EFFECT OF RETROREFLECTION ON A FIZEAU PHASE-SHIFTING INTERFEROMETER

Phase errors in a Fizeau phase-shifting interferometer caused by multiple-reflected beams from a retroreflective optics, such as a comer cube and a right-angle prism, are studied. Single- and double-pass configurations are presented, and their measurement results are compared. An attenuator is not needed in a double-pass configuration because light is reflected by the retroreflectve optics twice and the reference surface once and hence the intensities match. It is more accurate to test a comer cube or a right-angle prism in a double.pass configuration than in a single-pass configuration. Simulations and experimental results are presented.