A method of generating reference wave in interferometric measurement with multiple imaging sensors

Phase-shifting digital holography is a convenient method to measure small 3D displacement distributions on the surface of an object. More than three independent sensitivity vectors are theoretically necessary to obtain a 3D displacement. In general, three incident waves are used to obtain three sensitivity vectors. However, the optical system becomes complicated. Therefore, to simplify the optical system, authors have developed a method to use multiple imaging sensors instead of using multiple incident waves. In this paper, a method of generating reference waves using a flat glass plate and multiple imaging sensors for interferometric measurement was proposed. The calibration method and the calculation method to obtain 3D displacement using multiple imaging sensors were also proposed. The evaluation was performed by measuring the displacement of a flat plate moved with a 3-axis PZT stage using phase-shifting digital holography. The results showed that the proposed method was effective.