Investigation of the effect of atmospheric transmission on night vision systems

The electromagnetic spectrum band which can be seen by humanbeings is classified as visible region. Infrared (IR) region is a regioninside the electromagnetic spectrum band, far away from the visiblered. All substances which have temperature above absolute zero (OKelvin, -273 ° emit radiation. Systems which sense the radiation atC)infrared region are called ?Infrared Thermal Vision Systems?. By thehelp of these systems thermal visions can be detected even at darkatmosphere. A generalized infrared system has 6 sub systems. Thesesub systems are; source, background, atmospheric region, opticaldevices, detector and signal processing. This 6 sub systems determinethe performance of thermal systems. In this study, effects of theatmospheric gases to thermal vision systems are investigated. Whenthe gas mechanisms are investigated, it is seen that the highesttransmission is at 8-12 µm wave length region and the most effectivegas which decreases the transmission is water vapor. For this reason,effect of water vapor at 8-12 µm band is investigated. Experimentalstudies were done using AN/TAS-4A Night Vision Device which is in theinventory of the Land Forces Command at Electro-Optical SystemsMaintenance Center and then at Aselsan Company. In this study, theoutput voltage of the detector in the thermal vision system weremeasured to investigate the effect of temperature and humidityvariation of atmospheric transmission. It was observed that when thetemperature and humidity of the environment increased, thetransmission was decreased. The results were found in agreement withliterature.Science Code : 905.1.035Key Words : Atmospheric transmission, thermal cameras,detectorPage Number : 90Adviser : Prof.Dr.Müzeyyen SARITAŞ