Optical methods of shadow and projection moire are particularly suitable for mapping the absolute shape of a given surface or the difference between that surface and a master one or its accidental shape change. Essentially, product moire fringes are obtained on an image plane where a "filter" grating analyzes the image of the test surface which has been "coded" by projecting a master grating on it. The article resumes the theory in a unifying approach and presents a comprehensive list of applications.
"Shadow And Projection Moire Techniques For Absolute Or Relative Mapping Of Surface Shapes," Optical Engineering 21(4), 214640 (1 August 1982). https://doi.org/10.1117/12.7972959