Influence of atmospheric turbulence on imaging quality of electro-optical sensors in different climates

Weiss-Wrana, Karin

doi:10.1117/12.511801

Cited by 12 publications

(3 citation statements)

References 4 publications

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“…As an example for very different meteorological conditions one winter month, January (left hand graph) and one summer month, July (right hand graph) were selected. The diurnal runs of C n 2 differ significantly from the ones derived from our measurements over land in arid climate (Negev, Israel) and moderate climate (Germany, Central Europe), for details see 8,9 . Over sea, in summer the characteristic maximum at midday can hardly be observed in general.…”

Section: Analysis Of C N 2 Measurements Over Seamentioning

confidence: 92%

Turbulence statistics in littoral area

Weiss-Wrana

2006

SPIE Proceedings

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FGAN-FOM carried out a long-term experiment to measure C n 2 over sea in littoral area in moderate climate, Central Europe. A Boundary Layer Scintillometer was installed along a 1.7 km path crossing a bay of the Baltic Sea (Eckernfoerder Bucht) at a height of 4.7 m above water level. Meteorological parameters were measured simultaneously. One of the main parameters, which effects C n 2 , is the temperature difference between air and ground. In general a larger temperature difference causes stronger turbulence. Over sea, the air-sea temperature difference, ASTD, is generally smaller than the air-ground temperature difference over land, which implicates smaller C n 2 values. Turbulence over sea differs significantly from turbulence over land. The diurnal run of C n 2 does not show generally the characteristic maximum at midday, C n 2 values measured during night are not generally smaller than those measured at midday, and C n 2 values measured in the daytime in summer are not generally larger than those measured in winter season. Since C n 2 usually changes with environmental conditions, its influence on the effectiveness of electro-optical systems can normally only be expressed in a statistical way. We worked out a statistical database for atmospheric turbulence over sea accordingly to our turbulence statistics over land. The cumulative frequency of occurrence was calculated for a period of one month for a two-hour time interval during daytime and during night. Even though the meteorological conditions in Central Europe show a large variability, the cumulative frequencies of occurrence derived for 2003 and 2004 indicate the same seasonal devolution. We applied the LWKD model of the Defence Research and Development, DRDC Valcartier, Canada, to calculate C n 2 as a function of ASTD for the measured meteorological parameters. The measurements indicate larger C n 2 values than the calculations. Keywords:Atmospheric turbulence over sea, structure constant of refractive index fluctuations C n 2 , air-sea temperature difference ASTD, littoral area, LWKD Marine Boundary Model.

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Section: Analysis Of C N 2 Measurements Over Seamentioning

confidence: 92%

Turbulence statistics in littoral area

Weiss-Wrana

2006

SPIE Proceedings

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“…For other parametric value adequate models, e.g. described as strong turbulence models [8] or reference measurements in from other climates [16], are to be applied. Not all possible cases (e.g.…”

Section: Figure 4: Visualization Of the Theoretic Models In Image Unimentioning

confidence: 99%

Investigation of atmospheric turbulence effects on extended objects in high-speed image sequences applying automatic image analysis

Mauer

2004

SPIE Proceedings

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A main goal of this investigation is to extract local qualitative measurements of elementary turbulence effects on extended image objects from fast image sequences. These local measurements are a prerequisite for the relationship between the local turbulence level versus the degradation of specialized automatic processes and allow the selection of a specific image treatment (e.g. adequate object model) or the tuning (e.g. adaptive turbulence filtering) of an automatic image analysis process (e.g. object tracking). Results of the developed analysis methods on different sequences showing diverse image contents taken in a well known environment (desert test site, indoor experiments, simulation) under various conditions will be presented and discussed with respect to different applications (e.g. local C N 2 -estimation).

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“…In addition, studies have shown that active laser imaging systems can obtain images of non-line-of-sight targets hidden around corners 8 . The imaging quality is mainly affected by the backscattering 9 , attenuation and turbulence caused by the scattering medium 10 . Meanwhile, more backscattered radiation can be eliminated by adjusting the laser pulse frequency and shutter 11 .…”

Section: Introductionmentioning

confidence: 99%

Accurate performance prediction and full-chain quantitative characterization of active imaging quality degradation

Zhang

Yuan

Wang

et al. 2023

Conference on Infrared, Millimeter, Terahertz Waves and Applications (IMT2022)

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The active imaging system has shown great potential in harsh environmental conditions, but the imaging quality of the system under certain conditions is difficult to be assessed. Therefore, we performed accurate physical modeling and imaging simulations of the active imaging system. In this paper, we analyze the signal transmission and degradation mechanism of active imaging by considering the global radiation and scattering elements of the imaging profile. Then, a full-chain imaging pixel equation is established to characterize the information conversion process, and global radiation elements such as backscattering, ambient radiation, and atmospheric turbulence are coupled into the imaging conversion model for higher accuracy. Furthermore, various design parameters and environmental parameters are coupled with the imaging model and a 3D digital prototype of the active laser imaging system is completed. The degradation of imaging contrast and range caused by visibility, atmospheric turbulence, aerosol type, and solar zenith angle is quantitatively evaluated. This research can provide useful support for the simulation analysis and performance prediction of active imaging systems.

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Influence of atmospheric turbulence on imaging quality of electro-optical sensors in different climates

Cited by 12 publications

References 4 publications

Turbulence statistics in littoral area

Turbulence statistics in littoral area

Investigation of atmospheric turbulence effects on extended objects in high-speed image sequences applying automatic image analysis

Accurate performance prediction and full-chain quantitative characterization of active imaging quality degradation

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