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Sensors 2014, 14(3), 5056-5073; doi:10.3390/s140305056
Article

Subpixelic Measurement of Large 1D Displacements: Principle, Processing Algorithms, Performances and Software

1
,
1,* , 2
,
3
 and
1
1 Automation and Micro-Mechatronics Systems Department, FEMTO-ST Institute, UMR CNRS 6174, ENSMM, Université de Franche-Comté, 25000 Besançon, France 2 Applied Mechanics Department, FEMTO-ST Institute, UMR CNRS 6174, ENSMM, Université de Franche-Comté, 25000 Besançon, France 3 Instituto Tecnológico Metropolitano, Grupo de Materiales Avanzados y Energía, 05001 Medellin,Colombia
* Author to whom correspondence should be addressed.
Received: 18 December 2013 / Revised: 3 March 2014 / Accepted: 3 March 2014 / Published: 12 March 2014
(This article belongs to the Section Physical Sensors)
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Abstract

This paper presents a visual measurement method able to sense 1D rigid body displacements with very high resolutions, large ranges and high processing rates. Sub-pixelic resolution is obtained thanks to a structured pattern placed on the target. The pattern is made of twin periodic grids with slightly different periods. The periodic frames are suited for Fourier-like phase calculations—leading to high resolution—while the period difference allows the removal of phase ambiguity and thus a high range-to-resolution ratio. The paper presents the measurement principle as well as the processing algorithms (source files are provided as supplementary materials). The theoretical and experimental performances are also discussed. The processing time is around 3 µs for a line of 780 pixels, which means that the measurement rate is mostly limited by the image acquisition frame rate. A 3-σ repeatability of 5 nm is experimentally demonstrated which has to be compared with the 168 µm measurement range.
Keywords: displacement sensing; subpixelic measurement; nanometric precision; extended range-to-resolution ratio; real-time image processing; twin-grid pattern; direct phase computation displacement sensing; subpixelic measurement; nanometric precision; extended range-to-resolution ratio; real-time image processing; twin-grid pattern; direct phase computation
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Guelpa, V.; Laurent, G.J.; Sandoz, P.; Zea, J.G.; Clévy, C. Subpixelic Measurement of Large 1D Displacements: Principle, Processing Algorithms, Performances and Software. Sensors 2014, 14, 5056-5073.

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