气流场ESPI载频条纹图的消噪处理与相位提取方法

为拓展ESPI方法在流动可视化测量技术中的应用，对气流场ESPI载频条纹图进行了傅立叶变换、数字全低通滤波，和傅立叶逆变换的处理以消除散斑噪声，并直接将其替换为原散斑相关条纹图，进而成为保留了流场信息的高对比度、低噪声的灰度条纹图，便于提取原散斑图中流动相位信息。根据模拟数据确定了由这两种条纹图互换所引起的空间相移量和相应流场测量中的修正量。提出了用灰度扫描法对互换后的条纹图进行一维灰度扫描，由灰度计算得出气流扰动的一维相位差分布和流场一维温度分布；同时也用FTP法对该图进行了二维相位展开和温度分布计算，亦可对多帧条纹图进行时间轴上的逐点相位提取以计算其他流场参数。结果表明，计算数据与实测符合，方法简单易行，为在气流场参数测量中应用动态ESPI方法提供了一种实用有效的方法。

A Method of Removing Speckle Noise of Airflow Field ESPI Fringe Patterns and Phase Extraction

In order to extend the application range of ESPI to visualizing by a digital phase-only low pass filter and an inverse FFT were applied speckle noise, and then the original ESPI carrier fringe patterns were in real-time airflow motion, a FFT followed to ESPI carrier fringe patterns for removing replaced with the input images. The low-pass filtered patterns were regarded as normal interference fringes that in high-contrast and low noise, and airflow field information was contained in it. The change of spatial phase caused by the process of replacing image, and a correlative correction term in measurement of airflow field were obtained by a simulated test interferogram. A phase extraction method based on gray scanning was proposed for calculating phase difference in real-time airflow motion, and phase extraction using Fourier transformation profilometry was carried out in spatial domain, also along the timeaxis. The temperature distribution were calculated using phase extraction. This method can be used in dynamic ESPI measurements of airflow freld availably