OPTICAL CORRELATION OF IMAGES WITH SIGNAL-DEPENDENT NOISE USING CONSTRAINED-MODULATION FILTER DEVICES

Images with signal-dependent noise present challenges beyond those of images with additive white or colored signal-independent noise in term s of designing the optimal 4-f correlation filter that maximizes corre lation-peak signal-to-noise ratio, or combinations of correlation-peak metrics. Determining the proper design becomes more difficult when th e filter is to be implemented on a constrained-modulation spatial ligh t modulator device. The design issues involved for updatable optical f ilters for images with signal-dependent film-grain noise and speckle n oise are examined. It is shown that although design of the optimal lin ear filter in the Fourier domain is impossible far images with signal- dependent noise, proper nonlinear preprocessing of the images allows t he application of previously developed design rules for optimal filter s to be implemented on constrained-modulation devices. Thus the nonlin ear preprocessing becomes necessary for correlation in optical systems with current spatial light modulator technology. These results are il lustrated with computer simulations of images with signal-dependent no ise correlated with binary-phase-only filters and ternary-phase-amplit ude filters.