Analysis on Combination of Different Wavelengths in Surface Roughness Measurement by Polychromatic Laser Speckle Patterns

Based on the method of polychromatic speckle autocorrelation measuring surface roughness, this paper discussed the influence of the combination of different wavelengths on speckle patterns and speckle elongation ratio when rough surface and polychromatic speckle patterns were simulated. The results show that the smaller the difference of wavelengths combination is, the further peak of the speckle elongation ratio is from the speckle field centre, for the same surface roughness. And the wider area of speckle elongation effects extends. Therefore, influence of combination of wavelengths on measurement precision should be taken into consideration during measuring process.