In the past, annular coded aperture images have been recon-structed by correlating an appropriately scaled annulus with the coded image. The basic improvement suggested in this paper is the addition of a linear radial frequency weighting in the Fourier plane. Reconstructions of point and disk objects were simulated with a computer program. The results show the advantage of this modification in the processing scheme. When the assumption is made that the detector is an Anger camera, the resolution obtained with the improved processing of the coded image is equal to that obtained with conventional apertures. An actual object consisting of the letter E was imaged with an annular aperture and a scintillation camera. The reconstruction with and without the improved processing is presented. In addition, the annulus is intermediate between the pinhole and the Fresnel zone plate with regard to both collection efficiency and the number of counts required for a given signal-to-noise ratio (SNR). It therefore offers an improvement over pinhole apertures without demanding the increased count rate and resolution required of detectors when Fresnel zone plate coded apertures are used.
R. G. Simpson,
H. H. Barrett,
J. A. Subach,
H. D. Fisher,
"Digital Processing of Annular Coded-Aperture Imagery," Optical Engineering 14(5), 145490 (1 October 1975). https://doi.org/10.1117/12.7971815