Design and construction of a two-degree-of-freedom linear encoder for nanometric measurement of stage position and straightness

This paper presents a two-degree-of-freedom (two-DOF) linear encoder which can measure the position along the moving axis ( X-axis) and the straightness along the axis vertical to the moving axis ( Z-axis) of a precision linear stage simultaneously. The two-DOF linear encoder is composed of a reflec...

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Bibliographic Details
Published in:Precision engineering 2010, Vol.34 (1), p.145-155
Main Authors: Kimura, Akihide, Gao, Wei, Arai, Yoshikazu, Lijiang, Zeng
Format: Article
Language:English
Subjects:
Applied sciences
Electronics
Exact sciences and technology
Linear encoder
Magnetic and optical mass memories
Measurement
Mechanical engineering. Machine design
Position
Precision engineering, watch making
Storage and reproduction of information
Straightness
Two-degree-of-freedom displacement
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Summary:This paper presents a two-degree-of-freedom (two-DOF) linear encoder which can measure the position along the moving axis ( X-axis) and the straightness along the axis vertical to the moving axis ( Z-axis) of a precision linear stage simultaneously. The two-DOF linear encoder is composed of a reflective-type scale grating and an optical sensor head. A reference grating, which is identical to the scale grating except the scale length, is employed in the optical sensor head. Positive and negative first-order diffracted beams from the two gratings are superposed with each other in the optical sensor head to generate interference signals. The optical configuration is arranged in such a way that the direction of displacement in each axis can also be detected. A prototype two-DOF linear encoder is designed and constructed. The size of the optical sensor head is about 50 mm ( X) × 50 mm ( Y) × 30 mm ( Z) and the pitch of the grating is 1.6 μm. It has been confirmed that the prototype two-DOF linear encoder has sub-nanometer resolutions in both the X- and Z-axes.
ISSN:0141-6359
1873-2372
DOI:10.1016/j.precisioneng.2009.05.008