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Natural three-dimensional images can be produced by displaying a large number of directional images with directional rays. Directional images are orthographic projections of a three-dimensional object and are displayed with nearly parallel rays. We have already constructed 64-directional, 72-directional, and 128-directional natural three-dimensional displays whose angle sampling pitches of horizontal ray direction are 0.34°, 0,38°, and 0.25°, respectively. In this study
we constructed a rotating camera system to capture 360° three-dimensional information of an actual object. An object is located at the center of rotation and a camera mounted at the end of an arm is rotated around an object. A large number of images are captured from different horizontal directions with a small rotation angle interval. Because captured images are perspective projections of an object, directional images are generated by interpolating the captured images. The 360° directional image consists of 1,059, 947, and 1,565 directional images corresponding to the three different displays. When the number of captured images is about ~ 4,000, the directional images can be generated without the image interpolation so that correct directional images are obtained. The degradation of the generated 360° directional image depending on the number of captured images is evaluated. The results show that the PSNR is higher than 35 dB when more than 400 images are captured. With the 360° directional image, the three-dimensional images can be interactively rotated on the three-dimensional display. The data sizes of the 360° directional images are 233 MB, 347 MB, and 344 MB, respectively. Because the directional images for adjacent horizontal directions are very similar, 360° directional image can be compressed using the conventional movie compression algorithms. We used H.264 CODEC and achieved the compression ratio 1.5 % with PSNR > 35 dB.
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