18-Dec-15

OUT LINES 1.INTRODUCTION 2.CONCEPT OF HOLOGRAM 3.REQUIREMENTS FOR HOLOGRAPHY 4.DIFFERENCE BETWEEN PHOTOGRAPHY & HOLOGRAPHY 5.REDUNDANCY OF HOLOGRAM 6.METHOD OF STORING DATA 7.METHOD OF RETRIVING DATA 8.ADVANTAGES AND CHALLENGES 9.LATEST REASERACH ON HOLOGRAPHIC STORAGE

Holography is the new resolution in the stroage method of today.It is an advanced Optical stroage device.

HOLOGRAM CONCEPT Holography is a method of lenses photography in which the wave field of light scattered by an object is recorded in a place as an interface pattern.

REQUIREMENTS FOR HOLOGRAPHY There must be specifically two beams incident on the plate. 1-The reference beam 2- The object beam. The two beams are required to form the interface pattern. The other specially property of light used in holography is that it must be Coherent.

HolographicPhotographic The Difference Between Photography And Holography Lasers Redundancy Volume Light Point To Point Surface

MATERIALS REQUIRED The practical concern relater to holographic recording material include:- The recording resolution. Material sensitive as a function of optical wave length. The processing steps requires developing of the hologram.

REQUIREMENT:- SLM (SPATIAL LIGHT MODULATOR) CCD CAMERA BEAM SPLITTER

SLM :- It is a device that manipulate the amplitude and phase of a beam of light at different point of space. An SLM for a holographic storage need only be binary. What is necessary,however,is a high contrast and rapid switching between on and off states to enable clear distinction between the brightness and darkness pattern.

CCD CAMERA:- The main function of the CCD( Charge couple device ) device camera is interpreting the reconstructing data page and forward the digital information to a computer.

BEAM SPLITTER The beam splitter, which is used to split the original laser beam of light

Holography: Basic Principle Laser Mirror Lens Object Recording Plate Object Beam Reference Beam

Random Access Serial Access ? What Will Be The Next Logical Step In Computer Storage ?

Magnetic Optical Hard Disk Floppy Disk PCMCIA CD-ROM Magneto-Optical Disk Advantages: - Faster than tape - Allows direct access to data Disadvantages:- Performance relies on speed of mechanical heads - Neither fault nor damage resistant Advantages:-More data capacity than magnetic disk -High quality storage of sound and images Disadvantages:-Data capacity is small for video -Limited Data densities

Interference Patterns Wave A Wave B White Screen Crest of A concides with trough of B-Destructive intererence Two crests coincide- Constructive interference

mirror page mirror laser beam splitter read/write shutter spatial-light modulator transform lens recording medium imaging lens detector array Basic Holographic Storage System Basic Principle For Data Storage

Holographic Storage Device

A Holographic Storage Device Is A Page Oriented Device That Writes And Reads Data, Represented As A Two Dimensional Array Of Spot Called A Page. Multiple Pages Are Multiplexed Holographically To Create A Stack Of Pages, All In The Space Normally Required To Store A Single Two Dimensional Image.

Multimedia Floppy Organization 3000 stacks ( 1 gigabyte) Stack site: 1 mm2 40 pages per stack (320 Kbytes) 64K bits per page

Drive Cost (MB) Media Cost/MB Capacity (GB) Average Access Time (msec) Media Size Holographic (Tamarack) CD-ROM (NEC 3X) Magnetic Disk (Sony) $0.70$0.84$5.35 $0.01$0.002$ ”4.7”3.5”/5.25 Comparative Table

Storage Capacity Chart Year

Store information throughout the whole volume of the medium instead of just the surface as with other storage technologies. Uses fewer or no moving parts at all, thus allowing greater data processing speeds. Hold more information than 100 compact disks of the same diameter Can read 64,000 bits at one time, compared to to just one or two bits with magnetic storage. Provides unique robustness and error insensitivity A Holographic Disk can:

Video-On-Demand Portable Computing MultimediaConsumer Audio/Video Applications

METHOD OF STORING DATA – When the blue-argon laser is focused,a beam splitter splits it into two parts,a reference beam and a signal beam. –The signal beam passes through a SLM where digital information, organized in a page like format of ones and zeroes, is modulated onto the signal beam as a two dimensional pattern of brightness and darkness. –This signal beam is purified using different crystals (normally, light sensitivity Lithium Niobate crystal, through some systems use a photopolymer in the place of the crystal ).

contd. When the signal beam and the reference beam meet, the reference pattern created stores the data that is carried by the signal beam on to the surface of the holographic material as a hologram. Different data pages are recorded over the surface depending on the angle at which the reference beam meets the signal beam.

METHOD OF RETRIVING DATA To retrieve data, the reference beam is focused on the hologram at a particular angle ; this will retrieve the modulated data stored at the same angle of interference.To read the page,one need to pass it thorough detector and then through CCD camera, which will project the data on to the display panel.

ADVANTAGES OVER OTHER CONVENTIONAL METHOD.Large data density A holography disk can store information through the whole volume of the medium Instead of just the surface as with other storage technologies..Better reliability Uses fewer or no moving part at all, thus allowing greater data processing speeds.

Large capacity Can hold information more than that of 100 compact disks of the same diameter..High data transfer rate and short access time Can read 64,000 bits of information at a time, compared to just one or two bits with magnetic storage. Fault and damage tolerance Provides unique robustness and error sensitivity. Cont.

MAJOR CHALLENGES. Integration of the state-of-art-components:- Still is very difficult to arrange all of those components like CCD camera, SLM arrays and beam steering devices..Lack of suitable medium:- Needs good recordings sensitive material to allow high data transfer rate. High optical quality to reading of data without degrading. Be able to retain data content without loss in the long term. Versatility to allow update of information as incase of rewritable systems.

LATEST RESEARCH ON HOLOGRAPHY STORAGE Small farms like Optiteck and Tamarack are the leading research organization in this field. Also large organizations like IBM,DARPA, LUCENT etc. have been investing lots of money in the research field. Also great process has been made in other related key components of a holographic storage device. It is expected that the first holographic device will be in the market within one or two year.

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