Real-time measurement of retardation of eighth-wave plate independent of fast-axis direction

A real-time measurement method for the retardation of an eighth-wave plate is proposed. The collimated laser beam is split using a Glan Taylor polarizer with two side escape windows. The reflected sub-beam is detected using a detector, whereas the transmitted sub-beam passes through the quarter-wave plate and the eighth-wave plate of interest. Then, it is reflected by the mirror and passes reversely through the eighth-and quarter-wave plates. Finally, it is analyzed using the Glan Taylor polarizer and detected using another detector. With two detection signals, the retardation is resolved and found to be independent of the fast-axis direction, initial intensity, and circuit parameters. In the experiment, a crystal quartz sample is measured at different fast-axis angles. The standard deviation of the retardation is 0.9 o . The usefulness of the method is verified.     

ATR-THz波谱结合PLS-DA对陈化小麦快速无损鉴别研究

采用ATR附件采集了人工控制条件老化小麦样品的太赫兹波谱数据,并在PCA综合得分基础上对数据进行分集,建立陈化小麦的快速无损鉴别PLS-DA模型,并对其进行外部验证。结果显示,针对吸收系数谱,所建模型的校正集实验组、对照组以及交互验证实验组、对照组正确率分别为84.2%,94.7%,84.2%和81.6%,外部验证集实验组、对照组正确率分别为73.7%和100.0%;针对折射率谱,所建模型的校正集实验组、对照组以及交互验证实验组、对照组正确率分别为84.2%,92%,76.3%和76.3%,外部验证集实验组、对照组正确率分别为84.2%和89.5%。研究表明,ATR-THz技术在陈化小麦无损鉴别方面具有一定的应用潜力。