WO2006035348A1 - Dispositif de balayage optique - Google Patents

Dispositif de balayage optique Download PDF

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Publication number
WO2006035348A1
WO2006035348A1 PCT/IB2005/053070 IB2005053070W WO2006035348A1 WO 2006035348 A1 WO2006035348 A1 WO 2006035348A1 IB 2005053070 W IB2005053070 W IB 2005053070W WO 2006035348 A1 WO2006035348 A1 WO 2006035348A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
scanning device
record carrier
radiation beam
optical scanning
Prior art date
Application number
PCT/IB2005/053070
Other languages
English (en)
Inventor
Bernardus H. W. Hendriks
Stein Kuiper
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2006035348A1 publication Critical patent/WO2006035348A1/fr

Links

Classifications

    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording 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
    • G11B7/12Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1398Means for shaping the cross-section of the beam, e.g. into circular or elliptical cross-section
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording 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
    • G11B7/004Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045Recording
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording 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
    • G11B7/004Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/005Reproducing

Definitions

  • the present invention relates to an optical scanning device for scanning an optical record carrier. More specifically, but not exclusively, it relates to an optical scanning device capable of reading information from and writing information to an information layer on the optical record carrier.
  • optical storage In optical storage, a radiation beam is incident on an information layer on the optical record carrier. Reading and writing information to and from the information layer place different requirements on the radiation spot used to scan the optical record carrier.
  • optical record carriers can include Compact Discs (CDs) and Digital Versatile Discs (DVDs).
  • the radiation spot size determines the mark size that is readable. It is therefore desirable that the spot size is small, so as to allow the reading of small mark sizes on optical record carriers having a high information density. Furthermore, the smaller the spot size, the less likelihood of crosstalk.
  • the intensity distribution of the optical beam incident on the lens system within the optical scanning device is relatively flat.
  • the radiation beam has a high rim intensity.
  • the rim intensity is the relative intensity of the beam at the edge of the entrance pupil of the objective lens system compared to the intensity along the optical axis.
  • the radiation spot size is less critical.
  • the radiation sources are typically lasers
  • the lifetime of the laser can be extended if the light path between the laser and the record carrier is efficient as it is possible to operate the laser at lower drive currents to generate the required radiation intensity incident on the record carrier.
  • writing mode it is mainly the central part of the radiation spot that is used. This central part of the beam has the highest intensity and therefore produces the highest temperature incident on the record carrier. Accordingly, to have the maximum radiation power incident on the record carrier, the rim intensity must be low (typically 60-70% of the central peak intensity) in order to achieve the required coupling efficiency.
  • the rim intensity of the radiation beam is generally a compromise.
  • a rim intensity is chosen that is generally not optimum for reading or writing.
  • the optical scanning device it would be desirable for the optical scanning device to be capable of switching between a low rim intensity situation when writing information to the optical record carrier, to a high rim intensity situation when reading information from the optical record carrier.
  • JP2000356792 discloses an optical clement capable of controlling the quantity of radiation transmitted in an optical system. However, only the quantity of the radiation transmitted can be changed using the optical element disclosed.
  • an optical scanning device for an optical record carrier, said device including a radiation source for generating a radiation beam to be scanned across the record carrier and optical elements for directing the beam to form a spot on a layer for carrying information on the optical record carrier, said optical elements including a cell comprising at least two immiscible fluids having different transmission characteristics, a first fluid being controllably movcablc into and out of the optical path of the radiation beam such that the intensity of the radiation beam is controllably changed from a first configuration, suitable for writing information to the information layer on the optical record carrier, to a second configuration suitable for reading information from the information layer on the optical record carrier.
  • Figure 1 is a schematic diagram of a typical optical scanning system suitable for incorporating a rim intensity switch in accordance with one form of the invention
  • Figure 2a is a schematic diagram showing a rim intensity switch in situation in a simplified light path optimized for writing information to an information layer on an optical record carrier, in accordance with one form of the invention.
  • Figure 2b is a schematic diagram showing a rim intensity switch in situation in a simplified light path optimized for reading information from an information layer on an optical record carrier, in accordance with one form of the invention.
  • Figure 1 shows elements of an optical scanning device, arranged in accordance with an embodiment of the invention, including an optical head for scanning an optical record carrier 2.
  • the record carrier is in the form of an optical disk comprising a transparent layer 3, on one side of which an information layer 4 is arranged.
  • the side of the information layer facing away from the transparent layer is protected from environmental influences by a protection layer 5.
  • the side of the transparent layer facing the device is called the entrance face 6.
  • the transparent layer 3 acts as a substrate for the record carrier by providing mechanical support for the information layer.
  • the transparent layer may have the sole function of protecting the information layer, while the mechanical support is provided by a layer on the other side of the information layer, for instance by the protection layer 5 or by a further information layer and a transparent layer connected to the information layer 4.
  • Information may be stored in the information layer 4 of the record carrier in the form of optically detectable marks arranged in substantially parallel, concentric or spiral tracks, not indicated in Figure 1.
  • the marks may be in any optically readable form, e.g. in the form of pits, or areas with a reflection coefficient or a direction of magnetisation different from their surroundings, or a combination of these forms.
  • the scanning device 1 comprises a radiation source in the form of a semiconductor laser 9 emitting a radiation beam 7.
  • the radiation beam is used for scanning the information layer 4 of the optical record carrier 2.
  • a beam splitter 13 reflects the diverging radiation beam 12 on the optical path towards a collimator lens 14, which converts the diverging beam 12 into a collimated beam 15.
  • the collimated beam 15 is incident on a transparent electro-optical element 49, which modifies the wavefront of the collimated beam.
  • the beam 17 from the electro-optical element 49 is incident on an objective system 18.
  • the objective system may comprise one or more lenses and/or a grating.
  • the objective system 18 has an optical axis 19.
  • the objective system 18 changes the beam 17 to a converging beam 20 incident on the entrance face 6 of the record carrier 2.
  • the objective system has a spherical aberration correction characteristic adapted for passage of the radiation beam through the thickness of the transparent layer 3.
  • the converging beam 20 forms a spot 21 on the information layer 4.
  • Radiation reflected by the information layer 4 forms a diverging beam 22, transformed into a substantially collimated beam 23 by the objective system 18 and subsequently into a converging beam 24 by the collimator lens 14.
  • the beam splitter 13 separates the forward and reflected beams by transmitting at least part of the converging beam 24 towards a detection system 25.
  • the detection system captures the radiation and converts it into electrical output signals 26 which are processed by signal processing circuits 27, 29 and 31 which are located in the scanning device separately from the optical head 1.
  • a signal processor 27 converts these output signals to various other signals.
  • One of the signals is an information signal 28, the value of which represents information read from the information layer 4.
  • the information signal is processed by an information processing unit for error correction 29.
  • Other signals from the signal processor 27 are the focus error signal and radial error signal 30.
  • the focus error signal represents the axial different in height between the spot 21 and the information layer 4.
  • the radial error signal represents the distance in the plane of the information layer 4 between the spot 21 and the centre of a track in the information layer to be followed by the spot.
  • the focus error signal and the radial error signal are fed into a servo circuit 31 , which converts these signals to a focus error signal for controlling a mechanical focus actuator (not shown) in the optical head and a tracking error signal 32 for controlling the electro-optical element 16, respectively.
  • the mechanical focus actuator controls the position of the objective system 18 in the focus direction 33, thereby controlling the actual position of the spot 21 such that it coincides substantially with the plane of the information layer 4.
  • a further mechanical actuator such as a radially movable arm, alters the position of the optical head 1 in a radial direction 34 of the disk 2, thereby coarsely controlling the radial position of the spot 21 to lie above a track to be followed in the information layer 4.
  • the tracks in the record carrier 2 run in a direction perpendicular to the plane of Figure 1.
  • FIGS 2a and 2b show an clcctrowetting cell 49 comprising two immiscible liquids 50, 51 contained within a cavity 53.
  • the cavity 53 is formed from a cylinder 54 of conductive material coated with a layer of insulating material 55.
  • the inner side of the cylinder is provided with a fluid contact layer 56.
  • the conductive cylinder 54 forms a common first electrode for the immiscible liquids 50, 51.
  • the second electrode 57 comprises an annular conductive layer 58 having a central transparent area for passing radiation. It may also be a transparent conducting layer (such as ITO) of any shape.
  • the first immiscible liquid 50 has a refractive index nl and the second immiscible liquid 51 has a refractive index n2, where nl and n2 are substantially equal.
  • liquid 50 may be an oil and liquid 51 may be water.
  • the cell need not contain immiscible liquids but any immiscible fluids capable of performing similar functions may be used.
  • liquids other than oils and water performing the same function may be considered.
  • a surface 59 between the immiscible liquids will form and can be controlled by application of a voltage to the cylinder 54. It will be appreciated that the level of voltage required to control the surface between the liquids will depend on the two liquids 50, 51 chosen. The shape and curvature of the surface 59 can be changed using controllable voltage sources (not shown).
  • Figures 2a and 2b show two desirable configurations for the surface formed between the two immiscible liquids 50, 51.
  • the voltage is applied to the cylinder 54 such that the second immiscible liquid is removed from the optical path of the radiation emitted by the radiation source and transmitted through the objective lens system and incident on the optical record carrier 2.
  • Figure 2a is a schematic diagram of the system in the optimum mode for writing information to the information layer 4. That is to say the light efficiency of the radiation source 9 is high but the corresponding rim intensity is low. As in writing mode maximum coupling efficiency is required, the elcctrowetting cell 49 must not lead to significant transmission losses. Accordingly, the voltage applied to the conductive cylinder 54 acts so as to remove the low transmission liquid 51 from the optical path.
  • FIG. 2b shows the system in the optimum mode for reading information from the information layer 4 of the optical record carrier 2.
  • a relatively lower radiation beam power is required, whilst the rim intensity of the beam should be preferably higher.
  • a voltage applied to the conductive cylinder 54 causes a meniscus 59 to form between the liquids 50, 51 in the optical path of the optical scanning system.
  • the liquid with low transmission properties is now interposed between the radiation source 9 and the optical record carrier 2.
  • the thickness of the low transmission liquid 51 is greater at the optical axis (i.e. the centre of the radiation beam 7) and as a result, the centre intensity of the radiation beam 7 will be more significantly reduced in comparison with the rim intensity of the radiation beam. As a result, the rim intensity of the radiation beam will increase at the expense of a lower overall transmission. Accordingly, in reading mode more radiation source power is required when the low transmission liquid is present in the optical path than in the writing mode, as per Figure 2a. Advantageously, a higher laser power gives rise to a lower laser noise, so this additional requirement is acceptable. It will be appreciated that a difference of ⁇ 0.02 in transmissity of the liquids
  • the shape of the meniscus 60 is not critical.
  • the meniscus shown in the diagrams is indicative only. Other shapes of meniscus achieved by varying the voltage applied to the conductive cylinder may be considered.
  • changing the liquids 50, 51 in the electrowctting cell 49 enables other characteristics of the overall transmissivity of the optical scanning device to be altered.
  • changing the position and application of the voltage to the elcctrowetting cell will change to shape of the meniscus between the liquids 50, 51 which may again change the transmission properties of the optical scanning device.
  • electrowetting cell 49 may contain more than two immiscible liquids in order to further control the transmission characteristics of the radiation incident on the information layer of the optical record carrier.
  • immiscible liquids may be contained within the electrowetting cell 49 in order to further control the transmission characteristics of the radiation incident on the information layer of the optical record carrier.
  • the foregoing refers to laser radiation, it will be appreciated that any suitable form of electromagnetic radiation may be used and the invention is not limited to visible radiation.

Abstract

L'invention concerne un dispositif de balayage optique (1) destiné à lire des informations provenant d'un support d'enregistrement optique (2) ou de lire des informations se trouvant sur un tel support, notamment un CD ou un DVD. Le dispositif comporte deux modes, un mode de lecture et un mode d'écriture et peut être commuté électriquement entre les deux modes afin de fournir un système dans lequel les paramètres optimaux du dispositif optique puissent être utilisés pour lire et écrire. Le mode d'écriture nécessite une efficacité de couplage maximale entre le rayonnement incident (12) et le support d'enregistrement (2) et une faible intensité de bord du faisceau de rayonnement. Le mode de lecture nécessite une intensité de bord maximale mais une puissance de rayonnement incidente faible. Selon l'invention, une cellule est placée sur le trajet optique du système, cette cellule (49) contenant un fluide (51) pouvant être déplacée dans ou hors du trajet optique du rayonnement afin de modifier les caractéristiques du rayonnement incident en conséquence.
PCT/IB2005/053070 2004-09-28 2005-09-19 Dispositif de balayage optique WO2006035348A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP04104711 2004-09-28
EP04104711.9 2004-09-28

Publications (1)

Publication Number Publication Date
WO2006035348A1 true WO2006035348A1 (fr) 2006-04-06

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ID=35453519

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PCT/IB2005/053070 WO2006035348A1 (fr) 2004-09-28 2005-09-19 Dispositif de balayage optique

Country Status (2)

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TW (1) TW200615931A (fr)
WO (1) WO2006035348A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1069450A2 (fr) * 1999-06-16 2001-01-17 Canon Kabushiki Kaisha Elément optique et dispositif optique comprenant ledit élément
US20020176148A1 (en) * 2000-03-03 2002-11-28 Ichiro Onuki Optical apparatus
WO2004027489A1 (fr) * 2002-09-19 2004-04-01 Koninklijke Philips Electronics N.V. Element optique commutable
WO2004027769A1 (fr) * 2002-09-19 2004-04-01 Koninklijke Philips Electronics N.V. Dispositif de lecture optique
WO2004047092A1 (fr) * 2002-11-20 2004-06-03 Koninklijke Philips Electronics N.V. Dispositif d'exploration comprenant un filtre optique
WO2004059628A1 (fr) * 2002-12-30 2004-07-15 Koninklijke Philips Electronics N.V. Dispositif optique d'enregistrement et de lecture

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1069450A2 (fr) * 1999-06-16 2001-01-17 Canon Kabushiki Kaisha Elément optique et dispositif optique comprenant ledit élément
US20020176148A1 (en) * 2000-03-03 2002-11-28 Ichiro Onuki Optical apparatus
WO2004027489A1 (fr) * 2002-09-19 2004-04-01 Koninklijke Philips Electronics N.V. Element optique commutable
WO2004027769A1 (fr) * 2002-09-19 2004-04-01 Koninklijke Philips Electronics N.V. Dispositif de lecture optique
WO2004047092A1 (fr) * 2002-11-20 2004-06-03 Koninklijke Philips Electronics N.V. Dispositif d'exploration comprenant un filtre optique
WO2004059628A1 (fr) * 2002-12-30 2004-07-15 Koninklijke Philips Electronics N.V. Dispositif optique d'enregistrement et de lecture

Also Published As

Publication number Publication date
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