Research On Fiber Optic Dynamic Light Scattering Particle Analyzer

Dynamic light scattering (DLS) technique has been widely used in measuring the particle sizes and the sizes distribution of submicron and nanometer particles suspended in suspensions. At present, this technique has been used in various fields of industrial production. The traditional DLS system is bulky. The scattering light caused by particles was transmitted in the air, and was easily interfered by dusts and external vibrations. This caused low signal-noise ratio of the system, and affected the measuring accuracy of the particle sizes. In order to overcome the shortcomings of the traditional DLS, this paper studied the fiber optic dynamic light scattering particle analyzer.The main study contents of this paper consist of:1、This paper compared the coupling efficiency that the scattering light coupled to the single mode fiber and multimode fiber respectively. Using the single mode fiber and multimode fiber received the scattering light, measured the scattering light power out of the fiber, and compared the particle analyzer performance differences. The single mode fiber had low coupling efficiency, this caused small flux received by photomultiplier, and the signal to noise ratio of the autocorrelation function curve was low. The multimode fiber could overcome this problem, had high coupling efficiency, and could improve the signal to noise ratio of autocorrelation function curve.2、This paper studied how to improve the coherence of the system by analyzing the coherence solid angle, coherence area and the scattering volume. The scattering volume was a three dimensional source, the coherence solid angle and the size of scattering volume could be got from the schematic diagram for the light-scattering geometry. By the VanCittert Zernike theorem, the size of the scattering volume was calculated. These studies showed that the divergence angle of the receiving probe would be smaller than the component in the y-z plane of coherence solid angle, and the receiving area of the photomultiplier would not be larger than the coherence area, and the small scattering volume could improve the scattering light power.3、This paper designed the input light path and the receiving light path. The focal length of the lens was calculated by the relational expression between the focal length and the diameter of the focus spot. The receiving light path was designed. According to the conditions of the light-to-fiber, this paper calculated the size of the aperture and the distance between the aperture and the fiber, and the fiber was processed by stripping coating, cleaning and cutting, then the scattering light was coupled to the fiber. This paper studied the optical path alignment. Using 1/2 approximation theory completed the optical path alignment.5、Using the designed analyzer measured five different particle sizes polystyrene suspensions, and built a traditional DLS system to measure the same particles. The comparisons and analysis for the two measuring results had been made. The comparisons showed that the fiber optic dynamic light scattering particle analyzer could improve the measuring accuracy.This paper based on the dynamic light scattering theory, used fiber optic technology, and developed a fiber optic dynamic light scattering particle analyzer. The analyzer has small volume, the scattering light is transmitted in the fiber optic, and the analyzer is not interfered by dusts and external vibrations. So far, the development of the fiber optic dynamic light scatter particle analyze in our country comes late the developed country. The studies in this paper better promote the development of the fiber optic dynamic light scatter particle analyzer industries.