提出了一种精确测量1/4波片相位延迟量的新方法。测量光路由激光器、起偏器、被测1/4波片、光弹调制器、检偏器和光电探测器构成。起偏器和检偏器的透光轴相互垂直。被测1/4波片的快轴与光弹调制器的振动轴平行,且与起偏器和检偏器的透光轴分别成±45°夹角。准直激光束依次经过起偏器、被测1/4波片、光弹调制器和检偏器的探测光强由光电探测器接收。利用探测信号的直流分量与二次谐波分量精确计算出被测1/4波片的相位延迟量。实验验证了这种测量方法的有效性,改变初始光强过程中相位延迟量测量结果的复现性为0.012°,检偏器、被测1/4波片的方位角变化1°的过程中相位延迟量测量结果的复现性为0.008°。

A new method for measuring retardation of a quarter-wave plate is proposed. The optical measuring system is composed of a laser, a polarizer, the quarter-wave plate to be measured, a photoelastic modulator, an analyzer and a detector. The polarizer and the analyzer′s transmission axes are perpendicular to each other. The fast axis of the quarter-wave plate is parallel to the dynamically induced birefringent axis of the photoelastic modulator. The angles between the fast axis of the quarter-wave plate and transmission axes of the polarizer and the analyzer are ±45°, respectively. Laser beam passes through the polarizer, the quarter-wave plate, the photoelastic modulator and an analyzer to form detection signal. The retardation of the quarter-wave plate is obtained using the direct current and secondary harmonic components of the detection signal. The reproducibilities of the measured retardation of the quarter-wave plate were 0.012° and 0.008° when the initial intensity and the azimuth angles between the analyzer and the quarter-wave plate were changed, respectively.