Comment: absolute measurement of roughness and lateral-correlation length of random surfaces by use of the simplified model of image-speckle contrast.
This comment demonstrates several errors in the derivation of speckle contrast and corresponding measurements reported by Cheng et at. (Appl. Opt. 41, 4148 (2002)] for a 4f optical system. In particular, the theoretical derivation is wrong: It is used outside of its domain of validity, and the experimental results do not support the theoretical analysis.
Electronics and Photonics Laboratory, The Aerospace Corporation, P.O. Box 92957, Los Angles, California, USA.
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