300-mm-aperture phase-shifting Fizeau interferometer

A 300-mm-aperture digital phase-shifting Fizeau interferometer (LADI) has b een developed in house for precision metrology of optical components fabric ated by the Optical Workshop at CSIRO Division of Telecommunications and In dustrial Physics. This paper describes the optical and mechanical configura tion of the instrument as well as its calibration and performance character istics. Recent measurements on 250-mm-diam uncoated optical surfaces have c onsistently shown shortterm repeatability of 0.3 nm rms from measurement to measurement and allowed absolute characterization of these surfaces to an accuracy of a few nanometers. (C) 1999 Society of Photo-Optical Instrumenta tion Engineers.