Effects of intensity thresholding on the power spectrum of laser speckle

Spatial-frequency filtering of laser-speckle patterns has proved to be a useful tool in the measurement of the modulation transfer function for focal plane arrays. Intensity thresholding of the laser-speckle patterns offers nearly an order of magnitude savings in digital storage space. The effect of this thresholding on the spatial-frequency power spectral density of the speckle pattern is investigated. An optimum threshold level is found that minimizes distortion of the power spectrum for the classes of speckle data used for modulation transfer function testing.