STEREOSCOPIC IMAGING SYSTEMS UTILIZING SOLID-STATE ILLUMINATION AND PASSIVE GLASSES

Abstract

A stereoscopic display system employs narrowband illumination light beams and passive glasses with built-in interference filters. The system is also compatible with multiple viewing functions.

Description

TECHNICAL FIELD

The technical field of the examples to be disclosed in the following sections relates to the art of display systems, and more particularly, to the field of stereoscopic imaging systems using solid-state illumination and passive glasses.

BACKGROUND OF THE INVENTION

Traditional stereoscopic imaging systems for visualization of virtual objects use active shutter glasses and passive polarization glasses. Active shutter glasses incorporate left and right shutters that are synchronized to the sets of images for left and right eyes (left and right images). This approach, however, adds cost and introduces artificial effects, such as flickers as each side of the glasses turns on and off.

Passive glasses work in systems employing polarized light and incorporate left and right polarizers that are typically offset by 90° degrees. Due to the polarization, brightness and optical efficiency can be significantly reduced.

Therefore, there exists a need for cost effective displays capable of reproducing stereoscopic images with high brightness and optical efficiency.

SUMMARY

In an example, a method is disclosed herein. The method comprises: producing first and second light beams that are composed of different numbers of colors; modulating the first and second light beams based upon first and second sets of image data that are respectively derived from first and second sets of images; and passing the modulated first and second light beams through a pair of passive glasses with built-in first and second interference filters for viewing such that the modulated first light beam is capable of passing through and substantially only the first interference filter; and such that the modulated second light beam is capable of passing through and substantially only the second interference filter.

In another example, a system for use in producing a stereoscopic image is disclosed herein. The system comprises: an illumination system capable of producing first and second sets of light beams, wherein the wavelengths of light of the first set are not substantially overlapped with the wavelengths of light of the second set, and wherein the first set light beams comprises a different number of colors than the second light beam; a color processor capable of scaling the colors of the image into a consistent and unique color space; an image engine for re-producing a set of images derived from the stereoscopic image by modulating the light beams based upon the stereoscopic image; and a passive glass with a built-in interference filter for separating the set of images such that different images of the image set can arrive at different eyes of the viewer.

In yet another example, a method is disclosed herein. The method comprises: producing first and second narrowband light beams; modulating the first and second light beams based upon first and second sets of image data that are respectively derived from first and second sets of images; passing the modulated first and second light beams through a pair of passive glasses with built-in first and second interference filters for viewing such that the modulated first light beam is capable of passing through and substantially only the first interference filter; and such that the modulated second light beam is capable of passing through and substantially only the second interference filter; and delivering the re-produced first set of images to a first viewer, and the second set of images to the second viewer for viewing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an exemplary display system;

FIG. 2 is a block diagram showing an exemplary structure of the illumination system in FIG. 1;

FIG. 3a illustrates an exemplary structure of the right light source in FIG.2;

FIG. 3b illustrates an exemplary structure of the left light source in FIG.2;

FIG. 4 illustrates an exemplary stereoscopic imaging method using two primary color triplets generated by the illumination system of FIG. 3a and FIG. 3b with each color triplet having red, green, and blue color;

FIG. 5 illustrates the color space used in the imaging method illustrated in FIG. 4;

FIG. 6a illustrates another exemplary structure of the right light source in FIG.2;

FIG. 6b illustrates another exemplary structure of the left light source in FIG.2;

FIG. 7 illustrates an exemplary stereoscopic imaging method using two primary color triplets generated by the illumination system of FIG. 3a and FIG. 3b with asymmetric number of primary colors for right and left eye imaging;

FIG. 8 illustrates the color space used in the imaging method illustrated in FIG. 7;

FIG. 9 illustrates yet another exemplary stereoscopic display system of the invention which provides independent viewing experience for separate viewers;

FIG. 10 illustrates yet another exemplary stereoscopic display system of the invention which employs multiple image engines for generating stereoscopic images;

FIG. 11 illustrates yet another exemplary stereoscopic display system of the invention which employs multiple image engines for generating stereoscopic images; and

FIG. 12 illustrates yet another exemplary stereoscopic display system of the invention which employs multiple image engines for generating stereoscopic images.

DETAILED DESCRIPTION OF SELECTED EXAMPLES

Examples disclosed herein is a stereoscopic imaging system that uses illumination light with narrowband spectrum to generate stereoscopic images such that the generated images can be visualized using passive glasses, in particular, passive glasses integrated with interference filter technology (Infitech). By narrowband, it is meant that the full-with at half maximum (FWHM) of the light spectrum is 100 nm or less, more preferably 50 nm or less, and 30 nm or less.

Turning to the drawings, FIG. 1 is a diagram schematically illustrates an exemplary stereoscopic display system within the scope of the invention. Stereoscopic imaging system 100 in this particular example comprises illumination system 102, image engine 110, synchronization unit 112, color processor, right lens filter 114, and left lens filter 116.

Illumination system 102 is capable of emitting narrowband illumination light beams with different waveband spectra. Subject to the constraint that the maximum number of allowable light beams with different waveband spectra is determined by the interference characteristics of the Infitech filter of the passive glass, the number of light beams with different waveband spectra can be determined by the desired number of imaging channels with each channel transporting a sequence of images for a certain Infitech filter. As an example shown in the figure, dual-imaging channels, i.e. right image light and left image light, can be provided in compatible with the end right and left lens filters 114 and 116. Image information delivered by the right image light and passed through right lens filter 114 is collected by right eye 118 of the viewer; and image information delivered by the left image light and passed through left lens filter 116 is collected by left eye 120 of the viewer. In other alternatives, more than two imaging channels, and more than two separate illumination light beams with different waveband spectra can be provided, which will be discussed afterwards.

The illumination system may have one or multiple light source units for providing light beams of different spectrums. An example is shown in FIG. 2. Referring to FIG. 2, illumination system 102 comprises right source unit 122 and left source unit 124 for providing illumination light beams for right image channel and left image channels, respectively. In other alternatives, the illumination system may have any suitable number of light source units. Though not required, the solid-state light source units (e.g. 122 and 124) of the illumination system can be composed of solid-state light sources, such as lasers, LEDs, or any other suitable solid-state light sources capable of emitting narrowband light beams. Each light source unit preferably comprises light sources emitting a set of primary colors, such as red, green, and blue. For each color, there can be multiple light sources especially for rendering a desired waveband spectrum. For example, a set of light sources whose spectrums are substantially around one of the primary colors (e.g. red) but are sequentially shifted a small amount (e.g. 5 nm or less) can be used so as to obtain a desired bandwidth with substantially flat top.

In an alternative configuration, the illumination system (102) may have light source(s) not specifically designed for particular imaging channels. In this instance, for example when only one light source unit is provided, Infitech filters can be coupled to the light source unit so as to produce light beams with different (complementary) waveband spectrums. The produced light beams can then be used to deliver image information to the viewer.

Referring again to FIG. 1, the illumination light beams from the illumination system (102) are directed to image engine 110. The image engine can be any suitable devices capable of re-producing images. For example, the image engine may comprise reflective and deflectable micromirror devices, liquid-crystal cells (LCD), or liquid crystal on silicon cells (LCOS). Depending upon different optical configurations, the system can be a front- and rear-projection systems or other display systems, such as backlit displays.

The image engine (110) modulates the incident light beam (or multiple beams) based upon a set of image data derived from the corresponding images. For example, when right and left light beams are sequentially directed to the image engine, image data derived from right and left images (104 and 106) are sequentially delivered to the image engine through color processor 108 for modulating the incident light beams. The right and left images (104 and 106) can be generated by a separate module that is not shown in the figure.

To properly producing desired images, operations of the image engine, light sources of the illumination system, and feeding of the image data of right and left images are desired to be synchronized. For example, during the time periods when right light source is turned on while the left light source is turn off, the right light beams illuminate the image engine. Image data of the right images are fed into the image engine. The image engine then modulated the incident right light beams based on the image data of the right images so as to properly reproduce right images. The re-produced right images after the image engine are projected (e.g. by projection lens) to the passive Infitech glasses. At the passive Infitech glasses, the right images carried by the right light beams are passed through the right lens filter (114) and stopped by the left lens filter (116). Accordingly, only right side eye 118 of the viewer receives right images.

At time periods when the right light source is turned off; and the left light source is turned on, left image data derived from the left images are delivered to the image engine that re-produces left-images based on the left image data. The re-produced image data are then projected to the passive Infitech glasses (e.g. by projection lens); and pass through the left lens filter 116.

By sequentially turning on and off right and left light sources, and feeding image data of right and left images onto the image engine, re-produced right and left images can be sequentially delivered to right and left eyes 118 and 120, thus generating stereoscopic virtual objects. The above synchronization of the light sources, image feeding, and operation of the image engine can be accomplished by synchronization unit 112.

Other than sequentially re-producing right and left images as discussed above, right and left images can be simultaneously produced. In this example, multiple image engines are provided, which will be discussed afterwards with reference to FIG. 10.

As an example, FIG. 3a, FIG. 3b, and FIG. 4 schematically demonstrate exemplary image channels of the display system in FIG. 1 for producing stereoscopic images. As shown in FIG. 3a, right light source unit 122 comprises light sources 126, 128, and 130 for producing narrowband primary colors red, green, and blue, respectively. Left slight source unit 124 of FIG. 3b comprises light sources 132, 134, and 136 for producing another set of primary colors of red, green, and blue, respectively. It is noted that each color of each light source may have multiple light sources with identical spectrum or with small differences in spectrums.

In the top of FIG. 4, dual primary color triplets B_R-G_R-R_R and B_L-G_L-R_L for right imaging are illustrated therein. Each of the primary colors, red, green, blue, comprises substantially non-overlapping wavebands for right and left imaging. Specifically, B_R and B_L lie in the blue color range; G_R and G_L lie in the green color range; and R_R and R_L lie in the red color range. Wavebands B_R, G_R, and R_R form the color triplet for forming right images; and color wavebands B_L, G_L, and R_L form the color triplet for forming left images.

The middle and bottom of FIG. 4, the dual color triplets after the passive Infitech glasses are schematically illustrated. As shown in the middle of FIG. 4, the color triplet B_R-G_R-R_R for the right images is passed through the right lens filter (e.g. 114 in FIG. 1); and the color triplet B_L-G_L-R_L for left images are stopped by the right lens filter. As a result, only the right images carried by the color triplet B_R-G_R-R_R can arrive at the right eye of the viewer after the passive Infitech filter. The color triplet B_L-G_L-R_L for left images is passed through the left Infitech filter but stopped by the right Infitech filter—resulting in only left images arriving at the left side eye of the viewer. The left and right images are then integrated by the viewer's eyes so as to form the virtual stereoscopic object.

FIG. 5 schematically illustrates the color spaces in the color gamut. Blue_right, Green_right, and Red_right represent the saturate colors of the color triplet B_R-G_R-R_R; and together define the color space for the right images, which is represented by the area surrounded by solid line triangle. Blue_left, Green_left, and Red_left represent the saturate colors of the color triplet B_L-G_L-R_L; and together define the color space for the left images, which is represented by the area surrounded by dashed line triangle. This non-uniform color spaces for right and left images may cause annoying visual effect to the viewer, such as color displacement effect. In the example as shown in FIG. 5, the right eye of the viewer may feel that right images are greenish; while the left images are red-ish or blue-ish. In order to maintain a consistent color space for the right and left images perceived by the viewers, a unique color space is defined as illustrated in shaded area in FIG. 5. This unique color space is for both right and left imaging. Input right and left color images are processed (e.g. by color processor 108 in FIG. 1) so as to scale the primary colors of the right and left images into the unique color space by mixing colors. For example, the green color of the right images outside the shaded area can be mixed with an amount of blue and red colors. The red color of the left images when outside the shaded area can be mixed with an amount of green and blue.

As afore mentioned, the illumination light beams may or may not have the same number of primary colors. In particular, a beam of illumination light can be primary color triplet; whereas another beam of illumination light can be color multiplet with more than three colors, such as color tetrad and color quintuplet. FIG. 6a and FIG. 6B schematically illustrate a such example. Referring to FIG. 6a, right light source 138 unit of the illumination system 102 (in FIG. 1) may comprise light sources 126, 128, 130, 140, and 142 for emitting red, green, blue, cyan, and yellow colors. It is noted that cyan and yellow, or any one or more colors of red, green, and blue, in this example, can be replaced by other colors, such as white and magenta. Moreover, other colors, such as white and magenta can be added to the right light source. Left light source unit 124 can be the same as that shown in FIG. 3b, which comprises light sources for red, green, and blue color. Of course, the right light source unit 138 may have less number of light sources or can be the same as that in FIG. 3a; while left light source unit 124 may have more number of light sources.

The spectrums of the colors from the right and left light sources are schematically illustrated in the top plot of FIG. 7. Referring to FIG. 7, the right color quintuplet B_R-C-G_R-Y-R_R for right images and left color triplet B_L-G_L-R_L for left images are illustrated there on the top of the figure. Additional colors cyan and yellow are added to enhance the color and whiteness of the perceived images. The cyan and yellow colors can be generated directly by right light sources, such as solid-state light sources, or can alternatively by mixing colors from red, green, and blue colors (B_R, G_R, and R_R) of the right light sources.

After the passive Infitech glasses as shown in the middle of FIG. 7, B_R, C, G_R, Y, R_R colors are passed through the right lens filter (e.g. 114 in FIG. 1); and the color triplet B_L-G_L-R_L for left images are stopped by the right lens filter. As a result, only the right images carried by the color quintuplet B_R, C, G_R, Y, and R_R can arrive at the right eye of the viewer after the passive Infitech filter. The color triplet B_L-G_L-R_L for left images is passed through the left Infitech filter but stopped by the right Infitech filter—resulting in only left images arriving at the left side eye of the viewer. The left and right images are then integrated by the viewer's eyes so as to form the virtual stereoscopic object.

FIG. 8 is a chromaticity diagram schematically illustrating the color spaces of the quintuplet and triplet colors of FIG. 6a and FIG. 6b. Blue_right, Cyan_Right, Green_right, Yellow_Right, and Red_right represent the saturate colors of the color quintuplet B_R-C-G_R-Y-R_R; and together define the color space for the right images, which is represented by the area surrounded by solid line triangle. Blue_left, Green_left, and Red_left represent the saturate colors of the color triplet B_L-G_L-R_L; and together define the color space for the left images, which is represented by the area surrounded by dashed line triangle. In order to maintain a consistent color space for the right and left images perceived by the viewers, a unique color space can be defined for both right and left imaging. Input right and left color images are processed (e.g. by color processor 108 in FIG. 1) so as to scale the primary colors of the right and left images into the unique color space by mixing colors.

The stereoscopic display systems as described herein are also compatible with multiple viewer function, as shown in FIG. 9. Specifically, the maximum number of different viewers simultaneously experiencing different image contents is determined by the characteristic interference spectrum of the passive Infitech filter and the narrowest characteristic bandwidths of the illumination light beams from the light sources. In this specific example, two imaging channels (corresponding to right and left illumination light beams) are provided by the light source. Accordingly, the system can provide two different (though not necessary) sets of viewing contents to two viewers—image viewer 146 and image viewer 154. In operation, right illumination light carries image set A 160 and delivers image set A to eyes 152 (both right and left sides) of viewer 146 through image A lens filter 150. Light illumination light carries image set B 162 and delivers image set B to eyes 158 (both right and left sides) of viewer 154 through image B lens filter 156, as shown in the figure. In this example, viewers 146 and 154 may not experience stereoscopic imaging. To provide stereoscopic viewing for different viewers (e.g. 146 and 154) with different contents simultaneously, multiple imaging channels are created, as shown in FIG. 10.

Referring to FIG. 10, the illumination system (102) provides multiple illumination light beams L_A^r, L_A^l, L_B^r, and L_B^l, with different wavelength spectrums having substantially no over-laps therebetween. The light beams L_A^r, L_A^l, L_B^r, and L_B^l respectively corresponds to the characteristic interference spectrums of right and left passive Infitech filters on different viewers 146 and 154. Specifically, light beams L_A^r can and substantially only can pass through the right lens filter of viewer 146; while light beams L_A^l can and substantially only can pass through the left lens filter of viewer 146. Light beams L_B^r can and substantially only can pass through the right lens filter of viewer 154; while light beams L_B^l can and substantially only can pass through the left lens filter of viewer 154. Image contents are divided into groups for different viewers; and the image contents for each viewer are divided into right and left images for left and right side eyes of the specific viewer.

In operation, the image engine can modulate each of the light beams L_A^r, L_A^l, L_B^r, and L_B^l sequentially in any desired orders, but is synchronized with the input images. For example, the image engine can re-produce right and left images for viewers 146 and then re-produce left and right images for viewer 154. In this specific operation, light beams L_A^r and L_A^l sequentially illuminate the image engine while synchronized by sequentially feeding the right and left images for viewer A (146) into the image engine, as discussed with reference to FIG. 1. The modulated illumination light carrying right and left image information for viewer 146 are projected to passive Infitech filters of viewer 146 wherein light beams L_A^r and L_A^l separately pass through right and left lens filters of the viewer 146. After one or multiple frames of images for viewer A are modulated and projected to viewer A, image engine can be operated to re-produce images for viewer B 154. During this time period, light beams L_B^r and L_B^l sequentially illuminate the image engine while synchronized by sequentially feeding the right and left images for viewer B (154) into the image engine. The modulated illumination light carrying right and left image information for viewer 154 are projected to passive Infitech filters of viewer 154 wherein light beams L_B^r and L_B^l separately pass through right and left lens filters of the viewer 154. After modulating one or more frames of images for viewer B, the image engine can turn again to re-produce images for viewer A. The above process is repeated for re-producing images for both viewers.

In an alternative example, image engine can be operated to re-produce right (or left) images for right (or left) side eye of viewer 146 followed by re-producing images for right (or left) images for right (or left) side eye of the different viewer 154, which will not be discussed in detailed herein. Of course, other than single image engine, the stereoscopic system can employ multiple image engines for re-producing images for separate (or the same) viewer(s). For example, the image engine 110 in FIG. 10 can be assigned to re-produce images for viewer A 146. Another image engine (not shown in the figure) can be provided to reproduce images for viewer 154. In this example, illumination light beams L_A^r and L_A^l preferably illuminates only the image engine designated to reproduce images for viewer A; and illumination light beams L_B^r and L_B^l preferably illuminates only the image engine designated to reproduce images for viewer B.

In yet another example, multiple image engines are provided with each image engine being assigned to re-produce only a portion of the images for both viewers A and B. For example, an image engine can be assigned to reproduce right images for right side eyes of both viewers 146 and 154; while another image engine can be assigned to reproduce left images for left side eyes of both viewers 146 and 154.

Even for one viewer, provision of multiple image engines in the system can also be advantageous in imaging performance. An example of such system is schematically illustrated in FIG. 11. Referring to FIG. 11, image engines 110a and 110b are provided for respectively reproducing images for right and left side eyes 118 and 120. For this purpose, right images to be re-produced for right side eye of the viewer are delivered to image engine 110a; and left images to be re-produced for left side eye of the viewer are delivered to image engine 110b. Operations of image engines 110a and 10b, feeding of the right and left images, and emitting of the illumination light from the illumination system can be synchronized by synchronization unit 113.

Instead of juxtaposing multiple image engines (102a and 102b) in parallel on the optical path of the display system for independently re-producing images, the multiple image engines can be serially disposed on the optical path of the system, as shown in FIG. 12. This configuration can be of importance in obtaining high dynamic range (e.g. 2000:1 or higher and 10,000:1 or higher) and high resolution. Referring to FIG. 12, image engine 110a is disposed in front of image engine 110b on the optical path of the system. The two image engines may or may not have the same resolution or same type of physical pixels. For example, one of the image engines may be composed of micromirrors whereas the other one can be composed of LCD cells, LCOS cells, or plasma cells. The front side image engine is designated to project images onto the rear side image engine. As a result, the contrast ratio of each pixel of the reproduce image (perceived by viewer's eyes) is a product of the natural contrast ratios of the two image engines. By offsetting the pixel arrays of image engines 110a and 110b a small distance, fro example half the pixel size of the image engine along the diagonal of the pixel array, the perceived resolution of the reproduced images can be approximately quadrupled. Operations of the image engines 110a and 110b can be synchronized to the illumination system (102) and feeding of the right and left images by synchronization unit 113, as shown in the figure.

It will be appreciated by those of skill in the art that a new and useful stereoscopic display system and a method producing stereoscopic virtual objects using the same have 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. A method, comprising:

producing first and second light beams that are composed of different numbers of colors;

modulating the first and second light beams based upon first and second sets of image data that are respectively derived from first and second sets of images; and

passing the modulated first and second light beams through a pair of passive glasses with built-in first and second interference filters for viewing.

2. The method of claim 1, wherein the first and second light beams are narrow band light beams.

3. The method of claim 2, wherein the first light beam comprises red, green, and blue colors.

4. The method of claim 3, wherein the first light beam further comprises yellow and cyan colors.

5. The method of claim 2, wherein the first and second light beams are produced by a set of solid-state light sources that are lasers or light emitting diodes.

6. The method of claim 3, further comprising:

sequentially directing the first and second light beams onto an image engine that modulates the first and second light beams.

7. The method of claim 3, further comprising:

simultaneously directing the first and second light beams onto an image engine that modulates the first and second light beams.

8. The method of claim 2, further comprising:

producing third and fourth narrowband light beams whose wavelength spectrums substantially have no overlap;

modulating the first and second light beams to re-produce images for a first viewer; and

modulating the third and fourth light beams to re-produce images for a second viewer.

9. The method of claim 8, wherein the step of modulating the first and second light beams further comprises:

at a first time period, modulating the first light beam so as to re-produce the first set of images; and

at a second time period modulating the second light beam so as to re-produce the second set of images.

10. The method of claim 9, wherein the first and second time period are substantially equal to a frame period.

11. The method of claim 2, further comprising:

producing third and fourth narrowband light beams whose wavelength spectrums substantially have no overlap;

modulating the first and second light beams so as to re-produce a portion of the first and second sets of images for first and second viewers; and

modulating the first and second light beams to re-produce another portion of the first and second sets of images for first and second viewers.

12. The method of claim 11, wherein the step of modulating the first and second light beams so as to re-produce a portion of the first and second sets of images for first and second viewers further comprises:

at a first time period, modulating the first light beam so as to re-produce the first portion of the first set of images; and

at a second time period, modulating the second light beam so as to re-produce the second portion of the first set of images.

13. The method of claim 11, wherein the step of modulating the first and second light beams further comprises:

directing the first and second light beams onto a first image engine;

the first engine modulating the first and second light beams based upon at least a portion of the first and second sets of images so as to generate first and second modulated light beams; and

projecting the first and second modulated light beams from the first image engine onto a second image engine so as to re-produce the first and second sets of images.

14. A system capable of producing a stereoscopic image, the system comprising:

an illumination system capable of producing first and second sets of light beams, wherein the wavelengths of light of the first set are not substantially overlapped with the wavelengths of light of the second set, and wherein the first set light beams comprises a different number of colors than the second light beam.

a color processor capable of scaling a color space of the stereoscopic image;

an image engine for re-producing a set of images derived from the stereoscopic image by modulating the light beams based upon the stereoscopic image; and

a passive glass with a built-in interference filter for separating the set of images.

15. The system of claim 14, wherein the image engine comprises an array of micromirrors.

16. The system of claim 14, wherein the image engine comprises an array of liquid-crystal cells.

17. The system of claim 14 is a front projection system.

18. The system of claim 14 is a rear projection system.

19. The system of claim 14 is a backlit display system.

20. The system of claim 14, further comprising:

another image engine disposed on an optical path of the system.

21. A method, comprising:

producing first and second narrowband light beams;

modulating the first and second light beams based upon first and second sets of image data that are respectively derived from first and second sets of images;

passing the modulated first and second light beams through a pair of passive glasses with built-in first and second interference filters for viewing such that the modulated first light beam is capable of passing through and substantially only the first interference filter; and such that the modulated second light beam is capable of passing through and substantially only the second interference filter; and

delivering the re-produced first set of images to a first viewer, and the second set of images to the second viewer for viewing.

22. The method of claim 21, wherein the light beams are composed of different numbers of colors

23. The method of claim 22, wherein the first light beam comprises red, green, blue, yellow and cyan colors.

24. The method of claim 22, wherein the first and second light beams are produced by a set of solid-state light sources that are lasers or light emitting diodes.

25. The method of claim 21, further comprising:

producing third and fourth narrowband light beams whose wavelength spectrums substantially have no overlap;

modulating the first and second light beams to re-produce images for a first viewer; and

modulating the third and fourth light beams to re-produce images for a second viewer.

26. The method of claim 21, further comprising:

producing third and fourth narrowband light beams whose wavelength spectrums substantially have no overlap;

modulating the first and second light beams so as to re-produce a portion of the first and second sets of images for first and second viewers; and

modulating the first and second light beams to re-produce another portion of the first and second sets of images for first and second viewers.