Retroreflective projection gratings

A retroreflective projection grating technique has been investigated to inspect quasi flat and specular surfaces. The method introduces the flexibility to adjust the properties of the grating to a specific application or to move it as a whole, in order to use phase shifting technology. Three types of optical configuration have been demonstrated. The method has been tested with a quantified artifact. The experiment shows that it can successfully recover the contour and amplitude of the surface waviness on the artifact. The method can be developed for industrial application in nondestructive testing and evaluation (NDTE).