用反射率和低相干技术测容器内液体的折射率

Measuring the refractive indices of liquids in a container with reflectivity and low coherence technique

为测量透明容器内液体的折射率,建立了基于容器内表面反射率测量的低相干技术实验系统。系统采用宽带低相干半导体激光光源和改进的迈克尔逊干涉仪,将装有待测液体的容器放入测量臂光路中,调节参考臂的光程,使由容器前壁内表面反射光的光程与来自参考臂反射光的光程相等,出现干涉现象。捕捉并记录下此干涉信号,并从中求出容器前壁内表面反射光的强度,再结合菲涅尔公式及反射率的定义,即可求出待测液体的折射率,其测量精度与阿贝折射仪相当。方法能够方便、快捷、准确地测出容器内液体的折射率,可用于食品、生物医学检验等领域内液体浓度或折射率的实时非接触监测。

In order to measure the refractive index of liquid in a transparent container, a low coherence interference measuring experimental system based on the measurement of the reflectivity of the container's internal surface is established. Broadband low coherence laser diode light source and improved Michelson interferometer are adopted in the.sys-tem. The container with a liquid to be measured is put into the optical path in its measuring arm,and then optical path of the reference arm is adjusted. When the optical path of a reflected light from the inner surface of the container's front wall is equal to the optical path of a reflected light from reference arm, there will be interference phenomenon. These interference signals are captured and recorded, and the intensity of reflected light from the inner surface of the container's front wall could be obtained from these recorded interference signals. The refractive index of the liquid can be obtained by combining the Fresnel Formula and the definition of reflectivity, and its measurement accuracy is equivalent to the Abbe refractometer. This method is convenient, quick and accurate in measuring the refractive index of liquids in the container and can be used for real-time non-contact monitoring liquid concentrations or refractive index in testing-food, biomedicine and other fields.