Use the interference of object light and reference light to record an interference pattern on the photosensitive film, which is an intricate pattern with different transparency. It is called a hologram (that is, a holographic photo), which is equivalent to making the film into an irregular shape. grating, and then use the diffraction of appropriate illumination light by the hologram to extract the original three-dimensional image. The latter process is called reappearance. Hologram is a natural information storage that can "resurrect" the "frozen" scenery in front of people's eyes. Due to this unique property, holograms have an extremely wide range of applications. For example, it is used to study the shock waves of rocket flight and non-destructive testing of aircraft wing honeycomb structures. Now there is not only laser holography, but also white light holography, rainbow holography, and panoramic rainbow holography have been successfully researched, allowing people to see all sides of the scene. Holographic three-dimensional display is developing in the direction of holographic color stereoscopic TV and movies.
In addition to using light waves to generate holograms, computers have been developed to generate holograms. Holograms are widely used and can be made into various thin-film optical components, such as various lenses, gratings, filters, etc. They can be overlapped in space and are very compact and lightweight, making them suitable for space flight. The use of holograms to store data has the advantages of large capacity, easy extraction, and anti-fouling.