High-reflectivity surface measurement in structured-light technique by using a transparent screen

Fringe projection profilometry (FPP) has been widely applied to measure objects, but for measurement of the high-reflectivity surfaces is still a tricky problem. In this paper, a new high-dynamic-range (HDR) technique by using a transparent screen as an optical mask for the camera is proposed. Specially, a transparent screen is placed in front of the camera, and each camera pixel’s intensity can be precisely controlled by adjusting its corresponding screen pixel’s intensity. Experiments has verified the effectiveness of our method: the dynamic range of the 4-step phase-shift method is increased from 48.13 dB to 71.83 dB, and a fewer number of projection patterns compared with the other techniques. The significance of this study is that our method can be easily combined with the other HDR technologies to obtain a greater dynamic range for the structured light technique.