PHOTOREFRACTIVE 2-BEAM COUPLING OPTIMAL THRESHOLDING FILTER FOR ADDITIVE SIGNAL-DEPENDENT NOISE-REDUCTION

Computer simulations of photorefractive thresholding filters for the r eduction of artifact or dust noise demonstrate an increase in signal-t o-noise ratio (SNR) of 70% to 95%, respectively, of that provided by t he Wiener filter for inputs with a SNR of approximately 3. These simpl e, nearly optimal filters use a spectral thresholding profile that is proportional to the envelope of the noise spectrum. Alternative nonlin ear filters with either 1/v or constant thresholding profiles increase the SNR almost as much as the noise-envelope thresholding filter.