Research Center for Non Destructive Testing Gmb

Linz, Austria

Research Center for Non Destructive Testing Gmb

Linz, Austria
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Berer T.,Research Center for Non Destructive Testing Gmb | Burgholzer P.,Research Center for Non Destructive Testing Gmb | Haltmeier M.,University of Innsbruck
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2017

Fast data acquisition is a central aspect of photoacoustic imaging. Increasing the imaging speed is especially crucial for optical detection schemes where an optical interrogation beam is scanned along a planar detection surface and the ultrasonic waves are recorded at each position sequentially. In this work, we demonstrate that the number of measurements in photoacoustic imaging can significantly be reduced by using techniques of compressed sensing. A main requirement in compressed sensing is the sparsity of the unknowns to be recovered. Sparsity of the pressure wave as a function of space and time is not valid directly. Therefore, we introduce the concept of sparsifying temporal transforms for three-dimensional photoacoustic imaging. We present reconstruction results for simulated data verifying that the proposed compressed sensing scheme allows a significant reduction of the number of spatial measurements without sacrificing the spatial resolution. © 2017 SPIE.


Leiss-Holzinger E.,Research Center for Non Destructive Testing Gmb | Bauer-Marschallinger J.,Research Center for Non Destructive Testing Gmb | Berer T.,Research Center for Non Destructive Testing Gmb
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2017

We present a multimodal optical setup, allowing non-contact photoacoustic imaging (PAI) and optical coherence tomography (OCT). Optical coherence tomography is sensitive to changes in the specimen's refractive index, thereby offering complementary information to photoacoustic signals which are induced by light absorption. A multimodal setup, allowing OCT and photoacoustic measurements, should ideally not rely on any physical contact to a specimen and, thus, commonly used transducers for photoacoustic signal detection which require acoustic coupling to the specimen should be avoided. In this work photoacoustic signals are acquired by measuring the surface displacement of a specimen using a fiber-optic Mach-Zehnder interferometer. Photoacoustic signals are excited with a Nd:YAG pulse laser. The interferometer for non-contact photoacoustic detection and the OCT system are realized in the same fiber-optic network. Light from the PAI detection laser and the OCT source are multiplexed into a single optical fiber and the same objective is used for both imaging modalities. Light reflected from specimens is demultiplexed and guided to the respective imaging systems. To allow fast non-contact PAI and OCT imaging the detection spot is scanned across the specimens' surface using a galvanometer scanner. As the same fiber-network and optical components are used for photoacoustic and OCT imaging the obtained, images are co-registered intrinsically. Imaging is demonstrated on a tissue mimicking sample. © 2017 SPIE.


Hochreiner A.,Research Center for Non Destructive Testing Gmb | Bauer-Marschallinger J.,Research Center for Non Destructive Testing Gmb | Burgholzer P.,Research Center for Non Destructive Testing Gmb | Jakoby B.,Johannes Kepler University | Berer T.,Research Center for Non Destructive Testing Gmb
Biomedical Optics Express | Year: 2013

In photoacoustic imaging the ultrasonic signals are usually detected by contacting transducers. For some applications contact with the tissue should be avoided. As alternatives to contacting transducers interferometric means can be used to acquire photoacoustic signals remotely. In this paper we report on non-contact three and two dimensional photoacoustic imaging using an optical fiber-based Mach-Zehnder interferometer. A detection beam is transmitted through an optical fiber network onto the surface of the specimen. Back reflected light is collected and coupled into the same optical fiber. To achieve a high signal/noise ratio the reflected light is amplified by means of optical amplification with an erbium doped fiber amplifier before demodulation. After data acquisition the initial pressure distribution is reconstructed by a Fourier domain reconstruction algorithm. We present remote photoacoustic imaging of a tissue mimicking phantom and on chicken skin. © 2013 Optical Society of America.


Jordens C.,TU Braunschweig | Scheller M.,TU Braunschweig | Wietzke S.,TU Braunschweig | Romeike D.,TU Braunschweig | And 5 more authors.
Composites Science and Technology | Year: 2010

We employ terahertz time-domain spectroscopy (THz TDS), a novel, non-destructive testing method, to study the fibre orientation and fibre content in reinforced plastics. The birefringent properties of plastics filled with differing amounts of short glass fibres are measured at frequencies from 100 GHz up to 1 THz. To predict the permittivity of the experimentally examined composite materials, we use an effective medium theory first introduced by Polder and van Santen. On the basis of the measured data and this model, we deduce the additive content ξ, the preferential orientation of the fibres φ and the fraction of orientated fibres a. Our findings agree well with corresponding mold flow simulations performed with commercially available software. © 2009 Elsevier Ltd. All rights reserved.


Nuster R.,Research Center for Non Destructive Testing GmbH | Nuster R.,University of Graz | Gruen H.,Research Center for Non Destructive Testing GmbH | Reitinger B.,Research Center for Non Destructive Testing GmbH | And 4 more authors.
Optics Letters | Year: 2011

An optical detection setup consisting of a focused laser beam fed into a downstream Fabry-Perot interferometer (FPI) for demodulation of acoustically generated optical phase variations is investigated for its applicability in photoacoustic tomography. The device measures the time derivative of acoustic signals integrated along the beam. Compared to a setup where the detection beam is part of a Mach-Zehnder interferometer, the signal-to-noise ratio of the FPI is lower, but the image quality of the two devices is similar. Using the FPI in a photoacoustic tomograph allows scanning the probe beam around the imaging object without moving the latter. © 2011 Optical Society of America.


Langer G.,Christian Doppler Laboratory | Bouchal K.-D.,Research Center for Non Destructive Testing Gmb | Grun H.,Research Center for Non Destructive Testing Gmb | Burgholzer P.,Christian Doppler Laboratory | And 3 more authors.
Optics Express | Year: 2013

In the present paper we demonstrate the possibility to image dyed solids, i.e. Rhodamine B dyed polyethylene spheres, by means of two-photon absorption-induced photoacoustic scanning microscopy. A two-photon luminescence image is recorded simultaneously with the photoacoustic image and we show that location and size of the photoacoustic and luminescence image match. In the experiments photoacoustic signals and luminescence signals are generated by pulses from a femtosecond laser. Photoacoustic signals are acquired with a hydrophone; luminescence signals with a spectrometer or an avalanche photo diode. In addition we derive the expected dependencies between excitation intensity and photoacoustic signal for single-photon absorption, two-photon absorption and for the combination of both. In order to verify our setup and evaluation method the theoretical predictions are compared with experimental results for liquid and solid specimens, i.e. a carbon fiber, Rhodamine B solution, silicon, and Rhodamine B dyed microspheres. The results suggest that the photoacoustic signals from the Rhodamine B dyed microspheres do indeed stem from two-photon absorption. © 2013 Optical Society of America.


Veres I.A.,Research Center for Non Destructive Testing Gmb | Berer T.,Research Center for Non Destructive Testing Gmb | Berer T.,Christian Doppler Laboratory | Burgholzer P.,Research Center for Non Destructive Testing Gmb | Burgholzer P.,Christian Doppler Laboratory
Ultrasonics | Year: 2013

Laser-generation of ultrasound is investigated in the coupled dynamical thermoelasticity in the presented paper. The coupled heat conduction and wave equations are solved using finite differences. It is shown that the application of staggered grids in combination with explicit integration of the wave equation facilitates the decoupling of the solution and enables the application of a combination of implicit and explicit numerical integration techniques. The presented solution is applied to model the generation of ultrasound by a laser source in isotropic and transversely isotropic materials. The influence of the coupling of the generalized thermoelasticity is investigated and it will be shown, that for ultra high frequency waves (i.e. 100 GHz) generated by laser pulses with duration in the picosecond range, the thermal feedback becomes considerable leading to a strong attenuation of the longitudinal bulk wave. Moreover, the coupling leads to dispersion influencing the wave velocities at low frequencies. The numerical simulations are compared to theoretical results available in the literature. Wave fields generated by a line focused laser source are presented by the numerical model for isotropic and for transversely isotropic materials. © 2012 Elsevier B.V. All rights reserved.


Berer T.,Christian Doppler Laboratory | Berer T.,Research Center for Non Destructive Testing Gmb | Hochreiner A.,Christian Doppler Laboratory | Zamiri S.,Christian Doppler Laboratory | And 2 more authors.
Optics Letters | Year: 2010

We report on remote and contactless photoacoustic imaging (PAI) for the inspection of solid materials using a twowave mixing interferometer. In this Letter, a semitransparent sample was excited with picosecond laser pulses. The local absorption of the electromagnetic radiation led to generation of broadband ultrasonic waves inside the sample. Ultrasonic waves arriving at the sample surface were detected utilizing a two-wave mixing interferometer. After data acquisition, the initial pressure distribution was reconstructed using a Fourier space synthetic aperture technique algorithm. We show the potential of PAI for the inspection of semitransparent solid materials. © 2010 Optical Society of America.


Hochreiner A.,Christian Doppler Laboratory | Berer T.,Christian Doppler Laboratory | Berer T.,Research Center for Non Destructive Testing Gmb | Grun H.,Research Center for Non Destructive Testing Gmb | And 3 more authors.
Journal of Biophotonics | Year: 2012

In this paper we report on remote three-dimensional photoacoustic imaging without the need for a coupling agent or other aids (e.g. detector foils) by utilizing a two-wave mixing interferometer (TWMI). In this technique the beams coming from sample and reference are brought to interfere in a Bi12SiO20 photorefractive crystal (PRC). Such a setup allows the measurement of ultrasonic displacements on rough sample surfaces. After data acquisition the initial pressure distribution is reconstructed by a Fourier domain synthetic aperture focusing technique (FSAFT). We present three-dimensional imaging of a hair ribbon phantom, on biological samples with embedded artificial blood vessels or pig bristles, and measurements on a human forearm in-vivo. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Veres I.A.,Research Center for Non Destructive Testing Gmb | Berer T.,Research Center for Non Destructive Testing Gmb | Berer T.,Christian Doppler Laboratory | Grunsteidl C.,Research Center for Non Destructive Testing Gmb | And 2 more authors.
Ultrasonics | Year: 2014

This article elaborates on the crossing points of the frequency-wavenumber branches for the symmetric and anti-symmetric Lamb modes in a homogeneous plate. It is shown both theoretically as well as experimentally that at these crossing points either the normal or the longitudinal components of modal displacement attain an extreme value, i.e. a maximum or it vanishes. This behavior is assessed herein using a method due to Mindlin, who showed that the dispersion curves for a plate with mixed boundary conditions - which are associated with uncoupled shear and dilatational modes - provide bounds to the spectral lines of the free plate. Therefore, a subset of the crossing points of the symmetric and antisymmetric Lamb modes for a free plate coincide with the crossing points for a plate with mixed boundary conditions. © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

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