Holography for 3D Displays
6.1 Introduction and Overview
Recording media such as photographic films, emulsions, photo-polymers, and also CCDs and LCDs are only able to store intensities of light and not the phase of a light wave. Also, the human eye is only receptive to intensity. D. Gabor [1–3] used the interference of two mutually coherent light waves with different phase angles and the resulting interference pattern to record intensity and phase. The phases, as we shall see, are expressed by a modulation of this pattern. The whole information on beams of light, the magnitude and the phase, is contained in this interference pattern. In Greek holos means whole, from which the denotation hologram for that pattern is derived.
If one of the mutually coherent light waves represents the light reflected and diffracted from a 2D or 3D object and the other light wave, the reference beam, exhibits a known amplitude and phase, then the hologram contains the whole information on the object, even if it happens to be a 3D object. The 3D image can be reconstructed by shining the reference beam or a beam related to it onto the hologram and by perceiving the diffraction beam. That way, the reference beam serves as a reading beam, whereas during the recording of the hologram it was a writing beam. The reconstructed image is a true 3D image in space which the viewer can look at from various perspectives.
The images will be projected by lenses. As lenses are able to perform the inverse ...