Interferometric studies of lateral and axial displacements of an object using digital processing of speckle photography

Abstract

Measurement of lateral and axial displacements of an object using digital processing of speckle photography provides an economic and convenient method for the mechanical manufacturing industry. Laser speckle photography is used with CCD camera to record the resultant speckle pattern through computer control. Image processing software combines the initial and final speckle images and applies the Fast Fourier Transform function (FFT) to construct interference pattern digitally. This paper explains theoretical basis and FFT algorithm. Direction and magnitude of the local displacement is determined from the orientation and spacing of the fringes. Lateral and axial displacements are measured and its uncertainty of measurement is estimated.