基于色散偏振度的乳化油光谱检测系统研究

以色散偏振光谱检测技术为背景，着重研究了乳化油颗粒的偏振光学特性及米散射物理模型，构建了色散偏振度光谱检测系统。在400～700 nm波长范围内，分别对四种样品进行了301个波段的光谱反射率采集。结合贝塞尔函数和汉克尔函数，推导出了入射光波长与散射光偏振振幅矢量的关系，提取了一个新的特征参数：色散偏振度（DODP）。在暗室条件下，对乳化油样品ND18和ND75进行测量，利用色散偏振公式计算出了样品在各测量波长处的偏振度值，验证了基于DODP值检测乳化油的可行性。研究发现，虽然米散射的解是由单个球体的衍射推导而来，但是只要它们的直径和组成相同，且彼此之间的距离比波长大，也同样可以用于任意数量的球的衍射。在这种情况下，被不同球体散射的光之间没有相干的相位关系，总散射能量等于被一个球体散射的能量乘以它们的整数。当观测平面与入射波电矢量振动方向之间的夹角Φ=0或者Φ=π／2时，散射光分量E(s)_θ或者E(s)_Φ消失。由于ND18的粒径比ND75的粒径小，所以ND18的前向散射波瓣较大，前向散射与后向散射的比值较小。在相同光照条件下，ND75的多次散射现象要比ND18严重。根据路径相关矩阵的理论，多次散射容易引起退偏振，二次辐射波会在角域内扩散和分布。因此，被测乳化油表面产生的散射次数与入射光能的阻尼能力成正比。由于乳化油表面入射光的能量耗散存在差异，因此能量耗散率与入射波矢量方向的前向散射振幅的分量成正比，且乳化油的偏振散射程度不同于入射光的偏振散射程度。实验结果表明，DODP可以反映出乳化油由多次色散引起的去偏振能力。由于模拟光源是自然光，所以计算散射光的偏振参数非常方便，可以大大缩短数据处理时间，减小实验误差。DODP不仅能够识别海水中的乳化油，而且能够区分不同浓度的污染物，准确识别出乳化油的边缘扩散。

Study on Spectral Detection System of Emulsified Oil Based on the Degree of Dispersion Polarization

Based on the spectrum detection technology of dispersion polarization, the optical polarization characteristics of emulsified oil particles and the Mie scattering physical model have been emphatically studied, and the spectrum detection system of dispersion polarization degree has been constructed. In the wavelength range of 400-700nm, the spectral reflectance of 301 bands was collected for four samples. Combining the Bessel function and Hankel function, the relationship between the wavelength of incident light and the polarization amplitude vector of the scattered light has been derived, and a new characteristic parameter has been extracted: the degree of dispersion polarization (DODP). Under darkroom conditions, the emulsified oil samples ND18 and ND75 were measured, and the polarization value of the sample at each measurement wavelength was calculated using the dispersion polarization formula, verifying the feasibility of detecting emulsified oil based on DODP value. This study found that although the solution of Mie scattering is derived from the diffraction of a single sphere. As long as their diameter and composition are the same, and the distance between each other is greater than the wavelength, They can also be used to diffract any number of balls. There is no coherent phase relationship between lightly scattered by different spheres, and the total scattered energy is equal to the energy scattered by a sphere multiplied by their integers. When the angle between the observation plane and the vibration direction of the incident wave electric vector is Φ=0 or Φ=π／2, the scattered light component E(s)_θ and E(s)_Φ disappears. Since the particle size of ND18 is smaller than that of ND75, the forward scattering lobe of ND18 is larger, and the ratio of forwarding scattering to backward scattering is small. Under the same lighting conditions, the multiple scattering of ND75 is more serious than that of ND18. According to the theory of path correlation matrix, multiple scattering is likely to cause depolarization, and secondary radiation waves will spread and distribute in the angular domain. Therefore, the number of scatterings generated on the surface of the emulsified oil measured is proportional to the damping capacity of the incident light energy. Due to the difference in energy dissipation of incident light on the surface of emulsified oil, the energy dissipation rate is proportional to the component of the forward scattering amplitude in the direction of the incident wave vector, and the degree of polarized scattering of emulsified oil is different from the degree of polarized scattering of incident light. Experimental results show that DODP can reflect emulsified oil’s depolarization ability caused by multiple dispersions. Since the simulated light source was natural light, it was very convenient to calculate the polarization parameters of scattered light, which could greatly shorten the data processing time and reduce the experimental error. DODP can identify emulsified oil in seawater and distinguish the concentration of pollutants and accurately identify the edge diffusion of emulsified oil.