%0 Journal Article
%A Saez Landete, José
%A Alonso Fernández, José
%A Sánchez Brea, Luis Miguel
%A Morlanes Calvo, Tomás
%A Bernabeu Martínez, Eusebio
%T Correlation technique for the compensation of diffraction widening of optical reference signals
%D 2009
%@ 1084-7529
%U https://hdl.handle.net/20.500.14352/44293
%X 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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