Moiré fringe generation and phase shifting using a consumer product LCD projector

One of the most important uses of Moire fringes is profilometry of 3-D surfaces. Grid lines are projected onto an object, and the deformed projection is imaged onto a second grid to obtain Moire fringes [1]. Grid noise is removed by translating both grids simultaneously in their own plane. To obtain the surface height information the fringes can be traced, but much more detailed information is obtained by applying a phase shifting technique. The necessary phase-shifts of the Moire fringes are obtained by changing the relative distance between the two grids. From at least three phase-shifted Moire fringe patterns, object surface height is then calculated on all pixel points of the camera which records the Moire fringe patterns. Classically, translation of the grids is performed mechanically. Recently we have introduced a method using two liquid crystal light modulators to perform high resolution phase-shifting Moire topography without any mechanically moving parts [2]. We will now show how this new method can be implemented using a low-cost consumer product LCD projector.