2. Contents
1. Introduction.
2. What is Holographic memory?
3. What is HVD?
4. Basic Principle.
5. Structure of HVD.
6. Components of HVD.
7. Spatial Light Modulator
8. How HVD Works?
i. Recording Data.
ii. Writing Data.
9. Comparison.
10. Advantages of HVD.
11. Disadvantages of HVD.
12. Possible Applications.
13. Interesting Facts.
14. 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
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.
Conventional memories use only the surface to store the data. But
holographic data storage systems use the volume to store data. It has
more advantages than conventional storage systems. It is based on the
principle of holography.
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
5. Holographic 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 Disc
These discs have the capacity to hold up
to 3.9 terabyte (TB) of information,
which is approximately 5800 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. BASIC PRINCIPLE
A hologram is a block or sheet of photosensitive material which
records the diffraction 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 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 and 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.
8.
9. HVD Structure
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
10. BASIC COMPONENTS OF HVD
BLUE-GREEN ARGON LASER
POLARIZING BEAM SPLITTERS
MIRRORS TO DIRECT THE LASER BEAMS
SPATIAL LIGHT MODULATOR (SLM)
LENSES TO FOCUS THE LASER BEAMS
PHOTO POLYMER
CHARGE-COUPLED DEVICE (CCD )
11. In a holographic memory device, a laser beam is split in two, and the
two resulting beams interact in a crystal medium to store a
holographic recreation of a page of data.
12. SPATIAL LIGHT MODULATOR (SLM)
Translates electronic data (0's and 1's)
into optical pattern of light and dark
pixels.
Data is arranged in an array similar to
a checkerboard of usually 1M (million)
bits.
By varying the angle of the reference
beam, wavelength or media position,
many holograms can be stored in the
same volume of storage material.
13. WORKING OF HVD
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.
14. 1. 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.
15.
16. 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.
17.
18. COMPARISON
Parameters DVD BLU-RAY HVD
Capacity 4.7 gb 25 gb 3.9 tb
Laser wave length 650 nm 405 nm 532 nm
(red) (blue) (green)
Disc diameter 120 mm 120 mm 120 mm
Hard coating no yes yes
Data transfer rate (raw data) 11.08 mbps 36 mbps 1 gbps
Data transfer rate (audio/video) 10.08 mbps 54 mbps 1 gbps
20. Advantages 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 .
21. DISADVANTAGES OF HVD
Manufacturing cost HVD is very high and there is a
lack of availability of resources which are needed
to produce HVD.
A difficulty with the HVD 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 produces a gradual erasure of the
recording.
You would be unable to locate the data if there’s an
error of even a thousandth of an inch.
22. POSSIBLE APPLICATIONS
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 can’t be distinguished by human
eyes due to the vast amount of data.
The many advances in access times and data storage
capacity that holographic memory provides could exceed
conventional storage and speedup data mining
considerably
Holographic Versatile Disc (HVD) is an optical disc
technology still in the research stage which would hold up
to 3.9 terabytes (TB) of information
23. INTERESTING FACTS
It has been estimated that the books in the U.S. Library of
Congress, the largest library in the world , could be stored on six
HVDs.
The pictures of every landmass on Earth - like the ones shown in
Google Earth - can be stored on two HVDs.
With MPEG4 ASP encoding, a HVD can hold anywhere between
4,600-11,900 hours of video, which is enough for non-stop playing
for a year.
24. Conclusion
Capacity increased from 3.00GB 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.
