Comparison of modeled atmosphere-dependent range performance of long-wave and mid-wave IR imagers

Dhar, V.; Khan, Zafar

doi:10.1016/j.infrared.2008.05.001

Cited by 10 publications

(5 citation statements)

References 28 publications

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“…Atmospheric transmission models are fairly complicated and use a huge database, so they are suitable for dedicated calculations and analysis [97,98]. The average user in the field cannot use these calculations, so need simplified methods based on locally available meteorological conditions-related parameters that have a key influence on atmospheric transmission: meteorological visibility and air humidity.…”

Section: Thermal Imager Range Predictionsmentioning

confidence: 99%

Thermal Imager Range: Predictions, Expectations, and Reality

Peric¹,

Livada²,

Peric³

et al. 2019

Sensors

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Imaging system range defines the maximal distance at which a selected object can be seen and perceived following surveillance task perception criteria. Thermal imagers play a key role in long-range surveillance systems due to the ability to form images during the day or night and in adverse weather conditions. The thermal imager range depends on imager design parameters, scene and transmission path properties. Imager range prediction is supported by theoretical models that provide the ability to check range performance, compare range performances for different systems, extend range prediction in field conditions, and support laboratory measurements related to range. A condensed review of the theoretical model’s genesis and capabilities is presented. We applied model-based performance calculation for several thermal imagers used in our long-range surveillance systems and compared the results with laboratory performance measurement results with the intention of providing the range prediction in selected field conditions. The key objective of the paper is to provide users with reliable data regarding expectations during a field mission.

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Section: Thermal Imager Range Predictionsmentioning

confidence: 99%

Thermal Imager Range: Predictions, Expectations, and Reality

Peric¹,

Livada²,

Peric³

et al. 2019

Sensors

View full text Add to dashboard Cite

show abstract

“…The radiation from both target and background is absorbed and scattered as the radiation propagates through the atmosphere between target and imager. Though the atmospheric transmission is dependent on wavelength of radiation but for just proving the concept an average value for the atmospheric transmission τ may be used 11 . Apparent temperature difference between target and background at a distance R from the target is ΔT R =τ R ΔT 12 .…”

Section: Effect Of Emissivity On Detection Capabilities Of Thermal Immentioning

confidence: 99%

Estimation of Effect of Emissivity on Target Detection through Thermal Imaging Systems

Sharma

Vasistha

et al. 2017

Def. Sc. Jl.

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The effects of target emissivity on apparent thermal contrast as well as on detection range capabilities of thermal imagers in long wave infrared and middle wave infrared bands were evaluated. The apparent thermal contrast (to be seen by the thermal imager at standoff distance), considering only the emission from target and background, was first computed in both the IR bands in terms of target emissivity and secondly the apparent thermal contrast, considering the background radiation reflected off the target, was also computed. A graphical user interface simulation in MATLAB was prepared for the estimation of total apparent thermal contrast taking into account both the emission and reflection. This total apparent thermal contrast was finally used in night vision thermal and image processing model for predicting the detection range performance of thermal imagers. Results of the analysis show that the effect of target emissivity on thermal contrast estimates is more pronounced in LWIR. The lower thermodynamic temperature difference between target and background at lower values of target emissivity leads to negative thermal contrast which in-turn leads to higher detection ranges.

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“…Detection ranges are more sensitive to temperature and RH variations than the recognition ranges, while identification ranges are the least sensitive. Typically, the crossover temperature is the lowest for identification and the highest for detection 1,4 , since a task that requires high resolution will favor the lower wavelength MW array. Thus, we have concentrated in this paper on the detection range calculations.…”

Section: Crossover Temperature For Low Ambient Temperaturesmentioning

confidence: 99%

“…The advent of dual band imaging systems has not rendered this discussion irrelevant since the more producible FPAs are sequential (single bump per pixel) rather than simultaneous (two bumps per pixel) 1 . The analysis in this paper would be applicable to a dual-band LW/MW (sequential or simultaneous) system or to two single-band LW and MW systems.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the performance of LWIR and MWIR thermal imagers for varying ambient temperature and humidity conditions

et al. 2011

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Hodgkin (SPIE 6207(2006)) extended NVThermIP to be applicable to cold weather conditions. We also (IRPhys&Technol.51 (2008)520) later published an analysis of the effect of varying ambient temperature (T amb ) by modifying the inputs to NVTherm2002, and by using spectrally-weighted atmospheric transmission calculated from MODTRAN at different ambient temperatures and relative humidities (RH). We took into account the effects on the integration time and NETD, and we now account for the variation of ΔT with varying T amb , as Hodgkin has done. The overall trends are similar, but we have NVTherm, not NVThermIP. We vary the parameters associated with Johnson's criteria to obtain similar results. Note that diurnal, seasonal, climatic and microclimatic variations of relative humidity (RH) significantly impact the performance of thermal imagers, especially LWIR ones. We compare the performance of thermal imagers a horizontal mean-sea-level path in clear weather conditions for terrestrial imagers and ground targets/scenes in both LWIR and MWIR bands, as a function of the ambient temperature from -40°C to +40°C and also as a function of RH (30%, 50% and 70%). To understand the differences in the results reported by Hodgkin and our paper, we do a sensitivity analysis as a function of system and environmental parameters (f/#, RH, detection probability, spectral width etc). For one set of parameters, we observe that the range curves R LW and R MW intersect at more than one value of T amb and suggest an analogy to a 're-entrant phase'. We also analyze how motion blur affects the two bands, at different T amb .

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Comparison of modeled atmosphere-dependent range performance of long-wave and mid-wave IR imagers

Cited by 10 publications

References 28 publications

Thermal Imager Range: Predictions, Expectations, and Reality

Thermal Imager Range: Predictions, Expectations, and Reality

Estimation of Effect of Emissivity on Target Detection through Thermal Imaging Systems

Comparison of the performance of LWIR and MWIR thermal imagers for varying ambient temperature and humidity conditions

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