Serguei A. Shestak

Desktop autostereoscopic display with head tracking capability

A desktop 20 inches autostereoscopic display system based on two 6.5 inches LCD projection panels and a single objective is described. The system employs vertical separation of left and right views in the objectives entrance pupil for the viewing zone forming. The vertically separated views are horizontally divided with use of a positioned at the pupil. This diaphragm is composed of two horizontally parallel LC stripes shutters which are made of independently working 32 black and white LCD columns. A rear projection type screen made of a Fresnel lens with a vertical diffuser is used for the image projection. The screen provides the best viewing distance of 70 - 80 cm. The system equipped with a head-tracking device for 16-view image display. The system is compatible with any dual monitor SVGA video card with resolution 800 X 600 or any source of parallel stereoscopic video signal. The size of the system is comparable to that of 20 inch CRT monitor.

Achromatized transmission-type holographic screen for a multiview stereoscopic image system

The main drawback of the use of transmission-type holographic screens is poor color reproduction caused by their high spectral dispersion. For overcoming this drawback, a long, narrow diffusing slit is used as an object when recording the screen. The necessary size and position of the slit relative to the photoplate and to the recording and reconstruction beams are determined by the phase relations of the beams. By use of the slit, holographic screens of 30 cm x 40 cm are recorded with a diverging reference beam and are used to display a multiview full-color stereoscopic image. The images displayed on the screen show no sign of color separation except near the edges of the screen. The image brightness on the screen is high enough that it can be watched in a normally illuminated room.

Sliding-aperture multiview 3D camera-projector system and its application for 3D image transmission and IR to visible conversion

A new architecture of the 3-D multiview camera and projector is presented. Camera optical system consist of a single wide aperture objective, a secondary (small) objective, a field lens and a scanner. Projector supplementary includes rear projection pupil forming screen. The system is intended for sequential 2-D prospective images acquisition and projection while the small working aperture is sliding across the opening of the big size objective lens or the spherical mirror. Both horizontal and full parallax imaging are possible. The system can transmit 3-D images in real time through fiber bundles, free space, and video image transmission lines. This system can also be used for real time conversion of infrared 3-D images. With this system, clear multiview stereoscopic images of real scene can be displayed with 30 degrees view zone angle.

Recent improvement of pulsed laser electro-holographic system

The application of pulsed laser in real time holography base don acousto-optic (AO) cells allows to get rid of mechanical horizontal scanning. The improvement of recently reported real time pulsed holographic display is presented. Ar-ion laser, used before as a coherent light source, is replaced with Q-switching Nd:YVO4 laser with SHG, operated by external triggering at 46 kHz. The commercial PC dual monitor graphic card was adapted to generate six parallel analogue outputs to feed six AO cells with gray scale hologram data. The upgrade improves brightness and clearness of reconstructed images and reduces the system dimensions and power consumption. 2D and 3D images reconstructed from precomputed HPO holograms are presented.

Achromatized-transmission-type holographic screen for stereo imaging and the multiview projection

The main drawback of a transmission type holographic screen is the color separation when the color images are projected on it due to its high dispersion. This drawback can be overcome by recording the screen with use of a long narrow slit type diffuser as an object. With the diffuser, a holographic screen of size 30 by 40 cm2 has been recorded to display a full color stereoscopic image. The images displayed on the screen show a good resolution and are naturally colored, except near the edges of the screen. The color distortions in the edges of the screen are reduced by a lenticular sheet attached to the screen. The lenticular sheet enlarges the viewing zone. The image that appears on the screen is bright enough to watch even in a normally illuminated room

Electroholographic display with sequential viewing zone multiplexing

Electroholographic display with viewing zone multiplexing, based on multichannel AOM is described. A method of viewing zone multiplexing resides in sequential reconstruction of elemental perspective views of the 3D object, accompanied by the formation of moving exit pupil of the display. The exit pupil is created by the combination of field lens and synchronously scanning reflection type vertical diffuser, placed in the reconstructed image volume. The method makes possible spatio-temporal multiplexing of wide viewing zone without resort to optical demagnification. The method is also capable of viewing zone extension without any reduction in lateral size of the reconstructed image. Two types of reconstruction geometry have been considered. One is corresponded to reconstruction of real image Fresnel type hologram, another is similar to Fourier type. Fresnel type display with image size 7 X 7 cm is designed for the experimental realization.

Emitting diagram control method for solid-object 3D display

We present a new method for solid object 3-D imaging which can control the emitting diagram of each image point and can be applied in volumetric displays. A new method is based on the fact that the visibility of each point of the 3-D object or scene can be described in the terms of points emitting diagram. It was found that the amount of information for the emitting diagram in general has the same order of magnitude as that for sampled hologram. The emitting diagram control can be applied to many different types of volumetric display with use of means like spatial filters. Unlike the electroholography, the method provides 3-D positioning of image points and emitting diagram forming separately. So in special cases, it allows us to reduce significantly information amount. Experimentally, we obtained a color stereoscopic image with a number of resolvable perspective views, distributed within 30 angular degrees using only two 2-D images and a moving shield as the diagram former.

Electroholographic display with minimum data redundancy

A method for synthesis of driving RF signal, corresponding to sampled hologram, which allows to minimize the capacity of the display memory, is suggested. With the application of new method required frame-buffer capacity for the current displays can be reduced by the factor 1.8 - 3. We have considered three variants of hologram sampling method for data reduction. It is found that minimum hologram data redundancy can be achieved with Fourier and Image types of holographic stereograms. For given 3-D image resolution a maximum image size, which can be displayed without redundancy is determined as 4...5 cm. Further scaling of the image requires application of the sampling method. With proper improvement of the hardware, application of hologram sampling method provides stable capacity of the display memory a little over 32 MB regardless of the image size. Since the method also permits direct synthesis of driving RF signal, acousto-optical modulators with up to several GHz bandwidth can be employed in electroholographic display.

Holographic video system using Fourier transform method adapted to two-dimensional and three-dimensional data calculation

A holographic video system, displaying computer generated Fourier transform hologram is described. The method of Horizontal Parallax Only (HPO) Fresnel CGH is well known. HPO computer generated Fourier transform hologram is basically 2- dimensional hologram. To expand an HPO computer generated Fourier transform hologram algorithm based on the ray tracing is introduced. This algorithm can possibly reduce CGH data amount and CGH calculation time. The experimental result is included, and it shows the reduction of CGH data amount and CGH calculation time. One extra advantage compared with Fresnel CGH is described as well.

Compensation of 3D image perspective distortion using a sliding-aperture multistereoscopic technique

Magnified real image of 3D object, provided by conventional optical means is more stretched in depth by the factor of lateral magnification. We found, that our recently reported sliding aperture multistereoscopic technique, utilizing sequential views projection on the scanning mirror, is capable of producing equally magnified 3D images. This capability is based on image depth control that can be used for compensation of perspective distortion, caused by the optical magnification. Image formation analysis shows that relative visual position of a certain image point in depth can be exactly corrected in order to get the same scaling in both depth and lateral direction. Longitudinal position of other points of image will also be corrected, but with some error, depending on their lateral and longitudinal positions. This error results from the difference between the nonlinear components of perspective distortion and compensation mechanism. Error magnitude is usually small enough for the image to look equally magnified.