激光二极管自混频技术可用于纳米颗粒的测量，采用多通道带通滤波技术分别测量了180，100，60 nm三种纳米颗粒，获得自混频信号的频带功率谱(PS-BPF)。作为比较，对实时提取的自混频信号进行傅里叶变换得到功率谱密度(PSD)函数。分别对PSD函数和PS-BPF反演计算得到颗粒粒径分布。结果显示：两种方法得到的颗粒粒径分布基本一致，并与商用仪器测试结果吻合。对两种处理方式的模式矩阵分析表明，多通道带通滤波技术明显优于PSD函数处理方式。

激光自混频技术可用于纳米颗粒和纳米流体的探测。在纳米流体自混频信号自相关函数的基础上，理论推导了功率谱函数的表达式。结果表明，纳米流体的激光自混频信号功率谱是洛伦兹线型和高斯线型的卷积，即佛赫特(Voigt)线型。通过数值计算研究了各种典型情况下激光自混频信号功率谱的频谱特征，颗粒定向运动速度决定了多普勒频移和高斯线宽，颗粒粒度决定了洛伦兹线型的宽度，颗粒粒度和速度与功率谱之间的对应关系为纳米流体的测量提供了理论基础。

In this letter, the technique of laser self-mixing effect is employed for nano-particle size analysis. In contrast to the photon correlation spectroscopy (PCS) and photon cross correlation spectroscopy (PCCS), the main advantages of this technique are sensitive, compact, low-cost, and simple experimental setup etc. An improved Kaczmarz projection method is developed in the inversion problem to extract the particle size distribution. The experimental results prove that nano-particle size can be measured reasonably by using the self-mixing effect technique combined with the improved projection algorithm.