seninar report

8/2/2019 Seninar Report

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ABSTRACT

Holographic memory is a technique that can store information at high density

inside crystals. Holographic memory is developing technology that has promised to

revolutionalise the storage systems. 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 computer hard drives only hold 10 to 40 GB of

data, a small fraction of what a holographic memory system might hold.

Holographic storage has the potential to become the next generation of storage

media. It has more advantages than conventional storage systems. Conventional

memories use only the surface to store the data. But holographic data storage systems

use the volume to store data. Holographic data storage system (HDSS), a three

dimensional data storage system which enable more information to be stored in a much

smaller space and has a fundamental advantage over conventional read/write memory

systems.

The technology uses holograms which are created when a light from a single laser

beam is split into two beams; the signal beam (which carries the data) and the reference

beam. In holographic storage, at the point where the reference beam and the data

carrying signal beam intersect, the hologram is recorded in the light sensitive storage

medium.

When you create a variance in the reference beam angle or media position then

hundreds of unique holograms can be recorded in the same volume of material. To read

the stored holographic data, the reference beam is deflected off the hologram

reconstructing the stored information. This hologram is then projected onto a detector

that reads the entire data page of over one million bits at once.

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 entire DVD movie in 30 seconds.

Chapter 1
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INTRODUCTION

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 early

1980s, 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 store bits of

information on the surface of a recording medium.

Mass memory systems serve computer needs in both archival and backup needs.

There exist numerous applications in both the commercial and military sectors that

require data storage with huge capacity, high data rates and fast access. To address such

needs 3-D optical memories have been proposed. Since the data are stored in volume,

they are capable of much higher storage densities than existing 2-D memory systems. In

addition this memory system has the potential for parallel access. Instead of writing or

reading a sequence of bits at each time, entire 2-D data pages can be accessed at one

go.

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.

Storing information through the volume of the medium not on its surface offers

an intriguing high capacity alternative.

Holographic data storage is a volumetric approach, which has made recent

progress towards practicality with the appearance of lower cost enabling technologies.

Hence the holographic memory has become a great white whale of technology research.

Mass memory systems serve computer needs in both archival and backup needs.

There exist numerous applications in both the commercial and military sectors that

require data storage with huge capacity, high data rates and fast access. To address such
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needs 3-D optical memories have been proposed. Since the data are stored in volume,

they are capable of much higher storage densities than existing 2-D memory systems. In

addition this memory system has the potential for parallel access. Instead of writing or

reading a sequence of bits at each time, entire 2-D data pages can be accessed at one

go. With advances in the growth and preparation of various photorefractive materials,

along with the advances in device technologies such as spatial light modulators(SLM),

and detector arrays, the realizations of this optical system is becoming feasible.

A hologram is a recording of the optical interference pattern that forms at the

intersection of two coherent optical beams. Typically, light from a single laser is split into

two paths, the signal path and the reference path.. The beam that propagates along the

signal path carries information, whereas the reference is designed to be simple to

reproduce. A common reference beam is a plane wave: a light beam that propagates

without converging or diverging. The two paths are overlapped on the holographic

medium and the interference pattern between the two beams is recorded. A key

property of this interferometric recording is that when it is illuminated by a readout

beam, the signal beam is reproduced.

Chapter 2

HISTORICAL ROOTS

Dr. Dennis Gabor is known as the father of holography. In year 1947, Dr. Gobor a

Hungerian Physicist given the idea of holography at the imperial college of London


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in1971 Dr. Gabor received a noble prize in physics for holography. His theory was

originally meant to increase the resolving power of electronic microscope and towards

that he used light of beam instead of electronic beam and this resulted in the first

hologram ever made. In 1960s, two engineers from the University of Michigon, Emmitt

Lerth and Juris Upatlipks, developed a new device that produce a 3-D image of an

object. Polaroid scientist Peter J. Vann Heerdern proposed the idea of holographic

storage in the early 1960s and decade later scientist at RCA laboratories demonstrated

the holographic storage 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. However, the development of holographic data storage was put on hold for

several years because of the absence of cheap parts of the advancement in magnetic

and semiconductor memories.

In recent years IBM and lucent Bell labs are actively involved in creating a

successful holographic storage medium as a result of which it has become possible to

store 1000 GB of data in a small cube.

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 persecond fast enough to transfer an entire DVD movie in 30 seconds. So why has it taken

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

When the idea of an HDSS was first proposed, the components for constructing

such a device were much larger and more expensive. For example, a laser for such a

system in the 1960s would have been 6 feet long. Now, with the development of

consumer electronics, a laser similar to those used in CD players could be used for the

HDSS. LCDs weren't even developed until 1968, and the first ones were very expensive.

Today, LCDs are much cheaper and more complex than those developed 30 years ago.

Additionally, a CCD sensor wasn't available until the last decade. Almost the entire HDSS

device can now be made from off-the-shelf components, which means that it could be

mass-produced.
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Chapter 3

What is HOLOGRAPHIC STORAGE?

Holographic storage works by storing a sequence of discrete data snapshots

within the thickness of the media. The storage process starts when a laser beam is split

into two signals. One beam is used as a reference signal. Another beam, called the data-

carrying beam, is passed through a device called a spatial light modulator (SLM) which


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acts as a fine shutter system, passing and blocking light at points corresponding to ones

and zeroes. The reference beam is then reflected to impinge on the data-carrying beam

within the media. This creates a three-dimensional refraction pattern (the "hologram")

that is captured in the media. Holographic storage uses circular media similar to a blank

CD or DVD that spins to accept data along a continuous spiral data path. Once the media

is written, data is read back using the reference beam to illuminate the refraction.

This three-dimensional aspect of data recording is an important difference

between holographic storage and conventional CD/DVD recording. Traditional optical

media uses a single laser beam to write data in two dimensions along a continuous spiral

data path. In contrast, prototype holographic storage products save 1 million pixels at a

time in discrete snapshots, also called pages, which form microscopic cones through the

thickness of the light-sensitive media. Today's holographic media can store over 4.4

million individual pages on a disc.

Today, holographic storage is a WORM technology that relies on light-sensitive

media housed in removable protective cartridges. Although rewritable media and drives

will appear in the next few years, much like the progression from CD-R to CD-RW or

from DVD-R to DVD-RW, experts note that the most likely application for WORM media is

for long-term archiving.


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FIG: STORAGE TECHNIQUE

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

LCD panel (spatial light modulator)

Lenses to focus the laser beams

Lithium-niobate crystal or photopolymer

Charge-coupled device (CCD) camera

Chapter 4

How are holographic drives specified and deployed?
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Ultimately, any discussion of holographic storage deployment is theoretical

because there are no commercial products available today. Beta products are being

evaluated, but manufacturers, like InPhase Technologies Inc., are keeping their beta

users under wrap. Consequently, there is no word from the field about value,

performance, reliability or any application of holographic products. Still, there are

important trends worth noting.

As with most storage devices, the key issues to consider are capacity and data

transfer rates. Although holographic storage capacity and performance are currently

below current disk and tape systems, they compare favorably to existing optical storage

devices. Today, holographic storage media holds 300 GB (uncompressed), and beta

drives from vendors, like InPhase, are expected to utilize that media. The InPhase

product roadmap touts uncompressed capacities up to 1.6 TB over the next few years.

Holographic drives, such as the fledgling InPhase Tapestry 300r, cite data rates of 160

Mbps. Seek time can be a lengthy 250 milliseconds, and you can expect almost two

seconds to load or unload the disk cartridge.

The SLM is a critical part of the overall drive capacity and performance. SLMs in

today's early drives use a 1,000 x 1,000 pixel matrix (1 million bits) to modulate laser

light and encode each data page. In order to increase storage capacity, SLMs must

eventually become finer (offering more bits) and switch faster. This will fit more and

larger data pages on each disk and allow the drive to write and read more data per

second.Early generation holographic drives appear positioned as single-disk external

products connected to the local area network (LAN) or storage area network (SAN). As

an example, the Tapestry 300r is expected to provide SCSI, 4 Gbps Fibre Channel

optical, Gigabit Ethernet, SAS, and iSCSI Ethernet connectivity options, allowing the

drive to reside on a wide range of LAN/SAN architectures. When used with a server,

holographic storage devices will invariably require device drivers that correspond to the

operating system in use.

Optical storage technologies use lasers for noncontact read/write operations, and

holographic drives should also be maintenance free. This is a substantial advantage over

tape drives, which require frequent cleaning to remove accumulations of magnetic

particles from the read/write heads.


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Chapter 5

WORKING OF HDSS

5.1 RECORDING DATA ON MEDIUM

FIG : HOW DATA IS RECORDED ON A MEDIUM


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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. 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.

5.2 READING DATA FROM HOLOGRAM

FIG: HOW DATA IS READ FROM HOLOGRAM

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-
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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.

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

be retrieved quickly and at one time.
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FIG: READING AN OBJECT

5.3 IMPLEMENTATION

A holographic data storage system consists of a recording medium, an optical

recording system, a photo detector array. A beam of coherent light is split into areference beam and a signal beam which are used to record a hologram into the

recording medium. The recording medium is usually a photo refractive crystal.

A hologram is simply the three-dimensional interference pattern of the

intersection of the reference and signal beams are perpendicular to each other. This

interference pattern is imprinted into the crystal as regions of positive and negative

charges. To retrieve the stored hologram, a beam of light that has the same wavelength

and angle of incidence as the reference beam is sent into the crystal and the resulting

diffraction pattern is used to reconstruct the pattern of the signal beam. Many different

holograms may be stored in the same crystal volume by changing the angle of incidence

of reference beam


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FIG: IMPLEMENTATION OF HDD

The most common holographic recording system uses laser light, a beam splitter

to divide the laser light into reference beam and signal beam, various lenses and mirrors

to redirect the light, a photo reactive crystal, and an array of photo detectors around the

crystal to receive the holographic data. To record a hologram, a beam laser light is split

into two beams by a mirror. These two beams then become the reference and signal

beams. The signal beam interacts with an object and the light that is reflected by the

object intersects the reference beam at right angles. The resulting interference patterncontains all the information necessary to recreate the image of the object after suitable


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processing. The interference pattern is recorded on to a photo reactive material and may

be retrieved at a later time by using a beam that is identical to the reference beam. This

is possible because the hologram has the property that if it is illuminated by either of the

beams used to record it, the hologram causes light to be diffracted in the direction of the

second beam that was used to record it, there by recreating the reflected image of the

object if the reference beam was used to illuminate the hologram. So, the reflected must

be transformed into a real image with mirrors and lenses that can be sent to the laser

detector array.

Chapter 6

What is a HOLOGRAM ?

The word Hologram is derived from Greek word Holos meaning Whole and

GRAM meaning Message. A hologram is often described as a 3-D picture.

While a photograph has an actual physical image, a hologram contains

information about size, shape, brightness and contrast of object being recorded .This

information is stored in a very microscopic and complex pattern of interference. The

interference pattern is made possible by the properties of light generated by a LASER.

In order to record the whole pattern, the light used must be highly directional and

must be one of one color. Such light is called coherent. Because the light from a LASER is

one color and leaves the LASER with one wave in perfect one step with all others, it is

perfect for making hologram. When we shine a light on the hologram the information

that is stored as an interference pattern takes the incoming light and re-creates the

original optical wave front that was reflected off the object hence the eyes and brain now

perceives the object as being in front of us once again.

A hologram is a recording of the optical interference pattern that forms at theintersection of two coherent optical beams. Typically, light from a single laser is split into

two paths, the signal path and the reference path.

The beam that propagates along the signal path carries information, whereas the

reference is designed to be simple to reproduce. A common reference beam is a plane

wave: a light beam that propagates without converging or diverging. The two paths are

overlapped on the holographic medium and the interference pattern between the two

beams is recorded.


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A key property of this interferometric recording is that when it is illuminated by a

readout beam, the signal beam is reproduced. In effect, some of the light is diffracted

from the readout beam to reconstruct a weak copy of the signal beam. If the signal

beam was created by reflecting light off a 3D object, then the reconstructed hologram

makes the 3D object appear behind the holographic medium. When the hologram is

recorded in a thin material, the readout beam can differ from the reference beam used

for recording and the scene will still appear.

Chapter 7

MULTIPLEXING

Once one can store a page of bits in a hologram, an interface to a computer can

be made. The problem arises, however, that storing only one page of bits is notbeneficial. Fortunately, the properties of holograms provide a unique solution to this

dilemma. Unlike magnetic storage mechanisms which store data on their surfaces,

holographic memories store information throughout their whole volume. After a page of

data is recorded in the hologram, a small modification to the source beam before it

reenters the hologram will record another page of data in the same volume. This method

of storing multiple pages of data in the hologram is called multiplexing. The thicker the

volume becomes smaller the modifications to the source beam can be.


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Chapter 8

COMPARISION

Major difference between convention recording techniques and holographic

method is the 3-D approach. Traditional optical media uses a single laser beam while in

this technique a single beam is split into two beams.

In conventional methods all the data bits are stored on the surface of a recording

medium but holographic memory will go beneath the surface and use the volume of the

recording medium for storage, instead of only the surface area.

StorageMedium

Access Time DataTransferRate

StorageCapacity

HolographicMemory

2.4 s 10 GB/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

Chapter 9


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9.1 ADVANTAGES

With three-dimensional recording and parallel data readout, holographic

memories can outperform existing optical storage techniques. In contrast to the

currently available storage strategies, holographic mass memory simultaneously offers

high data capacity and short data access time (Storage capacity of about 1TB/cc and

data transfer rate of 1 billion bits/second).

Holographic data storage has the unique ability to locate similar features stored

within a crystal instantly. A data pattern projected into a crystal from the top searches

thousands of stored holograms in parallel. The holograms diffract the incoming light out

of the side of the crystal, with the brightest outgoing beams identifying the address of

the data that most closely resemble the input pattern. This parallel search capability is

an inherent property of holographic data storage and allows a database to be searched

by content.

Because the interference patterns are spread uniformly throughout the material,

it endows holographic storage with another useful capability: high reliability. While a

defect in the medium for disk or tape storage might garble critical data, a defect in a

holographic medium doesn't wipe out information. Instead, it only makes the hologram

dimmer.

No rotation of medium is required as in the case of other storage devices. It can

reduce threat of piracy since holograms cant be easily replicated.

9.2 DISADVANTAGES

Manufacturing cost HDSS is very high and there is a lack of availability of

resources which are needed to produce HDSS. However, all the holograms appear

dimmer because their patterns must share the material's finite dynamic range. In other

words, the additional holograms alter a material that can support only a fixed amount of

change. Ultimately, the images become so dim that noise creeps into the read-out

operation, thus limiting the material's storage capacity.

A difficulty with the HDSS technology had been the destructive readout. The re-

illuminated reference beam used to retrieve the recorded information, also excites the

donor electrons and disturbs the equilibrium of the space charge field in a manner that


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produces a gradual erasure of the recording. In the past, this has limited the number of

reads that can be made before the signal-to -noise ratio becomes too low. Moreover,

writes in the same fashion can degrade previous writes in the same region of the

medium. This restricts the ability to use the three-dimensional capacity of a

photorefractive for recording angle-multiplexed holograms. You would be unable to

locate the data if theres an error of even a thousandth of an inch.

Chapter 10

APPLICATIONS

There are many possible applications of holographic memory. Holographic

memory systems can potentially provide the high speed transfers and large volumes of

future computer system. One possible application is data mining. Data mining is the

processes of finding patterns in large amounts of data. Data mining is used greatly in

large databases which hold possible patterns which cant be distinguished by human

eyes due to the vast amount of data. Some current computer system implement data

mining, but the mass amount of storage required is pushing the limits of current data

storage systems. The many advances in access times and data storage capacity that

holographic memory provides could exceed conventional storage and speedup 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

extremely large amounts of data provided by holographic memory could be utilized in

petaflop architecture. Clearly advances are needed to in more than memory systems,
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but the theoretical schematics do exist for such a machine. Optical storage such as

holographic memory provides a viable solution to the extreme amount of data which is

required for a petaflop computing.

The three main companies involved in developing holographic memory, as of

2002, were InPhase and Polaroid spinoff Aprilis in the United States, and Optware in

Japan. Although holographic memory has been discussed since the 1960s, and has been

touted for near-term commercial application at least since 2001, it has yet to convince

critics that it can find a viable market. As of 2002, planned holographic products did not

aim to compete head to head with hard drives, but instead to find a market niche based

on virtues such as speed of access.

Inphase Technologies, after several announcements and subsequent delays in

2006 and 2007, announced that it would soon be introducing a flagship product. InPhase

went out of business in February 2010 and had its assets seized by the state of Colorado

for back taxes. The company had reportedly gone through $100 million but the lead

investor was unable to raise more capital.

In April 2009, GE Global Research demonstrated their own holographic storage

material that could allow for discs that utilize similar read mechanisms as those found on

Blu-ray Disc players.
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Chapter 11

FUTURE SCOPE

The future of holographic storage is fraught with unknowns. "This technology is

very promising. I've been hearing about it for years," Garrett says. "But at this point, the

No. 1 concerns are [high] cost and [product] immaturity." Experts agree that capacity

and performance will only increase over time, moving from 300 GB to 800 GB and finally

on to 1.6 TB over the next 48 months or so. But the pace of improvements will

ultimately rest heavily on industry acceptance. Given that holographic technology is

currently geared toward a niche in the storage market, it may be years before early

product releases give way to more capable and cost-effective systems that appeal to a

larger storage audience.

Experts also note the possible introduction of "hybrid" holographic media. Just as

magnetic hard drives are starting to incorporate significant quantities of flash or RAM

within the disk, near-term holographic storage media may add some amount of flash

memory in the cartridge to provide a degree of rewritability until a suitable rewritable

media is developed and productized.

Backward compatibility also remains a significant unknown. No tape drive in your

enterprise today is capable of reading a tape written 50 years ago, and the same specter

is in the cards for holographic storage. For example, the InPhase product roadmap

suggests a third generation of holographic drives in roughly four years and promises

backward compatibility with the previous two generations. (Back to first generation in

this case.) Well, then what? If the fifth or sixth or 10th generation drives cannot read the

holographic disks written today, you'll need to either retain the older drive software and

hardware, assuming that it still functions, or rewrite the older disks to the newer media

later -- defeating the purpose of such long retention. "The same corner case that

justifies holographic storage also works against it," Schulz says.

Researchers are confident that technologies will be developed in the next two or

three years to meet these challenges. This DVD-like disc would have a capacity 27 times

greater than the 4.7-GB DVDs available today, and the playing device would have data

rates 25 times faster than today's fastest DVD players.

Chapter 12


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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. 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 HDSS impractical. It will most likely be

used in next generation supercomputers where cost is not as much of an issue. Current

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

market. As computer system evolve, it is, not unreasonable to believe that magnetic

storage will continue to do so. As mentioned earlier, however, these improvements are

not made on the conceptual level. The current storage in a personal computer operateson the same principles used in the first magnetic data storage devices. The parallel

nature of HDSS 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 our computer systems.

BIBLIOGRAPHY

.......www.holopc.com

........www.wikeipedia.com

..........www.computer.howstuffworks.com
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