There are currently two types of infrared thermal imaging sensors on the market, cooled and uncooled. Uncooled IR detector operates at ambient temperature. It is based on semi-conductor industry and thus usually can be fabricated in big volume with small size and low cost. Uncooled IR detectors are widely used in portable/handheld/mobile devices. Cooled IR detectors are packaged in a unit that keeps them at an extremely low temperature which shall be supported by a cryo cooler. They are much bigger, more expensive and less reliable than uncooled sensors, mainly due to the complex cooling systems they require. However, the cooled systems are incredibly sensitive and usually work with long focal length optics to achieve long range mission.

The cooled infrared focal plane detector operates at a low temperature which is provided by a detector dewar cooler (ddc). It has high sensitivity and can distinguish more subtle temperature difference than uncooled infrared detector. It can detect, identify and recognize objects at a very long range which is more than ten kilometers away. The structure of cooled detector is very complex which results in a relatively high cost than uncooled detector.

In nature, all objects whose temperature is higher than absolute zero (-273℃) can radiate infrared rays. By using the infrared camera detector to measure the infrared radiation temperature difference between the target itself and the background, you can get different infrared images, which are also called thermal images.

Infrared radiation that emitted by target enters the sensing range of the thermal detector, then the infrared detector converts the radiation signal of different intensity into the corresponding electrical signal, and then through amplification and video processing, forms the infrared image that can be observed by the naked eyes.