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We present the design of a bipolar composite filter (BCF) by a simulated annealing algorithm. By minimizing the energy function of the system, we construct an out-of-plane rotation-invariant bipolar filter. We show that the BCF offers high pattern discrimination capability and can easily be implemented with an electronically addressed spatial light modulator.
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Correlation experiments for the images used in the proposed setup indicate that nonlinear compression of the joint power spectrum may be necessary to produce good correlation performance and a peak-to-sidelobe ratio of larger than unity.
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Key performance characteristics of an optically addressed ferroelectric liquid-crystal spatial light modulator have been measured and compare favorably with those of other commercially available spatial light modulators. Several characteristics that are important for optical pattern recognition, including imaging resolution, visibility, and response time, are discussed. Maximum resolution was measured to be 40 line pairs/mm at an imaging rate of 60 Hz. This differs from previously published results [Appl. Phys. Lett. 55, 537 (1989)], primarily because the device was operated so that good sensitivity was obtained with moderate illumination while the high resolution of the device was retained.
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An optically addressed ferroelectric liquid crystal spatial light modulator has been verified as a suitable input and frequency plane modulator in a joint transform correlator.
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The recent production of a deformable mirror device (DMD) spatial light modulator has naturally led to techniques of using this device in popular optical correlator architectures. In this paper, the DMD is used in both joint transform and VanderLugt arrangements. In some cases, the DMD is used as the input device to a single stage joint transform correlator, and in other cases it is used as the filter device in a VanderLugt correlator. A liquid crystal TV is also used for real time addressing of filters displayed on the DMD.
