Surface roughness measurements with an optical Fourier spectrum analyzer.

The far-field pattern of light scattered by a small rough metallic surface area is obtained with a coherent optical system and used to quantify roughness measurements of machined surfaces. The distribution is usually anisotropic due to tooling marks. A cylinder lens forms a 1-D transform at favorable angular orientations about the optic axis to circumvent this problem and provides useful spectrum averaging. The integrated Gaussian curve fits to experimentally observed scattered light patterns from individual roughness samples yield an empirical linear relation between a Gaussian width parameter and average roughness height.