We introduced several approaches of terahertz wavefront phase retrieval from intensity measured in a volumetric grid. Our developments include several experimental solutions for the registration of multiple intensity distributions spaced along the optical axis for two types of terahertz sources, namely Gunn diode with frequency multiplication chain and quantum cascade laser. We implemented several measurement modes: (i) sequential raster scanning by single Schottky diode with two lock-in amplifiers, complimentary tuned to different sensitivities for high dynamic range recording; (ii) step by step registration on matrix photodetectors, with averaging over several images for every measurement plane; (iii) continuous measurement during the displacement of the motorized translation stage. The high dynamic range data acquisition allowed us to successfully implement single-beam terahertz surface profilometry in the reflection, while the on-the-go recording ensures the shortest measurement times. In addition, we experimentally appraised two matrix detectors (INO and I2S) and applied several phase retrieval algorithms which proved their effectiveness in various experimental conditions, namely for the intensity registration in various diffraction zones and axial measurement plane allocations.
sequences. Sizing, surface and volume rendering can be extracted and compared with targeted dimensions. In this work, we use millimeter wave systems tomographic system (100 and 300 GHz), frequency modulated systems (100 and 300 GHz), and pulse time domain systems (100 GHz to 4 THz) for non destructive characterization of 3D printed additive manufacturing parts. The aim of this talk to to show the advantages and disadvantages of several techniques to define their application aera. This work is associated to a data processing analysis using automated segmentation, extracting of the different volumes of interest (VOI) composing the sample. A mesh is performed for each VOI to numerically calculate the dimensions, surfaces and volume which leads to 3D visualization and dimensional measurements. Overall sequence is implemented onto unique software and validated through different sample analysis.
Recent innovations in photonics and nanotechnology are now enabling terahertz (THz) research to be applied in many industrial fields such as homeland security, information and communications technology (ICT), biology and medical science, non-destructive tests or quality control of food and agricultural products. Still many challenges are to be addressed, the main one being to provide THz systems with sufficient signal to noise ratio when operated in real industrials conditions. In addition, cost is a key lock that hampers the spread of this technology but it is clear that cost-effective sources and detectors compatible with standard microelectronics will drive down the overall cost, and in particular will make THz imaging accessible for industrial use. In order to bring THz imaging to industry, Leti has been developing over the past decade complementary CMOS-compatible uncooled imaging 2D-array technologies: antenna-coupled bolometers and Field Effect Transistor detectors. In addition, CEATech built a test platform dedicated to the development of industrial prototypes of photonics technologies. In particular, in collaboration with i2S, this platform includes the TZCAM camera equipped with Leti’s 320×240 bolometric pixel array and gives access to a full industrial THz imaging chain that is essential for maturation of this emerging technology. This paper gives an overview of these developments and illustrates industrial applications with examples of uncooled THz imaging tests, e.g. opaque object 2D inspection or 3D tomography.
Detection of explosives has always been a priority for homeland security. Jointly, terahertz spectroscopy and imaging are emerging and promising candidates as contactless and safe systems. In this work, we treated data resulting from hyperspectral imaging obtained by THz-time domain spectroscopy, with chemometric tools. We found efficient identification and sorting of targeted explosives in the case of pure and mixture samples. In this aim, we applied to images Principal Component Analysis (PCA) to discriminate between RDX, PETN and mixtures of the two materials, using the absorbance as the key-parameter. Then we applied Partial Least Squares-Discriminant Analysis (PLS-DA) to each pixel of the hyperspectral images to sort the explosives into different classes. The results clearly show successful identification and categorization of the explosives under study.
In this paper we present an innovative data and image processing sequence to perform non-destructive inspection from 3D terahertz (THz) images. We develop all the steps starting from a 3D tomographic reconstruction of a sample from its radiographs acquired with a monochromatic millimetre wave imaging system. Thus an automated segmentation provides the different volumes of interest (VOI) composing the sample. Then a 3D visualization and dimensional measurements are performed on these VOI, separately, in order to provide an accurate nondestructive testing (NDT) of the studied sample. This sequence is implemented onto an unique software and validated through the analysis of different objects
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.