The principle and experimental results of the generation of contour map of an object by moire techniques are described.
A equi-spaced plane grating is projected onto an object by a lens. The projected pattern is deformed due to the height variation of the object. The deformed pattern is imaged again on another grating by a similar lens.
If the two gratings are identical and lie in a common plane and the two lenses are also identical, the moire fringes observed on the second grating represent a contour map of the object.
