A fast automated optical surface measurement system.

摘要

An experimental surface measurement system based on the Twyman-Green interferometer was developed. This system uses three main components: an interferometer, digitization hardware and analysis software. The software consists of an automated interferometery analysis routine and a graphical user interface.; Automated interferometery analysis methods were examined under three categories: Direct, Temporal Phase Shifting, and Spatial Phase Shifting. A comparison of the strengths and weaknesses of each approach was made. The Spatial Phase Shifting approach was selected for this system and was explored in more detail. Two approaches to Spatial Phase Shifting: the Fast Fourier Transform and Electronic Phase Shifting methods were investigated further. Software was developed based on the Electronic Phase Shifting method.; Experiments demonstrate the overall accuracy of the measurement system. Using this system, surfaces that are up to 60 millimeters in diameter can be measured to surface accuracies of +/-40 nanometers. Finally, the effects of optical aberrations, external disturbances, and computational error on the system were investigated.