Moiré topography.

A technique observing contour lines of an object by the use of moiré is developed. Shadow of an equispaced plane grating is projected onto an object by a point source and observed through the grating. The resulting moiré is a contour line system showing equal depth from the plane of grating if the light source and the observing point lie on a plane parallel to the grating. A technique to wash away the unwanted aliasing moiré optimization of contour line spacing and visibility and the results of the application are described.