Fringe projection profilometry via LED array with pre-calibration

Fringe projection profilometry (FPP) is a method that determines height by analyzing distortional fringes, which is widely used in high-accuracy 3D imaging. Now, one major reason limiting imaging speed in FPP is the projection device; the capture speed of high-speed cameras far exceeds the projection frequency. Among various devices, an LED array can exceed the speed of a high-speed camera. However, non-sinusoidal fringe patterns in the LED array systems can arise from several factors that will reduce the accuracy, such as the spacing between adjacent LEDs, the inconsistency in brightness across different LEDs, and the residual high-order harmonics in binary defocusing projection. It is challenging to resolve by other methods. In this paper, we propose a method that creates a look-up table using system calibration data of phase-height models. Then we utilize the look-up table to compensate for the phase error during the reconstructing process. The foundation of the proposed method relies on the time-invariance of systematic error; any factor that impacts the sinusoidal characteristic would present as an anomaly in the unwrapped phase. Experiments have demonstrated that the root mean square errors (RMSEs) of the results yielded by the proposed method were reduced by over 90% compared to those yielded by the traditional method, reaching 20 μm accuracy. This paper offers an alternative approach for high-speed and high-accuracy 3D imaging with an LED array and presents a workable solution for addressing complex errors from non-sinusoidal fringes.