Shape measurement of specular/diffuse complex surface based on structured light

Optical three-dimensional (3D) measurement technology is widely used in different fields due to its advantages of non-contact, non-destructive and rapid measurement. The existing technologies of Fringe Projection Measurement and Fringe Reflection Measurement are designed for the measurement of diffusely reflective and specularly reflective surfaces respectively. However, there are many complex surfaces which have both diffused and specular reflective surfaces together in aerospace and advanced manufacturing. In this paper, a method based on structured light projection and reflection was proposed to realize rapid measurement of complex surfaces. First, a Digital Light Projector (DLP) projected blue sinusoidal fringe onto the tested surface, and red fringes displayed by a screen were reflected by its specular part simultaneously. Second, deformed fringe patterns modulated by the measured surface were captured by a color Charge Coupled Device (CCD) camera. Then, deformed fringes of different reflection surface were extracted from different color channels of the camera and then absolute phase information could be calculated. Finally, after system calibration to build up the relationship between phase and depth, 3D shape data of the measured complex object was obtained. Experimental results show that the proposed method can not only measure complex surfaces effectively, but obtain 3D shape of isolated diffused and specular surfaces simultaneously.