Abstract

The theoretical information storage capacity of conventional holographic memories has been analyzed by several workers and is extended in this paper to the holographic associative memory utilizing phase conjugate mirrors (PCMs). Macovski has performed an analysis for the thin hologram. He found for planar objects that, if the hologram space-bandwidth product (SBP) is n², the number of resolvable object points N is n²/4, assuming that an off-axis reference beam is used to spatially offset the reconstructed image. Extending his analysis to our PCM-based associative memory, this SBP can be divided among M stored objects, each having n²/4M resolvable points and each associated with a unique reference. For 3-D objects and plane wave references, N = 11/768 n³. (N can be greater than n² because of the analog nature of the hologram.) Jannson has performed a similar analysis for the thick hologram case which includes the effects of the Bragg condition and the finite resolution of the hologram medium. In both the thin and thick hologram cases the storage capacity of the associative memory is further limited by the effective aperture of the PCM. This limits the range of reference beams and the degree to which the storable SBP can be divided among separate stored objects.

© 1986 Optical Society of America