Talk
Abstract:
Seminar
on Industrial Problems
Time-Varying Speckle Patterns, and Application
to Laser Scanners
February
18, 2000
Presented
by:
Sasa Kresic
Symbol Corporation
kresic@symbol.com
570
Vincent Hall
10:10 am
A speckle pattern is a random interference pattern which is
formed when a highly coherent beam is scattered from a rough
surface. As the beam scans across the surface the speckle pattern
changes in time giving rise to random fluctuations in the current
of a photodetector which collects the scattered light. This
phenomenom is called speckle noise, and is of great importance
in laser scanning devices such as barcode readers. The purpose
of this talk is to present the mathematical model of Gaussian
speckle patterns, and to explain how the theory of random processes
can be used in studying spectral properties of speckle noise.
In particular, we will show how an application of the Wiener-Khinchine
theorem yields the distribution of the noise power in the frequency
domain. We shall also discuss the signal-to-noise ratio (SNR)
when the scanning beam moves across a surface of nonuniform
reflectance. We will derive estimates for the lower bound of
SNR for some simple reflectance functions, and explain the implications
of this to laser barcode scanning.
Collaborators: Prof. E. Marom, Tel Aviv University and Prof.
L. Bergstein, Brooklyn Politechnic.
Slides from the IMA Talk
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