Holographic Storage (Autosaved)

7/29/2019 Holographic Storage (Autosaved)

1/18

HOLOGRAPHIC STORAGE TECHNOLOGY

A Technical Report submitted

in partial fulfillment of the requirement

for the award of the degree of

BACHELOR OF TECHNOLOGY

In

ELECTRONICS AND COMMUNICATION ENGINEERING

By

K.VARUN KUMAR

(09PQ1A0463)

Department of Electronics and Communication Engineering

ANURAG COLLEGE OF ENGINEERING(Approved by A.I.C.T.E New Delhi, Affiliated to J.N.T.U. Hyderabad)

Aushapur(V), Ghatkesar(M), R.R.Dist- 501301

2012-2013


2/18

ANURAG COLLEGE OF ENGINEERING(Approved by A.I.C.T.E New Delhi, Affiliated to J.N.T.U. Hyderabad)

Aushapur(V), Ghatkesar(M), R.R.Dist- 501301

2012-2013Department of Electronics and Communication Engineering

Bonafide Certificate

This is to certify that the Technical Report entitled HOLOGRAPHIC STORAGE

TECHNOLOGY, is being submitted by KANDUKURI VARUN KUMAR bearing the

Regd. No. 09PQ1A0463 in partial fulfillment for the award of the degree of Bachelor

of Technology in ELECTRNOICS AND COMMUNICATION ENGINEERING is a

record of confide work carried out by him under my guidance and supervision during the

academic year 20122013 and it has been found worthy of acceptance according to the

requirements of the university.

Guide Head of the Department


3/18

ACKNOWLEDGEMENT

I have successfully completed my technical report. It happens only because of some

auxiliary co-operation from some people.

K.VARUN09PQ1A0463


4/18

ABSTRACT

Devices that use light to store and read data have been the backbone of data

storage for nearly two decades. Compact discs revolutionized data storage in the early1980s, allowing multi-megabytes of data to be stored on a disc that has a diameter of a

mere 12 centimeters and a thickness of about 1.2 millimeters.

In 1997, an improved version of the CD, called a digital versatile disc (DVD),

was released, which enabled the storage of full-length movies on a single disc. CDs and

DVDs are the primary data storage methods for music, software, personal computing and

video. A CD can hold 783 megabytes of data, which is equivalent to about one hour and

15 minutes of music, but Sony has plans to release a 1.3-gigabyte (GB) high-capacity

CD. A double-sided, double-layer DVD can hold 15.9 GB of data, which is about eight

hours of movies. These conventional storage mediums meet today's storage needs, but

storage technologies have to evolve to keep pace with increasing consumer demand.

CDs, DVDs and magnetic storage all storebits of information on the surface of

a recording medium. In order to increase storage capabilities, scientists are now working

on a new optical storage method, called holographic memory, that will go beneath the

surface and use the volume of the recording medium for storage, instead of only the

surface area. Three-dimensional data storage will be able to store more information in a

smaller space and offer faster data transfer times
http://computer.howstuffworks.com/dvd.htmhttp://computer.howstuffworks.com/bytes.htmhttp://computer.howstuffworks.com/bytes.htmhttp://computer.howstuffworks.com/dvd.htm


5/18

CONTENTS

1. INTRODUCTION

1.1. COMPACT DISK

1.2. DIGITAL VERSATILE DISK

1.3. BLUR-RAY DISK

2. HOLOGRAPHIC DATA STORAGE

2.1. HOLGRAPHY

2.2. DESKTOP HOLOGRAPHIC DATA STORAGE

2.3. THE HOLOGRAPHIC DATA

2.4. RECORDING OF DATA IN HOLOGRAPHIC MEMORY

SYSTEMS

2.5. RETRIEVING OF DATA IN HOLOGRAPHIC MEMORY

SYSTEMS

2.6. PAGE DATA ACCESS2.7. RECORDING ERRORS

2.8. PAGE LEVEL PARITY BITS

3. MERITS & CHALLENGES OF HOLOGRAPHIC STORAGE

3.1. MERITS OF HOLOGRAPHHIC MEMORY

3.2. CHALLENGES

4. POSSIBLE APPLICATIONS

5. CONCLUSION

6. REFERENCES


6/18

LIST OF FIGURES

FIG 1.1 CROSS SECTION OF CD

FIG 1.2 REFLECTION OF LASER IN CD

FIG 1.3 REFLECTION OF LASER ON PIT

FIG 1.4 TRACK OF CD

FIG 1.5 TRACK OF DVD

FIG 1.6 DVD Vs. BLU-RAY CONSTRUCTION

FIG 2.1 HOLOGRAHIC DATA STORAGE SYSTEM

FIG 2.2 WRITING OF DATA

FIG 2.3 READING OF DATA


7/18

1. INTRODUCTION

The hologram was invented in 1947 by Dennis Gabor to record images in a

medium (e.g., a crystal). It has a very unique feature, namely, any small part of the

medium contains all information about the image. Therefore, even if the medium isbroken into pieces, the entire image can still be obtained from any piece, except the

resolution is reduced.

Holographic memory offers the possibility of storing 1 terabyte (TB) of data in

a sugar-cube-sized crystal. A terabyte of data equals 1,000 gigabytes, 1 million

megabytes or 1 trillion bytes. Data from more than 1,000 CDs could fit on a holographic

memory system. Most computerhard drives only hold 80 to 160 GB of data, a small

fraction of what a holographic memory system might hold. Polaroid scientist Pieter J. van

Heerden first proposed the idea of holographic (three-dimensional) storage in the early

1960s. A decade later, scientists at RCA Laboratories demonstrated the technology by

recording 500 holograms in an iron-doped lithium-niobate crystal, and 550 holograms of

high-resolution images in a light-sensitive polymer material.

Devices that use light to store and read data have been the backbone of data

storage for nearly two decades. It started from CDs which can store 700MB and has

moderate speed. Then came DVD which can store up to 17 GB and has speed up to 10

Mbps. Recently in 2006 ,BLU-RAY disc was launched which has capacity up to 54 GB

and speed of 36 Mbps.

But looking to the future we need to go ahead and find a better way of storing

data, a easier way which is far more better in speed as well as memory. In to achieve this

scientist have proposed a new technology which uses 3-D layers instead of conventional

2-D. This technology is named HOLOGRAPHIC DATA STORAGE

1.1 COMPACT DISC(CD):

Most of a CD consists of an injection-molded piece of clear polycarbonate

plastic. During manufacturing, this plastic is impressed with microscopic bumps

arranged as a single, continuous, extremely long spiral track of data. A CD has a

single spiral track of data, circling from the inside of the disc to the outside. The

elongated bumps that make up the track are each 0.5 microns wide, a minimum of

0.83 microns long and 125 nanometers high.
http://computer.howstuffworks.com/hard-disk.htmhttp://computer.howstuffworks.com/hard-disk.htmhttp://computer.howstuffworks.com/framed.htm?parent=holographic-memory.htm&url=http://www.polaroid.comhttp://computer.howstuffworks.com/hard-disk.htmhttp://computer.howstuffworks.com/framed.htm?parent=holographic-memory.htm&url=http://www.polaroid.com


8/18

FIG 1.1CROSS SECTION OF CD

A label layer

B protection layer

C Data layer (reflection layer)D protection layer (transparent)

E Logical 0 (bump)

F Logical 1 (pit)

DATA RETRIEVAL IN CD:

The data in the cd is stored in these extremely small bumps. The data is

retrieved with the help of a red laser beam in the manner as shown.

FIG 1.2 REFLECTION OF LASER IN CD

In the first image, we see that the laser (A), reflects (Image 1) on the

bump. The reflected laser light however does not seem to reach the sensor (B). The

CD-player interprets this as a logical ZERO.


9/18

FIG 1.3 REFLECTION OF LASER ON PIT

In the second image we see a reflection on a pit (Image 2). Here we see that the

reflected laser light DOES reach the sensor (B). This is being interpreted by the CD-

player as a logical ONE. The incredibly small dimensions of the bumps make the spiral

track on a CD extremely long. If we could lift the data track off a CD and stretch it out

into a straight line, it would be 0.5 microns wide and almost 3.5 miles (5 km) long

1.2 DIGITAL VERSATILE DISC(DVD):

DVDs are of the same diameter and thickness as CDs, and they are made

using some of the same materials and manufacturing methods. Like a CD, the data on

a DVD is encoded in the form of small pits and bumps in the track of the disc. The

elongated bumps that make up the track are each 320 nanometers wide, a minimum of

400 nanometers long and 120 nanometers high. The biggest advantage of a DVD over

a CD is that the pits and the tracks in DVD are smaller so that it takes less space than

a DVD to store the same amount of data. Thus physically tighter spacing of pits on a

DVD increases its storing capabilities.

FIG 1.4 TRACK OF CD FIG 1.5 TRACK OF DVD


10/18

1.3 BLU-RAY DISC:

The movie industry has set a revolution with the introduction of Blu-ray Discs

(BD) in 2006. With their high storage capacity, Blu-ray discs can hold and play back

large quantities of high-definition video and audio, as well as photos, data and other

digital content. Unlike current DVDs, which use a red laser to read and write data, Blu-

ray uses a blue laser. A blue laser has a shorter wavelength (405 nanometers) than a redlaser (650 nanometers). The smaller beam focuses more precisely, enabling it to read

information recorded in pits that are only 0.15 microns (m) long. Because of this in a

Blu-ray the track pitch has been reduced from 0.74 microns to 0.32 microns.

FIG 1.6 DVD Vs. BLU-RAY CONSTRUCTION


11/18

2. HOLOGRAPHIC DATA STORAGE

2.1 HOLOGRAPHY:

A hologram is a block or sheet of photosensitive material which records the

interference of two light sources. To create a hologram, laser light is first split into two

beams, a source beam and a reference beam. The source beam is then manipulated and

sent into the photosensitive material. Once inside this material, it intersects the reference

beam and the resulting interference of laser light is recorded on the photosensitive

material, resulting in a hologram. Once a hologram is recorded, it can be viewed with

only the reference beam. The reference beam is projected into the hologram at the exact

angle it was projected during recording. When this light hits the recorded diffraction

pattern, the source beam is regenerated out of the refracted light. An exact copy of the

source beam is sent out of the hologram and can be read by optical sensors. For example,

a hologram that can be obtained from a toy store illustrates this idea. Precise laser

equipment is used at the factory to create the hologram. A recording material which can

recreate recorded images out of natural light is used so the consumer does not need high-

tech equipment to view the information stored in the hologram. Natural light becomes the

reference beam and human eyes become the optical sensors.

Holography was invented in 1947 by the Hungarian-British physicist Dennis

Gabor (1900-1979), who won a 1971 Nobel Prize for his invention.

DESKTOP HOLOGRAPHIC DATA STORAGE

After more than 30 years of research and development, a desktop holographic

storage system (HDSS) is close at hand. Early holographic data storage devices will have

capacities of 125 GB and transfer rates of about 40 MB per second. Eventually, these

devices could have storage capacities of 1 TB and data rates of more than 1 GB per

second -- fast enough to transfer an entireDVD movie in 30 seconds. So why has it taken

so long to develop an HDSS, and what is there left to do?

Like other media, holographic media is divided into write once (where the

storage medium undergoes some irreversible change), and rewritable media (where the

change is reversible). Rewritable holographic storage can be achieved via the

photorefractive effect in crystals.
http://computer.howstuffworks.com/dvd.htmhttp://computer.howstuffworks.com/dvd.htmhttp://en.wikipedia.org/wiki/Photorefractive_effecthttp://computer.howstuffworks.com/dvd.htmhttp://en.wikipedia.org/wiki/Photorefractive_effect


12/18

2.2 The HOLOGRAPHIC DATA STORAGE SYSTEM:

Prototypes developed by Lucent and IBM differ slightly, but most

holographic data storage systems (HDSS) are based on the same concept. Here are the

basic components that are needed to construct an HDSS:

Blue-green argon laser Beam splitters to spilt the laser beam

Mirrors to direct the laser beams

LCDpanel (spatial light modulator)

Lenses to focus the laser beams

Lithium-niobate crystal or photopolymer

Charge-coupled device (CCD) camera

FIG 2.1 HOLOGRAPHIC DATA STORAGE SYSTEM

When the blue-green argon laser is fired, a beam splitter creates two beams.

One beam, called the object or signal beam, will go straight, bounce off one mirror and

travel through a spatial-light modulator (SLM). An SLM is a liquid crystal display (LCD)

that shows pages of raw binary data as clear and dark boxes. The information from the

page of binary code is carried by the signal beam around to the light-sensitive lithium-

niobate crystal. Some systems use a photopolymer in place of the crystal.

A second beam, called the reference beam, shoots out the side of the beam

splitter and takes a separate path to the crystal. When the two beams meet, the

interference pattern that is created stores the data carried by the signal beam in a specific

area in the crystal -- the data is stored as a hologram .
http://computer.howstuffworks.com/laser.htmhttp://computer.howstuffworks.com/lcd.htmhttp://computer.howstuffworks.com/digital-camera.htmhttp://computer.howstuffworks.com/lcd.htmhttp://computer.howstuffworks.com/laser.htmhttp://computer.howstuffworks.com/lcd.htmhttp://computer.howstuffworks.com/digital-camera.htmhttp://computer.howstuffworks.com/lcd.htm


13/18

An advantage of a holographic memory system is that an entire page of data

can be retrieved quickly and at one time. In order to retrieve and reconstruct the

holographic page of data stored in the crystal, the reference beam is shined into the

crystal at exactly the same angle at which it entered to store that page of data. Each page

of data is stored in a different area of the crystal, based on the angle at which the

reference beam strikes it. During reconstruction, the beam will be diffracted by the

crystal to allow the recreation of the original page that was stored. This reconstructed

page is then projected onto the charge-coupled device (CCD) camera, which interprets

and forwards the digital information to a computer. The key component of any

holographic data storage system is the angle at which the second reference beam is fired

at the crystal to retrieve a page of data. It must match the original reference beam angle

exactly. A difference of just a thousandth of a millimeter will result in failure to retrieve

that page of data.

2.4 RECORDING OF DATA IN HOLOGRAPHIC MEMORY

SYSTEM

When the blue-green argon laser is fired, a beam splitter creates two beams.

One beam, called the object or signal beam, will go straight, bounce off one mirror and

travel through a spatial-light modulator (SLM). An SLM is a Liquid crystal display

(LCD) that shows pages of raw binary data as clear and dark boxes. The information

from the page of binary code is carried by the signal beam around to the light-sensitive

lithium-niobate crystal. Some systems use a photopolymer in place of the crystal. A

second beam, called the reference beam, shoots out the side of the beam splitter and takes

a separate path to the crystal. When the two beams meet, the interference pattern that is

created stores the data carried by the signal beam in a specific area in the crystal - the

data is stored as a hologram.

FIG. 2.2 WRITING OF DATA

2.5 RETRIEVAL OF DATA FROM HOLOGRAPHIC MEMORY

SYSTEM

An advantage of a holographic memory system is that an entire page of data

can be retrieved quickly and at one time. In order to retrieve and reconstruct the

holographic page of data stored in the crystal, the reference beam!

s shined into thecrystal at exactly the same angle at which it entered to store that oage of data. Each page

of data is stored in a different area of the crystal, based on the angle at which the

reference beam strikes it. During reconstruction, the beam will be diffracted by the

crystal to allow the recreation of the original page that was stored. This reconstructed

page is then projected onto the charge-coupled device (CCD) camera, which interprets

and forwards the digital Formation to a computer.

Laser
http://computer.howstuffworks.com/category-computers.htmhttp://computer.howstuffworks.com/category-computers.htm


14/18

Recording

medium

RecoveredData

CCD is a 2-D array of thousands or millions of tiny solar cells, each of

which transforms the light from one small portion of the image into electrons. Next step

is to read the value (accumulated charge) of each cell in the image. In a CCD device, the

charge is actually transported across the chip and read at one corner of the array. An

analog-to-digital converter turns each pixel's value into a digital value. CCDs use a

special manufacturing process to create the ability to transport charge across the chip

without distortion. This process leads to very high-quality sensors in terms of fidelity and

light sensitivity. CCD sensors have been mass produced for a longer period of time, so

they are more mature. They tend to have higher quality and more pixels. The key

component of any holographic data storage system is the angle at which the second

reference beam is fired at the crystal to retrieve a page of data. It must match the original

reference beam angle exactly. A difference of just a thousandth of a millimeter will result

in failure to retrieve that page of data.

011101010101001010

FIG 2.3 READING OF DATA

2.6 PAGE DATA ACCESS

Because data is stored as page data in a hologram, the retrieval of this data must

also be in this form. Page data access is the method of reading stored data in sheets, not

serially as in conventional storage systems. It was mentioned in the introduction that

conventional storage was reaching its fundamental limits. One such limit is the way datais read in streams.

Holographic memory reads data in the form of pages instead. For example, if a

stream of 32 bits is sent to a processing unit by a conventional read head,a holographic

memory system would in turn send 32 x 32 bits, or 1024 bits due to its added dimension.

This provides very fast access times in volumes far greater than serial access methods.


15/18

The volume could be one Megabit per page using a SLM resolution of 1024 x 1024 bits

at 15-20 microns per pixel.

2.7 RECORDING ERRORS

When data is recorded in a holographic medium, certain factors can lead to

erroneously recorded data. One major factor is the electronic noise generated by laserbeams. When a laser beam is split up ( for example, through a SLM ), the generated light

bleeds into places where light was meant to be blocked out. Areas where zero light is

desired might have minuscule amounts of laser light present which mutates its bit

representation. For example, if too much light gets recorded into this zero area

representing a binary 0, an erroneous change to a binary 1 might occur. Changes in both

the quality of the laser beam and recording material are being researched, but these

improvements must take into consideration the cost-effectiveness of a holographic

memory system. These limitations to current laser beam and photosensitive technology

are some of the main factors for the delay of practical holographic memory systems.

2.8 PAGE-LEVEL PARITY BITS

Once error-free data is recorded into a hologram, methods which read data

back out of it need to be error free as well. Data in page format requires a new way to

provide error control. Current error control methods concentrate on a stream of bits.

Because page data is in the form of a two dimensional array, error correction needs to

take into account the extra dimension of bits. When a page of data is written to the

holographic media, the page is separated into smaller two dimensional arrays. These sub

sections are appended with an additional row and column of bits. The added bits calculate

the parity of each row and column of data. An odd number of bits in a row or column

create a parity bit of 1 and an even number of bits create a 0. A parity bit where the row

and column meet is also created which is called an overall parity bit. The sub sections are

rejoined and sent to the holographic medium for recording.

3. MERITS & CHALLENGES OF HOLOGRAPHIC STORAGE

3.1 MERITS OF HOLOGRAPHIC MEMORY

Holographic memory offers storage capacity of about 1 TB. Speed of

retrieval of data in tens of microseconds compared to data access time of almost 10ms

offered by the fastest hard disk today. By the time they are available they can transfer an

entire DVD movie in 30 seconds. Information search is also faster in holographic

memory. Consider the case of large databases that are stored on hard disk today. To


16/18

retrieve any piece of information you first provide some reference data. The data is then

searched by its address, track, sector and so on after which it is compared with the

reference data. In holographic storage entire pages can be retrieved where contents of two

or more pages can be compared optically without having to retrieve the information

contained in them. Also HDSS has no moving parts. So the limitations of mechanical

motion such as friction can be removed.

3.2 CHALLENGES

During the retrieval of data the reference beam has to be focused at exactly

the same angle at which it was projected during recording. A slight error can cause a

wrong data page to be accessed. It is difficult to obtain that much of accuracy. The crystal

used as the photographic filament must have exact optical characteristics such as high

diffraction efficiency, storage of data safely without any erasure and fast erasure on

application of external stimulus light ultra violet rays. With the repeated number of

accesses the holograms will tend to decay.

4. POSSIBLE APPLICATIONS

There are many possible applications of holographic memory.

Holographic memory systems can potentially provide the high-speed transfers and largevolumes of future computer systems. One possible application is data mining.

Data mining is the process of finding patterns in large amounts of data. Data miningis

used greatly in large databases which hold possible patterns which can.t be

distinguished by human eyes due to the vast amount of data. Some current computer

systems implement data mining, but the mass amount of storage required is pushing

the limits of current data storage systems. The many advances inaccess times and data


17/18

storage capacity that holographic memory provides could exceed conventional storage

and speed up data mining considerably. This would result in more located patterns

in a shorter amount of time.Another possible application of holographic memory is in

petaflop computing. A petaflop is a thousand trillion floating point operations per

second. The fast access in extremely large amounts of data provided by holographic

memory systems couldbe utilized in a petaflop architecture. Clearly advances are needed

in more than memory systems, but the theoretical schematics do exist for such a

machine. Optical storage such as holographic memory provide a viable solution to the

extreme amount of data which is required for petaflop computing.

HOLOGRAPHIC MEMORY VS. CONVENTIONAL STORAGE DEVICES

Storage Medium Access Time

Data Transfer Rate

Storage Capacity

Holographic

Memory

2.4 us lOGB/s 400 Mbits/cm2

Main Memory

(RAM)

10-40 ns 5 MB/s 4.0 Mbits/cm2

Magnetic Disk 8.3 ms 5-20 MB/s 100 Mbits/cm2

5. CONCLUSION

The future of holographic memory is very promising. The page access of

data that holographic memory creates will provide a window into next generation

computing by adding another dimension to stored data. Finding holograms in

personal computers might be a bit longer off, however. The large cost of high-tech

optical equipment would make small-scale systems implemented with holographic

memory impractical. Holographicmemory will most likely be used in next

generation super computers where cost is not as much of an issue. Currentmagnetic

storage devices remain far more cost effective than any other medium on the market.

As computer systems evolve, it is not unreasonable to believe that magnetic storage

will continue to do so. As mentioned earlier, however, these improvements are not


18/18

made on the conceptual level. The current storage in a personal computer operates on

the same principles used in the first magnetic data storage devices. The parallel nature

of holographic memory has many potential gains on serial storage

methods.However, many advances in optical technology and photosensitive

materials need to be made before we find holograms in computer systems.

6. REFERENCES

1. http://www.howstuffworks.com

2. http://[email protected]

3. http ://www. stanford.edu/~svngam/
http://www.howstuffworks.com/http://nford.edu/~svngam/http://www.howstuffworks.com/http://nford.edu/~svngam/

Date post:	03-Apr-2018
Category:	Documents
Upload:	sandeep-anugandula
View:	221 times
Download:	0 times

Holographic Storage (Autosaved)

Documents