DATA STORAGE USING HOLOGRAPHY : DATA STORAGE USING HOLOGRAPHY HOLOGRAPHY: : HOLOGRAPHY: The science of producing holograms, an advanced form of photography that allows an image to be recorded in three dimension.
Holographic memory is a technique that can store information at high density inside crystals or photopolymers. Features: : Features: Data Transfer Rate:1Gbps.
Technology permits over 10 kilobits of data to be written and read in parallel with in a single flash.
CD saves one bit per pulse whereas HVD stores 60,000 bits per pulse in the same place.
1 HVD=5800 CDs=830 DVD=160 Blue Ray COMPRASION : COMPRASION PROCESS INVOLVED: : PROCESS INVOLVED: In a hologram, both the amplitude and phase of the light are recorded.
When reconstructed, the resulting light field is identical to that which emanated from the original scene, giving a perfect three-dimensional image Recording Process: : Recording Process: RECONSTRUCTION: : RECONSTRUCTION: Once the film is processed, if illuminated once again with the reference beam, diffraction from the fringe pattern on the film reconstructs the original object beam in both intensity and phase.
Because of the need for interference between the reference and object beams, holography typically uses a laser in production.
The coherence length of the beam determines the maximum depth the image can have. Reconstruction medium: : Reconstruction medium: REAL TIME HOLOGRAM: : REAL TIME HOLOGRAM: Here the steps of recording, developing and reconstruction all take place at the same time.
A material with properties which allow continuous updating of the hologram making the hologram dynamic so that the image information which records the hologram can change and the reconstructed output can also track, or change, simultaneously. Digital Holography: : Digital Holography: Makes use of digital devices likes CCD(charge coupled devices) instead of conventional photographic film.
In this, the reconstruction process can be carried out by digital processing of the recorded hologram by a computer.
Image of the object can later be visualized on the computer screen. Types of errors caused: : Types of errors caused: The readout conditions change.
The detector array doesn’t line up with the pixel array in the reconstructed hologram.
The detector is receiving undesired light.
There are brightness variations across the detected image. Combating the Errors : : Combating the Errors : Designer decrease error rate by storing redundant bits with user data.
This forms an ECC(Error Correcting Code). Advantages: : Advantages: PC with a holographic technology platform (HoloPCs) will be able to access data more rapidly and in a qualitatively different manner than conventional PCs.
Two-dimensional data saving systems such as CDs and DVDs record and retrieve files in a serial fashion -- one bit at a time. Holographic data systems retain and retrieve data in parallel, a total (million- bit) page of files at a time.
The interface of holography and robotics may make holobots that learn through creative identification of useful patterns in big quantities of files. Disadvantages: : Disadvantages: Manufacturing cost HDSS is very high and there is a lack of availability of resources which are needed to produce HDSS.
Holograms appear dimmer because their patterns must share the material's finite dynamic range.
Writes in the same fashion can degrade previous writes in the same region of the medium. Conclusion: : Conclusion: The future of HOLOGRAPHIC DATA STORAGE SYSYEM is very promising. The page access of data that HDSS creates will provide a window into next generation computing by adding another dimension to stored data.
Can achieve higher amount of memory storage.
Can achieve higher data transfer rates so as to reduce the access time.
This technology has revolutionalized the storage media. Future Enhancements: : Future Enhancements: Erasable Write-once, Read-many drives :supports Terabytes of storage,1 GBit/second read-out and access of data in blocks.
Write-once 3D disk: accessing time is only 10-100msec.
Pre-recorded 3D disks: supports more than 100 Gbytes per 120 mm and readout rates are greater than 200 Mbits/sec.