波片、晶体等自然双折射元件广泛应用于各种光学系统中。普通光学元件在加工、镀膜等过程中会引入残余的内应力, 形成双折射。双折射会对整个光学系统的性能产生影响, 需要对其进行精确测量。基于激光回馈效应, 利用偏振跳变中光强调制曲线与双折射的线性关系, 构建了光学元件双折射测量系统。通过引入稳频技术, 使激光器长期稳定单纵模运转, 增强了激光器的抗干扰能力, 提高了系统的稳定性。实验结果表明, 构建的激光回馈双折射测量系统测量精度优于0.24°, 重复测量最大偏差0.13°, 标准差0.06°, 稳定性好, 可靠性高, 可实现在线测量。该系统有潜力应用于微小应力的在线测量, 如飞机座舱盖、汽车玻璃等。

Natural birefringent elements such as wave plates and crystals are widely used in various optical systems. During the processing and coating process, residual stress will be introduced into the common optical components, causing birefringence. The birefringence has influences on performances of whole optical systems, which needs to be measured precisely. The birefringence measurement system was constructed based on the laser feedback effect, utilizing the linear relationship between light intensity modulation curve and birefringence in polarization flipping phenomenon. The long-term stable single longitudinal mode functioning of the laser could be fulfilled by utilizing frequency stabilization technique, which improved the anti-disturbance capability of the laser and the stability of the system. The experimental results show that the measurement accuracy of the system is within 0.24 °, and standard derivation of multi-measurement is within 0.18 °. The system can work on-line with good reliability and high stability. The system has potentials to be applied to on-line measurement of micro-stress, such as stresses in aircraft canopy, automotive glass, etc.