动态光散射信号自适应探测与处理研究

As a popular technique for nano-particle size analysis, dynamic light scattering is applied extensively in Physics, Chemistry, Biology and Material Science. However, it becomes more and more difficult to meet the growing requirements from nano-particle fundamental research and industry, due to its limitations, such as relative long measurement time, which last several minutes normally, narrow measurement range, which covers 10nm to 1000nm effectively, and etc. This project aims to develop a novel technology by introducing a serial adaptive methods into the signal processing of dynamic light scattering. First, an adaptive photon correlator will be designed, which can optimize its parameters according to the sample when the auto- or cross- correlation functions of the input photon intensity are calculated. It will be based on Field Programmable Gate Array chips and a Build-in system. Second, an adaptive joint inverse algorithm will be developed, which will involve more boundary condtions from the above adaptice correlator during its iteration process. A strategy of algrithms combination will be adopted. Third, adaptive opto-mechanics components will be designed, which will adjust the mechanics adaptively according to the correlation functions directly during the measurement. Finally, an adaptive dynamic light scattering prototype will be established. It is expected that, by self-optimizing the measurement parameters on-line, the typical measurement time can be reduced to less than 10 seconds, and the effective measurement range can be extended to 1nm to 5000nm. The utility improvement will be assessed systematically by comparing with the commercial traditional equipments The outcome of this study will provide novel methods and equipments for nano-particle research and industry. The short measurment time can support a realtime detection and control when the sample size vary fast; The wide measurement range can guarantee a sufficient region for large distribution of particle size. To the best of our knowldege, the adaptive dynamic light scattering has not been presented elsewhere, which demonstrate the creativity of this research.

动态光散射技术是纳米颗粒粒度分析的标准手段。然而，该技术典型测量时间长达数分钟，可靠测量范围在1000纳米以下，难以满足纳米颗粒测量领域日益增长的新要求。本项目试图在相关运算、数据反演和光机系统等信号探测与处理关键模块中引入自适应技术，力图使典型测量时间缩短至10秒钟以内，测量范围扩展至5000纳米，促使动态光散射技术应用范围从平衡稳态系统研究扩展至颗粒团聚、变性、包覆等非平衡系统的演化过程研究，并促进其从目前的点式测量向成像技术方向发展，为纳米颗粒研究领域提供新的技术方法与装备。研究内容包括基于动态参数配置的相关运算模式研究；自适应硬件光子相关器研制；基于参数传递的联合反拉普拉斯变换技术研究；自适应反演算法的开发等；并在此基础上，开发相应的光机系统，研制自适应动态光散射仪器样机。本项目的创新之处在于将自适应方法引入动态光散射技术的信号探测与处理中，未见有相关报导。

动态光散射技术主要用于纳米颗粒粒度、zeta电位等物性的表征，被国际标准化组织ISO推荐为标准方法。然而目前的动态光散射技术存在测量速度慢、测量范围窄、测量精度低等缺点，已制约了纳米颗粒测量技术的发展。随着纳米科技的发展，越来越多的研究领域要求快速测量大分散度颗粒系统的粒度分布，传统的动态光散射技术已难以满足上述要求，如何提高动态光散射技术在纳米颗粒物性表征中的精度和速度是目前该领域的研究热点。目前，虽然限制动态光散射仪测量速度和范围的原因较多，但信号探测与处理环节中模块的固化与相互独立是主要原因，在关键模块中引入自适应优化方法或是解决方案之一。本项目提出通过在光子相关器等重要零部件、反演算法、光机结构中引入自适应技术，从而可以极大地提高动态光散射技术的测量速度和测量范围，并且能在测量精度上也有一定的改善。主要的研究结果包括：研制了系列的自适应光子相关器，包括基于ARM的在线配置FPGA硬件自适应光子相关器、基于CPLD和FPGA的自适应光子相关器、基于FPGA的多路复用光子相关器和软件自适应光子相关器等四种；提出了自适应动态光散射测量方案，实现了测量参数的动态自适应配置；开发了基于并行计算的动态光散射数值仿系统；研究了自适应反演算法；研制了自适应动态光散射仪器样机，并通过了了中国合格评定国家认可委员会组织的能力验证。研制的自适应动态光散射技术及仪器样机在测量速度和测量范围等性能上有了很大提高，使得该技术的应用范围有望从目前的平衡稳态系统扩展到非稳态系统，从而可用于颗粒团聚、变性、包覆等颗粒系统演化过程研究；并促使动态光散射技术从目前的点式测量向成像技术方向发展，为系统微观体系的动态特性的空间分布及演变研究提供技术基础；还希望能促进该技术向实时在线化方向发展，从而应用于粉体工业的在线检测与分析。