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 moiré technique. A grating is placed close to a deforming object, and its shadow is observed through the grating. The moiré 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.
© 2004 Optical Society of America
(100.5070) Image processing : Phase retrieval
(100.7410) Image processing : Wavelets
(120.4120) Instrumentation, measurement, and metrology : Moire' techniques
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
Cho Jui Tay, Chenggen Quan, Yu Fu, and Yuanhao Huang, "Instantaneous Velocity Displacement and Contour Measurement by Use of Shadow Moiré and Temporal Wavelet Analysis," Appl. Opt. 43, 4164-4171 (2004)