Plane grating interferometer displacement measurement system

Abstract

The invention provides a plane grating interferometer displacement measurement system comprising a single frequency laser, a beam splitter, an acousto-optic modulator, a grating interferometer, a plane grating, a receiver, an electronic signal processing part, an optical fiber coupler and a frequency synthesizer. The grating interferometer comprises a polarizing beam splitter, a dioptric element,a retro-reflector and a quarter-wave plate. The measurement system realizes displacement measurement on the basis of grating diffraction, the optical Doppler effect and the principle of optical beat frequency. When the grating interferometer and the plane grating perform two-degree-of-freedom linear relative motion, the system can output two linear displacement. According to the measurement system, sub-nanometer and even higher resolution and accuracy can be realized and two linear displacement can be simultaneously measured; and the measurement system has the advantages of high measurement accuracy and simple structure and acts as the photoetching machine ultra-precision workpiece table position measurement system to enhance the integrated performance of the workpiece table.

Description

technical field [0001] The invention relates to a displacement measuring system of a plane grating interferometer, in particular to a displacement measuring system of a plane grating interferometer used for measuring the displacement of a workpiece table of a lithography machine. 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 long measuring range, low cost, and easy installation and adjustment, but the accuracy is usually on the order of microns, which is common for general industrial applications. [0003] The lithogra...

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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", Japanese scholar GAOWEI proposed a single encoder using the principle of diffraction interference. Frequency 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

Chinese patent document application numbers 201210449244.9 (application date November 09, 2012) and 201210448734.7 (application date November 09, 2012) respectively disclose a heterodyne grating interferometer measurement system, and the readings in the two interferometer measurement systems The head structure uses a quarter-wave plate to change the polarization state of the beam, the optical structure is complex, and the non-ideality of the optical components will lead to measurement errors

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