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Proceedings Paper

Speckle contrast measurement with low light levels and imperfect laser illumination
Author(s): J. W. Goodman; Yiping Feng; Robert Aymeric
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Paper Abstract

The contrast of a speckle pattern, defined as the ratio of the standard deviation of intensity to the mean intensity, is an important parameter that can yield useful information in vibration analysis, and surface roughness measurement. It is also of inherent interest in the measurement of scattering by coherent X-rays. Under some circumstances, the light levels at which contrast measurements must be made are low, and the measurement of speckle fluctuations is complicated by the presence of noise associated with discrete detected photoevents. In addition, the measurements are made over a finite integration time and a finite integration area, so it is the contrast of the integrated intensity that is of interest. The goal of this paper is to explore the effects of both photoevent noise and source fluctuations on the measurement of speckle contrast. Thus in themost general case, there are three sources of randomness, source fluctuations, random scattering and photoevent fluctuations. Partial motivation for the investigation is understanding the photoevent statistics and speckle count contrast for synchrotron and fee-electron laser sources.

Paper Details

Date Published: 3 November 2011
PDF: 11 pages
Proc. SPIE 8011, 22nd Congress of the International Commission for Optics: Light for the Development of the World, 801165 (3 November 2011); doi: 10.1117/12.902323
Show Author Affiliations
J. W. Goodman, Stanford Univ. (United States)
Yiping Feng, SLAC National Accelerator Lab. (United States)
Robert Aymeric, SLAC National Accelerator Lab. (United States)


Published in SPIE Proceedings Vol. 8011:
22nd Congress of the International Commission for Optics: Light for the Development of the World

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