EXACT MEASUREMENT OF FLAT SURFACE PROFILES BY OBJECT SHIFTS IN A PHASE-CONJUGATE FIZEAU INTERFEROMETER

We propose a method of exact measurement of flat surface profiles in a phase-conjugate Fizeau interferometer. Aberration of lenses causes an undesirable phase distribution in the interference signal of the phas e-conjugate Fizeau interferometer. To eliminate this phase distributio n, we shift the object in two directions orthogonal to each other and we get difference values of the surface profile of the object. Additio nal displacements of the object surface involved in the shifts lead to some small errors in the difference values. We estimate an exact surf ace profile by solving the difference equations. Characteristics of th e method are made clear through computer simulations and measurements of a 40-mm-diam flat mirror.