Five-degree of freedom heterodyne grating interferometry system

Abstract

The invention provides a five-degree of freedom heterodyne grating interferometry system, which comprises a single-frequency laser, an interferometer mirror group, a measurement grating and multiple optical fiber beams, wherein the single-frequency laser is used for emitting single-frequency laser, and the single-frequency laser can be divided to a beam of reference light and a beam of measurementlight; the interferometer mirror group and the measurement grating are used for forming reference interference signals and measurement interference signals from the reference light and the measurement light; and the multiple optical fiber beams receive measurement interference signals and reference interference signals respectively, and multiple multimode optical fibers exist in each optical fiber beam for receiving interference signals of different positions on the same plane. The measurement system of the invention has the advantages of being insensitive to the environment, small in size, light in weight, convenient to arrange and the like; multiple five-degree of freedom interferometry systems are adopted for arrangement, the redundant information is used to realize six-degree of freedom ultra precision measurement, and six-degree of freedom position and attitude measurement requirements of a lithography machine workpiece stage and the like are met.

Description

technical field [0001] The invention relates to the technical field of interferometry, and more specifically, to a five-degree-of-freedom heterodyne grating interferometry system. Background technique [0002] As a typical displacement sensor, the interferometric measurement system has the advantages of traceability of length, high measurement accuracy, large measurement range, large dynamic measurement range, easy installation and debugging, etc., and is widely used in the field of precision and ultra-precision measurement. Commonly found in precision machinery and processing equipment. At present, the interferometry system can be mainly divided into laser interferometry system and grating interferometry system. The laser interferometry system is based on the measurement principle of laser interferometry, while the grating interferometry system is based on the principle of diffraction interference. The measurement reference is the grating pitch. The sensitivity to environm...

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Problems solved by technology

[0004] For the above problems, the usual method is to use multiple single-degree-of-freedom laser measurement systems to form a distributed multi-degree-of-freedom measurement system, such as the U.S. patent US 6020964B2 (disclosed on February 1, 2000) of ASML Corporation in the Netherlands, and the U.S. patent of Nikon Corporation in Japan. US 6980279B2 (published on December 27, 2005) and the US patent US7355719B2 (published on April 8, 2008) of Agilent Corporation of the United States all adopt a similar six-degree-of-freedom measurement system, that is, a multi-axis laser interferometer is arranged in the horizontal direction , using a 45° mirror to introduce the measurement light into the Z axis, installing the mirror on the side and the Z direction, using the displacement difference to calculate the rotation angle, and realizing the six-degree-of-freedom measurement, but the distributed interferometric system takes up a lot of space and is difficult to install and adjust, which is difficult to meet measurement requirements

In the grating interferometry system, the common one is the two-degree-of-freedom measurement system, such as the German Heidenhain company's US patent US0058173A1 (disclosure date March 15, 2007), but simultaneous measurement of more degrees of freedom cannot be achieved

Others such as Lee et al. based on a two-degree-of-freedom grating interferometry system, using PSD and a specific optical path structure to propose a simple six-degree-of-freedom simultaneous measurement method [C.B.Lee, G.H.Kim, and S.K.Lee, "Design and construction of asingle unit multi -function optical encoder for a six-degree-of-freedom motionerror measurement in an ultra-precision linear stage”, Meas.Sci.Technol, 2011], but the structure of the measurement system is complex, and the measurement of multiple degrees of freedom depends on specific The optical path structure, the consistency and stability of the measurement are poor, and the measurement accuracy is largely limited by the performance of the detector. Generally, the measurement accuracy of the rotation angle can only reach the order of arc seconds, and the measurement accuracy of the displacement can only reach the order of microns. Meeting the Performance Requirements of Ultra-Precision Measurement Systems

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