Infrared detection in the face of the hottest eart

2022-09-22
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In front of the earthquake, the infrared detection that competes with death every second

at 21:19:46 on August 8, a 7.0-magnitude earthquake occurred in Jiuzhaigou County, Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province, affecting the hearts of hundreds of millions of people. Not only is it as beautiful as heaven, which makes unqualified people worry about the safety of local residents and tourists, but also it is easy for people to think of the Wenchuan earthquake and the tragedy at that time. These days, a large number of rescue forces are struggling to save people in the disaster area

in fact, since the birth of the earth, the earth's crust has been moving continuously and slowly, accumulating huge energy, just as they will break when using enough force to tear paper or bend glass. When it exceeds the tolerance limit, the energy contained in the earth's crust will be sprayed out, and the rapid release of energy will bring violent vibration. This natural phenomenon is earthquake. When the earthquake occurred, the earth collapsed, the mountains collapsed, and the houses collapsed. At present, there is no completely effective means to predict the occurrence of earthquakes. Therefore, post earthquake rescue is particularly important

for rescue, finding and saving lives are the biggest goals. Science and technology have shown their great strength in rescue - as soon as all kinds of life detectors were invented, they went hand in hand with rescue dogs and played a great role. A series of life detectors such as infrared, audio, video, radar, electrostatic field, optics, gas sensitivity and so on are common. They have their own advantages and are suitable for different rescue conditions. In the actual rescue, several instruments often work together - first, the infrared detector determines the general orientation of the survivors, then the radar detector accurately locates them, and finally the optical detector is used to observe the surrounding environment of the survivors to determine the rescue plan. Among them, infrared detector has a long history and is one of the most commonly used life detectors

the infrared life detector relies on the difference between the infrared radiation of the human body and the environment to identify survivors, so it can be used in dark, smoke filled and other rescue places that are difficult for people to see. All objects above absolute zero will produce infrared radiation, and the human body is also a natural source of infrared radiation. Different from other objects in the environment, as a kind of constant temperature animal, the infrared wave band emitted by man is a special constant range. Finding the infrared within this range is very likely to find survivors, which is also the key point of infrared detector search and rescue. The core component of infrared life detector is infrared detector. Because of their different working principles, they are divided into two categories - thermoelectric detectors that use temperature differences and photoelectric detectors that rely on infrared wavelength differences. Thermoelectric detectors are often used to measure temperature, while infrared photoelectric detectors that can identify special bands are often used for life detection

photodetectors are electronic components that convert optical signals into electrical signals. There are two common types: photodiodes and photoresistors

the former is the same as the principle of solar cell power generation. Semiconductor materials absorb the energy of light and produce positive and negative charges that can be separated from each other. They are separated by the internal electric field of the material, and then pushed to both ends of the semiconductor, forming a potential difference. The potential difference is like the water level drop from high to low at both ends of the dam. Once the circuit is connected, the current will be like the water flow when the gate is opened for flood discharge, and it will be turbulent in an instant, thus forming a complete circuit, that is, an electrical signal; The latter usually has little conductivity when there is no light, and after being illuminated, it will only produce a large number of photogenerated carriers (basic units carrying charges). Unlike photodiodes, these charges usually have only one kind, which will generate positive or negative charges according to the type of semiconductor. They are like some stragglers who suddenly parachute down, and will only rotate around like headless flies. But when voltage is applied at both ends of the semiconductor, they rush forward in an orderly manner like hearing the horn of attack, making the current suddenly increase, and then converting the optical signal into an electrical signal

photoelectric detectors usually have differential responses to light of different wavelengths, so they can detect light of specific bands. There are two kinds of energy states of electrons in Semiconductors - conduction band and valence band. At low temperature, most electrons are in the valence band of low energy, which is very safe; Some electrons, like crazy children, become "little madmen" after being stimulated (such as light or temperature rise) and jump to the conduction band of high energy. At this time, they are more free and have conductivity. Therefore, semiconductors are named - the ground state conductivity is poor, and the conductivity is greatly improved after being stimulated. The energy gap is the energy difference between these two states, which determines how much stimulation can make an Fen. 7. The electrons of the accumulator become "Crazy". In general, the energy gap of a semiconductor is constant, and the energy of light depends on its wavelength. The energy gap corresponds to the light of a specific wavelength. Only the light with energy equal to or greater than this wavelength can convert light into electricity. After all, a large stimulus will only make electrons more "crazy". Therefore, if you want to detect infrared ray with very small energy, the energy gap of the selected semiconductor must be smaller, which makes the material selection of infrared photoelectric detector subject to great limitations. Because of this, at present, some scientists are improving the existing infrared response materials, while others are exploring new semiconductor materials, such as organic semiconductors with strong designability

infrared detection technology has been applied in all aspects of our life for a long time. For example, the remote controller of both air conditioner and TV emits information loaded on infrared ray, which is then converted into electrical signals by the infrared detector in the appliance, and then demodulated by the processor to realize remote control

in fact, this technology first emerged in the military industry, and its vigorous development also depended on the Second World War. Subsequently, infrared night vision helped soldiers clearly see the whereabouts of the enemy at night. The infrared precision guided weapons developed in recent years have led the war to a new level of "surgical" precision strike

therefore, infrared detection technology is not only paralyzed on the top left of the sofa, but also the main shaft drive system and the oil box with the remote control in hand. It is also a decisive tool for fighting for points in the disaster area (3) advanced basic materials to seize seconds to search for survivors, but also a preemptive trump card on the battlefield

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