True-3D imaging and display systems are based on physical duplication of light distribution. Holography is a true-3D technique. There are significant developments in electro-holographic displays in recent years. Liquid crystal, liquid crystal on silicon, optically addressed, mirror-based, holographic polymer-dispersed, and acousto-optic devices are used as holographic displays. There are complete electro-holographic display systems and some of them are already commercialized.
A circular holographic video display system reconstructs holographic video. Phase-only spatial light modulators are tiled in a circular configuration in order to increase the field of view. A beam-splitter is used to align the active area of the SLMs side by side without any gap. With the help of this configuration observers can see 3D ghost-like image floating in space and can move and rotate around the object. The 3D reconstructions can be observed binocularly. Experimental results are satisfactory.
Cataloged from PDF version of article.Holography aims to record and regenerate volume\ud filling light fields to reproduce ghost-like 3-D images that are\ud optically indistinguishable from their physical 3-D originals.\ud Digital holographic video displays are pixelated devices on which\ud digital holograms can be written at video rates. Spatial light\ud modulators (SLMs) are used for such purposes in practice; even\ud though it is desirable to have SLMs that can modulate both the\ud phase and amplitude of the incident light at each pixel, usually\ud amplitude-only or phase-only SLMs are available. Many laboratories\ud have reported working prototypes using different designs.\ud Size and resolution of the SLMs are quite demanding for\ud satisfactory 3-D reconstructions. Space–bandwidth product\ud (SBP) seems like a good metric for quality analysis. Even though\ud moderate SBP is satisfactory for a stationary observer with no\ud lateral or rotational motion, the required SBP quickly increases\ud when such motion is allowed. Multi-SLM designs, especially over\ud curved surfaces, relieve high bandwidth requirements, and\ud therefore, are strong candidates for futuristic holographic video\ud displays. Holograms are quite robust to noise and quantization. It\ud is demonstrated that either laser or light-emitting diode (LED)\ud illumination is feasible. Current research momentum is increasing\ud with many exciting and encouraging results
A real-time full-color phase-only holographic display system generates holograms of 3D objects. The system includes a 3D object formed by voxels, an internet-based transmission capability that transmits the object information to the server, a real-time hologram generation unit, and a holographic display unit with incoherent illumination. The server calculates three phase holograms for RGB components using multiple GPUs. The resultant phase holograms are saved into an RGB bitmap image and loaded to the phase-only spatial light modulators (SLMs). SLMs are illuminated uniformly by LEDs, and reconstructed waves are aligned and overlapped by using high precision optics and stages. Experimental results are satisfactory.
An approximation for fast digital hologram generation is implemented on a central processing unit (CPU), a graphics processing unit (GPU), and a multi-GPU computational platform. The computational performance of the method on each platform is measured and compared. The computational speed on the GPU platform is much faster than on a CPU, and the algorithm could be further accelerated on a multi-GPU platform. In addition, the accuracy of the algorithm for single- and double-precision arithmetic is evaluated. The quality of the reconstruction from the algorithm using single-precision arithmetic is comparable with the quality from the double-precision arithmetic, and thus the implementation using single-precision arithmetic on a multi-GPU platform can be used for holographic video displays.
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