Abstract

A harmonic ac interferometer was built by interfacing a Macintosh computer to modulation and data collection electronics as well as a translation stage assembly. The phase sample to be measured was mounted on the stage and translated through the test arm of the interferometer. This configuration resulted in accurate measurements that were independent of the quality of the optics, as well the alignment of the interferometer cavity. The lateral dimension of the phase sample under test was limited only by the range of motion of the translation stage and not by the aperture of the interferometer. An electronic fringe counting scheme was used to keep track of fringes during movement of the sample, and the stage was stopped at predetermined step sizes in order for accurate phase measurements to be made.

© 1989 Optical Society of America