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Characteristics of thermal imager

2013-12-06

Characteristics of thermal imager
All objects in nature above absolute zero(-273℃) emit IR energy and IR emission exists most widely in nature. Atmosphere and clouds can absorb visible light and infrared radiation, but they are transparent for infrared whose wavelength is fall within in 3μm to 5μm and 8μm to 14μm. Therefore, these two infrared bands are called “atmospheric windows.” So we can make use of this “atmospheric windows” to observe the surroundings in completely darkness night or harsh environment with dense smoke. With this characteristic, thermal imaging technology can be used for night-time security surveillance and forest firefighting monitoring systems.

Thermal imager applications
Using infrared thermal imaging technology to detect infrared radiation from the target object, and through the photoelectric conversion, signal processing means, the temperature distribution of the target object image into a video image of the device, called a thermal imager. Thermal imager can be broadly divided into two types: those with cooled infrared image detectors and those with uncooled detectors. Cooled thermal imager is generally used for military purpose with its high thermal sensitivity and complex structure. While uncooled type is less sensitive than cooled type, its performance can satisfy the demand of majority military and almost all civilian areas. Therefore, uncooled type, without cooled detector, is more reliable and more cost-effective than cooled type.


 
 1、Monitoring in darkness night or complicated environment
As we know, visible light equipment couldn’t work normally at night and it’s easy to expose if it works under the help of light. Besides, the use of low-light-level night version equipment also needs the help of light because it works for visible wavelengths. However, thermal imager absorbs infrared radiation passively from the target, and it can work normally all day and night without exposure. When it happens to rain, fog and other bad weather, the effect of visible light observation is bad because it is weak anti-jamming and short wavelength. But thermal imager can still detect the target accurately under the same condition. This is because thermal radiation (especially between 8 ~ 14um) can penetrate rain and fog more readily than visible radiation with its longer infrared wavelengths and good penetration properties.
So we can draw a conclusion that the thermal imager can normally work for detecting miscellaneous target, like people and car, at night or in bad weather.

 2. Firefighting
Thermal imager is a device which is capable of reflecting the temperature across the target surface. In addition to security monitoring at night, thermal imager can work efficiently for firefighting alarm. In large areas of forest, fire disaster is always caused by unnoticed hidden fire which is the root cause of devastating fire and it is difficult to discover the signs of hidden fire by Common methods. However, the use of thermal imager can efficiently help people rapidly discover the hidden fire and ignition point as well as the extent of fire through the smoke and make early prevention and extinguished.

3. Identify camouflaged and hidden targets
The camouflage effect is responsible for preventing detection in the visible range. Generally, criminals usually hide in the bushes and trees to commit crimes as the outdoor harsh environment and human visual illusion easily leads to wrong judgments. Thermal imager can absorb infrared radiation passively from target. As the temperature and infrared radiation from car and human-body are greater than bushes and trees, it’s not easy to camouflage and make wrong judgments.