Holography can be used for optical storage, reproduction and information processing. Although holography has been widely used to display static three-dimensional images, it is still impossible to display objects arbitrarily by using three-dimensional volume holography.
Holography was first discovered by Hungarian physicist dennis gabor (1900- 1979) in 1947, and197/kloc-0 won the Nobel Prize in physics. Other physicists have also done a lot of pioneering work, such as Mieczyslaw Wolfke solving the previous technical problems and making optimization possible. In fact, this discovery is a casual product of a British company in the process of improving the electron microscope (patent number GB685286). This technology was originally called "electronic hologram" because it was still using electron microscope at the beginning. As a hologram in the optical field, it was not until the invention of laser technology in 1960. The first hologram recording a three-dimensional object was taken by Yuri Denisuke, emmett Liss and Yuri Upatneks in the United States on 1962.
There are many kinds of holograms, such as projection holograms, reflection holograms and rainbow holograms.
Ordinary photography can only record the light field intensity (the square of complex amplitude mode) of an object, and cannot represent all the information of the object. Using holographic method, the intensity of light field is also recorded, but that is the intensity after the interference of reference light and object light. For the light intensity recorded by this method (in crystal or holographic film), when reproduced with reference light, the object light recovery amplitude can be expressed completely representing the object information.
The manufacturing process is as follows.
A beam of coherent light (whose frequency is strictly consistent, which can produce obvious interference) is split by 1: 1, and the beam irradiated on the object is called object light, and the other beam is called reference light. When the optical path (the distance of light propagation) is almost the same, the object light reflected on the object and the reference light interfere on the crystal (or holographic negative).
When observing, the original three-dimensional object can be observed on the holographic negative as long as it is irradiated with reference light.
This is the simplest holographic principle. In addition, there are holograms (widely used in anti-counterfeiting signs) that can be reproduced by white light (referring to incoherent light sources, such as lights and sunlight), color holograms (which can reproduce the color of objects with white light) and so on. The production process of these holograms is quite complicated.
Although holograms usually refer to three-dimensional optical holograms, this is a misunderstanding. In addition, the sound field can also be made into a hologram.