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3D OPTICAL DATA STORAGE

Introduction Popularity and rate of adoption of optical disc has been unparalleled in the history of consumer electronics. volumetric nature of data structure. Distance between layers may be 5 to 100 micrometers. Greater than 100 layers of information can be stored on a single disc.

HISTORY Yehuda Hirshberg developed the photochromic spyropyrans. Valeri Barachevskii demonstrated photochromism could be prodused by two photon excitation. Peter.T.Rentzepis showed that this could lead to three dimensional data storage.

RECORDING DATA Laser light split into two-signal and reference beams. Data arranged as data pages. 0’s and 1’s of data pages are translated into pixels of the spatial light modulator. signal beam encoded with the data page pattern. Encoded beam interferes with the reference beam through the recording medium. photochemical changes takes place in the medium leads to recording of data pages. RECORDING DATA

Interference pattern induces modulations in the refractive index of the recording material yielding diffractive volume gratings Reference beam is used during readout of the recorded gratings, reconstructing the stored array of bits Reconstructed array is projected on to a pixelated detector that reads the data READING DATA

CROSS SECTION OF A 3-D DISC

MEDIA DESIGN Active part of media is usually an organic polymer doped with photo chemically active species. Media have been suggested in several forms- disc, card, crystal, cube or sphere. Media to be constructed layer by layer. It is analogous to a roll of adhesive tape.

DRIVE DESIGN Drive designed to this storage media has a lot in common with CD/DVD drives if both have similar form factor. Care must be taken for the followings during design Laser Variable spherical aberration correction Detection

DEVELOPMENT ISSUES Development of commercial products has taken a significant length of time due to limited financial backing in the field, as well as technical issues, including: Destructive reading Thermodynamic stability Media sensitivity

COMMERCIAL DEVELOPMENT Figure shows examples of 3D optical data storage media Top raw- Call/Recall media and Mempile media Middle raw- FMD and Drive Bottom raw- Landour media and microholas media in action

ADVANTAGES Terabyte data storage in an ordinary disc 1’’ diameter 50GB disc for data storage for mobiles More than 100 layer of information in a single disc More data storage in less space We can store 100s of movies in a single disc

DISADVANTAGES High cost Not easy to design as compared with other optical discs

APPLICATIONS Consumer entertainment applications Personal computing Application software distribution Data storage and transport medium world wide

CONCLUSION

REFERENCES www.wikipedia.com www.worldbook.com www.encarta.in www.google.com

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