小角弹性光散射粒径测量技术与准确性验证

Measurement Technique and Verification of Accuracy for Particle Sizing by Low Angle Elastic Light Scattering

改变了用中心有孔的环形光电元件接收前向散射光的传统做法,选择采用高灵敏度、低噪声、高分辨率带冷却的CCD采集散射光。采用光导纤维使透射光导出光轴,从CCD采集到的图像得到光强随散射角变化的分布曲线,用米氏散射程序反算出粒径分布;采用CCD为接收设备提高了测量系统的灵敏度和角度分辨率,使测量稀薄液雾或悬浊液的粒径分布成为可能。尽管激光散射粒径测量方法从测量原理上看更加准确,但此测量技术不是利用颗粒的放大成像确定粒径,不直观,通常需要验证激光粒径测量结果的准确性,常采用经其他光学方法测量过的标准粒子验证。提出了一种非光学的准确性验证方法,即利用单分散液滴串发生器产生的大小可控的等直径、等间距液滴串来验证小角弹性光散射粒径测量系统的准确性。

Instead of using the traditional detectors made of a series of concentric annular rings with a small aperture in the center, a high sensitivity, low noise, high resolution and cooled CCD is employed to detect the scattering pattern. An optical fiber is placed in the focal point of the receiver lens to make the transmitted light away from the owical axis. The image of scattering pattern recorded by CCD can be processed to get the curves of light intensity distribution with the scattering angle. Further, the particle size distribution can be calculated by Mie scattering code with inversion technique. It is possible to measure very diluted dispersions or fogs with CCD based low angle elastic light scattering measurement system due to its high sensitivity, high angular resolution. Although low angle elastic light scattering seems a more accurate method for its measurement principle, it is not an intuitive method. Normally the accuracy of laser particle sizing is verified by standard particles which are measured by other optical methods. A non-optical method is suggested. A mono-disperse droplet generator is used to produce a chain of droplets with same size, same droplet spacing to verify the laser scattering droplet sizing results.