A Denoising Algorithm for Terahertz Time Domain Spectrum based on Lifting Wavelet Transform

Terahertz time domain spectroscopy has been widely used in tumor detection, chemical analysis and nondestructive testing. However, the measurement errors of terahertz time domain spectrum frequently occur because of vibration of experiment instrument platform or temperature and humidity changes. Lifting wavelet transform based on different wavelet basis functions was applied to the denoising of terahertz time domain spectrum of PTFE. The denoising results were compared with denoising results of wavelet soft threshold method. The wavelet soft threshold method got a highest signal to noise ratio (SNR) of 58.75 dB and a least root mean square error (RMSE) of 3.56*10(boolean AND)(-5), while lifting wavelet transform method achieved a highest SNR of 60.69 dB and a least RMSE of 2.85*10(boolean AND) (-5). These results imply that lifting wavelet transform performs better in terahertz spectrum denoising than wavelet soft threshold.