Nondestructive testing by use of TV holography and deformation phase gradient calculation.
We present a technique for nondestructive testing based on phase shifting TV holography and digital image processing. With this technique we calculate the phase modulation of the object light caused by object deformation. The resulting deformation phase image is smoothed to obtain a better signal-to-noise ratio. Smoothing is done by a new low pass filtering procedure we call phase shifting convolution. This procedure is based on smoothing of two phase images: the original phase image and a second image obtained by spatial phase shift of the original phase image. By combining the two smoothed images we obtain an image without smoothing errors close to the 2pi phase ambiguities in the deformation phase image. To detect surface areas with local inhomogeneous deformations indicating material defects, we calculate and display the deformation phase gradients. Examples with testing of composite materials are shown.
Vikhagen
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E