presented an apparatus and method for printing one-step, full-color, full-parallax holographic stereograms 36. In the next year, Yamaguchi analyzed the wavefront reconstruction of holographic stereogram and proposed phase added stereogram (PAS) 35, which required less computation load than actual CGH and presented higher reconstruction quality. In 1992, Yamaguchi proposed a new holographic stereogram printer 34, which can make accurate distortionless hard copies of 3 D object with both horizontal and vertical parallaxes. 33, in which the relationship between capture and recording geometries was relaxed and the viewer can still get 3D stereoscopy at arbitrary plane. In 1991, the ultragram was described by Halle et al. In 1990s, most large reflection holographic stereograms had therefore started to be recorded using the DeBitetto/King model 23 31, 32. Considering the cost of time, the final holographic stereogram usually contained only horizontal parallax. In 1970, King fabricated a holographic stereogram by DeBitetto’s process and printed its Fresnel hologram furtherly to obtain a white light-viewable image plane hologram 24. In 1969, the slit was added into holographic stereogram printing system creatively by DeBitetto 23 to improve the poor resolution of holographic stereogram. According to this approach, the virtual stereo images of the 3D object can be reconstructed. The holographic stereogram has become the focus of research 8, 25, 26, 27, 28, 29, and are also widely applied in many fields 30.Īs early as 1967, Pole photographed the 3D scene illuminated with ordinary white light by a fly’s eye lens to generate a "holocoder", and then converted the "holocoder" into a Fresnel hologram 22. A series of perspective images is obtained recoded to expose into small holographic elements, which are called hogels. Compared to the traditional hologram as well as the CGH, holographic stereogram can reconstructed real or virtual objects by printing reflection hologram with high-fidelity, distortion-free and full-color multiple reconstructed 3D images 22, 23, 24. Some other holographic technologies have also been developed due to the progress on novel materials or devices 17, 18, 19, 20, 21. CGH is ideally suited to transmission holography and has no ability to print reflection hologram. Similarly, the computer-generated hologram (CGH) also records the wavefront information by numerical calculation and electron beam lithography/laser direct writing 14, 15, 16. Traditional hologram is capable of reproducing extremely high-quality 3D images by wavefront reconstruction, which can be achieved by the way of interference between the object light and the reference light. Holography is a promising approach to get realistic 3D reconstruction 12, 13. Three dimensional (3D) display has attracted an intense research interest in recent years 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and it also has potential applications in variable fields, such as industrial, medical, military, artistic, and so on 11. Both the numerical and optical experiments are implemented, and the results are well agreed with the theoretical prediction, which demonstrates that the view-flipping reduction and reconstruction visualization enhancement for EPISM based holographic stereogram can be achieved when the proper size of hogel is utilized. The theory shows that there is an optimal hogel size existed for the certain depth of scene. Furthermore, a diffraction-limited imaging model of the hogel based holographic stereogram is established, where both the limited aperture of the hogel and the defocused aberration of the object point are introduced, and the effective resolvable size of the reconstructed image point is simulated. The performance of the view-flipping effect is analyzed, and the results indicate that decreasing the size of hogel is beneficial to the reduction of the view flipping, however, which will result in significant diffraction effect which can degrade the reconstruction quality. To reduce the view-flipping effect and enhance the viewing resolution, the modulation characteristics of the hogel based holographic stereogram is constructed and validated.
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