Shearography for specular object inspection

Digital shearography is a laser speckle pattern interferometry based, non-destructive testing (NDT) method, which has a great potential in revealing the defects inside the objects e.g. composite materials. It has been applied successfully in various industry applications. However, due to its essence of laser speckle utilization, the object surface needs to be rough enough, otherwise, the object surface has to be specially treated. Considering the situations that the surface treatment under some cases is not allowed, an improved optical setup has been introduced and described in this paper. A modified shearography setup which can be applied on samples with specular surface is introduced. The theory and experiment results are described and presented.