DETERMINATION OF FRACTIONAL FRINGE ORDER BY PHASE-SHIFTING IN REAL-TIME SHEAROGRAPHY

Phase shifting shearography is achieved by translating the wedge at th e iris plane of the image-shearing camera parallel to the shearing dir ection. For a particular wedge angle used, the amount of phase shift i s linearly proportional to the amount of wedge translation. Furthermor e, the sensitivity of the phase shift increases with wedge angle. The experimental results for the wedge translation corresponding to a 2 pi radian phase shift deviate by less than 7% from the derived theoretic al prediction for a range of wedge angles used. This technique is part icularly developed for the determination of fractional fringe order in real-time shearography.