基于光学成像原理和激光三角测距法，提出将三个点激光器与水下相机结合、根据水下光学图像对水下目标物距离进行测量的思路。建立了激光束与目标物垂直、与目标物之间存在旋转角、存在俯仰角三种情况下的三点激光测距理论模型，推导了目标物距离与水下激光光斑图像之间的数学关系，在此基础上得到了三种情况下的三点激光测距公式。研制了系统样机，并通过空气中和水下的距离测量实验，测试了测距模型和定标算法的误差。实验结果显示，在8.4 m范围内，使用统一测距公式对距离进行测量时，测距误差最大值约为35 cm，平均测量误差小于15 cm。研究成果可望用于水下目标较近距离的精确测距。

Based on the principles of optical imaging and the method of triangular laser ranging, a method was proposed to measure the distance of an underwater target by three point laser sources and underwater camera. Theoretical models were built for the cases when the target was perpendicular to the laser beams, when there was a rotation angle and a pitching angle between the target and the laser beams. Mathematical relationships was established between underwater distance and geometric parameters of the laser spot pattern in the underwater image. Based on theoretical models, formulas for distance calibration were deduced. To verify the feasibility and accuracy of the proposed method, a prototype of the laser ranging system was implemented and tested in air and underwater. Experimental results show that the maximal measurement error is 35 cm and the mean value is less than 15 cm for a range within 8.4 m. The system has the potential to be used for accurate ranging at short distance underwater.