Correlation technique for the compensation of diffraction widening of optical reference signals
JOSA A, Vol. 26, Issue 9, pp. 1901-1906 (2009)
http://dx.doi.org/10.1364/JOSAA.26.001901
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Abstract
Two-grating measurement systems are routinely employed for high-resolution measurements of angular and linear displacement. Usually, these systems incorporate zero reference codes (ZRCs) to obtain a zero reference signal (ZRS), which is used as a stage-homing signal. This signal provides absolute information of the position to the otherwise relative information provided by the two-grating incremental subsystems. A zero reference signal is commonly obtained illuminating the superposition of two identical pseudorandom codes and registering the transmitted light by means of a photodiode. To increase the resolution of the system, a reduction of the grating period and the ZRC widths is required. Due to this reduction, the diffractive effects produce a widening of the ZRS and, in turn, a loss of the measuring accuracy. In this work, we propose a method to narrow the distorted signal obtained with a Lau-based encoder, reinstating the accuracy of the ZRS. The method consists of the inclusion of a correlation mask on the detector. A theoretical model to design the mask has been developed, and experimental results have been obtained that validate the proposed technique.
© 2009 Optical Society of America
OCIS Codes
(040.1880) Detectors : Detection
(040.5160) Detectors : Photodetectors
(050.1940) Diffraction and gratings : Diffraction
(050.1950) Diffraction and gratings : Diffraction gratings
(120.3940) Instrumentation, measurement, and metrology : Metrology
(230.0040) Optical devices : Detectors
ToC Category:
Detectors
History
Original Manuscript: April 9, 2009
Revised Manuscript: June 26, 2009
Manuscript Accepted: June 30, 2009
Published: August 4, 2009
Citation
José Sáez-Landete, José Alonso, Luis Miguel Sanchez-Brea, Tomás Morlanes, and Eusebio Bernabeu, "Correlation technique for the compensation of diffraction widening of optical reference signals," J. Opt. Soc. Am. A 26, 1901-1906 (2009)
http://www.opticsinfobase.org/josaa/abstract.cfm?URI=josaa-26-9-1901
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