针对折射现象对水下视觉系统的影响并为了实现视觉系统的便携性,本文构建了基于光平面约束的水下视觉测量系统。首先,建立了基于光平面约束的水下结构光测量模型,并从理论上证明了当投影仪垂直于折射平面投射且光平面经过投射光轴时,陆上投射光线与投影光轴构成的空气中的光平面以及水下折射光线与折射平面法向量构成的水下光平面为同一平面,这样从理论上证明了陆上标定代替水下标定的可行性,避免了光平面的水下标定过程;然后,根据光平面簇共线的约束条件设计了中心旋转编码光模式,通过光平面旋转角度实现了对投影光模式的编解码;最后,按照测量模型中的光平面约束条件,提出了对应的陆上优化标定方法。实验结果证明,本文提出的水下视觉测量系统在2 m以内的测量距离上,可以获得1.72 mm的测量精度。该系统可用于弥补当前水下声学三维形貌测量中无法进行近距离、高精度和高分辨率测量的不足,有效地避免了水下标定操作,提高了水下视觉测量系统的便携性,有利于扩大视觉测量系统在水下工程探测、水下三维形貌测量、水下结构缺陷检测中的应用。

Aiming at the influence of refraction on underwater vision system and to achieve portability of the vision system, an underwater vision measurement system based on the constraint of light-plane is established in this paper. First, the underwater structured light measurement model based on the light-plane constraint is proposed. It is theoretically proved that when the projector is perpendicularly projected to the refraction plane and the light-plane passes through the projection optical axis, the light-plane in the air formed by the projection light on land and the projection optical axis is the same with the light-plane in water formed by the underwater refraction light and the normal vector of the refraction plane, which theoretically proves the feasibility of land calibration instead of underwater calibration, avoiding the underwater calibration process of the light-plane. Then, the center rotation light mode is designed based on the light-plane constraint, and the light pattern is decoded through the light-plane rotation angle. Finally, the optimized land calibration method is proposed based on the light-plane constraints. Experiments show that the proposed underwater structured light system can achieve a measurement accuracy of 1.72 mm at a measurement distance of less than 2 m. The system can compensate the lack of short distance, high accuracy, and high resolution in the current underwater acoustic three-dimensional topography measurement. Furthermore, the proposed system can effectively avoid underwater calibration operation, improve the portability of underwater vision system, and expand the application of vision measurement system in underwater engineering detection, underwater three-dimensional topography measurement, and underwater structural defect detection.