Spatial–Temporal 3-D Directional Binary Coding Method for Fringe Projection Profilometry

Fringe projection profilometry (FPP) is a leading optical technique for high-speed and efficient 3-D measurements, crucial in automation for enhancing efficiency, quality, productivity, and reliability. Traditional FPP methods face challenges with limited pattern quantity and coding efficiency. This article introduces a novel spatial-temporal 3-D directional binary coding (STDBC) method, enhancing the conventional binary coding approach by incorporating the temporal dimension. Compared to the traditional four codewords in 1-D (x) and nine codewords in 2-D (x and y) methods, this integration expands codewords in the 3-D (x, y, and t) space, achieving up to 81 ultralarge codewords. To address decoding difficulties caused by synchronization circuit delays or memory optimization, the article introduces a directional coding method to ensure the correct decoding position of coded patterns. Additionally, a region contraction method was developed to suppress the percentage shift problem caused by static defocusing and motion blur, respectively. Under the optimized projection-decoding paradigm, the proposed method can achieve the same reconstruction efficiency as conventional single-frame coded maps with guaranteed reconstruction accuracy. Experimental results demonstrate that this method significantly advances high-precision and high-efficiency 3-D imaging as well as paves the way for further research and practical applications in various automated dynamic measurement environments.