After World War II, the first generation of infrared imaging equipment used in the military field was developed by Dextran Instruments Company of the United States after nearly a year's exploration, and it was called Infrared Sight Finding System (FLIR). It uses optical and mechanical systems to scan the infrared radiation of the measured target. Photon detectors receive two-dimensional infrared radiation signals, which are converted into video image signals through photoelectric conversion and a series of instruments. The prototype of this system is a non-real-time automatic temperature distribution recorder. Later, with the development of indium antimonide and germanium-doped mercury photon detectors in the 1950s, systems for high-speed scanning and real-time display of thermal images of targets began to appear.
In the early 1960s, AGA company of Sweden successfully developed the second generation infrared imaging device, which added the temperature measurement function to the infrared seeker system, and was called infrared thermal imager.
At first, due to confidentiality reasons, it was limited to military use in developed countries. The thermal imaging equipment put into use can detect other targets, camouflage targets and high-speed moving targets at night or in thick clouds. Due to the support of national funds, the investment in research and development costs is high, and the cost of instruments is also high. In the future, considering the practicality in the development of industrial production and combining the characteristics of industrial infrared detection, the cost of the instrument will be reduced. According to the requirements of civil use, measures such as reducing scanning speed to reduce production cost and improve image resolution have gradually developed into civil use.
In the mid-1960s, AGA developed the first industrial real-time imaging system (THV), which was cooled by liquid nitrogen and powered by 1 10V power supply, weighing about 35kg, and was not portable when used. After several generations of improvement, the infrared thermal imager developed by 1986 adopts thermoelectric refrigeration. 1988, which integrates temperature measurement, modification, analysis, image acquisition and storage, weighs less than 7 kg, and its function, accuracy and reliability have been significantly improved.
In the mid-1990s, FSI Company of the United States first successfully developed a new infrared thermal imager (CCD), which was commercialized from military technology (FPA) and belonged to the focal plane array structure. The technical function is more advanced. When measuring the temperature in the field, you only need to aim at the target to take an image and store the above information on the PC card in the machine, that is, all operations are completed. You can use software to modify and analyze the settings of various parameters indoors. Finally, the test report is directly obtained. Due to the improvement of technology and the change of structure, complex mechanical scanning has been replaced. The instrument weighs less than 2 kg and can be easily operated with one hand like a hand-held camera.
At present, infrared thermal imaging system has been widely used in electric power, fire fighting, petrochemical and medical fields. Infrared thermal imager plays an important role in the development of world economy.
2.3 Classification of Thermal Imagers
Infrared thermal imager is generally divided into scanning imaging system and non-scanning imaging system. The photoelectric scanning imaging system adopts single-element or multi-element (the number of elements is 8, 10, 16, 23, 48, 55, 60, 120, 180 or even more) photoconductive or photovoltaic infrared detectors. When using a single detector, the speed is slow, mainly because the frame response time is not fast enough and the multi-element array. Non-scanning imaging thermal imager, such as array staring imaging focal plane thermal imager introduced in recent years, belongs to a new generation of thermal imaging devices, and its performance is far superior to that of optical scanning thermal imager, and it has a tendency to gradually replace optical scanning thermal imager. The key technology is that the detector is composed of a monolithic integrated circuit, and the whole field of view of the measured object is focused on it, which makes the image clearer and more convenient to use. The instrument is very small and light, and has the functions of auto-focusing image freeze-frame, continuous amplification, point temperature, line temperature, isothermal, voice labeling and so on. The instrument adopts PC card, and the storage capacity can be as high as 500 pictures.
Infrared thermal imager is a kind of infrared thermal imager. Infrared thermal TV receives infrared radiation from the surface of the target object to be measured through a pyroelectric camera tube (PEV), and converts the invisible thermal image of the thermal radiation distribution in the target into a video signal. Therefore, the pyroelectric camera tube is an optical key device of infrared thermal TV, which is a thermal imaging device with real-time imaging, wide spectrum imaging (good frequency response to 3 ~ 5 microns and 8 ~ 14 microns) and medium resolution, mainly composed of lenses. Its technical function is to focus the infrared radiation of the target on the pyroelectric camera tube through the lens, and realize it by using the technologies of constant temperature TV detector, electron beam scanning and target surface imaging. The main parameters of the thermal imager are:
2.3. 1 working band; The working band refers to the response wavelength region of the infrared detector selected in the infrared thermal imager, which is generally 3 ~ 5 microns or 8 ~ 12 microns. ..
2.3.2 detector type; The detector type refers to the infrared equipment used. It is a photoconductive or photovoltaic infrared detector, which has one unit or multiple elements (element 8, 10, 16, 23, 48, 55, 60, 120, 180, etc.). ), its elements are lead sulfide (PbS), lead selenide (PnSe) and so on.
2.3.3 scanning system; Generally, it is China standard TV system and PAL system.
2.3.4 display mode; Refers to whether the screen display is black and white or false color.
2.3.5 Temperature measuring range; Refers to the temperature range between the lower limit and the upper limit of the measured temperature.
2.3.6 Temperature measurement accuracy; Refers to the percentage of the ratio of the maximum temperature error of infrared thermal imager to the instrument range.
2.3.7 Maximum working hours; Infrared thermal imager allows continuous working time.
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