全反射比较法测量液体折射率色散的研究

基于全反射原理，提出一种用比较法测量液体折射率色散的方法.分析了棱镜全反射比较法测量液体折射率色散的基本原理，推导得到折射率色散的计算公式.结果表明:待测液体折射率色散与标准液体折射率色散、全反射极限出射角有关，与棱镜折射率色散无关；搭建相应的实验光路及系统，通过与阿贝折射仪及双棱镜法测量折射率色散对比证明了该方法的准确性.实验测量了葡萄糖水、印度墨水、聚苯乙烯溶液、品红溶液、唾液、汗液及不同浓度蜜糖溶液样品的折射率色散曲线，同一样品的折射率随着波长的增加而降低，并通过柯西色散公式得到相关样品色散曲线的拟合方程.实验表明:测量液体折射率的精度约0.000 2；分离餐后汗液、唾液的折射率明显高于餐前，这一实验结论给糖尿病的无创检测血糖提供一种可能的思路.文中提出的方法不需要棱镜折射率及其色散数据，具有实验系统简单、样品量少、测量过程方便、测量精度高等特点，不仅适合于透明及弱吸收散射的液体，而且可被用于固体折射率色散的测量，具有实际推广应用意义.

A Study on the Measurement of Refractive Index Dispersion of Liquid with the Total Reflection Comparison Method

Based on the principle of total reflection, a method for measuring the refractive index dispersion of liquid with the comparison method is proposed. The basic principle of measuring the refractive index dispersion of liquid with the prism total reflection comparison method is analyzed, and the calculation formula of refractive index dispersion is derived. The analysis indicates that the refractive index dispersion of the liquid to be tested is related to the refractive index dispersion of the standard liquid and the total reflection limit exit angle, which is independent of the refractive index dispersion of the prism. The corresponding experimental light path and system were set up, and the accuracy of the method is proved by comparing the refractive index dispersion with the Abbe refractometer and double prism method. In the experiment, the refractive index dispersion curves of glucose water, Indian ink, polystyrene solution, magenta solution, saliva, sweat and different concentrations of honey solution samples were measured. The refractive index of the same sample decreased with increasing wavelength, and the fitting equation of the dispersion curve of the relevant sample was obtained with the Cauchy dispersion formula. Experiments show that the accuracy of measuring the refractive index of liquid is about 0.000 2. The refractive index of post-meal sweat and saliva was significantly higher than that before meal. The experimental conclusion provides a possible idea for non-invasive detection of blood glucose in diabetes. The proposed method does not need the refractive index and dispersion of the prism, and has the characteristics of simple experimental system, small sample amount, convenient measurement process and high measurement precision and is suitable not only for transparent and weakly absorbing scattering liquid, but also for measuring solid refractive index dispersion.