Double-frequency grating interferometer displacement measurement system

Abstract

The invention discloses a double-frequency grating interferometer displacement measurement system. The system comprises a double-frequency laser device, an interferometer, a measuring grating and an electrical signal processing portion. The measurement system achieves displacement measurement based on optical grating diffraction, the optical doppler principle and an optical beat frequency principle. The double-frequency laser device transmits double-frequency laser, the laser is divided into reference light and measuring light through a polarizing beam splitter, the measuring light transmits into a position of the measuring grating, positive and negative first-order diffraction occurs, diffraction light and the reference light form a beat frequency signal which contains displacement information in two directions at the position of a light detection unit, and linear displacement output is achieved through signal processing. According to the system, the sub-nanometer-grade or even higher grade of resolution ratio and accuracy can be achieved, and horizontal large-stroke displacement and horizontal displacement can be measured at the same time. The system has the advantages of being insensitive to the environment, high in measuring accuracy, small in volume and light in weight. The system serves as a lithography machine ultraprecise workpiece platform position measurement system, the comprehensive performance of the workpiece platform can be improved.

Description

technical field [0001] The invention relates to a grating measurement system, in particular to a dual-frequency grating interferometer measurement system. Background technique [0002] As a typical displacement sensor, the grating measurement system is widely used in many electromechanical equipment. The measurement principle of the grating measurement system is mainly based on the Moiré fringe principle and the diffraction interference principle. As a well-developed displacement sensor, the grating measurement system based on the Moiré fringe principle has become the first choice for displacement measurement of many electromechanical equipment due to its high resolution, high precision, low cost, easy installation and many other advantages. [0003] The lithography machine in semiconductor manufacturing equipment is the key equipment in the production of semiconductor chips. The ultra-precision workpiece stage is the core subsystem of the lithography machine, which is use...

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Problems solved by technology

In the research paper "Design and construction of a two-degree-of-freedom linear encoder for nanometric measurement of stage position and straightness. Precision Engineering 34 (2010) 145-155", the Japanese scholar GAOWEI proposed a single-frequency encoder using the principle of diffraction interference. Two-dimensional grating measurement system, which can realize horizontal and vertical displacement measurement at the same time, but due to the use of single-frequency laser, the measurement signal is susceptible to interference and the accuracy is difficult to guarantee

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