提出了一种简便的激光自混合散斑干涉测量流体速度的方法。根据散斑和法布里珀罗腔的理论，提出了半导体激光器的自混合散斑干涉模型。研究了流体运动时在半导体激光器内产生的自混合散斑干涉效应(SMPI)，给出了激光器输出增益的变化及其概率密度分布。得到了激光自混合散斑干涉平均频率与流体速度之间的关系。模拟计算和实验结果验证了这个关系。利用散斑干涉的平均频率与流体速度的关系测量了高分子材料溶液的速度，并在溶液浓度和背景光变化时，对流体速度进行了测量、比较和分析。实验表明，在溶液浓度不太低时，测量误差小于8％。

The theoretical analysis and experimental result of self-mixing laser speckle interference (SMSI) velocimeter for flow measurement are presented based on the theory of Fabry-Pérot (F-P) cavity model. The mean speckle frequency reflects the activity of flow. The variation of gain and distribution of probability density are given. The computer simulation shows the linear relation between the mean speckle frequency and velocity of flow, and experimental result proves relation. The velocity of glutin solution is measured by this linear relation. The effect of background and concentration of flow are considered in the experiment. When the concentration of flow is appropriate, the error of experiment is less than 8%. The results of experiment show this method is useful for measurement of flow.