用光脉动法在线测量颗粒浓度和粒度时，必须预知原始光强，但在在线测量中原始光强不仅难以测得，而且极易受环境影响产生变化。假设在短时间间隔内原始光强不发生变化，基于Gregory的光脉动法理论，可以得到颗粒数目浓度比。结合不同时刻浓度比以及透射光信号的标准偏差和均值，可以推导出原始透射背景光强。实验结果证明，该方法得到的原始透射背景光强和预先测得的原始透射背景光强吻合得很好，最大偏差小于1.1%。

For in-line measurement of particle size and concentration based on the light fluctuation method, the intensity of incident light must be pre-detected. However, it is very difficult to measure the incident light intensity during the in-line measurement because the incident light intensity is easily affected by many factors. A novel method based on Gregory′s light fluctuation method is proposed. The relation among the intensity of incident light, the ratio of particle concentrations at different time, the standard deviation and the mean value of the intensity of transmitted light is established. With those measurable parameters the intensity of incident light may be obtained. Experimental results agree well with the pre-detected value of the intensity of incident light, and the maximum deviation is less than 1.1%.