High-frame rate, large-depth-range structured light projector based on the step-designed LED chips array.

Among numerous mature optical 3D measurement techniques, phase-shift profilometry (PSP) has been widely used because of its high precision and insensitivity to ambient light, and high-speed PSP has become a research hotspot in recent years. Current mainstream high-frame rate PSP projection techniques employ binary defocusing projection schemes, which limit the available measurement depth. We propose a high-frame rate, large-depth-range sinusoidal fringe projection technique based on step-designed LED chips array. In principle, on the one hand, the LED chips array still produces a binary pattern, so high-frame rate switching can be achieved, on the other hand, whether focusing or defocusing can generate sinusoidal fringes, avoiding the limit of defocusing projection on the depth range of measurement. A PSP projector is designed and manufactured, and 3D reconstruction of static human face mask and dynamic rotating fan is carried out at 1 kHz frame rate. In another experiment, the PSP projector projected the fringes at a 100kHz frame rate and detected the fringes with a single point photodetector, and the output waveform showed that the projection technique had the potential to be much higher than the 100 kHz frame rate. These results show that the PSP projection technology has the advantages of high-frame rate and large-depth-range, and is very useful for three-dimensional measurement of moving targets.