The following are the uses of the laser:
(1) Laser communication  
Sending information by light is very common today. For example, the ship uses light communication, and the traffic lights use red, yellow and green colors. But all these ways of transmitting information by ordinary light can only be limited to a short distance. In order to transmit information directly to the far center through light, ordinary light cannot be used, and only lasers can be used.  
Where is laser communication improving the predecessors? The strength of laser communication is first of all a large capacity. How big is its capacity? When we usually call, we talk about sometimes irrelevant words. This kind of fight is because a pair of telephone lines can only pass one way. If another line comes in, the normal two parties will be interfered. Suppose there are 10 pairs of people talking on a pair of telephone lines at the same time, that is, 20 people talking at the same time, then basically can't talk. In order to solve this problem, it is necessary to adopt a carrier method, etc., so that each telephone is in each frequency band. Because the frequency range of ordinary telephones is 300-400 Hz, and the highest frequency on a pair of telephone lines is only 1500 kHz, only a dozen telephones can be simultaneously transmitted on a pair of telephone lines. Obviously, such telecom capacity is far from satisfying the demands of today's information society.
What is particularly surprising is that fiber optic communications are particularly well suited for the transmission of television, images and digital. According to reports, a pair of optical fibers can transmit a full set of Encyclopedia Britannica in one minute.
In addition, the material for making optical fibers is the sand that is found everywhere on the earth—quartz, which can produce 1 kilometer-long fiber with just a few grams of quartz. In this way, not only the original materials are inexhaustible, but also the copper and aluminum materials can be greatly saved. It is precisely because of this, the world's prosperous countries are competing to discuss laser communication. So laser communication became the darling of the competition.
In the history of communication technology, the rapid development of optical fiber communication technology is unprecedented. Taking a few milestones in the history of communication technology, the phone has been spent for about 60 years from creation to application, and telephone communication is still widely used and widely used. It took about 30 years for radio technology (such as telegraph) to go from creation to application. Although TV technology has developed rapidly, it has been bred for about 14 years. Laser communication, from the birth of the first low-loss optical fiber to the application, takes only a total of five years. Today, laser communication is not only common, but also constitutes a huge fiber market.
In short, the industrial booming countries have established a nationwide fiber-optic communication network to completely replace the current copper wire and cable. This mighty technical project is estimated to be completed by the year 2000. By then, laser communication will bring great changes to our planet. For example, if you are in a deeper position, you can use a fiber-optic network to dispose of files at home or get involved in a meeting; or connect your home's fiber-optic network to the shopping center. It seems to be in a supermarket, sitting at home and buying goods that you need, and you only need to pay for e-finance. Shopping system settlement. The medical center of each place can also view the patient's condition and laboratory lectures from the screen, and open the prescription form accordingly, so that the "show will not go out, you can know the world", "the operation is in the middle of the battle, and it is better than a thousand miles." outer".
Lasers and fiber optics are also capable of transmitting images. First, a single optical fiber having a diameter smaller than that of a human hair is combined into a fiber bundle. In the process of transmitting information, there are two types of fiber bundles commonly used: one is called a beam, and the other is called a beam. The task of transmitting a beam is to pass light from one end to the other. Compared with the simple configuration, the beam structure is glued together by a plurality of monofilaments, and then the end faces are polished and ground to reduce the reflection and scattering loss when the light enters the fiber, and then the plastic sheath is placed on the outside of the beam.
Because an optical fiber can only transmit one spot, to transmit the entire image, the optical fibers must be arranged one by one. The bundle of fibers is called a beam.
In the image bundle, all the fibers are arranged in a line, and the positions of the two ends are strictly corresponding one by one, which is not disordered, just like a uniform chopstick. For example, if one end of a fiber is in the eighth row and eighth column of the image bundle, then the other end of the fiber is also in the eight or eight positions.
When the image beam is transmitted, the image is first divided into a mesh shape, that is, an image is synthesized into an infinite number of pixels by an infinite number of fibers, and then transmitted. An optical fiber acts as a pixel, and an infinite number of fibers can transfer the entire image to the other end. If you want to make the image clear, you should use a fiber with a smaller diameter as much as possible, because the finer the fiber, the more beam can be contained in a certain image beam, so that more pixels can be transmitted. Obviously, the more pixels, the clearer the image.
Today's application bundle consists of tens of thousands of fibers, and it is not an easy task to arrange so many fibers one by one. After being arranged, the two ends are glued together with an organic binder called epoxy resin to bond the fibers to ensure that the fibers at both ends correspond one by one. The two end faces are also smoothed and polished. As for the middle part, it does not need to be glued, but it is as slack as the erhu's string. It only needs to be attached with a maintenance plastic sleeve. This kind of image beam is soft and can be bent.  
In addition to transmitting images, the image beam can also transmit ordinary symbols or numbers, as well as magnify or reduce the image.  
To enlarge the image, the image beam can be made one end large and one end small, just like a cone. When the image element is passed from the little end to the big end, the entire image is enlarged. Conversely, if the image is sent from the big end to the little end, the entire image is reduced.  
In addition, the application fiber can also modify the image. If the arrangement of the optical fiber is intentionally disturbed according to the demand, the exiting true pixel does not fall on the original corresponding point, but falls to the point of objective conceiving, and the image is changed. If the image element entrance is made into a square fiber and the exit end fiber is made into a circular shape, the square image element can be turned into a circular pixel.  
In short, the optical fiber image beam has great potential for development, and it will increasingly show its common role in future optical information processing technologies.  
(2) Data processing  
Drilling, cutting, welding, and quenching are the most common controls used to process metal materials. Since the introduction of the laser, a new scene has been created in terms of the strength, quality and range of processing. In addition to metal materials, lasers can process many non-metallic materials.  
Laser Drilling Machines Before the advent of laser drilling machines, drilling of various mechanical parts relied on electric drills or punching machines. However, mechanical drilling is not only inefficient, but the hole that is drilled is not bright enough.  
The principle of laser drilling is to apply laser beam collection to make the metal surface focus temperature rise rapidly, and the temperature rise can reach 10 million degrees per second. When the heat has not yet diverged, the beam burns the metal until it vaporizes, leaving a small hole. Laser drilling is not limited by the hardness and brittleness of the processing data, and the drilling speed is extremely fast, and it is fast enough to drill small holes in the order of a few thousandths of a second or even a few millionths of a second.  
For example, if you need to drill hundreds of micropores that are difficult to detect on the metal sheet, it is obviously incompetent to use an electric drill, but it can be used within 1 to 2 seconds with a laser drill. Completed. If you look at these micropores with a magnifying glass, you can see that the micropore surface is very bright.  
Laser drilling can also be used to process watch diamonds. It can drill 20 to 30 holes per second, which is several hundred times more efficient than machining, and has high quality. At the same time, laser drilling is the same as the laser cutting we will talk about below. The processing process is long and short contact type, that is, it does not drill through the metal data by steel drill bit like machining. Thus, laser manipulation can be performed in automated continuous processing or in a special environment of ultra-clean, vacuum.  
The laser cutting machine knows the principle of laser drilling, so it is easy to understand why the laser can cut metal data: just move the workpiece or move the laser beam so that the drilled holes are connected to the line, and the data can be cut naturally. Moreover, no matter what kind of information, such as steel plate, titanium plate, ceramic, quartz, rubber, plastic, leather, chemical fiber, wood, etc., the laser is like a handle to cut iron as a mud, cut wood as a gray lightsaber, and, cut The edges are very bright.  
The laser welder laser can be used for soldering because of its high power density. The so-called high power density means that extremely high energy can be concentrated per square centimeter of area. How high is the power density of the laser? We can compare it: the acetylene flame normally used in the factory can weld two steel plates together. The power density of this flame can reach 1000 watts per square centimeter; the power density of the argon arc welding equipment is even higher. Can reach 10,000 watts per square centimeter. But these two welding flames are basically incomparable with lasers because the power density of lasers is ten million times higher than them. This high power density not only welds ordinary metal materials, but also welds hard and brittle ceramics.  
The traditional quenching method of laser quenching is very simple. The blade is burned red and then immersed in cold water. Through this hot and cold treatment, the hardness of the blade is greatly improved. However, such quenching is obviously not very convenient, and the effect is not necessarily ideal.  
Laser quenching is the use of a laser to scan a part of a tool or part that requires quenching to increase the temperature of the scanned area, while the unscanned part remains at room temperature. Because the metal dissipates heat quickly, the laser beam just sweeps over and the temperature at this part falls sharply. The faster the temperature is lowered, the higher the hardness. If you spray the coolant on the scanned part, you can achieve much better hardness than ordinary quenching.
(3) Laser phototypesetting Photographic typography introduces the principle of optical photography. In typesetting, it is necessary to check the type of characters and fonts of different sizes and fonts according to the manuscript. There are a lot of phototypesettings. It is to change the size and shape of the typeface through the lens on the typesetting machine. As for why the size and shape of the typeface can be changed with a lens, in practice, we are taking a "haha mirror".  
In photocopying, it is only necessary to image the desired text and symbols on the photographic paper via a lens, and then develop and fix the photographic film. Then, just print as you would a photo.  
Phototypesetting can use two kinds of light sources, only to talk about ordinary light sources. In comparison, laser typesetting saves time and effort. Because the laser has high brightness and light color, it can greatly improve the clarity of the image, and the quality of the printed book is naturally high. What is the principle of it? First, the text is turned into a dot by a computer, and then the laser scanning photoreceptor is controlled by a dot to actually take a hologram.  
Holography and flat photography are two different things. Although the flat color photos look bright, clear, and flat, but it is always a single-sided image, no matter how good the plane can not replace the real thing. For example, a square photo of a square block, no matter how we change the viewing angle, we can only see the picture on the photo, but the hologram is different. We only need to change the viewing angle to see the square. Six aspects. Because holographic technology can record all the geometrical information of an object on a negative film, this is also the most important feature of holography.  
The second important feature of holography is that it can be seen in a panther. When the hologram is damaged, even if it is mostly damaged, we can still see the whole picture of the original object from the remaining half. This is not true for ordinary photos. Even if you lose a corner, the picture on the corner will not be visible.  
The third characteristic of holographic illumination is that multiple holograms can be layered on a single holographic film and do not interfere with each other as they appear. It is this hierarchical record that allows holograms to store large amounts of information. Laser holographic negatives can be special glass, latex, crystal or thermoplastic. A small special glass that can store the contents of millions of books in a large library. The use of holography is becoming more common.  
Holograms can record valuable historical relics. In the event that cultural relics are severely damaged, even if they are gone, we can still reconstruct them according to holograms. For example, the famous scenic spot like Beijing Yuanmingyuan was burned down by the Eight-Power Allied Forces. Now, although it is planned to be rebuilt, it is difficult to recover completely because it does not know the original appearance. If holograms were created 100 years earlier, things would be easier.  
Holography can also be used as non-destructive testing in the industry. What is nondestructive testing? That is to say, laser holography can check whether raw products have minor defects and do not damage these products at all. Even more interesting is that holograms are currently used to capture holograms and televisions, and soon viewers will see images of real life. That is, the laser "collision" hits the photographic paint on the negative film, leaving a countless corresponding points, which are developed and fixed to become text or images. Here, the laser beam is commensurate with the electron beam, and the photographic film is commensurate with the television screen. Next, you can print magazines and magazines with negatives containing text and images. The reason why color TV sets can display red, green and blue colors is because the screen is coated with three-color phosphors, which will show three colors under the impact of electrons. Laser phototypesetting can also use a similar principle to print beautiful color images.
(4) The application of laser in medicine The application of laser in the field of medical equipment is many, it can play various roles such as drill bit, scalpel and welding torch.  
Welding torches and drill bits in ophthalmology, lasers are mainly used to treat retinal detachment. Retinal detachment is a very difficult disease, and the patient's retina is disengaged from the inner wall of the eyeball and cannot produce vision. Before the laser was released, the patient was afraid of a blind disaster.  
Today, doctors can use a laser to align the patient's fundus, causing the laser to emit a laser that reheats the retina to the inner wall of the eye. The whole process took a few minutes, and the laser beam, like a welding torch, welded the patient's retina.  
In addition to welding, the laser can also be used for cutting.  
Cataract is a common disease in the elderly. The convex lens at the front of the patient's eyeball - the lens, gradually becomes turbid and inelastic by the original transparent elastic body, the light can not pass through the lens, and falls to the retina of the fundus, and the patient gradually cannot see anything. The traditional method of treating cataracts is to cut a hole in the front of the eyeball and then insert a thin metal needle from the small mouth. The metal needle has a very low temperature, and the opaque lens is frozen and adhered to the needle, and then taken out from the small mouth. Obviously, the whole operation is laborious.  
If you use medical lasers for treatment, it is not only convenient, but also effective. Simply aiming the laser beam at the anterior or posterior surface of the lens inside the eyeball can quickly remove the chaotic membrane of the crystalline external surface.  
In dentistry, the laser is able to replace the dental drill. According to the World Health Organization, the incidence of dental caries in children is relatively high, reaching approximately 75%. With a laser to treat the teeth, the patient does not feel uneasy, and only needs to be inflamed, and the treatment can deal with the problem. The dental laser is a small brother in the laser. Its power is very small, as long as 3 watts, commensurate with an energy-saving lamp, it does not generate heat. Its launch end is actually a thin fiber like a hair.  
During treatment, it is only necessary to bring the fiber-emitting end close to the dental caries, emit a laser beam, and the tissue will be synthesized and then washed away with clean water. If the cavities are only damaged by the shallow gums, the laser beam will seal the tiny pores in the lesion one by one, thus preventing the lactate from eroding the dentin. If the pupil has been presented, after drilling and cleaning with a laser beam, the artificial enamel data can be filled into the air, and then the laser is used to heat the joint to integrate the artificial enamel data with the gum. Laser treatment is not only painless, rapid, but also effective after treatment.  
Laser scalpels are difficult to use if they use a laser knife to enter the patient's bladder, heart, liver, stomach, intestines and other important internal organs. How can the laser enter the human internal organs? This depends on a magic weapon in the hands of the doctor. This magic weapon is a laser fiber endoscope.  
The so-called endoscope is an optical installation that the doctor uses to insert the human body and directly view the organ. However, the volume of the endoscope is usually larger than that of the endoscope, and it can only be inserted from the patient's mouth along the esophagus into the stomach. It is often difficult to get sick of the stomach, and the patient will feel very painful. Laser fiberscopes are completely different. An endoscope made of optical fiber is soft, thin, and bendable, and it does not suffer when it is inserted into the patient's stomach. In addition to the stomach, fiberscopes can also enter other important organs. On the one hand, the laser fiber endoscope can be used to check whether the patient's organs can have lesions, and more importantly, the laser energy can be input into the internal organs, and the diseased tissue can be stopped, which is also removed, and the scalpel is used. . Moreover, with a laser knife, the wound can automatically stop bleeding, no need to ligature the bleeding point, greatly shortening the operation time, and the wound will not be inflamed. If you use a laser knife to remove malignant tumors, you can also avoid the spread of cancer cells.
(5) Laser weapons  
In the Gulf Campaign, the US-led multinational force launched a large-scale air strike against Iraq and destroyed many important military objectives of Iraq. In the end, the battle ended in Iraq’s failure. Some people say that the Gulf Campaign is a game to improve the weapons of the predecessors, which makes sense.  
The US aircraft is equipped with a laser sight that emits an infrared laser. When an aircraft that is a reconnaissance mission finds aerial targets in the air, it whirls in the air and uses a laser sight to launch a laser beam from time to time. This laser beam actually acts as a guide. At this time, other aircraft serving as missions then flew in and dropped laser-guided missiles at the destination. These laser guided missiles are equipped with an automatic tracking system. This automatic tracking system is the eye of the missile. When the missile is thrown at the target, it can correct the heading in flight according to the guided laser light reflected from the purpose, so as to hit the target accurately.  
In fact, such laser-guided missiles were used in the battlefields of Vietnam in the 1970s. Today, there are not only air-to-ground missiles, but also a variety of laser missiles, such as ground-to-ground, air-to-air, and ground-to-air.  
Today, people have been able to separate radio search radars and laser radars into a combat system. For example, when a radio radar finds an air destination (enemy or missile), it can accurately measure the height, azimuth, and speed of the destination. As long as the purpose is within a certain range, the laser radar will be turned on, and a very fine laser beam will be emitted, and the position of the target will be firmly fixed and correctly measured. Then the laser missile launched will be guided by the laser provided by the laser radar. Bunch, precisely hit the purpose and destroy it. These laser missiles can be deployed locally on trucks and can be converted into anti-tank missiles.  
The anti-tank laser missiles currently being developed can be launched from the air as well as from helicopters. The missile is equipped with a semiconductor laser, which plays the role of automatic tracking, so that the missile can hit the tank in every possible way.  
Although the laser radar has high precision, small size, good control, and convenient transfer, it also has defects, which are easily restricted by the weather premise, and is not suitable for searching in a wide range. Therefore, it is generally used in conjunction with radio radars to foster mutual strengths and avoid weaknesses.  
Laser guns and laser guns The so-called laser guns and laser guns are all laser tactical weapons. They are shaped like guns and cannons, but they don't fire bullets and shells, but laser beams that cause enemy workers to die or become blind. The ability of such guns is related to their energy and shooting distance. Nowadays, the effective range of laser guns and laser guns is not far away, so the ability to die light is limited, and the future development space is still quite large.
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