Mr. Frédéric Schwenger Profile

Frédéric Schwenger

at Fraunhofer IOSB

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Publications (10)

Proceedings Article | 23 April 2020 Presentation + Paper

Simulation of laser speckle patterns generated by random rough surfaces

Frédéric Schwenger, Katrin Braesicke

Proceedings Volume 11406, 1140609 (2020) https://doi.org/10.1117/12.2557235

KEYWORDS: Laser beam propagation, Speckle pattern, Optical simulations, Reflection, Fourier transforms, Speckle, Fractal analysis, Laser sources, Surface roughness

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Proceedings Article | 5 October 2017 Paper

Simulation of an oil film at the sea surface and its radiometric properties in the SWIR

Frédéric Schwenger, Alexander M. Van Eijk

Proceedings Volume 10432, 104320D (2017) https://doi.org/10.1117/12.2278282

KEYWORDS: Computer simulations, Short wave infrared radiation, Bidirectional reflectance transmission function, Surface roughness, Modulation, Reflection, Ocean optics, Radio optics, 3D modeling, Capillaries

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Proceedings Article | 3 May 2016 Paper

Simulation of whitecaps and their radiometric properties in the SWIR

Frédéric Schwenger, Endre Repasi

Proceedings Volume 9820, 982014 (2016) https://doi.org/10.1117/12.2223025

KEYWORDS: Computer simulations, Short wave infrared radiation, Bidirectional reflectance transmission function, Light sources, Optical simulations, Light, Reflection, 3D modeling, Cameras, Statistical modeling, Reflectivity, Sensors, Receivers

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A 3D simulation of the dynamic sea surface populated with whitecaps is presented. The simulation considers the dynamic evolution of whitecaps depending on wind speed and fetch. It is suitable for imaging simulations of maritime scenarios. The calculation of whitecap radiance is done in the SWIR spectral band by considering wave hiding and shadowing, especially occurring at low viewing angles. Our computer simulation combines the 3D simulation of a maritime scene (open sea/clear sky) considering whitecaps with the simulation of light from a light source (e.g. laser light) reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The whitecap generation is deduced from the vertical acceleration of the sea surface, i.e. from the second moment of the wave power density spectrum. To predict the view of a camera, the sea surface radiance must be calculated for the specific waveband with the emitted sea surface radiance and the specularly reflected sky radiance as components. The radiances of light specularly reflected at the windroughened sea surface without whitecaps are modeled by considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). A specific BRDF of whitecaps is used by taking into account their shadowing function. The simulation model is suitable for the pre-calculation of the reflected radiance of a light source for near horizontal incident angles where slope-shadowing of waves has to be considered. The whitecap coverage is determined from the simulated image sequences for different wind speeds and is compared with whitecap coverage functions from literature. A SWIR-image of the water surface of a lake populated with whitecaps is compared with the corresponding simulated image. Additionally, the impact of whitecaps on the radiation balance for a bistatic configuration of light source and receiver is calculated for different wind speeds.

Proceedings Article | 12 May 2015 Paper

Simulation of a polarized laser beam reflected at the sea surface: modeling and validation

Frédéric Schwenger

Proceedings Volume 9452, 94520A (2015) https://doi.org/10.1117/12.2176970

KEYWORDS: Optical simulations, Cameras, Reflection, Laser sources, Polarizers, Bidirectional reflectance transmission function, Polarization, Reflectivity, Computer simulations, Short wave infrared radiation

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A 3-D simulation of the polarization-dependent reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation considers polarized or unpolarized laser sources and calculates the polarization states upon reflection at the sea surface. It is suitable for the radiance calculation of the scene in different spectral wavebands (e.g. near-infrared, SWIR, etc.) not including the camera degradations. The simulation also considers a bistatic configuration of laser source and receiver as well as different atmospheric conditions. In the SWIR, the detected total power of reflected laser light is compared with data collected in a field trial. Our computer simulation combines the 3-D simulation of a maritime scene (open sea/clear sky) with the simulation of polarized or unpolarized laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the input of a camera equipped with a linear polarizer, the polarized sea surface radiance must be calculated for the specific waveband. The s- and p-polarization states are calculated for the emitted sea surface radiance and the specularly reflected sky radiance to determine the total polarized sea surface radiance of each component. The states of polarization and the radiance of laser light specularly reflected at the wind-roughened sea surface are calculated by considering the s- and p- components of the electric field of laser light with respect to the specular plane of incidence. This is done by using the formalism of their coherence matrices according to E. Wolf [1]. Additionally, an analytical statistical sea surface BRDF (bidirectional reflectance distribution function) is considered for the reflection of laser light radiances. Validation of the simulation results is required to ensure model credibility and applicability to maritime laser applications. For validation purposes, field measurement data (images and meteorological data) was analyzed. An infrared laser, with or without a mounted polarizer, produced laser beam reflection at the water surface and images were recorded by a camera equipped with a polarizer with horizontal or vertical alignment. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam and different alignment for the laser polarizers (vertical/horizontal/without) and the camera (vertical/horizontal).

Proceedings Article | 5 June 2013 Paper

Simulation of laser beam reflection at the sea surface modeling and validation

Frédéric Schwenger, Endre Repasi

Proceedings Volume 8706, 87060S (2013) https://doi.org/10.1117/12.2015767

KEYWORDS: Optical simulations, Cameras, Reflection, Laser sources, Computer simulations, Video, Bidirectional reflectance transmission function, Receivers, Atmospheric modeling, Sensors

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Proceedings Article | 10 May 2011 Paper

Simulation of laser beam reflection at the sea surface

Frédéric Schwenger, Endre Repasi

Proceedings Volume 8014, 80140R (2011) https://doi.org/10.1117/12.883387

KEYWORDS: Sensors, Laser sources, Optical simulations, Short wave infrared radiation, Reflection, Bidirectional reflectance transmission function, Receivers, Pulsed laser operation, Computer simulations, Atmospheric modeling

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Proceedings Article | 22 April 2009 Paper

Validation of the thermal code of RadTherm-IR, IR-Workbench, and F-TOM

Frédéric Schwenger, Peter Grossmann, Alain Malaplate

Proceedings Volume 7300, 73000J (2009) https://doi.org/10.1117/12.817727

KEYWORDS: Temperature metrology, Sensors, Infrared sensors, Image sensors, Thermal modeling, Thermography, Solar radiation models, Cameras, Clouds, Data modeling

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Proceedings Article | 30 April 2007 Paper

CUBI: a test body for thermal object model validation

Alain Malaplate, Peter Grossmann, Frédéric Schwenger

Proceedings Volume 6543, 654305 (2007) https://doi.org/10.1117/12.724825

KEYWORDS: Data modeling, Temperature metrology, Thermal modeling, Thermography, Infrared signatures, Cameras, Sun, Solar radiation models, Infrared radiation, Infrared imaging

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Proceedings Article | 4 May 2006 Paper

Sea surface simulation in the infrared modeling and validation

Frédéric Schwenger, Endre Repasi

Proceedings Volume 6239, 62390J (2006) https://doi.org/10.1117/12.664838

KEYWORDS: Clouds, Thermography, Sensors, Long wavelength infrared, Mid-IR, Sun, Infrared imaging, Cameras, Computer simulations, Thermal modeling

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Proceedings Article | 5 September 2003 Paper

Sea surface simulation for testing of multiband imaging sensors

Frederic Schwenger, Endre Repasi

Proceedings Volume 5075, (2003) https://doi.org/10.1117/12.488472

KEYWORDS: Sensors, Visible radiation, Computer simulations, Water, Polarization, Reflectivity, Dielectric polarization, Infrared imaging, Sun, Reflection

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Showing 5 of 10 publications

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