Automatic analysis of speckle photography fringes

Speckle interferometry is a technique adequate to metrological problems such as the measurement of object deformation. An automatic system of analysis of such measurements is given; it consists of a motorized x-y plate positioner controlled by computer, a CCD video camera, and software for image analysis. A fringe-recognition algorithm determines the spacing and orientation of the fringes and permits the calculation of the magnitude and direction of the displacement of the analyzed object point in images with variable degrees of illumination. For a 256 x 256 pixel image resolution, the procedure allows one to analyze from three fringes to a number of fringes that corresponds to 3 pixels/fringe.