Measurement of dynamic deformation using speckle shearography with carrier frequency generated by double-aperture

To measure the dynamic deformation and slope of an object surface,this paper proposed a shearing speckle interferometry with a spatial carrier frequency generated by double-apertures.In this method,a double-aperture mask was used to generate a spatial carrier,a rotating wedge pair was utilized to adjust the shear continuously and the sinusoidal-fitting algorithm was taken to calculate the phase distribution.This paper firstly derivated the relationship between the carrier phase and the separation of double apertures and also imaging distance.Then,the experimental condition to generate adjustable lateral shear was discussed based on the ratable wedge pair.Finally,the parameter of this measuring method was analyzed.To produce a π/2 carrier frequency,it suggested that the separation of double aperture was selected as 3.8 mm when the focus length of the imaging lens and object distance were 300 mm and 80 mm,respectively.A stress release plate after centre loading was measured,and the experimental results demonstrate that this measuring system can obtain the information of deformation in real time under the capturing rate of 15 frame/s and the measurable range of displacement peak value is from 0.11 to 1.15 μm.This approach yields simple and compact optical implementation and allows a real time detection for dynamic deformation.