Study of the fractal correlation method in displacement measurement

The classical digital speckle pattern, or digital image, correlation method of deformation measurement is based on gray level correlation between unformed and deformed digital images. Since the pattern of artificial random speckles and the natural texture have fractal characteristics, and their fractal dimensions represent both gray and morph information, a fractal correlation method of displacement measurement is developed in this paper. The in-plane displacement field of a body can be acquired. In order to verify the validity of the new method, an experiment has been designed and the results have been compared with those tested by gray correlation method. The calculation speed is over 20 times fast than the digital image correlation method. The results how that its precision is less than 0.05 pixels.