EP1579429A2 - Optical reading device for writing/reading on/from multi-layer optical disks - Google Patents

Optical reading device for writing/reading on/from multi-layer optical disks

Info

Publication number
EP1579429A2
EP1579429A2 EP02742281A EP02742281A EP1579429A2 EP 1579429 A2 EP1579429 A2 EP 1579429A2 EP 02742281 A EP02742281 A EP 02742281A EP 02742281 A EP02742281 A EP 02742281A EP 1579429 A2 EP1579429 A2 EP 1579429A2
Authority
EP
European Patent Office
Prior art keywords
optical
reading
piezo
layer
electrostriction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02742281A
Other languages
German (de)
French (fr)
Inventor
Eugene Levich
Alexander Libin
Anatolii Dovgan
Sergey Milutin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
D Data Inc
Original Assignee
TriD Store IP LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TriD Store IP LLC filed Critical TriD Store IP LLC
Publication of EP1579429A2 publication Critical patent/EP1579429A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
    • G11B7/13925—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means
    • G11B7/13927—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means during transducing, e.g. to correct for variation of the spherical aberration due to disc tilt or irregularities in the cover layer thickness
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
    • G11B7/1369—Active plates, e.g. liquid crystal panels or electrostrictive elements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
    • G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
    • G11B2007/0013—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage for carriers having multiple discrete layers

Definitions

  • the present invention generally related to an optical reading device for writing /reading on/from multi-layer disks utilizing a light beam from a light source and provided with a device for controlling and correction of the wave front of phase shift of light beam which is produced by changing of thickness in the substrate of information layer.
  • the thickness of substrate changes in transition from one informational layer to another during reading and due to technological deviations of substrate at disk fabrication.
  • Magneto-optical and phase optical carriers such as optical and magneto-optical disks, magnetic disks and magnetic tapes are most popular carriers for digital information. Such carriers were used as information carriers for writing/reading by light beam from laser source. Recently, carriers using fluorescent layers for writing/reading of information were suggested in the related art. Thin film is distributed at the surface of a carrier with preliminary created profile forms a recording layer with a strong fluorescent action.
  • Such optical carriers have exceptional optical properties like optical transparency and significant difference in wavelengths of laser write/excitement beam and reading fluorescent beam.
  • Multi-layer fluorescent disk almost transparent for the laser beam allows developing disks with 10 and more layers.
  • the allowable limit for inter-layer gap should be above 30 ⁇ m, which is necessary to keep the required level of cross-noise from different informational layers of the multi-layer disk. Therefore, only 3 layers of high-density record could be obtained without spherical aberration correction.
  • the number of write/read layers on disk could be increased ten times or more by using a module for detection of the substrate thickness of the record layer and phase corrector for the lens spherical aberration. This solution allows a significant increase of the lens aperture, reduces the write/read wavelength and increases information density, and write/read 10 th informational layers on the disk.
  • An additional problem for the high-density carrier is the focusing of the lens with a high numeric aperture.
  • the design problem of an effective focus sensor having minimum cross-noise from neighbor layers is derived from decreasing focus deepness by inverse square of numeric lens aperture, and cross-interaction of neighbor layers on a focus sensor signal. Focusing sensors realizing algorithm of signal generation by phase methods e.g. synchronized detection, but not amplitude methods have certain advantages.
  • Such a sensor construction could be realized with piezo-ceramic optical element that will produce a periodic phase difference for optical irradiation between central and peripheral lens zones with a property producing unfocusing on a carrier of light beam.
  • a single piezo-ceramic element will allow a high-density multi-layer recording on optical carrier and provide an effective defocusing sensor that will not be sensitive to the amplitude cross-noise from the above and lower informational layers.
  • an optical information reader for writing/reading of multi-layer optical disks utilizing light beam from the light source directed to optical carrier by the lens and receiving reflected or fluorescent light.
  • the optical reader includes a device for receiving reflected fluorescent light and a detector of the disk writing/reading layer which determines the required value of compensation or correction of spherical aberration compared to the calculated one.
  • the writing layer detector controls the reflected or fluorescent light signal obtained from information layer of the carrier.
  • the optical reader also includes also a piezo-ceramic optical element located in a light beam that is directed from the light source to the carrier.
  • This piezo-element has a phase difference between central and peripheral zones that depend on sign and value of voltage applied to it.
  • An optical reader can determine a value and sign of optical aberration with high accuracy.
  • the piezo-ceramic element reduces spherical aberrations to the accepted level at any writing layer and at any radial position of spot on record track. In such a way the average value of spherical aberration and its current value mediated by fluctuation of record layer thickness will be reduced.
  • a piezo-ceramic device reduces aberrations by using the phase differences change between its central and peripheral zones as result of current change of record layer thickness.
  • Fig. 1 is an electrostriction device for the spherical aberration correction. Electrodes are shown by numbers 1 ,2 and 3. Radius Ro» ho.
  • Fig. 2 is an electrostriction device for the focus scanning. Electrodes are shown by numbers 1 ,2 and 3. Radius Ro ⁇ ho.
  • Fig. 3 is a combined electrostriction device. Electrodes are shown by numbers 1 ,2,3 and 4.
  • the present invention relates to the optical information reader for writing/reading of multi-layer optical disks utilizing the light beam from the light source directed to optical carrier by the lens and receiving reflected or fluorescent light from the optical carrier.
  • the present invention comprises an optical reading device for reading, correction of spherical aberration and focusing that can maintains a minimum spherical aberration and a high accuracy lens focusing with high aperture during reading of multi-layer optical high-density disks.
  • the optical reading device includes information reading means illuminating an optical disk with irradiated light beam via an objective lens and detecting a light reflected from the optical disk to read information, thickness record layer and defocusing detector, and an electrostriction device located in the path of a light beam passing from the light source and secured to the lens on moving part of the lens moving device for producing a phase difference between the central and peripheral parts when voltage is applied thereto.
  • the present invention also comprises a device for controlling the lens spherical aberration invoked by deviation of informational layer thickness in comparison with calculation rating of the given lens.
  • a device for controlling the lens spherical aberration invoked by deviation of informational layer thickness in comparison with calculation rating of the given lens are described US Patent No. 5513153 containing titanium or tin oxide and divided into central and peripheral compartments.
  • the electrostriction devices in the '153 patent are incorporated herein in their entirety.
  • Transparent electrodes are introduced in such medium.
  • Light beam phase difference providing the lens focal point move or the convergence of light beams in the lens focus could be obtained by application of differential voltage to central and peripheral parts of the electrodes.
  • Additional high frequency 'scanning' or phase difference formation for electrostriction device can be utilized for the detection of spherical aberration and focusing.
  • ⁇ cf ⁇ r 4 + ⁇ 2 r 6 + ⁇ 3 r 8
  • 2-coordinate actuator reducing the focusing error is sing as lens device control in focus direction.
  • Electrostriction device used for the beam dephasing by formulas (1) or (2) can work as spherical aberration control device. It is necessary to reside the electrode system in such a way that phase gradient was achieving a necessary value.
  • the dephasing at the spherical aberration correction will be up to 2-3 ⁇ in the range 0-100 Hz because of an electrostriction element is an executive mechanism if the phase difference due to base focusing signals less then O.l ⁇ at frequencies more 10 KHz.
  • One central and one peripheral electrode is enough for the support of defocusing phase difference. At least 2 peripheral electrodes are necessary for spherical aberration phase difference to maintain bend of the function of phase difference at the maximum (minimum), which is not necessary for the defocusing phase difference.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Head (AREA)
  • Optical Recording Or Reproduction (AREA)

Abstract

An optical information reader for writing/reading of multi-layer optical disks utilizing light beam from the light source directed to optical carder by the lens and receiving reflected or fluorescent light is described. An optical reader includes the device for the reception of reflected of fluorescent light and the detector of the disk writing/reading layer with the aim to determine a required value of compensation or correction of spherical aberration compare to the calculated one. Optical reader includes also a piezo-ceramic optical element (1, 2, 3, 4) resided in a light beam that is directed from light source to the carder. This piezo-element has a phase difference between central (1, 2) and peripheral (3, 4) zones that depend on sign and value of voltage applied to it. A piezo-ceramic device reduces aberrations by using the phase differences change between its central and peripheral zones as result of current change of record layer thickness.

Description

OPTICAL READING DEVICE FOR WRITING/READING ON/FROM MULTI-LAYER OPTICAL DISKS
FIELD OF THE INVENTION
The present invention generally related to an optical reading device for writing /reading on/from multi-layer disks utilizing a light beam from a light source and provided with a device for controlling and correction of the wave front of phase shift of light beam which is produced by changing of thickness in the substrate of information layer.
The thickness of substrate changes in transition from one informational layer to another during reading and due to technological deviations of substrate at disk fabrication.
BACKGROUND OF THE INVENTION
Magneto-optical and phase optical carriers such as optical and magneto-optical disks, magnetic disks and magnetic tapes are most popular carriers for digital information. Such carriers were used as information carriers for writing/reading by light beam from laser source. Recently, carriers using fluorescent layers for writing/reading of information were suggested in the related art. Thin film is distributed at the surface of a carrier with preliminary created profile forms a recording layer with a strong fluorescent action.
Such optical carriers have exceptional optical properties like optical transparency and significant difference in wavelengths of laser write/excitement beam and reading fluorescent beam. Multi-layer fluorescent disk almost transparent for the laser beam allows developing disks with 10 and more layers.
Informational capacity of the disk increases proportionally to the number of writing layers with practically the same dimensions of the disk. Reading lens designed for limited thickness of transparent base of informational layer that create difficulties for reading of such disks using traditional optics. Thickness change limit is proportional to wavelength and inverse proportional to the 4th degree of numeric lens aperture. For example, for wavelength 650 nm and NA=0.5 the limit will be ±50 μm.
At the same time, the allowable limit for inter-layer gap should be above 30 μm, which is necessary to keep the required level of cross-noise from different informational layers of the multi-layer disk. Therefore, only 3 layers of high-density record could be obtained without spherical aberration correction.
The number of write/read layers on disk could be increased ten times or more by using a module for detection of the substrate thickness of the record layer and phase corrector for the lens spherical aberration. This solution allows a significant increase of the lens aperture, reduces the write/read wavelength and increases information density, and write/read 10th informational layers on the disk.
An additional problem for the high-density carrier is the focusing of the lens with a high numeric aperture. The design problem of an effective focus sensor having minimum cross-noise from neighbor layers is derived from decreasing focus deepness by inverse square of numeric lens aperture, and cross-interaction of neighbor layers on a focus sensor signal. Focusing sensors realizing algorithm of signal generation by phase methods e.g. synchronized detection, but not amplitude methods have certain advantages.
Such a sensor construction could be realized with piezo-ceramic optical element that will produce a periodic phase difference for optical irradiation between central and peripheral lens zones with a property producing unfocusing on a carrier of light beam.
Therefore, a single piezo-ceramic element will allow a high-density multi-layer recording on optical carrier and provide an effective defocusing sensor that will not be sensitive to the amplitude cross-noise from the above and lower informational layers.
SUMMARY OF THE INVENTION According to the present invention, an optical information reader for writing/reading of multi-layer optical disks utilizing light beam from the light source directed to optical carrier by the lens and receiving reflected or fluorescent light is provided. The optical reader includes a device for receiving reflected fluorescent light and a detector of the disk writing/reading layer which determines the required value of compensation or correction of spherical aberration compared to the calculated one. The writing layer detector controls the reflected or fluorescent light signal obtained from information layer of the carrier.
The optical reader also includes also a piezo-ceramic optical element located in a light beam that is directed from the light source to the carrier. This piezo-element has a phase difference between central and peripheral zones that depend on sign and value of voltage applied to it. An optical reader can determine a value and sign of optical aberration with high accuracy. The piezo-ceramic element reduces spherical aberrations to the accepted level at any writing layer and at any radial position of spot on record track. In such a way the average value of spherical aberration and its current value mediated by fluctuation of record layer thickness will be reduced.
A piezo-ceramic device reduces aberrations by using the phase differences change between its central and peripheral zones as result of current change of record layer thickness.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig, 1 is an electrostriction device for the spherical aberration correction. Electrodes are shown by numbers 1 ,2 and 3. Radius Ro» ho. Fig. 2 is an electrostriction device for the focus scanning. Electrodes are shown by numbers 1 ,2 and 3. Radius Ro~ ho.
Fig. 3 is a combined electrostriction device. Electrodes are shown by numbers 1 ,2,3 and 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Briefly stated, the present invention relates to the optical information reader for writing/reading of multi-layer optical disks utilizing the light beam from the light source directed to optical carrier by the lens and receiving reflected or fluorescent light from the optical carrier.
The present invention comprises an optical reading device for reading, correction of spherical aberration and focusing that can maintains a minimum spherical aberration and a high accuracy lens focusing with high aperture during reading of multi-layer optical high-density disks.
Preferably, the optical reading device includes information reading means illuminating an optical disk with irradiated light beam via an objective lens and detecting a light reflected from the optical disk to read information, thickness record layer and defocusing detector, and an electrostriction device located in the path of a light beam passing from the light source and secured to the lens on moving part of the lens moving device for producing a phase difference between the central and peripheral parts when voltage is applied thereto.
The present invention also comprises a device for controlling the lens spherical aberration invoked by deviation of informational layer thickness in comparison with calculation rating of the given lens. Useful electrostriction or piezo-optical devices the PLZT medium, are described US Patent No. 5513153 containing titanium or tin oxide and divided into central and peripheral compartments. The electrostriction devices in the '153 patent are incorporated herein in their entirety. Transparent electrodes are introduced in such medium. Light beam phase difference providing the lens focal point move or the convergence of light beams in the lens focus could be obtained by application of differential voltage to central and peripheral parts of the electrodes.
Additional high frequency 'scanning' or phase difference formation for electrostriction device can be utilized for the detection of spherical aberration and focusing.
Base defocusing signal used for synchronized focus detection sensor formation suggested at high frequency dephasing of light beam using the law Δφ=a0r2 (1). That is different from the US Patent 5513158 where electrostriction element used for the fine adjustment of the lens focus point. At high frequency light beam dephasing by the law Δφcf =αιr4 +α2r6 +α3r8 (2) the base signal for the control of the beam stigmaticity is introduced for the synchronized detection sensor formation by spherical aberration deviation. 2-coordinate actuator reducing the focusing error is sing as lens device control in focus direction.
Electrostriction device used for the beam dephasing by formulas (1) or (2) can work as spherical aberration control device. It is necessary to reside the electrode system in such a way that phase gradient was achieving a necessary value.
The dephasing at the spherical aberration correction will be up to 2-3 λ in the range 0-100 Hz because of an electrostriction element is an executive mechanism if the phase difference due to base focusing signals less then O.lλ at frequencies more 10 KHz.
One central and one peripheral electrode is enough for the support of defocusing phase difference. At least 2 peripheral electrodes are necessary for spherical aberration phase difference to maintain bend of the function of phase difference at the maximum (minimum), which is not necessary for the defocusing phase difference.

Claims

What is claimed is:
1. An optical reading device for writing/reading on/from multi-layer optical disks comprising: an information reading means for illuminating a carrier with light via an objective lens and light detecting means for reading information from said carrier; a defocusing detector; and an electrostriction device located in the pathway of said light beam, said electrostriction device secured to said objective lens and fixed to a lens moving device.
2. The optical reading device of Claim 1 , including a thickness record layer; said thickness record layer and said defocusing detector providing correction of spherical aberration and controlling said reflected light from said information carrier.
3. The optical reading device of Claims 1 and 2, wherein said electrostriction device is a piezo-ceramic element, said piezo-ceramic element produces a phase difference between the central and peripheral zones when voltage is applied to said piezo-ceramic optical element.
4. The optical recording device of any of the proceeding claims, wherein said electrostriction device includes electrodes located within said central and peripheral zone of said electrostriction device.
5. The optical recording device of Claim 1 , wherein said lens moving device is a 2 coordinate actuator for reducing focusing error.
6. The optical recording device of Claim 1 , wherein said carrier is in a form of disc, tape or card.
EP02742281A 2001-06-25 2002-06-25 Optical reading device for writing/reading on/from multi-layer optical disks Withdrawn EP1579429A2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US30005501P 2001-06-25 2001-06-25
US300055P 2001-06-25
PCT/US2002/019979 WO2003001512A2 (en) 2001-06-25 2002-06-25 Optical reading device for writing/reading on/from multi-layer optical disks

Publications (1)

Publication Number Publication Date
EP1579429A2 true EP1579429A2 (en) 2005-09-28

Family

ID=23157510

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02742281A Withdrawn EP1579429A2 (en) 2001-06-25 2002-06-25 Optical reading device for writing/reading on/from multi-layer optical disks

Country Status (5)

Country Link
EP (1) EP1579429A2 (en)
JP (1) JP2005508559A (en)
CN (1) CN101366085A (en)
AU (1) AU2002315429A1 (en)
WO (1) WO2003001512A2 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9275671B2 (en) 2011-06-09 2016-03-01 Case Western Reserve University Optical information storage medium

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5835458A (en) * 1994-09-09 1998-11-10 Gemfire Corporation Solid state optical data reader using an electric field for routing control
US6044056A (en) * 1996-07-30 2000-03-28 Seagate Technology, Inc. Flying optical head with dynamic mirror
US6246650B1 (en) * 1996-12-18 2001-06-12 Sony Corporation Method and apparatus for high speed data reproduction

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO03001512A3 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9275671B2 (en) 2011-06-09 2016-03-01 Case Western Reserve University Optical information storage medium

Also Published As

Publication number Publication date
WO2003001512A2 (en) 2003-01-03
AU2002315429A8 (en) 2008-11-20
AU2002315429A1 (en) 2003-01-08
WO2003001512A3 (en) 2008-10-23
JP2005508559A (en) 2005-03-31
CN101366085A (en) 2009-02-11

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