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Hologram Introduce and its Application
What's Holography
Holography also known as: "hologram", a use of wave interference records are subject reflection (or transmission) light wave (amplitude and phase) of the photographic technology. Holography is a bunch of reference light and the subject of the light reflected on the object superimposed on the interference fringes formed on the photosensitive sheet. Holography only records the amplitude (intensity) of the subject is reflected lightwave, but also record the relative phase of the reflected lightwave photography, also known as: "hologram", a wave interference record is subject reflective (or transmissive) lightwave information (amplitude, phase) of photographic technology. Holography is a bunch of reference light and the subject of the light reflected on the object superimposed on the interference fringes formed on the photosensitive sheet. Holography only records the amplitude (intensity) of the subject is reflected lightwave, but also record the relative phase of the reflected lightwave
Principle
Holography refers to a new photographic technique of recording all the information of the subject is the amplitude and phase of the reflected wave.
The ordinary photography is the recording surface of the object light intensity distribution, it can not record the phase information of the object of the reflected light, thus losing the three-dimensional sense.
Lighting source
Holography using a laser as a light source, and light from the source is divided into two beams, a bunch directly directed to the photosensitive sheet, another bunch reflection object and then directed to the photosensitive sheet. The two light beams on the photosensitive sheet superposed interference the photosensitive extent of each point on the photosensitive film is not only with the intensity with the phase relationship of the two light beams with different. Holography not only records the reflective intensity on the object, the phase information is also recorded. The human eye to see this photosensitive film directly, only to see the fringes like fingerprints, but if it is irradiated with laser, the human eye through the negatives can see the original shooting identical three-dimensional objects like
Laser holography consists of two steps: recording and reproduction.
Holography records
Dividing the laser beam into two beams; laser beam projected directly on the photosensitive film, known as the reference beam; another bunch of laser light projected on the object, the object as reflection or transmission to carry relevant information of the object, known as the object beam. The object beam is also projected treated in the same region of the photosensitive film. coherent superposition occurs in the photosensitive film on the object beam and the reference beam, the formation of interference fringes, which completed a hologram.
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Hologram photography reproduction
The hologram is irradiated with a laser beam, the frequency and transmission direction of the laser beams should be exactly the same as with the reference beam, so they can be reproduced by the stereoscopic image of the object. People look from different angles, you can see the different sides of the object, as if to see real objects, and just a touch less than the real object.
Holographic imaging is cutting-edge technology, holographic and conventional photographic plane image recorded on the film is not three-dimensional objects, but the light field. The conventional photographic records only the reflected beat changes in light intensity of the surface, i.e. only the amplitude of the recording light, the hologram is recorded all the information of the lightwave also recorded, unless the amplitude of the outer the FIG phase of the lightwave. I.e. the lightwave field of the three-dimensional object all of the information stored in the recording medium.
Hologram principle
The holographic principle is "a system in principle, it borders on the number of degrees of freedom to fully describe" a new basic principles based on the quantum nature of the black hole. In fact, the basic principle is to contact quantum yuan combination of quantum theory and quantum bit. Mathematical proof, how many dimensional space-time, there are that many quantum yuan; how many quantum yuan, there is the number of quantum bits. Together they form the matrix-like space-time finite set, that is, the set of permutations. Hologram incomplete, said selected number of permutations Select an empty set with the election of the full array duality. Certain dimension of space-time holographic completely equivalent to less number of permutations of a quantum bit hologram; This is similar to the "quantum error avoiding coding theory, a fundamental solution to the system of of encoding quantum computing error calculation error problem. The time and space of the quantum computation, double conjugate coding of the the similar biological DNA double helix structure, it is real and imaginary, positive and negative double conjugate the coding organization together quantum computer. This can be called the "biological space-time learning", which "entropy", similar to "macro entropy" not only refers to the degree of disorder, but also refers to a range.
Differences and characteristics of holographic photography and photography
Difference
Records only in the ordinary photography, the scene captured by the camera, the intensity of reflected light of the scene, that is, the amplitude of the reflected light information, while the three-dimensional information can not record the scene. Holography technology, capable of recording the amplitude and phase of the reflected light in the scene. Shooting holographic images recorded the lightwave itself as well as two beams relative phase, phase is caused by the difference in kind between the reference light position.
We see the imaging of the object, you must use a cohesive laser to accurately aim at the target irradiation hologram to reproduce all the information of the object light from the interference fringes on the hologram. Benton later found easier to use white restore image, so that this technology is gradually moving towards the practical stage.
Significant features
The three-dimensional image of a recycling out of favor the preservation of precious art data collection.
b, when shooting each point are recorded in any point of the hologram sheet, once photo damage little relationship.
c scene three-dimensional holographic photo realistic image with the laser can be displayed in a variety of exhibitions, will get very good results.
Holographic shooting requirements
The shooting system must meet the following requirements in order to shoot a satisfactory holographic photo
The light source must be coherent light source
Holography is based on the principle of interference of light, so they requested that the light source must have good coherence know by the previous analysis. The emergence of the laser light for the hologram of an ideal light source. This is good because the laser coherence, He-Ne laser used in the experiment, with its shooting small diffuse object, get a good spatial coherence and time of the hologram.
Hologram system stability
Since the hologram recorded on the interference fringe, and is a thin, dense, interference fringes, minimal interference will cause the blurring of interference fringes in the photographic process, and even the interference fringes can not be recorded. Example, shooting film displacement of a micron, the stripes on a confusion, the holographic experiment station is shockproof. Table holographic optics magnetic firmly sucked on countertops steel. Further, the airflow through the optical path, the acoustic interference, and temperature changes will cause changes in the density of the surrounding air. Therefore, the exposure should prohibit loud noises, can not move around freely, the entire lab absolute quiet. Our experience is that each group tuned optical path, the students left the bench stable after a minute, and then came to light at the same time, to get a better effect.
Object light and reference light should meet
Object light and reference light, an optical path difference should be as small as possible, preferably equal to the optical path of the two beams of light, up to not more than 2cm, adjusting the optical path with twine amount; the angle between the two light beams at 30 ° ~ 60 °, preferably at about 45 °, because the angle is small, interference fringes on the thin, so that the lower the resolution requirements of the system stability and the photosensitive material; two light beams of the light intensity ratio should be appropriate, generally requires can be between 1:1 to 1:10, the light intensity ratio measured with a silicon photovoltaic cell out.
Using high-resolution hologram
Because recorded on the hologram backsheet is a thin, dense interference fringes, so the photosensitive material requires high-resolution. Ordinary camera used in photographic film due to coarse particles of silver compounds can record only 50 ~ 100 stripes per millimeter, the photosensitive film Tianjin plant production of I-type hologram dry plate, with a resolution of up to 3000 per mm, can meet the holographic photographic requirements.
Holographic photo of flushing process
The flushing process is also very critical. We follow the recipe requires dispensing with the developer, stop bath and fixer and bleach solution. The above several prescriptions are required to use distilled water, but the experiment proved successful with pure water preparation. The flushing process in the darkroom, liquid must not see the light, and kept at room temperature about 20 ° C to wash formulated liquid custody properly about a month.
Application of holography everyday life and special occasions
Holography technology use in life.
On some credit cards and banknotes, there is the use of a full-color holographic image technology invented in the 1960s, the Russian physicist Yuri Danny Suker (Yuri Denisyuk) the soft polyester film production on rainbow "holographic image. But these holographic image is more just as a complex printing technology to achieve security purposes, their low sensitivity, color is also not enough realistic, far less to the realm of spurious.
 
Filmed some precious relics of this technology, when it was exhibited true stereo reproduction artifacts for visitors to enjoy, while the original is properly preserved, anti-theft the the large hologram can show cars, satellites and a variety of three-dimensional advertising , we can use pulse holography reproduction portraits, wedding photos. The small hologram can be worn on the neck, forming a beautiful decorative it reproducible favorite animal, colorful flowers and butterflies. Rapid development of molded rainbow hologram, can become vivid cartoons, greeting cards, three-dimensional stamp, also can be used as anti-counterfeit labels appear in the trademark documents cards, bank credit cards, and even banknotes.
  
Embossed hologram logo rainbow effect due to its three-dimensional sense of depth, and changes with the viewing angle, as well as the ever-changing security tag, plus closely integrated with other high-tech security means the security technology of the new century to a new brilliant vertices.
In summary, the holographic a video without ordinary optical imaging system, the sixties developed a three-dimensional photography and wavefront reproduction of new technologies. Hologram able to record all the information issued by the surface (ie, the amplitude and phase of the light wave) and reproduction subject to all the information of the object light waves, holographic technology in production practices and scientific research in the field has a wide range of applications . For example: the holographic film and holographic television, holographic storage, holographic display and holographic anti-counterfeit trademark.
   
Special occasions to use
In addition to optical holography, the development of infrared, microwave and ultrasonic holographic technology, holographic technology is important in military reconnaissance and surveillance. We know that the general radar can only detect the target orientation, distance, etc., and the hologram is able to give the three-dimensional image of the target, which plays a significant role for the timely identification of aircraft, ships and other. Therefore, much attention. However, due to the attenuation of visible light propagation in the atmosphere or water quickly in adverse climate and even unable to work. For the infrared, microwave and ultrasonic holographic techniques developed to overcome this difficulty, i.e. coherent infrared light, microwave and ultrasonic shooting hologram reproducing images, and then with visible light, the same principle of this holographic technology with ordinary holography. The key to the technology is to find sensitive recording medium and suitable method of reproduction.
  
Ultrasonic holography reproduction lurking in the three-dimensional pattern of underwater objects, and therefore can be used to conduct underwater surveillance and reconnaissance. Visible opaque objects, often transparent to ultrasonic, ultrasonic holography can be used for underwater military operations, and can also be used for medical perspective as well as the industrial NDT measurements.
In addition to the lightwave generated hologram has been developed to the available computer generated hologram. The hologram is very versatile and can be made of a variety of thin-film optical components such as lenses, gratings, filters, can overlap in space, is very compact, lightweight, suitable for space flight use. Use hologram storage of data, with a large capacity, easy to extract, anti-fouling, etc..
   
The holographic methods from the field of optics extended to other areas. Microwave holography, acoustic holography been greatly developed and successfully applied in industrial and medical aspects. Seismic wave, the electron wave, X-ray, and other aspects of the hologram is also in-depth study. The hologram has an extremely wide range of applications. As used in the study of the shock wave of rocket flight, non-destructive inspection of the aircraft wing cellular structure. Now not only laser holography, and research the successful white holographic rainbow hologram, and panoramic rainbow hologram, so that people can see each side of the scene. Holographic three-dimensional display is the direction of the development of holographic color stereoscopic television and movies.
    
The hologram unlike ordinary camera photography. Ordinary camera when the light emitted by objects or surface emitting and light refracted through the imaging lens , the light intensity recorded on the photosensitive film , showing a plane image of the object in the photographic paper . The hologram is a lensless imaging method , he used - amplitude and phase of all the information of the subject , so called hologram recorded in the hologram dry plate of the light interference principle . Hologram reproduction , see the objects are three-dimensional and vivid image .
Currently, hologram interferometry , information storage , optical information processing , non-destructive testing , stereoscopic display , the field of biology, medicine , and defense-related research has been quite widely used .
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