US20090009995A1

US20090009995A1 - optical architecture

Info

Publication number: US20090009995A1
Application number: US11/856,004
Authority: US
Inventors: Regis Grasser; Jim Dunphy
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 2007-07-02
Filing date: 2007-09-14
Publication date: 2009-01-08
Also published as: US7817323B2; US20090009837A1

Abstract

An optical beam-shaping unit comprises a fly-eye lens for modifying light beams into modified light beams with desired profiles. The optical beam-shaping unit is especially useful in modifying collimated light from solid-state illuminators, such as laser sources.

Description

CROSS-REFERENCE TO RELATED CASES

This US patent application claims priority under 119(e) from co-pending U.S. provisional patent application Ser. No. 60/947,618 filed Jul. 2, 2007, attorney docket number TI-64796PS, the subject matter being incorporated herein by reference in its entirety.
This US patent application also claims priority under 119(e) from co-pending U.S. provisional patent application Ser. No. 60/953,409 filed Aug. 1, 2007, attorney docket number TI-64992PS, the subject matter being incorporated herein by reference in its entirety.
This US patent application is related to US patent application “An Optical Structure and an Imaging System Using the Same,” attorney docket number TI-65026 and “An Optical Architecture having a Rotating Polygon for Use in Imaging Systems” to Destain, attorney docket number TI-64796, both filed on the same day as this application; and the subject matter of each being incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE DISCLOSURE

The technical field of this disclosure relates to the art of optical devices; and more particularly to the art of optical devices and optical architectures for use in imaging systems.

BACKGROUND OF THE DISCLOSURE

In recent years, solid-state light illuminators, such as LASERs and light-emitting-diodes (LEDs), and other narrow-banded light illuminators capable of producing phase-coherent light, such as wavelength specific plasma lamps, have drawn significant attention as alternative light sources to traditional light sources, such as arc lamps, for use in imaging systems, especially imaging systems employing light valves each comprising an array of individually addressable pixels, due to many advantages, such as compact size, greater durability, longer operating life, and lower power consumption.
Regardless of the widely embraced superior properties of solid-state illuminators over traditional light sources, it is however difficult to optically couple solid-state illuminators with light valves. For example, it is difficult to generate a far-field illumination area with uniform illumination intensity at the light valve location using solid-state or narrow-banded light illuminators because the illumination light from the solid-state illuminators and most narrow-banded illuminators are highly collimated as compared to the light from traditional illuminators.
An approach to illuminate light valves with solid-state illuminators, especially lasers, is to use a rotating polygonal mirror, as set forth in US patent application “An Optical Structure and an Imaging System Using the Same,” attorney docket number TI-65026, the subject matter of which is incorporated herein by reference in its entirety. In a simple example, beams of color laser light are directed to reflective facets of a rotating polygonal mirror structure. The moving reflective facets reflect the laser beams and generate illumination fields on the pixel array of the light valve. By moving the illumination field across the light valve pixel array, light valve pixels can be illuminated sequentially. The light valve modulates the laser beams based on the desired image; and the modulated laser beams are directed to a screen to produce the desired image.
In order to obtain high quality images on the screen, the illumination fields illuminating the light valve are expected to have specific profiles, such as elongated strips along the rows (or columns) of the pixel array; and uniform intensity distribution in the direction perpendicular to the scanning/moving direction. The expected profiles are not always ready for commercialized solid-state illuminators, such as laser sources.
Single laser source often has limited output power that is incapable of generating produced images with satisfactory brightness. When multiple laser sources are used for providing satisfactory output power, the multiple laser sources are often arranged in an array for the laser sources emitting substantially the same color light. Due to the highly collimated light beam, the illumination field of the laser array on the light valve pixel array is not uniform enough, resulting in poor quality images on the screen.
Therefore, what is desired is an optical device or an optical architecture that is capable of shaping light beams from solid-state illuminators, especially from laser sources to generate illumination field with pre-defined profiles.

SUMMARY

In one example, an illumination system is disclosed herein. The system comprises: an array of laser sources capable of emitting light of substantially the same wavelength; and a beam-shaping unit positioned for modifying the light comprising: a fly-eye lens comprising a first array of lenslets.
In another example, an illumination system is disclosed herein. The system comprises: an array illuminators capable of emitting light of substantially the same wavelength; a beam-shaping unit positioned for modifying the light comprising: a fly-eye lens comprising a first array of lenslets.
In yet another example, an illumination system is disclosed herein. The system comprises: a light source providing light; a beam-shaping unit positioned for modifying the light comprising: a fly-eye lens comprising a first array of lenslets; and a scanning-mechanism comprising a number of reflective facets for reflecting the modified light onto a target.
In still yet another example, an imaging system is disclosed herein. The system comprises: a light source providing light; a beam-shaping unit comprising an array of unidirectional lenslets that are optically positioned for modifying the light from the light source; and a light valve for causing the light to propagate toward or away from a display target so as to produce an image on the display target.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates an exemplary display system comprising an illumination system that is capable of illuminating the target by causing an illumination field on the target and moving the illumination field across the target continuously so as to illuminate the entire image area on the target;

FIG. 2 a schematically illustrates an illumination field of the light emitting from the illuminators and before the beam-shaping device of the display system in FIG. 1;

FIG. 2 b schematically illustrates an illumination field of the illumination light after the beam-shaping device of the display system in FIG. 1;

FIG. 2 c schematically illustrates an exemplary intensity distribution of the illumination field on FIG. 2 b along one direction;

FIG. 2 d schematically illustrates an exemplary intensity distribution of the illumination field on FIG. 2 b along another direction;

FIG. 2 e schematically demonstrates an illumination field that is generated on the light valve of the display system in FIG. 1; and used for scanning the light valve to illuminate the light valve;

FIG. 3 schematically illustrates an exemplary optical architecture of the beam-shaping device in FIG. 1;

FIG. 4 schematically illustrates a perspective view of an exemplary fly-eye optical element that can be used in the optical architecture FIG. 3;

FIG. 5 a schematically illustrates a top view of another exemplary fly-eye optical element that can be used in the optical architecture in FIG. 3;

FIG. 5 b schematically illustrates a cross-sectional view of the fly-eye optical element in FIG. 5 a;

FIG. 5 c schematically illustrates a cross-sectional view of another fly-eye optical element;

FIG. 6 schematically illustrates an exemplary display system in which a beam-shaping device of this disclosure can be implemented;

FIG. 7 schematically illustrates the illumination field at the entrance of the optical architecture in FIG. 6;

FIGS. 8 a and 8 b schematically illustrate near-field and far-field illumination profiles at a location between the polygonal mirror structure and the screen in the optical architecture in FIG. 6;

FIGS. 9 a and 9 b schematically illustrate near-field and far-field illumination profiles at the light valve location in the optical architecture in FIG. 6;

FIG. 10 schematically illustrates an exemplar rear-projection system having an optical structure of this disclosure; and

FIG. 11 schematically illustrates an exemplary micromirror device that can be used in the light valve of the imaging system illustrated in FIG. 1 a.

DETAILED DESCRIPTION OF SELECTED EXAMPLES

In the following, the beam-shaping optical device and display systems using the same will be discussed with selected examples. However, it will be appreciated by those skilled in the art that the following discussion is for demonstration purpose, and should not be interpreted as a limitation. Other variations within the scope of this disclosure are also applicable. For example, other imaging systems, such as systems for storing information of image (e.g. 2D images or holographic images) in image storing mediums are also applicable.
Referring to the drawings, FIG. 1 schematically illustrates an exemplary display system employing a beam-shaping device capable of tailoring light from the illuminators into modified light with desired profiles. In this example, display system 100 comprises illuminator unit 102 providing light beams, beam-shaping unit 112 for tailoring the light beams. Rotating polygon 116 comprising reflective facets receives modified light beams, projects the modified light beams onto light valve to generate an illumination field, and causing the illumination field to scan the light valve so as to illuminating the individually addressable pixels of the light valve.
In order to provide light beams with sufficient power corresponding to the desired brightness of produced images on the screen, illuminator unit 102 comprises multiple solid-state illuminators, such as lasers. The illuminators are arranged into arrays based on the color of the light emitted by the illuminators. Specifically, illuminators emitting light of substantially the same color (characteristic wavelength) can be arranged in one straight line; and illuminators emitting different color of light beams can be arranged in separate lines, while the separate lines can be substantially parallel. As illustrated in FIG. 1, illuminator arrays 104, 106, and 108 each comprise illuminators emitting substantially the same color light beam, such as red, green, blue, white, yellow, cyan, magenta, and any desired combinations thereof.
Each illuminator array may comprise any suitable number of illuminators. However, it is preferred that the each array comprises a number of illuminators such that the total output power of the illuminators in the array satisfies the desired brightness of the produced images on the screen.
Illumination unit 102 may comprise any suitable numbers of arrays of illuminators with each array corresponding to a particular color based on the desired illumination scheme for illuminating the light valve and for producing the desired image. For example, the illumination unit (102) may comprise illuminators capable of emitting light of primary colors with a primary color being defined as a color that is not a combination of other colors, such as red, green, and blue colors. Alternatively, the illumination unit may comprise illuminators capable of emitting light of secondary colors with a secondary color being defined as a color that is a combination of primary colors, such as while, yellow, cyan, magenta, and other colors.
In one example, the illuminators of the illuminator unit (102) can be laser sources, such as those of NECSEL™ technologies from Novalux, Inc. and solid-state lasers from Collinear Inc. and Coherent Inc. The lasers, when used in the illuminator unit (104), are preferred to have a light power of from 50 mW or higher per color used in the system for producing the image (e.g. the red, green, or the blue color), such as 1 W or higher per color, and more preferably 3 W or higher per color. When multiple laser sources are used for providing sufficient light intensity, it is preferred, though not required, that 5 or more, 10 or more, 17 or more, 24 or more, laser sources (or independent laser units), are used for each color light.
When the illuminators are laser sources or the like that emit collimated light, light beams 110 from the illuminator unit (102) has non-uniform intensity distributions, as schematically illustrated in FIG. 2 a.
Referring to FIG. 2 a, the near-field of the light beams (110) before the beam-shaping unit (112) is schematically illustrated therein. The illumination pattern in the near-field corresponds to the arrangement of the illuminators in the illuminator unit (102). Light beams of the same color in the near-field is not uniform along the illuminator array (e.g. along the Y direction).
To modify the non-uniform light beams such that the light beams of substantially the same color are uniform along the array (e.g. along the Y direction), the non-uniform light beams from the illuminator unit (102) is directed to beam-shaping unit 112, as schematically illustrated in FIG. 1. The beam-shaping unit (112) modifies incident light beams 110 into modified light beams 114 with a desired illumination profile, as schematically illustrated in FIG. 2 b through FIG. 2 d.
FIG. 2 b schematically illustrates the near-field of the light beams after the beam-shaping unit (112). Corresponding to the special arrangement of the illuminators, color light beams from the illuminators in the same array are modified into a substantially illumination strip. Specifically, color illumination field 114 comprises color strips 130, 128, 126, and blank sub-fields (e.g. 132) between color strips. Color strips 130, 128, and 126 each extend along the direction of the illuminator array (e.g. the Y direction). Each color strip has a desired intensity distribution as schematically illustrated in FIG. 2 c and FIG. 2 d.
FIG. 2 c schematically illustrates an intensity distribution of the color strips along the Y direction (the length of the color strips) as defined in FIG. 2 a. In this example, each color strip has a uniform intensity distribution along the length of the color strip. Even shown in FIG. 2 c that all color strips have substantially the same maximum intensity I_Y, this is one of many possible examples. In other examples, different color strips may have different maximum intensity along the length (Y direction) depending upon the specific illuminators used. Regardless of different illuminators used, each color strip preferably has a substantially uniform intensity distribution along the length of the color strip.
Each color strip may have any suitable intensity distributions along the width (X direction) of the color strip, such as uniform, Gaussian, top-hat, triangle, and random distributions. FIG. 2 d schematically illustrates an exemplary Gaussian intensity distribution of the color strips along the width of the color strips. In this example, all color strips have substantially the same maximum intensity I_X. In other examples, different color strips may have different maximum intensity along the width (X direction) depending upon the specific illuminators used. In some examples, different color strips may have different of intensity-distribution forms along the width of the color strips. For example, one or more color strips may have a random intensity distribution; while another one or more color strips may have a uniform or a Gaussian intensity distribution along the width of the color strips; and different color strips may or many not have the same maximum intensity along the width.
Referring back to FIG. 1, the modified light beams (such as that illustrated in FIG. 2 b) output from beam-shaping unit can then be used for illuminating the light valve. In one example, the modified light beams are directed to reflective facets of rotating polygon 116. As the polygon rotating, the reflective facets (e.g. reflective facet 118) of the polygon moves relative to the propagation path of the modified light beams. As a consequence, the incident light angle (the angle between the incident light beams and the normal direction of the reflective facet on which the light beams are incident) changes with the rotation of the polygon. The reflected light beams from each reflective facet change propagation paths and sweep across a special angle (referred to as scanning angle). By aligning the light valve (122) to the area corresponding to the scanning angle, the reflected light beams from the polygon are capable of moving across the light valve to sequentially illuminating the light valve pixels. The light valve pixels being illuminated modulate the incident light beam(s) based on image data of the desired image to be produced. The modulated light can then be directed towards the screen to display the desired image.
As a way of example, FIG. 2 e schematically demonstrates the movement of the illumination field (114) comprising the color strips of FIG. 2 b across the pixel array of the light valve. The dimension of the pixel array can be characterized by width W₀and height H_o. In one example, W₀can be 480 pixels or more, 600 pixels or more, 720 pixels or more, 768 pixels or more, 1024 pixels or more, 1050 pixels or more, 1200 pixels or more, with each pixel having a characteristic length of 200 microns or less, 150 microns or less, 100 microns or less, 50 microns or less, 20 microns or less, 14 microns or less, 8 microns or less. H₀can be 640 pixels or more, 800 pixels or more, 1024 pixels or more, 1280 pixels or more, 1400 pixels or more, 1600 pixels or more, and 1920 pixels or more, with each pixel having a characteristic width of 200 microns or less, 150 microns or less, 100 microns or less, 50 microns or less, 20 microns or less, 14 microns or less, 8 microns or less. In another example, H can be from 5 mm to 30 mm, such as from 10 mm to 20 mm. The total width of the color strips including the blank subfields (if provided) is s. s can be a value such that the ratio of s to H₀is 1/500 or higher, such as 1/200 or higher, 1/100 or higher, 1/50 or higher, 1/20 or higher, or 1/10 or higher, and preferably less than ½.
In one example, the color strips can be equally spaced. The total width s can be substantially equal to the height H₀of the pixel array. For N color strips that are equally spaced with blank sub-fields, the total width s of the N sub-fields and the blank sub-fields is preferably H₀×(1−(½×N)) with H_o. A blank sub-field between two consecutive color strips may be designed to provide a time period during which light valve pixels of a display system can be updated. In particular, the size (width) of a blank sub-field can be determined based on the minimum update (state-switching) time period of light valve pixels.
It is noted that FIG. 2 a through FIG. 2 e illustrate only one of many possible configurations. Other configurations are also applicable. For example, the illumination field (114) may comprise any suitable numbers of color strips and blank fields; and the illumination field may also comprise multiple color strips of the same color. In one example, the illumination field may comprise color strips of R-G-B, R-G-B-W, R-R-G-G-B-B, R-R-G-G-B-B-W, R-G-B-Y-C-M, R-G-B-Y-C-M-W, with R, G, B, W, Y, C, and M respectively representing red, green, blue, white, yellow, cyan, and magenta colors. Blank sub-fields can be distributed between colored sub-fields in any desired ways if provided.
The beam-shaping unit (112) in FIG. 1 can be implemented in many ways. In one example, the beam-shaping unit can employ a fly-eye lens, as schematically illustrated in FIG. 3.
Referring to FIG. 3, beam-shaping unit 112 comprises fly-eye lens 134 and field lens 140. The front side lenslets (136) is distanced L₁from the backside lenslets in the fly-eye lens. The field lens (140) is disposed such that target (e.g. pixel array of the light valve) is substantially at a focal plane of the field lens (140); and the focal length of the field lens (140) is L₂.
The fly-eye lens (134) can be a unidirectional lenticular array, which corresponds to the fact that homogenization of the light beams from each illuminator array is expected along the length (length of the array). FIG. 4 schematically illustrates a perspective view of the front side of the unidirectional fly-eye lens (134).
Referring to FIG. 4, front side 136 of the fly-eye lens comprises an array of lenslets arranged along the Y direction; and each lenslet uniformly extends along the X direction so as to uniformly homogenize the incident light beams in the Y direction, while substantially maintain the illumination profile of the incident light in the X direction. The uniformity can be further improved by selecting aspheric lenslets so as to avoid spherical aberration caused non-uniformities. In particular, low power lenslets, which exhibit low spherical aberration, can be employed.
The total number of lenslets in each front and back sides of the fly-eye lens is preferably (though not required) equal to or larger than the number of illuminators in each illuminator array. For example, the number of lenslets of the front side (or the backside) can be equal to or larger than K×N, wherein K is an integer equal to or larger than 1, such as a number between 5 and 10; and N is the number of illuminators in each illuminator array, or can be the maximum number of illuminators in an illuminator array when the illuminator arrays have different numbers of illuminators.
The center-to-center distance between adjacent lenslet is defined as pitch of the lenslet, P_lens. The lenslet pitch P_lensis preferably (though not required) equal to or smaller than P_illum/K, wherein P_illumis the center-to-center distance between adjacent illuminators in each illuminator array (referred to as the pitch of an illuminator array), or the minimum pitch of the illuminator arrays. With this configuration, each illuminator can be associated with at least one lenslet in substantially the same way.
The distance G_lensbetween adjacent illuminator arrays can be selected based on the desired size (e.g. width) of the blank-field between the color strips, such as black-field 132 between color strips 130 and 128 as illustrated in FIG. 2 b.
It is noted that FIG. 4 is for demonstration purpose, and should not be interpreted as a limitation. Even though 8 lenslets are illustrated corresponding to 8 illuminators in each illuminator array, this is only an example. In many other configurations, the front/back side of the fly-eye lens each may have any suitable number of lenslets corresponding to the numbers(s) of the illuminators in the illuminator arrays, as discussed above. The illuminator arrays can be arrayed such that illuminators of the same position in different arrays are aligned along a straight line (e.g. along the X direction), as illustrated in FIG. 4. In other examples, the illuminator arrays can be arranged in many other suitable ways, in which instances, the lenslets of the fly-eye lens can be extended according to the arrangements of the illuminator arrays.
The front side and backside are disposed in the fly-eye lens such that the front side and the backside are substantially images to each other; and the lenslets of the front side (backside) are substantially at the focal planes of the lenslets of the backside (front side), as illustrated in FIG. 3. Referring again to FIG. 3, each lenslet in the front side corresponds to a lenslet on the backside. The distance L₁between the front side and the backside, and the field lens (140) can be arranged such that the magnification (defined as ratio of L₂/L₁) of the fly-eye architecture in FIG. 3 is equal to or larger than 2, such as 3 or more, 5 or more, 10 or more, such as from 10 to 30. Larger magnification can be of great importance in minimizing divergence of the color strips, for example, divergence along the width of the color strips.
Incident light beams converging at the front lenslets, such as lenslet 148 a, are directed to the corresponding lenslet (148 b) at the backside; and are collimated as parallel light beams after the lenslets at the backside of the fly-eye lens. The collimated light beams pass through field lens 140; and are converged at the pixel array of light valve 146.
Collimated light beams incident to the lenslets at the front side, such light beams incident to lenslet 150 a, are converged to the corresponding lenslets at the backside, such as lenslet 150 b. The lenslets (e.g. lenslet 150 b) pass the light beams to the field lens (140) that expands the light beams into an illumination strip on the light valve (146) with the illumination strip corresponding to the desired color strip. As a consequence, the fly-eye lens integrates incident light beams at the light valve; and forms a homogenized illumination strip (color strip) at the light valve with the desired profile.
When illuminators are lasers or the like, the light beams emitted thereof are phase-coherent, which may cause unwanted diffraction, interference fringes, and/or speckle noises. The unwanted diffraction, interference fringes, and/or speckle noises can degrade line uniformity; and are desired to be minimized or eliminated.
Speckle noises can be minimized or eliminated using a movable optical diffuser (e.g. diffuser 142 in FIG. 3). The optical diffuser can be any suitable optical diffusers, such as surface optical diffusers, bulk optical diffusers, and engineered optical diffusers. The optical diffuser can be moved along many suitable directions, and more preferably along the direction of the illumination strip where the uniform intensity distribution is desired, such as along the length of the illumination strip. The movement preferably has a frequency equal to or higher than the flick frequency of viewer's eyes such that the movement is not perceptible by viewer's eyes. Other moving frequencies lower than the flick frequencies are also applicable; while prevent from being observed by viewer's eyes. This arises from the fact that the illumination field on the light valve moves across the light valve pixel array; and such movement can reduce or eliminate the speckles or unwanted artifacts caused by the movements of the optical diffuser.
Diffractive patterns, such as interference fringes, may exist. This is due to the fact that light beams from single illuminator may pass propagates along different paths (e.g. passing through different lenslets of the fly-eye); and converging at one location. The interference fringes can be eliminated or reduced by adding a bi-directional feature to the fly-eye lens, as schematically illustrated in FIG. 5 a and FIG. 5 b.
Referring to FIG. 5 a, a top view of a bi-directional fly-eye lens is illustrated. Fly-eye lens 154 in this example can be the same as the fly-eye lens 136 in FIG. 4 except that each lenslet extends in the X direction to form a two-dimensional structure, instead of a one-dimensional straight line as illustrated in FIG. 4. The two dimensional structure of each lenslet in the X-Y plane can be any suitable forms, such as smooth and continuous curves and zigzagged line-segments. It is preferred, though not required, that the lenslets are substantially parallel, regardless the different structures.
A cross-sectional view of the fly-eye lens is schematically illustrated in FIG. 5 b. Referring to FIG. 5 b, the lenslets in the Y-Z plane each have an aspheric profile; and the curved top surfaces of the lenslets can be continuous. In other examples, the curved top surfaces of the lenslets can be interconnected by other features, such as a flat segment, as schematically illustrated in FIG. 5 c.
Examples of the beam-shaping unit as discussed above can be implemented in a wide range of systems and in many ways. As an example, a light beam-shaping unit can be implemented in a display system; while the display system can be configured as a front-screen projector, a rear-screen projector, a rear-projection TV, or many other imaging systems. FIG. 6 schematically illustrates a display system that employs a beam-shaping unit as discussed above.
Referring to FIG. 6, the display system comprises illuminator unit 102, beam-shaping unit 112, optical element 157 that can be an f-theta lens comprising lenses 158 and 160, rotating polygonal mirror 116 that comprises a number of reflective facets (e.g. reflective facet 118), optical diffuser 142, optical elements 164 and 172, a dichroic filter stack that comprises dichroic filters 166, 168, and 170, and light valve 122 that comprises an array of individually addressable pixels.
The illuminator unit (102) comprises illuminator arrays as discussed above with reference to FIG. 1. In this example, the illuminator unit (102) comprises laser sources capable of emitting red, green, and blue laser light beams. Laser sources emitting substantially the same color light beams are arranged in a line (array); and different lines of illuminators are arranged in parallel. In other examples, the illuminator unit may comprise any suitable illuminators. For example, the illuminator unit may comprise illuminators capable of emitting red (R)—green (G)—blue (B) light beams, R-G-B-white (W) light beams, R-R-G-G-B-B with multiple illuminator arrays emitting the same color light beams, R-R-G-G-B-B-W, R-G-B-Y (yellow)-C (cyan)-M (magenta), R-G-B-Y-C-M-W.
The light valve pixels can be any suitable pixels, such as reflective and deflectable micromirror devices and liquid-crystal-on-silicon (LCOS) cells, examples of which will be discussed afterwards with reference to FIG. 11.
Rotating polygonal mirror 116 comprises a number N of reflective facets that can be specular or non-specular reflective, wherein N is an integer larger than 2. The polygonal mirror is aligned to the color light beams such that, when rotating along a rotation axis passing through the major axis (center) of the polygon, the reflective facets sequentially intercept the light beams and reflecting the light beams onto the light valve. For simplicity purpose, only one reflective facet 118 is illustrated, but the polygonal mirror may have any suitable number of reflective facets, as discussed above. It is noted that the reflective polygonal mirror can comprise any desired materials. For example, the reflective polygonal mirror can comprise a plastic material with the surfaces coated by a light reflective material, such as aluminum, gold, silver, or many other suitable materials. For moving/rotating the polygonal mirror, the polygonal mirror can be mounted to a driving mechanism, such as a motor.
Light beams from the illuminator unit (102) pass through beam-shaping unit 112. The beam-shaping unit modifies the light beams into modified light beams 114 that may comprise red, green, and blue color light beams 126, 128, and 130, respectively. FIG. 7 schematically illustrates the near-field illumination pattern of the modified light beams after the beam-shaping unit, such as at plane at plane 156.
Referring to FIG. 7, the near-field illumination pattern comprises illumination fields 126, 128, and 130 respectively corresponding to the light emitted from illuminator arrays.
Referring again to FIG. 6, the illumination light beams (126, 128, and 130) are incident to a reflective facet, such as facet 118, of rotating polygonal mirror 116 through f-theta lenses 157 that comprises lens 158 and 160. The light beams (126, 128, and 130) respectively generate illumination fields (e.g. color strips) on the reflective facet (118).
The illumination fields (e.g. color strips) on the reflective facet (118) are spatially separated as illustrated in FIG. 6. The light beams are then reflected by the reflective facet; and passes through the f-theta lens (157). The near field and far field illumination pattern of the reflected light beams after the f-theta lenses (157) at plane 162 are schematically illustrated in FIG. 8 a and FIG. 8 b.
Referring to FIG. 8 a, illumination fields 126 a, 128 a, and 130 a correspond to the illumination fields 126, 128, and 130 in FIG. 7, respectively. However, the illumination fields 126, 128, and 130 in FIG. 7 are spatially static; while illumination fields 126 a, 128 a, and 130 a in FIG. 8 a are spatially moving during to the rotation of the reflective facet of the rotating polygonal mirror.
Referring to FIG. 8 b, the far-field illumination pattern of the reflected light from the facet of the polygonal mirror comprises circular illumination fields 190, 192, and 194 corresponding to the near field illumination fields 126 a, 128 a, and 130 a, respectively. The far field illumination fields 190, 192, and 194 are spatially separated.
Referring again to FIG. 6, the reflected light after f- theta lenses 154 and 156 is directed to movable diffuser 142. The movable diffuser can be any suitable optical diffusers, such as bulk- or surface engineered optical diffusers for spreading each color light so as to substantially fill the pupil of the projection optical element at far field. The movement of the optical diffuser can be accomplished by attaching the optical diffuser to a moving mechanism that is capable of rotating and/or vibrating the optical diffuser.
The reflected light after the optical diffuser (142) is projected to a stack of dichroic filters 166, 168, and 170 through relay optical element 164; wherein the stack of dichroic filters is substantially disposed at the far field of relay optical element 164. The stack of dichroic filters comprises dichroic filters corresponding to the wavelengths (colors) of the light beams. For example, when red, green, and blue color light beams are used, the dichroic filters can be red, green, and blue dichroic filters. In another example, one of the dichroic filters can be replaced by a folding mirror, such as a specular or non-specular folding mirror. The dichroic filters are disposed such that the reflected light of different colors from the dichroic filters are overlapped at far field, such as at the location of the screen, on which the modulated light from the light valve (174) are projected. An exemplary far field illumination pattern of the reflected light after the stack of dichroic filters is schematically illustrated in FIG. 9 b.
Referring to FIG. 9 b, the far-field illumination pattern, such as the illumination pattern at the pupil of the projection lens that projects the modulated light from the light valve, is substantially a uniform field 188.
Referring again to FIG. 6, the reflected light after the stack of dichroic filters is incident onto the light valve (122) through relay lens 172. At the light valve, the reflected light from the stack of dichroic filters forms the desired illumination fields, as schematically illustrated in FIG. 9 a.
The generated illumination fields as illustrated in FIG. 9 move along the desired direction (e.g. along the column) across the light valve pixels so as to sequentially illuminating the light valve pixels. The light valve pixels modulate the illumination light in each illumination field according to image data (e.g. bitplane data) associated with the desired image to be produced on the screen. The modulated light from the light valve pixels is then projected to the screen of the system to present the desired image.
It is noted that relay lenses 164 and 172 can be of great importance in improving image quality. This arises from the fact that the illumination fields generated by the light beams of different colors on each reflective facet are spatially separated, thereby are not telecentric. On the other hand, in order to obtain a high duty cycle on the polygonal mirror, it is expected that each illumination field generated by a color light has a small angular divergence. The above two problems together may cause a non-uniform pupil filling of the projection lens that is often provided for projecting the modulated light from the light valve onto the screen of the display system. This problem can be solved by the relay lens (164 and 172), as well as a moving diffuser and a stack of dichroic filters.
With the above optical architecture, the illumination light of different colors from the illuminators can be projected to the light valve simultaneously, which in turn allows for the illuminators being operated continuously. Because all light from the illuminators can arrive at the screen simultaneously with substantially no light being blocked, the brightness of the produced images on the screen can be significantly larger than that in existing display systems wherein light of different colors are sequentially incident to the light valve and only one color light is incident to the light valve at a time.
As a way of example, FIG. 10 schematically illustrates an exemplary rear-projection system, such as a rear-projection TV that employs an optical architecture as discussed above.
Referring to FIG. 10, the rear-projection system (190) comprises block unit 144 for providing illumination light. The block unit (144) can be the same as that discussed above with reference to FIG. 6. The illumination light from the block unit 144 is incident to light valve 174 and illuminates the pixels of the light valve (174) in a way as discussed above with reference to FIG. 6. The light valve pixels modulate the incident light according to image data (e.g. bitplane data) derived from the desired image to be produced. The modulated light is then directed to a folding mirror (192) through optical element 196 that spreads the modulated light from the light valve across the reflecting area of the folding mirror (192). The folding mirror projects the modulated light onto a translucent screen (194) so as to present the desired image on the translucent screen.
As discussed above, the light valve may comprise any suitable type of pixels, one of which is reflective and deflectable micromirror devices. FIG. 11 schematically illustrates an exemplary reflective and deflectable micromirror device.
Referring to FIG. 11, the micromirror device comprises substrate layer 222 in which substrate 224 is provided. Substrate 224 can be any suitable substrates, such as semiconductor substrates, on which electronic circuits (e.g. circuits 226) can be formed for controlling the state of the micromirror device.
Formed on substrate layer 222 can be electrode pad layer 216 that comprises electrode pad 218 and other features, such as electronic connection pad 220 that electrically connects the underlying electronic circuits to the above deformable hinge and mirror plate. Hinge layer 206 is formed on the electrode pad layer (216). The hinge layer comprises deformable hinge 208 (e.g. a torsion hinge) held by hinge arm 210 that is supported above the substrate by hinge arm posts. Raised addressing electrodes, such as electrode 212 is formed in the hinge layer (206) for electrostatically deflecting the above mirror plate. Other features, such as stopper 214 a and 214 b each being a spring tip, can be formed in the hinge layer (206). Mirror plate layer 202, which comprises reflective mirror plate 204 attached to the deformable hinge by a mirror post, is formed on the hinge layer (206).
FIG. 11 schematically illustrates one of many possible micromirror devices. In other examples, the micromirror device may comprise a light transmissive substrate, such as glass, quartz, and sapphire, and a semiconductor substrate formed thereon an electronic circuit. The light transmissive substrate and the semiconductor substrate are disposed proximate to each other leaving a vertical gap therebetween. A reflective mirror plate is formed and disposed within the gap between the light transmissive and semiconductor substrates. In another example, the reflective mirror plate can be in the same plane of the light transmissive substrate and derived from the light transmissive substrate.
It will be appreciated by those of skill in the art that a new and useful optical architecture having an optical scanning mechanism for causing an illumination field on a target and moving the illumination field across the target has been described herein. In view of the many possible embodiments, however, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of what is claimed. Those of skill in the art will recognize that the illustrated embodiments can be modified in arrangement and detail. Therefore, the devices and methods as described herein contemplate all such embodiments as may come within the scope of the following claims and equivalents thereof.

Claims

1. An illumination system, comprising:

an array of laser sources capable of emitting light of substantially the same wavelength; and

a beam-shaping unit positioned for modifying the light comprising:

a fly-eye lens comprising a first array of lenslets.

2. The system of claim 1, wherein the first array of lenslets are positioned at a front side of the fly-eye lens further comprises a second array of lenslets at a backside of the fly-eye lens

3. The system of claim 1, further comprising:

a field lens disposed after the fly-eye lens and the array of laser sources along a propagation path of the light.

4. The system of claim 1, wherein each laser source is associated with at least one of the lenslets of the first array of lenslets.

5. The system of claim 1, wherein the lenslets of the first array are aspheric lenslets.

6. The system of claim 1, wherein the fly-eye lens is a unidirectional fly-eye lens or a bi-directional fly-eye lens.

7. The system of claim 1, further comprising an optical diffuser disposed on a propagation path of the light.

8. The system of claim 1, wherein the modified beam has a substantially rectangular illumination field with a substantially uniform intensity along a length of the illumination field.

9. The system of claim 1, further comprising a polygon having a number of reflective facets, wherein the polygon is positioned after the array of laser sources and the beam-shaping unit and along a propagation path of the light.

10. The system of claim 9, further comprising: a f-theta lens positioned between the beam-shaping unit and the polygon.

11. The system of claim 1 is in a display system that is configured as a projector; and wherein said array of laser sources further comprises a laser source that is capable of emitting a laser beam having a wavelength different from said same wavelength.

12. The system of claim 11, wherein the projector is a front projector or rear-front-projector.

13. An illumination system, comprising:

an array illuminators capable of emitting light of substantially the same wavelength;

a beam-shaping unit positioned for modifying the light comprising:

a fly-eye lens comprising a first array of lenslets.

14. The system of claim 13, wherein the illuminators are laser sources; and wherein each laser source is associated with at least one of the lenslets of the first array of lenslets.

15. The system of claim 13, wherein the fly-eye lens is a unidirectional or a bi-directional fly-eye lens.

16. The system of claim 13 is in a display system that is configured as a projector.

17. An illumination system, comprising:

a light source providing light;

a beam-shaping unit positioned for modifying the light comprising:

a fly-eye lens comprising a first array of lenslets; and

a scanning-mechanism comprising a number of reflective facets for reflecting the modified light onto a target.

18. The system of claim 17, wherein the scanning mechanism comprises a polygon having a number of reflective facets.

19. The system of claim 18, wherein the light source comprises an array of illuminators that are laser sources capable of emitting light of substantially the same wavelength.

20. The system of claim 19, wherein each laser source is associated with at least one of the lenslets of the first array of lenslets.