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在光全散射法颗粒粒径测量中,基于米氏(Mie)理论的计算方法只能求出均匀球形粒子的消光系数,而且计算复杂。通过反常衍射近似(ADA)代替米消光系数,可以简化粒径分布的反演过程。对使用反常衍射近似方法计算圆柱形粒子消光系数的可行性以及限制条件进行深入的研究,并在非独立模式算法下,采用遗传算法反演粒径分布。仿真结果表明,当粒子的相对折射率在一定范围内时,利用反常衍射近似反演圆柱形粒子的粒径分布是完全可行的,反演结果稳定、可靠。对消光值测量结果加入3％相对误差时,反演误差为5．7％。该方法具有简单、直观、计算速度快等优点,适合颗粒粒径的在线测量。
In the light scattering method, the calculation method based on the Mie theory can only calculate the extinction coefficient of a uniform spherical particle, and the calculation is complicated. By replacing the extinction coefficient with the Abnormal Diffraction Approximation (ADA), the inversion of the particle size distribution can be simplified. The feasibility and limitation of calculating the extinction coefficient of cylindrical particles by using anomalous diffraction approximation method are studied deeply. Under the non-independent mode algorithm, the genetic algorithm is used to invert the particle size distribution. The simulation results show that when the relative refractive index of particles is within a certain range, it is feasible to approximate the particle size distribution of cylindrical particles by using the normal diffraction method. The inversion results are stable and reliable. When 3% relative error was added to the extinction measurement, the inversion error was 5.7%. The method has the advantages of simple, intuitive, fast calculation speed and is suitable for on-line measurement of particle size.