Doppler phase-shifting interferometry and holography

A new technique is proposed, in which a phase-shifting algorithm utilizing the optical Doppler effect and a high-speed CMOS camera are employed. In many phase-shifting algorithms, the phase distribution of the object is calculated by using a few reference phases with equal phase difference. In our proposed method, a reference mirror is moved continuously or randomly to make phase shift based on the Doppler effect. The phase distribution of the object is calculated by Fourier transforming the time-depending interference fringe data. If the reference phase shift is equally introduced to all the data points in the interference fringe image, the phase distribution at the peak frequency component in the Fourier spectrum gives the phase distribution of the object. Since a few hundred or more images were required in this method, a CMOS camera with a high frame rate of 500fps was used.