Real-Time High-Accuracy 3-D Measurement System for Complex Scenes Using Cross-Projected Gray-Coded and Phase-Shifting Patterns

The structured-light 3-D measurement technology, which combines phase shift and gray code, is widely adopted in industrial measurement and quality inspection due to its features such as high accuracy, rapid phase unwrapping, robustness, and suitability for complex shapes. However, the requirement for projecting multiple frames restricts its application in real-time systems. Furthermore, it cannot simultaneously yield high-accuracy measurement results for complex scenes comprising static and dynamic objects, without introducing any motion-related artifacts. Therefore, this article introduces a real-time, fast, and highly accurate single-camera structured-light 3-D measurement system to address these challenges. This system uses a strategy of cross-projecting phase-shifting and gray-coded patterns to enhance the 3-D measurement frame rate. It also introduces an effective 2-D phase misalignment correction method to address the issue of misalignment between gray code and phase shift at the boundaries. By comparing the phase differences among different combinations of phase-shifting patterns, the system can distinguish between static and dynamic areas with a small time span. Subsequently, during the decoding process, the standard method and a motion compensation approach are, respectively, applied to static and dynamic regions. Experimental results demonstrate that our system achieves a point cloud frame rate of 30 fps, which is five times higher than the sequential projection solution and notably enhances the measurement accuracy of dynamic areas using motion compensation, all while maintaining accurate measurements in static areas.