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Two Degree-of-Freedom Fiber-Coupled Heterodyne Grating Interferometer with Milli-Radian Operating Range of Rotation

1,2, 1,2,*, 1,2, 1,2, 1,2 and 1,2
1
State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
2
Beijing Lab of Precision/Ultra-Precision Manufacture Equipment and Control, Tsinghua University, Beijing 100084, China
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(14), 3219; https://doi.org/10.3390/s19143219
Received: 9 May 2019 / Revised: 18 July 2019 / Accepted: 20 July 2019 / Published: 22 July 2019
(This article belongs to the Section Optical Sensors)
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Abstract

In the displacement measurement of the wafer stage in lithography machines, signal quality is affected by the relative angular position between the encoder head and the grating. In this study, a two-degree-of-freedom fiber-coupled heterodyne grating interferometer with large operating range of rotation is presented. Fibers without fiber couplers are utilized to receive the interference beams for high-contrast signals under the circumstances of large angular displacement and ZEMAX ray tracing software simulation and experimental validation have been carried out. Meanwhile, a reference beam generated inside the encoder head is adopted to suppress the thermal drift of the interferometer. Experimental results prove that the proposed grating interferometer could realize sub-nanometer displacement measurement stability in both in-plane and out-of-plane directions, which is 0.246 nm and 0.465 nm of 3σ value respectively within 30 s. View Full-Text
Keywords: grating interferometer; encoder; heterodyne; two-degree-of-freedom; fiber-coupled; signal contrast grating interferometer; encoder; heterodyne; two-degree-of-freedom; fiber-coupled; signal contrast
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Yang, F.; Zhang, M.; Zhu, Y.; Ye, W.; Wang, L.; Xia, Y. Two Degree-of-Freedom Fiber-Coupled Heterodyne Grating Interferometer with Milli-Radian Operating Range of Rotation. Sensors 2019, 19, 3219.

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