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Absolute height measurement of specular surfaces with modified active fringe reflection photogrammetry

Ren, Hongyu, Jiang, Xiangqian, Gao, Feng and Zhang, Zonghua (2014) Absolute height measurement of specular surfaces with modified active fringe reflection photogrammetry. In: Interferometry XVII: Advanced Applications. Proceedings of SPIE, 9204 (9204). SPIE, San Diego, California, USA, 920408-1-920408-8. ISBN 9781628412314

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Abstract

Deflectometric methods have existed for more than a decade for slope measurement of specular freeform surfaces through utilization of the deformation of a sample pattern after reflection from a test surface. Usually, these approaches require two-directional fringe patterns to be projected on a LCD screen or ground glass and require slope integration, which leads to some complexity for the whole measuring process.
This paper proposes a new mathematical measurement model for measuring topography information of freeform specular surfaces, which integrates a virtual reference specular surface into the method of active fringe reflection delfectometry and presents a straight-forward relation between height and phase. This method only requires one direction of horizontal or vertical sinusoidal fringe patterns to be projected on a LCD screen, resulting in a significant reduction in capture time over established method. Assuming the whole system has been pre-calibrated, during the measurement process, the fringe patterns are captured separately via the virtual reference and detected freeform surfaces by a CCD camera. The reference phase can be solved according to spatial geometrical relation between LCD screen and CCD camera. The captured phases can be unwrapped with a heterodyne technique and optimum frequency selection method. Based on this calculated unwrapped-phase and that proposed mathematical model, absolute height of the inspected surface can be computed. Simulated and experimental results show that this methodology can conveniently calculate topography information for freeform and structured specular surfaces without integration and reconstruction processes.

Item Type: Book Chapter
Subjects: Q Science > QC Physics
T Technology > TS Manufactures
Schools: School of Computing and Engineering
School of Computing and Engineering > Centre for Precision Technologies
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Depositing User: Feng Gao
Date Deposited: 23 Jun 2015 14:03
Last Modified: 03 Dec 2016 02:02
URI: http://eprints.hud.ac.uk/id/eprint/24802

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