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Optical Engineering

Double-diffraction planar encoder by conjugate optics
Author(s): Ching-Fen Kao; Calvin C. Chang; Mao-Hong Lu
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Paper Abstract

A planar encoder using conjugate optics is proposed for sensing the 2-D displacement of a 2-D grating. A Doppler frequency shift of diffracted light is generated when the grating moves. The optical conjugate path can compensate for the error arising from the relative tilt between the optical head and the scale (head-to-scale tilt). Additionally, the optical head is easily integrated, having high tolerance in component-to-component placement. The 2-D displacement system with the 2-D grating, which has period of 1.6 µm in both the X and Y directions, provides a signal period of 0.4 µm by using a double-diffraction configuration. This system and associated electronics provide interpolation with a factor of 400, corresponding to a measurement resolution of 1 nm.

Paper Details

Date Published: 1 February 2005
PDF: 7 pages
Opt. Eng. 44(2) 023603 doi: 10.1117/1.1839227
Published in: Optical Engineering Volume 44, Issue 2
Show Author Affiliations
Ching-Fen Kao, Industrial Technology Research Institute (Taiwan)
Calvin C. Chang, Industrial Technology Research Institute (Taiwan)
Mao-Hong Lu, National Chiao Tung Univ. (Taiwan)

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