International conference on advanced phase measurement methods in optics an imaging vol:1236 pages:419-422
AIP Conference Proceedings
International Conference on Advanced Phase Measurement Methods in Optics and Imaging Ascona, SWITZERLAND, MAY 16-21, 2010
In moire profilometry, a grid of lines is projected onto an object. When the grid is observed under an angle with the projection direction, a deformed line pattern is seen. The phase of this deformed grid contains the information about the object height. In dual-grid moire projection profilometry, the deformed line pattern is projected onto a second straight grid, leading to the generation of moire fringes. To obtain the fringe phase, at least three phase shifted moire topograms are needed. The phase shifts are obtained by translating one grid in its own plane and along the direction perpendicular to the grid lines. We have developed an LCD-based system, in which phase shifting is obtained without any mechanical moving parts. By using LCD's, we can generate grids with a sinusoidal intensity pattern, which gives the technique superior linearity as compared to the use of classical Ronchi-rulings. The non-linear response of the LCD's is compensated using a gamma-correction function, so that grid lines with nearly perfectly sinusoidal intensity patterns are obtained. In this paper we will present results obtained with this profilometer, and demonstrate how the use of sinusoidal line patterns improves the linearity of the phase extraction.