Oblique fringe measurement by pattern correlation

This paper introduces a method for the determination of the slope and period of oblique and equi-spaced fringes by pattern correlation. In the method, two pairs of image patches in two different regions of a fringe pattern are selected for pattern correlation calculations, and the phase shift between the two selected regions of the fringe pattern is obtained from the phase curves computed with the correlation function. The computer simulation and experiment have shown that this method is useful in interferometry and laser interference lithography for determining the slope and period of the oblique and equi-spaced fringe patterns with the advantage of high resistance to noise. It has potential applications for the measurement of the fringe pattern period, fringe angle, phase difference, displacement, and other relevant physical quantities. In practice, it can also be used for the orientation of interference patterns and alignment of laser interference lithography systems.