Accurate Profile Measurement by an Interferometer

摘要

For the pupose of improving measurement accuracy in interferometry, a lot methods have been proposed to separate the form error in the reference optics from that in the test optics. The best known one is the three-plate method~(1)(2) in which multiple measurements to three plates combined in pairs are carryed out. The unknown form error in the test optics can be evaluated through the calucation of the measurement resutls. However, multiple measurements across several lines and the cobination of these individual sets of data are considered to lead to a loss of precision. In another method proposed by Schulz and Elssner~(3), three positions, including the basic position, rotated position and cat's eye position, were used between the reference optics and the test optics. With a comprebensive calcualtion of data at these positions, the unknown form error in the test optics can be evaluated in spite of that in the reference surface.