There is often confusion among the general public between holograms and the type of contemporary 3D images seen in movie theaters, in which viewers from each side of the theater see the same image on the screen. As astonishing as these 3D effects are, the technologies used are typically based on either polarization stereoscopy (the technique currently used in cinemas and 3D television), digital image fusion, or 2D semitransparent screens. These techniques have little to do with holography, which is based on the reproduction of not only the amplitude but also the phase of light by diffraction. These 3D images can have depth but are typically filmed from a single perspective. On the other hand, for a viewer moving around a hologram, the appearance of the object changes continuously and smoothly as the viewer’s perspective changes, as if the object is real. A standard 3D movie camera (which actually uses two cameras) captures light scattered from an object at two different angles, one for each eye, from a single perspective. However, in the real world, light reflects from objects at an infinite number of angles. For a 3D television viewing experience to be maximally realistic, it must be autostereoscopic (requiring no glasses), present continuous parallax (rather than just stereopsis), and realistically represent other perceptual depth cues, such as proper visual accommodation (focusing) and vergence. The display technology most likely able to offer these features is holographic television. Some recent 3D display technologies, though not necessarily holographic, have been commercialized due to the increasing demand from the public for autostereoscopic 3D TVs, 3D games, and mobile devices equipped with 3D displays. This chapter systematically reviews various 3D display technologies. Byoungho Lee et.al. and Jason Geng have recently published excellent review articles concerning many state-of-the-art 3D display technologies, which will be summarized in this chapter.
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