用激光散射法测量大颗粒时使用衍射理论的误差

THE ERROR OF THE DIFFRACTION THEORY IN LARGE PARTICLE SIZE MEASUREMENT BY LASER SCATTERING METHOD

从实验数据，物理和几何光学的定性分析及Ｍｉｅ理论的严格计算等三个方面证明了即便是远远大于光波长的颗粒的散射光场，其实际光能分布与衍射理论给出的结果之间也有不可忽略的误差：表现为较大散射角上实际的散射光能远大于衍射理论光能。按照衍射理论的计算结果，这一误差等效于１μｍ左右的颗粒产生的光能分布。如果颗粒对光具有吸收性，则误差将显著减少。

n the basis of experimental data,quantitative analysis by both physical and geometic optics and calculation by Mie's scattering theory,it is proved that the error of the calculated light energy distribution by the diffraction theory could not be neglected in the laser paticle sizer even for large particles relative to the light wavelength. This error is distributed mainly over the scope of large scattering angle, which appoximately equal to the light energy distibution scattered by particles of diameter about 1μm.It is also proved that the error will strikingly decrease if the particles is absorbent of light.