为了测试长焦距激光光学系统焦距，对基于自准直原理的焦距测试精度进行了理论分析，提出了一种采用光纤激光器、分光镜、平面镜、精密测角仪、电荷耦合器件(CCD)探测器和波前采集系统的焦距测试方法。通过自行设计的波前采集系统测试被测激光光学系统透射波前，使光纤点源置于其焦点位置。由CCD探测器扫描自准直点源像面，通过扫描定焦算法，使CCD探测器置于最佳像面位置。旋转平面镜使精密测角仪和CCD探测器同步采集，通过精密测角仪获取平面镜旋转的角度和质心法判读点源像移动的线量，获取被测激光光学系统的焦距。采用此方法对焦距为7171 mm的激光光学系统焦距进行测试，并对测试结果进行分析，扩展不确定度为13.48 mm(k=2)。结果表明，该方法可满足长焦距激光光学系统的焦距测试要求。

In order to measure the focal length of long focal length laser optical system, a method based on the principle of autocollimation, using fiber laser, beam splitter, flat mirror, precision angular instrument, charge couple device (CCD) and wavefront sensor is proposed. The fiber pinhole is placed at the focal point of laser optical system by testing the transmission wavefront of laser optical system with the Shack-Hartmann wavefront. Then, the CCD is placed at the best image surface by the scanning focus algorithm. The synchronization acquisition of the angular instrument and CCD is made. The focal length of laser optical system is calculated with the angle got by precision angular instrument and the deviation of pinhole image calculated by the centroid algorithm. The long focal length laser optical system of which the focal length is 7171 mm has been tested by this method. The uncertainty of test result is 13.48 mm (k=2). The test results show that this method is practical to the focal length testing of long focal length laser optical system.