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How Do Thermal Imaging Cameras Work?

thermal-imaging-cameraThermal imaging camera, or infrared camera, is a type of camera which forms an image through infrared rays or heat as opposed to a normal camera which forms images with the help of visible light. Thermal imaging cameras have been around since the 1920’s but have only been put to mass use since the 1990s.


The first thermal imaging device invented was by the Hungarian scientist, Kálmán Tihanyi, as early as in 1929. In 1947, the first infrared scanner was invented, and it took around one hour to scan one line. At this stage, most of the innovations in this field were developed for military purposes. The British infrared camera was known as the Yellow Duckling and was developed in the 1950s. Similarly, the US Military, along with Texas Instruments and Honeywell, made developments in this area at the same time. In 1969, Michael Francis Tompsett patented his camera from which the modern technology in this field developed. Today, infrared cameras have been put to use in different fields.

How it works

Thermal imaging cameras work with heat, and are hence, very useful equipment for many purposes. The lens of the camera is a special one used for working with infrared rays. It concentrates all the waves from the thermal or infrared energy present in view on an infrared sensor array. This leads to the creation of a detailed temperature pattern, which is known as a thermogram. This is then converted into electrical signals, which are then received by a processing unit. This translates the electrical signals received from the thermogram into display data, i.e., an image which can be seen by the person using the camera.

These images are not clear-cut reflection images as we get through a normal camera. They are based on the amount of heat radiating from each object. The more heat an object emits, the whiter it will appear. For instance, a person will appear whiter when seen through the lenses than most other objects, because of their body heat. The cooler objects will appear in shades of grey.


There are two main types of thermal imaging cameras: cooled infrared detectors and uncooled infrared detectors.

Cooled cameras use detectors are kept in a vacuum sealed box and cryogenically cooled. This cooling activates the semiconductors to form the images. Without this cooling, the sensors would be unable to form an image because they would be flooded by their own radiation. These cameras are more sensitive but are expensive and energy intensive.

Uncooled cameras, on the other hand, use room temperature sensors. These sensors function with change in resistance, voltage, or current caused by heat or infrared rays. These cameras are less expensive and more portable. But the quality of the images are lower than that of cooled cameras.


Originally, the thermal imaging cameras were developed for military purposes by different governments around the world. It was first used in the Korean War. Today, these cameras are ubiquitous and are used in a variety of industries and fields. They have also increased efficiency and decreased in cost. Some of the most useful and frequent applications of this invention is in the following fields:

Law enforcement: There are myriad uses of thermal imaging cameras in law enforcement. It can be used in detecting suspects and in spotting dangers in dark and camouflaged areas. Another use is to detect money, drugs, or stolen artifacts stashed in away.

Firefighting: Firefighting techniques received a major boost when thermal imaging began to be used in fighting fire. Because the heat emitted in a fire can be easily detected through these cameras, it becomes much easier to extinguish them while remaining at a safe distance.

Construction: It is a very useful tool in the construction and home inspection industries. With the help of infrared cameras, leaks and defects can be easily detected. It can also be used to detect loss of heating and cooling and increase energy efficiency.

Natural disasters: Thermal imaging is used during natural disasters such as earthquakes in order to find people trapped in the rubble. This saves precious time and assists the rescuers in working efficiently even under tough conditions.

Medicine: Thermal imaging also has its uses in the medical field. It is often used to determine inflammation and irregular blood flow in the body.

As advances happen in the technology, these cameras get more and more sophisticated and their uses and applications are increasing with time.