Two beam interferometer with multiple scanning of reference beam - achieves compensation of errors by matching angle of incidence to number scans

摘要

The two-beam interferometer compensates errors due to scanning table movement, thermal distortion and structural vibrations. The reference beam is moved over the surface 2n times, where n is 1,2... and whilst the angle of incidence is maintained as arc cos (1/2n). An object beam and reference beam are produced by a beam divider (6). The object beam is incident perpendicularly on the object (10) and the reference beam at an angle. The reflected beams are brought together to produce interference. USE/ADVANTAGE - E.g. for use in surface measurement, interferometer uses new method of compensating changes in path length between measurement object and interferometer head.