Aviation Electronics Technician 1 - Historic Naval Ships Association

Table 6-1.-Characteristics of IR Radiationthe target and the FLIR attenuates and blurs the targetsignal. The FLIR operator aims the limited field ofview FLIR to search the scene for targets, using asearch pattern and clues, such as radar targets or laserdesignators.The FLIR system uses thermal sensitivity, imagesharpness, spectral response, contrast, and magnificationto produce a visual image of the thermal scene.The operator uses training, experience, and imageinterpretation skills to detect and identify targets.INFRARED RADIATIONThe atmosphere is a poor transmitter of infraredradiation because of the absorption properties of CO2(carbon dioxide), H2O (water), and 03 (ozone).Infrared radiation is broken into four regions, as canbe seen in table 6-1. Only the first three are used withthis system. Figure 6-3 shows the transmissionspectrum of the atmosphere. You can see that the besttransmission is between 3 µm and 5 pm, and between8 µm and 14 µm. The range between thesewavelengths is known as a window. Infrared imagingdevices are designed to operate in one of these twowindows, usually the 8 µm to 14 µm window.Infrared Radiation SourcesAll matter whose temperature is above -273°C(absolute zero) emits IR radiation. The amount of theradiation emitted is a function of heat. Theoretically,a perfect emitter is a black body with an emissivity of1. Realistically, the best emissivity is somewherearound 0.98. The emissivity of various objects ismeasured on a scale of 0 to 1.Figure 6-3.-Transmission spectrum of the atmosphere.6-3