Apr 21, 2023 www.fakengineer.com

OUT LINES1.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 CONCEPTHOLOGRAM 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 REQUIREMENTS FOR HOLOGRAPHYHOLOGRAPHY

• 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 REQUIREDMATERIALS 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 CAMERACCD 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 SPLITTERBEAM SPLITTER

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

Holography: Basic Principle

Laser

Mirror Mirror

Mirror

Lens

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-Destructiveintererence

Two crests coincide-Constructive interference

mirrorpage mirror

laser beam splitterread/write shutter

spatial-lightmodulator

transform lens

recordingmedium

imaging lens

detectorarray

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)

MagneticDisk (Sony)

$0.70 $0.84 $5.35

$0.01 $0.002 $0.14

1.0 0.65 0.14

32 195 300

2.5” 4.7” 3.5”/5.25

Comparative Table

0

2000

4000

6000

8000

10000

12000

1993 1995 1998

MAGN. DISK

OPTIC. DISK

HOLO. DISK

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-DemandPortable Computing

Multimedia Consumer Audio/Video

Applications

METHOD OF STORING DATAMETHOD 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 ).

contdcontd..

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 DATAMETHOD 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 mediumInstead 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.

LATESTLATEST RESEARCHRESEARCH ONON HOLOGRAPHYHOLOGRAPHY STORAGESTORAGE

• 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 .

..