All objects, both natural and man-made, emit infrared energy as heat. By detecting very subtle temperature differences of everything in view, infrared (or thermal imaging) technology reveals what otherwise would be invisible to the naked eye. Even in complete darkness and challenging weather conditions, thermal imaging gives users the ability to see the unseen.
First developed for military purposes, thermal imaging has since been adopted by law enforcement, fire and rescue teams and security professionals. This technology can be used to detect approaching people or vehicles, to track the footsteps of a fugitive or to learn why a fire resists extinguishment.
In order to understand thermal imaging, it is important to understand something about light. The amount of energy in a light wave is related to its wavelength: Shorter wavelengths have higher energy. Of visible light, violet has the most energy, and red has the least. Just next to the visible light spectrum is the infrared spectrum.
Infrared light can be split into three categories:
The key difference between thermal-IR and the other two is that thermal-IR is emitted by an object instead of reflected off it. Infrared light is emitted by an object because of what is happening at the atomic level.
Thermal Imaging - Here's how it works:
A special lens focuses the infrared light emitted by all of the objects in view.
The focused light is scanned by a phased array of infrared-detector elements. The detector elements create a very detailed temperature pattern called a thermogram. It only takes about one-thirtieth of a second for the detector array to obtain the temperature information to make the thermogram. This information is obtained from several thousand points in the field of view of the detector array.
The thermogram created by the detector elements is translated into electric impulses.
The impulses are sent to a signal-processing unit, a circuit board with a dedicated chip that translates the information from the elements into data for the display.
The signal-processing unit sends the information to the display, where it appears as various colors depending on the intensity of the infrared emission. The combination of all the impulses from all of the elements creates the image.
Most thermal-imaging devices scan at a rate of 30 times per second. They can sense temperatures ranging from -4 degrees Fahrenheit (-20 degrees Celsius) to 3,600 F (2,000 C), and can normally detect changes in temperature of about 0.4 F (0.2 C).
See: TanYing Thermal Imaging Weapon Sight
There are two common types of thermal-imaging devices:
Unlike traditional most night-vision equipment which uses image-enhancement technology, thermal imaging is great for detecting people or working in near-absolute darkness with little or no ambient lighting (i.e. stars, moonlight, etc, ).
See TianYing Thermal Imaging Weapon Sight Video:
40mk NETD detector with 75mm F1.0 lens, at 600m can clearly see man's two legs; at 850m and 950m can confirm the target,if is person, maybe some supplier called recognition, also can see the image is clear and sharp that can compete with many 640x480 chip detector thermal sight (thermal weapon sight ).
40mk NETD detect with 50mm F1 lens: at 600m person image is a dot, when use for electrice magnification-digital zoom, can find person target.
17microns 55mm lens 50mk show person image size is bigger than 25microns 384x288 75mm lens, but 17microns 55mm lens 50mk image is more clear than 25microns 384x288 75mm lens image.
1).Covertly Finding and Locating Objects Without Visible Light.