Point Efficiency and Signal-to-Background Ratio in Exponential Holograms for Optical Memories

The reconstruction of a point matrix by holograms with an exponential exposure characteristic is exactly calculated in dependence on exposure parameters, geometry, and position of a point in the image field. Linear and nonlinear distortion of the reconstruction is described in terms of the signal-to-background ratio (SBR). The variation of the SBR across the image field is demonstrated for both phase holograms and exponential amplitude holograms. The results, derived for point holograms in optical memories, are also applicable to the more generalized case of holograms of diffuse objects.