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Doh! New format could store all of Homerís life on one optical disk

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-Department of Physics
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-Imperial Innovations
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Under embargo for
07.00 BST / 14.00 TAIWAN
Monday 27 September 2004

Physicists at Imperial College London are developing a new optical disk with so much storage capacity that every episode of The Simpsons made could fit on just one.

Speaking at the Asia-Pacific Data Storage Conference 2004 in Taiwan today, Dr Peter Török, Lecturer in Photonics in the Department of Physics, will describe a new method for potentially encoding and storing up to one Terabyte (1,000 Gigabytes) of data, or 472 hours of film, on one optical disk the size of a CD or DVD.

All 350 scheduled episodes of The Simpsons, totalling 8,080 minutes of film, could be easily stored on the new disk, dubbed MODS - for Multiplexed Optical Data Storage - by the Imperial College team.

The 1TB disk would be double sided and dual layer, but even a single sided, single layer, MODS disk could hold the Lord of the Rings trilogy 13 times over, or all 238 episodes of Friends. (See Notes to Eds for more comparisons).

MODS disks will not be the first to challenge DVDs domination of the audiovisual optical disk market. BluRay disks, which have five times the capacity of a DVD at 25GB per layer, are expected to be released towards the end of 2005 for the home market.

The Imperial researchers, working closely with colleagues at the Institute of Microtechnology, University of Neuchâtel, Switzerland, and in the Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece, estimate that MODS disks would cost approximately the same to manufacture as an ordinary DVD and that any system playing them would be backwards compatible with existing optical formats - meaning that CDs and DVDs could be played on a MODS system. Dr Török believes that the first disks could be on the shelves between 2010 and 2015 if his team are able to secure funding for further development.

"According to our experimental results, we can optimistically estimate that we will be able to store about one Terabyte per disk in total using our new method," said Dr Török, leader of the research. "This translates to about 250GB per layer, 10 times the amount that a BluRay disk can hold."

The Imperial researchers and colleagues at Neuchâtel and Thessaloniki filed a patent covering their ideas in July 2004.

Under magnification the surface of CDs and DVDs appear as tiny grooves filled with pits and land regions. These pits and land regions represent information encoded into a digital format as a series of ones and noughts. When read back, CDs and DVDs carry one bit per pit, but the Imperial researchers have come up with a way to encode and retrieve up to ten times the amount of information from one pit.

Unlike existing optical disks, MODS disks have asymmetric pits, each containing a step sunk within at one of 332 different angles, which encode the information. The Imperial researchers developed a method that can be used to make a precise measurement of the pit orientation that reflects the light back. A different physical phenomenon is used to achieve the additional gain.

"We came up with the idea for this disk some years ago," says Dr Török. "But did not have the means to prove whether it worked. To do that we developed a precise method for calculating the properties of reflected light, partly due to the contribution of Peter Munro, a PhD student working with me on this project. We are using a mixture of numerical and analytical techniques that allow us to treat the scattering of light from the disk surface rigorously rather than just having to approximate it."

Increasingly manufacturers are looking at miniaturising the size of optical disks, says Dr Török.

"Multiplexing and high density ODS comes in handy when manufacturers talk about miniaturisation of the disks," he says. "In 2002 Philips announced the development of a 3cm diameter optical disk to store up to 1GB of data. The future for the mobile device market is likely to require small diameter disks storing much information. This is where a MODS disk could really fill a niche."

Imperial College Innovations Ltd, the College's wholly owned technology transfer company, managed and helped to prepare the patent application.


For further information, please contact:

Dr Peter Török
Department of Physics
Imperial College London
Tel : +44 (0)20 7594 7753

*Please note Dr Török will be away from College at the conference in Taiwan from 24 September. Please contact Abigail Smith if you wish to reach him in Taiwan.*

Abigail Smith
Imperial College London Press Office
Tel: +44 (0)20 7594 6701
Mob: +44 (0)7803 886248

Notes to Editors:

Dr Török is talking at Asia-Pacific Data Storage Conference 2004 (APDSC'04) at The Ta-Shee Resort, Taoyuan, Taiwan, from 27-29 September 2004.

Calculated capacities for TV and Film on MODS disks

A single layer 250GB MODS disk could hold 118 hours or 7,080 minutes of broadcast quality film. This equates to:

*All 10 series of Friends (238 episodes at 25 minutes each = 5,950 minutes = 99 hours). All 10 series would fit on a MODS 118 hour disk.

*All three seasons of 24 (3 seasons at 3,240 minutes) Would fit on one single sided disk twice.

*The Lord of the Rings Trilogy. Would fit 13 times on one single sided disk.

*Every episode of Only Fools and Horses (2,830 minutes) would fit on single layer disk 2.5 times over.

*Sex and the City (94 35 minute episodes = 3,290 minutes) would fit twice on 250GB single sided disk.

*The Sopranos (65 episodes at 60 mins = 2,100 mins) would fit three times.

*Buffy the Vampire Slayer (144 episodes at 45 mins each = 6,480 minutes / 108 hours) would all fit on one single sided disk.

*The West Wing (113 episodes aired so far (in USA) at 60 mins = 113 hours) would fit on one 250GB single sided disk.

A double sided, double layer 1TB MODS disk could hold 472 hours or 28,320 minutes of broadcast quality film. This equates to:

*Star Trek, Next Generation: all 178 hour-long episodes.

*ER: all 231 episodes so far.

*BUT even a 1TB disk wouldn't be big enough to hold every episode of Eastenders made so far.

(Episode information from, and

Patent detail:

P. Török, M. Salt, P.R.T. Munro, H.-P. Herzig, E.E. Kriezis, C. Rockstuhl - Optical Disk and Reader Therefor, British Patent Application No: 0416649.2

About Imperial College London

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About Imperial College Innovations Ltd

Imperial Innovations is one of the United Kingdoms leading technology transfer companies, having developed an impressive portfolio of over 50 successful technology-based companies since 1997. Imperial Innovations is wholly owned by Imperial College London; a world-renowned centre of academic excellence. Imperial Innovations is committed to the creation of wealth for Imperial College, and the company's mission is to match the outstanding quality of research at Imperial College with excellence in technology transfer.