Separation method of superimposed gratings in double-projector structured-light vision 3D measurement system

In structured-light vision (SLV) 3D measurement technology, double-projector SLV is often used to solve the defects in single projector SLV, such as the shadow caused by the self-occlusion of the measured object's surface profile and the limitation of the projector's visual angle. Usually, to avoid gratings' superimposition, multiple projectors cannot work at the same time. In this paper, we design a new separation method to separate phase-shifted superimposed gratings by controlling the sequence in double-projector SLV. Without changing the original measurement system, the four-step phase-shifted method and dual-frequency method are combined to solve the unwrapped phase. Based on the proposed separation method, the wrapped phases of left and right projections are obtained only by six phase-shifted gratings, whose efficiency is improved by 25%. The separation method includes the process of averaging phase patterns, which improves the phase accuracy of the measured object, comparing with the single projector measurement. Experiments demonstrate that this method can separate phase-shifted superimposed gratings simply, quickly, effectively and accurately without additional hardware devices. This method is practical and general.