全自动可变光阑测量激光发散角的工程化研究

Engineering study on the auto-measurement of divergence angle of the laser beam with the variable diaphragms

激光远场发散角是评价激光光束质量的重要指标,根据远场发散角的定义和国际惯例,实际工程应用中设计出全自动可变光阑来测量激光远场发散角。在测量时利用图像处理和一阶重心距算法计算光斑中心,使可变光阑中心与待测激光束中心对准。测试系统自动由小到大变化光阑孔径,同时用探测器测量透过的激光能量。对光阑孔径和通过光阑的能量进行曲线拟合,算出总能量为1/e2时光阑的孔径,即对应于该处的激光束宽,从而可计算得出激光远场发散角。上述测量过程是利用虚拟仪器技术来全自动实现的,该激光远场发散角测试系统经过了项目验收和实际工程检验。

Far-field divergence angle of laser beams is an important parameter in the evaluation of laser quality in the laser radiometer. According to the definition of far-field divergence angle and the international practice, the automated measurement system with the variable diaphragms was developed in the practical engineering application. It was used in the far-field divergence angle testing of laser. In the measurements, the pulse laser spots were captured with the special image processing, and the center position of laser spot was calculated by the first order moment for the center of gravity. By then the center of laser could be aligned with the center of variable diaphragms. With the automated measurement system, the diaphragms would be automatically changed from smaller to bigger, and the laser energy would be measured by the probe at the same time. It would be fitted for the chart of diameter of the diaphragm with the laser beam width, and when the part of total energy passing the diaphragm reached 1/e2 percent of total beam energy, the fitting diameter of the diaphragm would be the laser beam waist width. Finally, the far-field divergence angle of the laser beam can be calculated. This automated farfield divergence angle measuring system was based on the technology of virtual instruments. It had been passed by the customers＇ tests and proved by the practical utilization.