作为波片最重要的技术参数，波片相位延迟量的精确度会直接影响整个偏振光学系统的性能，在有些情况下，使用前需要对其进行精确测量。根据偏振干涉光谱曲线分布特性提出了一种测量波片相位延迟量的方法。此方法是将待测波片置于起偏镜和检偏镜之间，利用分光光度计测量一定范围内光谱透射率曲线，通过精确提取曲线上定值透射率对应波长，利用公式可同时获得待测波片的绝对相位延迟量、有效相位延迟量、波片级次、波片厚度等多个光学参数。理论分析和实验结果表明，该方法适用于具有任意延迟量的晶体零级或多级波片，具有测量精度高、对起偏镜与检偏镜透振方向和待测波片快轴方向调节无严格要求、操作简单的优势。

The accuracy of the phase retardation of a wave plate, which is an important technical parameter, directly affects the performance of the entire polarization optical system. It may be necessary to measure the wave plate before use. Based on the curve distribution characteristics of the polarization interference spectrum, a method for measuring the phase retardation of a wave plate is presented. In this method, the wave plate to be measured is placed between a polarizer and an analyzer, and the transmission spectrum curve in a certain spectral range is measured using a spectrophotometer. Based on an accurate estimation of the wavelengths of certain points with specific transmission from the transmission spectrum curve, the thickness, absolute phase retardation, order, and effective phase retardation of the wave plate can be obtained simultaneously. Theoretical analysis and experimental results show that the proposed method has advantages such as, suitability for zero-order or multi-order crystal wave plate with any phase retardation, high measurement precision, and ease of operation. Furthermore, it has no strict requirements for the directions of the fast axis of the wave plate and the transmission axes of the polarizer and the analyzer.