颗粒溶液颗粒尺寸及浓度的差分偏振弹性散射光谱在线分析方法

偏振弹性散射光谱技术的基本原理为在偏振光入射条件下，根据出射光的偏振特性不同可以筛选出浅表层组织的单次散射光信息和深层组织的漫散射光信息。该研究的创新点在于将这种方法应用于颗粒溶液检测，目的是在颗粒溶液原始状态下实现对颗粒尺寸及浓度的同时检测。设计了一个共轴笼式光学系统，测量了聚苯乙烯微球颗粒溶液某一角度的背向散射信号，通过控制入射端和收集端偏振片的偏振方向获得了颗粒溶液的偏振平行光谱与偏振垂直光谱，两者之差即偏振差分光谱对应颗粒的单次散射信息，将该单次散射信息与Mie散射数据库进行比对获得颗粒的尺寸，然后在颗粒尺寸作为已知的条件下进一步分析偏振垂直光谱，将该垂直光谱对应的颗粒溶液的漫散射信息代入光漫散射下的近似表达式拟合得到颗粒的浓度信息。将实验结果与样品提供值进行了比对，并进一步分析了在获取颗粒数浓度时，颗粒直径的方差分布对结果的影响，最终验证了该实验方法的可行性。该方法的潜在应用包括对标准颗粒制造厂商的产品在线检测以及对牛奶制品中脂肪和蛋白质的浓度检测研究。

Particle Size and Number Density Online Analysis for Particle Suspension with Polarization-Differentiation Elastic Light Scattering Spectroscopy

The basic principle of polarization-differentiation elastic light scattering spectroscopy based techniques is that under the linear polarized light incidence, the singlely scattered light from the superficial biological tissue and diffusively scattered light from the deep tissue can be separated according to the difference of polarization characteristics. The novel point of the paper is to apply this method to the detection of particle suspension and, to realize the simultaneous measurement of its particle size and number density in its natural status. We design and build a coaxial cage optical system, and measure the backscatter signal at a specified angle from a polystyrene microsphere suspension. By controlling the polarization direction of incident light with a linear polarizer and adjusting the polarization direction of collected light with another linear polarizer, we obtain the parallel polarized elastic light scattering spectrum and cross polarized elastic light scattering spectrum. The difference between the two is the differential polarized elastic light scattering spectrum which include only the single scattering information of the particles. We thus compare this spectrum to the Mie scattering calculation and extract the particle size. We then also analyze the cross polarized elastic light scattering spectrum by applying the particle size already extracted. The analysis is based on the approximate expressions taking account of light diffusing, from which we are able to obtain the number density of the particle suspension. We compare our experimental outcomes with the manufacturer-provided values and further analyze the influence of the particle diameter standard deviation on the number density extraction, by which we finally verify the experimental method. The potential applications of the method include the on-line particle quality monitoring for particle manufacture as well as the fat and protein density detection of milk products.