Automatic measurement of surface height with the interferoscope

Abstract

Using a grazing incidence interferometer, the interferoscope, an automatic absolute measurement of a test object surface height can be made by counting the number of interference fringes when varying the surface incident angle. This is accomplished by combining the inter- feroscope with a computer-controlled stepping motor along with an im- age processing system. By transforming the equations describing the interferoscope, the sought depth can be regarded as a ''frequency,'' which can be attained using Fourier transforms or other frequency evalu- ation algorithms. © 1996 Society of Photo-Optical Instrumentation Engineers.