Holographic data storage is a potential technology in the area of high-capacity data storage currently dominated by magnetic and conventional optical data storage. Magnetic and optical data storage devices rely on individual bits being stored as distinct magnetic or optical changes on the surface of the recording medium. Holographic data storage records information throughout the volume of the medium and is capable of recording multiple images in the same area utilizing light at different angles.

2. Contents
1. Introduction.
2. What is Holographic memory?
3. What is HVD?
4. Structure of HVD.
5. How HVD Works?
I. Writing Data
II. Reading Data
6. Advantages of HVD
7. How HVD compares with other
storage device?
8. Conclusion

3. Introduction
As computer systems continue to become faster, they
will need a way to access larger amounts of data in
shorter periods of time.
Holographic memory is a three-dimensional data
storage system that can stored information at high
density inside the crystal or photopolymer.
Hence holographic storage system has the potential to
became the next storage generation over
conventional storage system.

4. What is 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.
 As current storage techniques such as DVD reach the upper
limit of possible data density (due to the diffraction limited size
of the writing beams), holographic storage has the potential to
become the next generation of storage media.
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 photo
refractive effect in crystals.

5. Holographic Versatile DiscHolographic Versatile Disc
Holographic Versatile Disc (HVD) is an optical disc technology still
in the research stage which would hold up to 3.9 terabyte (TB) of
information.
It employs a technique known as collinear holography, whereby two
lasers, one red and one blue-green, are collimated in a single beam.
The blue-green laser reads data encoded as laser interference fringes
from a holographic layer near the top of the disc while the red laser is
used as the reference beam and to read servo information from a
regular CD-style aluminum layer near the bottom.

6. Holographic Versatile DiscHolographic Versatile Disc
These discs have the capacity to hold up
to 3.9 terabyte (TB) of information,
which is approximately 6,000 times the
capacity of a CD-ROM, 830 times the
capacity of a DVD, 160 times the
capacity of single-layer Blu-ray-Discs,
and about 8 times the capacity of standard
computer hard drives as of 2007.
The HVD also has a transfer rate of
1gigabyte/s

7. Holographic Versatile DiscHolographic Versatile Disc
structurestructure
1. Green writing/reading laser
(532 nm)
2. Red positioning/addressing
laser (650 nm)
3. Hologram (data)
4. Polycarbon layer
5. Photo polymeric layer (data-
containing layer)
6. Distance layers
7. Dichroic layer (reflecting green
light)
8. Aluminum reflective layer
(reflecting red light)
9. Transparent base

8. The HVD System: Writing Data

9. The HVD System: Writing
Data
The process of writing information onto an HVD begins with
encoding the information into binary data to be stored in the
SLM. These data are turned into ones and zeroes represented as
opaque or translucent areas on a "page" -- this page is the image
that the information beam is going to pass through.

10. The HVD System: Writing
Data1. Once the page of data is created, the next step is to fire a laser beam
into a beam splitter to produce two identical beams. One of the beams
is directed away from the SLM -- this beam becomes the reference
beam. The other beam is directed toward the SLM and becomes the
information beam.
2. When the information beam passes through the SLM, portions of the
light are blocked by the opaque areas of the page, and portions pass
through the translucent areas. In this way, the information beam carries
the image once it passes through the SLM.
3. When the reference beam and the information beam rejoin on the same
axis, they create a pattern of light interference -- the holography data.
This joint beam carries the interference pattern to the photopolymer
disc and stores it there as a hologram.

11. The HVD System: Writing
Data

12. The HVD System: Reading
Data

13. The HVD System: Reading
Data
1. 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.
2. Each page of data is stored in a different area of the crystal, based on the
angle at which the reference beam strikes it.
3. During reconstruction, the beam will be diffracted by the crystal to
allow the recreation of the original page that was stored.
4. This reconstructed page is then projected onto the charge-coupled device
(CCD) camera, which interprets and forwards the digital information to a
computer.
5. 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.

14. Advantages of HVDAdvantages of HVD
1. Resistance to damage - If some parts of the medium are damaged, all
information can still be obtained from other parts.
2. Efficient retrieval - All information can be retrieved from any part of
the medium.
3. These discs have the capacity to hold up to 3.9 terabyte (TB) of
information, which is approximately 6,000 times the capacity of a CD-
ROM, 830 times the capacity of a DVD, 160 times the capacity of
single-layer Blu-ray-Discs, and about 48 times the capacity of standard
computer hard drives.
4. The HVD also has a transfer rate of 1 gigabit/s.
5. While reading a page the entire page of data can be retrieved quickly
and at one time .

15. HVD Compares With Other StorageHVD Compares With Other Storage
DeviceDevice
Blu-ray HD-DVD HVD
Initial cost for
recordable
disc
Approx. $18 Approx. $10 Approx. $120
Initial cost for
recorder/play
er
Approx.
$2,000
Approx.
$2,000
Approx. $3,000
Initial storage
capacity
54 GB 30 GB 300 GB (max 3.9 TB)
Read/write
speed
36.5 Mbps 36.5 Mbps 1 Gbps

16. Road Map of HVD

17. ConclusionConclusion
• Capacity increased from 3oo Gbyte to 3.9 TB
• No need to turn over the CD,DVD,HD-DVD,etc.
• Three-dimensional data storage ,store information
in a smaller space and faster data transfer times .
• The HVD playing device would have data rates 25
times faster than today's fastest DVD players.

18. ?