Measurement of surface topography by RGB Shadow-Moiré with direct phase demodulation



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Quiroga Mellado, Juan Antonio and Gómez Pedrero, José Antonio and Terrón López, M. José and Crespo Vázquez, Daniel (2006) Measurement of surface topography by RGB Shadow-Moiré with direct phase demodulation. Optics and Lassers in Engineering, 44 (12). pp. 1297-1310. ISSN 0143-8166

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In this paper we present the application of a direct demodulation method for the measurement of surface topography by means of Shadow-Moiré. In our set-up, we use three LEDs (with green, red and blue peak wavelengths) to illuminate the grating. Due to the different position of these light sources, a polychromatic Shadow-Moiré fringe pattern is produced, which can be described as the superposition of three monochromatic (red, green and blue) fringe patterns. Taking the image of this polychromatic fringe pattern with a RGB CCD camera, we get a monochromatic fringe pattern stored at each RGB channel of the CCD. The direct demodulation algorithm employed uses these fringe patterns to calculate the wrapped phase map. After unwrapping the phase map using a standard multi-grid technique, we implemented an automatic procedure to detect the area of interest of the phase map by removing low modulation zones and to calculate the absolute value of the phase. In this way it is possible to determine the topography of a surface with a single RGB snapshot maintaining a simple experimental set-up, which is an important feature, especially for the study of dynamic phenomena such as deformations. We present the experimental results obtained after measuring different objects with both smooth and rough surface textures.

Item Type:Article
Additional Information:

© 2006 Elsevier Ltd. This work has been financially supported by the Spanish Ministry of Science and
Education; project DPI2002-02104.

Uncontrolled Keywords:Shadow-Moiré, RGB Illumination, Asynchronous Phase Demodulation
Subjects:Sciences > Physics > Optics
ID Code:22923
Deposited On:30 Sep 2013 08:06
Last Modified:31 Dec 2020 00:01

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