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WO2008020358A2 - Procédé et système pour commander des puissances d'écriture pour une pluralité de faisceaux laser - Google Patents

Procédé et système pour commander des puissances d'écriture pour une pluralité de faisceaux laser Download PDF

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Publication number
WO2008020358A2
WO2008020358A2 PCT/IB2007/053061 IB2007053061W WO2008020358A2 WO 2008020358 A2 WO2008020358 A2 WO 2008020358A2 IB 2007053061 W IB2007053061 W IB 2007053061W WO 2008020358 A2 WO2008020358 A2 WO 2008020358A2
Authority
WO
WIPO (PCT)
Prior art keywords
laser beam
writing
optical disc
copying
laser beams
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.)
Ceased
Application number
PCT/IB2007/053061
Other languages
English (en)
Other versions
WO2008020358A3 (fr
Inventor
Dayu Chen
Henk Goossens
Qiang Zhan
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.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
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 NV filed Critical Koninklijke Philips Electronics NV
Publication of WO2008020358A2 publication Critical patent/WO2008020358A2/fr
Publication of WO2008020358A3 publication Critical patent/WO2008020358A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045—Recording
    • G11B7/00458—Verification, i.e. checking data during or after recording
    • 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
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/126—Circuits, methods or arrangements for laser control or stabilisation

Definitions

  • the invention relates to a method and system for controlling the writing power of a laser beam during writing an optical disc, and the invention especially relates to a method and system for controlling the writing powers of a plurality of laser beams during writing an optical disc.
  • the optical disc may be a DVD (Digital Versatile Disc), a CD (Compact Disc), or a BD (Blu-ray Disc). Therefore, during writing an optical disc, an OPC (Optimum Power Control) process is required, so as to maintain a good writing quality.
  • OPC Optimum Power Control
  • a CAV Constant Angular Velocity
  • a Walking-OPC may be employed for controlling writing power.
  • the reason for using Walking-OPC is that: when CAV is employed to write an optical disc, the linear velocity is constantly changing. The linear velocity of an inner track of an optical disc is smaller than the linear velocity of an outer track of the optical disc in CAV mode. For example, when a 16X DVD is running full speed in CAV mode, the linear velocity at an innermost track is actually 6.6X.
  • a Walking-OPC process for a laser beam may comprise the steps of: writing predefined length data; jumping back to a start point of the written predefined length data; checking the writing quality of the written predefined length data; adjusting the writing power of the laser beam according to the checked writing quality.
  • the laser beam has to jump back to check the writing quality, which may reduce the writing efficiency because of the extra time required for the jumping back process and the checking process, and may also require extra energy for the jumping back process.
  • the use of a plurality of laser beams for writing may require a substantial amount of extra time and a large increase in energy consumption.
  • the method of controlling writing powers for a plurality of laser beams during writing an optical disc comprises the steps of:
  • the advantage is that a laser beam can be used to check the writing quality of another laser beam without a jumping back process, thereby saving time and energy. Furthermore, a laser beam, arriving at an area previously written by another laser beam, must be kept in a waiting state (i.e not in writing state) to avoid overlapping writing, until all laser beams are simultaneously shifted to a subsequent writing position. Thus, the checking process implemented by a laser beam being in a waiting state may not consume extra time.
  • the plurality of laser beams are positioned along inner tracks to outer tracks of the optical disc, and each laser beam has a symmetrical laser beam, said method further comprising the step of:
  • the advantage is that the method can save much more time and energy, since the writing powers for the symmetrical laser beams can be directly copied from corresponding symmetrical laser beams, without a checking process and an adjusting process.
  • the invention also proposes a system comprising a processing unit for implementing the different steps of the method according to the invention.
  • Fig. 1 to Fig. 4 illustrate, by means of an example, different states of writing an optical disc
  • Fig. 5 is a flow chart describing, by means of an embodiment, a method of controlling writing powers for a plurality of laser beams during writing an optical disc
  • Fig. 6 depicts a system for implementing the method previously described.
  • a laser beam "waiting state" is intended to mean that a laser beam is not in a writing state.
  • the plurality of laser beams is positioned along inner tracks to outer tracks of an optical disc.
  • the innermost laser beam designates the laser beam positioned on the innermost track of the optical disc compared with other laser beams
  • the outermost laser beam designates the laser beam positioned on the outermost track of the optical disc compared with other laser beams.
  • Fig. 1 to Fig. 4 illustrate, by means of an example, different states of writing an optical disc by using four laser beams A, B, C, and D applied to the optical disc so as to write data in parallel.
  • the optical disc and the laser beams make a relative rotational movement.
  • the writing process may be implemented segment by segment (e.g. Error Correct Code Block).
  • the laser beam B is located inside segment 2
  • the laser beam C is located inside segment 4
  • the laser beam D is located inside segment 7.
  • A is positioned at the start of segment 1, and starts to write.
  • the laser beams B, C, and D are not positioned at the start of segments and are kept in a waiting state. Thus, a writing revolution is started.
  • the laser beam D starts writing after arriving at the start of segment 8.
  • the laser beam C starts writing after arriving at the start of segment 5, and the laser beam B just arrives at the start of segment 3 and starts to write.
  • the laser beam A is still in the writing state.
  • the laser beam C arrives at the start of segment 8, i.e. the area previously written by the laser beam D. To avoid writing over the area previously written by the laser beam D, the laser beam C is kept in a waiting state. During this time, the laser beam C is used to read the data of the area previously written by the laser beam D, so as to check the writing quality of the laser beam D and then adjust the writing power of the laser beam D according to the checked writing quality.
  • the laser beam B arrives at the start of segment 5, i.e. the area previously written by the laser beam C. To avoid writing over the area previously written by the laser beam C, the laser beam B is kept in the waiting state. During this time, the laser beam B is used to read the data of the area previously written by the laser beam C, so as to check the writing quality of the laser beam C and then adjust the writing power of the laser beam C according to the checked writing quality.
  • the laser beam A when the laser beam A arrives at the area previously written by the laser beam B, the laser beam A can also be used to check the writing quality of the laser beam B (not shown).
  • the writing is done from inner track to outer track; the writing quality of every laser beam can be checked by the same process as described above, with the exception of the innermost laser beam A. If the writing is done from outer track to inner track, the laser beam whose quality cannot be checked is the outermost laser beam D. Based on an optical axis, a symmetrical relationship exists between the laser beams (if the number of laser beams is odd, the middle laser doesn't have a symmetrical laser beam), and the defocus and skew angle of two symmetrical laser beams are the same.
  • the writing power of the innermost laser beam A can be directly obtained by copying the adjusted writing power of the outermost laser beam D (the corresponding symmetrical laser beam).
  • the writing power of each laser beam which has a symmetrical laser beam can also be obtained by copying a previously adjusted writing power of a corresponding symmetrical laser beam, without the checking process and the adjusting process. If every laser beam has obtained a writing power by adjusting or copying, and the outermost laser beam D has arrived at the start of a segment, the writing revolution is completed. Therefore, all laser beams (A, B, C, D) are shifted to a subsequent writing position (not shown) to start a subsequent writing revolution, and the previous process can be repeated.
  • the adjusting value of the writing power depends on the checked writing quality and a predefined writing quality threshold.
  • the adjusting value is larger; if the checked writing quality is near to the threshold, the adjusting value is smaller; if the checked quality is equal to the threshold, the adjusting value can be zero. Normally, the likelihood of the adjusting value being zero is very low.
  • Fig. 5 is a flow chart depicting a method of controlling writing powers for a plurality of laser beams during writing an optical disc, by showing one embodiment of the invention. The method comprises the steps of:
  • the detecting (520) step can be implemented by detecting the address information previously written by said another laser beam (D).
  • - checking (530) the writing quality of the area written by the laser beam (C) that arrived at the area.
  • the laser beam (C) that arrived at the area is used to read back data in the area, so as to check the writing quality of the read back data.
  • - adjusting (540) the writing power of said another laser beam (D) according to the checked writing quality.
  • the adjusting value of the writing power depends on the checked writing quality and a predefined writing quality threshold. If the checked writing quality is far from the threshold, the adjusting value is larger; if the checked writing quality is near to the threshold, the adjusting value is smaller; if the checked quality is equal to the threshold, the adjusting value can be zero. Normally, the likelihood of the adjusting value being zero is very low.
  • the plurality of laser beams is positioned along inner tracks to outer tracks of the optical disc, and the outermost laser beam (D) is symmetrical to the innermost laser beam (A).
  • the method further comprises a step of: copying (550) the adjusted writing power of the outermost laser beam (D) to the innermost laser beam (A), if the writing is done from inner track to outer track, or copying (550) the adjusted writing power of the innermost laser beam (A) to the outermost laser beam (D), if the writing is done from outer track to inner track.
  • the writing power of each laser beam which has a symmetrical laser beam can also be obtained by copying a previously adjusted writing power of a corresponding symmetrical laser beam, without the checking process and the adjusting process.
  • the method further comprises a step of: copying (550) the adjusted writing power of said another laser beam (C, D) to a symmetrical laser beam (B, A), if said another laser beam (C, D) has a symmetrical laser beam (B, A).
  • the method further comprises a switching (510) step for successively switching-on the plurality of laser beams to write the optical disc.
  • the method further comprises a step of: simultaneously shifting (560) all the laser beams (A, B, C, D) to a subsequent position for a subsequent writing revolution, if each laser beam obtains a writing power by the adjusting (540) step or copying (550) step.
  • This shifting implies a simultaneous displacement of all the laser beams (A, B, C, D), for example via a translation movement along a radial direction of the optical disc.
  • Fig. 6 depicts a system 600 for implementing the method according to the invention previously described.
  • the system 600 comprises:
  • a detecting (620) unit for detecting a laser beam (C) arriving at an area previously written by another laser beam (D).
  • the detecting (620) unit may detect the address information previously written by said another laser beam (D) to confirm whether the laser beam (C) arrives at the area previously written by said another laser beam (D).
  • checking (630) unit for checking the writing quality of the area written by the laser beam (C) that arrived at the area.
  • the checking (630) unit controls the laser beam (C) that arrived at the area to read data in the area, so as to check the writing quality of the read back data.
  • an adjusting (640) unit for adjusting the writing power of said another laser beam (D) according to the checked writing quality.
  • the adjusting value of the writing power depends on the checked writing quality and a predefined writing quality threshold. If the checked writing quality is far from the threshold, the adjusting value is larger; if the checked writing quality is near to the threshold, the adjusting value is smaller; if the checked quality is equal to the threshold, the adjusting value can be zero. Normally, the likelihood of the adjusting value being zero is very low.
  • the plurality of laser beams are positioned along inner tracks to outer tracks of the optical disc, and the outermost laser beam (D) is symmetrical with the innermost laser beam (A).
  • the system 600 further comprises: a copying (650) unit for copying the adjusted writing power of the outermost laser beam (D) to the innermost laser beam (A), if the writing is done from inner track to outer track, or copying the adjusted writing power of the innermost laser beam (A) to the outermost laser beam (D), if the writing is done from outer track to inner track.
  • a copying (650) unit for copying the adjusted writing power of the outermost laser beam (D) to the innermost laser beam (A), if the writing is done from inner track to outer track, or copying the adjusted writing power of the innermost laser beam (A) to the outermost laser beam (D), if the writing is done from outer track to inner track.
  • the writing power of each laser beam which has a symmetrical laser beam can also be obtained by copying a previously adjusted writing power of a corresponding symmetrical laser beam, without the checking process and the adjusting process.
  • the system 600 further comprises: a copying (650) unit for copying the adjusted writing power of said another laser beam (C, D) to a symmetrical laser beam (B, A), if said another laser beam (C, D) has a symmetrical laser beam (B, A).
  • the system also comprises a switching (610) unit for successively switching - on the plurality of laser beams to write according to a received writing signal (WS).
  • a switching (610) unit for successively switching - on the plurality of laser beams to write according to a received writing signal (WS).
  • the system further comprises a shifting (660) unit for simultaneously shifting all the laser beams (A, B, C, D) to a subsequent position for a subsequent writing revolution, if each laser beam has obtained a writing power by the adjusting (640) unit or the copying (650) unit.
  • the shifting (660) may also be used to output a next writing signal (NWS) to start the subsequent writing revolution.
  • This shifting implies a simultaneous displacement of all the laser beams (A, B, C, D), for example via a translation movement along a radial direction of the optical disc.
  • the shift could be done via similar actuation units (not shown) usually in charge of displacing a laser beam along the radial direction.
  • the word 'comprising' does not exclude the presence of elements or steps not listed in a claim.
  • the word "a” or “an” preceding an element does not exclude the presence of a plurality of such elements.
  • the invention can be implemented by means of hardware comprising several distinct elements and by units of a suitable programmed computer. In the unit claims enumerating several units, several of these units can be embodied by one and the same item of hardware.
  • the usage of the words first, second and third, etcetera does not indicate any ordering. These words are to be interpreted as names.

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

Abstract

L'invention concerne un procédé de commande de puissances d'écriture pour une pluralité de faisceaux laser pendant l'écriture d'un disque optique, ledit procédé comprenant les étapes consistant à : - détecter (520) un faisceau laser (C) arrivant sur une surface précédemment écrite par un autre faisceau laser (D), - vérifier (530) la qualité d'écriture de la surface écrite par le faisceau laser (C) qui est arrivée sur la surface, et - ajuster (540) la puissance d'écriture dudit autre faisceau laser (D) selon la qualité d'écriture vérifiée.
PCT/IB2007/053061 2006-08-18 2007-08-03 Procédé et système pour commander des puissances d'écriture pour une pluralité de faisceaux laser Ceased WO2008020358A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN200610111091 2006-08-18
CN200610111091.1 2006-08-18

Publications (2)

Publication Number Publication Date
WO2008020358A2 true WO2008020358A2 (fr) 2008-02-21
WO2008020358A3 WO2008020358A3 (fr) 2008-04-17

Family

ID=38988056

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2007/053061 Ceased WO2008020358A2 (fr) 2006-08-18 2007-08-03 Procédé et système pour commander des puissances d'écriture pour une pluralité de faisceaux laser

Country Status (2)

Country Link
TW (1) TW200814011A (fr)
WO (1) WO2008020358A2 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08147744A (ja) * 1994-11-16 1996-06-07 Canon Inc 光記録装置
US5856964A (en) * 1997-04-15 1999-01-05 Eastman Kodak Company Multihead optical disc drives with direct reading after writing operation
US6483797B1 (en) * 1999-08-20 2002-11-19 Lots Technology, Inc. Apparatuses and methods for reading after writing in optical recording systems

Also Published As

Publication number Publication date
WO2008020358A3 (fr) 2008-04-17
TW200814011A (en) 2008-03-16

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