Full-field micro surface profilometry using digital fringe projection with spatial encoding principle

Abstract

This article describes an effective full-field three-dimensional micro surface profilometer using digital fringe projection with digital micromirror device (DMD) technology and triangulation measurement principle. Fast and accurate three-dimensional measurement techniques with full-field measurement capability are thus highly demanded for sharpening product competitiveness. Traditional laser triangulation methods have difficulty in detecting the accurate centre position of projected points or lines when encountered with light scattering problems caused by the object's geometric discontinuities, such as surface boundaries or edges. The newly developed profilometer deploys a DMD to project flexible digital structured light patterns of white light onto the object to suit various inspection requirements, such as the object's size and surface condition. Micro structured light patterns can be generated by using optical zoom and collimating lens sets. Accurate system parameters of 3-D surface profilometry can be obtained by developing a calibration process based on least squares minimization. Micro 3-D contours with a large surface gradient can be reconstructed accurately and efficiently.