22 June 2015 Application of Fresnel diffraction from a 2D array of reflective disks in optical profilometry of a flat surface
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Abstract
Optical methods of three-dimensional profilometry have been of growing interest in both industrial and scientific applications. These techniques provide absolutely non-destructive measurement due to their non-contact nature and maintain their high precision in a large field of view. Most of these techniques however, are based on interferometry which happens to be considerably sensitive to environmental noises such as turbulence and vibration. We have used the phenomena of Fresnel diffraction from phase-steps instead of interferometry to maintain a higher precision and reduce sensitivity to environmental noises. This phenomena has been recently introduced as a method for precise measurement of wavelength, thickness and refractive index. A 2D array of reflective disks are placed above the test surface to provide the required phase-steps. In this paper, theoretical principles of Fresnel diffraction from phase-steps are discussed and the experimental results of testing an optical flat surface are presented. A flat mirror surface has been tested as an optical test surface and is been profiled. The results show that the method is precise and is not sensitive to environmental noises such as vibration and turbulence. Furthermore, the method seems to be a powerful means for testing of curved surfaces, too.
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Ahmad Darudi, Ahmad Darudi, Pegah Asgari, Pegah Asgari, Yousef Pourvais, Yousef Pourvais, } "Application of Fresnel diffraction from a 2D array of reflective disks in optical profilometry of a flat surface", Proc. SPIE 9525, Optical Measurement Systems for Industrial Inspection IX, 952547 (22 June 2015); doi: 10.1117/12.2184863; https://doi.org/10.1117/12.2184863
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