3D Shape Measurement of Complex Surface by Combining Fringe Projection and Phase Measuring Deflectometry

Abstract

There are many components having both diffused and specular surfaces together, which called as complex object. The existing fringe projection profilometry and deflectometry can only measure 3D (three-dimensional) shape of diffused and specular surfaces, respectively. This paper presents a novel method to measure 3D shape of complex objects by combining fringe projection profilometry and DPMD (direct phase measuring deflectometry) technique. The specular parts of a complex object reflect fringe pattern of two LCD (Liquid Crystal Display) screens and the other parts diffuse the projected fringe pattern from a DLP (digital light processing) projector. All the specular reflected and diffused deformed fringe patterns are simultaneously captured by multiple color channels of a color camera from a different viewpoint. The reflected and diffused fringe patterns on the measured complex object are easily extracted from the captured color images. The absolute phase information is calculated from the extracted fringe patterns. After 3D calibration to build up the relationship between phase and depth, 3D shape data of the measured complex object are obtained. An artificial complex step having diffused and specular surfaces has been manufactured to verify the proposed method. Experimental results show that this method can measure complex surfaces effectively.