A research on compact short-distance grating interferometer based on ridge prism

Grating interferometer has great application potential in precision measurement. In view of its miniaturization, a compact installation based on ridge prism is adopted in this paper, and the interference signal with 90° phase is obtained by numerical calculation. The specific scheme is to divide the laser beam through the splitting prism to make the two beams diffract at the reference two-dimensional grating and the measurement two-dimensional grating respectively. The four beams of diffracted light are collimated through the ridge prism. The collimated two groups of beams produce interference at the splitting prism, and the interference signal is received by the photodetector. Differing from the conventional method, the second group of 90° phase interference light data is obtained by derivation. Through the solution of the interference signal, the displacement in X and Z directions of the measurement grating can be deduced. Experiments were carried out to verify the measurement accuracy of the grating interferometer. The moving speed of scale grating is 1μm/s ,distance is 0.5 mm and the sampling frequency is 100 Hz. Repeatability and measurement accuracy of the grating interferometer are obtained. The repeatability measurement error is less than 0.5%. Specially, this method benefits for simple installation, high precision, high stability and low energy loss. It has high practical value in industrial production. Precision measurement of two degrees of freedom of short-distance displacement is realized and error of the measurement results is analyzed.