Joachim Jonuscheit

Fraunhofer Institute for Industrial Mathematics

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R. Beigang

University of Kaiserslautern

Daniel Molter

Fraunhofer Institute for Industrial Mathematics

Jens Klier

Fraunhofer Institute for Industrial Mathematics

Georg von Freymann

Fraunhofer Institute for Industrial Mathematics

Frank Ellrich

TH Bingen University of Applied Sciences

Fabian Friederich

Fraunhofer Institute for Industrial Mathematics

Stefan Weber

University of Freiburg

Carsten Matheis

Fraunhofer Institute for Industrial Mathematics

Marijke Vandewal

Royal Military Academy

S. Wohnsiedler

Fraunhofer Institute for Physical Measurement Techniques

Cooperative Institutions

Fraunhofer Institute for Industrial Mathematics

University of Kaiserslautern

Fraunhofer Institute for Physical Measurement Techniques

Fraunhofer Society

Centre National de la Recherche Scientifique

Friedrich-Alexander-Universität Erlangen-Nürnberg

Goethe University Frankfurt

Ludwig-Maximilians-Universität München

LMU Klinikum

Military University of Technology in Warsaw

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A pulsed THz Imaging System with a line focus and a balanced 1-D detection scheme with two industrial CCD line-scan cameras

Optics Express (2010)

Christian Wiegand Michael Herrmann Sebastian Bachtler Jens Klier Daniel Molter

We present a pulsed THz Imaging System with a line focus intended to speed up measurements. A balanced 1-D detection scheme working with two industrial line-scan cameras is used. The instrument is implemented without the need for an amplified laser system, increasing the industrial applicability. The instrumental characteristics are determined.

Line (geometry)

10.1364/oe.18.005595

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Citations (6)

One-dimensional vibrational coherent anti-Stokes Raman-scattering thermometry

Optics Letters (1996)

Joachim Jonuscheit Albert Thumann Martin Schenk Thomas Seeger Alfred Leipertz

Quantitative one-dimensional single-pulse temperature measurements by broadband N2 vibrational coherent anti-Stokes Raman scattering (CARS) are presented. A planar BOXCARS phase-matching geometry was used to generate the CARS signal along a 6.16-mm path positioned perpendicularly to the beam propagation. Depending on the imaging optics used, a spatial resolution of 86 μm was achieved. The applicability of this technique for measuring temperature gradients is demonstrated in a premixed laminar CH4–air flame.

10.1364/ol.21.001532

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Citations (35)

Multilayer terahertz thickness imaging at 1.6-kHz pixel rate

Daniel Molter Kim-Sophie Ellenberger Jens Klier Stefan Weber Joachim Jonuscheit

Terahertz layer thickness measurements is one of the most promising fields of applications for terahertz technology. Measuring subwavelength layers in multilayer systems is most commonly achieved by applying retrieval algorithms. These algorithms are computational demanding, which makes it hard for the evaluation to keep up with the increasing speed of modern terahertz systems. ECOPS-based systems now achieve measurement rates above 1 kHz. By applying a highly efficient algorithm based on desktop-grade CPU, we achieve multilayer imaging at 1.6 kHz measurement rate. A three-layer system on a metal disk of 300 mm diameter is measured in 2.5 minutes with 240000 pixels.

10.1117/12.2615320

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Simulation and experiment of terahertz stand-off detection

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2009)

S. Wohnsiedler M. Theuer Michael Herrmann Shany Islam Joachim Jonuscheit

Terahertz (THz) spectroscopy is a promising technique for the stand-off detection and characterization of hidden objects. The THz band is particularly well suited firstly because THz radiation penetrates many dielectrics like clothes and secondly because many potentially hazardous substances have characteristic signatures in the THz spectral region. In order to utilize the full potential of THz radiation for detecting possible hazards and recognizing characteristic signatures, disturbing influences must be accounted for. We have performed experiments and simulations in order to investigate the limits of terahertz stand-off detection. A special emphasis is paid on humidity in ambient air and properties of the sample like surface roughness, alignment and interfaces. Water vapor absorption strongly affects the THz spectra. Since the absorption lines are strong and narrow, the calculation must be precise. We have checked various models well-known in meteorology covering the infrared and the microwave region of the electromagnetic spectrum. By extending the models into the THz region, an accurate description of the measured spectral absorption is achieved. In our studies transmission spectra for different substances were tested. In a reflection scheme metallized sandpaper of various grit sizes was used to determine the influences of different surface properties. Further measurements were performed for different tilt angles to analyze the influence of the surface roughness. We are currently creating a look-up table to show which parts of the THz spectrum can be used for THz stand-off detection.

Sandpaper

10.1117/12.808871

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Citations (17)

Terahertz detection of explosive materials and dangerous objects

HAL (Le Centre pour la Communication Scientifique Directe) (2015)

Norbert Pałka Marcin Kowalski Michał Walczakowski M. Szustakowski W. Ciurapiński

Explosive detection

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Untersuchung von diodenlaserbasierten Mehrkomponenten-Konzentrationsmesssystemen zur Gasanalyse (Investigation of Diode Laser-Based Multi-Species Gas Sensor Concepts)

tm - Technisches Messen (2001)

Jan Egermann Joachim Jonuscheit Thomas Seeger Alfred Leipertz

Es wird ein auf dem Prinzip der Ramanspektroskopie beruhendes Messsystem zur Konzentrations-bestimmung grundlegend hinsichtlich seiner Nutzbarkeit in der Gasanalyse untersucht. Das Detektorsystem nutzt kommerziell erhältliche Lasersysteme im sichtbaren bis zum nahinfraroten Bereich. Eingesetzt wurden sowohl ein diodenlasergepumpter Festkörperlaser als auch ein Diodenlasersystem. Die Nutzung der Ramanspektroskopie ermöglicht bei einer frei wählbaren Einstrahlfrequenz die simultane Registrierung der verschiedenen im Probenvolumen vorliegenden Moleküle und ist somit messtechnisch nicht auf einzelne Moleküle beschränkt. Als Nutzungsmöglichkeit dieser Technik wird die präzise Analyse von Verbrennungsgasen zur Heizwertbestimmung vorgestellt. Auch die Analyse von Anästhesiegasen erscheint möglich.

10.1524/teme.2001.68.9.400

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influences of real-world conditions on terahertz stand-off detection: Simulation and experiment

S. Wohnsiedler M. Theuer Michael Herrmann Shany Islam Joachim Jonuscheit

Terahertz spectroscopy has become a well-established tool under laboratory conditions but terahertz stand-off detection in the real world is hampered by a number of influences related to the environment and the sample properties such as air humidity, surface roughness and angle of detection. A terahertz stand-off system must be calibrated in order to account for these influences. We have performed experiments and simulations in order to probe the limits of terahertz stand-off detection under real-world conditions.

Sample (material)

10.1109/icimw.2008.4665848

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A 3D THz image processing methodology for a fully integrated, semi-automatic and near real-time operational system

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2012)

Anna Brook Edison Cristofani Marijke Vandewal Carsten Matheis Joachim Jonuscheit

The present study proposes a fully integrated, semi-automatic and near real-time mode-operated image processing methodology developed for Frequency-Modulated Continuous-Wave (FMCW) THz images with the center frequencies around: 100 GHz and 300 GHz. The quality control of aeronautics composite multi-layered materials and structures using Non-Destructive Testing is the main focus of this work. Image processing is applied on the 3-D images to extract useful information. The data is processed by extracting areas of interest. The detected areas are subjected to image analysis for more particular investigation managed by a spatial model. Finally, the post-processing stage examines and evaluates the spatial accuracy of the extracted information.

Data Processing

10.1117/12.919382

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Citations (4)

Automatically Detecting Peaks in Terahertz Time-Domain Spectroscopy

Henrike Stephani Joachim Jonuscheit Christoph Robiné Bettina Heise

To classify spectroscopic measurements it is necessary to have comparable methods of evaluation. In Terahertz (THz) time-domain spectroscopy, as a new technology, neither the presentation of the data nor the peak detection is standardized yet. We propose a procedure for automatic peak extraction in THz spectra of chemical compounds. After preprocessing in the time-domain, we use a variance based algorithm for determining the valid frequency region. We furthermore propose a baseline correction using simulated THz spectra. We illustrate how this procedure works on the example of hyperspectral THz measurements of six chemical compounds. Subsequently we propose to use unsupervised classification on the thus processed data to robustly detect the characteristic peaks of a compound.

Terahertz time-domain spectroscopy

10.1109/icpr.2010.1085

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Citations (7)

Assignment of coherent anti-stokes Raman spectra of the ν1 bands of ammonia: 14ND3 and 15ND3

Journal of Molecular Structure (1999)

M. Stamova S. Anders Joachim Jonuscheit H. W. Schrötter P. Pracna

Isotopomers

10.1016/s0022-2860(98)00793-5

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Citations (6)