Seminar Report on

HOLOGRAPHIC MEMORY

What is Holographic Memory ?

• It is a memory that can store information in form of holographic image.

• It is a technique that can store information at high density inside crystals or photopolymers.

• It provides data to be written beneath the surface of the disc.

• Holographic memory can store up to 1 Tb in a storage medium the size of a sugar cube crystal.

To spilt the laser beam

To direct the laser beams

spatial light modulator

photopolymer

Interprets the digital

informationBlue-green argon laser

Beam splitters

Mirrors

LCD panel

Lithium-niobate crystal

CCD camera

Basic Components

Working Principle

Continues..

Creating Holograms

Reconstructing the image

Shift Characteristics

Shift multiplexingread/write can bedone at 3μpitch

Read-out Page DataShift:

1μm pitch

Y

X

2μm

3μm

1μm

Properties of Hologram

• A block or sheet of photosensitive material which records the diffraction of two light sources.

• A laser beam is splitted into two beams: Source beam Reference beam

• The two beams diffracts to form the image on the recording medium.

Spatial light modulator

• It is used for creating binary information out of laser light.

• It is a 2D plane, consisting of pixels which can be turned on and off to create binary 1.s and 0.s.

• It contains a two-dimensional array of windows, which are only microns wide.

Page Data Access

• As the data is stored in the form of holograms, data retrieval must be in the same form.

• So, a holographic system sends data in the form of pages.

• It provides fast access times.

Error Correction

• As the density of data is massive, it is prone to errors.

• Errors can be controlled by:o Recording errorso Page level parity bitso Interfacing

Recording Errors

• Cause: Noise generated by laser beam

• Result: Can change a binary 0 to binary 1

• Possible Solution: Improvement in laser beam and recording material

Page-level Parity Bits

• Data is stored in the form of 2-D array

• Odd no. of bits accounts for parity 1

• Even no. of bits accounts for parity 0

• Parity check bits are used to identify any errors present in the array

APPLICATIONS OF HOLOGRAPHY

• Product packaging

• Data mining

• Holograms are used in credit card, license, books, magazine.

• Used in airplanes etc. in heads up display

• Used in testing for fractures and quality control.

• Application in future computer system.

• Used in 3-D projection of artistic images or expressions.

CONCLUSION

There is bright scope of advancement in the field of holography. The holographic storage provide high data density . It can easily store 1000GB of data in a small cubic centimeter crystal reducing the cost on the other hand .It may offer high data transfer rate. Till, the holographic storage is at the beginning stage, it will mark its existence soon in the market.

References

• www.almaden.com

• www.eik.bme.hu

• www.vision.caltech.edu

• Mansi, Mark “the hard disk survival guide” , BPB publications , 1993

QUERIES??