Instantaneous velocity displacement and contour measurement by use of shadow moiré and temporal wavelet analysis
Tay, Cho Jui
Date of Issue2004
A temporal wavelet analysis method is proposed for velocity, displacement, and three-dimensional surface-profile measurement of a continuously deforming object by use of the shadow moire´ technique. A grating is placed close to a deforming object, and its shadow is observed through the grating. The moire´ fringe patterns, generated by the interference of the grating lines and their shadows, are captured by a high-speed CCD camera with a telecentric gauging lens. Instantaneous frequency of gray-value variation is evaluated point by point with the continuous wavelet transform. From the instantaneous frequency of each point on the object, the velocity, displacement, and high-quality surface profile at different instants can be retrieved. In this application, two specimens are tested to demonstrate the validity of the proposed method: One is a small coin with a rigid body motion, and the other is a simply supported beam subjected to a central point load. The results are compared with those obtained from temporal Fourier-transform and mechanical stylus methods.
DRNTU::Science::Physics::Optics and light
This paper was published in [Applied Optics] and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: [http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-43-21-4164]. Systematic or multiple reproduction or distribution to multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.