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Zeitschriftenartikel

  • E. Schwab
  • S. Pogrebnoj
  • M. Freund
  • Florian Flossmann
  • S. Vogl
  • K.-H. Frommolt

Automated bat call classification using deep convolutional neural networks

In: Bioacoustics - The International Journal of Animal Sound and its Recording pg. 1-16.

  • 18.03.2022 (2022)

DOI: 10.1080/09524622.2022.2050816

Identification of bats is most practically done by exploiting the characteristic features of their echolocation calls. This usually involves expert knowledge, expensive equipment and time-consuming post processing of previously recorded calls. Automated solutions exist, but are usually not as accurate as human experts. We present an automated solution for the processing of bat calls and identification of bat species with extremely high classification accuracy that can be used during live recording or in an automated post-processing software. Our algorithm is the first application of a Deep Convolutional Neural Network to classify bat species based on sound spectrogram images of their echolocation calls. We tested several deep CNN architectures including a modified Google Inception and a ResNet50 architecture. The nets were trained on a very large call database consisting of images of snippets of call spectrograms. All our software was developed in the Python programming language and an executable of the software is available on request.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Patentschrift

  • W. Holzapfel
  • Florian Flossmann

Optische Positionsmessvorrichtung

Deutschland

  • (2011)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Patentschrift

  • W. Holzapfel
  • Florian Flossmann

Positionsmesseinrichtung und Verfahren zum Betrieb einer Positionsmesseinrichtung

Deutschland

  • (2010)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Patentschrift

  • W. Holzapfel
  • Florian Flossmann

Position measuring Device, and Operation Method of the same

Japan

  • (2010)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • K. OHolleran
  • Florian Flossmann
  • M. Dennis
  • M. Padgett

Methodology for imaging the 3D structure of singularities in scalar and vector optical fields

In: Journal of Optics vol. 11

  • (2009)

DOI: 10.1088/1464-4258/11/9/094020

  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • U. Schwarz
  • Florian Flossmann
  • M. Dennis

Topology of Generic Polarization Singularities in Birefringent Crystals

In: Topologica vol. 2

  • (2009)

DOI: 10.3731/topologica.2.006

An optical vortex incident on a birefringent crystal unfolds into a complex topological structure of lines of circular polarization (C–lines) and surfaces of linear polarization (L–surfaces). The incident beam splits into two or-thogonally polarized beams of ordinary and extraordinary polarization. Ex-traordinary refraction causes a shift of the extraordinarily polarized beam even under normal incidence. This shift together with the different phase velocities of both beams is the origin of an intriguing pattern of polarization singularities. We measure spatially resolved the full set of Stokes parameters after the beam passed the crystal to determine experimentally the spatial structure of the polarization singularities in three dimensions, two spatial directions (x, y) and one (Λ) corresponding to the relative phase retarda-tion between ordinary and extraordinary beam. The observed unfolding of the initial phase singularity is the most generic case of the generation of polarization singularities in uniaxial or biaxial birefringent crystals. It can be describe in a very general way in terms of Stokes parameters where the polarization singularities arise naturally from the zeros of the Stokes param-eters.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • J. Götte
  • K. OHolleran
  • D. Preece
  • Florian Flossmann
  • S. Franke-Arnold
  • S. Barnett
  • M. Padgett

Light beams with fractional orbital angular momentum and their vortexs tructure

In: Optics Express vol. 16 pg. 993-1006.

  • (2008)

DOI: 10.1364/OE.16.000993

Light emerging from a spiral phase plate with a non-integer phase step has a complicated vortex structure and is unstable on propagation. We generate light carrying fractional orbital angular momentum (OAM) not with a phase step but by a synthesis of Laguerre-Gaussian modes. By limiting the number of different Gouy phases in the superposition we produce a light beam which is well characterised in terms of its propagation. We believe that their structural stability makes these beams ideal for quantum information processes utilising fractional OAM states.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • Florian Flossmann
  • K. OHolleran
  • M. Padgett
  • M. Dennis

Polarization Singularities in 2D and 3D Speckle Fields

In: Physical Review Letters - moving physics forward vol. 100

  • (2008)
The 3D structure of randomly polarized light fields is exemplified by its polarization singularities: lines along which the polarization is purely circular (C lines) and surfaces on which the polarization is linear (L surfaces). We visualize these polarization singularities experimentally in vector laser speckle fields, and in numerical simulations of random wave superpositions. Our results confirm previous analytical predictions [M. R. Dennis, Opt. Commun. 213, 201 (2002)] regarding the statistical distribution of types of C points and relate their 2D properties to their 3D structure.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • K. OHolleran
  • Florian Flossmann
  • M. Padgett
  • M. Dennis

Fractality of light's darkness

In: Physical Review Letters - moving physics forward vol. 100

  • (2008)
Natural light fields are threaded by lines of darkness. For monochromatic light, the phenomenon is familiar in laser speckle, i.e., the black points that appear in the scattered light. These black points are optical vortices that extend as lines throughout the volume of the field. We establish by numerical simulations, supported by experiments, that these vortex lines have the fractal properties of a Brownian random walk. Approximately 73% of the lines percolate through the optical beam, the remainder forming closed loops. Our statistical results are similar to those of vortices in random discrete lattice models of cosmic strings, implying that the statistics of singularities in random optical fields exhibit universal behavior.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • Florian Flossmann
  • U. Schwarz
  • M. Maier
  • M. Dennis

Stokes parameters in the unfolding of an optical vortex through a birefringent crystal

In: Optics Express vol. 14 pg. 11402-11411.

  • (2006)
Following our earlier work (F. Flossmann et al., Phys. Rev. Lett. 95 253901 (2005)), we describe the fine polarization structure of a beam containing optical vortices propagating through a birefringent crystal, both experimentally and theoretically.We emphasize here the zero surfaces of the Stokes parameters in three-dimensional space, two transverse dimensions and the third corresponding to optical path length in the crystal. We find that the complicated network of polarization singularities reported earlier – lines of circular polarization (C lines) and surfaces of linear polarization (L surfaces) – can be understood naturally in terms of the zeros of the Stokes parameters.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Hochschulschrift

  • Florian Flossmann

Singularitäten von Phase und Polarisation des Lichts

Universität Regensburg Regensburg Naturwissenschaftliche Fakultät II - Physik

  • 2006 (2006)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • Florian Flossmann
  • U. Schwarz
  • M. Maier

Propagation dynamics of optical vortices in Laguerre-Gaussian beams

In: Optics Communications vol. 250 pg. 218-230.

  • (2005)

DOI: 10.1016/j.optcom.2005.02.032

We have calculated the propagation dynamics of an initial off-axis vortex with topological charge 1 in Laguerre–Gaussian background beams View the MathML source(LG10andLG70), which are examples of background beams with non-generic dislocation surfaces, on which the real and imaginary parts of the light field are zero. When initially a vortex with broad core (e.g., r-vortex) is embedded in the background beam, the dislocation surfaces are destroyed during propagation and two vortices with opposite charge are created per dislocation surface in planes perpendicular to the propagation direction. For a vortex with narrow core (e.g., point vortex) diffraction is important and leads to the birth of more than two vortices per dislocation surface. These results are also valid for other background beams with dislocation surfaces, e.g., Hermite–Gaussian and Ince–Gaussian beams. We investigated experimentally the spatial evolution of the intensity distribution of an initial off-axis vortex with narrow core and topological charge 1 in View the MathML sourceLG10andLG70 background beams. The experimental results are in good agreement with the calculated intensity distributions.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • Florian Flossmann
  • U. Schwarz
  • M. Maier

Optical Vortices in a Laguerre-Gaussian LG10 beam

In: Journal of Modern Optics vol. 52

  • (2005)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel

  • Florian Flossmann
  • U. Schwarz
  • M. Maier
  • M. Dennis

Polarization Singularities from Unfolding an Optical Vortex through a Birefringent Crystal

In: Physical Review Letters - moving physics forward vol. 95

  • (2005)

DOI: 10.1103/PhysRevLett.95.253901

Optical vortices (nodal lines and phase singularities) are the generic singularities of scalar optics but are unstable in vector optics. We investigate experimentally and theoretically the unfolding of a uniformly polarized optical vortex beam on propagation through a birefringent crystal and characterize the output field in terms of polarization singularities (C lines and points of circular polarization; L surfaces and lines of linear polarization). The field is described both in the 2-dimensional transverse plane, and in three dimensions, where the third is abstract, representing an optical path length propagated through the crystal. Many phenomena of singular optics, such as topological charge conservation and singularity reconnections, occur naturally in the description.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen