DISPLACEMENT MEASUREMENT SYSTEM FOR TWO-DEGREE-OF-FREEDOM HETERODYNE GRATING INTERFEROMETER

摘要

A displacement measurement system for a two-degree-of-freedom heterodyne grating interferometer, comprising a double-frequency laser (1), a grating interferometer (2), a measurement grating (3), a receiver (4) and an electronic signal processing component (5), wherein the grating interferometer (2) comprises a polarizing spectroscope (21), a reference grating (22) and dioptric elements (23a, 23b, 23c). The measurement system achieves the displacement measurement on the basis of the grating diffraction, the optical Doppler effect and the optical beat frequency principle. After the double-frequency laser emitted from the double-frequency laser (1) is incident onto the grating interferometer (2) and the measurement grating (3), two paths of optical signals are output to the receiver (4), and then to the electronic signal processing component (5). When the grating interferometer (2) and the measurement grating (3) conduct two-degree-of-freedom linear relative motion, the system can output two linear displacements. The measurement system can achieve sub-nanometer or even higher resolution and accuracy, and can simultaneously measure two linear displacements. The measurement system has the advantages of insensitivity to the environment, high measurement accuracy, a small volume and light weight, and can improve the comprehensive performance of a workpiece stage as a position measurement system for an ultra-precise workpiece stage of a photoetching machine.