提出的透过率起伏光谱分析法是一种新的颗粒测量方法。采用一细小光束照射匀速流动的颗粒系统，通过采集透射光起伏信号，经统计处理得到透过率的平均值与起伏谱。通过求解逆问题，从透过率的起伏谱中得到颗粒粒径分布信息，再结合透过率的平均值得到颗粒的体积分数信息。给出了关于单层颗粒透过率的平均值与起伏谱的理论表达式，并推广到三维单分散和多分散的颗粒系统。对粒径在32～425 μm内的稀薄颗粒系进行了部分实验测试和模拟计算，结果表明该方法可同时对颗粒粒径分布和体积分数进行有效测量。

Spectral analysis on the transmission fluctuations is a new method for measurements on large particles. Radiated by a narrow beam, the flowing particle system at a uniform velocity causes the transmission signal fluctuate violently. Both the average transmission and the spectrum of transmission fluctuations can be obtained statistically, which include the complete information on particle size distribution and particle concentration (volume fraction). By using the inverse algorithm, the particle size distribution may be extracted from the spectrum of transmission fluctuations and consequently the particle concentration can be achieved from the average transmission. The theoretical expression of the transmission fluctuation spectrum is established, for monolayer of mono-dispersed particles. The theory is then extended to a 3-dimensional system of mono-dispersed particles and further to that of poly-dispersed particles. Experimental test and simulation on dilute particle systems with particle diameters in the range 32～425 μm are performed, which shows that the method is valid to measure the particle size distribution and particle concentration simultaneously.