Thermal Monocular camera that “see” heat instead of light. Sometimes referred to as cameras, they produce an image that portrays objects using their temperature instead of their visible properties.
So how does thermal monocular camera see heat? All objects warmer than absolute zero (-273°C/-459°F) emit infrared radiation in the MWIR and LWIR wavelengths (3µm–14µm) in an amount proportional to the temperature of the object. Thermal Monocular camera focuses and detects this radiation, then translates the temperature variations into a greyscale image, using brighter and darker shades of grey to represent hotter and cooler temperatures, which gives a visual representation to the heat profile of the scene. Many thermal imagers can also apply color profiles to these images, showing hotter objects as yellow and cooler objects as blue for example, to make it easier to compare temperatures in the image.
In order to “see” radiated heat, special lenses and sensors are needed to focus and detect electromagnetic radiation in the MWIR (mid‑wave infrared) and LWIR (long‑wave infrared) ranges.
Thermal Monocular camera Sensors
To detect thermal energy, special FPAs (Focal Plane Arrays) are required. These can be divided into two types, cooled and uncooled detectors.
Cooled detectors exist to maximize detection performance. Since we’re detecting radiated heat, any heat from the camera components themselves makes it harder to see the image of the scene. Both our high-definition MCT (Mercury Cadmium Telluride or HgCdTe) sensors and our Indium Animonide (InSb) sensors incorporate a cryogenic cooling system to reduce the “noise” from the heat of the internal camera components and the sensor itself. This allows for detection of thermal energy with an accuracy as fine as 0.025°C.
Uncooled detectors are also available which are more affordable and compact due to the lack of a cryogenic cooler. We use vanadium oxide (VOx) detectors in our uncooled cameras and combine them with wide aperture lenses to maximize their performance (see below).
Lenses for Thermal Monocular camera
For visible light, glass lenses are typically used to focus light on a camera sensor, however glass is not transparent to thermal radiation. Instead, thermal lenses are constructed from a special metal called Germanium (Ge). This is a relatively rare element and thus is quite costly, with raw prices often as high as $2000 per kilogram. Depending on the type of sensor, lenses of different specifications are required.
Our cooled sensor thermal cameras are designed to have the best long-range detection. We have a wide variety of long-range continuous zoom lenses, allowing the operator to smoothly transition between wide angle and long range. Our germanium lenses are available in lengths of up to 1400mm, allowing us to reach detection ratings of over 50km.
Since uncooled thermal imagers are inherently less sensitive than cooled sensors, we maximize the quality of those images by using lenses with an extremely wide aperture of ƒ/1.0. This wide aperture allows more thermal energy through to the sensor for detection; twice as much energy as that of a lens with an aperture of ƒ/1.4, or four times as much as ƒ/2.0.
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