A 300-mm-aperture digital phase-shifting Fizeau interferometer has been dev
eloped in-house for precision metrology of optical components fabricated by
the optical workshop at Telecommunications and Industrial Physics, Commonw
ealth Scientific and Industrial Research Organization. We describe the proc
edures used in the calibration of the instrument. A reference data file rep
resenting the deviations from flatness of the reference surface is generate
d, measurement uncertainty estimated, and aberrations in the instrument ass
essed. Measurements on 250-mm-diameter uncoated optical surfaces have consi
stently shown short-term repeatability of 0.3-nm rms from measurement to me
asurement and allowed for absolute characterization of these surfaces to wi
thin a few nanometers. (C) 2000 Optical Society of America OCIS codes: 120.
3180, 120.3940, 120.6650, 120.5050, 120.4570, 120.4800.