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Proceedings Paper

Optical Processor For The Very Large Array (VLA) Radiotelescope: Encoding-Dependent Errors
Author(s): J. R. Fienup; L. E. Somers
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Paper Abstract

An optical Fourier transform processor converts visibility data at its input to a sky brightness function at its output. Scattered light and spurious terms resulting from the method of encoding the complex visibility function as a real-valued and nonnegative transmittance result in errors in the processor output. In this paper, we discuss the degree to which each of these undesired terms degrades the signal-to-noise ratio of the output for different encoding methods and classes of images. We suggest alternative methods of encoding the input that greatly reduce the errors. Two particularly powerful methods of minimizing noise are "complementary weighting" and "bias equalization". Two data dependent parameters are found to be most important: (1) the ratio of the mean-squared visibility magnitude to the square of its maximum, and (2) the ratio of the squared maximum of the brightness function to its mean squared value.

Paper Details

Date Published: 22 August 1980
PDF: 18 pages
Proc. SPIE 0231, 1980 Intl Optical Computing Conf I, (22 August 1980); doi: 10.1117/12.958833
Show Author Affiliations
J. R. Fienup, Environmental Research Institute of Michigan (United States)
L. E. Somers, Environmental Research Institute of Michigan (United States)


Published in SPIE Proceedings Vol. 0231:
1980 Intl Optical Computing Conf I
William T. Rhodes, Editor(s)

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