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[Concept]
Records are subject reflection (transmission) light waves in the photography of all of the information (amplitude, phase).
"Holographic" a wave interference record the subject is reflected (or transmitted) light waves (amplitude, phase), photography.
Holography to produce interference fringes from light being shot by a bunch of reference light reflected on the object superimposed on the sensitive film.
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[Calendar history]
The hologram (Hologram) is to cover Bo (Gabor) in 1948 in order to improve the resolving power of electron microscopy, proposed the concept of the hologram, and begin the research work of the hologram.
1960 laser holography provides a high-brightness highly coherent light source, then on holographic technology into a new phase.
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The original rationale
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[Introduction]
Holography refers to a record subject the reflected wave amplitude and phase information of the new photographic technique.
Ordinary photography is the light intensity distribution of the recorded object surface, it can not record the phase information of the object reflected light, thus losing the three-dimensional sense.
Laser holography is a new technology, it was hailed as a miracle of the 20th century.
Its principles in 1947 by Dennis Gabor, British physicist of Hungarian nationality, it is completely different to the ordinary principles of photography.
Until 10 years later, after the American physicist Ralph in Pat Nyx invention, the laser holography to practical application.
It can be said that the holographic information storage and laser technology product.
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[Lighting]
Holography using laser as a light source and light source emitted light into two beams, a bunch of fired directly at the sensitive film, the other a bunch of has been the subject of reflection and then fired at the sensitive film.
Two beams of light sensitive film on the superposition of interference, the photosensitive film on the photosensitive not only with strength but also with the phase relationship of the two beams of light. Holography not only records the reflection intensity on the object, but also record the phase information.
Directly to the human eye to see this light-sensitive film, only to see the same as the fingerprint of interference fringes, but if the laser irradiation, the human eye through the film will be able to see the original object being photographed identical three-dimensional like .
A holographic photography have only a small part, can still reproduce all the scenery.
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Laser holography steps]
A. The holographic recording process is divided into two beams: the laser beam;
Direct projection of the laser beam on a photosensitive film, called the reference beam;
The laser beam projected onto the object, the object of reflection or transmission, carry information about objects, called the object beam.
The object beam is also projected treated in the same area on the photosensitive film on a photosensitive film, the object beam and reference beam coherent superposition of the formation of interference fringes, which completed a hologram.
Two. Holography is:
The hologram of the laser beam irradiation, laser frequency and the transmission direction and the reference beam should be exactly the same, so they can reproduce the three-dimensional image of the object.
People can see a different side of an object viewed from different perspectives, like to see real objects only touch less than the real object.
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[Holography and photography difference]
Is a cutting-edge holographic imaging, holography and conventional photography, plane image recorded on the film is not a three-dimensional objects, but the light field itself.
Conventional camera only records reflect was shot in the surface light intensity changes, that is, only records the amplitude of the light, holography is to record all the information of the light waves, also recorded in addition to the amplitude of light waves of Figure phase. That all the information of the light waves of three-dimensional objects are stored in the recording medium.
From the interference fringes on the hologram, we see less than the imaging of objects, must use the the cohesive laser to accurately aim at the target exposure holographic film, in order to reproduce all the information of the object light.
Called the people of Benton and later found it easier to use white light to restore image, so that this technology is gradually heading towards the practical stage.
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【Shooting requirement】
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(1) light source must be a coherent light source]
Know through the above analysis, the hologram is based on the principle of interference of light, so they requested that the light source must have a good coherence.
The emergence of laser, holographic an ideal light source.
This is because the laser has good spatial coherence and temporal coherence, He-Ne laser used in the experiment, a small diffuse object with its shooting, get a good hologram.
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(2) the holographic system is stable
Interference fringes is recorded on the holographic film, and thin, dense interference fringes, so minimal interference in the photographic process will cause interference fringes blurred, and even the interference fringes can not be recorded.
For example, in the process of shooting the film displacement a micron, the stripes on a confusion, that required the holographic bench is shock.
Holographic stage all optical devices using magnetic materials firmly smoke on the work surface plate.
In addition, the airflow through the optical path, the interference of sound and temperature change will cause changes in the ambient air density.
Therefore, exposure should be banned are noisy, can not walk around to ensure that the laboratory is absolutely quiet.
Our experience is that each group adjusted the light path, the students leave the laboratory bench, stable one minute, then came to light in the same time, get a better effect.
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(3) the object light and reference light should be met]
Things light and reference light optical path difference should be small, two-beam optical path equal to the best, a maximum of 2cm, string a good amount of dimming Road;
The angle between the two beams of light between 30 ° to 60 °, preferably about 45 °, because the angle is small, interference fringes on thin, so that the stability of the system and the photosensitive material resolution than the low;
The two beams of light intensity should be appropriate, generally between 1:1 to 1:10, the light intensity measured a silicon photocell.
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(4) using high-resolution holographic film]
Recorded on the holographic film is thin, dense interference fringes, so they need high-resolution photographic materials.
Ordinary photographic photosensitive film due to the coarse particles of silver compounds, can only record 50 to 100 per mm stripes
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(5) [holographic photo flushing process]
The flushing process is also critical.
We follow the recipe calls for dispensing with the developer, stop video solution, fixer and bleach solution.
These prescriptions are prepared with distilled water, but experiments show that, using pure water preparation, but also succeed.
The flushing process in the darkroom, the liquid should never see the light, kept at room temperature 20 ° C wash in the right, the preparation of a liquid custody properly can be a month or so.
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[Features advantage
A. Recycling out of the three-dimensional image to save the precious works of art data collection.
Two. Every point of the shooting recorded on any point of the holographic film, Once the photo damage.
3. Holographic photo of the scene dimensional sense of strong, vivid, with the laser in a variety of exhibitions on display will get very good results.
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【Article is excerpted from: Baidu Encyclopedia】
【Network reprint / Just reference】
【Translation is by Goolge】
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