<title>A Rationale For Optimal Coded Aperture Design</title>

Abstract

The distribution of noise in coded aperture images is known to depend in a complex manner upon the encoding technique, the decoding technique and upon the object distribution. We have examined the S/N characteristics of a classs of, planar, pseudorandom, time -modulated coded apertures in order to optimize the aperture design for a defined object distribution.Relative standard deviation (RSD) in the reconstructed image is studied both theoretically and by computer simulation.Results are shown for uniform, planar source distributions of varying size as a function of mean code plate transmission and aperture hole spacing.In each case, effects of solid angle and finite geometry are taken into account. For simplicity, image reconstruction is accomplished by backprojection.For a source size equal to 20% of a full field flood, a code of 12% mean transmission gives a near optimum S /N.The RSD with this code for an on -axis image element is equal to .33 of that for a single scanning pinhole covering an identical field of view. Even for a 100% field flood an optimum code exists which has a mean transmission of nearly 4 %. The RSD in this case is smaller compared to the scanning pinhole by a factor of .85.