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Proceedings Paper

Design verifications of a linear laser encoder with high head-to-scale tolerance
Author(s): Chyan-Chyi Wu; Yi-Chun Chen; Chih-Kung Lee; Chi-Tang Jeffrey Hsieh; Wen-Jack Wu; Sheyshi Lu
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Paper Abstract

Laser encoders overcome the fundamental resolution limit of geometrical optical encoders by cleverly converting the diffraction limit to phase coded information so as to facilitate nanometer displacement measurement. As positioning information was coded within the optical wavefront of laser encoders, interferometry principles thus must be adopted within the design of the laser encoders. This effect has posed a very strong alignment tolerance among various components of the whole laser encoder, which in turn impose a serious user adaptation bottleneck. Out of all alignment tolerance, the head-to-scale alignment tolerance represents the most important hindrance for wider applications. Improving the IBM laser optical encoder design by taking into the consideration of manufacturing tolerance of various optical components, an innovative linear laser encoder with very high head-to-scale tolerance is presented in this article. Efficiency of the TE/TM incident light beams on the grating scale used are examined theoretically and verified experimentally so as to provide design optimizations of the grating scale. Effect of various grating scale, quartz master or polymer-based grating replicate, is also detailed. Signal processing used to decoded the quadrature based positioning optical signal is also studied. Experimental results that verify the resolutions of the tabletop laser encoder prototype by comparing the decoded quadrature signal and a HP laser interferometer output signal is also presented.

Paper Details

Date Published: 5 October 1999
PDF: 10 pages
Proc. SPIE 3779, Current Developments in Optical Design and Optical Engineering VIII, (5 October 1999); doi: 10.1117/12.368194
Show Author Affiliations
Chyan-Chyi Wu, National Taiwan Univ. (Taiwan)
Yi-Chun Chen, National Taiwan Univ. (Taiwan)
Chih-Kung Lee, National Taiwan Univ. (Taiwan)
Chi-Tang Jeffrey Hsieh, AHEAD Optoelectronics, Inc. (Taiwan)
Wen-Jack Wu, National Taiwan Univ. (Taiwan)
Sheyshi Lu, National Taiwan Univ. (Taiwan)

Published in SPIE Proceedings Vol. 3779:
Current Developments in Optical Design and Optical Engineering VIII
Robert E. Fischer; Warren J. Smith, Editor(s)

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