Non destructive testing by digital shearography using a Savart plate

Shearography is a growing optical technique in the field of non-destructive testing (NDT). Hololab developed an out of plane, in line and almost common path interferometer based on polarization states separation using a coated prism for digital phase-shifting shearography. This setup is efficient but does not allow varying the shearing direction, that is an important parameter for defects detection and quantification. To overcome this disadvantage, the coated prism is substituted by a Savart plate device that allows scanning several shearing directions by rotating the device around the light propagation axis. Many advantages of the prism substitution are discussed. The behaviour of the Savart plate as a shearing device is experimentally analyzed to optimize its integration within the interferometer. Recorded phasemaps in NDT for different shearing directions are presented.