Shearography control consists of using a heat source or a mechanical stress which will send a wave or a vibration which will penetrate into the object to be inspected.
This wave will interact with any discontinuity present in the object, creating a surface deformation. This surface displacement is detected by a shearographic camera through the projection of a laser which forms an image where the defects create a discontinuity.
Image interpretation should be done by a level 2 ST (Shearography Testing) inspector. The inspection technique must be validated by a level 3 ST person.