Deformation Measurement Of Object Based On Speckle Interferometry

Speckle interferometry is a new-type optical testing method which relates to laser, holography, digital image processing and other technologies. The measurement precision can reach micron level, and meanwhile, with the development of computer technology, speckle interferometry realizes automation measurement and can be used for testing surface deformation of metal object.Twyman-Green beam path is used for obtaining interference pattern in this paper. Every speckle pattern after deformation is received by CCD. Fringe information in speckle pattern is obtained by appropriate algorithm, so interference fringe patterns are observed.Several methods based on digital image processing are adopted to improve contrast further, meanwhile thinning processing improves measurement accuracy. Finally three-dimensional phase of measured object is obtained by two-dimensional Fourier Transforming, thus the size and direction of deformation are achieved. Experimental results show that filter processing and the method of extracting skeleton line improve measurement accuracy obviously, the precision can reach up to λ/10and relative error is less than2%.