| Summary: | 碩士 === 逢甲大學 === 通訊工程所 === 93 === This paper is to discuss the effect of noise and analyze nonlinearity of the optical correlator on detection procedure of the optical watermark system (OWS). In the digital holographic watermarking scheme, the watermark is constructed by an optically holography architecture, and the watermarked hologram is embedded into a cover image. For the Detection, the optical correlator is used to detect the embedded watermark based on the correlation of the watermarked image and the authorized mark pattern. Given a sharp correlation, one can claim that the watermarked image has a correct mark. Conversely, the mark is absence.
This thesis consists of two purposes: one is to discuss the noise effect of the optical watermark system and the second is to consider the influence of the nonlinear device of the system. When the watermarked image interrupted by various type of noises such as additive white noise、occlusion of one part of the image and quantization, we develop an statistical model for analyzing the output correlation under the noise environment. Furthermore, since the watermarked image is a wide range gray-level image, the nonlinear SLM effect should consider under this structure. Thus, we derive the nonlinear relationship for the input and output of the SLM and use it to consider output correlation under the nonlinear environment. Experimental results is demonstrated the performance of the optical watermark system under the noise corruption and the nonlinear effect of the optical device in the system.
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