Holographic display is a true three-dimensional (3D) display technology presenting all depth cues without using any
special glasses. With this technology we have developed a system of city photonics map. In the system there are three
key steps: gaining raw 3D point clouds data, Computer-generated holograms, and digital holographic display of 3D data.
In the first step, the theory of structure from motion (SfM) is applied. Then an algorithm of phase CGH with inverse
diffraction is proposed and implemented. Difference from ordinary CGH is that the diffraction fringes of 3D
reconstructed terrain data are obtained from the diffraction results by the reverse strike means. At last, 3D hologram is
displayed on the developing experimental platform and printed on the holographic silver halide plate.
Proc. SPIE. 8556, Holography, Diffractive Optics, and Applications V
KEYWORDS: Diffraction, 3D acquisition, 3D image reconstruction, Modulation, Image processing, Computer generated holography, Spatial light modulators, Near field diffraction, Reconstruction algorithms, 3D image processing
A novel method for computing kinoform of 3D object based on traditional iterate Fourier transform algorithm(IFTA) is proposed in this paper. Kinoform is a special kind of computer-generated holograms (CGH)，which has very high diffraction efficiency since it only modulates the phase of illuminated light and doesn’t have cross-interference from conjugate image. The traditional IFTA arithmetic assumes that reconstruction image is in infinity area(Fraunhofer diffraction region), and ignores the deepness of 3D object ,so it can only calculate two-dimensional kinoform. The proposed algorithm in this paper divides three-dimensional object into several object planes in deepness and treat every object plane as a target image，then iterate computation is carried out between one input plane(kinoform) and multi-output planes(reconstruction images) .A space phase factor is added into iterate process to represent depth characters of 3D object, then reconstruction images is in Fresnel diffraction region. Optics reconstructed experiment of kinoform computed by this method is realized based on Liquid Crystals on Silicon (LCoS) Spatial Light Modulator(SLM). Mean Square Error(MSE) and Structure Similarity(SSIM) between original and reconstruction image is used to evaluate this method. The experimental result shows that this algorithm speed is fast and the result kinoform can reconstruct the object in different plane with high precision under the illumination of plane wave. The reconstruction images provide space sense of three-dimensional visual effect. At last, the influence of space and shelter between different object planes to reconstruction image is also discussed in the experiment.