@article {kiefhaber2014a,
	title = {High-speed imaging of short wind waves by shape from refraction},
	journal = {J. Europ. Opt. Soc. Rap. Public.},
	volume = {9},
	year = {2014},
	pages = {14015},
	doi = {10.2971/jeos.2014.14015},
	author = {Daniel Kiefhaber and Svenja Reith and Roland Rocholz and Bernd J{\"a}hne}
}
@conference {kiefhaber2013,
	title = {Optical measurement of surface ocean waves},
	booktitle = {3rd EOS Topical Meeting on Blue Photonics --- Optics in the Sea},
	year = {2013},
	note = {best student poster award},
	doi = {10.5281/zenodo.12334},
	author = {Daniel Kiefhaber and Roland Rocholz and Paulus Salomon Bauer and Bernd J{\"a}hne}
}
@unpublished {rocholz2012,
	title = {High speed and high resolution wave imaging to investigate the initial generation of wind waves at very small fetch},
	year = {2012},
	note = {WISE (Waves In Shallow Environments) 2012, 19th International Conference, Barcelona, Spain},
	url = {http://hci.iwr.uni-heidelberg.de/publications/dip/MISC/WISE_2012_rrocholz/2012_WISE_rrocholz_noVideos.pdf},
	author = {Roland Rocholz and Patrick Fahle and Bernd J{\"a}hne}
}
@conference {kraeuter2012,
	title = {Partitioning of the Trasfer Resistance between Air and Water},
	booktitle = {SOLAS Open Science Conference, Washington State, USA},
	year = {2012},
	doi = {10.5281/zenodo.12328},
	author = {Christine Kr{\"a}uter and Kerstin E. Richter and Evridiki Mesarchaki and Roland Rocholz and Jonathan Williams and Bernd J{\"a}hne}
}
@conference {richter2012,
	title = {The Schmidt Number Dependency of Air-Sea Gas Exchange with Varying Surfactant Coverage},
	booktitle = {SOLAS Open Science Conference, Washington State, USA},
	year = {2012},
	author = {Kerstin E. Richter and Roland Rocholz and Bernd J{\"a}hne}
}
@conference {kiefhaber2012,
	title = {Water Surface Topography Measurements with the Reflective Stereo Slope Gauge},
	booktitle = {AGU Ocean Science Meeting 2012, Salt Lake City},
	year = {2012},
	doi = {10.5281/zenodo.12333},
	author = {Daniel Kiefhaber and Julia Schaper and Roland Rocholz and Christopher J. Zappa and William E. Asher and Jessup, A.T. and Bernd J{\"a}hne}
}
@conference {rocholz2011a,
	title = {Combined visualization of wind waves and water surface temperature},
	booktitle = {Gas Transfer at Water Surfaces 2010},
	year = {2011},
	pages = {496--506},
	doi = {10.5281/zenodo.14957},
	url = {http://hdl.handle.net/2433/156156},
	author = {Roland Rocholz and Sven Wanner and Uwe Schimpf and Bernd J{\"a}hne},
	editor = {S. Komori and W. R. McGilles and R. Kurose}
}
@conference {mischler2011,
	title = {Experimental setup for the investigation of bubble mediated gas exchange},
	booktitle = {Gas Transfer at Water Surfaces 2010},
	year = {2011},
	pages = {238--248},
	doi = {10.5281/zenodo.14953},
	url = {http://hdl.handle.net/2433/156156},
	author = {Wolfgang Mischler and Roland Rocholz and Bernd J{\"a}hne},
	editor = {S. Komori and W. R. McGilles and R. Kurose}
}
@conference {wanner_11_framework,
	title = {A Framework for Interactive Visualization and Classification of Dynamical Processes at the Water Surface},
	booktitle = {16th International Workshop on Vision, Modelling and Visualization},
	year = {2011},
	note = {1},
	pages = {199-206},
	publisher = {Eurographics Association, Germany},
	organization = {Eurographics Association, Germany},
	doi = {10.2312/PE/VMV/VMV11/199-206},
	author = {Sven Wanner and Christoph Sommer and Roland Rocholz and Fred A. Hamprecht and Bernd J{\"a}hne},
	editor = {Eisert, P. and Joachim Hornegger and Konrad Polthier}
}
@conference {wanner2011,
	title = {A framework for interactive visualization and classification of dynamical processes at the water surface},
	booktitle = {16th International Workshop on Vision, Modelling and Visualization},
	year = {2011},
	pages = {199--206},
	publisher = {Eurographics Association, Germany},
	organization = {Eurographics Association, Germany},
	doi = {10.2312/PE/VMV/VMV11/199-206},
	author = {Sven Wanner and Christoph Sommer and Roland Rocholz and Jung, M. and Fred A. Hamprecht and Bernd J{\"a}hne},
	editor = {Peter Eisert and Joachim Hornegger and Konrad Polthier}
}
@conference {kiefhaber2011b,
	title = {Improved optical instrument for the measurement of water wave statistics in the field},
	booktitle = {Gas Transfer at Water Surfaces 2010},
	year = {2011},
	pages = {524--534},
	doi = {10.5281/zenodo.14958},
	url = {http://hdl.handle.net/2433/156156},
	author = {Daniel Kiefhaber and Roland Rocholz and Bernd J{\"a}hne},
	editor = {S. Komori and W. R. McGilles and R. Kurose}
}
@conference {kiefhaber2011a,
	title = {Mean square slope measurements in the field with the reflective stereo slope gauge},
	booktitle = {EGU General Assembly, Vienna},
	year = {2011},
	abstract = {An optical instrument for the measurement of surface ocean small-scale wave statistics has been developed. This reflective stereo slope gauge (RSSG) is capable of simultaneous measurements of height and slope statistics of the water surface in the field. The instrument is a significant technical improvement of the early work by Waas and J{\"a}hne (1992) and comprises a stereo camera setup, artificial light sources and a wind following system. The measurement principle is similar to Cox \& Munk{\textquoteright}s derivation of slope statistics from photographs of Sun glitter (Cox and Munk, 1954). However, the RSSG uses artificial light sources instead of relying on natural illumination and can thus be used independent of daytime or cloud cover. The probability distribution of the occurrence of specular reflections at given image coordinates can be related to the probability distribution of the surface slope, if the position of the instrument relative to the water surface is known. The slope probability distribution is measured for small slopes up to 0.15. From this partial probability distribution, estimates of the mean square slope (mss) and other statistical parameters can be extracted. The distance from of the instrument to the water surface is obtained from stereo triangulation, while an inclination sensor measures its tilt. Stereo triangulation at the specular reflecting water surface requires the use of two light sources in complementary positions to ensure that both cameras detect reflections coming from the same surface patches. Furthermore, to guarantee that each camera can only sees the corresponding light source, the stereo images are acquired sequentially and the LED light sources are pulsed. The water surface does not change significantly in between the image acquisitions, since the exposure time (and thus the minimum delay of the second image acquisition) is limited to 0.2 ms. The instrument can measure the along-wind and cross-wind mean square slope components, even under varying wind conditions. A wind following system was implemented that is able to rotate the stereo base to keep it aligned in an along-wind or cross-wind direction. Even though the instrument cannot record slope time series and only makes statistic measurements, it has significant advantages over other techniques that are commonly used. Measurements are non-invasive (no instrument parts suspended into or submersed in water) and mostly independent of natural illumination (light source peak wavelength is 940 nm, IR filters suppress skylight, only direct sun glitter may cause complications), not influenced by upwelling light (strong absorption of light at 940 nm by water) and have a spatial resolution that allows the measurement of slope statistics also for capillary waves. At the same time, the (gravity) wave amplitudes can be inferred from the stereo information. The RSSG was characterized and tested in the laboratory and deployed to the Baltic Sea in July and September 2010 to perform local wave statistics measurements at the footprint of heat exchange experiments with the active controlled flux technique (Schimpf et al., 2010). First results from these experiments that demonstrate the capability of the RSSG to measure wave slope statistics in a variety of conditions are presented.},
	doi = {10.5281/zenodo.12331},
	author = {Daniel Kiefhaber and Roland Rocholz and Julia Schaper and G{\"u}nther Balschbach and Bernd J{\"a}hne}
}
@conference {kiefhaber2011,
	title = {Measurement of ocean wave statistics with the reflective stereo slope gauge},
	booktitle = {DPG Fr{\"u}hjahrstagung Dresden, Fachverband Umweltphysik},
	year = {2011},
	abstract = {An optical instrument for the measurement of surface ocean small-scale wave statistics has been developed. This reflective stereo slope gauge (RSSG) is a significant technical improvement of the early work by Waas and J{\"a}hne (1992) and capable of simultaneous measurements of height and slope statistics of the water surface in the field. It comprises a stereo camera setup to measure wave heights by stereo triangulation. The slope measurement is based on Cox \& Munk{\textquoteright}s derivation of slope statistics from photographs of sun glitter (1954) but uses artificial light sources to be independent of natural illumination. The probability distribution of the occurrence of specular reflections in the images can be related to the probability distribution of the surface slope. Although the instrument only makes statistical measurements, it has significant advantages over other common techniques. Measurements are non-invasive (no instrument parts suspended into or submersed in water) and mostly independent of natural illumination (IR light source with},
	url = {http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/up/session/1/contribution/30},
	author = {Daniel Kiefhaber and Roland Rocholz and G{\"u}nther Balschbach and Julia Schaper and Bernd J{\"a}hne}
}
@techreport {mischler2011a,
	title = {Vereinfachung der Massenbilanz im Blasentank f{\"u}r luftseitige Messung},
	year = {2011},
	institution = {Institut f{\"u}r Umweltphysik},
	author = {Wolfgang Mischler and Roland Rocholz and Weissbach, T.}
}
@techreport {rocholz2010b,
	title = {Calibration of the 2010-CISG Setup at the Aeolotron},
	year = {2010},
	institution = {Institute of Environmental Physics, University of Heidelberg},
	author = {Roland Rocholz}
}
@conference {rocholz2010,
	title = {Spatio-temporal measurements of short wind water waves},
	booktitle = {EGU General Assembly 2010, Symposium AS2.2},
	year = {2010},
	pages = {EGU2010-5509},
	author = {Roland Rocholz and Bernd J{\"a}hne}
}
@conference {kiefhaber2009,
	title = {Instrument development for combined height/slope/curvature statistics measurements of wind water waves in the field},
	booktitle = {Poster abstracts SOLAS Open Science Conference, Barcelona, 16--19 Sep. 2009},
	year = {2009},
	abstract = {An optical method for the measurement of slope statistics of capillary and short gravity wind waves on the ocean is currently under development. Specular reflections from infrared LED light sources are observed on the water surface with a stereo camera setup. The principle is similar to Cox \& Munk{\textquoteright}s derivation of slope statistics from photographs of the Sun{\textquoteright}s glitter. Fractional area of the speckles in the image is related to the local slope probability distribution, speckle size and brightness is correlated with surface curvature, and the local water height can be inferred from parallax in the stereo images. The instrument measures slope statistics locally, making it a beneficial appendix to air-sea interaction measurements. It is scheduled to accompany heat transfer experiments in the Baltic Sea in phase II of the SOPRAN project.},
	author = {Daniel Kiefhaber and Roland Rocholz and Bernd J{\"a}hne}
}
@conference {mischler2009,
	title = {Optical method for measuring size-distribution and lifetime of bubbles},
	booktitle = {Poster abstracts SOLAS Open Science Conference, Barcelona, 16--19 Sep. 2009},
	year = {2009},
	abstract = {A high resolution imaging method for measuring the size distribution of bubbles entrained by water jets between 10-1000 um in diameter is presented. The bubble clouds are similar to those produced by breaking water waves. The goal of these measurements is the validation of models for bubble mediated gas transfer. A Depth from Focus technique is used to determine the 3D position and the size of the bubbles at the same time. This yields the size-distribution and its dependence on depth. Additionally the velocity of the bubbles is estimated using repeatedly exposed images. To evaluate the lifetime of bubbles a high-speed camera is used to count the bubbles crossing the surface. The measuring principle, image analysis and first results are presented.},
	author = {Wolfgang Mischler and Roland Rocholz and Bernd J{\"a}hne}
}
@phdthesis {rocholz2008,
	title = {Spatiotemporal Measurement of Short Wind-Driven Water Waves},
	year = {2008},
	publisher = {Institut f{\"u}r Umweltphysik, Fakult{\"a}t f{\"u}r Physik und Astronomie, Univ.\ Heidelberg},
	abstract = {Spatio-temporal measurements of wind-driven short-gravity capillary waves are reported for a wide range of experimental conditions, including wind, rain and surface slicks. The experiments were conducted in a linear wind wave flume and for the water surface elevation eta(x,y,t) both components of the slope field s = grad eta were measured optically. For this the color imaging slope gauge (CISG) was realized, comprising a range of wavenumbers k = sqrt(kx^2 + ky^2) from 60 to 4500 rad/m. The instrument was improved to achieve a sampling rate of 312.5 Hz, which now allows for the computation of 3D wavenumber-frequency spectra S(kx, ky, omega). Using a new calibration method it was possible to correct for the intrinsic nonlinearities of the instrument in the slope range up to {\textpm}1. In addition, the Modulation Transfer Function (MTF) was measured and employed for the contrast restoration of the data. The results are generally consistent with former measurements. But, the shape of the saturation spectra in the vicinity of k > 1000 rad/m stands in contradiction to former investigations where a sharp spectral cutoff (propto k^(-2) or k^(-3)) is commonly reported. The new MTF corrected spectra show just a gentle decrease (between k^(-0.5) and k^(-1)) for k >1000 rad/m, which has implications for the modeling of the energy fluxes in the wave field. Concerning the dispersion relation, a first approach for a quantitative evaluation of the wavenumber-frequency spectrum is shown. This includes estimates of the surface tension and the Doppler shift due to the surface shear flow and the wave-wave modulations. The wave measurements were accompanied by synchronized and spatially coinciding measurements of the surface temperature by means of infrared imagery. The temperature data is mapped onto an animated graphical model of the reconstructed surface elevation using a new interactive visualization tool. This allows for an investigation of intermittent small scale processes that are influencing the transfer of heat and gases at the air-water interface, such as microscale wave breaking, small scale Langmuir circulations, and the impact of rain drops.},
	url = {http://www.ub.uni-heidelberg.de/archiv/8897},
	author = {Roland Rocholz}
}
@techreport {rocholz2007,
	title = {Kalibrierung der Color Imaging Slope Gauge \& Auswertung der Wellenmessungen},
	year = {2007},
	institution = {Institut f{\"u}r Umweltphysik, Universit{\"a}t Heidelberg},
	author = {Roland Rocholz}
}
@conference {rocholz2006,
	title = {Imaging System for combined slope/height measurements of short wind waves : ISHG},
	booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Spring Conference, Heidelberg, 15.-17.03.2006},
	year = {2006},
	publisher = {Deutsche Physikalische Gesellschaft},
	organization = {Deutsche Physikalische Gesellschaft},
	url = {http://www.dpg-verhandlungen.de/2006/heidelberg/up.html},
	author = {Roland Rocholz and Bernd J{\"a}hne}
}
@mastersthesis {rocholz2005,
	title = {Bildgebendes System zur simultanen Neigungs- und H{\"o}henmessung an kleinskaligen Wind-Wasserwellen},
	year = {2005},
	school = {University of Heidelberg},
	author = {Roland Rocholz}
}
@article {jaehne2005a,
	title = {Combined optical slope/height measurements of short wind waves: principles and calibration},
	journal = {Meas. Sci. Technol.},
	volume = {16},
	number = {10},
	year = {2005},
	pages = {1937--1944},
	abstract = {A novel short wave imaging technique is described. For the first time, it is capable of measuring the wave height and wave slope simultaneously with unprecedented accuracy. A telecentric optical system is used to image the waves so that the image magnification does not change with the wave height and the slope calibration is much less dependent on the position of the image. A telecentric illumination system contains an area-extended LED light source that is placed in the focal plane of a second lens below the water channel. In this way, the wave slope can be coded by the position-dependent intensity of the light source. LEDs with two different wavelengths in the red and near infrared part of the spectrum are used. Because the water column absorbs the two wavelengths differently, the difference in the observed intensities gives the wave height. The paper details the principle of the technique and the calibration procedures.},
	issn = {0957-0233},
	doi = {10.1088/0957-0233/16/10/008},
	author = {Bernd J{\"a}hne and Schmidt, M. and Roland Rocholz}
}
