激光回馈波片位相延迟测量的误差源及消除方法

激光回馈法是一种新型的波片位相延迟测量方法。将波片放置在激光器与回馈镜之间，可使激光回馈波形产生偏振90°旋转（即跳变）现象，而两偏振态所占的周期比（占空比）与波片的位相延迟相关。通过测量占空比即可由计算机自动给出波片位相延迟。采用双向扫描回馈镜，2次获得并测出占空比，这样可以很好地消除两偏振态损耗的波动造成的测量误差，提高了该方法长期测量的稳定性。测量的重复性达到0.5°。该方法结构简单，在线测量精度高，满足工业化生产的需要。

Error source and its elimination in phase retardation measurement of wave plate based on laser feedback

Laser feedback is a new method to measure the phase retardation of wave plate. The wave plate is located between the laser and the feedback mirror,which can make the laser feedback waveform produce 90°rotation of polarization,i. e. polarization flipping. The duty cycle of the two polarizations is related to the phase retardation. The computer will calculate the phase retardation automatically from the cycle duty. Through scanning the feedback mirror forwards and backwards and getting the duty cycle separately,we can eliminate the error caused by the fluctuation of the two polarization states'loss,and improve the long term stability. A repeatability of 0.5 degree is ensured. This device has advantages such as simple structure,high precision of on-line measurement,and can meet the need of industrial production.