4 December 1998 Application of a liquid crystal display as a multilevel quantized phase-mostly filter in a 4-f optical correlator
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Abstract
A twisted nematic liquid crystal display (TN-LCD) from a video projector was characterized for phase modulation. It was found to have a phase modulation of approximately 1.5 to 2(pi) with consistently flat amplitude. Using this knowledge a fast Fourier transformed complex 2D frequency domain image was encoded with 2, 4, 8, and 16 levels of phase modulation. The LCD was then used to display the phase-mostly computer generated (CG) matched filter, known as a kinoform, in the Fourier plane of a 4-f correlator. An intensity modulated LCD was used to display input information to the correlator. Results showed that a CG multi-level phase filter had similar correlation peaks to a CG binary phase filter, but there was a less likely chance of detecting a character or image that was similar to the inverted image used to generate the matched filter. Further study was done with the autocorrelation of images as well as detecting an image amongst other images using an 8 level phase-mostly matched filter.
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Mark Starzomski, Mark Starzomski, Michael Cada, Michael Cada, } "Application of a liquid crystal display as a multilevel quantized phase-mostly filter in a 4-f optical correlator", Proc. SPIE 3491, 1998 International Conference on Applications of Photonic Technology III: Closing the Gap between Theory, Development, and Applications, (4 December 1998); doi: 10.1117/12.328693; https://doi.org/10.1117/12.328693
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