Optical EngineeringComputer-generated cylindrical rainbow hologram
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We investigate the computer-generated cylindrical rainbow hologram. Since the general flat format hologram has a limited viewable area, we usually cannot see the other side of the reconstructed object. There are some holograms to solve this problem. A cylindrical-type hologram is well known as the 360-deg viewable hologram. There are two kinds of cylindrical holograms, a multiplex hologram and a laser reconstruction 360-deg hologram. Since the multiplex hologram consists of many 2-D pictures, the reconstructed image is not truly 3-D. In contrast, a laser reconstruction 360-deg hologram has a true 3-D effect. However, since the spatial resolution of the output device is not enough and the calculation amount is huge, there are few reports on computer-generated cylindrical holograms. In our previous study, the computer-generated cylindrical hologram was realized as a Fresnel hologram. The calculation amount was too huge and took about 44 h in total calculation time, though we had used several PCs. We now propose the rainbow-type computer-generated cylindrical hologram. To decrease the calculation amount, the rainbow hologram sacrifices the vertical parallax. Also, this hologram can reconstruct an image with white light. Compared with the previous study of the Fresnel type, the calculation speed becomes 165 times faster. After calculation, we print this hologram with a fringe printer, and evaluate reconstructed images.