Instantaneous velocity displacement and contour measurement by use of shadow moiré and temporal wavelet analysis

• Main Authors: Tay, Cho Jui, Quan, Chenggen, Fu, Yu, Huang, Yuanhao
• Other Authors: Temasek Laboratories
• Format: Article
• Language: English
• Published: 2010
• Subjects: DRNTU::Science::Physics::Optics and light
• Online Access: https://hdl.handle.net/10356/92039; http://hdl.handle.net/10220/6472
• Institution: Nanyang Technological University

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.