Improved method for isochromatic demodulation by RGB calibration



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Quiroga Mellado, Juan Antonio and García Botella, Ángel and Gómez Pedrero, José Antonio (2002) Improved method for isochromatic demodulation by RGB calibration. Applied Optics, 41 (17). pp. 3461-3468. ISSN 0003-6935

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The red-blue-green (RGB) calibration technique consists in constructing an a priori calibration table of the isochromatic retardation versus the triplet of RGB values obtained with a RGB CCD camera. In this way a lookup table (LUT) is built in which the entry is the corresponding RGB triplet and the output is the given retardation. This calibration (a radiometric quantity) depends on the geometric and chromatic parameters of the setup. Once the calibration is performed, the isochromatic retardation at a given point of the sample is computed as the one that minimizes the Euclidean distance between the measured RGB triplet and the triplets stored in the LUT. We present an enhanced RGB calibration algorithm for isochromatic fringe pattern demodulation. We have improved the standard demodulation algorithm used in RGB calibration by changing the Euclidean cost function to a regularized one in which the fidelity term corresponds to the Euclidean distance between RGB triplets; the regularizing term forces piecewise continuity for the isochromatic retardation. Additionally we have implemented a selective search in the RGB calibration LUT. We have tested the algorithm with simulated as well as real photoelastic data with good results.

Item Type:Article
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© 2002 Optical Society of America.
We appreciate the financial support for this work given by the European Union project Advanced Integrated Nondestructive Testing Concepts for Unified Life-Cycle (INDUCE), BRPR-CT98-0805.

Uncontrolled Keywords:Optics
Subjects:Sciences > Physics > Optics
ID Code:23126
Deposited On:14 Oct 2013 09:11
Last Modified:07 Feb 2014 10:57

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