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On the basis of our previous studies on measurements of surface roughness properties using the average speckle contrast, we have actually applied a speckle technique to measure the fine scale roughness of various metal surfaces produced with different finishing processes. The average contrast of speckle patterns produced in the far-field region of the illuminated metal surfaces has been measured for these samples as a function of the illuminated spot width of the laser light over the object surface and is found to have a relation with their CLA (center line average height) roughness. Measurements of surface roughness now become possible for metal objects having various surface profiles by investigating the average contrast variation of speckle intensity distributions as a function of the illuminated spot width of the laser light.
Fujii et al. (1977) studied this question.