本文认为文献[1]的结论是错误的.作者从标量衍射理论的瑞利--索末菲公式出发,导出了描述通过照明波发散中心并与衍射屏平行的观察面所接受到的衍射花样的夫朗和费衍射公式及其成立条件.并将上述公式应用到二维随机分布的微粒系统,从而导出了描述此系统相应的夫朗和费衍射花样的光强公式及粒径测量公式.指出当用夫朗和费衍射法测量微粒直径时,只要应用文中导出的在大衍射角情形下亦成立的测量公式,便能得到正确的结果,并不存在文献[1]所提出的随衍射角增大而增加的系统误差.相反,对于偶然误差而言,当衍射距离不变时,随着衍射角的增加,偶然误差反而减小,测量的准确度增加.

It is pointed out that the conclusion in the reference [1] is not correct. The formula for Fraunhofer diffraction, which describes the diffraction pattern on an observing screen locating at the divergence center of an illuminating spherical wave and being parallel with the diffracting screen, is deduced from the Rayleigh-Sommerfeld formula of the scalar diffraction theory. The application condition of the formula is also discussed. Applying the formula to the particles scattered randomly over a 2-D plate, the light intensity formula and the measurement formula for a particle diameter, which describe the Fraunhofer diffraction pattern of the particles, are derived. The authors demonstrated that, when the Fraunhofer diffraction method is used to measure the average dimension of the particles, it is necessary to adopt the formula for the case of a big diffraction angle, the related correct result can be obtained. There is not any systematic error mentioned in reference [1] that increases with the value of diffractionangle.On the contrary,under the condition that the diffracting distance doesn't change,the measurement accuracy increases and the accidental error decreases as the diffraction abgle increases.