Downie J D
Appl Opt. 1995 Jul 10;34(20):3896-903. doi: 10.1364/AO.34.003896.
Images with signal-dependent noise present challenges beyond those of images with additive white or colored signal-independent noise in terms of designing the optimal 4-ƒ correlation filter that maximizes correlation-peak signal-to-noise ratio, or combinations of correlation-peak metrics. Determining the proper design becomes more difficult when the filter is to be implemented on a constrained-modulation spatial light modulator device. The design issues involved for updatable optical filters for images with signal-dependent film-grain noise and speckle noise are examined. It is shown that although design of the optimal linear filter in the Fourier domain is impossible for images with signal-dependent noise, proper nonlinear preprocessing of the images allows the application of previously developed design rules for optimal filters to be implemented on constrained-modulation devices. Thus the nonlinear preprocessing becomes necessary for correlation in optical systems with current spatial light modulator technlogy. These results are illustrated with computer simulations of images with signal-dependent noise correlated with binary-phase-only filters and ternary-phase-amplitude filters.
对于具有信号相关噪声的图像而言，在设计能使相关峰值信噪比或相关峰值指标组合最大化的最优4-ƒ相关滤波器时，其所面临的挑战要超过具有加性白色或彩色信号无关噪声的图像。当要在受约束调制空间光调制器设备上实现该滤波器时，确定合适的设计会变得更加困难。本文研究了用于具有信号相关胶片颗粒噪声和散斑噪声图像的可更新光学滤波器所涉及的设计问题。结果表明，尽管对于具有信号相关噪声的图像，在傅里叶域中设计最优线性滤波器是不可能的，但对图像进行适当的非线性预处理可以应用先前开发的最优滤波器设计规则，以便在受约束调制设备上实现。因此，对于采用当前空间光调制器技术的光学系统中的相关性而言，非线性预处理变得必不可少。这些结果通过对具有信号相关噪声的图像与仅二元相位滤波器和三元相位幅度滤波器进行相关性的计算机模拟得到了说明。
