Abstract: An optical scanning technique comprising three laser interferometers and one autocollimator to measure a large flat mirror profile with high accuracy is described. The flat mirror profile and its measurement uncertainty are reconstructed by an application of simultaneous linear equations and least-squares method. The whole measurement process is numerically modeled by the computer simulation. Measurement uncertainties of the flat bar mirror profile are evaluated for different sampling numbers of the flat bar mirror. Moreover, a prototype of optical measurement system based on micro coordinate measuring machine platform is built. The experiment shows that the measurement technique successfully achieves the profile measurement of 100 mm flat mirror and repeatability of measurement accuracy within the range of ±20 nm. Comparing with the results measured by Zygo whitelight interferometer, this technique can achieve profile measurement in nanometer accuracy.

Key words: Autocollimator, Large flat mirror profile, Laser interferometer, Scanning measurement