Real-time fringe analyzer and its applications to active optics

A fringe analyzer has been developed which delivers phase distribution from an interference pattern having carrier fringes at the video rate. It is based on the generation of three phase- shifted moire fringe patterns through electronic multiplication with computer generated reference patterns having mutual phase shifts and subsequent phase calculation. After the principle and specifications of the analyzer are presented, applications to feedback control of a liquid crystal spatial phase modulator, measurements of large mirrors using synthetic aperture interferometry, and active phase shifting speckle interferometry are reported.