讨论了在近场接收条件下颗粒的消光特性。 计算表明: 在近场接收时, 颗粒的实际消光特性与远场接收相比, 存在很大的区别实际消光系数不但同颗粒的性质和大小有关, 而且与颗粒在光束中的位置相联系。 对于大颗粒, 近场和远场间的消光系数在数值上也有很大差异, 如果采用近场接收来测量颗粒的大小, 必须考虑这些因素的影响, 否则将极大增加测量误差。 还论述了近场接收时消光法测量颗粒时测量区定义中的问题, 论证了如果能恰当定义测量区, 可以把由于采用近场接收带来的误差限制在一个可接受的范围之内。

The particle extinction characteristics, determined by receiption in short distance, is discussed. Calculations show that the extinction coefficient in short distance, especially for the large particles, is very different from that in long distance, i.e. it is not only dependent on particle properties, but also the location of particle in measuring beam. Therefore, the above mentioned factors should be taken into account when the short distance receiption is used to measure the particle size. Furthermore, the way to define the measurement volume under the receiption in short distance is also described, the particle diameter and concentration can be clearly determined by above mentioned method.