The so-called holography is to use laser technology for photography to record all the light information of the object on the film, unlike ordinary photography that only records the projection of a certain side of the object. Therefore, when the object on the film is When the body is reproduced, it appears extremely lifelike in the eyes of the viewer, and the visual effect it produces is exactly the same as when viewing the real object.

The principle of holography, simply put, mainly takes advantage of the characteristic of pure color of laser .In fact, the theory of holography was proposed by the British scientist Gabo as early as 1947. However, it was not until the advent of lasers with high brightness, pure color, and good coherence that holograms were actually taken.

Holography and stereoscopic photography are two different things. Although the stereoscopic color photo looks bright, clear-cut, and full of three-dimensionality, it is still a single-sided image. No matter how good the stereoscopic photo is, it cannot replace the real object. For example, a square For a three-dimensional photo of a wooden block, no matter how we change the viewing angle, looking horizontally or vertically, we can only see the picture in the photo. But the hologram is different. As long as we change the viewing angle, we can see the exact picture. Six aspects of the cube. Because holographic technology can record all geometric feature information of an object on the film, this is also the most important feature of holography.

The second feature of holography is that it can The whole picture can be seen at a glance. When the hologram is damaged, even if most of it is damaged, we can still see the full picture of the original object in the hologram from the remaining half. This is not possible with ordinary photos. , even if one corner is lost, the picture on that corner will no longer be visible.

The third feature of holograms is that multiple holograms can be recorded in layers on one holographic film. And they will not interfere with each other when they display the picture. It is this kind of layered recording that enables holographic photos to store a huge amount of information.

Why do holographic photos have such characteristics? Why do ordinary photos not? What about these characteristics? This starts with the principle of photography.

Suppose a laser beam is used to illuminate a tiny particle. The light wave reflected from the small particle is basically a spherical wave that continues to expand outward. We Small particles appear to be bright spots. When you take a picture of a small particle with a camera, the light wave passes through the lens to form a bright spot on the film. The brightness of this point is related to the intensity of the light reflected by the small particle. The photographic film can record this. The bright spot, but the position of the small particles in the three-dimensional space cannot be remembered, and there is only one bright spot on the printed photo. It does not seem to have any three-dimensional feeling. When taking a holographic photo, a camera lens is not used, but a beam of laser light emitting plane waves and The spherical waves reflected by the small particles hit the photographic film together. The entire film is illuminated, and what it records is not a bright spot, but a group of concentric circles. When the intervals between the concentric circles are very small, it looks like a knife handle. A round radish is cut into thin slices and stacked together to form a set of concentric rings. After the film is developed, it is placed in its original position, and then the laser beam that emits plane waves is used to illuminate the film at the same angle as when shooting. , we can see a bright spot where the tiny particles were originally placed. Pay attention! This bright spot is in space, not on the film, and the light we see seems to be emitted from this bright spot. Therefore, the holographic photo records It is not only a bright spot, but also the spatial position of the bright spot, or the entire light wave emitted from the bright spot. The whole secret lies in this novel shooting method, which lies in this parallel (plane wave) laser beam. This laser beam , we call it the reference beam.

Therefore, any object can actually be seen as a three-dimensional image composed of countless bright spots with different light and dark colors. The holographic photos taken using the above shooting method are countless The complex figure composed of concentric circles also looks dark. Similarly, this holographic photo not only records the light and dark of each point of the object, but also records the spatial position of each point. When the reference beam is used to illuminate the developed film, The light we see seems to be emitted from the original object. Therefore, we say that it records all the light information emitted by the object, which is why the name of the hologram comes. However, the laser hologram can only be illuminated by the laser. Only under the eyes can the three-dimensional image be seen, and the laser is a relatively expensive equipment. One photo needs to be equipped with a laser. Except for the possibility of setting it up in scientific research departments and specialized places, it must be widely and widely used. It is impossible. To address this shortcoming, scientists have continued to study and finally

Invented a holographic photo that can see holographic scenes under incandescent light. It is called white light holography or rainbow holography.

The negative of the laser hologram can be special glass, latex, or crystal Or thermoplastic, etc. A small piece of special glass can store all the contents of millions of books in a large library.

If you pay attention to the photos in the newspaper, you can find that they are made of It is composed of small dots. Each small dot is called a pixel, and its density is approximately a few dots per square millimeter. The special glass film used for holography is about 10 microns thick, and the dot density is approximately 10 microns per square millimeter. More than 2000 dots. On this kind of film, a large photo of 310 square centimeters can be placed in every square millimeter. A 200-page thick book can be placed on a small piece of 5 mm square film. Books.

The main significance of the invention of the holographic camera is not photography. As an aspect of laser technology, it has extensive practical value in industry, agriculture, scientific research and other fields.

From In terms of photography, this is a brand-new technology. Because holographic photos have a realistic three-dimensional effect, using them to replace ordinary photos has a unique effect. In foreign countries, some people have used holographic photos to make book inserts and trademarks. Create three-dimensional advertisements; museums use them to replace precious cultural relics for display. A foreign machine tool manufacturing company went to another country to hold a product introduction meeting, and used holographic photos instead of real objects to hold a machine tool exhibition. The exhibition hall was full of various products. Holographic photos of machine tools. These holographic photos look no different from real machine tools, but instead arouse the interest of visitors.

The well-conceived holographic photos are also exquisite works of art. United States Countries such as China and France have holographic photo museums, which collect the most exquisite works in the world.

Holograms can also record precious historical relics. If any cultural relics are seriously damaged, even if they are gone, If nothing exists, we can still reconstruct it based on holograms. For example, famous places like the Old Summer Palace in Beijing were burned down by the Eight-Power Allied Forces. Although they plan to rebuild them now, it is difficult to fully restore them because they don’t know the entire appearance. If holograms had been invented 100 years earlier, Things will be easy to handle.

Inspired by holographic photos of three-dimensional scenes, scientists thought of holographic movies and holographic TVs. Experimental holographic three-dimensional movies have already appeared in the former Soviet Union. When such movies are shown, the audience The scene you see is not on the screen, but in the audience, giving people a real and immersive feeling. As for holographic TV, because the technical issues involved are relatively complex, it is still being studied. In 1982, Germany The three-dimensional TV broadcast by the TV station is not a laser holographic TV. Its principle is the same as that of ordinary three-dimensional movies. You need to wear a pair of special glasses when watching it. It is expected that by the end of this century, movies and TV will have to be replaced again; by then, people's Cultural and entertainment life may become more colorful due to the emergence of laser panoramic stereoscopic movies and laser stereoscopic TV.

Another important application of holography is the production of holograms that can replace glass on some special occasions. Optical elements. This special optical element has the advantages of easy processing, compactness, lightness, and thinness. A concave lens can make the light beam diverge, and a parallel light wave shines up and turns into a spherical wave; the hologram shot with small particles we talked about earlier The photo will also turn the parallel light reference beam into a spherical wave; such a holographic photo is a special concave lens. Using a similar method, optical components such as convex lenses and cylindrical lenses can be made. Such components are as thin and light as paper. , and it will not break. There are now telescopes made of holographic optical elements, which are about the same thickness as ordinary myopia lenses. Some people have also reported using holographic optical elements to make window glass. This kind of strange window glass will not affect people's sight. , but it can reflect a large amount of sunlight and function as a curtain; more interestingly, the sunlight reflected by it can be concentrated on a row of solar cells installed under the window eaves, and converted into electrical energy for indoor use. It really kills three birds with one stone. Got.

Hologram technology has the ability to see clearly. Because holograms can accurately reproduce the original photographed object, we can use it as a standard to check whether the original object has changed; in fact, as long as there are 1 micron Changes can be detected using holographic technology. The scientific research and production department also uses laser holography to serve as the "inspector" of the intrinsic quality of the finished product. During inspection, a little pressure or heat is added to the inspected object; if there is something inside the object Cracks and micropores will cause corresponding changes in its surface.

Although the degree of this change is extremely subtle and cannot be detected by the naked eye, under the "fiery eyes" of holography, all these flaws and hidden dangers are fully exposed. In addition to accurately inspecting the internal quality, this method also has the ability to The advantage of the inspection object is that it is not damaged at all, which is especially suitable for the detection of valuable items, such as precious cultural relics and ancient sculptures. Greek scientists once used this method to detect the degree of weathering of ancient statues. This method is used in production to inspect precision parts. , aircraft skins, and the intrinsic quality of aircraft tires. In foreign aircraft tire factories, laser holography "inspectors" have been used. This method is also used for biological research, such as studying the vibrations produced when the brain is subjected to force. Deformation, studying the growth rate of mushrooms, etc.

What is still under development is holographic storage technology. The information storage we mentioned when talking about the characteristics of holography is the ability to record information. Theoretically, when using optical discs to store information, the information that can be stored per square centimeter is about 106 bits, while using holographic storage, it can store 108 bits per square centimeter, which is 100 times higher! And the time to read out the information is only a hundred times. Ten thousandths of a second!

Now, it is possible to store information in materials. The material used for holography is not a thin layer of film, but a whole crystal that can store 100,000 books. One The library only needs to store a few recording crystals. This seems a bit fantasy, but it is promising. More importantly, the development of holographic storage will promote the development and replacement of computers.

General holographic photos can only be produced one by one, and the price is also very high; apart from being used in scientific research, they can only be used as high-end works of art. In the 1980s, a new imprinting holographic technology appeared. To make holograms in this way, you first need to make a metal micro-relief plate; use it as a printing plate to press out holograms on special paper coated with a metal film. This is more convenient than printing stamps and can be mass-produced , the cost is greatly reduced, and the application scope is becoming wider and wider.

This kind of holography not only has a three-dimensional sense; it shows a variety of colors under sunlight or light, and appears more vivid when set against a silver-white metal background. It is very gorgeous. People use it to decorate books, toys, and travel souvenirs. It is very charming.

This kind of hologram also contains a wealth of information, and it completely depends on the scenery and shooting method used in the production. It is like adding a password. Without the original printing plate, it cannot be copied. Therefore, it has become an effective means to prevent forgery. Various holographic marks have appeared on banknotes, credit cards, magnetic cards and diplomatic visas to prevent forgery. In our country, Many manufacturers have also adopted holographic trademarks to prevent people from forging trademarks and deceiving customers.

It is worth mentioning that holography, a major technological achievement, has nothing to do with ordinary photography. Invented in the field of scientific research. The purpose of the inventor Garber's research on this subject was to improve the resolution of electron microscopes. He designed this new imaging method and published it in a scientific magazine in 1948. However, at that time, There was no monochromatic light as good as laser, and there were some technical difficulties. Garber did not achieve results, and no one paid attention to his paper.

It was not until more than ten years later, in 1964, because of the emergence of lasers With this ideal light source, holography technology began to develop. Soon, holography became a new technology with a wide range of uses and unlimited development potential. Garber won the 1971 Nobel Prize for pioneering the theory of holography. Bell Prize in Physics. As a result, he was recognized by the world as the "Father of Holography".