Surface roughness measurement using white light speckle.

An experimental investigation is made of a technique for measurement of surface roughness. A speckle pattern is formed near the image plane of a lens in spatially coherent light having a broad spectral bandwidth. The contrast of the speckle is found to be related to surface roughness when the roughness and the coherence length of illumination are comparable in magnitude. Implementation techniques are discussed and results shown that indicate good correlation with profilometer measurements for a wide range of roughness values produced with a variety of finishing procedures.