  Fringe projection profilometry has been increasingly sought and applied in
dynamic three-dimensional (3D) shape measurement. In this work, a robust and
high-efficiency 3D measurement based on Gray-code light is proposed. Unlike the
traditional method, a novel tripartite phase unwrapping method is proposed to
avoid the jump errors on the boundary of code words, which are mainly caused by
the defocusing of the projector and the motion of the tested object.
Subsequently, the time-overlapping coding strategy is presented to greatly
increase the coding efficiency, decreasing the projected number in each group,
e.g. from 7 (3 + 4) to 4 (3 + 1) for one restored 3D frame. Combination of two
proposed techniques allows to reconstruct a pixel-wise and unambiguous 3D
geometry of dynamic scenes with strong noise using every 4 projected patterns.
The presented techniques preserve the high anti-noise ability of
Gray-coded-based method while overcoming the drawbacks of jump errors and low
coding efficiency. Experiments have demonstrated that the proposed method can
achieve the robust and high-efficiency 3D shape measurement of high-speed
dynamic scenes even polluted by strong noise.
