提出一种精确测量波片相位延迟的方法。将待测波片置于起偏器和检偏器之间,转动待测波片和检偏器至不同的位置并探测输出的光强,得到波片的相位延迟。采用光源调制技术和解调技术,抑制了连续光所无法克服的背景光干扰和电子噪声的干扰；将光路分为测量光路和参考光路,采用软件除法技术,消除了光源波动的影响,从而实现波片相位延迟的精确测量。详细分析了影响测量精度的误差因素,主要有光源波长变化、温度变化、入射角倾斜、转台转角误差和光源波动,计算了1064 nm波长时厚度为0.52 mm的λ/4多级结晶石英波片产生的相位延迟误差,其中光源波动的影响在作除法后有显著的改善,各误差因素的总测量误差为±1.58°。实际测量了该λ/4结晶石英波片的相位延迟为91.06°±1.78°,与理论分析相符。该测量和误差分析方法同样适合其他的波片。

A method for precisely measuring the phase retardation of wave plate is presented. In this method, a test wave plate is placed between a polarizer and an analyzer, with the polarizer and the analyzer being rotated to different position, the output power is tested and the phase retardation of the wave plate is reached. The modulated light source and the demodulation technique are used to erase the noises, which are helpless for continuous light, arise from background light and electronics. Since the light path is divided into measurement light path and reference light path and the software division technology is used, the influence of light fluctuation is eliminated and the phase retardation of wave plate can be measured precisely. Main error factors that degrade the measurement accuracy are analyzed in detail, which are wavelength change of the light source, temperature change of surrounding environment, oblique incidence of the light, rotational angle error of the sample carriers and fluctuation of the light power. Phase retardation errors that arise from the above mentioned factors for a piece of crystal quartz plate with thickness of 0.52 mm and phase retardation being 90° at 1064 nm are analyzed and calculated. The influence of light fluctuation is greatly improved after using division technique, and the total error is ±1.58°. The quartz wave plate with thickness of 0.52 mm is tested experimentally, and its phase retardation is 91.06°±1.78°, which consists with the theoretical analysis. Methods about measurement and error analysis can also be used for other wave plates.