Design and fabrication of digital dual-frequency patterns for projected fringe profilometry

Abstract

One key problem of fringe projection techniques for 3D shape measurements is the limited phase unambiguity range when only one grating period is used. Dual-frequency patterns in which involves two grating periods can easily extend the unambiguity range. A method to fabricate accurate dual-frequency patterns is presented. The advantage of using digital dual-frequency patterns for projected fringe profilometry are (1) high geometrical accuracy (< 0.5μm); (2) high contrast ratio; (3) very low high order harmonic distortions; and (4) extended unambiguity range.