Laser-diode phase-shifting interferometer operating at a frame rate

We have developed a laser-diode phase-shifting interferometer that can capture frame-rate phase-shifted interferograms on a video tape with a high capacity of their storage. A number of the video flame is simultaneously recorded on an audio track of the video tape. The injection-current variation of laser diode in a four-step manner is synchronized with the field pulse of a CCD camera to produced pi/2-step phase shifts at a frame rate. An intensity distribution of the interferogram on any frame can be obtained from the video tape with a frame memory by utilizing the recorded frame number. The four successive phase-shifted interferograms are used to calculate a distribution of dynamic phase by a phase-extraction algorithm.