Holografi memory

of Holografi memory is a technology, with which one can store information in a very high density within crystals or photopolymers. There current memory technologies such as z. B. the DVD the upper limit of the data density achieved, has a Holografi memory the potential the next generation from storage medium to to become (HVD). The advantage of this data memory is that the complete volume of the recording material, and not only the surface can be used. This aspect permits the fact that phenomena can be used such as Bragg volume Addressierung whereby more information in the same volume at storage medium can be accommodated very much. But each hologram must Bragg be detuned against its neighbours. This can be achieved by several methods, z. B. by rotation of the storage medium with consideration of the photograph medium and the reference radiation or by change of the wavelength or phase of the photograph laser beam for each hologram.

As also with other data media holographic memory is once into recordable memory (the storage medium not reversibly changed) and into again-recordable memory (change is reversible) partitions. Re+recordable holographic memory can be achieved by the fotorefraktiven effect in crystals:

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If information from a hologram to be called up or read is, is only the reference jet necessary. The jet becomes in exactly the same way, as it happened, when the hologram was written, into the material skillfully. As result of the changes of index in the storage medium, which were produced during the write process, the jet is divided into two parts. One of it represents the signal, in which the information is stored. Equipment such as z. B. a CCD - Camera can be used then, in order to then bring these data into a better usable form.

Hologramme can store theoretically a bit in a cube with the edge length of the wavelength of the light, which was used for the letter. The light z. B. a Helium-Neon-Lasers is red (exact wavelength: 632.8 Nm). If one uses now light of this wavelength, square inch a memory 1,61×10 holografischen of perfect could store 13 bits, which corresponds approximately to 2,014 Terabyte. A Kubikinch of such memory would have a storage capacity of 8.083.729.105 Terabyte. But memory density is in practice substantially lower, since still bits are needed for error correction, and which must become balanced defectiveness of the optical system.

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literature data

  • A. M. Glass (preface), M. J. Cardillo (preface), Hans's J. Coufal (publisher), the trichloroethylene Psaltis (publisher), Glenn T. Sincerbox (publisher): Holographic DATA STORAGE. ISBN 3540666915
 

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