IMPROVED ELECTROHOLOGRAPHIC DISPLAY USING LIQUID-CRYSTAL DEVICES TO SHORTEN THE VIEWING DISTANCE WITH BOTH-EYE OBSERVATION

We are constructing an electroholographic display system using liquid crystal devices (LCDs) as spatial light modulators to control the wave front of laser light for reconstructing 3-D images. A wide horizontal viewing zone is secured with five special LCDs set up in a continuous series by a half mirror. The viewing distance is still considerably lo ng, however, and this distance reduces the perception of image depth. Thus, we suggest setting a field lens at the center of the reconstruct ed image to shorten the viewing distance. Since the reconstructed 3-D image becomes considerably distorted by the use of a field lens, we pr opose predistortion to compensate. Each LCD is assumed to have 3200 (H ) x960 (V) pixels with 28 (H) x56 (V) mu m pixel pitch. Although, this LCD is still in trial production, we have confirmed the reconstructed image by replacing the LCDs with computer-generated holograms (CGHs) recorded to five photographic films having the same specifications as real LCDs. In this way, we verified the reconstructed image [50 (W) x5 0 (D) x100 (H) mm] with off-axis, horizontal parallax only. This image can be observed with both eyes at a distance of 900 mm, and we can pe rceive the image depth sufficiently. (C) 1996 Society of Photo-Optical Instrumentation Engineers.