WO2005020590A1

WO2005020590A1 - Anaglyphic 3d glasses comprising polarisation dependent color filters

Info

Publication number: WO2005020590A1
Application number: PCT/DK2004/000564
Authority: WO
Inventors: Steen Svendstorp Krener-Iversen
Original assignee: Sirius Large Format Aps
Priority date: 2003-08-25
Filing date: 2004-08-24
Publication date: 2005-03-03

Abstract

Anaglyphic glasses for viewing stereoscopic 3D images on displays emitting polarised light, comprising polarisation dependent color filters, present advantages in viewing comfort, filter precision and degree of freedom in glasses design, over traditional anaglyphic glasses. Further, an alternating color filter version presents advantages over traditional shutter glasses.

Description

Anaglyphic 3D glasses comprising polarisation dependent color filters.

Background of the invention

Anaglyphic viewing systems comprising anaglyphic glasses with differently colored filters, provide observers of a printed, displayed or projected image to observe a stereoscopic 3-D image.

Anaglyphic images are generally produced by encoding a left eye image in a first color and a right eye image in a second color, then superimposing the left eye image and the right eye image. The first color normally contains one or two elementary colors, and the second color normally contains the remaining complementary color. Often used color pairs are for example red/cyan and blue/ yellow.

The anaglyphic viewing filters decodes the image by transmitting the first color and the second color selectively, so that the left eye image is filtered out by a viewing filter in front of the left eye(s) of the observer(s), and the right eye image is filtered out by a viewing filter in front of the right eye(s) of the observer(s), so that the left eye image and the right eye image are respectively directed to the left and the right eye(s) of the observer(s).

Anaglyphic glasses using colored viewing filters are well known in the stereoscopic art, and even though other systems that provide higher image quality and viewing comfort has been developed, anaglyphic 3D is still widely used because of it's versatility; it can be used in a vast number of viewing situations and with a large number of display types. The image quality, noticeably color reproduction, has been improved in recent developments, but some disadvantages of anaglyphic glasses still remains.

One disadvantage is, that when viewing anything else than the anaglyphic image itself, -wearing the glasses, such as the surroundings of the display, other viewers in an auditorium, a presenter, a computer keyboard, a written manual, a medical journal, etc., the viewing comfort is reduced by the colored filters, which gives a distraction to the overall experience. As a consequence, viewers tend to put on and off the glasses when viewing 3D images and when observing other things, not an effective solution providing high comfort.

Another disadvantage is, that the differently colored glasses bring to mind associations of the "funny glasses" used by audiences for the '50es Hollywood 3-D movies, which is not desirable in many professional applications. An airport security officer inspecting 3-D X-ray images, for example, may prefer glasses in a more neutral or professional looking style.

A suggested solution to the above was demonstrated by Benton in the early 80'es. A viewing system comprising a dichroic polarising sheet, mounted on the front of a crt display, allowing conventional anaglyphic images to be viewed with glasses with orthogonally oriented polarisers. This enables viewing the surroundings with higher comfort. A disadvantage is though, that it requires the described, for an average user relatively complicated, modification of the display.

Yet another disadvantage of current types of anaglyphic glasses, is, that if the highest quality 3-D experience is desired, relatively expensive viewing filters for the glasses are needed. While cheap filters can be produced, the quality of the 3-D experience is less using these, especially when watching a big, projected image, and where light gain is of importance.

For example in cinema applications, the highest quality 3-D experience on the big cinema screen is requested, while it is still desirable for practical, economical and promotional reasons to use low cost glasses, that the audiences are allowed to bring home, where they can use them for watching the movie's website etc., a viewing situation where the requirements regarding the filters characteristics are more relaxed.

Further relevant techniques are described in DE 100 23 512 A1 , FR 2 532 503 A1, JP 6-214193 A, US 4,559,556 A, EP 0 477 882 A2 and US 2001/0048505 A1 , to which reference is made and which US patents are hereby incorporated in the present specification by reference.

The object of the invention is to overcome the above-described disadvantages.

Description of the invention

Figure 1 illustrates a first embodiment of the present invention, an anaglyphic viewing system, comprising a first color filter 1 and a second color filter 2, where the first color filter and the second color filter are polarisation dependent, so that the first color filter and the second color filter appear essentially neutral or uncolored, or so that first color filter and the second color filter essentially has the same color, when viewing non polarised light transmitted through the first color filter and the second color filter, but differently colored when viewing polarized light transmitted through the first color filter and the second color filter, and a display that emits polarised light 3. An observer 4 observes the display, with the first color filter located in front of the left eye and the second color filter located in front of the right eye. The display 3 may be an LCD display, which emits polarised light. The color of the transmitted polarised light through the first color filter and the second color filter, respectively, may be any color pair that is suitable for anaglyphic viewing. Color pairs suitable for anaglyphic viewing are well known in the art, and include red/cyan and green/ magenta color pairs. An especially advantageous color pair for anaglyphic viewing is the blue/amber color pair, commercialised under the trademark "ColorCode 3-D", as described by Svend E. B. Sørensen et al. in US patent 6,687,003, which is hereby incorporated in the present specification by reference.

Figure 2 shows a possible configuration of the first color filter 1 and the second color filter 2. The first and second color filters may comprise polarisers 5a and 5b, located towards the face of an observer 4 and wavelength dependent retarders 6a and 6b, that rotates the polarisation direction of transmitted light dependent on the wavelength, located in front of the polarisers, to the side towards the display. The retarders 6a and 6b may be identical, and the polarisers 5a and 5b may be oriented, so there is a difference in their polarisation axis, thereby causing a different transmission spectrum of the color filter 1 and the color filter 2. The difference angle between the axis of polarisers 5a and 5b may be 90 degrees. The retarders 6a and 6b may be of type "Red/Cyan ColorSelect" or "Blue/Yellow" ColorSelect from ColorLink Inc, Colorado. Alternatively or additionally, the retarders 6a and 6b may have different characteristics, thereby causing a different transmission spectrum for polarised light of color filters 1 and 2. The retarder 6a may have specifications as defined by Fig. 7. Fig. 7 illustrates a possible transmission spectrum of the retarder 6a through parallel polarisers. The retarder 6b may have specifications as defined by Fig. 8. Fig. 8 illustrates a possible transmission spectrum of the polariser 6b through parallel polarisers.

The first color filter may comprise a first polariser 5a and a first wavelength dependent wave retarder 6a, and the second color filter may comprise a second polariser 5b and a second wavelength dependent wave retarder 6b, the first and second polarisers 5a and 5b located towards the face of an observer 4, and the first and second wavelength dependent retarders 6a and 6b, located in front of the polariser, to the side towards the display,

The retarder 6a and the retarder 6b may each comprise a retarder stack, consisting of multiple layers of retarders, selected to give the desired overall spectral transmission distribution with respect to wavelength, towards polarised light. The retarder stack may be of the type ColorSelect from ColorLink Inc. Reference is made to US patent number 5,751 ,384, which is hereby included in the specification by reference.

In an alternative configuration, the color filters may comprise dichroic inks printed on coated sheets or other types of dichroic coatings or materials. Reference is made to US Patent number 6,013,123, 4,431 ,265 and 2,298,058 which are hereby included in the specification by reference.

The display 3 of the first embodiment may be a LCD display, which emits polarised light. Fig. 3 illustrates a second embodiment comprising a projector 7, a projection screen 8 which has the characteristic, that it preserves the polarisational direction of reflected light, and a polariser 9, located in the path between the projector 7 and the projection screen 8.

Fig. 5 illustrates an alternative configuration of the second embodiment, where an additional wavelength dependent retarder 14 is comprised, located in the optical path between the polariser 9 and the viewing filters 1 and 2. The retarder 14 may be oriented, so it has its axis of polarisation parallel to the axis of polarisation of the polariser 9. The retarder 14 and the retarders 6a and 6b may be selected or manufactured, so that polarised white light emitted from the projector 7 and transmitted through the polariser 9, the retarder 14 and the retarder 6a and entering polariser 5a in a first plane of polarisation, parallel to the polarisation axis of the polariser 5a, has a first color, hence light transmitted and filtered through the polariser 5a is of the first color, and so that polarised white light emitted from the projector 7 and transmitted through the polariser 9, the retarder 14 and the retarder 6b and entering polariser 5b in a first plane of polarisation, parallel to the polarisation axis of the polariser 5b, has a second color, hence light transmitted and filtered through the polariser 5b is of the second color, where the first and second colors constitute a color pair, suitable for anaglyphic viewing. The first color may be yellow and the second color may be blue. The retarder 14 may be a construction comprising several wavelength dependent retarders, all located in the optical path between the polariser 9 and the viewing filters 1 and 2.

Alternatively or additionally, an additional wavelength dependent retarder 12, located in the optical path between the polariser 9 and the viewing filters 1 and 2, and an additional polariser 13, located in the optical path between the retarder 12 and the viewing filters 1 and 2 may be comprised. In this configuration, the retarders 6A and 6B may still be included but may also be omitted. The polariser 13 may be oriented, so it has its axis of polarisation parallel to the axis of polarisation of the polariser 9. The retarder 12 may be selected or manufactured, so the transmission spectrum for polarised light emitted from the projector 7 and transmitted through the polariser 9, the retarder 12 and the polariser 13 results in an improved color balance or reduced stereoscopic crosstalk, or both, of the perceived image observed through the viewing filters 1 and 2 by the observer 4. The retarder 12 may be a ColorCorrect DN3 filter or a ColorCorrect DN7 filter from ColorLink Inc., Colorado, or it may be a retarder having different characteristics. The retarder 12 may be a construction comprising several wavelength dependent retarders, all located in the optical path between the polariser 9 and the polariser 13.

The advantage of the above configuration of the second embodiment is, that in situations, where viewing filters for many observers are required, the precision in meeting the design spectra for the first and the second color can be improved, without having to add complexity to the viewing filters, but adding only one set of more complex retarders located in front of the projector. The same viewing filters may still be used in the first embodiment and the first configuration of the second embodiment, although with slightly less precision in meeting the desired color pair.

In an alternative and especially advantageous configuration of the second embodiment, the polariser 9 is eliminated and the projector 7 is of a type, that emits polarised light due to polarising means inside the projector. The polarising means may comprise polarising filters or polarising beam splitters, such as often used in LCD projectors.

The emitted light from commercially available LCD projectors often has different polarisation directions for different wavelengths. It is understood, that this must be taken into account when selecting or manufacturing the retarder 14, the retarder 9 and the retarders 6a and 6b as described above. Many projectors have a first polarisation direction for red and blue light and a second polarisation direction for green light, orthogonal to the first polarisation direction. The retarder 12 may be a construction comprising a Green/Magenta ColorSelect retarder or a Magenta/Green ColorSelect retarder from ColorLink Inc., Colorado. The retarder 14 may be a construction comprising a Green/Magenta ColorSelect retarder or a Magenta/Green ColorSelect retarder from ColorLink Inc., Colorado.

Fig. 4 illustrates a third and especially advantageous embodiment, in which electrically controlled means 10 for rotating the polarisational direction of transmitted light in either of two orthogonal directions, is comprised, located in the optical path between the display 3 or the polariser 9 or the projector 7, of the first or the second embodiment and the color filter 1 and the color filter 2, which may be located in a pair of viewing glasses, and synchronized by a synchronisation circuit 11 , with an alternation of the colors being used for encoding of the left eye image and right eye image in the anaglyphic image displayed at the display 3 or projected by the projector 7, so that the left eye image is essentially always filtered out for the left eye of the observer(s) and the right eye image is essentially always filtered out for the right eye of the observer(s). In this embodiment, the retards 6a and 6b may be identical, and the polarisers 5a and 5b may be oriented with orthogonal polarisation axis.

The electrically controlled means of rotating the polarisational direction of transmitted light, may comprise one or more liquid crystal cell(s). The liquid crystal cell(s) may be mounted in the viewing glasses, located in front of the viewing filters or they may be located in front of the projectors exit pupil or in the optical path between the polariser, located in front of the projectors exit pupil, and the projection screen.

The advantage of the third embodiment is, that given a high enough alternation frequency, the viewing filters appear clear, or more specifically as neutral density filters, even when viewing polarised light, due to the human eye's inherent low frequency filtering, caused by retinal latency. Compared to traditional shutter glasses, which alternates between an essentially clear and an essentially opaque state, the alternating color filters will have a lower flicker threshold, above which, the average observer will not experience distracting flicker due to lower contrast difference between the two states.

Fig. 6 illustrates an alternative configuration of the third embodiment, where retarders 12 and 14 and polariser 13 are comprised, their respective purposes and principles of operation being the same as described in the description of the second embodiment. Fig. 7 illustrates a spectral transmission distribution curve of the retarder 6a.

Fig. 8 illustrates a spectral transmission distribution curve of the wavelength retarder 6b.

Fig. 9 illustrates a pair of viewing glasses comprised in an alternative and especially advantageous configuration of the first embodiment. The viewing glasses hold the first color filter 1 and the second color filter 2 in place in front of the observers eyes, and allows for the observer to adjust the glasses for different types of the display 3, having different types of polarisation angle of emitted light, by rotating the first color filter 1 and the second color filter 2 in a synchronised way. Commercially available LCD displays, for example, usually have one of the four polarisation angles 0 degrees, 45 degrees, 90 degrees and 135 degrees.

The viewing glasses comprise a frame 15 and means for rotating the first color filter 1 and the second color filter 2 in a synchronised way, so that the first color filter 1 and the second color filter 2 is always rotated by the same angle, thereby maintaining the same difference in polarisation angle between the first polariser 5a and the second polariser 5b. The difference in polarisation angle between the first polariser 5a and the second polariser 5b may be essentially 90 degrees.

Fig. 10 is a front view of the frame 15 of the alternative configuration of the first embodiment with the color filter 1, the color filter 2 and the means for rotating the first color filter 1 and the second color filter 2.

Fig. 11 is an exploded perspective view of the frame 15 of the alternative configuration of the first embodiment with the color filter 1, the color filter 2 and the means for rotating the first color filter 1 and the second color filter 2.

The means for rotating the first color filter 1 and the second color filter 2 comprises a flexible wire 16 such as a wire made from e.g. nylon or another plastic material. The flexible wire may comprise a finger knob 16a for moving it by hand, thereby rotating the color filter 1 and the color filter 2 in a synchronised rotation. Further, the flexible wire 16 may comprise means for locking it onto the first color filter 1 and means for locking it onto the second color filter 2.

Alternatively, the means for rotating the first color filter 1 and the second color filter 2 may comprise a gearwheel, a rack or a string or any combination hereof. The gearwheel, rack or string may be operated by hand and may comprise means for the observer to move it with his/her fingers. The means for the observer to move it with his/her fingers may comprise a finger knob.

The means for rotating the first color filter 1 and the second color filter 2 may comprise means for locking the rotational position in a number of predetermined positions. The number of predetermined positions may be 4. The predetermined rotational positions may be 0 degrees, 45 degrees, 90 degrees and 135 degrees.

The frame 15 comprises a fold 15c in which the first color filter 1 and the second color filter 2 can rest, and allowing the first color filter 1 and the second color filter 2 to rotate within a range of angles, and further allowing the flexible wire 16 to rest and slide in, as it wraps around the first color filter 1 and the second color filter 2. The range of angles may be from 0 degrees to 135 degrees. Further, the frame 15 may comprise a number of shapes 15a to hold the first color filter 1 and the second color filter 2 in place, not allowing them to leave the frame 15, the shapes 15a also allowing the flexible wire 16 to slide under and wrap around the first color filter 1 and the second color filter 2.

The means for locking the flexible wire 16 onto the first color filter 1 may comprise a convex shape 16c in the flexible wire 16, that can lock into a concave shape 1a in the first color filter 1. The means for locking the flexible wire 16 onto the second color filter 2 may comprise a convex shape 16d in the flexible wire 16 that can lock into a concave shape 1b in the second color filter 2.

The convex shape 16c may be a different shape than the convex shape 16d, so that the convex shape 16c can lock into the concave shape 1a but not into the concave shape 1b, and so that the convex shape 16d can lock into the concave shape 1b but not into the concave shape 1c, thereby making it easy to identify the correct placement of the color filter 1 and the filter 2 during assembly.

Further, the frame 15 may comprise a curved slit 15d, in which the flexible wire 16 can travel from the first color filter 1 to the second color filter 2, holding it in place and not allowing it to leave the frame 15.

Even further, the frame 15 may comprise two shapes 15b, which are located, so they secure, that, even when the flexible wire 16 is moved and wraps and unwraps within the fold 15c, the first color filter 1 can not move farther within the tolerances of the fold 15c, than the convex shape 16c is still locked adequately into the concave shape 1a, and the second color filter 2 can not move farther within the tolerances of the fold 15c, than the convex shape 16d is still locked adequately into the concave shape 1b.

Alternatively, the means 16c for locking the flexible wire 16 onto the first color filter 1 may comprise a concave shape in the flexible wire 16, that can lock into a convex shape in first color filter 1, and the means 16d for locking the flexible wire 16 onto the first color filter 1 may comprise a concave shape in the flexible wire 16 that can lock into a convex shape in first color filter 1.

Further, the first color filter 1 may comprise shapes 1b and the second color filter 2 may comprise shapes 2b for reducing friction, when rotating inside the frame 15 in the fold 15c.

Fig. 12A illustrates a front view of the viewing glasses frame of the alternative configuration of the first embodiment with the color filter 1, the color filter 2 and the means for rotating the first color filter 1 and the second color filter 2, in a first rotational position.

Fig. 12B illustrates a front view of the viewing glasses frame of the alternative configuration of the first embodiment with the color filter 1, the color filter 2 and the means for rotating the first color filter 1 and the second color filter 2, in a second rotational position.

Fig. 12C illustrates a front view of the viewing glasses frame of the alternative configuration of the first embodiment with the color filter 1, the color filter 2 and the means for rotating the first color filter 1 and the second color filter 2, in a third rotational position.

Fig. 12D illustrates a front view of the viewing glasses frame of the alternative configuration of the first embodiment with the color filter 1, the color filter 2 and the means for rotating the first color filter 1 and the second color filter 2, in a fourth rotational position.

Illustrations

Fig. 1 is a perspective view of the first embodiment Fig. 2 is a top view of the first and second color filters Fig. 3 is a top view of the second embodiment Fig. 4 is a top view of the third embodiment Fig. 5 is a top view of an alternative configuration of the second embodiment Fig. 6 is a top view of an alternative configuration of the third embodiment Fig. 7 is a spectral transmission distribution curve of a first wavelength dependent retarder

Fig. 8 is a spectral transmission distribution curve of a second wavelength dependent retarder

Fig. 9 is a perspective view of the glasses comprised in an alternative configuration of the first embodiment.

Fig. 10 is a top view of the glasses comprised in an alternative configuration of the first embodiment. Fig. 11 is an exploded perspective view of the glasses comprised in an alternative configuration of the first embodiment.

Fig. 12A is a front view of the glasses comprised in an alternative configuration of the first embodiment, set to a first polarisation direction. Fig. 12B is a front view of the glasses comprised in an alternative configuration of the first embodiment, set to a second polarisation direction.

Fig. 12C is a front view of the glasses comprised in an alternative configuration of the first embodiment, set to a third polarisation direction.

Fig. 12D is a front view of the glasses comprised in an alternative configuration of the first embodiment, set to a fourth polarisation direction.

Claims

1. An anaglyphic viewing system comprising means of displaying an anaglyphic image with polarised light and viewing filters located in front of each of the observers(s)' eyes, where said viewing filters' color transmissions are dependent of the polarisation of the transmitted light.

2. An anaglyphic viewing system according to claim 1 , where each of said viewing filters comprises a polariser, located at the side facing towards the observer(s), and a color polariser, located at the side facing toward said anaglyphic image, that rotates the polarisational direction of transmitted light at different angles, dependent on the wavelength of said transmitted light.

3. An anaglyphic viewing system according to claim 2, where said color polariser is a wavelength dependent wave retarder filter.

4. An anaglyphic viewing system according to claim 3, where said wavelength dependent wave retarder filter comprises a stack of wave retarder filters.

5. An anaglyphic viewing system according to claims 1 ,2,3 or 4, where said means of displaying an anaglyphic image with polarised light is a LCD display".

6. An anaglyphic viewing system according to claims 1 ,2,3 or 4, where said means of displaying an anaglyphic image with polarised light comprises a projector, a projection screen, that preserved the polarisational direction of reflected light and a second polariser, located in the optical path between said projector and said projection screen.

7. An anaglyphic viewing system according to claims 1 ,2,3 or 4, where said means of displaying an anaglyphic image with polarised light comprises a projector that emits polarised light due to it's internal mode of operation.

8. An anaglyphic viewing system according to claim 7, where said projector is a LCD projector.

9. An anaglyphic viewing system according to claims 7 or 8, where a compensating polarisation filter, that rotates the polarisational direction of transmitted length at different angles, dependent on the wavelength of transmitted light, is included in the optical path between the projector and the polarisers of said viewing filters.

10. An anaglyphic viewing system according to claim 9, where said compensating filter is integrated into said color filters in the viewing filters.

11. An anaglyphic viewing system according to claims 1 to 10, where electrically controlled means of rotating the polarisational direction of transmitted light in either of two orthogonal directions is comprised, located in the optical path between said display or said projector of the first or the second embodiment and said viewing filters, and synchronized with an alternation of the colors being used 4 for encoding of the left eye image and right eye image in the anaglyphic image displayed at said display or projected by said projector, so that said left eye image is essentially always filtered out for the left eye of the observer(s) and the right eye image is essentially always filtered out for the right eye of the observer(s).

12. An anaglyphic viewing system according to claim ii, where said electrically controlled means of rotating the polarisational direction of transmitted light is located in the viewing glasses, in front of the viewing filters.

13. An anaglyphic viewing system according to claim 11 , where said electrically controlled means of rotating the polarisational direction of transmitted light is located in the optical path between said polariser, located in front of said projectors exit pupil, and said projection screen.

14. An anaglyphic viewing system according to claim 11, 12 or 13, where said electrically controlled means of rotating the polarisational direction of transmitted light is a liquid crystal cell.

15. An anaglyphic viewing system according to any of the claims 1 to 14 and comprising any of the features of the viewing system as herein before described and illustrated in the accompanying drawings.