WO2008129450A1 - Système et procédé de stockage du rapport push-pull normalisé dans une partie préformatée d'un disque réinscriptible utiles pour assurer le fonctionnement continu sans à-coups d'un servomécanisme de guidage - Google Patents

Système et procédé de stockage du rapport push-pull normalisé dans une partie préformatée d'un disque réinscriptible utiles pour assurer le fonctionnement continu sans à-coups d'un servomécanisme de guidage Download PDF

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Publication number
WO2008129450A1
WO2008129450A1 PCT/IB2008/051422 IB2008051422W WO2008129450A1 WO 2008129450 A1 WO2008129450 A1 WO 2008129450A1 IB 2008051422 W IB2008051422 W IB 2008051422W WO 2008129450 A1 WO2008129450 A1 WO 2008129450A1
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WO
WIPO (PCT)
Prior art keywords
disc
tracks
blank
written
tes
Prior art date
Application number
PCT/IB2008/051422
Other languages
English (en)
Inventor
Johannes Lepoldus Bakx
Original Assignee
Koninklijke Philips Electronics N.V.
U.S. Philips Corporation
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., U.S. Philips Corporation filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2008129450A1 publication Critical patent/WO2008129450A1/fr

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
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0945—Methods for initialising servos, start-up sequences
    • 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
    • G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
    • G11B7/00736—Auxiliary data, e.g. lead-in, lead-out, Power Calibration Area [PCA], Burst Cutting Area [BCA], control information
    • 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
    • G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
    • G11B7/08523—Methods for track change, selection or preliminary positioning by moving the head with both tracking and focusing pull-in
    • 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
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0941—Methods and circuits for servo gain or phase compensation during operation

Definitions

  • the present invention generally relates to optical data reading. More particularly, the present invention relates to the smooth and stable performance of a tracking servo in areas which contain an arbitrary mix of blank and written tracks to allow the readout spot to smoothly track the pre-groove center.
  • an optical storage disc comprises at least one track, either in the form of a continuous spiral or in the form of multiple concentric circles, of storage space where information may be stored in the form of a data pattern.
  • Optical discs may be read-only type, where information is recorded during manufacturing, which information can only be read by a user.
  • the optical storage disc may also be a writable type, where information may be stored by a user.
  • the present invention is intended for use with writable optical discs. Therefore, the present invention will hereinafter specifically be explained for the case of writable discs, without the intention of restricting the scope of the invention to such example.
  • a potential problem of a partially written disk is that the amplitude of the radial error signal on a blank area differs from that of a written area. While reading and seeking on the disk, the readout spot will from time to time enter a different area type (i.e., blank or written). The requirement is that the tracking servo should not be disturbed at an area transition (e.g., blank-written or written-blank). Ideally, the readout spot should smoothly continue to track the pre-groove center at these transitions. However, when the readout spot moves from a blank area into a written area or the reverse, the gain of the radial servo loop will change. This is highly undesirable, since in general the loop is only stable for a limited gain range.
  • a method of maintaining a readout spot on tracks of an optical disc is known as push-pull method.
  • This method involves the generation of a tracking error signal (TES) referred to as a push-pull signal.
  • the tracking error signal corresponds to the default error signal in the radial axis of the disc and is caused by the interaction of the readout spot with the groove or some other tracking structure placed on the disc surface.
  • a tracking servo adjusts the radial position of the spot to keep the push-pull signal at a predetermined value.
  • the readout spot is on the track for the zero-crossing points of the push-pull signal.
  • FIG. 1 depicts the implementation of the known DC push-pull method. It includes a photo-detector comprising two areas Al and A2 for detecting reflected or transmitted beams of the optical spot. This photo-detector generates two output signals A and B that are filtered by low-pass filters LPFl and LPF2, resulting in low-frequency signals A(DC) and B(DC). Subtracting means SUBl determine the difference of the signals A(DC) and B(DC) for the purpose of generating the low-frequency push-pull signal PP(DC) that is used as a tracking error signal.
  • the tracking error signal (TES) is usually derived from the PP- signal.
  • an associated parameter of the PP-signal is the "Normalized PP" value, which, according to the BLUE-RAY DISC definition, is the peak-to-peak value of PP divided (i.e., normalized) by 2x the average value of the central aperture while the readout spot crosses the tracks.
  • This "Normalized PP” value determines the amplitude of the tracking error signal (TES) and hence the gain, and hence the bandwidth of the radial servo loop.
  • Normalized PP Ratio is defined, according to the BLUE-RAY DISC , as the ratio of the Normalized PP values before and after recording.
  • NPPR Normalized PP Ratio
  • the requirement is that NPPR stay within the range, 0.75 ⁇ NPPR ⁇ 1.25, which is a range that can just be managed by a drive.
  • many media cannot comply with this range.
  • the new BD-R media have a NPPR that differs substantially from 1, the optimum value.
  • a solution was developed that allows a large range of NPPR values to be handled by a drive.
  • the solution switches the servo gain according the state of a disc area, i.e. blank or written.
  • the solution calculates what a proper gain should be for a blank or a written area and switches the servo gain in accordance with the calculation.
  • one drawback of the proposed solution is the assumption that the drive is able to determine what the proper gains are for the two areas, i.e., blank or written. For sufficiently large areas (i.e., blank or written) this determination is feasible.
  • the drive can determine what the proper gains are for the two areas by calibrating the tracking error signal (TES) on an each area (i.e., blank, written) by measuring its peak-to-peak value while in open radial loop mode, if there is a sufficiently large area of that type available.
  • TES tracking error signal
  • the determination of what the proper gain should be is not feasible for a written area on a BLUE-RAYTM formatted disk for the case where a single block of data (e.g., less than one revolution for BLUE- RAY DISCTM), is written, which prohibits an open-loop measurement of tracking error signal (TES).
  • the system and method must allow the readout spot to smoothly continue to track the pre-groove center for those cases where the open-loop measurement of the tracking error signal (TES) for either the blank or written area of a disc is not feasible.
  • TES tracking error signal
  • the present invention has been made in view of the above problems. Accordingly, the present invention provides a method that allows for the smooth and stable performance of a tracking servo in areas of a re-writable disc which contain an arbitrary mixture of blank and written tracks to allow the readout spot to smoothly continue to track the pre-groove center where the open-loop measurement of the tracking error signal (TES) for either the blank or written areas of a disc is not feasible.
  • TES tracking error signal
  • the method further comprises the steps of: determining whether the tracks within the track capture area are blank or written tracks; assigning the measured amplitude of the tracking error signal (TES) to a servo gain for blank areas if it is determined that the tracks within the track capture area are blank tracks, otherwise assigning the measured amplitude of the tracking error signal (TES) to a servo gain for written areas; reading the normalized NPPR from the pre-formatted portion of the disk; estimating the servo gain for written areas of the disc based on the measured amplitude of the tracking error signal (TES) and the NPPR if it was determined that the tracks within the capture area are blank tracks; and otherwise estimating the servo gain for blank areas of the disc based on the measured amplitude of the tracking error signal (TES) and the NPPR, if it was determined that the tracks within the capture area are written tracks.
  • a primary advantage of the invention is the flexibility provided to media manufacturers in choosing media materials. More particularly, the current restrictive requirement that the NPPR must not deviate too much from 1.0, limits the possible ranges of disk parameters such as the width, depth and slope of the pregroove, and the refractive indices of the recording stack before and after recording. This restriction is applied because all these parameters influence the PP signal which in turn affects the NPPR.
  • This limitation is overcome by the invention in that the drive can now handle large PP ratios by performing a gain calibration for both written and blank areas of the disc and switching the gain in transition areas of the disc, (e.g., blank to written and written to blank), when performing read operations.
  • FIG. 1 illustrates a known tracking system for generating a radial tracking error signal.
  • FIG. 2 shows schematically a DVD showing a spiral data track including mixed mode regions.
  • FIG. 3 is a more detailed illustration of a singular mixed mode region of the
  • FIG. 4 is a flow diagram illustrating a process to facilitate the smooth performance of a tracking servo at area transitions of a mixed mode region of a DVD.
  • FIG. 2 shows schematically a spiral track 4 of a re- writable disc 6.
  • the re- writable disc 6 is comprised of an exemplary mixture of blank 35 and written 30 tracks. The written tracks 30 being illustrated by the darker shaded areas.
  • a potential problem of a partially written disk is that the amplitude of the radial error signal on a blank area differs from that of a written area. While reading and seeking on the disk, the readout spot will from time to time enter a different area type (i.e., blank or written). This occurs in the so-called mixed mode regions, such as the one shown in FIG. 3.
  • FIG. 3 illustrates one segment 40 of the re- writable disc 6 of FIG. 2, the segment 40 being defined as a "mixed-mode" region, comprised of a mixture of blank tracks 35a-c and written 30a-c tracks having transitions there-between. It is understood that the particular configuration of blank and written tracks is provided by way of example only.
  • the tracking servo not be disturbed at area transitions in these mixed mode regions.
  • An area transition comprising, for example, a transition from a blank to a written region or the reverse.
  • the readout spot should smoothly continue to track the pre-groove center at these transitions.
  • the gain of the radial servo loop will change. As pointed out above, this is highly undesirable, since in general the loop is only stable for a limited gain range.
  • This problem is overcome by allowing for the smooth and stable performance of a tracking servo in those areas of a re- writable disc which contain an arbitrary mixture of blank and written tracks to allow the readout spot to smoothly continue to track the pre-groove center where the open-loop measurement of the tracking error signal (TES) for either the blank or written areas of a disc is not feasible.
  • TES tracking error signal
  • the smooth and stable performance of a tracking servo is assured by using one of a pre-stored measured servo gain value or a pre-stored estimated servo gain value for the gain of the radial servo loop. This process is described in greater detail as follows.
  • FIG. 4 a process 400 is illustrated to allow for the smooth performance of a tracking servo in mixed mode areas 40 of a disc 6, which contain an arbitrary mixture of blank 35 and written 30 tracks, to allow the readout spot to smoothly continue to track the pre-groove center for those cases where the open-loop measurement of the tracking error signal (TES) for either the blank areas 35 or written areas 30 of a disc 6 cannot be obtained because the blank areas 35 or written areas 30 of a disc 6 are too small to allow an open-loop measurement of TES.
  • TES tracking error signal
  • a nominal value of the normalized push-pull ratio is stored in a pre-formatted part of the disk.
  • This nominal value can be provided by the media supplier or otherwise defined in the disk standard.
  • the pre-formatted portion of the disk refers to either the modulation of the pregroove or the embossed pits of the disc.
  • particular pregroove portions may include the embossed wobble of the pre-groove of the media and the so-called HFM, which is a high-frequency version of the wobble in the so-called PIC band of Blue-Ray Disk. For Blue-Ray Disc BD-R/RE startup is always done in the so-called PIC band, which is never written.
  • the gain of the blank area is calibrated, while the gain of the written area is estimated from the NPPR.
  • DVD+R/RW application
  • the reverse may be true because for DVD+R/RW applications data is written in a contiguous way. That is, the DVD+R/RW format is not used as a random write format as is true for the Blue-Ray Disk [00027]
  • particular embossed pit portions of the disc may include the pits of an embossed area such as the Lead-in Area of a DVD-R/RW disk, Preformatted headers such as those present in DVD-RAM and Land Prepits as used in connection with DVD-R/RW.
  • Land prepits are formed on a predetermined area during the manufacture of a disc substrate.
  • a pickup device provided in a recording/reproducing apparatus can easily move to a desired location using the information recorded in the land prepits. Also, the pickup device can identify a sector number or type, a land/groove or the like, and perform a servo control using the information recorded in forms of land prepits.
  • the on-focus state is acquired near the inner radius of the disc near the point where the normalized push-pull ratio is stored. It should be understood that it is much more convenient to acquire the focus near the inner radius rather than the outer radius to avoid a long search procedure from outside to inside, which is cumbersome since tracking is not possible or reliable on every area of the disk at this point because the NPPR is not yet known.
  • the location of the focus is defined by the disk standard, and is typically situated at the inner radius. Focusing near this location prevents a long search procedure before gain switching is in operation (i.e., before the NPPR is read).
  • the amplitude of the open-loop tracking error signal is measured while in the radial open-loop mode to estimate the tracking servo gain (NPP).
  • the open-loop tracking error signal can be measured by applying the tracking servo in an open-loop mode and measuring the peak-to-peak value of TES using a peak detector circuit. This step is performed as a check to determine whether the position of the readout spot is correct (i.e., within the capture area) and that the TES measurement can be trusted.
  • Steps 408 through 412 refer to the track capture process for establishing a stable servo loop.
  • the total gain in the loop should have a well-defined value in order to get acceptable values for the amplitude- and phase margin. Large deviations from the optimum gain value will cause the capture process to fail, or, even when it succeeds, to result in unstable loop behavior.
  • three steps are required: (1) setting the loop gain, (2) closing the radial servo loop and (3) tracking the pregroove.
  • step 408 - Track Capture step 1 - the loop gain is set using the open-loop tracking error signal (TES) measured at step 406.
  • TES open-loop tracking error signal
  • step 410 Track Capture step 2 - the radial servo loop is closed.
  • step 412 Track Capture step 3 - the pregroove is tracked for those tracks within the track capture area.
  • step 414 it is determined whether the tracks within the capture area are blank or written. This determination may be made by determining the presence or absence of RF at the start-up point while in a radial closed-loop mode. The presence of absence of RF can be made by measuring the power or the RMS value of RF in a pre-determined time interval and comparing the result with a detection level. In another embodiment, the peak-to- bottom level of a detected RF level is measured and compared with a detection threshold.
  • the measured amplitude of the tracking error signal (TES) is assigned to a servo gain for blank areas if it is determined at step 414 that the tracks within the track capture area are blank tracks.
  • the measured amplitude of the tracking error signal (TES) is assigned to a servo gain for written areas if it is determined at step 414 that the tracks within the track capture area are written tracks.
  • the NPPR is read from the disc. In one embodiment, this can be performed by moving the optical head to the location where the NPPR is located, closing the tracking servo loop, and reading and decoding the wobble signal. As discussed above, the NPPR may be stored in other locations on the disc.
  • the tracking servo gain is estimated for the written area if the tracks within the capture area were determined to be blank at step 414.
  • the tracking servo gain is estimated for the written areas by multiplying the calculated servo gain (NPP) for the blank areas by the NPPR.
  • the tracking servo gain is estimated for blank areas if the tracks within the capture area were determined to be written at step 414.
  • the tracking servo gain is estimated for the blank areas by dividing the calculated servo gain (NPP) at step 408 by the NPPR.
  • the calculated (estimated) servo gain value is stored in memory for use during normal operation.
  • the tracking servo gain (NPP), measured at step 406 is retrieved from the memory for use in setting the servo gain for the current blank area of the disc.
  • the calculated (estimated) servo gain value for blank areas of the track is retrieved from memory to set the instantaneous servo gain for the blank areas 30.
  • the measured tracking servo gain (NPP) is retrieved from memory to set the instantaneous servo gain for the written area 35 of the disc.

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  • Optical Recording Or Reproduction (AREA)

Abstract

L'invention concerne un procédé qui permet à un servomécanisme de guidage de fonctionner de manière stable sans à-coups dans des régions d'un disque réinscriptible qui contient un mélange arbitraire de pistes vierges et écrites, le gain de boucle du servomécanisme de guidage étant réglé à partir du signal d'erreur de guidage quand la boucle est ouverte. Le gain du servomécanisme pour les différentes régions de piste est ensuite estimé à partir à la fois du gain de boucle du servomécanisme et de la valeur nominale du rapport push-pull normalisé.
PCT/IB2008/051422 2007-04-18 2008-04-14 Système et procédé de stockage du rapport push-pull normalisé dans une partie préformatée d'un disque réinscriptible utiles pour assurer le fonctionnement continu sans à-coups d'un servomécanisme de guidage WO2008129450A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US91247907P 2007-04-18 2007-04-18
US60/912,479 2007-04-18
US3453908P 2008-03-07 2008-03-07
US61/034,539 2008-03-07

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WO2008129450A1 true WO2008129450A1 (fr) 2008-10-30

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WO (1) WO2008129450A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2246850A1 (fr) * 2008-01-31 2010-11-03 Kabushiki Kaisha Kenwood Procédé de reconnaissance de disque optique, dispositif à disque optique, et logiciel

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0388555A2 (fr) * 1989-03-20 1990-09-26 Pioneer Electronic Corporation Méthode pour la régulation de l'amplification d'un circuit servo pour suivi de piste
EP0867868A2 (fr) * 1997-03-27 1998-09-30 Mitsubishi Chemical Corporation Milieu d'enregistrement optique d'information
WO2004105000A1 (fr) * 2003-05-20 2004-12-02 Samsung Electronics Co., Ltd. Support de mise en memoire de l'information et procede et appareil d'enregistrement et/ou de reproduction de donnees sur et/ou a partir dudit support

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0388555A2 (fr) * 1989-03-20 1990-09-26 Pioneer Electronic Corporation Méthode pour la régulation de l'amplification d'un circuit servo pour suivi de piste
EP0867868A2 (fr) * 1997-03-27 1998-09-30 Mitsubishi Chemical Corporation Milieu d'enregistrement optique d'information
WO2004105000A1 (fr) * 2003-05-20 2004-12-02 Samsung Electronics Co., Ltd. Support de mise en memoire de l'information et procede et appareil d'enregistrement et/ou de reproduction de donnees sur et/ou a partir dudit support

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2246850A1 (fr) * 2008-01-31 2010-11-03 Kabushiki Kaisha Kenwood Procédé de reconnaissance de disque optique, dispositif à disque optique, et logiciel
EP2246850A4 (fr) * 2008-01-31 2011-04-06 Kenwood Corp Procédé de reconnaissance de disque optique, dispositif à disque optique, et logiciel

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