在金属激光熔覆自由三维成形中，不断生长的成形面与成形喷头之间的距离应保持恒定值，以保证生长表面上处于聚焦激光焦点附近熔池的离焦量基本不变。以光学三角法为原理，提出了一种基于嵌入式机器视觉的激光自由成形熔池离焦量在线测控系统，推导出了镜头焦距设计公式，给出了系统硬件方案以及软件方案，同时为高效稳定处理熔池图像，提出了一种基于面积的熔池灰度阈值估计算法。经测试，此测量系统能实时准确地测得熔池离焦量，将该系统运用至实际薄壁圆环成形中，实时调节光头提升速度以保持离焦量恒定，使得薄壁圆环成形精度得到明显提高。

To maintain the defocusing amount during the metal laser cladding forming experiments, the distance between the forming surface and the nozzle should be fixed. Based on optical triangle method, an embedded machine vision online measuring system for controlling the laser defocusing amount is proposed. The formula for designing the lens focal length of the measuring camera is deducted, and both hardware and software solutions are meanwhile presented. To process the gained pictures from the measuring camera effectively and stably, a new algorithm estimation based on molten pool gray threshold is used for programming. The output voltage from the measuring system is also integrated into the robot controlling coding which helps adjust the nozzle position automatically once the laser defocusing amount is offset. This measuring system is later verified through several metal laser cladding forming experiments to be stable and precise. By comparing the thin-wall cylinder forming parts, the surface roughness of the part made with the measuring system is much brighter and cleaner than the ones without this system.