Abstract—Chemometric analysis was applied on terahertz
absorbance 3D images, in transmission. The goal is to
automatically discriminate some explosives on images and
quantify mixtures of RDX/PETN in the frequency range of 0.2 –
3 THz. Partial Least Square (PLS) was applied on THz
absorbance multispectral images to quantify individual product
inside pure samples and mixtures at each pixel on the image.
Then the best score obtained is used to display the samples’
images and provide the optimal frequencies combination for
erahertz spectral-imaging is an imaging technique that
utilizes the wave in the terahertz region of the
electromagnetic spectrum (3-0.03 mm; 0.1-10 THz) . It
was investigated in different fields such as biology,
pharmaceutical, security fields, etc., and allows getting
physical and chemical information about the inspected
samples by getting the dielectric response over several
decades of frequencies.
On the other hand, chemometrics technics showed powerful
capability in data analysis for discrimination, identification or
quantitation. As well as in terahertz science, chemometrics
was successfully applied on spectroscopy  and on imaging
 for various purposes.
Partial least square (PLS) is one of the chemometrics
multivariate analyses used to get chemical information on
multispectral data and to predict the amount of products in
samples. Different studies demonstrated the good ability of
PLS applied on THz spectra for quantification of different
chemical substances .
In the context of transportation security and in the aim of
not only identify some explosives but also to predict their
exact amount in the terahertz domain, we applied PLS
algorithm on multispectral terahertz images. This study was
pentaerythritoltetranitrate (PETN) in pure state and in mixtures
on each pixel of THz multispectral images.