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How does thermal imaging work? A closer look at what is behind this remarkable technology

June 11, 2007
By: Will Roberts

Two primary technologies are used for night-vision surveillance applications. These include image enhancement and thermal imaging. The basic concept behind image enhancement is to amplify the visible light in an area to enhance visibility. Thermal imaging on the other hand is a bit more complex. This technique refers to the process of capturing the heat from an object, which is undetectable to the human eye, and transforming it into an image that can be viewed. The purpose of this article is to seek to answer the question, how does thermal imaging work?

Before we take a closer look at thermal imaging technology, it is important to have an understanding of what thermal energy itself is. Thermal energy is a part of the electromagnetic spectrum. It makes up the upper portion of the infrared light spectrum. You cannot see thermal energy because it is emitted from objects as heat, not reflected as light. The hotter an object is, the more thermal energy it emits. However, all objects even inanimate ones, such as buildings, or even ice cubes, emit some form of thermal energy. Infrared thermal imaging cameras are able to capture this thermal energy and transform it into an image you can see.

The process by which a thermal imaging camera transforms thermal energy into visible light consists of five basic steps. These steps are:

1. Utilize a specially designed lens to focus the infrared radiation that is given off from all objects within the field of view of the camera lens.
    
2. Infrared detectors are then used to scan this focused radiation. The detectors create what is called a thermogram, or temperature map.
    
3. The thermogram is then translated into electric impulses.
    
4. The electric impulses are then sent to a signal-processing unit where they are translated into data. The signal-processing unit is a tiny chip that is embedded on a circuit board, which is used to translate the electric impulses into usable data.
    
5. Once translated, the signal-processing unit sends the data to the display where it then becomes visible to the viewer.

Since thermal imaging cameras work solely by capturing infrared radiation given off from an object, no light at all is required for the device to function. In fact, a thermal imaging camera can function optimally no matter what the surrounding lighting conditions, bright or dim.

In addition to the ability to function in a wide array of lighting conditions, thermal imaging cameras can be used to reveal aspects about ones surroundings where no visible sign of evidence exists. For example, a thermal imaging camera might reveal an area of ground that has been dug up to bury something. Another example could include an area of a wall that has been painted or repaired recently. It will appear slightly darker through a thermal imaging camera. This unique ability to detect and gather evidence that would have previously gone undetected makes thermal imaging cameras invaluable devices for law enforcement and military personnel.

There are two basic types of thermal imaging cameras, un-cooled, and cryogenically cooled. Most thermal imaging devices are un-cooled. This simply means that the camera itself functions without an additional cooling unit attached. A cryogenically cooled thermal imaging device on the other hand, is much more expensive, but produces a much clearer image and is much more sensitive to temperature variations. This means the corresponding image contains much more detail and depth.

Thermal imaging cameras were first designed for use by the military to help locate enemy targets. As improvements were made to the technology, these camera devices became more and more practical for commercial uses such as perimeter surveillance and other security applications. Now more than ever, thermal imaging cameras are continuing to be used on a much broader scale. There are several other applications where thermal imaging technology can be very useful. These include, security and surveillance, navigation, hunting, law enforcement, and hidden object detection. As the technology continues to improve and prices drop, more businesses and consumers will consider thermal imaging devices for use in their video surveillance systems or in related applications.

It is easy to see how thermal imaging technology can be superior to traditional video surveillance systems. The technology is very versatile, and can provide a great deal more information than can be garnered by a traditional video surveillance camera. As prices for these cameras continue to drop, we will likely be seeing and hearing more and more about this remarkable technology.

Also See:  [ Free webcam motion detection software for home surveillance ]
[ Using hidden surveillance cameras to counter covert surveillance equipment ]
[ FLIR infrared cameras & how an infrared thermal imaging camera works ]

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