Accession Number : ADP006792

Title :   Photorefractive Deamplification for Artifact Noise Reduction,

Corporate Author : TUFTS UNIV MEDFORD MA ELECTRO-OPTICS TECHNOLOGY CENTER

Personal Author(s) : Khoury, Jehad ; Cronin-Golomb, Mark

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Many optical image processing operations such as edge enhancement may be performed by suitable linear spatial filters. A broader class of operations is made available by extending this technique to nonlinear filters. An example of this is the use of a logarithmic nonlinearity for conversion of multiplicative to additive noise. In this work, we demonstrate that phase preserving thresholding in the Fourier plane which linearly transmits signals above a certain intensity, reduces additive signal dependent noise, such as noise from coherent artifacts, image defects and uniformity noise. Coherent artifact noise, defect noise and film grain noise are often important limitations in the operation of coherent optical processing devices. It can be shown that both of these noise sources contribute a similar spectral effect in the Fourier transform plane: addition of signal dependent noise to the signal transform. This enables a nonlinear optical thresholding mechanism operating in the Fourier plane to separate the relatively intense signal peaks from the noise related smear. This.noise reduction even works with input amplitudes which have a small signal relative to noise. We use the thresholding mechanism of photorefractive two-beam coupling to reduce strong artifact noise in plane wave illumination of a bar chart transparency. There is no noticeable reduction in the resolution of the signal in our measurements. Furthermore, no reference signal is used in this noise reduction technique.

Descriptors :   *IMAGE PROCESSING, *NOISE REDUCTION, *OPTICAL IMAGES, ADDITION, ADDITIVES, ARTIFACTS, AUGMENTATION, CHARTS, CONVERSION, COUPLINGS, EDGES, FILMS, FILTERS, ILLUMINATION, IMAGES, INPUT, INTENSITY, LIMITATIONS, MEASUREMENT, NOISE, OPERATION, OPTICAL PROCESSING, PHASE, PLANE WAVES, PROCESSING, REDUCTION, RESOLUTION, RODS, SIGNALS, TRANSPARENCIES, WORK, COHERENT OPTICAL RADIATION, REFRACTION, SYMPOSIA.

Subject Categories : Acoustics
      Cybernetics

Distribution Statement : APPROVED FOR PUBLIC RELEASE