Non-destructive evaluation (NDE) using multi-aperture DSPI system and fast Fourier transform method

Basanta Bhaduri; N. Krishna Mohan; M. P. Kothiyal

doi:10.1117/12.732772

14 September 2007 Non-destructive evaluation (NDE) using multi-aperture DSPI system and fast Fourier transform method

Basanta Bhaduri, N. Krishna Mohan, M. P. Kothiyal

Proceedings Volume 6671, Optical Manufacturing and Testing VII; 667115 (2007) https://doi.org/10.1117/12.732772
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

Digital speckle pattern interferometry (DSPI) and digital shearography (DS) are two independent whole-field non-contacting optical methods for nondestructive flaw detection and precision measurements. A multi-aperture arrangement in front the imaging lens provides the grid structure within the speckles to yield desired diffraction halos at the Fourier transform plane. A three aperture arrangement in front of the imaging system is proposed here to combine coherently three waves at the CCD plane and also to introduce spatial carrier fringes within the speckle. One of the apertures is used for imaging the object onto the CCD plane, the second aperture for introducing smooth reference wave, while the third aperture carries a small angle wedge plate to provide the shear. This method allows simultaneous phase evaluation of the out-of-plane displacement and its first order derivative (slope) by filtering the appropriate diffraction halos of the Fourier spectrum. In this paper, we describe a (1, N) phase shifting technique with fast Fourier transform (FFT) for non destructive evaluation (NDE) of quasi-dynamic behavior of objects subject to slowly varying loads. The prominent advantage of the technique is that, it requires only a single frame prior to the object deformation and N number of frames during the object deformation for NDE. Experimental results are presented on a honeycomb structure subjected to thermal load.

Citation Download Citation

Basanta Bhaduri, N. Krishna Mohan, and M. P. Kothiyal "Non-destructive evaluation (NDE) using multi-aperture DSPI system and fast Fourier transform method", Proc. SPIE 6671, Optical Manufacturing and Testing VII, 667115 (14 September 2007); https://doi.org/10.1117/12.732772

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KEYWORDS

Fourier transforms

Nondestructive evaluation

Charge-coupled devices

Speckle

Mirrors

Phase shifting

Speckle pattern

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