THREE-DOF HETERODYNE GRATING INTERFEROMETER DISPLACEMENT MEASUREMENT SYSTEM

摘要

A three-DOF (Degree of Freedom) heterodyne grating interferometer displacement measurement system comprises a dual-frequency laser (1), a grating interferometer (2), a measurement grating (3), a receiver (4) and an electronic signal processing component (5); the grating interferometer (2) comprises a polarizing beam splitter (21), a reference grating (22) and refraction elements (23, 24); the measurement system realizes displacement measurement on the basis of grating diffraction, the optical Doppler Effect and the principle of optical beat frequency. After dual-frequency laser light which exits from the dual-frequency laser (1) enters the grating interferometer (2) and the measurement grating (3), four paths of optical signals are output to the receiver (4) and then to the electronic signal processing component (5). Three linear displacements can be output by the system when the grating interferometer (2) and the measurement grating (3) perform a three-DOF linear relative motion. The measurement system can reach the level of sub-nanometer and even higher resolution and precision, and can measure three linear displacements at the same time. The measurement system has the advantages of being environmentally insensitive, high in measurement precision, small in size, light in weight and the like, and is capable of improving the overall performances of an ultra-precision stage of a lithography machine when serving as a position measurement system for this stage.