<title>Photopolymer elements for an optical correlator system</title>

Abstract

An optical correlator system that employs photopolymer materials fabricated to form holographic optical elements and multiple matched filter memories is described. The photopolymer media offer some distinct advantages over other materials; in particular, these are in situ operations, high-efficiency one-step dry chemistry, and ease of operation. By comparison, silver-halide media in general require off-line multistep wet chemistry processing which is slow and inconvenient; the resultant holographic element exhibits low efficiency. To be sure, the use of photopolymers for holographic elements has its shortcomings, being several orders of magnitude less sensitive, with spatial frequency limits at the low end and somewhat limited wavelength operation. In this paper a comparison is made of two Van der Lugt architectures, one being an all-photopolymer element system and the second a benchmark correlator system employing silver-halide materials. Representative correlation objects were prepared and processed for each medium. This was followed by a series of test measurements for peak levels, signal-to-clutter, and tracking response. For a wider range of applications, filter impulse responses are examined and compared for the classic Van der Lugt filter and binary-phase-only-filter-type elements. It is shown that when care is taken in processing, the photopolymers can offer an extremely convenient and effective medium for in situ recording of both amplitude and phase filter elements, while providing significantly more versatility than the silver halides and, generally, with higher efficiency and system throughput.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.