Infrared telescope

Telescope receiving infrared radiation from celestial bodies

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Infrared telescope, receiving celestial bodies Of infrared radiation A telescope. The shape structure is similar to that of optical mirror, and some can be used for infrared observation and Optical observation 。 But when making infrared observation terminal equipment Different from optical observation modulation technique To suppress Background interference And use interferometry to improve its resolution.

Chinese name: Infrared telescope
Foreign name: infrared telescope
Band: Wavelength 800-1 000nm

Properties: receive celestial bodies Infrared radiation telescope
Methods: Interferometry
Invention time: The second half of the 19th century

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definition

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An instrument that can detect the movement of people, objects, and vehicles 500 meters or more away in extremely harsh weather conditions. A kind of telescope. It is also called passive infrared telescope. The characteristics of passive infrared telescopes are: they do not interfere with each other; It can track without sending signals; Low power consumption, long distance, narrow beam; Easy installation and quick response. Infrared eye in perimeter protection, boundary and fence observation, battlefield direction finding system, fire and explosion detection, traffic calculation flow and control High voltage wire Rod protection has a wide range of applications.^[1]

Structural characteristics

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Infrared telescope and ordinary Optical telescope Its principle and structure are basically the same, and its special requirements include:

1) The infrared telescope should not have a closed lens tube, but should use Truss structure The mechanical structures in the field of view should be minimized, and those structures that cannot be defaulted should not be blackened but polished to reduce their infrared Emissivity , or wrapped with aluminum foil or gold foil.

2) General infrared telescope coke Relatively large, f/20~f/50, some up to f/100. A large focal ratio is conducive to reducing the brightness of the sky background to reduce the radiation noise of the sky background. Large focal ratio can also be reduced Secondary mirror Size, to facilitate modulation, can also be reduced Primary mirror The size of the central hole, thus reducing the infrared from the telescope Background radiation 。

3) In the matching of primary mirror and secondary mirror, smaller secondary mirror and small secondary mirror bracket are used to avoid thermal radiation To facilitate the modulation of the secondary mirror.

4) The primary and secondary mirrors are silver or gold plated. Mirror gold or silver plating is more sensitive to infrared radiation than aluminum plating reflectivity High, low emissivity.

5) High pointing accuracy and wide and bright Guide star field 。 This facilitates infrared detection of dark or invisible objects.

6) Application Infrared modulation technology Different methods can be used to realize infrared modulation, mainly including: ① focal plane Modulation ② Secondary mirror Modulation. ③ Primary mirror Modulation.^[2]

Imaging principle

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Infrared telescope can see infrared that is band (wavelength 800-1000nm). In military applications Night vision telescope One of. Of course, infrared telescopes are more often used Astronomical observation Medium. Infrared telescope The infrared ray is converted into Electron flow , and then Electronics Multiply, and finally make the electrons hit the fluorescent screen and become visible light. As long as there is temperature, infrared will be generated. It is a special lens that can pass through and display infrared.

Infrared telescope application

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The infrared observation image is also quite different from the optical image. Since the earth's atmosphere has only seven narrow "windows" for infrared, infrared telescopes are often located in high mountain areas. Most of the world's better ground-based infrared telescopes are installed in Monakia, Hawaii, the United States, which is the research center of the world's infrared astronomy. Built in 1991 Keck telescope It's the largest infrared telescope caliber It is 10 meters long and can be used for both optical and infrared purposes. In addition, infrared telescopes can also be mounted on high-altitude balloons. The maximum aperture of the infrared telescopes on the balloons is 1 meter, but the effect is comparable to some infrared telescopes with larger aperture on the ground. Every different appearance of the infrared telescope must require a battery, because the infrared ray emitted by the object is invisible. The machine needs to receive the infrared ray and send the corresponding visible light 。 It needs electricity to emit light. There are many kinds of infrared, most of them LLL night vision system It also has infrared function. Its infrared belongs to short wave infrared, which is a little longer than visible light, similar to Remote control 。 This night vision device is designed for infrared illumination, so that it is not easy to be found. Another is Thermal imaging In fact, thermal imaging is also to collect the infrared emitted by hot objects, but this kind of infrared wavelength is very long and cannot be seen with ordinary low light level night vision devices. The advantage of thermal imaging is that it can effectively observe heat source , for example mammal , cars, etc., are of great military use.

Development history

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The earliest infrared observations can be traced back to the end of the 18th century. Due to the absorption and scattering As a result, infrared observation on the ground is limited to a few near-infrared windows, so more infrared is needed band The space infrared observation must be carried out. From the second half of the 19th century, Infrared astronomy The observation really began. Originally it was used High-altitude balloon Later, it developed into aircraft carrying infrared telescopes or detectors for high-altitude observation. On January 23, 1983, the United States, Britain and the Netherlands jointly launched the first Infrared astronomical satellite IRAS。 Its main body is a telescope with an aperture of 57cm, mainly engaged in sky survey. The success of IRAS has greatly promoted the development of infrared astronomy at all levels. The observation source of IRAS is still a hot target for astronomers. It was jointly established by Europe, the United States and Japan on November 17, 1995 Infrared Space Observatory ISO launches. The main body of ISO is a R-C telescope with an aperture of 60 cm. Its function and performance are much better than that of IRAS line. Compared with IRAS, ISO has wider band Scope, higher space resolving power , Higher sensitivity (about 100 times that of IRAS) and more.^[3]

Infrared telescope (7 sheets)

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