基于干涉原理和图像处理方法的浓度变化分布测量

利用数字全息干涉技术测量了电极过程中电极/溶液界面处溶液的浓度变化分布。以铁电极在0.5mol/dm3硫酸溶液中恒电位电流振荡的活化过程为例,测量了反应初始时刻1.6s内铁电极界面处的溶液浓度变化情况。由于在全息干涉测量中引入载波条纹,所以能够方便地应用傅里叶分析方法分析计算干涉条纹的动态变化。通过对全息干涉图像序列的分析计算得到了电极反应过程中溶液浓度变化所引起的物光相位变化,并把相位差分布用来描述浓度变化分布。计算结果显示,在反应进行到1.6s时,溶液浓度变化引起的物光峰值相位差为41.2rad,相应的溶液折射率改变量为0.0021。重建图像比较直观地再现了反应过程中溶液的浓度变化、扩散层厚度等信息,从而为动态半定量分析和检测浓度变化提供了一种新的方法。

Measurement of Concentration Change Distribution Based on Theory of Interference and Image Processing Methods

Digital holographic interferometry was used to measure concentration change distribution of the solution at the interface of electrode/solution during electrochemical reactions. In experiment, the first 1.6 s of the activation processes of potentiostatic current oscillation on iron in 0.5 mol/dm3 H2SO4 solution was studied. With the introduction of carrier fringes in digital holographic interferometry, Fourier analysis method was used to analyze interference patterns and calculate their dynamic changes conveniently. The phase difference of object wave front, which was caused by the change of the solution′s concentration during the electrochemical reaction, was calculated from interference patterns to reflect the concentration change distribution. The obtained results have shown that the maximum phase difference caused by the concentration change of the solution was 41.2 rad and the corresponding change of solution′s refractive index was 0.0021 while the electrochemical reaction was at 1.6 s. The reconstructed images, which were distribution of the phase difference of object wave front, reflected the changes such as concentration distribution, diffusion layer, etc.. It provided a new method to detect and analyze dynamic concentration changes.