Optimization of parameters in matched spatial filter synthesis

Optical generation of a circular harmonic filter for rotation and translation invariant optical pattern recognition

A new method to generate a circular harmonic filter with both rotation and translation invariance is described, which is based on a phase-shifted double-exposure (PSDE) technique. An expression for the peak correlation intensity at the origin of the correlation plane as a function of target orientation for the PSDE filter is derived. Experimental results confirming the theoretical predictions are provided.

Light utilization in optical correlators

An analysis is made of the overall light efficiency in a coherent optical correlator. The results are applied to a matched filter and an inverse filter. Kogelnik's coupled wave theory is applied to analyze the diffraction efficiency of a filter recorded on a high-efficiency phase medium such as dichromated gelatin. Experimental results are presented for a matched filter and out-of-focus spatial filter, and the former is compared to the theory with good agreement.

Equalizing and coherence measure correlators

A correlator is described that combines optical and electronic processing. The optical section is the first Fourier transform taking stage of a joint transform correlator; its output is electronically processed by a modified spectrum analyzer. Increased flexibility and various processing operations beyond those normally possible in an optical system result.

Aerial reconnaissance film screening using optical matched-filter image-correlator technology

The use of aerial photography for reconnaissance and the relatively high costs associated with human photo interpreters are responsible for the continuing interest in the development of automated screening systems. An optical matched-filter image-correlator (OMFIC) system has the inherent capability to perform this task, especially when expanded to include multiple holographic lens-matched filter memory banks. An OMFIC system was investigated in detail, and a projection of its performance for the screening mission was made. This showed that a high probability of detection can be obtained at a low false alarm rate. For example, a memory bank of 23 (orientational) views of an M-60 tank would enable a probability of detection of 98% to be obtained with 1.4% false targets in a complex village scene even though the image scale changed by as much as +/-9.5% (linear scale).