A second image or successive images are compared to t his first image by the video-processing computer at the pixel level. The computer calculated the deformation of the test part by analyzing the interference phase shift of the laser light for each pixel. The key to electronic shearography is the shearing optical element in the optical camera. This optical system combines pairs of points from the test object allowing the video camera to form an interferogram of the test part. This panel consists of three skins and four bondlines and measures 2 inches in thickness.
Red indication is an unbond at the first skin to core bondline.
A second unbond, located at the third bondline from the surface is shown in green. Images obtained with the L TI-4200 provide a direct indication of the size, shape, and location of an unbond or other structural defect.