为了得到云母波片的相位延迟量和双折射率随波长的变化关系，利用椭偏光谱仪连续测量了云母波片在400~770 nm光谱范围内的延迟量.在对云母波片进行校准后，测量的数据被光电探测器收集并输送到计算机，根据输出的数据可以得到云母波片的相位延迟量随波长的变化.利用测得的延迟量计算出了云母波片在一定光谱范围内的双折射率，得到了云母波片的双折射率色散曲线，并通过拟合得到了双折射率色散公式.该方法能测量任意波片的相位延迟量，并且具有测量方便、周期短、精度高等特点.

In order to gain the phase retardation and birefringence of mica wave plate according to the increase of the wavelength, the phase retardation of the mica wave plate is measured continuously in the spectral region of 400~770 nm using a spectroscopic ellipsometer. After the calibration of the mica plate, the experimental data are collected by the detector and sent to the computer. From the outputted data, the retardation can be obtained according to the increase of the wavelength. With the measured phase retardation, the birefringence of the mica wave plate can be calculated. The birefringence dispersion curve and dispersion formula are also gained. The proposed method can measure a mica wave plate with arbitrary phase retardation and has the merits of convenient, quick and high accuracy.