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Proceedings Paper

High-resolution absolute position detection using a multiple grating
Author(s): Ulrich Schilling; Pawel Drabarek; Goetz Kuehnle; Hans J. Tiziani
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Paper Abstract

To control electro-mechanical engines, high-resolution linear and rotary encoders are needed. Interferometric methods (grating interferometers) promise a resolution of a few nanometers, but have an ambiguity range of some microns. Incremental encoders increase the absolute measurement range by counting the signal periods starting from a defined initial point. In many applications, however, it is not possible to move to this initial point, so that absolute encoders have to be used. Absolute encoders generally have a scale with two or more tracks placed next to each other. Therefore, they use a two-dimensional grating structure to measure a one-dimensional position. We present a new method, which uses a one-dimensional structure to determine the position in one dimension. It is based on a grating with a large grating period up to some millimeters, having the same diffraction efficiency in several predefined diffraction orders (multiple grating). By combining the phase signals of the different diffraction orders, it is possible to establish the position in an absolute range of the grating period with a resolution like incremental grating interferometers. The principal functionality was demonstrated by applying the multiple grating in a heterodyne grating interferometer. The heterodyne frequency was generated by a frequency modulated laser in an unbalanced interferometer. In experimental measurements an absolute range of 8 mm was obtained while achieving a resolution of 10 nm.

Paper Details

Date Published: 26 August 1996
PDF: 10 pages
Proc. SPIE 2783, Micro-Optical Technologies for Measurement, Sensors, and Microsystems, (26 August 1996); doi: 10.1117/12.248492
Show Author Affiliations
Ulrich Schilling, Univ. Stuttgart (FRG) and Robert Bosch GmbH (Germany)
Pawel Drabarek, Robert Bosch GmbH (Germany)
Goetz Kuehnle, Robert Bosch GmbH (Germany)
Hans J. Tiziani, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 2783:
Micro-Optical Technologies for Measurement, Sensors, and Microsystems
Olivier M. Parriaux, Editor(s)

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