Study on phase retrieval of a single closed fringe interferogram in radial shearing interferometer for aspheric test

Abstract

The radial shearing interferometer that is immune to vibration and the spatial phase modulation technique that can retrieve the phase from a single interferogram can be used for precise measurement of aspheric surfaces. However, as a carrier is needed to be introduced in the system to keep the fringes open, the spatial phase modulation technique generally leads to a great increase in the density of the fringes. A novel method that uses just one frame of the interferogram and need not introduce any spatial carrier in the interferometer is proposed in the paper. To demodulate the closed interferograms generated in the system, a regularized phase-tracking technique that can be used for a single open or closed fringe pattern is employed to recover the phase map. Actually the presented method can also be applied in many other cases, for example flow visualization. Both computer simulation and experimental result have demonstrated the validity and efficiency of the proposed method.