Correlation technique for the compensation of diffraction widening of optical reference signals



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Saez Landete, José and Alonso Fernández, José and Sánchez Brea, Luis Miguel and Morlanes Calvo, Tomás and Bernabeu Martínez, Eusebio (2009) Correlation technique for the compensation of diffraction widening of optical reference signals. Journal of The Optical Society Of America A-Optics Image Science and Vision, 26 (9). pp. 1901-1906. ISSN 1084-7529

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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.

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© 2009 Optical Society of America.
This work has been supported by Center for Innovation in Transport (CENIT) project “Tecnologías avanzadas para los equipos y procesos de fabricación de 2015: e-eficiente, e-cológica, e-máquina (eEe)” of the Ministerio de Industria, Turismo y Comercio of Spain and by the Madrid Autonomous Community-University of Alcalá de Henares (CAM-UAH) project CCG08-UAH/TIC-3941.

Uncontrolled Keywords:Design, Codes, Light
Subjects:Sciences > Physics > Optics
ID Code:26222
Deposited On:17 Jul 2014 11:51
Last Modified:17 Jul 2014 11:51

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