Comparison of coded aperture imaging systems containing zone plate and random-phase code functions

Coded aperture imaging systems provide an alternative to the conventional pinhole camera imaging system normally used for producing images of gamma-ray and x-ray emitting objects. The coded aperture system uses a large, highly structured aperture in place of the single pinhole aperture, so that the resulting image is a complex pattern of overlapping shadows, produced by the convolution of the aperture transmittance function with the object radiance distribution function. When the aperture transmittance function is properly chosen, it is possible to use a second imaging step to obtain the desired image of the original object radiance distribution. The use of a coded aperture system and its two-step imaging process has two important advantages over the conventional, pinhole imaging system with its single-step imaging process. First, for objects which consist of non-overlapping point sources, such as star fields, the coded aperture imaging system offers greater efficiency and increased signal-to-noise ratio. Second, for both point sources and extended objects, the coded aperture imaging system records three-dimensional information from a single view of the object