Projection Moire Profilometry using Liquid Crystal Digital Gratings

摘要

A projection moire profilometry using a pair of liquid crystal digital gratings (LCDG) is applied to determine a step height using two liquid crystal digital gratings (LCDGs). Moire contours are filtered over to remove the images of the original grating from the moire counter when a pairs of grating images are traveled to the same direction in-phase electrically. The new idea of this report is proposed to overcome the 2pi ambiguity of moire contour by changing the fringe interval of moire contours which are adjusted the period of LCDGs. The measured accuracy has been achieved to +-0.7 mm in the range of 96 mm of steep height by projecting two different of grating periods as 6.7 and 13.3 time of original grating.