Thermal Camera Technology

by Basmah Alshalhoub - Date: 2010-08-14 - Word Count: 511 Share This!

Thermographic camera or what is called FLIR, Forward Looking Infrared, is type of cameras which produces an image with the use of infrared radiations or wavelength that differs from the common cameras which use the visible light.
How do thermal cameras work? Since it depends on the wavelength, it's necessary to know a bit about the radiations produced by objects. Each object produces a certain amount of black bodies. From its name we can guess that it absorbs the electromagnetic radiation falling on it.

It is black because it cannot reflect or even transmit these radiations, which make the object black when it becomes cold. So, it is the camera's job to detect these radiations, since, the more temperature the object is, the more production of infrared radiation of black bodies. It is the same process done by a usual camera that handles visible light.

Images from infrared cameras prefer to use sensor, which does not distinguish the various wavelengths of infrared radiations. It is capable of working in a complete darkness regardless the surrounding light, that is, light does not affect thermal cameras. However,, a color camera needs more complex system to differentiate between the different wavelengths.

It is the role of the thermal camera to detect the radiations. Thus, knowing more about the types of these detectors can be beneficial for their users.
They are of two types: Cooled infrared detectors and Uncooled infrared detectors.

Cooled infrared detectors are usually contained in a thermos, which separates the components from the ambient environment. These detectors are very important because they cool the sensors and prevent them from burning. Each captured photo must be taken a few minutes later so the camera can work again properly. Cooling is both "power-hungry and time-consuming", besides, it's too expensive.

How does the cooling system work inside this kind of camera? First, there are two cooling systems; one of them is too expensive, but provides higher qualities, and the other is more proper to certain fields.

Regarding to the main system, rotary Stirling engine cryocoolers, though it is costly but it provides higher image qualities than the un-cooled infrared detectors. The other cooling system is to use nitrogen gas bottled at high pressure. The pressurized gas is expanded through small hole and then passed over a micro-sized heat exchanger leading to renew cooling through Joule-Thomson effect. Joule-Thomson effect describes the change of temperature of a gas when it is forced through valve while in isolation so there is no change of heat with the surrounding area.

On the other hand uncooled infrared detectors use a sensor which makes the imaging process at the surrounding temperature or closer to the ambient temperature by using temperature control elements. It is cheaper to produce lower qualities than its counterpart.

After all, what are the benefit and the applications of such cameras? This product is very substantial in various fields. Firefighters, for example, can use it for rescuing people to see through smoke and to locate people's position in the firing place. It also can be used in laboratories, chemical imaging, military, night vision…and so on.

Related Tags: radiation, detector, sensor, infrared, thermal, stirling engine, wavelength, blackbodies, joule-thomson effect

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