Efficiency of using correlation function for estimation of probability of substance detection on the base of THz spectral dynamics

摘要

One of the problems arising in Time-Domain THz spectroscopy for the problem of security is the developing thecriteria for assessment of probability for the detection and identification of the explosive and drugs. We analyze theefficiency of using the correlation function and another functional (more exactly, spectral norm) for this aim. Thesecriteria are applied to spectral lines dynamics. For increasing the reliability of the assessment we subtract the averagedvalue of THz signal during time of analysis of the signal: it means deleting the constant from this part of the signal.Because of this, we can increase the contrast of assessment. We compare application of the Fourier-Gabor transform with unbounded (for example, Gaussian) window, which slides along the signal, for finding the spectral lines dynamics with application of the Fourier transform in short time interval (FTST), in which the Fourier transform is applied to parts of the signals, for the same aim. These methods are close each to other. Nevertheless, they differ by series of frequencies which they use. It is important for practice that the optimal window shape depends on chosen method for obtaining the spectral dynamics. The probability enhancements if we can find the train of pulses with different frequencies, which follow sequentially. We show that there is possibility to get pure spectral lines dynamics even under the condition of distorted spectrum of the substance response on the action of the THz pulse.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.