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Optical Engineering

Enhanced multiwavelength holographic profilometry by laser mode selection
Author(s): Eduardo A. Barbosa; Eduardo A. Lima; Marcos R. R. Gesualdi; Mikiya Muramatsu
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Paper Abstract

A method for improving the accuracy of surface shape measurement by multiwavelength holography is presented. In our holographic setup, a Bi12TiO20 photorefractive crystal was the holographic recording medium, and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. On employing such lasers the resulting holographic image appears covered with interference fringes corresponding to the object relief, and the interferogram spatial frequency is proportional to the diode laser's free spectral range (FSR). Our method consists in increasing the effective free spectral range of the laser by positioning a Fabry-Perot étalon at the laser output for mode selection. As larger effective values of the laser FSR were achieved, higher-spatial-frequency interferograms were obtained and therefore more sensitive and accurate measurements were performed. The quantitative evaluation of the interferograms was made through the phase-stepping technique, and the phase map unwrapping was carried out through the cellular-automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared with respect to measurement noise and visual inspection.

Paper Details

Date Published: 1 July 2007
PDF: 7 pages
Opt. Eng. 46(7) 075601 doi: 10.1117/1.2756817
Published in: Optical Engineering Volume 46, Issue 7
Show Author Affiliations
Eduardo A. Barbosa, Faculdade de Tecnologia de São Paulo (Brazil)
Eduardo A. Lima, Faculdade de Tecnologia de São Paulo (Brazil)
Marcos R. R. Gesualdi, Univ. Federal do ABC (Brazil)
Mikiya Muramatsu, Univ. de São Paulo (Brazil)

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