GB2273577A

GB2273577A - Autostereoscopic directional display apparatus

Info

Publication number: GB2273577A
Application number: GB9226272A
Authority: GB
Inventors: David Ezra; Basil Arthur Omar; Graham John Woodgate
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 1992-12-17
Filing date: 1992-12-17
Publication date: 1994-06-22
Also published as: GB9226272D0

Abstract

The number of 2D views available to form an autostereoscopic 3D image is increased by using a beam combiner (9) with two displays each having multiple views. Each display may comprise sequentially illuminatable light sources (1, 5) imaged by converging lenses (3, 7) for illuminating sequentially reproduced 2D images in spatial light modulators (4, 8). Alternatively or additionally a spatial light modulator and a lenticular array (Fig. 4) may provide each display. The views are combined by the optical combiner (9) so as to be visible to an observer (10) in different directions corresponding to the directions from which the views were recorded during image capture. <IMAGE>

Description

AUTOSTEREOSCOPIC DIRECTIONAL DISPLAY APPARATUS.

The present invention relates to autostereoscopic directional display apparatuses. Such apparatuses may be used to convert spatial and/or temporal information into directional information, for instance so as to provide an autostereoscopic three dimensional display.

Known three dimensional (3D) display apparatuses which can create images of opaque moving objects rely on creating the perception of a 3D image to a human observer by displaying a number of two dimensional (2D) images.

Each of the 2D images is a view of the object from a particular direction and is "replayed" in that direction.

The accuracy and effectiveness of these 3D images and the maximum display size and freedom of viewer location increase as the number of 2D views displayed increases.

Two known techniques for providing 3D displays use lenticular methods and time multiplexed or sequential methods. For effective operation, such systems must display a large number of 2D views of an object. In direct view lenticular systems, the maximum number of views is determined by the resolution of a spatial light modulator (SLM) used in the system whereas, in multiple projector systems, the maximum number of views is determined by the number of separate SLM's used. In time multiplexed systems, the frame rate of the SLM determines the maximum number of views.

With known arrangements, to display a large number of views, the maximum frame rates of practical available SLM's are insufficient for time multiplexed displays and the maximum resolution of presently available SLM's is insufficient for direct view lenticular methods.

Multiple projector lenticular methods with a large number of SLM's are expensive and bulky. Thus, known 3D display systems are incapable of or inconvenient for accurately providing a moving electronic opaque colour autostereoscopic 3D image from a range of perspectives.

British Patent Application No.9210399.3 discloses time multiplexed and spatially multiplexed systems, and a system which combines spatial and temporal multiplexing to provide a 3D display with a larger number of views.

However, the maximum resolution and frame rate of currently available SLM's limits the number of views that can be displayed.

A known 3D display technique uses a beam combiner and polarising techniques to provide a 3D image which is limited to two views. However, this technique is not autostereoscopic but is stereoscopic, i.e. the observer has to wear polarising glasses in order to see the 3D effect.

According to the invention, there is provided an autostereoscopic directional display apparatus comprising a plurality of displays and an optical combining system, the displays co-operating with the optical combining system to provide a plurality of views which are visible in respective different directions.

Such an apparatus may be used as a 3D display apparatus to provide a relatively large number of 2D views.

Alternatively, such an apparatus may be used in other applications, for instance to provide a sign displaying different information when viewed in different directions.

Preferably each of the directions in which the views are visible comprises an angular range, and the angular ranges are angularly contiguous in a lateral plane.

Each of the displays may comprise a spatial light modulator, an optical system, and a light source.

Preferably each of the displays cooperates with the optical combining system to provide a plurality of views which are visible in respective different directions.

Preferably the directions in which the views provided by each of the displays and the optical combining system are visible are different from the directions in which the views provided by the or each other of the displays and the optical combining system are visible.

Preferably the directions in which the views provided by each of the displays are visible are interlaced with the directions in which the views provided by the or each other of the displays are visible.

Each of the displays may be of the temporally multiplexed type in which the views provided by the display to form the or each 3D image are produced one at a time.

Alternatively, each of the displays may be of the spatially multiplexed type in which the views provided by the display to form the or each 3D image are produced simultaneously. In a further embodiment, each of the displays combines temporal and spatial multiplexing.

It is thus possible to provide optical devices which may be used in direct view display systems and which combine a number of displays of spatial and/or temporal type to increase the rate of display of 2D images or views. By increasing the number of views, it is possible to improve the accuracy and appearance of a 3D image. It is also possible to produce a larger 3D display with a larger range of viewing positions. No viewing aids are necessary to see the 3D effect, i.e. the display is autostereoscopic. Furthermore, known image capture techniques may be used so that colour, movement and opaque images may all be displayed.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic plan view of a 3D display using temporal multiplexing and constituting a first embodiment of the invention; Figures 2 and 3 are diagrammatic plan views illustrating operation of the display of Figure 1; Figure 4 is a diagrammatic plan view of a 3D display using spatial multiplexing and constituting a second embodiment of the invention; Figures 5 and 6 are diagrammatic plan views illustrating operation of the display of Figure 4; Figures 7 and 8 are diagrammatic plan views of 3D displays using temporal and spatial multiplexing and constituting third and fourth embodiments, respectively, of the invention; and Figures 9 and 10 are diagrammatic plan views of 3D displays constituting fifth and sixth embodiments, respectively, of the invention.

Like reference numerals refer to like parts throughout the drawings.

The 3D display shown in Figure 1 comprises a first display comprising a plurality of light sources 1 and a control circuit 2 for sequentially illuminating the light sources 1. Four light sources 1 are shown spaced apart laterally with a pitch which is substantially equal to the lateral extent of each of the light sources 1. An optical system shown in the drawing as a lens 3 is disposed between the light sources 1 and a spatial light modulator (SLM) 4. Alternatively, the SLM 4 may be disposed between the light sources 1 and the lens 3 and adjacent the lens 3.

The SLM 4 may comprise a liquid crystal device and is arranged to display a plurality of 2D views in sequence such that each view is illuminated by a respective one of the light sources 1. The 2D views are thus visible from different angles corresponding to the angles at which the views were recorded during image capture.

The display further comprises a plurality of light sources 5, a control circuit 6, a lens 7, and an SLM 8 which are substantially identical to the light sources, the control circuit 2, the lens 3, and the SLM 4, respectively.

The views from the two temporally multiplexed display arrangements are combined by means of an optical combining system shown in the drawing as a beam splitter 9. The views reproduced by the SLM 4 are transmitted through the beam splitter 9 towards an observer 10 whereas the views from the SLM 8 are reflected by the beam splitter 9 towards the observer 10. Figure 2 illustrates the directions in which the views from the two temporally multiplexed display arrangements are projected towards the beam splitter 9. Figure 3 shows the apparent light source positions and directionality as perceived by the observer 10 via the beam splitter 9.

Each 3D image component fills a defined range of image output angles with the components from the two display arrangements being interlaced with each other so that a laterally continuous spread of light emerges from the display. A reconstruction of the 3D image is thus observed over a continuous range of angles by a suitably positioned observer 10.

The 2D images reproduced by means of the SLM 8 are laterally inverted by the beam splitter 9. Compensation for this may be provided by laterally inverting the 2D views in the SLM 8.

The beam splitter 9 may comprise any device or system which is capable of performing the optical combining function. For instance, the beam splitter 9 may comprise a partially silvered mirror. Alternatively, in order to reduce the absorption of incident light caused by metallic coatings, all-dielectric non-polarising coatings may be used. However, such coatings are usually designed for particular wavelengths and may thus be of limited application. A hybrid metal-dielectric coating combines the benefits of metals and dielectrics to provide a splitter of moderate absorption, low polarisation sensitivity, and good broadband spectral flatness.

Figure 4 shows a display which comprises two spatially multiplexed display arrangements in place of the temporally multiplexed display arrangements of Figure 1.

The SLM's 4 and 8, the beam splitter 9, and the observer 10 correspond to those shown in Figure 1. However, the SLM 4 is illuminated by means of a diffuse light source 11 and the modulated light emerging from the SLM 4 passes through a lenticular screen 12 which comprises a plurality of plano-cylindrical converging lenticules disposed with a regular lateral pitch. Similarly, a diffuse light source 13 and a lenticular screen 14 are provided for the SLM 8.

Each of the SLM's 4 and 8 simultaneously produces a plurality of interlaced 2D views made up of thin vertical picture elements. A plurality of such picture elements from different views is displayed behind each of the lenticules of the screens 12 and 14 as illustrated in Figure 5. These views are combined by the beam splitter 9 so as to give an apparent picture element position and directionality as illustrated in Figure 6. Thus, as in the embodiment of Figure 1, the reconstructed 3D image is observed over a continuous range of angles by suitably positioned observer.

In order to increase the number of available views, the techniques of spatial and temporal multiplexing may be combined as illustrated in the display of Figure 7. The light sources 1 and 5, the control circuits 2 and 6, the lenses 3 and 7, and the beam splitter 9 are the same as shown in Figure 1. However, the SLM's 4 and 8 of Figure 1 are replaced by hybrid sandwiches 20 and 21 of the type disclosed in British Patent Application No.9210399.3.

Each of the hybrid sandwiches comprises a first lenticular screen having a first lenticular pitch, an SLM, a diffuser, and a second lenticular screen having a second lateral pitch which is greater than the first pitch. The pitch of the second lenticular screen is substantially equal to an integer multiple of the pitch of the first screen.

The light sources 1 and 5 are illuminated sequentially by the control circuits 2 and 6 and image information is supplied sequentially to the SLM's of the hybrid sandwiches 20 and 21 in synchronism with the illumination. Each "frame" of image information supplied to the SLM's comprises a plurality of images which are spatially multiplexed as described with reference to the embodiment of Figure 4. The individual 2D views are therefore reproduced over angular ranges in directions which correspond to the directions from which the views were recorded during image capture and the beam splitter 9 combines the views so that the observer 10 can observe the 3D image over a continuous range of angles.

The displays shown in Figures 1 to 7 each comprise a single beam splitter 9 co-operating with two display arrangements to increase the number of 2D views which can be provided to form a composite 3D image. However, a plurality of beam splitters may be provided and the display shown in Figure 8 comprises two beam splitters 9 and 29 with three display arrangements of the combined spatial and temporal multiplexing types shown in Figure 7. The third display arrangement comprises light sources 31, a control circuit 32, a lens 33, and a hybrid sandwich 34 which are substantially identical to the light sources 1, the control circuit 2, the lens 3, and the hybrid sandwich 20, respectively. The views from the hybrid sandwich 20 are transmitted directly through the beam splitters 9 and 29 to the observer 10.The views from the hybrid sandwich 21 are reflected by the beam splitter 9 and transmitted through the beam splitter 29 to the observer 10. The views from the hybrid sandwich 34 are reflected by the beam splitter 29 towards the observer 10. It is therefore possible to provide a larger number of 2D views to form the composite 3D image.

Figure 9 shows a 3D Display of relatively simple type for providing two views. The Display of Figure 9 resembles that of Figure 1 but differs in that the light sources 1 and 5 and the control circuits 2 and 6 are replaced by continuously illuminated light sources 41 and 42.

Figure 10 shows a 3D Display which is similar to that of Figure 9 but which includes a further beam splitter 29, lens 43, and SLM 44. The Display of Figure 10 has three continuously illuminated light sources 51, 52, and 53 and provides three views. The light sources 51, 52, and 53 are arranged such that the light source 52 is on the axis and 53 are arranged such that the light source 52 is on the axis of the lens 43 whereas the light sources 51 and 53 are displaced from the axis of the lens 3 and 7, respectively, so that the light beams leaving the beam splitter 9 are laterally contiguous with each other.

Displays of the type shown in the drawings may be used in 3D television, 3D computer aided design and graphics, 3D medical imaging, virtual reality, and computer games. By providing an increased number of 2D views to make up the 3D image, the accuracy and effectiveness of the 3D images can be increased and the maximum display signs and freedom of viewer location can be increased. Further, moving opaque colour autostereoscopic 3D images from a range of perspectives may be reproduced.

Claims

CLAIMS:

1. An autostereoscopic directional display apparatus comprising a plurality of displays and an optical combining system, the displays co-operating with the optical combining system to provide a plurality of views which are visible in respective different directions.

2. An apparatus as claimed in Claim 1, in which each of the directions in which the views are visible comprises an angular range.

3. An apparatus as claimed in Claim 2, in which the angular ranges are angularly contiguous in a lateral plane.

4. An apparatus as claimed in any one of the preceding claims, in which each of the displays comprises a spatial light modulator, an optical system, and a light source.

5. An apparatus as claimed in any one of Claims 1 to 3, in which each of the displays cooperates with the optical combining system to provide a plurality of views which are visible in respective different directions.

6. An apparatus as claimed in Claim 5, in which the directions in which the views provided by each of the displays and the optical combining system are visible are different from the directions in which the views provided by the or each other of the displays and the optical combining system are visible.

7. An apparatus as claimed in Claim 5 or 6, in which the directions in which the views provided by each of the displays are visible are interlaced with the directions in which the views provided by the or each other of the displays are visible.

8. An apparatus as claimed in any one of Claims 5 to 7, in which each of the displays comprises a temporally multiplexed display.

9. An apparatus as claimed in Claim 8, in which each of the displays comprises a spatial light modulator, an optical system, and a plurality of sequentially illuminatable light sources arranged to illuminate the spatial light modulator at respective different angles via the optical system.

10. An apparatus as claimed in any one of Claims 5 to 7, in which each of the displays comprises a spatially multiplexed display.

11. An apparatus as claimed in Claim 10, in which each of the displays comprises a spatial light modulator, a diffuse light source for illuminating the spatial light modulator, and an array of lenses disposed between the spatial light modulator and the optical combining system.

12. An apparatus as claimed in Claim 11, in which the array of lenses comprises a lenticular screen.

13. An apparatus as claimed in any one of Claims 5 to 7, in which each of the displays comprises a temporally and spatially multiplexed display.

14. An apparatus as claimed in Claim 13, in which each of the displays comprises a spatial light modulator, a first array of lenses having a first pitch disposed adjacent a first side of the spatial light modulator, a second array of lenses having a second pitch greater than the first pitch disposed adjacent a second side of the spatial light modulator between the spatial light modulator and the optical combining system, an optical system, and a plurality of sequentially illuminatable light sources arranged to illuminate the first array of lenses at respective different angles via the optical system.

15. An apparatus as claimed in any one of the preceding claims, in which the optical combining system comprises at least one beam combiner having an optically transmissive path and an optically reflective path.

16. A directional display apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 3 of the accompanying drawings.

17. A directional display apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 4 to 6 of the accompanying drawings.

18. A directional display apparatus substantially as hereinbefore described with reference to and as illustrated in Figure 7 of the accompanying drawings.

19. A directional display apparatus substantially as hereinbefore described with reference to and as illustrated in Figure 8 of the accompanying drawings.