Development of phase-shifting interferometry for measurement of isothermal diffusion coefficients in binary solutions
Development of phase-shifting interferometry for measurement of isothermal diffusion coefficients in binary solutions
复制标题
DOI：
10.1016/j.optlaseng.2012.03.006
复制
发表时间：
2012-09
影响因子：
4.6
通讯作者：
J. F. Torres;A. Komiya;E. Shoji;J. Okajima;S. Maruyama
中科院分区：
文献类型：
--
作者：
J. F. Torres;A. Komiya;E. Shoji;J. Okajima;S. Maruyama
在这项研究中，相移干涉仪进行实时高分辨率测量的浓度分布在二元扩散领域的发展。相移干涉仪包括马赫-曾德尔干涉仪、旋转偏振器、CCD摄像机和图像处理单元。相移技术被用来确定测试光束和参考光束之间的相位差，通过使用以1/30秒的间隔拍摄的三个图像。在640×240的空间分辨率下获得相位差。该数据被进一步实时处理，以可视化扩散池内的浓度分布。通过对实验浓度分布进行逆分析来确定扩散系数。目标函数利用数值计算，根据菲克定律，其中初始实验浓度分布作为初始条件。扩散场形成于热控制扩散池内，光程为20 mm。这种大的光路允许测量浓度差窄至1 mg/ml的扩散场。为了验证测量方法，在25°C的稀释区域中测定NaCl和蔗糖的等温扩散系数的浓度依赖性，这些值在文献中被广泛报道。结果表明，该光学系统比同类光学系统更快、更准确地测定二元体系的扩散系数。
In this study, a phase-shifting interferometer to conduct real-time high-resolution measurements of concentration profiles in binary diffusion fields was developed. The phase-shifting interferometer comprises a Mach–Zehnder interferometer, a rotating polarizer, a CCD camera, and an image-processing unit. A phase-shifting technique was used to determine the phase difference between a test beam and a reference beam by using three images taken at intervals of 1/30s. The phase difference is obtained for a spatial resolution of 640×240. This data is further processed in real-time to visualize the concentration profile inside a diffusion cell. The diffusion coefficient is determined by performing an inverse analysis of the experimental concentration profile. The objective function makes use of a numerical calculation, based on Fick's law, for which the initial experimental concentration profile is taken as initial condition. The diffusion field was formed inside a thermally controlled diffusion cell with optical paths as large as 20mm. This large optical path allows measurements of diffusion fields with concentration differences as narrow as 1mg/ml. In order to validate the measurement method, the concentration dependence of the isothermal diffusion coefficient of NaCl and Sucrose was determined in the dilute region at 25°C, such values being extensively reported in the literature. It was found that our optical system is much faster and accurate than similar optical systems to determine the diffusion coefficients in binary systems.