ContentsContents1. Introduction.2. What is Holographic memory?3. What is HVD?4. Structure of HVD.5. How HVD Works?

I. Writing DataII. Reading Data

6. Advantages of HVD7. How HVD compares with other storage device?8. Conclusion

IntroductionIntroduction

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.

What is Holographic What is Holographic Memory ?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.

Holographic Versatile DiscHolographic Versatile DiscHolographic 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.

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

Holographic Versatile Disc Holographic Versatile Disc structurestructureHolographic Versatile Disc Holographic 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

The HVD System: Writing Data

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.

                                      

      

                                             

     

The HVD System: Writing Data

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.

The HVD System: Writing Data

The HVD System: Writing Data

          

                            

      

            

                                

      

The HVD System: Reading Data

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.

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 .

HVD Compares With Other HVD Compares With Other Storage DeviceStorage Device

  Blu-ray HD-DVD HVD

Initial cost for recordable disc

Approx. $18 Approx. $10 Approx. $120

Initial cost for recorder/player

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

Road Map of HVD

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.

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