Applications:
Some of the applications of holography are discussed in brief below.
1. Holographic interferometry: The most successful application of holography, however, is in interferometry. If two holograms of the same object are recorded on the same plate, then upon reconstruction the two holographic images will interfere. If the object has undergone a deformation between the two recordings, phase differences in certain parts of the two images will result, creating an interference pattern that clearly shows the deformation.
2. Holographic diffraction gratings: Holography can be used to make gratings. In this method two laser beams are made to interfere on a recording medium which produces the rulings much more uniformly than any other method.
3. Holographic storage of digital data: The digital data can be recorded as bright and dark spots in holographic images. A hologram can contain a large number of ‘pages’ that are recorded at different angles relative to the plate, thus allowing the storage of a very large amount of data on one hologram. By illuminating the hologram with a laser beam at different angles, the pages can be read out one by one.
4. Acoustic holography: It is a method used to estimate the sound field near a source by measuring acoustic parameters away from the source. Measuring techniques included within acoustic holography are becoming increasingly popular in various fields, most notably those of transportation, vehicle and aircraft design.
5. Security holograms: They are very difficult to forge because they are replicated from a master hologram which requires expensive, specialized and technologically advanced equipment. They are used widely in many currencies, credit and bank cards as well as books, DVDs and sports equipment.
