A new technique based on digital shearography for determining the transient curvature and twist of a continuously deforming object from a series of speckle patterns is presented. The intensity variation of each pixel is analyzed along the time axis by using a complex Morlet wavelet transform. The absolute sign of the phase variation is determined by introduction of a temporal carrier when the speckle patterns are captured by a high-speed camera. A high-quality spatial distribution of the deflection derivative is extracted at any instant without the need for temporal or spatial phase unwrapping. The continuous Haar wavelet transform is subsequently processed as a differentiation operator to reconstruct the instantaneous curvature and twist of a continuously deforming object.
© 2005 Optical Society of America
(100.7410) Image processing : Wavelets
(110.6150) Imaging systems : Speckle imaging
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.6160) Instrumentation, measurement, and metrology : Speckle interferometry
Cho Jui Tay and Yu Fu, "Determination of curvature and twist by digital shearography and wavelet transforms," Opt. Lett. 30, 2873-2875 (2005)