Fabrication of an Optical Heterodyne Profilometer

Abstract

An optical heterodyne profilometer was fabricated for the measurement of surface roughness. Briefly, when two beams of slightly different frequencies are reflected from two different points on the surface, the phase of the resulting sinusoidal interference signal is related to the height difference between the two points, whose absolute value is estimated by comparing it with the phase of a reference signal, but no reference surface is involved.1