Determination of fractional fringe order by phase shifting in real-time shearography

Abstract

Phase shifting shearography is achieved by translating the wedge at the iris plane of the image-shearing camera parallel to the shearing direction. For a particular wedge angle used, the amount of phase shift is linearly proportional to the amount of wedge translation. Furthermore, the sensitivity of the phase shift increases with wedge angle. The experimental results for the wedge translation corresponding to a 2π radian phase shift deviate by less than 7% from the derived theoretical prediction for a range of wedge angles used. This technique is particularly developed for the determination of fractional fringe order in real-time shearography.