使用图像法测量崩塌角存在测量标准差大的问题（0.5°左右）。为了解决这个问题，采用一种新的基于动态散斑对比度的崩塌角在线测量方法和系统进行了理论分析和实验验证。当激光照射到滚筒内运动的颗粒上，在远场形成动态散斑，利用线阵CCD相机得到散斑随时间变化图像，通过分析散斑图像的对比度计算出颗粒流的速度波动，再找出两次崩塌的间隔时间，最后利用转速乘以间隔时间就可以得到崩塌角。实验中采用粒径为1mm~1.25mm的玻璃珠，分别采用动态散斑法和图像法测量了不同转速下的休止角的数据。结果表明，动态散斑对比度崩塌角在线法时空分辨率高，测得数据的标准差较小、重复性好、数据拟合的确定系数高。这一结果对滚筒内颗粒流的在线测量和科学研究是有帮助的。

Image method was often used to measure the slumping angles. However, the method has a problem that measurement standard deviation is large (about 0.5°). In order to resolve the problems, online measurement method of dynamic speckle contrast slumping angle was proposed. When laser irradiated on the granules in rotating drum, dynamic speckle formed in far field. Linear CCD camera was used to get the speckle image with the changing of time. Through the analysis of the contrast of speckle images, the speed fluctuation of granular flows was calculated and interval time between two slumping angles was found. Finally slumping angles can be calculated out by using speed multiplied by interval time. Glass beads with diameter distribution of 1mm~1.25mm were used. Dynamic speckle contrast method and image method were used respectively to measure the slumping angles under different rotational speeds. The results show that online measurement of dynamic speckle contrast slumping angle is high spatial and temporal resolution. The standard deviation of measurement data is small, repeatability is better and the determination of data fitting coefficient is high. Dynamic speckle contrast method is applicable for online measurement and scientific research of granular flow in rotating drums.