Digital holography optically generates a hologram, which is then recorded on a CCD camera, and an image is reconstructed using digital techniques. This chapter discusses the converse, i.e., the hologram is digitally generated and the reconstruction is performed optically, a process known as computer-generated holography (CGH). Thus, in CGH, holograms are created by calculations performed by a digital computer. The next step transfers the computer-generated hologram to a transparency by means of a plotting or printing device. Alternatively, the holographic image can be produced by a holographic 3D display (a display that operates on the basis of interference of coherent light) or displayed using a spatial light modulator (SLM), thus bypassing the need to fabricate a “hard copy” of the holographic interference pattern. Consequently, the term “computer-generated holography” is increasingly being used to denote the entire process chain of synthetically preparing holographic light wavefronts suitable for observation. Ultimately, CGH might serve all of the roles of current computer-generated imagery: holographic computer displays for a wide range of applications from CAD to gaming, holographic video and TV programs, automotive and communication applications (e.g., cellphone displays), and many more. In other words, CGH can create images of fictitious objects.
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