holographic memory system

By Sanket Mudgal

Future Technology

What is HolographyHolography is a technique which enables 

three-dimensional images to be made. It involves the use of a laser, interference, diffraction, light intensity recording and suitable illumination of the recording.

The image changes as the position and orientation of the viewing system changes in exactly the same way as if the object were still present, thus making the image appear three-dimensional.

Who invented holography?Dennis Gabor  was a 

Hungarian-British

electrical engineer and physicist, most notable for inventing holography, for which he later received the 1971 Nobel Prize in Physics

What is Holographic Data Storage?Three dimensional or “holographic” data storage involves using the entire media for storage, not just a few layers like we currently use today.

The process is accomplished by using two laser beams, instead of one, to write data to the disk.

1. The object is converted into binary code of 1’s and 0’s like we use today.

2. Next, the 1’s and 0’s are converted into a matrix of light and dark squares.

How Does Holographic Data Storage Work?

How Does Holographic Data Storage Work?3. Those light and dark squares are then

electronically sent to a spatial light modulator (SLM).

4. The laser beam then shines through the spatial light modulator (SLM).

5. Pixels of the spatial light modulator filter (block or allow) the light thus encoding the data into the laser beam.

SLM

Objective Lens

Cover LayerRecording LayerReflective Layer

Inner: InformationOuter: Reference

How Does Holographic Data Storage Work?

Diffracted informationbeam (page data)

Diffracted referencebeam (modulated)

Recorded Hologram

How Does Holographic Data Storage Work?

HVD Disk Structure A green and red laser beam are collimated in a single beam.

The green laser reads data encoded as laser interference fringes from a holographic layer near the top of the disc.

A red laser is used as the reference beam to read servoinformation from a regular CD-style aluminium layer near the bottom.

Red - 650 nmGreen – 532 nm

HDV Recording MediaMany disk prototypes have been looked at over the years, however, the industry standard has now accepted having the HVD disk include a reflective layer in order to be backward compatible and to assist with tracking of the write beam. Di-isobutylacrylamide

(DBA)

A simplified HVD system consists of the following main components:•Blue or green laser (532-nm wavelength in the test system)

•Beam splitter/merger

•Mirrors

•Spatial light modulator (SLM)

•CMOS sensor

•Photopolymer recording medium

CollinearTM HolographyRecording Process

Media

Lens

SLM

Information Pattern

Reference Pattern

Reconstruction Process

Media

Reconstructed

SLM

Beam SplitterLens

Reference Pattern

Reflective Layer

Collinear Holography

Why the Interest in Holographic Data Storage?Increased storage capacity

Increased read/write speed

Longer storage life

Security

Increased CapacityIn today’s world, digital media is becoming

more and more common and is requiring more storage to meet the new demands. More industries are now using digital storage than ever before.

200 DVD’s can fit on one 1 TB holographic disk with a future capacity of 6 terabytes.

Increased CapacityIBM's test platforms can store up to 390

bits per square micron (a micron is a millionth of a metre). DVDs, by contrast, have a storage density of about five bits per square micron.

  DVD DVD Blu-Ray Blu-Ray HVDNumber of Layers Single Dual Single Dual  200+/-Recording Capacity 4.7GB 9.4GB 25GB 50GB 1TBData Transfer Rate 11.08Mb/s 11.08Mb/s 36Mb/s 36Mb/s 1GB/s

Interesting FactsIt has been estimated that all the books in the U.S.

Library of Congress, could be stored on six (6) HVD's.

The pictures of every landmass on Earth (Google Earth for example) can be stored on two (2) HVD's.

With MPEG4 ASP encoding, a HVD can hold between 4,600 to 11,900 hours of video, which is enough for non-stop playing for a year.

Increased SpeedHolography allows a million bits of

data to be written and read out in single flashes of light, enabling data transfer rates as high as a billion bits per second (fast enough to transfer a DVD movie in about 30 seconds).

Why Is It So Fast?

Longer Storage LifeHVD’s have an estimated archival life

expectancy of at least 50 years or more compared to CD/DVD archival life of 2 to 5 years (even though published life expectancies are often cited as 10 to 25 years or longer for optical media, it depends on the storage conditions and quality of the disks).

CollinearTM Holography SecurityHVD storage also offers interesting possibilities for data protection. For mass production, holographic media can be replicated very efficiently in one simultaneous transfer from a master. But once written, the replicated discs cannot be used as masters for further copying.

By adjusting one of its laser beams, Collinear technology can provide a physical level of on-disk encryption during recording and reading, which holds great promise for digital rights management and other applications requiring high levels of security.

Why is it taking so long?Low cost materials needed to come available which are just now happening due to other industries utilizing new technology.

Development of needed components, in fields outside the storage industry, have brought the cost down making it financially viable to proceed.

Why is it taking so long?Green lasers now used in the medical,

cable TV, and printing industries are attractive recording sources due to their small size, ruggedness and low cost.

Digital micro-mirror devices appearing in new types of displays are ideal spatial light modulators (SLM). This overhead projector for instance uses a SLM.

Why is it taking so long?The CMOS active pixel detector arrays

emerging in digital photography exhibit the rapid access and data transfer properties required for holography. CMOS sensors were originally proposed for the detection of visible light in cameras. In the holography field, they can detect the light patterns that are stored on the disks.

Key Technological Partners

Sources: The Economist, Holographic data storage, Jul 31, 2003, http://

www.economist.com/node/1956881 General Electric Global Research InPhase Technologies, Longmont, Colorado,

http://www.inphase-technologies.com/ Wikipedia – Holographic Data Storage, http://

en.wikipedia.org/wiki/Holographic_data_storage Bell Laboratories Physical Sciences Research, http://

www.bell-labs.com/org/physicalsciences/projects/hdhds/1.html How Holographic Memory Will Work by Kevin Bosner. http://

computer.howstuffworks.com/holographic-memory1.htm Optware Corporation of America, Longmont, Colorado, http://

www.thic.org/pdf/Jul05/optware.mdeese.050719.pdf Technology Review, July 2010, http

://www.technologyreview.com/blog/mimssbits/25418/

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