Displacement Mode Analysis Method for Data Processing of Photonic Doppler Velocimetry

Abstract

The short time Fourier transform (STFT) and continuous wavelet transform (CWT) cannot resolve slowly varying velocity at low velocity stage in most photonic Doppler velocimetry (PDV) data. A new analysis method based on Fourier transform is presented to overcome this shortcoming. Instead of extracting the frequency of interference signal for velocity analysis, the new method uses a modified Fourier transform to analysis the phase of signal, and converts phase to displacement or velocity. The validity of the proposed method is examined in experimental data of a plate-impact experiment, which distinguishes the elastic-plastic properties of Fe sample. The method not only uses all sampling points of the raw data, but also has a higher velocity resolutions especially for low velocity stage. The method is a supplement to STFT and CWT method.

Windowed Fourier Transform Filter Method with Improved Threshold

“…滤波的常用方法有 Gabor 滤波 [12] 、 小波变换滤波 [13][14] 、 窗口傅里叶变换滤波等。其中以窗口傅里叶变换滤波 方法的滤波效果最佳。窗口傅里叶变换滤波的精髓在于对频谱系数进行处理， 目前对频谱系数进行处理是 采用固定阈值法。这种固定阈值的算法由于对噪声引起的小的频谱系数进行归零， 可以取得较好的去噪效 果。但由于其阈值函数不连续， 在阈值附近具有突变， 会对一些大的噪声频谱系数有所保留， 对小的信息的 频谱系数造成丢失。 针 对 窗 口 傅 里 叶 变 换 [6,[15][16]…”