Hydrophobic windscreenfor car

Active IR systems use short wavelength infrared light to illuminate an area of interest. Some of the infrared energy is reflected back to a camera and interpreted to generate an image. Thermal imaging systems use mid- or long wavelength IR energy. Thermal imagers are passive, and only sense differences in heat. These heat signatures (usually black (cold) and white (hot)) are then displayed on a monitor. Because thermal imagers operate in longer infrared wavelength regions than active IR, they do not see reflected light, and are therefore not affected by oncoming headlights, smoke, haze, dust, etc.