脉冲红外相位线性调频Z变换

为了解决脉冲相位法(PPT,Pulse Phase Thermography)在处理红外检测数据时频率分辨率不够的问题,提出了一种新型的频域变换方法.利用快速傅里叶变换(FFT,Fast Fourier Transform)选择出包含特征频率的窄频带,对其进行线性调频Z变换(CZT,Chirp Z Transform),得到细化的频率结构.并将逐点像素分析后的结果重构出清晰的幅值和相位图像序列.在不增加采样时间的前提下获得了比PPT更高的频率分辨率.通过对铝制材料试件检测信号的对比分析,结果表明该算法可以对选频带进行有效细化,得到更精确的特征频率,有效降低了频谱泄露造成的误差. 

Pulse phase thermography chirp Z transform

In order to solve the problem of insufficient frequency resolution, occurring at the infrared detection data processing by the pulse phase thermography (PPT), a new frequency domain transform method was proposed. The fast Fourier transform (FFT) was utilized to choose the narrow frequency band included within the characteristic frequency, this band was processed by the chirp Z transform (CZT), the refined frequency structure was obtained. The clear amplitude and phase image sequences were reconstructed from the pixel-by-point analysis results. Without increasing the sampling time, a higher frequency resolution was achieve than the one of the PPT. Through the comparison of the detection signal from an aluminum material specimen, the results show that the algorithm can effectively refine the selected frequency band, get more precise characteristic frequency and effectively reduce the spectral leakage errors.