WO2007063456A1 - Procédé et système de lecture/écriture de données par une pluralité de points - Google Patents

Procédé et système de lecture/écriture de données par une pluralité de points Download PDF

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Publication number
WO2007063456A1
WO2007063456A1 PCT/IB2006/054394 IB2006054394W WO2007063456A1 WO 2007063456 A1 WO2007063456 A1 WO 2007063456A1 IB 2006054394 W IB2006054394 W IB 2006054394W WO 2007063456 A1 WO2007063456 A1 WO 2007063456A1
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WO
WIPO (PCT)
Prior art keywords
spot
spots
laser
optical axis
reversing
Prior art date
Application number
PCT/IB2006/054394
Other languages
English (en)
Inventor
Henk Goossens
Dayu Chen
Rong Liu
Alexander Marc Van Der Lee
Nicolas Baumgartner
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
Priority claimed from CN 200510128594 external-priority patent/CN1979648A/zh
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2007063456A1 publication Critical patent/WO2007063456A1/fr

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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
    • G11B7/14—Heads, e.g. forming of the optical beam spot or modulation of the optical beam specially adapted to record on, or to reproduce from, more than one track simultaneously
    • 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
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/08547—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical 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
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/08547—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements
    • G11B7/08564—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements using galvanomirrors
    • 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
    • G11B7/1353—Diffractive elements, e.g. holograms or gratings
    • 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
    • G11B7/1359—Single prisms

Definitions

  • the present invention relates to a method and system for reading/writing data on an optical disc, and more particularly, to a method and system of reading/writing data on an optical disc by a plurality of spots.
  • optical discs have become a data carrier widely used for storage of multi-media audio/video information considering its relatively low cost and large data storage capacity.
  • a way to increase the data rate of an optical drive is using multiple spots that read or write multiple tracks of an optical disc in parallel.
  • spots will encounter a part of the track that already has been read or written by another spot, as illustrated by Fig. IA and Fig. IB.
  • Fig. IA is a schematic diagram showing the situation where data are recorded/read on the optical disc by spot A from start of block 1, and by spot B from start of block 5. This parallel process of recording/reading by spot A and B goes on until spot A arrives at start of block 5, as illustrated by Fig. IB. In other words, spot A arrives at a block previously recorded/read by spot B. To avoid spot A record new data on the previously recorded/read area by spot B, a displacement of the spots is needed at this point.
  • the displacement comprises moving all spots over an equal distance.
  • the advantage of this spot displacement strategy is that it is very easy to implement because only a radial displacement of the objective lens is required.
  • European Patent Application EP0840294 discloses a multiple track scanning method for optical pickup using multiple spots, in which this spot displacement strategy is employed.
  • the displacement must be (Nb-I)Ng-I tracks (for a system with Nb spots, with a distance of Ng tracks between the spots) in order to read or write all data.
  • the data rate of this method is limited to a factor Nb-l/Ng times the data rate for one spot.
  • Ng is often 1, so the data rate gain will be limited to Nb-I.
  • a method of reading/writing data on an optical disc by a plurality of spots comprises the steps of detecting that all of the plurality of spots except one spot have reached a data area previously read/written; and reversing the positions of the plurality of spots compared to the one spot.
  • a system of reading/writing data on an optical disc by a plurality of spots comprises a detection device for detecting that all of the plurality of spots except one spot have reached a data area previously read/written, and generating a detection signal; and an actuation device, which movement is triggered by the detection signal, for reversing the positions of said plurality of spots compared to the one spot.
  • the displacement strategy according to the present invention allows a data rate increase of a factor Nb.
  • the displacement strategy of moving the spots over different distances simultaneously allows to increase the data rate of reading and writing on an optical disc.
  • the strategy of moving the spots can be implemented in an easy way since not all spots have to be moved over an equal distance simultaneously, resulting in a cost- effective solution.
  • FIG. IA and FIG. IB illustrate schematic diagrams showing the situation of a spot encountering a region that has been read or written by another spot.
  • FIGs. 2A-2D illustrate different stages of multi-spot readout of an optical disc using the spot displacement strategy according to one embodiment of the present invention.
  • FIG.3A illustrates realization of the spot reversing by rotating a grating.
  • FIG.3B illustrates the spot arrangement after objective lens on the information layer corresponding to Fig.3A.
  • FIG.4 illustrates a schematic block diagram showing the structure of a closed loop control system.
  • FIG.5A illustrates realization of the spot reversing by means of rotating a dove prism.
  • FIG.5B illustrates the spot arrangement after objective lens on the information layer corresponding to Fig.5A.
  • FIG.6A illustrates realization of the spot reversing by means of rotating a laser array.
  • FIG.6B illustrates the spot arrangement after objective lens on the information layer corresponding to Fig. ⁇ A.
  • Fig. ⁇ C illustrates realization of rotating a laser array by rotating a laser module.
  • Fig. ⁇ D is a front view of a laser module with a laser array according to a first embodiment.
  • Fig. ⁇ E is a front view of a second laser module with actuated laser die according to a second embodiment.
  • Fig. ⁇ F represents two views of a flexible heat sink.
  • FIG.7 illustrates realization of the spot reversing by means of rotating a optical pickup unit sub-assembly.
  • FIG.8 illustrates a schematic flowchart showing a method of reading data on an optical disc in an open-loop control according to one embodiment of the present invention.
  • FIG.9 illustrates a schematic flowchart showing a method of reading data on an optical disc in a closed-loop control according to one embodiment of the present invention.
  • Figs. 2A-2D illuminate different stages of multi-spot readout of an optical disc using the spot displacement strategy according to one embodiment of the present invention. This strategy is illustrated by the use of three spots A, B and C being positioned on different tracks.
  • Fig.2A three spots, Spot A, Spot B and Spot C, are on Tracks Tl, T2 and T3 respectively and start reading in parallel with the orientation of the arrow in Fig.2A.
  • a detection device After reading along the spiral track for almost one revolution, a detection device detects that Spot A and Spot B (except Spot C) will encounter the regions of tracks already read by
  • Fig.2C shows the positions of the three spots before displacement. Then, for improving the data rate, Spot A and Spot B are displaced by an actuation device in response to the detection signal to regions which have not been read previously.
  • Fig.2D shows the positions of the three spots after implementing the displacement according to one embodiment of the present invention : Spot C is not changed (still on Track T3), Spot B is moved to Track T5, and Spot A is moved to Track T6. In other words, the order of the spots is reversed and the original outer Spot C continues to read the same track. After displacement, Spot A becomes the outer spot.
  • the above spot displacement strategy can be used on reversing the order of the spots while the outer spot stays on the same track.
  • outer is defined here as the spot that is radially farthest away from the position the drive started to follow the spiral track. This is usually the spot farthest away from the centre of the disc.
  • the drive reads from outside to inside and the outer spot is the one farthest from the outer edge of the disc.
  • Fig.3 A is a schematic diagram illustrating realization of the spot reversing by rotating a grating.
  • a laser travels along an optical axis 301.
  • a grating 302 creates a number of diffraction orders, here indicated with beams A, B and C.
  • the objective lens
  • 303 focuses the three beams on three different positions on the information layer of an optical disc, as shown in Fig.3B.
  • the higher order beams will also rotate, as well as the spots on the information layer of the optical disc.
  • the spots In the spots displacement by means of rotating a grating part of the light path of the drive as shown in Fig.3A, the spots rotate around any axis parallel to the optical axis 301, so around spot B, in principle so that spots arrangement after objective lens on the information layer is rotated as shown in Fig.3B.
  • rotation of a grating can reverse the order of spots on the optical disc.
  • a closed loop control system that measures the radial position of Spot C and displaces the objective lens radially, if needed, is used according to techniques in the technical field of optical storage. This guarantees the edge spot like Spot C stays on its track, while other spots like Spot A and Spot B effectively rotate around the edge spot.
  • Fig.4 is a schematic block diagram showing the structure of a closed loop control system.
  • the system comprises optics 401 which includes an illuminating light path, a disc, and a returning light path with a detector and some other electronics.
  • the optics 401 generates an electrical signal, called radial error signal, which is proportional to the distance of the spot on the disc to the center of the data track. This distance can be adjusted by the radial actuator 402, which moves the objective lens in radial direction.
  • the force (amplitude and sign) with which the radial actuator has to be moved to keep the spot on the center of the track and thus reduce the radial error to zero is defined by a radial controller 403.
  • the radial controller 403 takes the radial error signal as input and calculates an output signal such that it will reduce its input to zero.
  • the radial controller 403 is an electronic filter that has different characteristics in different frequency regions.
  • a typical, and often applied example of such a controller is a Proportional-Integrator-Differentiator (PID) controller, which has an integrator function dominating the controller output at low frequencies, a proportional gain dominating the output at middle frequencies and a differentiator dominating the output at high frequencies.
  • PID Proportional-Integrator-Differentiator
  • the radial error of the edge (outer) spot is taken as input for the radial controller 403.
  • the closed loop control system as explained above will ensure the spot like Spot C will stay on its track during the rotation of part of the optical path.
  • Fig.5 A is a schematic diagram illustrating realization of the spot reversing by means of rotating a dove prism 501 in the light path.
  • Fig.5B shows the spot arrangement after objective lens 303 on the information layer.
  • a and B on the information layer of an optical disc as shown in Fig.5B By rotating the dove prism 501 around the optical axis 301, the two beams are rotated and the Spots A and B are also rotated as shown in Fig.5B.
  • a closed loop control system can also be used to keep the edge (outer) spot on the same track.
  • Fig.6 A is a schematic diagram illustrating realization of the spot reversing by means of rotating a laser array.
  • Fig. ⁇ B shows the spot arrangement after objective lens on the information layer.
  • a laser array 601 typically has multiple lasers positioned at a certain distance from the optical axis 301. After collimation of the two laser beams into parallel beams, the two beams will have a certain angle with respect to the optical axis 301 defined by the position of the lasers and the focal length of the collimator lens 602. These beams create two Spots A and B on the information layer of an optical disc. Rotating the laser array 601 will lead to rotation of the two beams and to a displacement of the Spots A and B on the disc. Also here a closed loop control system can be used to keep the outer spot on the same track.
  • the laser array may be formed by integrating several laser sources in one laser die, the laser die being placed inside a laser module.
  • Fig.6C is a schematic diagram illustrating realization of rotating a laser array by rotating a laser module.
  • the laser module 620 By rotating the laser module 620 by means of actuators 622, the laser die 621 placed inside the laser module 620 (on top on a heat sink 623) is also rotated.
  • Another method to rotate a laser array is to only rotate the laser die while keeping the laser module stationary. By this method, the reversing step is done inside a laser module This method does not require extra components to the light path, which can therefore be more compact, resulting in a system easier to align.
  • Fig.6D is a front view of a laser module with a laser array according to a first embodiment.
  • the laser die 603 is fixed on a heat sink 613, which is horizontally held in position by two leaf springs 604.
  • the leaf springs 604 allows a certain flexibility to the heat sink 613(and the laser die) in vertical and rotational direction (illustrated by the turning arrow).
  • the advantage of the leaf springs 604 is that a rotation can be performed without moving. So the heat sink 613 and the actuator 605 are in contact in order to guarantee a high precision of the movement of the laser array. For this reason additional springs have been introduced in the system.
  • the rotation of the laser array may be done in using two actuators 605 (for example micro- actuators comprising piezo-electric elements) placed at the same distance from the centre of the laser array.
  • the actuators 605 are fixed to the laser module 620 but not to the heat sink 613. If the actuators 605 work in phase, then the heat sink 613 will rotate around the centre of the laser array, which should be aligned with the optical axis of the optical pick up unit.
  • the leaf spring 604 and the actuators 605 are placed on top and next to the heat sink 613, such that a monitor diode can be placed behind the laser array. Further the leaf springs 604 have to be designed in a way that the thermal resistance of the system stays in acceptable range. The heat flow has to be good enough for keeping the laser die 603 on working temperature.
  • Fig.6E is a front view of a second laser module with actuated laser die according to a second embodiment. This time the actuators 608 are placed horizontally. Due to the "double L-shape" of the heat sink 614, the displacement of the actuators 608 is transformed into a rotation of the laser die 606. The transformation factor depends on the ratio of the extremities of the L-shape.
  • the second embodiment is similar to the first embodiment.
  • the difference in the second embodiment is that the actuators 608 apply at the extremities of the "double L-shape" (1 L) of the heat sink 614.
  • the system becomes more compact and the transformation factor from the linear movement of the actuators 608 to the rotational movement of the laser die 606 can be adjusted by changing the ratio (length to height) of the "L" branches.
  • Fig.6F represents two views of a flexible heat sink: a first three-dimensional view A showing a flexible heat sink, and a second view B (cross- section) showing possible actuating means.
  • Views A and B show a heat sink made from a block of metal almost cut into two pieces. Only a thin part of material is left over behaving as bendable connection. This results in means to rotate one part of the block relative to the other part without play.
  • One part of the block is fixed to the laser module; at the other part the laser die 609 is fixed in a way that the centre of the laser array coincides with the rotational axis 610.
  • the rotation can be actuated for example by the use of a coil ⁇ l 1 -magnet 612 system as shown in Fig.6F.
  • the design of the heat sink has to be done in a way that thermal resistance of the system is small enough for keeping the laser die on working temperature.
  • Fig.7 is a schematic diagram illustrating realization of the spot reversing by means of rotating a sub-assembly of the light path, which at least comprises the light sources 701 and the preferably the photo detectors 707. Also here a closed loop control system can be used to keep the outer spot on the same track.
  • a folding mirror 702 is used to reflect these beams towards the objective lens 703, which focuses the beams into a plurality of spots 704 on the optical disc 705.
  • the reflected light from the disc 705, representing the information, is again reflected by the folding mirror 702, the beam splitter 706 and finally projected on to a plurality of photo detectors 707.
  • These photo detectors 707 convert the light into electrical signals.
  • a sub-assembly comprising the light sources 701, the beam splitter 706, the folding mirror 702 and the photo detectors 707 is rotated around the vertical axis (it may coincide with the optical axis 708 of the objective lens 703), the spots on the disc will also rotate around that axis 708, while the spots on the detectors remain stationary.
  • the axis of rotation preferably coincides with the optical axis 708 of the objective lens 703.
  • the spots on the detectors 707 do not move while displacing the spots on the disc 705, which would otherwise deteriorate the quality of the signals, derived from the detectors 707. Furthermore, no extra optical components are needed for the spot displacement. It is noted, however, that light sources 701 and photo detectors 707 are not restricted to be rotated together. The reason is that for this solution a set of flexible wires is needed to connect the photo detectors 707 on the rotating sub-assembly to the non-rotating part of the optical pickup unit (OPU). In terms of cost, it might be preferable to place the photo detectors 707 on the non-rotating part of the OPU and solve the problem of deterioration of the signals from the photo detectors 707 caused by spot displacement in the electronics.
  • OPU optical pickup unit
  • Another embodiment is to rotate the folding mirror 702.
  • Rotating the folding mirror 702 in Fig.7 around axis 708 will also lead to rotation of the spots on the information layer.
  • a closed loop control system can be used to keep the outer spot on the same track.
  • each laser emitted from a laser array is reflected by a small mirror and then travels through the collimator and objective lens to form a spot on the optical disc.
  • Controlling all of mirrors for deflections of different beams synchronically may also complete the spot reversing.
  • each spot is controlled independently. Rotation is, however, by far the simplest implementation of the present invention, because only one degree of freedom is actuated.
  • an open-loop or closed-loop control can be chosen to implement the displacement of the spots.
  • Fig.8 is a schematic flowchart showing a method of reading data on an optical disc by a plurality of spots in an open-loop control according to one embodiment of the present invention.
  • step S810 whether all of the plurality of spots except one spot have reached a data area previously read/written is detected. And then, at step S820, the positions of the plurality of spots compared to the one spot is reversed. Therefore, the spots displacement is finished.
  • a method in open-loop is in general simpler to be carried out. In a closed-loop control, the position of the moving spots is measured during displacement and the movement of each spot is controlled on the basis of that signal. To achieve the above effect, a controller is applied thereto.
  • one difference between open-loop and closed-loop control is that in an open loop scheme the rotation is done by feeding a predefined electric signal into an actuator, while for a closed loop reversing jump, the electric signal going into the actuator depends on the measured radial error signal from one of the non-static spots.
  • Fig.9 is a schematic flowchart showing a method of reading data on an optical disc by a plurality of spots in a closed-loop control according to one embodiment of the present invention.
  • step S910 whether all of the plurality of spots except one spot (such as the outer spot) have reached a data area previously read/written is detected.
  • step S920 the positions of all of the spots except the one spot are measured.
  • step S930 the movements of all of the spots except the one spot are controlled based on the signals measured.
  • the positions of the plurality of spots compared to the one spot is reversed.
  • the closed-loop control system is often more robust and therefore is a preferred embodiment.
  • the spots are positioned in an almost tangential orientation compared to the optical disc. This is advantageous because it minimizes the mechanical movement of components during displacement of the spots, and therefore simplifies the actuation. Indeed, the reversing can thus be done via rotating the spots by a very small angle.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)
  • Optical Recording Or Reproduction (AREA)

Abstract

Cette invention concerne un procédé et un système de lecture/écriture de données sur un disque optique par une pluralité de points (A, B, C). Ce procédé comprend les étapes consistant à détecter si l'ensemble des points à l'exception d'un point a atteint une zone de données précédemment lue/écrite ; et à inverser les positions de la pluralité de points par rapport audit point.
PCT/IB2006/054394 2005-11-29 2006-11-23 Procédé et système de lecture/écriture de données par une pluralité de points WO2007063456A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CN200510128594.5 2005-11-29
CN 200510128594 CN1979648A (zh) 2005-11-29 2005-11-29 用复数个光点在光盘上读/写数据的方法和系统
CN200610081965 2006-05-12
CN200610081965.3 2006-05-12

Publications (1)

Publication Number Publication Date
WO2007063456A1 true WO2007063456A1 (fr) 2007-06-07

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007148278A2 (fr) * 2006-06-23 2007-12-27 Koninklijke Philips Electronics N.V. Procédé et système pour lire et écrire un disque optique avec une pluralité de faisceaux laser

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4982395A (en) * 1988-10-03 1991-01-01 Storage Technology Partners Ii Composite optical grating for optical disk data storage systems
JPH04146534A (ja) * 1990-10-05 1992-05-20 Mitsubishi Electric Corp マルチビーム光ヘッド
JPH07244859A (ja) * 1994-03-08 1995-09-19 Mitsubishi Electric Corp トラックジャンピング方法およびマルチビーム光ヘッド
US5808986A (en) * 1993-02-17 1998-09-15 Vixel Corporation Multiple beam optical memory system with solid-state lasers
US6493297B1 (en) * 1990-05-09 2002-12-10 Hitachi, Ltd. Multibeam optical disk record and reproduction apparatus and method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4982395A (en) * 1988-10-03 1991-01-01 Storage Technology Partners Ii Composite optical grating for optical disk data storage systems
US6493297B1 (en) * 1990-05-09 2002-12-10 Hitachi, Ltd. Multibeam optical disk record and reproduction apparatus and method
JPH04146534A (ja) * 1990-10-05 1992-05-20 Mitsubishi Electric Corp マルチビーム光ヘッド
US5808986A (en) * 1993-02-17 1998-09-15 Vixel Corporation Multiple beam optical memory system with solid-state lasers
JPH07244859A (ja) * 1994-03-08 1995-09-19 Mitsubishi Electric Corp トラックジャンピング方法およびマルチビーム光ヘッド

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007148278A2 (fr) * 2006-06-23 2007-12-27 Koninklijke Philips Electronics N.V. Procédé et système pour lire et écrire un disque optique avec une pluralité de faisceaux laser
WO2007148278A3 (fr) * 2006-06-23 2008-02-21 Koninkl Philips Electronics Nv Procédé et système pour lire et écrire un disque optique avec une pluralité de faisceaux laser

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