Measurement of moving objects with phase-shifting digital holography using liquid crystal retarder

We propose a phase-shifting digital holography (DH) method that uses a liquid crystal (LC) retarder for use in the measurement of moving objects. Because LCs are birefringent, they can be used as waveplates for phase-shifting operations. In addition, the phase retardation can be adjusted by varying the LC drive voltage. Mechanical operations are unnecessary in phase shifting when using LCs, but fast interference fringe measurements are possible. The proposed method can be realized by incorporating the LC retarder into a conventional interferometer and is both simple and inexpensive. We performed experiments to verify the effectiveness of the proposed method and confirmed that the method is effective for imaging of the complex amplitude distributions of moving objects.