Comparison Of Fresnel Zone Plates And Uniformly Redundant Arrays

E. E. Fenimore; T. M. Cannon; E. L. Miller

doi:10.1117/12.956690

7 December 1978 Comparison Of Fresnel Zone Plates And Uniformly Redundant Arrays

E. E. Fenimore, T. M. Cannon, E. L. Miller

Proceedings Volume 0149, Digital Image Processing II; (1978) https://doi.org/10.1117/12.956690
Event: 22nd Annual Technical Symposium, 1978, San Diego, United States

Abstract

Several imaging systems in laser fusion, a-beam fusion, and astronomy employ a Fresnel zone plate (FZP) as a coded aperture. The recent development of uniformly redundant arrays (URAs) promises several improvements in these systems. The first advantage of the URA is the fact that its modulation transfer function (MTF) is the same as the MTF of a single pinhole, whereas the MTF of an FZP is an erratic function including some small values. This means that if inverse filtering is used, the URA will be less susceptible to noise. If a correlation analysis is used, the FZP will produce artifacts whereas the URA has no artifacts (assuming planar sources). Both the FZP and URA originated from functions which had flat MTFs. However, practical considerations in the implementation of the FZP detracted from its good characteristics whereas the URA was only mildly affected. The second advantage of the URA is that it better utilizes the available detector area. With the FZP, the aperture should be smaller than the detector in order to maintain the full angular resolution corresponding to the thinnest zone. The cyclic nature of the URA allows one to mosaic it in such a way that the entire detector area collects photons from all of the sources within the field of view while maintaining the full angular resolution. If the FZP is as large (or larger) than the detector, all parts of the source will not be resolved with the same resolution. The FZP does have some advantages, in particular its radial symmetry eases the alignment problem; it has a convenient optical decoding method; and higher diffraction order reconstruction might provide better spatial resolution.

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E. E. Fenimore, T. M. Cannon, and E. L. Miller "Comparison Of Fresnel Zone Plates And Uniformly Redundant Arrays", Proc. SPIE 0149, Digital Image Processing II, (7 December 1978); https://doi.org/10.1117/12.956690

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