26 June 2017 Digital holography on moving objects: multiwavelength height measurements on inclined surfaces
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Abstract
Multiwavelength digital holography on moving objects enables fast and precise inline-measurements of surface pro files. Due to the use of multiple wavelengths, optically rough surfaces with structure heights in the micrometer range can be mapped unambiguously. In this work we explore the influence of the object velocity on height measurements on inclined surfaces. We show measurements using spatial-phase-shifting holography employing two wavelengths and object velocities of up to 90 mm/s with eye-safe cw-lasers with less than 1 mW of laser light. Despite motion blur exceeding the mean speckle size, reliable height measurements can be conducted at these velocities. The height map of a metal cone with two different slope angles (1° , 10° ) is measured at an exposure time of 2 ms. Using line shaped illumination, each frame yields a height map of approximately 2 x 17 mm2. The overlap between the frames allows averaging as the image is put together, improving data quality. The mean repeatability of the height information in the investigated setup is better than 4.5 µm at a synthetic wavelength of 214 µm.
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Annelie Schiller, Annelie Schiller, Tobias Beckmann, Tobias Beckmann, Markus Fratz, Markus Fratz, Dominik Belzer, Dominik Belzer, Alexander Bertz, Alexander Bertz, Daniel Carl, Daniel Carl, Karsten Buse, Karsten Buse, } "Digital holography on moving objects: multiwavelength height measurements on inclined surfaces", Proc. SPIE 10329, Optical Measurement Systems for Industrial Inspection X, 103290D (26 June 2017); doi: 10.1117/12.2270176; https://doi.org/10.1117/12.2270176
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