A pattern produced when two sets of line grids are slightly inclined to one another. This results in the appearance of dark bands. In optics the moiré fringe is the series of interference fringes formed when two patterns of line grids on screens are superposed on each other and slightly inclined to one another. This type of interference pattern can occur in television. Moiré fringes can be used to measure displacements of one grid against another either to measure the deformation of a surface or to check the accuracy of diffraction gratings. The use of moiré fringes to measure displacements of one grid against another is called moiré interferometry. The name is French from a type of textile, usually silk, with a rippled (‘watered’) appearance.