WO2007081632A1

WO2007081632A1 - Optical apparatus with flipped compound prism structures

Info

Publication number: WO2007081632A1
Application number: PCT/US2006/061941
Authority: WO
Inventors: William J. Cassarly
Original assignee: Optical Research Associates; Avery Dennison Corporation
Priority date: 2006-01-13
Filing date: 2006-12-12
Publication date: 2007-07-19
Also published as: US20070035843A1; US7545569B2; WO2007081632B1

Abstract

An optical apparatus comprises a light source, an optical member and a spatial light modulator. The optical member comprises optically transmissive material and has a textured major surface receiving light from the light source. The textured surface comprises first and second pluralities of non-intersecting elongate features. The pluralities are angled with respect to each other by less than about 90° and intersect each other so as to form total internal reflection structures. The spatial light modulator has rows or columns of pixels for receiving light from the optical member at a major surface. The light source may be (i) a light guide, or (ii) a source of light providing, to the optical member, light having a peak luminance that is shifted from a normal direction to the textured major surface by more than about 30°.

Description

OPTiCALAPPARATUS WiTH FLIPPED COMPOUND PRiSM STRUCTURES

PRIORITY APPLlCATfON

[OOOIj This application claims priority to U.S. Provisional Patent Application No. 60/759.086 entitled "Light Recyding Structures with Multiple Arrays of Elongate Features" filed January 13, 2005, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION P002| This application relates generally to optical apparatus with optical control structures having multiple arrays of elongate structures. More particularly, the application relates to such optical apparatus wherein the optical control structures comprise light recycling structures or flipped compound prism structures- The present claims are directed to optical apparatus including flipped compound prism structures although light recycling structures may be included,

BACKGROUND

[0003J Conventional displays use optica! control structures (e.g., films) to maximize the luminance at the angles where viewers see the display. When the light source is efficiently coupled at large angles outside the desired view angles, optical control films can use the principle of total internal reflection to redirect the light into the desired view angle. Such optical control films may be included in displays that additionally comprise a light source and a transmissive spatfa! light modulator. The light source may be composed of an array of emitters, a light box. or a light emitter that is dispos&d at the edge of light guide. The spatial light modulator comprises Bn array of selectively activated pixels that can be used to form an image or pattern (e.g., text).

[0004J When using a Hght guide, light may be extracted from a front planar surface of the light guide by using an array of extractor elements, for example, on a back planar surface of the light guide, Extracting the light with high luminance at angles that are somewhat parallel to the front planar surface is often done more efficiently than extracting the light normal to that surface. This is often true when the light guide tapers between the edge close to the source and the edge far from the source,

EOOOδ] The conventional optical control film is disposed between the light source snύ the spatial light modulator. A plurality of rnicro-prisms in the film face towards the spafiai light modulator and are configured such that a portion of this light is redirected into a more desired range of angles using the principle of total interna! refiection.

[0006J One drawback of conventional optical control films having micro-prisms is that the films contribute to the formation of Moire patterns. Moire patterns are an interference effect resulting from the correlation of periodic structures. In this case, periodicity is introduced by the periodicity of the micro-prism film with the periodic pixels in the spatial light modulator. Additionally, Moire patterns can occur because of periodicities with the extractors used to couple the light out of the light guide.

[0007J What is needed, therefore, is a way to reduce or eliminate the contributions to Moire patterns,

SUMMARY

POOSJ One aspect of the invention provides an optical apparatus comprising a fight source, an optical member mά a spatial Sight modulator. The optical member comprises optically transmisslve material and has a iextureύ major surface receiving light from the light source. The textured surface comprises first and second pluralities of non-intersecting elongate features, The pluralities are angled with respect to each other by less than about 90^* anύ intersect each other so as to form total interna! refection structures. The spatial light modulator has rows or columns of pixels for receiving light from the optical member at a major surface. The light source may be (i) a light guide, or (H) a source of Sight providing, to the optica! member, light having a peak luminance that is shifted from a norma! direction to the textured major surface by more than about 30°

[0009| The opticai transmissive material, referred to herein as a flipped compound prism structure, fiim or sheet, reduces Moire patterns in a spafiai light modulator. This results from the above-mentioned angling of the pluralities of elongate features. The resulting textured surface provides multiple views into the light source (e.g., light guide) for each of many pixels of the spatial light modulator. This results in a reduction in Moire patterns by reducing correlation with artifacts in the light source such as a pattern of light extractors in a light guide.

£00010} A further aspect of the invention concerns undulating the mentioned, elongated features. Such undulating further reduces IVSoire patterns by reducing the periodicity of the textured surface.

[00011 J A yet further aspect of the invention concerns the use of the mentioned elongated features comprising prisms (as defined herein) with different pitches. The use of different pitches reduces Moire patterns by allowing the rotation of residual textured surface patterns without having to rotate the elongated features.

BRIEF DESCRIPTION OF THE DRAWINGS

[00012} The patent or application file contains at least one drawing executed in CQiOf. Copies of this patent or patent application publication with the color drawsng(s) wl be provided by the Office upon request and payment of the necessary fee. [00013j Example embodiments of optical apparatus and optical control structures such as light recycling structures or flipped compound prism structures are illustrated in the accompanying drawings, which are for illustrative purposes only, and in which like reference numerals refer to like parts.

[00014J Figure 1A is a cross-sectional view schematically illustrating selected components of an example display that includes a light recycling film.

[00015J Figure 1B is similar to Figure 1A but shows a display including a flipped compound prism film rather than a light recycling film_*

[00016] Figure 1C is similar to Figure 1 A but shows a display including both a light recycling film and a flipped compound prism film. [0001 ?} Figure 2A is a top surface view (parallel to the xy plane) of an example embodiment of a light recycling film comprising a plurality of total internal reflection structures.

[000183 Figure 2B is a cross-sectional view (parallel to yz plane) of the light recycling film of Figure 2A. [00019] Figure 2C is a plot of the intensity of the light transmitted by the light recycling film of Figure 2A,

£000203 Figure 3A is a top surface view (parallel to xy plane) of a modified light recycling film comprising an array of paraliei ridges and grooves that are rotated with respect to the x axis by an angle α

£000213 Figure 3B is a top surface view (paraϋel to xy plane) of a modified fight recycling film having an array of paraiiel ridges and grooves that are rotated with respect to the x axis by an angle α'.

100022] Figure 3C is a top surface view (paraliei to xy plane) of & composite light recycling film formed by combining the pattern of paraliei grooves rotated by an angle α (Figure 3A) with the pattern of paraiiel grooves rotated by an angle α' (Figure 38) to form a plurality of pyramid-shaped total Infernal reflection structures,

[000233 Figure 3D is a contour plot illustrating the surface profile of the composite light recycling film illustrated in Figure 3C. [00024] Figure 3E is a piof of the intensity of the light transmitted by the composite light recycling film of Figure 3C.

[00025J Figure 3F Is a plot of the gain as a function of the half angle |{α - α⁽) for the composite light recyciing film of Figure 3C.

£000263 Figure 3G is a top surface view {parallel to xy plane) of a modified light recycling film having aiternating deep grooves and shaliow grooves that are rotated with respect to the x axis by an angle α'.

[000271 Figure 3H is a cross-sectionai view (paraiiel to yz plane) of the modified light recycling film of Figure 3G.

[000283 Figure 3I is a perspective view of a modified light recycling fiim of Figure 3G.

£000293 Figure 3J is a top surface view (paraliei to xy piane) of a modified light recycling film having aiternating deep and shallow grooves that are rotated with respect to the x axis by an angle α

£00030] Figure 3K is a cross-sectional view (parallel to ys piane) of the modified light recycling film of Figure BJ. Figure 3L is a perspective view of a modified light recycling film of Figure 3J.

{000323 Figure 3M is a top surface view (parallel to xy plane) of a composite light recycling RIm formed by combining the set of parallel grooves having alternating depths and rotated by an angle a (Figure 3J) with the set of grooves having alternating depths and rotated by an angle α' {Figure 3G).

[00033] Figure 3N is a perspective view of the composite light recycling film of Figure 3M.

[00034] Figure 30 is a perspective view of a composite light recycling film formed by combining a pattern of parallel cylindrical elongate features (e.g., cylindrical grooves) rotated by an angle a with a pattern of parallel cylindrical elongate features rotated by an angle o',

[GGQ35J Figure 3P is a piot of the intensify of the light transmitted by the composite light recycling film of Figure 30.

Figure 3Q is a histogram of luminous intensity for the intensity piot of Figure ZP.

[GG037] Figure 3R is a perspective view of the composite light recycling film of Figure 3C comprising a plurality of pyramid-shaped prism structures and referred to herein as an upright (or "everted") configuration.

Figure 3S is a perspective view of an inverted composite light recycling film comprising a set of parallel ridges rotated by an angle α and a set of parallel ridges rotated by an angle α' that form inverted pyramid-shaped structures.

[000393 Figure 31 is a plot of the gain of an example light recycling film as a function of the shape of elongate features that comprise the light recycling film, as defined by a base angle v.

[00040] Figure 3U is a plot of the gain of an example iight recycling film as a function of film thickness L

[000411 Figure 3V schematically illustrates an example composite light recycling film formed by combining a first array of parallel grooves that have a pitch of 31 μm and that are inclined by an angle +5° with a second array of parallel grooves that have a pitch of 41 μm and that are inclined by an angle -5'. Figure 3W schematically illustrates a micro-prism having planar faces that form an apex that is a line rather than a point.

[000433 Figures 3X, 3Y_< and ZZ schematically illustrates a composite light recycling films having pitches that vary. [000443 Figure 4A is a top surface view (parallel to xy plane) of a modified light recycling film having an array of parallel ridges and grooves that are rotated with respect to the x axis by an angle α.

E00045] Figure 48 is a top surface view (parallel to xy plane) of a modified light recycling film having m array of parallel ridges and grooves that are rotated with respect to the x axis by an angle α'.

1000463 Figure 4C is a top surface view (parallel to xy plane) of an example embodiment of a light recycling film having ridges &nά grooves parallel to the x-axis.

[QQ047J Figure 4D is a top surface view {parallel to xy plane) of a composite light recycling film formed by combining the pattern of parallel grooves rotated by an angle α (Figure 4A) with the pattern of parallel grooves rotated by an angle α' (Figure 4S) and the pattern of parallel grooves that is parallel to the x axis (Figure 4C).

JΩ0G4SJ Figure 4E is a contour plot illustrating the surface profite of the composite light recycling film illustrated in Figure 4D.

[00049J Figure 4F is a plot of the intensity of the iight transmitted by the composite light recycling film of Figure 4D.

[OOOSOj Figure 4Q is a plot of the gain as a function of the half angle ?(α ~ εt') for the composite light recycling films of Figures 3C and AD,

[000513 Figure 4H is a histogram of luminous intensity for the intensity plot of Figure 4Ψ.

Figure 41 is a perspective view of the composite light recycling film of Figure 4D, which has sn upright ("everted") configuration comprising a plurality of parallel grooves that form upright total internal reflection structures,

[000533 Figure 4J is a perspective view of an inverted composite light recycling film formed by combining a pattern of parallel ridges rotated by an angle a with a pattern of parallel ridges rotated by an angle α' and a pattern of parailei ridges that is parallel to the x axis.

£000643 Figure 41 schematically iiiustrates a composite light recycling films comprising a plurality of sets of parallel elongate features that do not intersect each other at a single common point.

[GG95SJ Figure 5A is a top surface view (paraiiei to xy plane) of a modified fight recycling fiim having an array of paraiie? ridges and grooves that are angled with respect to the x axis by an angle α

[00058J Figure 58 is a top surface view (paraiϊeS to xy piane) of a modified light recycling film having an array of parallel ridges and grooves that are angled with respect to the x axis by an angle α'.

C000S73 Figure 5C is a top surface view {parailei to xy plane) of a modified light recycling film haying an array of paraiiei ridges and grooves that are angled with respect to the x axis by an angle ξ. [00058] Figure 6D is a top surface view (parallel to xy plane) of a composite light recycling film formed by combining the pattern of paraiiei grooves rotated by an angle α {Figure SA) with the pattern of parailei grooves rotated by an angle α' (Figure 5B) anά the pattern of paraiiei grooves rotated by an angle ξ (Figure 5C),

[øøøSδJ Figure 6A is a top surface view (paraϋeS to xy piane) of a modified light recycling film having an array of parallel ridges and grooves that are angled with respect to the x axis by an angle α,

£000603 Figure 68 is a top surface view (parallel to xy plarte) of a modified light recycling fiim having an array of paraiiei ridges and grooves that are angled with respect to the x axis by m angle α'. [00061J Figure 6C is a top surface view (parailei to xy plane) of a modified light recycling fiim having an array of parallel ridges and grooves that are angied with respect to the x axis by an angle ξ.

[00062J Figure <3D is a top surface view (parallel to xy plane) of a modified light recycling film, having an array of parallel ridges and grooves that are angled with respect to the x axis by an angle ξ\ [00063] Figure QE is a top surface view (parallel to xy plane) of a composite light recyciing film formed by combining the pattern of parallel ridges and grooves rotated by an angle α (Figure 6A) with the pattern of paraliei grooves rotated by an angle α' (Figure 8B)₁ the pattern of parailei grooves rotated by an angle ξ (Figure 6C)₁ and the pattern of parallel grooves rotated by an angle ξ' (Figure 8D).

[00064J Figure 6F is a plot of the intensity of the light transmitted by the composite light recycling film of Figure δE,

JOOO603 Figure 7 A is a plot of the gain as a function of the relative depth Δz of the grooves parallel to the x axis as compared to grooves rotated by the angle α and the grooves rotated by the angle a\

[000663 Figure 7S is a top surface view (parailei to xy plane) of a composite light recyciing film formed by combining the pattern of parallel grooves rotated by ati angle α with the pattern of paraSiel grooves rotated by an angle α'.

[DG0δ7j Figure 7C is a top surface view (parailei to xy plane) of a composite light recyciing film wherein a third set of grooves is added to the pattern of Figure 7B; the third set of grooves are parallel to the x axis and have the same depth as the grooves of Figure 7S, but are more closely spaced than the grooves of Figure 78.

£00068] Figure 7D is a top surface view (parailei to xy piane) of a composite light recyciing film corresponding to data point 7D in Figure 7A, wherein the grooves parallel to the x axis are deeper than the grooves rotated by the angle α and the grooves rotated by the angle oΛ

[00069] Figure 7E is a top surface view (parallel to xy plane) of a composite light recycling film corresponding to data point 7E in Figure 7A, wherein the grooves parallel io the x axis are deeper than the grooves rotated by the angle α and the grooves rotated by the angle α',

[00070J Figure 7F is a top surface view (parallel to xy piane) of a light recycling film wherein the grooves parailei to the x axis are cut sufficiently deep to remove the grooves created by the grooves rotated by the angle α and the grooves rotated fay the angle α¹. [00071] Figure 8A is a cross-sectional view (parallel to yz plane) of a portion of the composite light recycling film similar to that illustrated in Figure 4D₁ inciting back ray traces of light propagated through the film.

[00072] Figure 8B is a cross-sectional view (parallel to yz plane) of a portion of the composite light recycling film similar to that illustrated in Figure 4D_> including forward ray traces of Sight reflected by the film.

[00073] Figure SC is a cross-sectional view (paraiiei to yz piane) of a portion of the composite light recycling film similar to that iiiustrated in Figure 4D, including back ray traces of light reflected by the film. [000743 Figure 8D is a cross-sectional view (paraiiei to yz piane} of a portion of the light recycling film of Figure 4D, including back ray traces of light originating from a selected portion of a pixei of the spatial iight moduiator.

[00075] Figure 9A is a cross-sectional view (paraiiei to yz plane) of the backlii display showing the back ray traces of Figure 8D; the display includes (from left to right) a planar reflector, a iight guide, a diffuser, and a iight recycling film.

[00076] Figure 9B is a top surface view {parallel to xy plane) of &n example light recycling film, showing the relative dimensions of the pattern of paraiiei ridges anά grooves and a selected pixei of the spatial iight modulator.

[00077] Figure 9C is a plot of the illuminance of the light projected onto the rear surface of the iight guide by the collimated light rays illustrated in Figure 9A.

[00078J Figure 9D is a plot of the illuminance of light projected onto the rear surface of the light guide by the collimated iight rays illustrated in Figure 9A when a 3° diffuser is included in the backlit display.

[00079] Figure 9E is a piot of the illuminance of iight projected onto the rear surface of the light guide by the coliimated light rays iiiustrated in Figure 9A when 10° diffuser is included in the backiit display.

[000803 Figure 10A is an example array of extraction elements formed on a rear surface of the iight guide included in the display.

[00081J Figure 108 is a projection of the illuminated spatial regions of Figure 98 onto the array of extraction elements of Figure 10A, wherein the projection results in an under-illuminated pixel. Figure 10C is a projection of the illuminated spatial regions of Figure 9B onto a translated array of extraction elements, wherein the projection results in an over- iilυminated pixel.

[00083} Figure 11 A illustrates the projection of a selected! pixel onto the composite light recycling film of Figure 3C.

[00084] Figure 118 is a plot of the illuminance of light projected onto the rear surface of the light guide when the coiiimated light rays such as illustrated in Figure SA are transmitted through the composite light recycling film of Figure 3C.

[00086] Figure 12A iltustrates the projection of a selected pixel onto the composite light recycling film of Figure 4D.

[000863 Figure 12B is a piot of the illuminance of light projected onto the rear surface of the light guide when the coiiimaied light rays such as illustrated in Figure 9A are transmitted through the composite light recycling film of Figure 4 D.

[00087J Figure 12C illustrates the projection of a selected pixel onto a composite light recycling film wherein the relative depth Δz of the grooves parallel to the x axis relative to the grooves rotated at an angle α and the groove rotated at an angle α' are +0O05.

[00088J Figure 12D is a plot of the intensity of light projected onto the rear surface of the light guide when the collimated light rays such as illustrated in Figure 9A are transmitted through the composite light recycling film of Figure 12C.

[0008Sj Figure 13A illustrates the projection of a selected pixel onto two crossed light recycling films like the light recycling film of Figure 2A.

[OOO9O3 Figure 13B is a plot of the intensity of light projected onto the rear surface of the light guide when the collimated light rays such as illustrated in Figure 9A are transmitted through the crossed light recycling films of Figure 13A.

[00091] Figure 14A illustrates the projection of a selected pixel onto two crossed light recycling films IiKe the composite light recycling film of Figure 3C.

[0G092J Figure 14B is a plot of the intensity of light projected onto the rear surface of the light guide when the coilimaied light rays such as illustrated in Figure 9A are transmitted through the crossed light recycling films of Figure 14A. [00093] Figure 15A illustrates the projection of a selected pixei onto a two crossed light recycling films tike the composite light recycling film of Figure 4D,

E0OOS4J Figure 15B is a plot of the intensity of light projected onto the rear surface of the fight guide when the eøliimated Sight rays such as illustrated in Figure 9A are transmitted through the crossed light recycling films of Figure 15A.

[00095] Figure 1SC illustrates the projection of a selected pixei onto two crossed light recycling fiims like the composite light recycling fiim of Figure 12C

[00096J Figure 15D is a plot of the intensity of light projected onto the rear surface of the ilght guide when the collimated light rays such as iilusfrated in Figure 9A are transmitted through the crossed light recycling films of Figure 1βC.

£000973 Figure 18A iiiustrates the projection of a seiected pixel onto two crossed light recyciing films like the composite iight recycling film of Figure 4D₁ wherein the pixei and the films are rotated with respect to each other.

£000983 Figure 16B is a plot of the intensity of iight projected onto the rear surface of the iight guide when the collimated light rays such as illustrated in Figure 9A are transmitted through the crossed light recyciing films of Figure 16A,

£00099] Figure 16C is a plot of the intensity of light projected onto the rear surface of the light guide when the collimated iight rays such as illustrated in Figure 9A are transmitted through a diffuser and the crossed iight recyciing fiims of Figure 16A< [000100] Figure 1? is a schematic illustration of selected components of a coior backlit display that includes multiple light recycling films.

[000101] Figure 18 is a perspective view of selected components of a coior backJit display that includes a compound paraboϊic coliector configured to couple light from a light source into a light recyciing film £0001023 Figure 19A is a schematic illustration of the light recyciing film of Figure 2A positioned over the modified light recycling film of Figure 3A, which is positioned over the modified iight recycling film of Figure 3B.

£0001033 Figure 1 QB is a plot of the intensity of the iight transmitted by the three sequentially-positioned light recycling fiims of Figure 19A, Figure 19C is a histogram of the luminous intensity for the spatial intensity plot of Figure 198,

[0001053 Figure 20 is an exploded view of selected components of an example embodiment of a lighting apparatus that includes a light emitter in a hollow light box, a diffuses; and a light recycling film.

1000106] Figure 21 is an exploded view of selected components of an example embodiment of a lighting apparatus comprising a plurality of light emitters disposed about a light guide, a diffuser, and a light recycling film.

[000107] Figure 22A is a top surface view (parallel to the xy plane) of an example embodiment of a light recycling film having a sinusoidal pattern.

[O0O1OS3 Figure 22B is a cross-sectional view (parallel to yz plane) of the light recycling film of Figure 22A.

[000109] Figure 22C is a plot of the illuminance of the light projected through two of the light recycling films of Figure 22A that have been crossed at a 90° angle, and onto the rear surface of the light guide.

[000110] Figure 22D is a plot of the illuminance of Sight projected through a 3° diffuser, through two of the light recycling films of Figure 22A that have been crossed at a 90° angle, and onto the rear surface of the light guide.

[000111J Figure 22E is a top surface view (parallel to the xy plane) of an example embodiment of a composite nonlinear light recycling film formed by combining ihe two orthogonal patterns of grooves similar to those included in the light recycling film in Figure 22A.

[000112] Figure 23A is a top surface view (in the xy plane) of a modified light recycling film having a plurality of linear elongate features (e.g., grooves or ridgeiines) with varying elevation, which are oriented with respect to the x axis by an angle α

[000113] Figure 23B is a top surface view (in the xy plane) of a modified light recycling film having a plurality of linear elongate features (e,g., grooves or ridgeiines) with varying elevation, which are oriented with respect to the x axis by an angle α'.

[000114} Figure 23C is a schematic illustration of in-phase extrema points on a modified light recycling film having variable-elevation elongate features. [000115] Figure 23D is a schematic illustration of 180^* out-of-phase exfrema points on a modified fight recycling film having variable-elevation elongate features.

[00011δ] Figure 23£ is a top surface view (parallel to xy plane) of a composite modified light recycling fiirn formed by combining the pattern of elongate features rotated by an angle α (Figure 23A) with the pattern of elongate features rotated by an angle α' (Figure 23B).

[000117] Figure 23F is a top surface view {in the xy plane) of a modified light recycling film having a pfuraiiiy of elongate feature with varying elevation, wherein the extrerπa points are 180° out of phase. [000118] Figure 23G is a perspective view of the modified light recycling film of Figure 23F, wherein the extrema points correspond to elevation minima in an inverted configuration.

[000119] Figure 23H is a perspective view of the modified light recycling film of Figure 23F, wherein the extrema points correspond to elevation maxima in an upright f everted") configuration.

[0001203 Figure 23! is a plot of the intensity of the light transmitted by the light recycling film of Figure 23F.

[000121] Figure 24 is a partial cross-sectional view of a light recycling films having elongate features with multiple faceted edges. [000122] Figures 26 A and 2SB are plots of luminance versus angle for respective optical apparatuses that are shown below the plots in simplified cross-sectionai views.

[000123] Figures 26A and 268 are upper perspective views of a fragmentary portion of the light guides shown m Figures 25A and 258.

[00Q124] Figure 27 shows, on the top, a fragmentary view of prisms of a flipped compound prism structure and, on the bottom, the foregoing view together with a fragmentary portion of a light guide,

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

[000125] Figure 1 illustrates selected components of an example backlit display 10a. The backlit display 10a has a substantially planar display surface 26 that is parallel to the xy plane, as defined in Figure 1, The backiit display 10a includes a light source 12, such as one or more fluorescent lamps, incandescent lamps, light emitting diodes, or laser diodes. In other embodiments, other types of light sources are used, or a combination of different types of light sources is used, in certain embodiments, the backiit display 10a includes a light source that is configured to generate multi-chromatic light (for example, white light), while in other embodiments the backiit display 10a includes a light source that is capable of generating substantially monochromatic light at one or more selected wavelengths. One example of such a multi-chromatic light source is art array of red, green and blue light emitting diodes (ar\ "RGB LED array"), in the example embodiment illustrated in Figure 1, the light source 12 is a linear light source positioned afong at least a portion of a selected edge of the backSit display 10a to provide edge lighting. Examples of other linear light sources include laser diodes or other Sight emitters arranged in a linear array or other light sources extended along a length substantially longer than their height, in other embodiments, the light source is a point source. Examples of point sources include a single LED or laser diode, a relatively small incandescent bulb, or other relatively small light emitters having similar height and width. In certain modified embodiments, the light source 12 is positioned along more than one edge of the backiit display. The light sources 12 may be positioned elsewhere. £000126] Still referring to Figure 1. the backiit display 10a further includes a planar, optically transmissive light guide 18 that is positioned substantially parallel to the display surface 26. The light guide 18 is configured to receive and propagate light from the light source 12, Depending on the type of light source used, an optional elongate concave reflector 14 is positioned on the opposite side of the light source 12 from the light guide 18. In such embodiments, the concave reflector 14 is used to increase the amount of light coupled from the light source 12 into the iight guide 18. Other systems for coupling light from the iight source 12 into the iight guide 18 are used in other embodiments. For example, in an embodiment wherein the light source 12 comprises an array of iight emitting diodes, light piping or a fiber optic coupling system can be used to couple iight from the light source 12 into the light guide 18. This configuration allows ϊh& iight source 12 to be positioned remotely with respect to me light guide 18. Other configurations are possible. [000127] in certain embodiments the light guide 18 comprises materia! that is substantially optically transmissive to the wavelengths of operation, for example, to one or more wavelengths output by the light source 12. The light guide 18 may comprise, for exarπpie, glass or plastic or other polymeric materia! in certain preferred embodiments. In various embodiments, the light guide 18 comprises material having a higher index of refraction that surrounding areas such that iight is guided within the light guide 18 via total internal reflection,

[000128] in particular, iight from the light source 12 is propagated in the iight guide 18 by total internal reflection. However, the iight guide 18 includes a plurality of extraction elements that allow light to be coupled out of the light guide 18. ϊn one embodiment, the extraction elements are formed on the surface of the light guide 18 that faces the planar display surface 26, while in other embodiments the extraction elements are formed on the surface of the iight guide 18 that is opposite the pianar dispiay surface 26. Regardless of their position with respect to the planar display surface 26, the extraction elements are configured to allow a portion of the iight propagating in the light guide 18 to be coupled from the light guide, and to be redirected toward the planar display surface 28, In one embodiment, the extraction elements provide a portion of the surface of the light guide 18 having an increased surface roughness. The extractor elements may comprise, for example, raised or recessed micro-structures such as protrusions or dimples and ridges or grooves, as weii as localized materia! differences or other surface or volume perturbations. The extractors may refract, reflect, diffract, and/or scatter light. The extractors may be arranged in any pattern. For example, the extraction elements may be provided with a spatially varying pattern to enhance spatial uniformity of the out-coupled iight, In a modified embodiment, the light guide 18 is replaced with a planar iight source capable of generating a substantially uniform light field. In an alternative embodiment, the light guide can b& replaced with sn electroluminescent light source.

£0G012δj| As illustrated in Figure 1, a rear reflector 16 is disposed rearward of the light guide 18. The rear reflector 16 may have a shape that matches the rear shape of the light guide 18, although other shapes are possible. This rear reflector 16 may comprise a reflective layer such a metal layer or a diffuse paint. Dielectric coatings or other reflective layers may also be used. Also as illustrated in Figure 1, a planar diffuser 20a is positioned over or forward of the iight guide 18, such that light coupled from the extraction elements passes through the planar diffuser 20a, The planar diffuser 20a is configured to diffuse light For example, the diffuser may comprise surface or volume features that symmetrically or asymmetrically scatter light passing therethrough. Such scattering may be substantially random from location to location across the diffuser 20a, This diffusing effect reduces or eliminates the appearance of the light extractors as seen by the viewer, and generally enhances the spatial uniformity of the iiiurnϊnation of the planar display surface 26. Periodic illumination patterns at the pianar display surface 28, such as possibly produced by the light extractors, may disadvantageous^ result in Moire patterns being created when the display surface 26 forms part of a pixilated display comprising an ordered array of pixeis. in one embodiment, the planar diffuser 208 is an optically iraπsmissive element having a surface feature variation capabϊe of randomly redirecting light in a wide range of angles, such as up to ±90° with respect to the incident angle. The planar diffuser 20a is optional, and is omitted from the backiit display 10a in certain embodiments.

[000131] A planar light recycling film (LRF) 22a_< is positioned over or forward of the light guide 18, The light recyciing film 22a has a textured surface 22b. Although shown schematically in Figure 1A as flat, textured major surface 22b has multiple arrays of elongate structures as will be described below. In embodiments wherein a diffuser 20a is used to scatter light coupled out of the fight guide 18, the iight recycling film 22a is generally positioned over or forward the diffuser 20a. The light recycling film 22a is rearward of the planar display surface 26 and controls the angular distribution of light from the iight guide 18 directed toward the planar display surface. In particular, the light recyciing film 22a is configured to transmit light into a substantially limited range of angles ±Q. The light recyciing film 22a permits oniy a relatively small amount of the light transmitted therethrough to be directed outside the range of angles ±θ. In general, the iight recycling film 22a is designed such that iight is back reflected toward the rear reflector 16 and into the iight guide 18 rather than be directed outside the range of angles ±Q, in one embodiment β is iess than about 60°, in another embodiment θ is less than about 45*. in another embodiment θ is less than about 30% and in another embodiment 8 is less than about 20°, in one embodiment θ is between about 10° and about 70^π, in another embodiment θ is between about 15° anύ about 50°, and in another embodiment θ is between about 20" and about 40^*. The angle θ is about 22° in some embodiments. This angle 8 may be less than 15" in some embodiments.

HO0O132J This configuration reduces losses associated with the light recycling film

22a. since the light not transmitted by the light recycling film 22a is "recycled" into the light guide 18, The light may be reflected by the rear reflector 16 and/or circulated with the light guide. The light may be deflected, for example, scattered, by one or more extractor elements. The light may be incident on the light recycling film 22a one or more times and is thereafter capable of being transmitted by the iight recycling fiim 22a. in certain modified embodiments, the backiit display 10a comprises more than one light recycling fiim.

[000133] in certain embodiments the light recycling fiim 22a comprises materia! that is substantially optically transmlssive to the wavelengths of operation, for example, to one or more wavelengths used for illumination, As described herein, the light recycling fiim 22a is configured to transmit a portion of the light incident thereon. For example, in one embodiment the iight recycling fiim 22a transmits between about 70% and about 50% of the light incident thereon from a Lambertϊan source, and reflects between about 30% and about 50% of the light from the LambertSon source incident thereon averaged over ail angles, In another embodiment the iight recycling film 22a transmits between about 65% and about 45% {for example, about 60%) of the iight incident thereon, and reflects between about 35% and about 55% (for example, about 40%) of the light incident thereon, These values of transmission and reflection assume no recycling and negligible absorption by the iight recycling film. The light recycling fiim 22a may comprise glass or plastic or other polymeric material in certain preferred embodiments, In one preferred embodiment, the iight recycling film 22a comprises polycarbonate such as homogeneous polycarbonate or PMlViA. Other materials, however, may be used.

[000134] Still referring to Figure 1, a planar spatial light modulator 24 is positioned forward of the iight guide 18 and light recycling film 22a to receive iight passed through the light recycling fiim 22a. In one embodiment, the spatial iight modulator 24 is a liquid crystal display, such as those commonly used in products such as flat panels displays, telephone displays, anά fiat screen video displays. Such a spatial light modulator may comprise a plurality of pixels that are selectively activated to form an image or pattern. such as a text or symbols, in some embodiments, the spatial iight moduiator comprises a non-emissive device and may be transmissive device. Reflective or transreflective devices may also be employed in different configurations. Other apparatuses capable of spatially modulating light are used in other embodiments. In various preferred embodiments, a portion of the spatial light modulator 24 forms the planar display surface 28. In certain embodiments, a layer or coating, such as. for example, one or more polarizing iayers or coatings, may be disposed on the planar display surface 26.

£0001383 Thus, the example backiif display 10a illustrated in Figure 1 is usable as a flat panel display screen. As described herein, the light recycling film efficiently increases the directionality of the display screen. The light recycling film may, for example, reduce or prevent light from exiting the dispiay screen at certain angles, such as at steep angles with respect to the normal through the display screen. The non- transmitted iight is "recycling" back into the system to be redirected and subsequently transmitted Bi an angle within the desired range. Accordingly, the dispfay is more efficient as light that would otherwise be directed at undesirable angles is redirected into the desired range of angles tfrereby enhancing the luminance in this anguiar range. Angles closer to norma? are often advantageous in certain type of dispiay devices. For example, in embodiments wherein the spatial iight modulator 24 comprises a liquid crystal dispiay, light passing through the display at angles closer to θ = 0^β provides improved dispiay color and contrast as compared to iight passing through the display &i larger angles.

[000136] This performance feature is advantageous because in many applications light exiting the display screen at steep angles is not usefui. unwanted, or both. For example, in a display screen used as a desktop computer display, iight exiting the dispiay screen at a steep vertical angle (that is, toward the floor or toward the ceiling) is usualiy not useful. Additionally, in a display screen used as a video display in an automated teller machine, light exiting the display screen at a steep horizontal angle {that is, toward the usefs right or ieft) presents a security risk by allowing unauthorized users to view the contents of the display. The iight recycling fdm may at least somewhat attenuate these off-axes rays. Additionally, by recycling the non-transmitted light back into the system, the iight recycling film ailσws a iess powerful light source to be used with the system without compromising the dispiay luminance. This feature is a

1β particularly important advantage for display screens that are battery-powered, such as laptop displays, mobile phone displays, and handheld computer displays.

J0001373 Figure 18 illustrates selected components of another example backlii display 10b, The display 10b includes an optical control structure comprising a flipped compound prism structure 22c {e.g., film or sheet) having a textured major surface 2Zd facing light guide 1S. As used herein, "prism" means a device having the optical properties substantially similar to those of a planar and straight-surfaced prism (e.g_(J Figure 22B), although prism surfaces may have other shapes, such as planar anύ non- straight {e.g., Figure 24), or rounded (e.g., Figure 30). Optional diffuser 20b is situated between the flipped compound prism structure 22c and the spatial light modulator 24. Preferably, diffuser 22b is combined with the flipped compound prism structure 22c. Compared with the diffuser mentioned in Qi et al., Journal of the SiD, 13/9 (2GGS), pp. 781-788, the combined diffuser 22b attains an even smaiier "diffuser angle"— a term mentioned the foregoing article — and hence provides a higher oπ-axis brightness with the spatial light modulator 24, ("On-axis" means herein normal to the spatial light modulator, etc.) A rear reflector 16 is shown below the light guide 18. A light source 12 and optional reflector 14 supply Sight to the iight guide 18,

[000138] Figure 1C illustrates selected components of a further example backfit display 10c. The display 10c includes a pair of optical control structures comprising a flipped compound prism structure 22c having a textured major surface 22d facing light guide 18 and a light recycling film 22a having a textured major surface 22b facing the spatial light modulator 24. Optional diffuser 20a is situated between the flipped compound prism structure 22c and light recycling film 22a. A rear reflector 16 is shown below the light guide 18, A light source 12 and optional reflector 14 supply light to the light guide 18.

£000139] in this description. Figures 2A-24 nominally concern light recycling structures {e.g., 22a. Figures 1A and Figure 1C), whereas Figures 25A-27 nominally concern flipped compound prism structures (e.g., 22c, Figure 1B). However, as the following shows, many details of light recycling structures are interchangeable with detaiis of flipped compound prism structures. For the present purposes, it is sufficient to note key contrasts and a key similarity between light recycling structures and flipped compound prism structures. Regarding contrasts, the textured surface 22b of light recycling structure 22a {Figures 1A and 1C) face upwardly, towards the spatial light modular 24, whereas the textured surface 22d of flipped compound prism structure 22c faces downwardly, away from the spatial light modulator 24, Additionally, the diffuser 20a is of Figures 1A and 1C is positioned beneath the light recycling structure 22a, whereas in Figure 18, the diffuser 20b ts positioned above Xbβ flipped compound prism δ structure 22c. Regarding similarity, the construction of the flipped compound prism structure 22c (Figure 18} may be the same as for the light recycling structure 22a (Figures 1A and 1C). Thus, although the present application is directed to optical apparatus including flipped compound prism structures, at least the construction details of the fight recycling structure 22A {Figures 1A and Figure 1C) are relevant to the 0 flipped compound prism structures of Figure 1 B.

[000140] Referring back to Figure 1A, as described herein, the light recycling fiim 22 is configured to transmit light within a certain range of angles ±θ from a normal through the light recycling film (that is parallel to the z axis). Figure 2A schematically illustrates a top surface view (parallel to xy plane) of an example light recycling film δ 22a, &nύ Figure 28 schematically illustrates a cross-sectional view (parallel to yz plane) of the film illustrated in Figure 2A. Figures 2A and 28 show that the light recycling fiim 22a includes an array of elongate prisms 100₍ also referred to as "micro-prisms" or more generally "micro-structures", that are formed on a film body portion 102. These structures may be more generally referred to as total internal reflection (TiR) structures, 0 As illustrated in Figure 2B₅ the film body portion 102 has a first surface 104 in which the prisms 100 are formed, and a second surface 106 that is substantially planar, and that is opposite the first surface 104. The array of elongate prisms 100 forms a periodic structure of alternating parallel ridges 108 and grooves 110> Each period of the array includes two facets 105, or faces, from which light can be reflected. Figure 2A is a top 6 surface view of the light recycling fiim 22a illustrated in Figure 2B, showing the ridges 10S and the grooves 110.

(000141J in an example embodiment the elongate prisms 100 have an apex angle φ, the full included angle, that is typically about 90^*, but that ranges from about 70° to about 120* in one embodiment, and from about 80° to about 100° in another 0 embodiment. Values outside these ranges are also possible. The ridges 108 need not be symmetrical. Similarly the grooves 110 med not be symmetrical. The apex angle φ for adjacent prisms 100 also need not be identical. The height and periodicity may also vary. in yet another modified embodiment, the elongate prisms 100 are provided with curved surfaces instead of sharp angles, such that the cross-section illustrated in Figure 2B has the shape of a smooth oscillating waveform instead of a jagged triangle waveform. The elongate prisms 100 may also be bϊunted on top. For example, instead of ridges 108 with sharply pointed apexes, a substantially flat portion may be disposed at the top of the ridge. Such a Hat portion may assist in contacting the light recycling fiim 22a with another film or other structure disposed thereon. The elongate prisms 100 in the iight recycling film 22a are formed using one or mors of a wide variety of fabrication techniques including, for example molding or embossing techniques for fabricating sheets and diamond turning techniques for fabricating fools.

E00O143] The Sight recycling film 22a may be oriented such that the elongate prisms 100 are facing toward the pianar display surface 26. However, In modified embodiments the Sight recycling film 22a is oriented differently, for example, such that the elongate prisms 100 face away from the planar display surface 26, and toward the iight guide 18.

$5001443 As described herein, when the light recycling film 22a illustrated in Figures 2A and 28 is placed in the backiit dispiay 10a light distributed in a range of angles, for example, Lambertian, is incident thereon. The iight recycling film 22a transmits a portion of the light that will exit the light recycling fiim 22a in a certain range of angles ±8. The fight recycling fiim 22a reflects light that wouid otherwise not exit the light recycling film in ihe range of angles ±β. The result is a modified, for example, narrower and more concentrated angular distribution for iight transmitted through the iight recycling film 22a relative to the angular distribution of iight incident on the light recycling film. Figure 2C is a plot of intensity versus angle in the vertical and horizontal directions {parallel to the x and y axes, respectively) of the transmitted light distribution for the light recycling film 22a illustrated in Figures 2A and 2B. In this plot, light with higher intensity is indicated by lighter shading, and iight with lower intensity is indicated by darker shading. Figure 2C shows that the iight recycling film 22a illustrated in Figures 2A and 28 concentrates the transmitted light in a central lobe, and reduces or substantially eliminates ih^ transmission of light at wider angles.

[000146] in the light recycling film 22a illustrated in Figures 2A and 2B, the ridges 108 and grooves 110 are substantially parallel to the x axis, in modified embodiments of a iight recycling film, the array of parallel ridges 108 and grooves 110 is rotated with respect to the x axis. For example, Figure 3A schematically illustrates a modified light recycling film 112 wherein the ridges 108 and the grooves 110 are rotated with respect to the x axis by an angie α. where α > 0, Similarly, Figure 3B schematically illustrates a modified light recycling film 114 wherein the ridges 108 and the grooves 110 are δ rotated with respect to the x axis by an angle α'. where α' < 0. in another embodiment the angles α and | α'| are less than about 30*. in another embodiment the angles α and |α'| are less than about 20°, and in another embodiment the angles α and | α'j are less than about 10*. In one embodiment the angles α and | α'j are between about 5' and about 30°_: in another embodiment the angles α and | α'J are between about 0 7.5° and about 27.5^*, and in another embodiment the angles α and j α'j are between about 10° and about 25°. White in certain embodiments α - \

, in other embodiments εt ≠ j α' j . Likewise, while in certain embodiments α > 0 and o! < 0, in other embodiments σ > 0 and α' > Q. and in yet other embodiments cs < 0 and α* < 0.

|ø00146j| ^{iri an} example embodiment, the patterns of grooves 110 used to form the 5 modified light recycling films 112, 114 illustrated in Figures 3A and 38 are combined to form a composite light recycling film, Figure 3C schematically illustrates a two-arrøy composite light recycling film 116 formed by combining the pattern of parallel grooves 110 rotated by an angle α (Figure 3A) with the pattern of parallel grooves rotated by an angle α' (Figure 3B), in Figure 3C, line 112' is parallel to the array of grooves 110 0 corresponding to modified tight recycling Sim 112, and tine 114' is parallel to the array of grooves corresponding to the modified light recycling film 114. Figure 3D is a contour plot illustrating the surface profile of the composite light recycling film 114 illustrated in Figure 3C. The first and second sets of grooves form pyramid shaped prism structures or total interna! reflection structures. These pyramid shapes prism S structures may have rounded or pointed/sharp edges or corners. In the example embodiment illustrated in Figure 3D, the distance between grooves 110 Es approximately 0.05 mm (in XhB y dimension), (n other embodiments, the separation of grooves 110 are between approximately 0.02 mm wide and approximately 0.10 mm wide, in embodiments wherein the apex angϊe φ is 90*, the groove 110 have a depth 0 (in the z dimension) that is approximately half the groove width. In certain embodiments, the distance between the grooves and ridges is smaller than a pixel size in the spatial light modulator. Other dimensions are used in other embodiments. These grooves 100 may more generally be referred to as elongate features or in this particular example, substantially parallel linear features. In this embodiment, two sets of paraiiel linear features are used to form the total internal reflection structures. Note in this embodiment a given groove in the first set intersects another groove in the second set only once. [000147J When light distributed in a range of angles, for example, Lømbertian, is incident on the composite light recycling film 116 illustrated in Figure 30, the resulting angular distribution of transmitted Sight is shown in the light intensity plot of Figure 3E. The luminance of the light transmitted in the central iobe depends at least partially on the half angle |{α - α') between the modified light recycling fiims 112, 114. Figure 3F is a plot of the gain, or luminance enhancement measured on axis, for the composite light recycling film 118 illustrated in Figure 3C as a function of the half angle |{α - α') between the angled light recycling film patterns 112, 114. As illustrated In Figure 3F, the gain can be increased by reducing the half angle |{α - α'} to iess than approximately 30^* or increasing the haif angie above approximately 30°. The plot shown in Figure 3F₁ however, is a plot of data points from specific Monte Carlo simulations and. thus, includes some noise.

[000148J Figures 3A and 3B illustrate modified light recycling films 112, 114 having arrays of ridges and grooves rotated by angles α anά α' with respect to the x axis., respectively, in such embodiments, th& array features that define each light recycling fiim (for example, the ridges and grooves) are of eqυai dimension throughout each film, in contrast, in certain modified embodiments, the array features that define a light recycling film BTB not constant throughout the fiim. For example, Figure 3G schematically illustrates a modified Sight recycling film 114a wherein the array features are rotated with respect to the x axis by an angle «', where «' < 0. However, as iϊiustraied in the cross-sectiona! view provided in Figure 3H, the modified iight recycling film 114a comprises alternating deep grooves 108a and shallow groove 108b. Figure 3S provides a perspective view of the modified iight recycling film 114a illustrated in Figures 3G and SH, Likewise, Figure 3J schematically iusfrates a modified light recycling film 112a wherein the array features are rotated with respect to ihe x axis by an angle α, where α > 0, However, as illustrated in the cross-sectional view provided in Figure 3K, the modified Sight recycling film 112a comprises alternating deep grooves 108a and shallow grooves 108b. Figure 3L provides a perspective view of the modified light recycling fiim 112a iiiuslraied in Figures 3 J and 3K. Figure 3M schematically illustrates a two-array composite light recycling film 116a formed by combining the pattern of parallel deep and shallow grooves rotated by an angle α {Figure 31) with the pattern of parallel deep mό shallow ridges rotated by an angle α' (Figure 3!}. Figure 3N provides a perspective view of the modified light recycling film 116a illustrated in Figure 3M. The composite light recycling fiim 118a is described here as being formed by the two modified light recycling films 112a &nά 114a. However, the composite light recycling film 11Sa is alternatively described as being formed by four modified Sight recycling arrays A₁ B, C, D, each having an array of parallel grooves. Under this framework, arrays A and B are rotated by an angle α with respect to the x axis, arrays C and D are rotated by an angle α' with respect to the x axis, arrays A and C have elongate features with a first dimension, and arrays B mά D have elongate features with a second dimension.

[00016GJ in yet another modified embodiment, the array of total interna! reflection structures that define the light recycling film have curved surfaces, instead of the planar facets defining prismatic elements as illustrated in Figure 2A, For example, Figure 30 is a perspective view of a composite fight recycling film 150 formed by combining a pattern of parallel cylindrical elongate features having curved sides, for example, grooves in the shape of 140^* arc circular cylinders, rotated by an angle α with a pattern of parallel cylindrical elongate features rotated by an angle ct'. As illustrated in Figure 30, an array of total internal reflection structures having curved shapes are produced. As shown, the composite light recycling film 150 has a cross-section that includes a plurality of 140° circular arcs 152. in modified embodiments, the diameter of the cylindrical elongate features used to form the composite light recycling film 150 ar^ tuned to produce an angular light distribution pattern having certain properties. For example, Figure 3P illustrates an example angular light distribution pattern produced using the composite light recycling film 150 illustrated in Figure 3O. Figure 3Q is a histogram of the relative luminous intensity (measured in candeia) for the intensity plot of Figure 30. In other embodiments, more than or fewer than two sets of parallel cylindrical elongate features can be combined to form a composite light recycling film. However, the number of sets thai are combined to form the composite light recycling film may effect the resulting gain of the composite fight recycling film. For example, in an embodiment wherein light is passed through a light recycling film comprising one set of parallel grooves compromising fight circular cylinders, the gain is approximately 1.22, white in an embodiment wherein light is passed through a composite iight recycling film comprising two sets of parallel grooves comprising right circular cylinders, the gain is approximately 1 ,33. Advantageously, the crossed cylinder iight recycling film provides a smooth transition between the central region of high gain and the outer regions of low gain.

[G0G151J in certain embodiments, the composite light recycling films disclosed herein comprises a plurality of total interna! reflection structures having an upright ("everted") configuration, while in other embodiments an inverted configuration is used. Figure 3R is a perspective view of the composite light recycling film 116 illustrated in Figure 3C. which has upright ("everted") total internal reflection structures, in this case upright pyramid shape prisms, in the upright ("everted") configuration, a viewer looking down one of the grooves 110 sees a iine of constant eievation across the light recycling film, and there am no ridgelines of constant elevation in the light recycling film, (n contrast to the upright ("everted") configuration, Figure 3S is a perspective view of a composite tight recycling film 116' comprising a plurality of inverted total internal reflection structures. In the inverted configuration, a viewer looking down one of the ridges 108 sees a iine of constant eievation across the light recycling film, and fliere are no grooves of constant eievation in the iight recycling film. While both the upright ("everted") and inverted configurations are usable w^'rth the systems disclosed herein, the inverted configuration provides a stiffer structure for a given weight volume, or thickness of plastic. Additionally the inverted configuration may have reduced potential to trap long, thin contaminants and, thus, may be less susceptible to damage. Additionally, the inverted configuration facilitates reduced contact with neighboring surfaces by allowing the introduction of small variations in the height of the ridges 108. For examρie> a given ridge may vary in height along its length or different ridges can have different heights as discussed more fully below. In some embodiments, these height variations may be smail compared to the height of the ridge. Other advantages may also result.

[000152J Referring again to the example iight recycling film 22a illustrated in Figure 2B, the two facets 10S form acute base angles V₁ and v₂ with respect to the xy plane, such that vi + V₂ + φ « 180*. Figure 3T is a plot of the gain of an example light recycling film as a function of v, wherein v - V_t - v_s. In particular. Figure 3T illustrates the gain for the light recycling film 22a illustrated in Figure 2A (wherein the half angle Ifα - ctl = 0°), as weiϊ as for the composite light recycling film 116 illustrated in Figure 3C (wherein the half angle |[α ~ tf] « 5° and I[α ~ α] « 10°), Jn the illustrated embodiment, to increase or maximize the gain of the light recycling film, v may be between about 44°and about 44.5°, and is more preferably about 44.25°. [000163] The on-axis luminance enhancement of light passing through the light recycling film 22a, also referred to herein as the gain, depends on, among other things, the thickness t of the light recycling film 22a, as illustrated in Figure 28. Specifically, reflections from the inner planar surface 103 of the light recycling fiim 22a, and optionally from other planar surfaces of optical components included in the backllt display 10a, can cause reduced transmission and create interference patterns that aiter the gain of the system by up to approximately ±2%. Such interference patterns can create or amplify Moire patterns evident in the planar display surface 26. Therefore, in certain embodiments the thickness t of the light recycling fiim 22a is tuned to reduce or minimize these effects. [008154J Certain embodiments of a composite Sight recycling film 116< such as that illustrated in Figure 3C_S advantageously reduce the dependency of on-axis gain on thickness. For example, Figure 3U Is a plot of the gain of an example light recycling fiim as a function of film thickness t where the index of refraction of the film is 1485 As illustrated, both the gain and the variance in gain depend on the haif angle ₂(0 ~ α') of the composite tight recycling film 116. in Figure 3U, the gain variance is highest for |[α - a¹] ~ ⁰^- Figure 3ϋ also illustrates that for certain fiim thicknesses t, a composite fight recycling film 116 has a higher gain than a single array light recycling film 22a {wherein the half angle i[α~ Q¹I = O⁰).

[000155] Figure 3U also illustrates that in certain embodiments there exist gain maxima and minima for certain film thicknesses. Referring again to Figure 28, a coliimated light beam 109 is illustrated as being refracted and reflected by the light recycling film 22a. From Snelfs Law mά the geometry illustrated In Figure 28,

and

where β is the angie at which the coilimated light beam propagating normally into the Sight recycling film is refracted upon entering the light recycling film, v is the base angie formed between the facet 105 and the pϊane of the Sight recycling fiim (parallel to the xy plane), n is the index of refraction of the materia! comprising the light recycling film 22a, t is the thickness of the body portion of the film, and Δt is the thickness of the ridge 108. Thus, the quantity tan(β) is independent of film thickness. As illustrated in Figure 28, p is the pitch of the array of ridges 108. Gain maxima occur where the ratio wφ is an integer, and gain minima occur where the ratio w/p is m integer + Q.S, Accordingly, the thickness can be selected for a given pitch to provide increased gain, in certain embodiments the thickness is varied across the film to reduce interference effects. In some cases, this thickness may undulate across the fiim. Also as described herein, the height of the elongate features, e.g., ridges, can vary from ridge to ridge or along a given ridge.

£000157} in the example above, a singie pitch is shown. The composite light recycling fiim 116 illustrated in Figure 3C. for example, is formed by combining the array of parallel grooves 110 inclined by an angle α (Figure 3A) with the array of parailei grooves inclined by an angle α' (Figure 3B). In this example, the light recycling films illustrated in Figure 3A and Figure 38 have equal pitches, as measured along the y axis. The resulting composite Sight recycling film 116 illustrated in Figure 3C includes a plurality of pyramid centers 107 that are positioned in an array that is paraiiel to the x and y axes, fn a modified embodiment, a composite light recycling film is formed using subcomponent Hght recycling films with different pitches.

Ϊ000168J For example, Figure 3V schematically illustrates a composite fight recycling film 190 formed by combining a first array of parailei grooves that have a pitch of 31 pm and that are inclined by an angle α ~ +5° with a second array of parailei grooves that have a pitch of 41 μm and that are inclined by an angie α ~ -5°. In other embodiments, the pitches may be 40 and 50 microns respectively. Other values of pitches may be used as weil

[0001 S93 The composite light recycling film 190 includes a plurality of pyramid centers 192 that are positioned in an array that is rotated with respect to the x axis by an angle ζ. The pattern has a rotated appearance without rotating the film and without rotating the gain distribution. Gain is also not reduced. In certain configurations, this effect is used to reduce correlation with a pattern of extractor elements used to extract light from the iight recycling film or pixels In the spatiai light modulator. Thus_< by varying the pitch of the two patterns of parallel ridges and grooves that comprise the composite light recycling film, the patterns can be crossed at a smaiier half angie §(α - a') without the increase in pixel correlation that might occur when the half angie |(α - α') is reduced.

[0001603 in addition, the prisms formed are asymmetric The prisms may also comprise sides that come together at an apex that is a line 193 rather than a point as shown in Figure 3VV.

[000181 J in modified embodiments, the pitch of a pattern of ridges and grooves is varied across the surface of a of single-pattern light recycling fiim, such as illustrated in Figure 3X. 3Y₁ and 3Z . In such embodiments, the pitch variation is iinear. oscillation, random and pseudo-random. Accordingly, in some embodiments, the pitch may increase and decrease along a direction across the iight recycling film. Still other pitch variations are possible. J000162] Although various embodiments are described herein as having sets of elongate feature with the same pitch, alternatively the pitches of two or more of the sets may be different. In some composite light recycling fiims 116 comprising more than two sets of elongate features a first and second set may have the same pitch while a third set may have a pitch different from the first and second set, Jn other embodiments, ali three sets have different pitches. In a film 11δ with four sets, two, three, or four of the sets may be different and two or three of the sets may be the same. Various other combinations are possible. The number of combinations increases with increasing number of sets of paralie! elongate features.

[000163J Similarly, although various embodiments are described herein as having a constant pitch, alternatively the pitch need not be constant but may vary. In some embodiments only one of the sets has a pitch that varies, in other embodiments, a some but not ail of the sets have a pitch that varies, Jn other embodiments, each of the sets have pitches that vary. In some embodiments, the pitch may vary over portions of the film or over the entire fiim. The pitch may vary but have some pattern- A large range of variation and combinations are possible,

[000164] The composite light recycling fiim 116 illustrated in Figure 3C is formed by combining the array of paraiiei grooves 110 inclined by a first angle α (Figure 3A) with the array of parallel grooves inclined by an angle α' (Figure 3B). in certain modified embodiments, composite light recycling films are formed by combining more than two arrays of relatively parallel ridges or grooves. For example, Figure 4A schematically illustrates a modified light recycling film 112 wherein the ridges 108 anύ the grooves 110 are angled with respect to the x axis by an angle α. where α > 0. Figure 48 schematicaliy illustrates a modified light recycling film 114 wherein the ridges 108 and the grooves 110 are angled with respect to the x axis by an angle α\ where α' < 0. Figure 4C schematicaliy illustrates a tight recycling film 22a wherein the ridges 108 and ths grooves 110 are substantially parallel to the x axis. In one embodiment, the composite pattern of these three light recycling films is used to form a composite tight recycling film.

£000165] Figure 4D schematically illustrates a three-array composite light recycling film 118 formed by combining the pattern of parallel grooves 110 rotated by an angle α (Figure 4A), the pattern of parallel grooves rotated by an angle or^* (Figure 48). and the pattern of parallel grooves that is parallel to the x axis (Figure 4C). Line 112' is parallel to the array of grooves 112 corresponding to modified light recycling film 112, line 114' is parallel to the array of grooves corresponding to the modified light recycling film 114, and line 22' is parallel to the array of grooves corresponding to the light recycling film 22a. Note in this embodiment, a given groove in intersects another groove only once. Figure 4E is a contour plot illustrating the surface profile of the composite light recycling film 118 illustrated in Figure 4D. Figures 4D and 4E show total internal reflection structures comprising pyramid shaped prisms. Figures 4D and 4E also illustrate that the composite light recycling film 118 includes six facets 105 in each period of the composite array. £0001663 When light distributed in a range of angles, for example, Lambertian, is incident on the composite light recycling film 118 illustrated in Figure 4D. the resulting angular distribution of transmitted light is shown in the light intensity plot of Figure 4F. Figure 4H is a histogram of the luminous intensity (measured in candela) for the spatial intensity plot of Figure 4F- This histogram illustrates that the luminous intensity of the transmitted light field is relatively evenly distributed across a wide range of luminous intensities. The luminance of the light transmitted in the central lobe, as well as the shape of the central lobe, depends at least partially on the half angle s(α - o/) between the modified light recycling films 112, 114. Figure 4<3 is a plot of the gain, or luminance enhancement within the lobe, of two crossed two-array and three-array composite light recycling films 116, 118 illustrated in Figures 3C and 4D, respectively, as a function of the half angle |{α - a'} between the angled light recycling film patterns 112, 114. Figure 4G indicates that more light is coupled through the two crossed composite light recycling films when the films are formed with three arrays of parade! grooves 110 instead of two when the half angle ?(α - α') is less than approximately 30*. Figure 4G also indicates that the light recycling film comprising two arrays of parallel grooves 110 has higher gain for half angles above approximately 30°. Accordingly, light recycling films having three arrays of parallel grooves 110 may be more advantageous than light recycling films having two arrays of parallel grooves 110 for a given half angle f(α ~ α'} less than approximately 30°. However, outside this regime, that is, for half angles |{α ~ σ') greater than approximately 30^e, light recycling films having two arrays of parallel grooves 110 may be more advantageous than light recycling films having three arrays of parallel grooves 110. £00018?] Figure 4i is a perspective view of the composite light recycling film 118 illustrated in Figure 4D₁ which has an upright ("everted") configuration, in the upright ("everted") configuration, a viewer looking down one of the grooves 110 sees a line of constant elevation across the light recycling film, and there are no ridgefines of constant elevation in the light recycling film. In contrast to the upright ("everted") configuration, Figure 4J is a perspective view of an inverted composite light recycling film 118'. in the inverted configuration, a viewer looking down one of the ridges 108 sees a ilne of constant elevation across the Sight recycling film, and there are no grooves of constant elevation in the light recycling film,

[0001683 Figure 41 schematically illustrates a composite light recycling films comprising a plurality of sets of parallel elongate features (e.g., first, second, and third sets of elongate features) that do not intersect each other at a single common point. The first and second sets intersect ett set of points, However, the third set of elongate features does not intersect this set of point but is offset therefrom. fOOOi^βSJ The composite light recycling film 118 iifustrated in Figure 40 is formed by combining the array of parallel grooves 110 inclined by an angle α (Figure 4A) with the array of parallel grooves inclined by an angle α' (Figure 4B) and the array of parallel grooves parallel to the x axis (Figure 4C). In this example, as measured along the y axis, the pitch of tne array of parallel grooves parallel to the x axis is half the pitch of the array of parallel grooves inclined by angle cu in certain modified embodiments, composite light recycling films are formed without using an array of elongate features {e.g,, parade! grooves 110} that is parallel to the x axis. For example, Figure 5A schematically iiSustrates a modified light recyciing fiim 112 wherein the ridges 108 and the grooves 110 are angled with respect to the x axis by an angle α, where α > 0. Figure 58 schematically illustrates a modified light recycling film 114 wherein th& ridges 108 and the grooves 110 are angied with respect to the x axis by an angle α'_: where α' < 0- figure 5C schematically iilustrates a modified Sight recycling film 120 wherein the ridges 108 and the grooves 110 are angied with respect to the x axis by an angie ξ, where α > ξ > α' and ξ ≠ 0. in one embodiment, the composite pattern of these three light recycling arrays is used to form a composite Sight recyciing film.

[000170} Figure SD schematically illustrates a three-array composite light recycling film 122 formed by combining the pattern of parallel grooves 110 rotated by an angle α (Figure 5A), the pattern of parallel grooves rotated by an angle α' (Figure 5B), and the pattern of parallel grooves rotated by an angle ξ (Figure 5C), in Figure SD₁ line 112' is parallel to the array of grooves corresponding to modified light recycling Him 112, line 114' is parallel to the array of grooves corresponding to the modified light recyciing fiim 114, anά Sine 120' is paraiiβi to the array of grooves corresponding to the modified light recyciing film 120. £000171 J Accordingly, arrow 112" is directed along one of the grooves 110 in the array corresponding to the modified recycling fiim 112. A viewer iooking along the direction of arrow 112" would look down this groove 110. Arrow 114" is directed along one of the grooves 110 in the array corresponding to the modified recycling fiim 114. Likewise, a viewer iooking along the direction of arrow 114" would look down this groove 110. Similarly, arrow 120" is directed along one of the grooves 110 in the array corresponding to the modified recycling Him 120. Accordingly, a viewer iooking along the direction of arrow 120" would iook down this groove 110.

[000172] in certain modified embodiments, composite fight recycling films are formed by combining more than three patterns of parallel ridges 108 or grooves 110. For example, Figure 6A schematically illustrates a modified light recycling film 112 wherein the ridges 108 and the grooves 110 are angled with respect to the x axis by &n angle et, where α > 0. Figure 68 schematically illustrates a modified light recycling film 114 wherein the ridges 108 and the grooves 110 are angied with respect to the x axis by an angle α\ where α' < 0, Figure 6C schematically illustrates a modified light recycling film 120 wherein the ridges 108 and the grooves 110 are angled with respect to the x axis by an angle ξ, where ξ > 0. Figure 6D schematically iilustrates a modified light recycling film 124 wherein the ridges 108 and the grooves 110 are angled with respect to the x axis by an angle ξ', where ξ < 0. in one embodiment, the composite pattern øf these four light recyciing arrays is used to form a composite light recycling film,

1000173] Figure δE schematically illustrates a four-array composite light recycling film 126 formed by combining the array of parallel grooves 110 rotated by an angle a {Figure 6A), the array of parailei grooves rotated by an angte α' (Figure 6B), the array of parallel grooves rotated by an angle ξ (Figure 6C). and the array of parallel grooves rotated by an angle ξ' (Figure 6D). In Figure 6E, iine 112' is paraϊiel to the array of grooves 110 corresponding to angied iight recycling pattern 112. line 114' is paraliei to the array of grooves corresponding to the angled light recyciing pattern 114, iine 120' is parallel to the array of grooves corresponding to the angled iight recycling pattern 120, and line 124' is paraliei to the array of grooves corresponding to the angied light recyciing pattern 124.

[000174] Accordingly, arrow 112" is directed aiong one of the grooves 110 in the array corresponding to the modified recycling film 112. A viewer looking along the direction of arrow 112" would look down this groove 110. Arrow 114" is directed along one of the grooves 110 in the array corresponding to the modified recycling fiim 114. Likewise, a viewer looking along the direction of arrow 114" would look down this groove 110. Arrow 120" is directed afong one of the grooves 110 in the array corresponding to the modified recycling film 120. Accordingly, a viewer looking aiong the direction of arrow 120" would look down this groove 110. Similarly, arrow 124" is directed along one of the grooves 110 in the array corresponding to the modified recyciing fiim 124. Likewise, a viewer looking aiong the direction of arrow 124" wouid look down this groove 110. The composite light recycling film 126 includes eight facets in each period of the composite array. [Q0017SJ When iight distributed in a range of angles, for example, Lambertian, is incident on the composite iight recyciing film 126 illustrated in Figure 6E, the resulting pattern of transmitted iight is shown in the light intensity plot of Figure SF. The luminance of the light transmitted in the centrai lobe, as well as the shape of the central lobe depends on a variety of factors. Such factors include but are not limited to (i) the half angle |(α ~ a') between the modified iight recycling film patterns 112, 114; and (ii) the angle (α ~ ξ) between the modified light recycling fifrn patterns 112, 120.

£0001763 As described herein. Figure 40 illustrates a composite light recycling film 118 formed by combining the pattern of parallel grooves rotated by an angle α (illustrated in Figure 4A; referred to herein as "the ct pattern") with the pattern of parallel grooves rotated by an angle α' (illustrated in Figure 48; referred to herein as "the ct' pattern") and the pattern of parallel grooves thai is parallel to the x axis (illustrated in Figure 4C; referred to herein as "the x axis pattern"). The gain (luminance enhancement on-axis) of the iight transmitted through the composite three-array light recycling film 118 illustrated in Figure 40 depends on the depth of the x axis pattern relative to the α pattern and the σ' pattern. Figure 7A is a piot of the gain as a function of the relative depth Δz of the x axis pattern relative to the α pattern and the α' pattern. This piot is for half angle i(α - a') of 15° although the vaius of half angle |(α ~ α') may be different in different embodiments.

[000177J in embodiments wherein the x axis pattern has the same depth as the α pattern and the a' p&V&m, that is when Oz - O₁ the structure and optical properties of the resulting composite light recyciing film are identica! to the composite light recycling film 118 iiiustrated in Figure 40. In embodiments wherein the x axis pattern is sufficiently deep, that is when Δz « 0_s the α pattern and the a' pattern are effectively eliminated, and the structure and opticai properties of the resuiting composite light recyciing film are identical to the light recyciing film 22a illustrated in Figure 2A. in embodiments wherein the α pattern and the α' pattern &rQ sufficiently ύeep, that is when &z » 0, the x axis pattern is effectively eliminated, and the structure and optica! properties of the resulting composite light recycling film are identical to the composite light recycling fiim 118 illustrated in Figure 3C.

[00017Sj Figure 7A indicates that more iight is coupled through a composite light recycling film in the case wherein the film is formed with the x axis pattern only, as compared to composite light recyciing films having contributions from the α pattern md the α^r pattern. More significantly. Figure 7A indicates that the gain of the composite light recycling fiim 118 can be manipulated by adjusting the depth of the x axis pattern. Figures 7B through 7F provide top surface views of composite light recycling films 116, 118, 128, 130, 22a corresponding to selected data points illustrated in Figure 7A, In particular, Figure 7B is a top surface view of a composite light recycling film 116 wherein the α pattern and the a' pattern are sufficiently deep so that the x axis pattern is effectively eliminated in the composite Sight recycling film 116. Figure 7C is a top surface view of a composite iight recycling Him 118 wherein the x axis pattern has the same depth as the α pattern and the α' pattern, such that alf three patterns are evident in the composite light recycling film 118, Figure 70 is a top surface view of a composite iight recycling fiim 12S corresponding to data point 7D in Figure 7A, wherein the x axis pattern is deeper than the α pattern and the α' pattern, such that ail three patterns are evident in the composite light recycling film 128. Figure 7E is a top surface view of a composite light recycling fiim 130 corresponding to data point 7E in Figure 7A₁ wherein the x axis pattern is deeper than the α pattern and the α' pattern, such that all three patterns are evident in the composite light recycling fiim 130. Figure 7F is a top surface yiew of a iight recycling film 22a wherein the x axis pattern is sufficiently deep so that the α pattern and the α^* pattern are effectively eliminated in the light recycling fiim 22a.

[OOO18O3 Figures 8A through 8C are schematic cross-sectional views (parallel to yz plane) of portions of the composite tight recycling film 118 similar to the light recycling film iliustrated in Figure 4D. in the exampie embodiments illustrated In Figures 8A through 8C, α » +11.3° and α' ∞ ~α. Figures BA through 8C illustrate a plurality of example ray traces that demonstrate how light incident on the Sight recycling film 118 is either transmitted through the composite iight recycling film 118, or is reflected back towards the iight guide 18. For example, in Figure 8A, ray traces of light rays 132 indicate that the composite iight recycling film 118 transmits light that exits the film within a range of angles ±θ. While selective rays traces are shown in Figure 8A for illustrative purposes, other ray paths are possible.

[0001813 in contrast, Figure SB illustrates ray traces of example light rays 136 that are not transmitted through the composite light recycling film 118, but that are instead reflected back toward the light guide 18. After being reflected to the light guide 18, the liøht rays 136 may scatter from an extractor and possibly be refiected by the rear reflector 16, thereby enabling them to return to the composite light recycling fiim 118 at a different incident angle, in embodiments wherein most or all of the light transmitted by the composite light recycling film 118 is transmitted within a range of angles ±θ. the transmitted light intensity pattern illustrated in Figure 4F may result. As stated above, while selective rays traces are shown in Figure 8A for iilustrative purposes, other ray paths are possible, [Q00182] in Figure 8C_{ ray traces of light rays 134 indicate that the composite light recycling film 118 does not transmit light at certain angles. Accordingly, a viewer viewing the display 10a from such angles would not see features such as the extractor elements rearward of th® light recycling film 118. As stated above, while selective rays traces are shown in Figure SA for illustrative purposes, other ray paths are possible. |000183| As described above, In various embodiments the spatial light modulator 24 is pixilated, In such embodiments, an individual pixel in the spatiai Sight modulator 24 receives light from particular portions of the light guide 18, The portions of the light guide 18 that illuminate a particular pixel are determined by back tracing rays from the pixel through the light recycling film 22a and to the light guide 18. Figure SD is a schematic cross-sectional view (parallel to yz plane) of a portion of the light recycling film 118, illustrating a plurality of coiiimaled light rays 30 that have been traced from a selected pixel 28 of the spatial light modulator 24, through the light recycling film 118, and toward the light guide 18. As illustrated in Figure 8D, the back ray traces of a cross-section through the light recycling film 118 for light originating from the pixel 28 are traced at two distinct angles JS₁ and β₂ to two distinct spatial regions 32 of the light guide 18. Because the facets 10S are also tilted in the x axis (not visible in Figure 8D), the number of distinct angles through which light is traced is greater than that illustrated in the yz plane of Figure 8D, The relative area of the facets, as projected in the xy plane, wiil determine the relative magnitude of light at each of the distinct angles. More particularly, the projected area, the area projected onto a surface such as the front or rear surface of the light guide, determines this magnitude, in various embodiments, the total internal reflection structure comprises facets of substantially equai area so as to increase the uniformity of the illuminance of the display, in modified embodiments, curved facets, curved surface, and/or curved ridgeiines may blur the distinct angles. When curved surfaces are used, these surfaces may have substantially similar projected area values so as to reduce non-uniformity in the illuminance of the display. Tuning the angles and the projected area of the different facets provides an ability to control the correlation between the light recycling film, the light guide extractor pattern, and the pixels in the spatial light modulator.

£0001843 Figure SA is a schematic cross-sectional view (parallel to yz plane) of the backiit display 10a illustrating the ray traces shown in Figure 8D, As expounded herein, the back ray traces of light originating from the pixel 28 are traced to two distinct spatial regions 32 on the rear surface 18' of the light guide 16. Figure 9B schematically illustrates the relative size of the pixel 28 and the array of parallel ridges 108 and grooves 110 comprising the light recycling film 22a in an exampie embodiment, As illustrated, the dimensions of the pixel 28 are significantly larger than the dimensions of the ridges 108 and grooves 110 parallel to the y axis. Figure 9C is a plot of the illuminance of light projected onto the rear surface 18' of the light guide 18, illustrating the two spatial regions 32 which are illuminated by the back traced coilimated light rays 30. In modified embodiments, the sima of the two spatial regions is increased by including a diffuser 22a in the backiit display 10a. Figure 9D is a plot of the illuminance of iight projected onto the rear surface 18' of the light guide 18 when a 3^* Gaussian diffuser is included in the backiit display 10a. The shape of the Gaussian scatter distribution, ScafterCrj), is defined by

Scatter^/) * exp ( --- I--fV --_τ^ j L

I ²W))

[000185J where η is the scatter angle measured with respect to the specular direction.

[000186] Figure 9£ is a plot of the illuminance of light projected onto the rear surface 18' of the light guide 18 when a 10° diffuser is included in the backiit display 10a. in modified embodiments, the diffuser 20a is optionally incorporated into the light recycling film 22a_t such as by applying the diffuser 20a to the light recycling film first surface 104 or second surface 106, or by incorporating scattering materials within the film to form volume diffusing features. The scatter produced by the diffuser can be asymmetric with more or less scatter aiong the axis of the ridges and grooves than along the axis perpendicular to the ridges and grooves. In certain embodiments, the light recycling film first surface 104 and/or second surface 106 are provided with a roughened surface. The roughened surface can be achieved by subjecting the light recycling film to a surface treatment, such as sanding. The roughened surface can also be achieved by cutting the ridges 108 and grooves 110 using a modified cutting tool, such as cutting toot with a diamond mϊcroslructure on the cutting edge, In still other embodiments, the roughened surface is achieved by cutting the ridges 108 and the grooves 110 using a modified cutting technique that produces a greater surface δ roughness, such as a laser cutting technique. Surface roughness can be added to individual Sight recycling films or to a master die or mold used to form individual light recycling films.

$5001873 As described herein, in various embodiments, at ieast one surface of the light guide 18 includes a plurality of extraction elements that are configured to allow a 0 portion of the light propagating m the light guide 18 to be coupled from the light guide 18. In one embodiment: the extraction efements comprise an array of raised or recessed features such as bumps or dimples formed on the rear surface 18' of the light guide 18. Figure 10A schematically illustrates an example embodiment of an example array of extraction elements 34. By projecting the two illuminated spatial regions 32 5 onto i^e array of extraction elements 34 if is possible to determine which extraction elements contribute to the illumination of the selected pixei 28.

£000188] Figure 10B schematicaiiy illustrates the projection of the illuminated spatiai regions 32 (frustrated jπ Figure 9B) onto the array of extraction eiements 34 (illustrated in Figure 10A). In certain embodiments, the illumination of the selected 0 pixei 28 depends on how the extraction elements 34 are aligned with the illuminated spatiai regions 32 that correspond to the seiected pixei 28. For exampie, in the projection iiiustrated in Figure 108, the selected pixel 28 will be relatively under- illuminated because the extraction elements 34 are not well-aligned with the illuminated spatial regions 32 corresponding to the selected pixel 28. In contrast, Figure 10C 5 schematically illustrates th& effect of translating the array of extraction eiements 34, such that the extraction elements 34 are weif-aiigned with the illuminated spatiai regions 32. Specificaliy, in the projection illustrated in Figure 10C₁ the seiected pixei 28 is relativeiy over-illuminated because the extraction elements 34 are weil-aligned with the illuminated spatiai regions 32 corresponding to the selected pixel 28. 0 [000189] The projection illustrated in Figure 9C of the seiected pixei 28 on the rear surface 18' of the light guide 18 was obtained using the tight recycling film 22a iiiustrated m Figure 2A, This projection is modified when the light recycling Him 22a is replaced with a composite iight recycling film comprising a plurality of arrays of parallel ridges 108 and grooves 110. Figure 11 A, for example, schematically illustrates a composite Sight recycling film 116 comprising two-arrays such as illustrated in Figure 3C. Figure 11 A also shows a projection of the pixel 28 over the pattern of grooves 110 that comprise the composite light recycling film 116. As described herein, composite light recycling film 118 is formed by combining the pattern of parallel grooves 110 rotated by an angle α (Figure 3A) with the pattern of parallel grooves rotated by an angle σ' (Figure 3B). Figure 11S is a plot of the illuminance of light projected onto the rear surface 18' of the light guide 18 when the backiit display 10a includes the composite Sight recycling film 116 illustrated in Figures 3C and 11 A. As illustrated, the modified projection includes four illuminated spatial regions 32, instead of the two illumined spatial regions obtained when the light recycling fiim 22a comprising a single array of parallel ridges 10S and groove 110 was used,

[0001813 As another example, Figure 12A schematically shows a composite light recycling film 118 comprising three arrays of parallel grooves 110 such as illustrated in Figure 4D. Figure 12A also shows the projection of the pixel 28 over the pattern of grooves 110 that comprise the composite light recycling film 118. As described above, this composite light recycling fiim 118 is formed by combining the array of parallel grooves oriented at an angle α, referred to above as the α pattern, (Figure 4A) with the array of parallel grooves oriented at an angle α', referred to above as the α' pattern, (Figure 4B) and the array of grooves parallel to the x axis, referred to above as the x axis pattern, (Figure 4C). Figure 12B is a plot of the illuminance of light projected onto the rear surface 18' of the light guide 18 when the backiit display 10a includes the composite light recycling film 118 illustrated in Figures 4D and 12A. As illustrated, the modified projection includes six iiluminated spatial regions 32. The six illuminated spatial regions correspond to the six facets 105 illustrated in Figures 4D and 4E. In general, a composite light recycling fiim having n facets per array period will project 2n illuminated spatial regions onto the rear surface of the light guide when rays are back- traced through the composite light recycling film.

[000102} As described herein, the gain of the light transmitted through the composite light recycling fiim 118 depends on the depth of the x axis pattern relative to the α pattern and the α' pattern. As a result of this effect, the relative magnitude of the illuminated spatial regions 32 is controllable by adjusting ihef relative depth Δz of the x axis pattern relative to the α pattern and the α' pattern_* Figure 12C, for example, schematically illustrates the pattern of ridges and grooves that comprise a composite light recycling film 138 wherein the relative depth Δz ~ +0.GG5. Figure 12C, also shows the projection of the pixel 28 over this composite light recycling film 138, Figure 12D is a plot of the illuminance of light projected onto the rear surface 18' of the light guide 18 when the backiit display 10a includes the composite light recycling film 138 illustrated in Figure 12C, As iiiustrated, the relative magnitude of the Individual illuminated spatial regions 32 has been modified as compared to the embodiment illustrated in Figures 12A and 128, wherein Az ~ 0. Tuning Az changes the relative projected at& of the facets in the light recycling film, as described herein. £000193] In certain embodiments, the backiit display 10a includes a "crossed" light recycling film formed by overlaying two light recycling films at a right angle to each other. For example, Figure 13A schematically illustrates crossed light recycling films 140 formed by overlaying a light recycling film 22a having grooves and ridges parallel to the x axis with a light recycling film 22a having grooves and ridges parallel to the y axis. Figure 13A also shows the projection of the pixel 28 over the crossed iight recycling films 140.

[00G1S4] Figure 138 is a plot of the Illuminance of light projected onto the rear surface 18' of the light guide 18 when the backiit display 10a includes the crossed light recycling films 140 illustrated in Figure 13A. As illustrated^ there are four illuminated spatial regions 32 on the rear surface 18'. This distribution is in contrast to the two illuminated spatial regions 32 generated when light is projected through individual (uncrossed) iight recycling films, as illustrated in Figure 9C. Generally, in some embodiments, if iight projected through a selected light recycling film generates n illuminated spatial regions 32 on the rear surface 18', then light projected through crossed light recycling fiims comprising two orthogonal selected light recycling films will generate n² illuminated spatial regions 32 on the rear surface 18'.

[000135] As another example. Figure 14A schematically illustrates crossed light recycling films 142 formed by overlaying two of the two-arrayed composite light recycling films 116 illustrated in Figure 3C orthogonal to one another. As described herein, the composite two-array light recycling film 116 shown in Figure 3C is formed by combining the pattern of parallel grooves rotated by an angle α {Figure 3A) with the pattern of parallel grooves rotated by an angle α' (Figure 3B). Figure 14A also illustrates the projection of the pixel 28 over the crossed iight recycling film 142. Figure 14B is a plot of the illuminance of light projected onto the rear surface 18' of the light guide 18 when the bacKlit display 10a includes the crossed light recycling film 142, As explained above, and as illustrated in Figure 11 B, projecting light from the pixei 28 through a two-array composite light recycling film 118 generates four illuminated spatial regions 32 on the rear surface 18'. Therefore, projecting light through the crossed two- array light recyciing films 142 generates 4^s ~ 16 iiiυminated spatial regions 32 on the rear surface 18', as illustrated in Figure 14S.

[000196J As another example, Figure 15A schematically illustrates crossed light recycling films 144 formed by overlaying two of the three-array composite light recyciing films 118 illustrated in Figure 4D orthogonally. As described herein, the three-array composite light recyciing film 118 shown in Figure 4D is formed by combining the α pattern (Figure 4A) with the α' pattern {Figure 4B) and the x axis pattern (Figure 4C). Figure 15A also shows the projection of the pixel 28 over the crossed light recycling film 144. Figure 158 is a plot of the illuminance of iight projected onto the rear surface 18' of the light guide 18 when the backlit display 10a inciudes the crossed iight recycling films 144, As explained above, &nύ as illustrated in Figure 128, projecting light from ihβ pixel 28 through a three-array composite light recycling film 118 generates six illuminated spatial regions 32 on the rear surface 18\ Therefore, projecting light through the crossed light recycling films 144 generates 6² ~ 38 illuminated spatiai regions 32 on th& rear surface 18', as illustrated in Figure 15B.

[000197] Figure 15C illustrates crossed light recyciing films 148 formed by overlaying two of the three-array composite iight recycling films 138 illustrated in Figure 12C orthogonally. As described herein, the three-array composite light recyciing film 138 shown in Figure 12C is formed by combining the a pattern with the α' pattern anά the x axis pattern, wherein the relative depth Δz of the x axis pattern relative to the α pattern and the a' pattern is +0.005. Figure 15G also shows the projection of the pixei 28 over the crossed three-array iight recycling films 146. Figure 15D is a plot of the illuminance of light projected onto the rear surface 18' of the iight guide 18 when the backϊit display 10a includes the composite iight recycling films 146 illustrated in Figure 15C. As illustrated, the relative magnitude of the individual illuminated spatiai regions 32 has been modified as compared to the embodiment illustrated in Figures 15A and 15B₁ wherein Δ2 - 0. Although identical recycling ftims are crossed in the examples described above, tlie two constituent Sight recycling films that are crossed need not be identical. For example, in a modified embodiment the composite light recycling film 116 illustrated in Figure 3C (two arrays) is crossed with the composite light recycling fiim 118 illustrated in Figure 4D (three arrays). In another modified embodiment, the composite iight recyciing film 118 illustrated in Figure 4D (three arrays) is crossed with the composite iight recyciing film 126 iiiustrated in Figure 6E {four arrays). Other combinations are used in other embodiments, Additionaliy, more than two arrays may be crossed. Similarly, in certain modified embodiments the crossed iight recycling films are crossed at an angie that is less than or greater than 90".

[000199] in modified embodiments, certain of the light recycling films disclosed herein are sequentially positioned in the backiit display 10a. For example. Figure 19A iliustrates the light recycling film 22a (of Figure 2A, the x axis pattern) positioned over the modified light recycling fiim 112 (of Figure 3A, the α pattern), which is positioned over the modified iight recycling film 114 (of Figure 3B₁ the α' pattern). In other embodiments, these three light recycling films are sequentially positioned in a different order. The embodiment illustrated in Figure 19A is different from the embodiment illustrated in Figure 40, which illustrates the same three iight recycling films combined onto a single composite light recyciing fiim 118. JΩGG2OO3 Specifically, when a plurality of light recyciing fiims are positioned sequentϊaiiy, as iiiustrated in Figure 19A, the resuiting structure operates differently than a composite iight recyciing film, such as the composite iight recyciing film 118 illustrated, in Figure 4D, in particular, the sequentially-positioned iight recyciing films cause light to circulate in the region or regions between the fiims. For exampie, in the embodiment illustrated in Figure 19A, iight circulates in a region between the light recyciing fiim 22a and the modified iight recycling fiim 112, as weii as in a region between the modified iight recycling film 112 and the modified iight recycling film 114. in contrast, there is no "inier-fiim" iight circuiation in the single film embodiment illustrated in Figure Φ. [000201] Because the sequentially-positioned iight recycling films illustrated in Figure 19A operate differently, the resuiting spatiai intensity of light transmitted by the films is modiffed as compared to the single composite light recyciing fiim. Figure 19B is a plot of intensity versus angie in the vertical and horizontal directions (parallel to ihe x and y axes, respectively) of the transmitted light distribution for the three sequentially- positioned light recycling films illustrated in Figure 19A, As illustrated, this distribution pattern is different from that shown in Figure 4F, which corresponds to the single composite light recycling film 118. [0QQ202] Figure 19C is a histogram of the luminous intensify (measured in candeia) for the spatial intensity plot of Figure 198. This histogram illustrates that the luminous intensity of the transmitted Sight field is not evenly distributed across a wide range of luminous intensities, in particular, Figure 19C shows that more light having a relatively lower intensity is transmitted (indicated by bulge 90), as compared to light having a relatively higher intensity {indicated by recessed region 92), This intensity distribution illustrated in Figure 19C shouid be contrasted with the corresponding distribution for the composite light recyciing film 118, illustrated in Figure 4H₁ which illustrates that the composite light recycling IHm 118 produces a substantially more evenly distributed intensity distribution. $00203} In certain embodiments, a composite light recycling film is formed that includes the patterns of two or more recyciing films that ar& crossed with respect to each other. Such composite light recycling films may resemble, for example, the crossed light recycling films in Figures 13A, 14A, 15A₁ and 15C. Other patterns may be used as welϊ. [0002043 ^Trιe various embodiments described herein allow the light illuminating the selected pixel 28 to be "collected" from a larger area of the light guide 18, and possibly from a larger number of extraction elements 34. As described above and illustrated in Figures 10B and 1OC, collecting light for a pixel from a small number of extraction elements 34 causes underillumination of some pixels and over-illumination of other pixels. When more extractors contribute light to each of the pixels, the different pixels in the spatial light modulator are more uniformly illuminated as a consequence. Other Moire effects are also attenuated as well. In particular, Moire effects may be generated or enhanced when periodic illumination patterns &m produced at the spatial light modulator, which comprises a periodic array of pixels. Such periodic illumination patterns may result from underillumination of some pixels and over-illumination of other pixels. Causing the array of pixels to be more uniformly illuminated reduces the periodicity in the illumination pattern that contributes to the Moire effect. While a diffυser can aϊso be used to reduce Moire effects, use of diffusers, and especially high angle diffusers. can disadvantageous reduce the luminance of light transmitted through the backlit display 10a at usable angles. Therefore, employing the techniques disclosed herein to collect iight from a larger number of extraction elements allow the dtffuser to be eliminated, or allow a lower-angle diffuser to be used, thereby increasing the luminance at the most desirable angles.

[00020$] Another technique for collecting light from a larger number of extraction elements 34, thereby providing more uniform illumination and reducing yoir& effects, is to rotate the light recycling film with respect to the selected pixel 28 and the array of extractor elements. For example, Figure 18A schematically illustrates the projection of the selected pixel 28 on the crossed three-array Sight recycling fiϊms 144, wherein the pixel snύ the films have been rotated with respect to each other. When light is projected through the rotated and crossed light recycling films 144 onto the rear surface 18' of the light guide 18, the resulting pattern of illuminated spatial regions 32 is rotated, as illustrated in Figure 168. The rotated pattern illustrated in Figure 188 advantageousϊy reduces ih& correlation between the illuminated spatial regions 32 and the pattern of extraction elements 34. If the extraction elements 34 are arranged in a linear grid pattern, then increased Moire effects can disadvantageousiy occur if the illuminated spatial regions 32 are well-aligned with the pattern of extraction elements 34. The number of extraction elements 34 from which light is drawn is further increased by including a diffuβer 20a in the backiit display 10a, as illustrated in Figure 16C.

£0002073 As described above, by increasing the spatial area of the portion of the light guide from which light is extracted to iiiuminate a selected pixel, more uniform illumination can be provided at the spatial iight modulator and Moire effects are reduced, in an embodiment wherein the extraction elements are arranged in a rectangular grid, such as illustrated in Figure 10A, the illumination patterns of Figure 16B and 16C advantageously draw light from every row and every column of extraction elements. (Since "row" and "column" are merely relative terms, depending on orientation, they are used interchangeably herein.) This advantageously provides another degree of freedom to reduce Moire effects. By Nominating a greater number of extraction elements, correlation between the illuminated spatial regions and the pattern of extraction elements is reduced, Specifically, by drawing light from a larger number of extraction elements, and from extraction eiements that are more spatially distributed, the spatial variance in the extracted light is less pronounced. Rotating further reduces the correlations with extractors that are placed on a grid pattern. A similar effect can be achieved by rotating the array of extraction elements with respect to the iight recycling film.

£GG02Q8J As described above, the light recycling fiims may be disposed between the light guide and the spatial light modulator to control the fleld-of-view of the display and provide luminance enhancement within that fϊeld-of-view. Additionally, the light recycling fiims described herein can increase the uniformity of illumination of the display and reduce Moire effects.

£000209] in other embodiments, the iight recycling fiims can be disposed between the tight source and the Sight guide to provide mixing of the light source. For example, light sources that generate substantial monochromatic Sight at one or more selected wavelengths, such as RGB LED arrays, generally can benefit from mixing to produce white fight or colors formed by combinations the monochromatic light, for example, red, green, or biue. Because certain of the light recyciing fiims disclosed herein collect light from a variety of locations &nά direct this light into a localised area (for example, a pixel), these light recycling fiims advantageoυsiy provide the additional mixing required when a plurality of separate monochromatic Sight emitters are used. The light recyciing of the light recycling fiim may aάά to this mixing process.

[000210] Figure 17 illustrates selected components of a color backlit display 50. wherein a first light recycling film 52, such as one or more of the light recycling films disclosed herein, including the composite light recyciing films anύ crossed light recycling films described above, is positioned between a light source 54 having a plurality of monochromatic eiements anύ a light rod 56. In such embodiments, a second light recyciing film 58, such as one or more of the light recycling films disclosed herein, including the composite light recyciing fiims and crossed light recycling films described above, is positioned between the light rod 3§ and a pianar light guide 60. Other components may be placed above the planar light guide 60 (in the +z dimension). Such optional components may include other light recycling fiims, optional diffusers, and spatial light modulators; these components, however, are omitted from Figure 17 for clarity. £000211] The color bacKiit display 50 illustrated in Figure 17 advantageously provides enhanced mixing of the colors generated by the light source 54 comprising a plurality of monochromatic light emitters. The first Sight recycling fiim 52 causes each location on the ®nά of the light rod 58 to receive light from a plurality of separated sites on the iiøht source 54. These sites may include, for example, different dies in an RG8 LED array. Similarly, the second light recycling film 58 causes each location or? the edge of the iight guide 60 to receive Sight from a plurality of separated sites on the edge of light rod 56. More extensive color mixing is thereby provided. For example, in embodiments wherein individual rows of extractor elements correspond to different color emitters, certain of the iight recycling films disclosed herein will advantageously mά substantially increase the number of colors supplied to an individual pixel in the spatial light modulator.

£0002123 Ivlore or less light recycling films may be included in other embodiments. For example, in alternative embodiments, only one of the first and second light recycling films 52, 58 may be included. Also, the light rod 56 may be excluded in certain embodiments,

{ΦQ02133 In one example embodiment, an array of light sources is disposed &i sn edge of the light guide, A light recycling film disposed between the array of light sources and the light guide causes mixing of the light directed into the iSghi guide. In the case where the array of light sources comprises an array of different color light emitters, the iighi recycling film provides color mixing. Additional elements may be included in the display and the configuration may vary.

J0002143 in another embodiment, for example, a compound parabolic type collector is used to couple light from the array of light sources 54 to the first light recycling film 52. Figure 18 illustrates an example embodiment of selected components of a color backiit display 50 that includes an array of colored iight sources 54 that is configured to couple light into a compound parabolic collector 62. The compound parabolic type collector 62 is configured to efficiently distribute light to a first iight recycling film 52, such as one or more of the light recycling fiims described herein, including but not limited to the composite iight recycling fiims and crossed fight recycling fiims described above, in an example embodiment, the compound parabolic type collector 62 is an optically transmissive non-imaging optica! element wetted to a high refractive index material covering the array of light sources 54. The angular distribution of iight exiting the non-imaging optica! element is large_* and therefore the non-imaging optical element efficiently couples light from the array of light sources 54 to the first light recycling film 52. The non-imaging optical element can be made to provide more coilimation by wetting the light recycling film to the output face of the non-imaging optical element In 5 certain embodiments, the compound parabolic type collector 62 as well as the iigbt- recyciing film 52 advantageously mixes the light generated by the array of light sources 54. Other types of non-imaging opticai elements (as well as imaging optical elements) may be used in different embodiments. Additionally, additional components such as a light guide, a diffuser, one or more additional fight recycling films anά a spatiai light 0 modulator may aiso be included.

[000215] Although light sources comprising a plurality of different color may benefit from the use of light recycling fϊims, light sources that emit a single color as well as white light sources may aiso benefit For example, the Sight recycling film may advantageously mix the ϋghi from the light source to produce a more uniform intensity 5 output.

£0002163 Although specific examples have been described above, wide variation in design iβ contemplated. For example, the number, size, dimension, shape, configuration, arrangement, and order of the various components can vary. For example, the light recycling structure, also referred to herein as an optica! member 0 having a plurality of total internal reflection structures formed thereon, need not be limited to s film, In addition to being a sheet or layer, the fight recycling structure more generally can have any other length, width, thickness or shape. The light recycling structure can be rigid or flexible. A film may be flexible and may rely on another structure such as a substrate for support and/or to provide rigidity. As used herein a S film may be O.δ mm or thinner, in contrast, a sheet is thicker. The light recycling structure can be integrated together with another element. For example, the prisms may be formed on a diffuser or iight guide. Accordingly, the functionality of the diffuser or iight guide as described above can be combined in a single component with the light recycling structure. The prisms forming the light recycling structure may also be 0 integrated on filters, lenses, or other optical or non-optical components.

[0002173 Additionally, the light recycling structures can be included together with any one or combination of the components described herein such as the light sources, the iight guide, reflector, the diffuser, and the spatiai light modulators. Accordingly, any of these components can be excluded. Similarly, additional components may be adά&ό, The components themselves may be different than specifically disclosed herein. For example, although the shape of the light guide, reflector diffuser, light recycling structure and spatial Sight modulator have been described as planar, other shapes, sizes, and configurations are possible. The order of the components may also vary. Similarly, the different components can be assembled together in different ways. For example, some or all of the elements may be laminated together. The components may be otherwise mechanically secured in position with respect to each other.

£GU021ff| Similarly, although the light recycling structures have been described for use in displays, the light recycling structures can be used in other applications as well. For example, the light recycling structures may be used in lighting such as for portable lights including flashlights, for display lighting, down lighting, architectural lighting, automobile, nautical, aviation lighting, mti signage,

£0002193 Certaϊπ of the Sight recycling structures disclosed herein may also be used in other types of light apparatus. Such lighting apparatus may be used, for example, for down lighting, display case lighting, outdoor lighting, architectural lighting, and the like. For example, such lighting apparatus may be used in applications where a more focused beam of fight is to be directed to a target. Such lighting apparatus may comprise one or more ifghf emitters, a light box, a diffuser. and a light recycling film. Figure 20 is an exploded view of selected components of an example embodiment of lighting apparatus 70 that includes a light emitter 72 positioned within a hollow light box 74. in an example embodiment, the interior wails of the hollow light box 74 &re provided with a light colored or reflective surface to decrease the amount of liøht absorbed by the walls of the walls 74, These wall may for example be painted white. These walls may form a highly reflecting diffuse surface, In an example embodiment, the Sight emitter 72 is a fluorescent Sight bulb, although other Sight emitters are used in other embodiments, such as incandescent light bulbs, gas discharge lamps, arrays of light emitting diodes and the like. In certain embodiments, the lighting apparatus 70 includes a combination of different types of light sources. [000220] Still referring to Figure 20. an optional diffuser 76 is positioned over one side of the light box 74, mά a Sight recycling film 78 is positioned over the diffuser 76. These components 76, 78 are arranged such that light generated by the light emitter 72 passes through the optional diffuser 78 and the light recycling film 78 as it exits the light box 74, In certain embodiments the diffuser 76 is excluded as the iight box 74 is effectively a diffuser. For example, the inferior walls may be diffusely reflecting and rny diffuse the Sight from the light emitter 72. The fight recycling film 78 may alternatively comprise a plurality of iight recycling films and may Include any of the light recycling films disclosed herein, or an equivalent thereof. Such a light recycling film 78 used with a light apparatus 70 such as shown may have ridges and grooves with larger dimensions than with a light recycling film used with a spatial light modulator, as disclosed in certain of the other embodiments described herein.

£0002213 The lighting apparatus light 70 may have a wide variety of different configurations, and is not limited to boxiike shapes or other rectangular forms. For example, Figure 21 illustrates a light apparatus 80 that is cylindrical. This lighting apparatus 80 includes certain of the components of the lighting apparatus 70 illustrated in Figure 20. In the embodiments shown in Figure 21 , however, the holϊow light box is replaced with a solid iight guide 74, configured to transmit tight from light emitters disposed about the edges of the light guide 72- The iight guide 74 may comprise a solid material that is substanfiaiϊy optically fransmisssve to the wavelength of iight output by the emitters. The light guide 72 Sn Figure 21, as well as the hoilow light box shown in Figure 20 may be generally referred to as iight boxes,

[GGG222J Other designs for the lighting apparatus as weii as for the light recycling film are possible. For example, in certain embodiments, the elongate features in the light recycling films described herein may comprise nonlinear elongated features. Figure 22A is a top surface view (parallel to the xy plane) of such an example embodiment comprising a light recycling film 160 having a nonlinear pattern of elongated features, in this example embodiment, the light recycling film includes a plurality of nonlinear, nonintersecting ridges 162 and grooves 164. Each ridge 162 and groove 164 extends longitudinally in a direction parallel to the x axis. The ridges 162 and grooves 164, however, simultaneously oscillate in a lateral direction that is parallel to the y axis in this example. As shown, ridges 162 and grooves 164 are laterally displaced in an undulating manner, up and down in the +y and -y direction as the ridge 182 and groove 184 progresses left to right along the x direction. The amount off lateral displacement of the ridges substantially matches that of the grooves such that the width of the ridges and grooves as well as their periodicity is unchanging with position. e.g_M from left to right or along the x axis. The width and periodicity need not be so limited in different embodiments. Figure 228 is a cross-sectional view (parallel to yz plane) of the Sight recycling film 160 of Figure 22A,

J000223J WMe the example light recycling film 160 illustrated in Figure 22A includes a pattern of ridges and grooves having a sinusoidal oscillation pattern, other nonlinear spatiaiiy varying patterns are used in other embodiments. These non-linear patterns may be oscillating and may have a period oscillation that is constant or that varies, in some embodiments, the pattern may have sharper turns upward and downward along ϊhe y direction, and may for example, be characterized more as "zigzag". The turns may, however, be smooth in some embodiments. Random and pseudo random patterns are aiso possible.

[000224J When used with a backJit dispfay, the light recycling film 160 illustrated m Figure 22A and 228 is advantageously capable of collecting light from a larger spatial ®rea of the light guide 18, For example, when light rays are traced through two sequential light recycling films 160 that are crossed perpendicular to each other, the resulting pattern of illuminated spatial regions on the rear surface 18' of the light guide 18 are illustrated in Figure 22C. As illustrated, this pattern of illuminated regions Es substantially larger than the pattern associated with two sequential linear light recycling films 22a, as illustrated in Figure 13B. Moire effects resulting from periodic extractor patterns may be reduced with this larger pattern as described above. While the light recycling films 160 used to obtain the pattern iflustrated in Figure 22C were crossed at a 90" angle, the films are crossed at other angles in other embodiments. A diffuser is optionally used to diffuse the light from the light guide 18 and further reduce the Moire effect; Figure 22D is a plot of the illuminance of fight projected onto the rear surface 18' of the light guide 18 when a 3^* Gaussian diffuser is included. [0002253 In a modified embodiment, multiple nonlinear arrays of elongate features illustrated in Figure 22A are combined on a single light recycling film, For example, Figure 22E illustrates a composite nonlinear light recycling film 160' formed by combining two of the light recycling films 160 depicted in Figure 22A oriented at a right angle. This combination produces an array of pyramids with nonlinear sides, [000226] in this example embodiment, the light recyciing film includes a first set of nonlinear, non-intersecting grooves 164a as well as a second set of nonlinear, non- intersecting grooves 164b, in this particular embodiment, the first ancf second sets of grooves 164a, 164b_> are oriented substantially orthogonal to each other,

£0002273 In the embodiment shown, for example, each groove 164a in the first set extends longitudinally in a direction parallel to the x axis. The grooves 184a, however, simultaneously osculate in a iaterai direction that is parallel to the y axis in this example. As shown, grooves 164a are laterally displaced in an undulating manner, up and down in the +y and -y direction as the groove 164a progresses ϊeft to right along the x direction. The width of the grooves 164a as wei! as their periodicity is unchanging with position, e.g.. from left to right or along the x axis.

Additionally, each groove 164b in the second set extends longitudinally in a direction parallel to the y axis. The grooves 164ø_t however, simultaneously oscillate in a lateral direction that is parallel to the x axis in this example. As shown, the grooves 164b are laterally displaced in an undulating manner, left and right m the -x and +x direction as the grooves 164b progresses upward along the y direction. The width of the grooves 184b as we!! as their periodicity is unchanging with position, e.g.. with movement upward or along the y axis, although in other embodiments the width anά periodicity may change.

[000229] While the example light recycling film 160 illustrated in Figure 22A includes first snά second patterns of grooves having a sinusoidal oscillation pattern, other nonlinear spatially varying patterns are used in other embodiments. These nonlinear patterns may be oscillating and may have a period oscillation that is constant or that varies, In some embodiments, the pattern may have sharper turns upward and downward along the y direction or left and right along the x direction and may for example, be characterized more as "zig-zag^*. The turns may. however, be smooth in some embodiments. Random and pseudo random patterns are also possible.

[0002303 Non-linear rows and columns of pyramids result as shown in Figure 22E. As with certain of ihe other embodiments disclosed herein, the pyramids have an upright {''everted*) or inverted configuration. The grooves 164a and 164b, however, may be replaced with ridges to produce an array of inverted pyramids. In other modified embodiments, a composite array is formed by combining the patterns of more than two arrays of noniinear light recycling films, and/or a composite array is formed by combining the patterns of two nonlinear light recycling films at an angle other than 90". Use of a nonlinear Sight recycling film 160 to collect Sight from a larger spatiai portion of the light guide advantageously provides the spatial Sight moduiator with more uniform illumination. In embodiments wherein the spatial light modulator includes a plurality of pixels, uniform illumination advantageously reduces Moire effects, as described above. For example, in one configuration the non-linear non- intersecting elongate features (e.g., ridges or grooves) in a nonlinear iight recycling film 180 oscillate an integral number of periods within each pixel of the spaiiai light modulator. While dϊffusers are opttonaϊSy used to cause light to diffuse the iight from the light guide, use of strong {that is, high angle) diffusers can disadvantageous^ reduce the gain of the backlit display, increase the thickness of the backiit display, and/or increase the cost of the backlit display. For example, in certain embodiments use of one or more of the nonlinear light recycling films 160 illustrated in Figure 22A provides similar advantages as compared to use of a diffuser with one or more linear light recycling films 22a, such as that illustrated in Figure 2A, In a modified embodiment, a diffuser is formed on a surface of the Sight recycling film 180 without any microstructures, such as the second surface 106 illustrated in Figure 22B.

[000232] For example, in one embodiment a first backiit dispiay inciudes two perpendicularly-crossed nonlinear light recycling films 160 of Figure 22A and a 3^* diffuser. A second backlit display includes two perpendicularly-crossed linear light recycling fiims 22a of Figure 2A and a 10* diffuser. With other parameters held constant, such as the light guide dimensions, the first backlit dispiay produces a higher gain (1.77} than the second backiit display (1J2). Even in modified embodiments wherein use of a nonlinear light recycling fiirn 180 yields iittle or no gain advantage as compared to iinear light recycling films, the nonlinear light recycling ftim are still configurable to coliect light from a larger spatial area of the iight guide, thus helping to reduce Moire effects.

[000233] in certain embodiments, the modified light recyciing Him 112 iiiustrated in Figure 3A is further modified such that linear non-intersecting elongate features that define the Him (for example, the parallel ridges 108 and grooves 110 of Figure 3A) have a varying elevation over the surface of the film. For example, Figure 23A is a top surface view {in the xy plane) of a modified iight recycling film 170 having a plurality of linear elongate features with varying elevation, which are indicated by lines 172. The lines 172 are rotated with respect to the x axis by an angle α. in one example, this modified light recycling film 170 may comprise a plurality of linear grooves that follow along the lines 172. The depth or pitch of the grooves may vary or oscillate, In embodiments where the angle of the sloping sidewalls of the groove remains constant, the width of the groove wilt increase with deeper groove depths. Accordingly, as the groove varies in depth, so too wilt the groove vary in width. In other embodiments, the angle of the sloping sidewalls of the groove may vary, in another example, the modified Sight recycling fiSm 170 may comprise a plurality of ridges of varying or oscillating height. A more generalized description applicable to both ridges and grooves is provided below with continued reference to Figure 23A,

As illustrated by Figure 23A, the elevation of the surface of the modified light recycling film 170 is indicated by broken contour lines 174 which are drawn at a constant elevation with respect to a reference or bass, and elevation extrema along the lines 172 are located at points 175, Between adjacent lines 172 is a constant-elevation nonlinear interface path 178. The interface path 176 oscillates laterally between the surrounding lines 172. depending on the relative elevation difference between the elongate features at a selected point along the interface path 176. For example, the intetface path 176 is relatively far from a selected line 172 at a point adjacent an extrema 175 along the selected line 172, Figure 23B is a top surface view of a modified light recycling film 170' wherein the lines 172 &re rotated with respect to the x axis by an angle o'. In this example, the angle a illustrated In Figure 23A is equal to the angle α' illustrated in Figure 23B.

[000235J In Figures 23A and 23B. the exfrema 175 positioned along adjacent lines 172 are out of phase with respect to each other by an angle less than 180°. In embodiments wherein respective extrema positioned along adjacent lines 172 are in phase with each other, the array of extrema points 175 will form a rectangular array, as schematically illustrated in Figure 23C. In embodiments wherein extrema positioned along adjacent lines 172 are out of phase with respect to each other by an angle of 180°, a selected extrema point 175 will be positioned between two extrema points on an adjacent line 172, as schematically illustrated in Figure 23D, [0002363 In an example embodiment, the sets of elongate features used to form the modified light recycling films 170. 170' illustrated in Figures 23A and 238 are combined to form a composite modified light recycling film. Figure 23E schematically illustrates a two-array composite modified light recyciing film 170" formed by combining the elongate features in Figure 23A represented by lines 172 and rotated by an angle α with the elongate features in Figure 238 represented by lines 172 and rotated by an angle a\ In Figure 23E, line 172a is parallel to the array of lines corresponding to modified light recycling film 170, and line 172b is parallel to the array of microstructure lines corresponding to the modified iight recycling film 170'. The elevation of the surface of the modified iight recycling film 170" is indicated by broken contour lines 174 which are drawn at a constant elevation with respect to a base. As described herein, the lines 172 correspond to varying-heighi ridges and varying-height grooves in alternative embodiments.

Figure 23F is a top surface view (in the xy plane} of a modified iight recycling film 178 having a plurality of iinear parallel elongate features with varying elevation, which are indicated by iines 172. Lines 172 are parallel with respect to the x axis. In the embodiment illustrated in Figure 23F, the elongate features have an elevation that varies sinusoidally. In other embodiments the elongate features have an elevation that varies according to another pattern, such as a triangle pattern {that is, linearly decreasing for a selected segment, followed by linearly decreasing for a selected segment). In stiil other embodiments, the elongate features have an elevation that varies according to a pattern of connected arc segments,

£0002383 in Figure 23F, the eievation of the surface of the modified iight recycling film 178 is indicated by contour lines 179 which are drawn at a constant elevation with respect to a base, and eievation extrema along the lines 172 are located at points 175. in the example embodiment illustrated in Figure 23F, the extrema points 175 are 180° out of phase, as schematically illustrated in Figure 23D. Figure 23G is a perspective view of the modified iight recycling film 178 of Figure 23F₁ wherein the extrema points 175 correspond to elevation minima. This configuration is referred to as inverted. Figure 23H is a perspective view of the modified iight recycling film 178 of Figure 23F₁ wherein the extrema points 175 correspond to elevation maxima. This configuration is referred to as upright or "everted". Additional contour fines 179 are also shown.

[000239] Figure 23I is a plot of intensity versus angle in the vertical and horizontal directions (parallel to the x and y axes, respectively) of the transmitted light distribution for the light recycling film 178 illustrated in Figure 23F. in certain embodiments, the light recycling film 178 is advantageously capable of collecting light from a larger spatiai area of the iight guide 18, as compared to certain other nonlinear composite iight recycling films disclosed herein (for example, see Figures 22E anά 23E). Thus, the configuration illustrated in Figure 23F advantageous!;/ reduces Moire patterns in certain embodiments, and, because it includes a single set of parallel linear elongate features, may simplify fabrication in certain embodiments. Furthermore, the gain of the modified 5 light recycling film 178 of Figure 23F is comparable to certain other nonlinear composite light recycling films disclosed herein (for example, see Figures 22E &nd 23E).

[000240] In some embodiments, height variations may be introduced that are small For exampie, the ridges may vary in height by an amount small compared to the height 0 of the ridge.

[000241} The structures anύ methods described herein may be used in a wide variety of applications. The light recycling films may be used tn displays such as LCD televisions, monitors, handheld devices such as persona! digital assistants (PDAs), cell phones, watches, etc._s portable computers such as notebooks, navigational devices β such as GPS and instrumentation, including automobile, nautical, and aviation instrumentation, as well as stadium and roadside screens. A wide variety of other display applications are also possible. The light recycling structures may be used in lighting applications including down lighting, display fighting, architectural Sighting, traffic and airport lighting etc. The applications should not be limited to these. The structures 0 and methods described herein may be employed in medical, industrial, military, and consumer applications as we!! as in other areas.

[000242J In certain embodiments, at least a portion of the elongate features that comprise the light recycling film are provided with a modified surface profile. One example of such a modified surface profile is achieved by exposing a master used in S the formation of the light recycling fiim to a stress. The stress can be generated by the application of energy, chemicals, machining or pressure to a portion of the master. For exampie, energy can be applied as either electrical energy or focused heat, such as by an infrared laser or a pencil tip torch. For instance, focused laser energy can be used to melt a very small amount of materia! in a localized area of the master, 0 [GQG243J Use of chemicals to stress the surface of the master are particularly useful in embodiments wherein the master comprises a plastic material. For example, in such embodiments, application of a solvent on the master causes the film surface to pucker slightly, thereby affecting the orientation of the elongate features.

£0002443 Machining techniques are useful for altering the interna! mechanical stress of the master, and are particularly useful in embodiments wherein the master includes internal stresses. An example machining technique Is rnicro-driliing, wherein small amounts of material are removed from the master to slightly relieve locai mechanical stresses. This stress relieve creates minute distortion of the elongate features.

[GQ02453 Application of mechanical pressure can be used to produce localised distension involving the movement of material In the master, such as by contact of the master against projecting blunt fingers. Such localized distension preserves material mass while creating stress, and can be provided by a mechanical device, such as by a finger roller that is roiled against the master,

[000246] The light recycling film may be formed from the master, in certain embodiments, the master may be used form intermediate components such as copies or replicas that may be used to form the iight recycling film. In some embodiments, the master may be a copy itseif. A wide variety of such processing variations are possible.

[000247] Regardless of the method of application, stress can be used to introduce an aberration in the structure of the features that comprise the light recycling fiim, wherein the aberration affects the transmission of light through the feature. In one embodiment, the aberration is introduced in only a selected spatiai area of the light recycling film. Additional information regarding use of stress to modify the elongate features of the iight recycling fiim is provided in U.S. Patent 6,871,966.

[0002483 *n a modified embodiment, the elongate features have multiple faceted edges. For example, Figure 24 illustrates a partial cross-sectional profile of a light recycling film 180 that includes a pair of elongate features 182 that have multiple faceted edges. In particular, in the embodiment illustrated in Figure 24, the elongate features 182 inciude a first pair of faceted edges 184 and a second pair of faceted edges 186. In other embodiments, the elongate features 182 include more than two pairs of faceted edges. Elongate features having multiple faceted edges can be formed, for example, using a cutter with faceted edges corresponding to the shape of the features to be formed. in another modified embodiment, the tip of the cutting tool used to form the elongate grooves defines a straight groove root parallel to the xy plane, but the cutting tool osculates within a plane containing the groove root. That is, the cutting too! oscillates to and fro parallel to the direction of the groove. The attitude of the tool with respect to the substrate is controlled as a function of the position of the cutting tool along the groove, in this mode of operation, the center of oscillation is the tip of the cutting tool. This mode produces a groove having groove walls that undulate such that the included groove angie expands and contracts along the length of the groove. As the cutting tool oscillates in accordance with this embodiment, the included groove angle witi vary across the surface of the fiim. Additional information regarding certain methods wherein the cutting too) is oscillated are provided in U.S. Patent 6,984,047 entitled "Retroreftector with controlled divergence made by the method of groove undulation," issued January 10, 2006,

{$002503 ⁱⁿ another modified embodiment, the tip of the cutting tool used to form the elongate grooves defines a straight, constant elevation groove root, while the cutting tool oscillates within planes perpendicular to the groove root. That is, the cutting tool oscillates transverse to the direction of the groove, in this method, while the magnitude of the groove angle itself will not change along the length of the groove, the progressive oscillation the cutting tool along the groove will result in variations in the angle between the xy plane and the groove wails. Additional information regarding embodiments that may work are provided in U.S. Patent 6,984,047 entitled "Retroreftector with controlled divergence made by the method of groove undulation," issued January 10, 2006, subsection "Fourth Mode" (paragraph [0068]),

[000251J A wide range of variations in design are possibie. Each of the parameters described herein may be varied and various combinations of different features may be used in different embodiments. Still other variations are possible. For example, the on- axis gain may depend on the index of refraction of the light recycling film. Accordingly, the index of refraction of the light recycling film may be tuned as desired. Similarly, in cases where two or more sheets are employed, each of the sheets need not have the same index of refraction. Stiii other parameters, including those described herein as well as others may be varied. Additionally, features may be added, features may be removed, mύ different arrangements and configurations may also be used, include those yet to be devised. Other variations are also possible. Except for the description of flipped compound prism structures in Figures 1B and 1C, the foregoing description has focused on optical control structures consisting of fight recycling structures. Due to similarities between light recycling structures anύ flipped compound prism structures, the descriptions of at isast the following ones of the above-described figures concerning Sight recycling structures apply as well to flipped compound prism structures:

Figures;

1A₁

2C_S 3E, 3F₅ 3P, 3T, 3D,

4F, 4H, 4G,

6F₁

7A,

8A_: 8B₁ SC, SD, 13A, 13B.

UA, 14B₁

1SA-D,

16A-C (although Figure 16B relative to Figure 18C shows the effect of the diffuser 20b of Figure 1 B), 18 (although a different shaped item 62 could apply to a flipped compound prism structure),

19A-C, 2O₁

22C-D, and 231.

[000263] Various aspects of flipped compound prism structures are now considered in connection with Figures 25A-27, Figures 25A and 25B contrast angular luminance as between an optica! apparatus tacking an optica! control film and an optical apparatus including a flipped compound prism structure, Sn particular, the luminance plot of Figure 25A is associated with an optical apparatus 1Od including a light guide 18a, a reflector 16, and a spatial light modulator 24, such as an LCD. Light guide 18a may be wedge shaped (i.e., tapered) in the illustrated horizontal direction, and typically has an array of extractors 19 for extracting iight from the light guide. The extractors 19 can be embodied as shown in Figure 26A as rows or columns 1Sa, 1Sb. 19c, etc., of non-elongated extractors. Each of the extractors in the foregoing rows or columns comprises a truncated cone-shaped recess in the bottom of the light guide 18a, Figure 26B shows another typical arrangement of rows or columns of extractors 19d, 19e and 191 Each of the foregoing rows or cαfumns comprises an elongated, singie groove that may extend fully across a iight guide,

10002553 Returning to Figure 2SA, in which the optical apparatus 10d lacks an optical control film such as a flipped compound prism structure, light rays 200 are shown. The light rays 200 exit the light guide 18 at an angle sυbstantialiy different from the normal direction to the spatial iight modulator 24_< and, without passing through an optical control film, reaches the spatial light modulator at the same angle. The luminance plot in Figure 2SA shows point 202 as a point of maximum luminance. The point 202 can be seen as angled by more than about 30^* from normal to the spatial light modulator 24, (The foregoing norma! direction is indicated in the associated luminance plot at x ~ 0° and y ~ O⁰,) Bearing in mind that normal to the spatiai light modulator 24 is the direction—in colloquial terms— of looking straight into an LCD, for instance, it is usually desirable for the maximum luminance to be closer to the normal direction. There are some applications, such as in avionic and automotive displays where the maximum luminance may be shifted slightly away for the normal direction.

[GG0258J Figure 25B shows an optica! apparatus 10e that includes a flipped compound prism structure 22c for redirecting light rays 210a as described beiow. The optical apparatus 10e desirably produces the highest luminance at point 206 in the luminance plot, which is at or near normal to a spatial light modulator 24. As a result, a person viewing the spatial light modulator 24 would see the brightest image looking directly at the spatial light modulator. Notably, the relative on-axis (i.e.. in the norma! direction) intensity for Figure 258 is approximately 1500 compared to approximately 400 for Figure 25A. Jacking fSipped compound prism structure 22c. Beneficially, the amplitude line 208 exhibits an oval shape. Such an oval shape of high luminance is beneficial, since a viewer of a spatiai light modulator would see a bright Image when viewing at relatively wide horizontal angles, such as when viewing an LCD screen of a television, for instance, while walking around a room containing the LCD screen. On the other hand, the restricted vertical extent of viewing a bright image usually does not present a problem, because such viewing would be associated with rising above and below the LCD screen, which occurs much less than with walking horizontally around a room. [000257J The desired oval shape of luminance amplitude line 208 in Figure 258 can typicaliy be obtained as follows. At ieast first and second pluralities of non- intersecting elongate features of a flipped compound prism structure are suitably angled with respect to each other. Exemplary first and second pluralities comprise the elongate features shown in Figure 3A in light recycling film 112 and the elongate features shown In Figure 38 in light recycling film 114, which features are angled with respect to each others in the composite film 116 of Figure 3C. When using an array of non-elongated Sight guide extractors such as shown in Figure 26A, angiing of the mentioned pluralities of features at about 60° or less usuaiiy can result in obtaining a desirably oval-shaped amplitude line, like line 208 in Figure 25B, for obtaining the benefits mentioned above. Angling at less than 30' produces significantly oval shaped amplitude Sines. Angfing at about 60 can result in a more circular shaped amplitude line, in any event, angling at less than about 90° is generally preferred, and angling at about 80^cor iess is more preferred for obtaining a higher peak luminance than at 90°.

[0002583 in Figure 25B, the flipped compound prism structure 22c receives light rays 210a and redirects such light rays as rays 210b, which projects in a normal direction to the spatial tight modulator 24. As mentioned above, details of a flipped compound prism structure are already described above with respect to Sight recycling films. The data for the luminance plot in Figure 25B relates to prisms formed of planar surfaces and having a vertex angle of 60^β, [000259] Whereas Figures 25A and Figure 258 show light rays 200 and 210a emanating from a light guide, the flipped compound prism structures of the invention more generally may receive light from other light sources, In particular, the invention applies as weiS to a source of light having a peak luminance shifted from a normal direction to a spatiai fight modulator by more than about 30^*. Such distribution of light may be provided, for instance, by an array of LSDs (not shown) having maximum luminance at angles shifted considerably from a direction normal to the textured major surface of the flipped compound prism structure, [000280] Flipped compound prism structures have the advantage of providing multiple views into a light guide (or other iight source} and improving uniformity of light transmission to a spatial iight modulator by reducing correlation of the light with extractor structure in the iight guide (or artifacts in a light source). This is similar to the basic principle shown in Figure SA for light recycling structures. With a flipped compound prism structure, iight from a light guide, for instance, typically will nominally couple into a prism face (e,g,, 105, Figure 2B) and then totally internaliy reflect towards a spatiai iight modulator on another prism face. Flipped compound prism structures also have the advantage of being able to use different pitches and therefore reduce nonuniformities that result from correlation of a pixel structure of a spatial light moduiator. This is sinriar to the structure shown in Figure 3V where the pattern of pyramid centers 192 is rotated with respect to the cut angies of the iight recycling structure of α = 5^α and - α - -5°',

[000261] it is aiso useful to unduiaie the elongated prism features of the ffipped compound prism structures, such as shown in various figures above, such as Figure 2SA. Figure 23A shows undulations that may be (i) paraiiei to textured major surface 22d of Figure 1B, normal to such surface, or (Hi) a combination of (i) and (Si), Such undulating further reduces Moire patterns by reducing the periodicity of the textured surface.

£0002623 Referring again to Figure 28, an additional way to reduce Moire patterns is to vary adjacent cross-sectional shapes of adjacent elongated features of a flipped compound prism structure- Variation Sn cross-sectional shape may result, for instance, from varying one or more of pitch p, angles v or φ, or height Δt, or other shape-inducing factors in the elongate features of a flipped compound prism structure, By way of example, Figures 3X, 3Y_> and 3Z show variations in pitch as between adjacent elongate features, which have associated cross-seciionai shapes (not shown) that correspondingiy vary. Variation of the mentioned factors creates a randomization light passing through the flipped compound prism structure. This tends to mask or obscure artifacts in a flipped compound prism structure as well as to mask or obscure correlated structures as between a light guide and a spatial light modulator. In some embodiments, variations in pitch or height of the cross-sectional shapes allows the randomization and/or rotation of residua! textured surface patterns without having to rotate the elongated prism features. Moreover, variations of the mentioned shape- inducing factors ϊn an optica! control structure having intersecting elongate features — as in Figures 3X_> 3Y, and 3Z— is particiilary pronounced compared with similar variations in an optica! control film lacking such intersecting eiongate features.

[000263] Figure 27 shows a preferred modification of a flipped compound prism structure 22e, in which prisms 22f have their apexes cut off to form fiat surfaces 22g. This allows flat surfaces 22g to be "wetted" to light guide 18, for improving the efficiency of coupling Sight from the light guide to the flipped compound prism structure 22e. This feature of ''wetting" can be faciiitated with the use of refractive index- matching materials such as pressure-sensitive adhesives or index-matching epoxtes. Wetting can also be facilitated where the flat surfaces 22g are bonded to the light guide 18.

JG0Q264J While the foregoing detailed description discloses several embodiments of the present invention, it should be understood that this disclosure is illustrative only &nά is not limiting of the present invention, U should be appreciated that the specific configurations and operations disclosed can differ from those described above, and that the methods described herein can be used in contexts other than light recycling films.

Claims

WHAT IS CLAIMED IS:

1. An optical apparatus comprising: a) a Sight guide; b) an optical member comprising opticaiiy iraπsmissive material and having a textured major surface receiving light from said light guide; the textured surface comprising first and second pluralities of non-intersecting elongate features; the pluralities being angled with respect to each by iess than about 90^* and intersecting each other so as to form total internal reflection structures; and c) a spatial light modulator with rows or columns of pixels for receiving light from the optical member at a major surface.

2. The opticas apparatus of Claim 1_» wherein the piuraiities are angled with respect to each by about 60^* or less.

3. The optical apparatus of Ciaim 1 , wherein the pluralities are angled with respect to each other by about 30° or less.

4. The optica! apparatus of Claim 1. wherein the first and second pluralities of non- intersecting elongate features have different pitches.

5. The optica! apparatus of Ciaim 4, wherein the first and second piυraiities of non- intersecting elongate features have pitches that are sufficiently different from each other that the textured surface has an appearance that is rotated more than 15 ° from rows or columns of pixels of the spatial light modulator.

8, The optical apparatus of Ciaim 1 , wherein: a) more than one elongate feature of the first plurality of features each has a cross-sectϊonal shape that varies from an adjacent cross-sectional shape of an adjacent one of another elongate feature of the first plurality of features; and b) the cross-sectional shapes being taken along largest dimension of the associated elongate feature,

7. The optical apparatus of Claim 6, wherein said more than one elongate feature comprises at least 40 percent of the elongate features of lhe first plurality of features.

8, The optica! apparatus of Claim 6, wherein said first-mentioned cross-sectional shape varies from the second-mentioned cross-sectionai shape in pitch or height

9. The optical apparatus of Claim S, wherein: a) more than one elongate feature of the second plurality of features each has a cross-sectional shape that varies from an adjacent cross-sectional shape of an adjacent one of another elongate feature of the second plurality of features; and b) the cross-sectional shapes being taken along largest dimension of the associated efongate feature.

10. The optical apparatus of Claim 5, wherein: a) the first and second pluralities of non-intersecting elongate features are angied at plus anό minus about 5° from the direction of the rows or columns of pixels of the spatial light modulator; and b) the pitches of said first &nύ second pluralities are respectively about 31 end about 41 μm, respectively.

11. The optical apparatus of Claim 1, further comprising a diffuser situated between the optical member and the spatial Sight modulator; the diffuser being combined with the optica! member.

12. The optical apparatus of Claim 11, wherein the diffuser asymmetrically scatters light passing therethrough.

13. The optical apparatus of Claim 1, wherein the non-intersecting elongate features comprise non-linear features.

14. The optica! apparatus of Claim 13, wherein the non-linear features undulate across said textured major surface of the optica! member.

15. The optical apparatus of Claim 13, wherein the non-linear features undulate in a direction normal to said textured major surface of the optica! member.

16. The optical apparatus of Claim 1, wherein said pluralities intersect each other only once.

17. The optical apparatus of Claim 1, wherein: a) the first and second pluralities of features have peak sections facing the light ^■Quiάe; and b) the peak sections being flattened and wetted to the light guide.

18. The optical apparatus of Claim 1 , wherein: a) the light guide has an array of extractors to extract light from the Sight guide; said array comprising a plurality of rows or columns of extractors; and b) said first and second pluralities of features being angled with respect to the δ rows or columns of extractors.

19. The optica! apparatus of Claim 1, wherein the textured surface comprises more than two pluraiities of non-intersecting elongate features; said pluralities being angled with respect to each other and intersecting each other so as to form total internal reflection structures. 0

20. An optical apparatus comprising: a) a source of Sight; b) an optical member comprising optically fransmissive material and having a textured major surface receiving light from said source of light; the textured surface comprising first and second pluralities of non-intersecting elongate δ features; said pluralities being angled with respect to each other and intersecting each other so as to form total internal reflection structures; and c) a spatial light modulator with rows or columns of pixels for receiving light from the optical member at a major surface; and ύ) said source of light providing, to said optical member, light having a peak 0 iuminance that is shifted from a normal direction to said textured major surface by more than about 30".

21. The optical apparatus of Claim 20\ wherein said source of light comprises: a) a light emitter; and b) a light guide with rows or columns of extractors of light, for receiving light from 5 the light emitter.