Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB

Signature Assessment

Signature Assessment

THE INFLUENCE OF THE ATMOSPHERE ON THE THERMAL IMAGE

Assessment of camouflage materials and analysis of construction material for thermographical inspections, verification and validation of thermal simulations.

The rendition of an object in a thermal image (signature) is decisively influenced by its environment. In order to make a statement about the visibility of an object in a certain environment, it is therefore necessary to determine the influence of decisive environmental factors on the thermal appearance.

 

footprint burner warm hand

 

A method for characterizing distinctive features of textiles worn on a thermal image has been realized.

For this purpose, a textile is placed on a heating plate with a temperature control in the environmental simulation laboratory. The temperature is set to 34 °C, which corresponds to the skin temperature of the human body. Afterwards, a sequence of thermal images is recorded at different wind speeds for 5 min at a defined air temperature in four different environmental scenarios with an image frequency of 1 Hz under the following conditions:

  • without any radiation source
  • an artificial sun as a radiation source 
  • artificial sun and cold sky as a radiation source
  • cold sky as a radiation source

 

The measurements are performed for an angle of incline of the sample of 30° and 45° to the vertical axis in order to achieve different reflective conditions vis-à-vis the radiation sources.

The mean temperature of the textile surface investigated is then determined and averaged over time throughout the sequence.

To determine the conspicuity of a person, who wears the textile examined, in a natural environment the air temperature is used for comparison as the air temperature dominates the temperature of green vegetation in a thermal image.

Based on the behavior caused by different influences, conclusions can be made about the behavior of the textile in a wide variety of different scenarios, which were not investigated themselves.

The reproducibility of the measurement procedure returns a maximum deviation of 0.3 °C in the worst case scenario. The results of the validation of the measurement method can be provided on  request.

As the heating plate can be heated stably to temperatures of up to 80 °C, it is also possible to use the method for analyzing covers of technical devices like generators or the like.

 

Outline of the experimental set-up, the cold heaven is above the set-up

 

  • Die Bewertung der Effizienz von signaturverändernden Maßnahmen ist heute sowohl für den passiven Schutz von militärischen Objekten als auch in der zivilen Sicherheitsforschung von großer Bedeutung.

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