Fabrication of digital sinusoidal gratings and precisely controlled diffusive flats and their application to highly accurate projected fringe profilometry

Fabrication of digital sinusoidal gratings and precisely controlled diffusive flats and their application to calibration-based highly accurate phase-shifting projected fringe profilometry are presented. The main advantages of using digital sinusoidal gratings are (1) high geometrical accuracy (< 1 μm); (2) high contrast ratio; and (3) very low high-order harmonic distortion. In addition, a high-quality diffusive flat with precisely controlled lateral correlation length, fabricated by VLSI processes, offers a good calibration standard. It is found that, by applying these two components to the calibration-based phase-shifting projected fringe profilometry, absolute 3-D surface profile measurement accuracy on the order of microns can be achieved.