New ways to make computer-generated color holograms

Color images can be produced from three computer-generated holograms, one for each of the primary colors. Two basic problems must be solved: scaling the images according to wavelength and avoiding false images. The former can be solved by a computational step, during synthesis of he holograms, or during reconstruction. The latter problem, false images, can be solved by the reconstruction geometry or by using multi-emulsion color film. The wavelentgh-selective absorption of the different layers in color film can be used to selectively absorb light of an undesired color while transmitting light of the desired color at a given point on the film. This effect allows the spatial multiplexing of binary detour-phase holograms. In addition to density variations, there exist corresponding phase variations in color film, particularly Kodachrome II, making onaxis holograms possible. Furthermore, the phase variations can be used to eliminate an undesired color by selectively diffracting it off to the sides. Experimental results are presented.