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Erlangen, Germany

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. Source

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. Source

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. Source

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. Source

Bitterli R.,Photonics Optics Tech | Scharf T.,Photonics Optics Tech | Herzig H.-P.,Photonics Optics Tech | Noell W.,Ecole Polytechnique Federale de Lausanne | And 7 more authors.
Optics Express | Year: 2010

We present a new approach of beam homogenizing elements based on a statistical array of concave cylindrical microlens arrays. Those elements are used to diffuse light in only one direction and can be employed together with fly's eye condensers to generate a uniform flat top line for high power coherent light sources. Conception, fabrication and characterization for such ID diffusers are presented in this paper. © 2010 Optical Society of America. Source

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