7 September 2010 Edge enhancement methods based on derivative operations
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Two methods are described for edge enhancement using optical derivative operations. The proposed methods are based on the polarization properties of the twisted-nematic liquid-crystal displays (LCDs). LCDs traduce the image information in changes of the state of polarization of the light, which allows us to generate simultaneously a "positive" and a "negative" (i.e., a contrast-reversed) replica of the digital image displayed on the LCD. In both methods negative and positive replicas are at the same time imagined across a plane. In first case when the negative replica has a lateral differential displacement relative to the original one, an image with enhanced first derivatives along a specific direction is obtained. In the case when the negative replica is low-pass filtered, one obtains the Laplacian of the original image. Unlike the usual Fourier (coherent) image processing, the technique proposed here works with incoherent illumination. Validation experiments are presented.
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Jorge L. Flores, Jorge L. Flores, José A. Ferrari, José A. Ferrari, } "Edge enhancement methods based on derivative operations", Proc. SPIE 7797, Optics and Photonics for Information Processing IV, 779713 (7 September 2010); doi: 10.1117/12.860860; https://doi.org/10.1117/12.860860

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