optical data storage tatebe

8/2/2019 Optical Data Storage Tatebe

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Optical Data StorageOptical Data Storage

ByBy

Ken TatebeKen Tatebe2004.11.12004.11.1


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OutlineOutline

Basic TechnologyBasic Technology

CD: Properties and CapabilitiesCD: Properties and Capabilities

DVD: Comparison to CDDVD: Comparison to CD Whats makes DVDs better?Whats makes DVDs better?

Comparison to other contemporary dataComparison to other contemporary data

storage technologiesstorage technologies Future directionsFuture directions


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First Optical Storage TechniquesFirst Optical Storage Techniques

Writing systems representthe first optically based datastorage methods, replacingoral records.

Storage Capacity:

~ 0.01 byte / mm2


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2020thth Century: The Compact DiscCentury: The Compact Disc

Patented in 1970 by James T. Russell as aPatented in 1970 by James T. Russell as a

means for durable audio data storage.means for durable audio data storage.

First digital optical data storage; inspired by punchFirst digital optical data storage; inspired by punch

cards and magnetic storage devices.cards and magnetic storage devices. Mass production starts in 1985 by Philips andMass production starts in 1985 by Philips and

Sony.Sony.

Gives practical use to Reed Solomon ErrorGives practical use to Reed Solomon Error

Correction.Correction. Data Density: ~ 1Mbyte/mmData Density: ~ 1Mbyte/mm22


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Tracking and Error CorrectionTracking and Error Correction

Diagonally astigmatic lens coupled withDiagonally astigmatic lens coupled with

quadrant photocell.quadrant photocell.

Difficult to keep focus stable across allDifficult to keep focus stable across all

freq.freq.

1 mm surface spot size due to high NA1 mm surface spot size due to high NA

Reed - Solomon correction codesReed - Solomon correction codes Over-sampled polynomial using data asOver-sampled polynomial using data as

coefficientscoefficients


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DVD: Improvements to CDDVD: Improvements to CD

Feature DVD CD

Substrate Dia./Thick. 120 x 1.2 mm 120 x 1.2 mm

Sides 1 or 2 1

Layers per side 1 or 2 1

Capacity (GB) 4.7, 8.54, 9.4, 17 0.7

Track Pitch (micron) 0.74 1.6

Min pit length (micron) 0.44 0.83

Linear scan velocity 3.6 m/s 1.3 m/s

Laser wavelength 635 nm 780 nm

Numerical Aperture .6 .45

Modulation 8 to 16 8 to 17

Spot Size 1058 nm 1733 nm


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Road to the DVDRoad to the DVD

Innovations:Innovations:

Dual layerDual layer

Increased numerical apertureIncreased numerical aperture

Decreased depth of focusDecreased depth of focus

Signal to noiseSignal to noise

TrackingTracking

Data Density: ~7 MByte/mmData Density: ~7 MByte/mm22


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Dual Layer TechnologyDual Layer Technology

BenefitsBenefits

Increased durabilityIncreased durability

Increased capacityIncreased capacity

DetrimentsDetriments

Decreased S/NDecreased S/N

Decreased data densityDecreased data density


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Numerical ApertureNumerical Aperture

NA = n sin(NA = n sin(/2)/2)

Spot size =Spot size = /NA/NA


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Depth of FocusDepth of Focus

DoF =DoF = /NA/NA22

Determines spacingDetermines spacing

of layersof layers Affects S/N; places anAffects S/N; places an

upper limit on NA.upper limit on NA.


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Noise TolerancesNoise Tolerances

Coma AberrationsComa Aberrations

Laser more stable at -135 db/HzLaser more stable at -135 db/Hz

Eccentricity 100 micron down from 140 micronEccentricity 100 micron down from 140 micron

Surface aberration of 0.033Surface aberration of 0.033 down from 0.07down from 0.07


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Hard drivesHard drives


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Future Data Disc AdvancesFuture Data Disc Advances


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Non-linear UpgradesNon-linear Upgrades

2 Photon absorption to decrease depth2 Photon absorption to decrease depthof field for more layersof field for more layers

Magnetic Super-Resolution: 100 nm spotMagnetic Super-Resolution: 100 nm spotsize.size.

Separate layers by narrow spectralSeparate layers by narrow spectral

response.response. Shorter wavelength (freq. doubled?)Shorter wavelength (freq. doubled?)


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Volumetric StorageVolumetric Storage

K Vector Addressing: a.k.a.K Vector Addressing: a.k.a.

Holographic addressingHolographic addressing

2 beam intersection: issues with reaching2 beam intersection: issues with reaching

diffraction limitsdiffraction limits

Interferometer based path lengthInterferometer based path length

addressingaddressing


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ReferencesReferences

Optical Data Storage.Optical Data Storage. Coufal, Hans, Geoffrey Burr:Coufal, Hans, Geoffrey Burr:International Trends in OpticsInternational Trends in Optics, 2002., 2002.

DVD Focus Control.DVD Focus Control. Lincoln, Bo: Lecture notes.Lincoln, Bo: Lecture notes. Smith, Steven W.Smith, Steven W. The Scientist and Engineers Guide toThe Scientist and Engineers Guide to

Digital Signal Processing.Digital Signal Processing. San Diego: California TechnicalSan Diego: California TechnicalPublishing, 1997.Publishing, 1997. Usbyte.comUsbyte.com Pioneer.co.jpPioneer.co.jp Optical-disk.comOptical-disk.com

Hecht, Eugene.Hecht, Eugene. Optics.Optics. Reading: Addison WesleyReading: Addison WesleyLongman, 1998.Longman, 1998.

Magnetic Super Resolution: Fujitsu.Magnetic Super Resolution: Fujitsu.

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