固体火箭发动机热防护层厚度的均匀性会影响发动机的工作性能，为了测量热防护层的厚度，设计了一种基于激光超声的热防护层厚度检测方案。通过分析热防护层激光超声测厚的特点，利用小波变换对采集的回波信号进行了降噪处理，采用小波变换模极大值法对两界面的位置特征信息进行了有效提取，实现了对热防护层厚度的非接触测量。试验结果表明，该方法的测量相对误差小于6.4%。

The extent of the thickness uniformity of the thermal protection layer of the solid rocket motor will affect the working performance of the engine. To measure the thickness of the thermal protection layer, a thermal protection layer thickness detection scheme based on laser ultrasonic is designed. By analyzing the characteristics of laser ultrasonic thickness measurement of thermal protection layer, the echo signal which was collected is denoised by wavelet transform, and the positional feature information of the two interfaces is effectively extracted by wavelet transform modulus maximum method, and hence non-contact measurement of the thickness of the thermal protection layer is realized. The experimental results show that the relative error measured by this method is within 6.4%.