Thermography
lastmod 2025-03-13created 2025-03-122 edits
Infrared thermography, thermal video, or thermal imaging is a process in which a thermal imaging camera captures and creates an image of an object using the infrared radiation emitted from the object, and is an example of infrared imaging science.
Synopsis
Infrared is a form of energy transfer: electromagnetic waves in the 0.75-1000㎛ wavelength band, longer than visible light (Visible Wave) and shorter than microwaves (Micro Wave). It has characteristics similar to a real image, travels through space at the speed of light, and exhibits phenomena such as reflection, refraction, absorption, and radiation.
Since the body temperature of healthy people is between 36 and 37°C, a reading of 37.5°C is a high fever, and the upper limit of fever caused by a virus is around 39.5 degrees. Recent equipment (such as the Raven-384 camera) can detect temperature differences as small as 0.05°C, so, as in the figure above, it is widely used for swine flu.
According to Frank's research theory of heat-emitting bodies, every warm object radiates energy along a fixed path. A black body radiates ideal energy on its own, without interference from other energy sources and without reflecting heat outward. The performance of a black body depends on its price; a very high-quality black body reflects almost none of the energy radiated from external energy sources. The emissivity of a good black body goes up to 0.999, and an emissivity of 0.95-0.99 is enough for measuring human body temperature. Interestingly, human skin is very similar to a black body. Skin has a value of about 0.98, so it reflects almost none of the external heat energy. A person's heat radiation can be regarded as equal to the temperature inside the body, and this principle makes temperature measurement possible.
In thermal temperature screening of air travelers, the black body used with the Raven-384 is usually installed above the heads of passing travelers. During system setup, the built-in software performs statistical analysis relating the actual operating environment between systems to a local database. Typically, in the varied usage environments of different users, all of these environmental variables cannot be known in advance. Humidity is the most important in such environments because it affects the skin's ability to radiate heat. To reduce these variables, a few people are tracked and some statistics are used to obtain images of healthy people active in the relevant work environment, and in most cases this setup must be done before the system is first used.
Cameras
- Thermographic camera - Wikipedia, the free encyclopedia
- Thermal imaging camera - Namuwiki
- Types of thermal imaging cameras
- flir guide
A thermographic camera or infrared camera is a device that creates an image using infrared (IR) radiation, similar to an ordinary camera that forms an image using visible light. Instead of the 400-700 nanometer (nm) range of a visible-light camera, an infrared camera is sensitive to wavelengths from about 1,000nm (1 micrometer or μm) to about 14,000nm (14μm). The practice of capturing and analyzing the data they provide is called thermography.
Night Vision
Measures by emitting infrared wavelengths from the camera, or amplifies moonlight. An example is the green night-vision-goggle-like footage used when filming animal movements in documentaries. In fact, CCTV infrared cameras also belong here (most emit infrared with LEDs), and for some unknown reason they are called IR cameras. Strictly speaking, however, if a camera emits and receives IR, Night Vision is the correct term.
Infrared Thermal Camera
Also called an IR camera or infrared camera, it does not emit infrared but uses the infrared radiated by animal bodies. It is widely deployed as a body heat diagnostic device (Thermal Imaging Camera). When the subject is an object or an animal, it uses the principle that light of a corresponding wavelength is emitted according to the temperature of the body (object). Every object above absolute zero (-273 degrees) emits light of a corresponding wavelength; a human, with a body temperature of around 37 degrees, emits in the 8-14um band, the far-infrared part of infrared.
Company
The leader in this field is FLIR1, a thermal imaging camera manufacturer with more than 40 years of history and over 50% of the global market share. For thermal imaging, FLIR products are said to be better than Fluke's; Fluke is probably a company that recently acquired a thermal imaging camera manufacturer and is succeeding. FLIR Systems was started in 1958 by the Swedish company AGA. Companies such as Japan's NEC, HIOKI, and Yokogawa also produce many.
FLIR
FLIR (forward looking infrared) is an imaging technology that detects infrared radiation, a system that captures infrared images of the area ahead with a video camera. It is not the name of a specific system but a generic term for this kind of system. The infrared wavelengths that FLIR detects differ from those of night vision devices, which operate in the visible and near-infrared range (0.4 ~ 1.0 µm). Infrared can basically be divided by range into two types: long-wave infrared and mid-wave infrared.
Long-wave infrared (LWIR) cameras operate at 8 ~ 12 µm and can see the heat of hot engine parts or human body heat several miles away, but because infrared light is absorbed, scattered, and refracted by air and water vapor, long-range viewing is harder than with mid-wave infrared cameras. Some long-wave FLIRs require cryogenic cooling of their detectors, but moderately sensitive FLIRs do not require cryogenic cooling.
Cameras operating in the 3 ~ 5 µm range are called mid-wave infrared (MWIR). Because mid-wave infrared cameras are less affected by water vapor absorption, long-range viewing is relatively easy compared with long-wave infrared cameras, but they generally require more expensive detector arrays and cryogenic cooling.
Many FLIR systems use digital image processing to improve image quality. Because of limitations in the manufacturing process, FLIR sensor arrays often have responsivity that varies grossly from pixel to pixel. To remedy this, the response of each pixel is measured at the factory, and a transform, mostly linear, maps the measured input signal to an output level.
What is Korean: 비균일 보정 (Non-uniformity correction; NUC)?
See Non-Uniformity Correction for details.
Documentation
- Infrared thermography handbook for R&D professionals
- http://www.flirmedia.com/MMC/THG/Brochures/T559243/T559243_KR.pdf
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T559243_KR.pdf