基于傅里叶变换频谱分析的液体折射率实时测量系统

Real-time measuring system for liquid refractive index based on Fourier transform spectrum analysis

提出了一种基于傅里叶变换频谱分析技术的数字化、高精度、便携式液体折射率实时干涉测量系统。该系统以劈尖形液体容器构成的等厚干涉测量光路为基础,搭建了以CCD(charge coupled device)相机记录的共路干涉测量系统。以树莓派硬件系统为平台,Python语言为编程基础,通过傅里叶变换频谱分析和三次样条插值实现记录窗口内干涉条纹数的精确提取。设计了图形操作界面,实现了测量过程的动态可视,测量过程只需提前标定未注入液体时的初始干涉条纹数,无需额外预设参数即可实现流动液体折射率的实时测量。实验中分别测定了3种液体的折射率,并验证了测量系统的时间稳定性。结果表明,当初始干涉条纹数大于180条时,测量系统有较好的时间稳定性,且测量的相对误差均在0.754%以内。

A digital,high-precision and portable real-time interferometric measurement system for liquid refractive index based on Fourier transform spectrum analysis technology was proposed.Based on the equalthickness interferometry optical path composed of a split-tip liquid container,the common-path interferometric measurement system was built recorded by a charge coupled device(CCD)camera.Taking the Raspberry Pi hardware system as platform and the Python language as programming basis,the accurate extraction of the number of interference fringes from the CCD plane was realized through Fourier transform spectrum analysis and cubic spline interpolation.Moreover,a graphical user interface(GUI)was designed to realize the dynamic visualization for the measurement process.The measurement process only needed to determine the initial fringe number before injecting any liquids,then the real-time measurement of the refractive index of flowing liquid could be realized without additional preset parameters.In the experiment,the refractive indices of three liquids were determined and the time stability of the measurement system was verified.The results show that the measurement system can achieve better time stability as the initial fringe number is greater than 180,and the measured relative errors of the refractive indices are all within 0.754%.