Bayerisches Laserzentrum GmbH

Erlangen, Germany

Bayerisches Laserzentrum GmbH

Erlangen, Germany
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Cvecek K.,Bayerisches Laserzentrum GmbH | Alexeev I.,Lehrstuhl fur Photonische Technologien | Miyamoto I.,Koshien | Schmidt M.,Bayerisches Laserzentrum GmbH
Physics Procedia | Year: 2010

Many applications require a joining of several glass components. However, the established processes for glass joining have certain disadvantages. By contrast, laser fusion welding by ultrafast lasers exhibits in principle excellent versatility, if the nonlinear interaction is localized enough so that plasma induced stresses can be tolerated and the temperature is high enough to melt the glass adjacent to the focal spot. However, defect generation during welding was observed for a broad range of welding conditions. This paper reports the observed defects and analyzes their origins.

Bechtold P.,Friedrich - Alexander - University, Erlangen - Nuremberg | Eiselen S.,Bayerisches Laserzentrum GmbH | Schmidt M.,Friedrich - Alexander - University, Erlangen - Nuremberg
Physics Procedia | Year: 2010

We evaluated the application-oriented suitability of electrostatic fields and laser-induced discharges to enhance both debris removal and ablation rate during ultrashort pulse laser drilling of copper. The electric field was varied to either induce or prevent laser-induced electric discharges. Results show that debris is expelled to a much greater distance by applying an electric field. If a laser-induced electric discharge is induced, greater heat-affected zone and greater amounts of debris are observed, pointing to an increased amount of ablated material. Results were independent on the applied voltage polarity, suggesting that there is no significant charge separation in the material plasma.

Schaefer L.,Bayerisches Laserzentrum GmbH | Schmidt M.,Bayerisches Laserzentrum GmbH
Physics Procedia | Year: 2010

In optical data transmission, adherence is the common method for joining optical components like fibres and lenses. Adhesive joints however have some disadvantages. The transmittable optical power is limited and the boundary layer causes undesired reflections. An alternative method for joining fibers with lenses is welding using CO 2 laser radiation. The irradiation pattern is designed in such a way, that the fibre is welded to the substrate around its whole circumference. Therefore a ring shaped beam is formed by a novel focusing device based on the Schwarzschild objective. The results of the welding experiments show significantly improved characterisitcs of the joint. © 2010 Published by Elsevier B.V.

Luegmair G.,University Hospital Erlangen Medical School | Kniesburges S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Zimmermann M.,Bayerisches Laserzentrum GmbH | Sutor A.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 2 more authors.
IEEE Transactions on Medical Imaging | Year: 2010

The ability to communicate with our voice can be regarded as the concatenation of the two processes phonation and modulation. These take place in the larynx and palatal and oral region, respectively. During phonation the audible primary voice signal is created by mutual reaction of vocal folds with the exhaled air stream of the lungs. The underlying interactions of masses, fluids and acoustics have yet to be identified and understood. One part of the primary signal's acoustical source are vortex induced vibrations, as e.g., created by the Coandeffect in the air stream. The development of these vorteces is determined by the shape and 3-D movements of the vocal folds in the larynx. Current clinical in vivo research methods for vocal folds do not deliver data of satisfactory quality for fundamental research, e.g., an endoscope is limited to 2-D image information. Based hereupon, a few improved methods have been presented, however delivering only selective 3-D information, either for a single point or a line. This stands in contrast to the 3-D motions of the entire vocal fold surface. More complex imaging methods, such as MRI, do not deliver information in real-time. Thus, it is necessary to develop an easily applicable, more improved examination method, which allows for 3-D data of the vocal folds surfaces to be obtained. We present a method to calibrate a 3-D reconstruction setup including a laser projection system and a high-speed camera. The setup is designed with miniaturization and an in vivo application in mind. The laser projection system generates a divergent grid of 196 laser dots by diffraction gratings. It is calibrated with a planar calibration target through planar homography. In general, the setup allows to reconstruct the topology of a surface at high frame rates (up to 4000 frames per second) and in uncontrollable environments, as e.g., given by the lighting situation (little to no ambient light) and varying texture (e.g., varying grade of reflection) in the human larynx. In particular, this system measures the 3-D vocal fold surface dynamics during phonation. Applied to synthetic data, the calibration is shown to be robust (error approximately 0.5 $\mu {\rm m}$) regarding noise and systematic errors. Experimental data gained with a linear $z$ -stage proved that the system reconstructs the 3-D coordinates of points with an error at approximately 15 $\mu {\rm m}$. The method was applied exemplarily to reconstruct porcine and artificial vocal folds' surfaces during phonation. Local differences such as asymmetry between left and right fold dynamics, as well as global parameters, such as opening and closing speed and maximum displacements, were identified and quantified. © 2010 IEEE.

Bechtold P.,Friedrich - Alexander - University, Erlangen - Nuremberg | Bechtold P.,Bayerisches Laserzentrum GmbH | Hohenstein R.,Friedrich - Alexander - University, Erlangen - Nuremberg | Hohenstein R.,Bayerisches Laserzentrum GmbH | And 2 more authors.
Optics Express | Year: 2013

Using acousto-optical deflectors at high deflection speeds via acoustical frequency chirping induces astigmatism, deforming the laser beam in an unfavorable way. Within the paper, we present a method to prevent this effect for an ultrashort pulsed laser beam via acoustical frequency jumps synchronized to the pulse-to-pulse pause. We also demonstrate and give a method to calculate beam shaping capability of acousto-optical deflectors via arbitrary spatial frequency developments during ultrashort laser pulse transit through the deflector. Cylinder-lens-free deflection at >2000 rad/s and beam shaping capability is demonstrated experimentally. In our experiments the switching time between two beam shapes is 1 μs. © 2013 Optical Society of America.

Urmoneit U.,Bayerisches Laserzentrum GmbH | Hotz A.,Bayerisches Laserzentrum GmbH | Frohlich T.,LASERVISION GmbH and Co. KG | Krauss H.-J.,Bayerisches Laserzentrum GmbH
Physics Procedia | Year: 2014

Beside the total laser power, the laser beam diameter is a significant factor for the resistance of laser protection filters to laser radiation. In this paper a study of the resistance of laser protection filters to laser radiation in dependence of the laser beam diameter is given. For the investigation of this effect an experimental setup is realized, which detects laser radiation near the MPE value (ref. 1) (Maximum Permissible Exposure; level of laser radiation to which, under normal circumstances, persons may be exposed without suffering adverse effects) behind the filter glasses, which is taken as a criteria for the failure of laser protection filters. This failure defines the laser resistance time of the protection filter under the given laser parameters (laser power and laser beam diameter). The experiments involve a series of irradiations from a cw (continuous wave) Nd:YAG laser (wavelength 1064 nm) with the variation of laser power, laser beam diameter and with different material thicknesses. The dependency of the laser resistance time follows a power function of the laser beam diameter. It is shown that by performing only a few dedicated laser resistance tests for a specific type of laser protection filter, it is possible to calculate the laser resistance time for different laser beam diameters occurring in practical lab situations. © 2014 The Authors. Published by Elsevier B.V.

Amend P.,Bayerisches Laserzentrum GmbH | Frick T.,Bayerisches Laserzentrum GmbH | Frick T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schmidt M.,Bayerisches Laserzentrum GmbH | Schmidt M.,Friedrich - Alexander - University, Erlangen - Nuremberg
Physics Procedia | Year: 2011

This paper presents experimental results of joining carbon fiber (CF) reinforced thermosetting composites (TSC) to thermoplastics (TP) by means of laser-based hot-melt bonding. First of all the influence of different laser systems (λ = 355 nm and λ = 1064 nm) on the ablation of the thermosetting matrix (epoxy) with preferably little damage to the CF is analyzed by means of microscopy. Afterwards the laser-based joining process of TSC and TP is carried out. Finally the joining connections are characterized by tensile shear tests. Thereby the influence of the surface treatment and the used thermoplastic (PC/ABS, PA66 or PA66-GF30) on the tensile shear strength is investigated. © 2011 Published by Elsevier Ltd.

Leitz K.-H.,Friedrich - Alexander - University, Erlangen - Nuremberg | Redlingshoer B.,Friedrich - Alexander - University, Erlangen - Nuremberg | Reg Y.,Bayerisches Laserzentrum GmbH | Otto A.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 2 more authors.
Physics Procedia | Year: 2011

In laser microstructuring there is a general conflict between precision and efficiency. Short pulsed micro- and nanosecond systems generally allow high ablation rates. Yet, thermal damage of the workpiece cannot be avoided completely. Ultrafast picoand femtosecond systems allow a higher precision, yet at lower ablation efficiency. This on the one hand can be attributed to the generally lower medium laser power of the ultrafast laser systems, on the other hand to the changed ablation mechanisms. In this contribution a comparative study of the ablation of metal with micro-, nano-, pico- and femtosecond laser pulses shall be presented. © 2011 Published by Elsevier Ltd.

Amend P.,Bayerisches Laserzentrum GmbH | Pfindel S.,Bayerisches Laserzentrum GmbH | Schmidt M.,Bayerisches Laserzentrum GmbH | Schmidt M.,Friedrich - Alexander - University, Erlangen - Nuremberg
Physics Procedia | Year: 2013

In recent years, joining of plastics and metals for lightweight constructions has become more and more important for industrial applications. This paper presents a novel approach for thermal joining of thermoplastic metal hybrids by means of a combination of mono- and polychromatic radiation. During this work, hybrid joints of aluminum (EN AW-5182) and technical thermoplastics (PC, PA6, PA66-GF30) are studied. Thereby experiments for transmission and heat-conduction joining are performed. Besides, the influences of laser structuring of the metal surface on the joint connections are investigated. Additionally, climate tests according to BMW PR 308.2 from -30°C to 90°C and from -40°C to 120°C are performed to analyze the long-term durability of the hybrid joint connections. © 2013 The Authors.

Kanawade R.,Friedrich - Alexander - University, Erlangen - Nuremberg | Mehari F.,Friedrich - Alexander - University, Erlangen - Nuremberg | Knipfer C.,Friedrich - Alexander - University, Erlangen - Nuremberg | Rohde M.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 4 more authors.
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2013

This study focuses on tissue differentiation using 'Laser Induced Breakdown Spectroscopy' (LIBS) by monitoring the plasma plume created during laser surgery processes. This technique is aimed at controlling a laser surgery feedback system in real time. An Excimer laser (Ar-F 193 nm) was used for the ablation of tissue samples. Fat, muscle, nerve and skin tissue samples of bisected ex-vivo pig heads were prepared as test objects for the ablation procedure. A single fiber was used to collect emissions and deliver them to a spectrometer. The obtained LIBS spectra in the measured emissions were analyzed to determine each tissue type according to their chemical composition. The elements found in the samples and their emission spectra were in agreement with those described in literature. The collected LIBS spectra were analyzed to differentiate the tissues using statistical data analysis: Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Receiver Operating Characteristics (ROC). The obtained preliminary results suggest a successful differentiation of the target tissues with high sensitivity and specificity. The main goal of this study was to qualitatively identify tissue types during laser ablation, which will provide a real time feedback mechanism for clinical Laser surgery applications to significantly improve the accuracy and safety of laser surgery procedures. © 2013 Elsevier B.V. All rights reserved.

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