WO2008001164A1 - Enregistrement optique à grande vitesse - Google Patents

Enregistrement optique à grande vitesse Download PDF

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Publication number
WO2008001164A1
WO2008001164A1 PCT/IB2006/053764 IB2006053764W WO2008001164A1 WO 2008001164 A1 WO2008001164 A1 WO 2008001164A1 IB 2006053764 W IB2006053764 W IB 2006053764W WO 2008001164 A1 WO2008001164 A1 WO 2008001164A1
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WO
WIPO (PCT)
Prior art keywords
level
laser
write
pattern
laser beam
Prior art date
Application number
PCT/IB2006/053764
Other languages
English (en)
Inventor
Johannes Cornelis Norbertus Pijpers
Johannes Hubertus Godefriedus Jaegers Jaegers
Bart Michiel Boer
Jean Schleipen
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.
Priority to TW096122096A priority Critical patent/TW200818148A/zh
Publication of WO2008001164A1 publication Critical patent/WO2008001164A1/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
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/0045—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
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/006—Overwriting
    • G11B7/0062—Overwriting strategies, e.g. recording pulse sequences with erasing level used for phase-change media
    • 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

  • An aspect of the invention relates to an optical recorder that comprises a laser driver for generating a laser drive signal.
  • the optical recorder may be used for, for example, high- speed recording in accordance with the so-called Blu-ray Disc standard (Blu-ray Disc is a registered trademark of the Blu-ray Disc Association).
  • Other aspects of the invention relate to a laser driver, which may be in the form of an integrated circuit, a method of optical recording, a method of defining a pattern for a laser drive signal, a computer program product for defining a pattern for a laser drive signal, and a signal for driving a laser in an optical recorder.
  • Optical recorders typically record data on an optical carrier by projecting a laser beam on the optical carrier.
  • Compact disk (CD) recorders and digital versatile disk (DVD) recorders are examples, in which the optical carrier is in the form of a disk.
  • the laser beam produces a spot on the optical carrier, which moves along a given track.
  • the laser beam has a power that varies in dependence on a data signal, which is to be recorded.
  • the laser beam forms a mark on the track when the power is at a write level.
  • the laser beam leaves a space when the power is at a quiescent level.
  • a space may be more reflective than a mark, or vice versa, depending on the physical properties of the optical carrier.
  • a mark typically represents a string of ones in the data signal.
  • a space typically represents a string of zeros in the data signal.
  • a mark or a space has a length that represents the number of ones or zeros, respectively, in the string concerned.
  • An optical recorder typically comprises a laser driver, which generates a laser drive signal that modulates the power of the laser beam.
  • the laser driver should preferably ensure that marks and spaces, which are written on the optical carrier, precisely represent the data signal to be recorded. There is a nominal length for each number of ones or zeros that a mark or a space, respectively, may represent.
  • a reading error may occur if, for example, the length of a mark that has been written exceeds the nominal length to a relatively great extent. The mark is too long as it were. In that case, an optical reader may produce one or more ones too many when reading the mark. Conversely, a reading error may occur if the mark is too short. The optical reader may produce one or more ones too few.
  • the power modulation of the laser beam determines to relatively great extent the length of a mark. Consequently, a precise writing of marks and spaces, which avoids reading errors, involves a precise laser beam power modulation.
  • a laser driver may provide precise laser beam power modulation on the basis of a driver clock signal and a pattern definition for each different length that a mark may have.
  • the driver clock signal has a given period, which will be referred to as driver clock period hereinafter.
  • the driver clock signal defines a time grid with a pitch that corresponds with the driver clock period.
  • a pattern definition which belongs to a mark of a given length, defines a particular laser beam power modulation, which is aligned on the time grid. That is, the pattern definition defines various laser beam power transitions. Each laser beam power transition occurs at a particular grid point in the time grid, which the driver clock signal defines.
  • US patent number 6,674,702 discloses a laser drive circuit that includes a drive waveform generating unit, which generates a drive waveform signal based on an input signal.
  • the drive waveform generating unit includes a drive waveform storage unit, which stores a recording strategy according to a type of disk.
  • the laser drive circuit further includes a first current supply unit, which supplies a first drive current to a first laser diode, and a second current supply unit, which supplies a second drive current to a second laser diode.
  • a switching unit selectively supplies the drive waveform signal to the first current supply unit or the second current supply unit.
  • High-speed high-density optical recording may necessitate a relatively high driver clock frequency.
  • data is optically recorded in accordance with the Blu-ray Disc standard, which allows high-density optical recording.
  • the data is optically recorded with a recording speed that is 10 times the standard playback speed.
  • the data signal that is to be recorded will have a rate of 660 Megabit per second (Mb/s).
  • Mb/s Megabit per second
  • a bit period corresponds with 1.515 nanoseconds (ns).
  • the driver clock period is several times smaller than the bit period.
  • the driver clock period may even need to be at least an order of magnitude smaller than the bit period.
  • the driver clock period may therefore need to be smaller than a few 100 picoseconds (ps), or even smaller than 100 ps.
  • ps picoseconds
  • the laser driver needs to operate at a driver clock frequency of several gigahertzes, such as, for example, 10 GHz. It will generally require much design effort and special manufacturing processes in order to realize practical laser driver implementations that operate at such a high driver clock frequency.
  • a laser drive signal in which level changes are aligned on a time grid with a given pitch, is provided with a pattern that comprises an intermediate level.
  • the intermediate level is chronologically arranged between a quiescent level for leaving a space on an optical disk track and a write level for writing a mark on the optical disk track.
  • the intermediate level is comprised between the quiescent level and the write level.
  • an intermediate level in a pattern for the laser drive signal may time shift an effective laser beam power transition, which determines where a transition between a space and a mark will occur on an optical carrier. That is, an intermediate level in the pattern for the laser drive signal may translate, as it were, into a given time shift of the effective laser beam power transition. The given time shift varies as a function of the intermediate level. Accordingly, the effective laser beam power transition can be made to occur at a particular instant by assigning an appropriate value to the intermediate level.
  • the intermediate level thus allows achieving a time resolution that is finer than the time grid, which is imposed by the driver clock signal. Accordingly, a sufficiently precise laser beam power modulation can be achieved with a lower driver clock frequency compared with conventional solutions.
  • the invention allows optical recording at moderate cost, in particular for high-density high-speed optical recording. In this respect it is noted that the invention allows a time resolution in order of a few picoseconds, which is hardly achievable with conventional solutions, if achievable at all.
  • An implementation of the invention advantageously comprises one or more of following additional features, which are described in separate paragraphs that correspond with individual dependent claims.
  • the pattern of the laser drive signal preferably comprises a pre-pulse level that is chronologically arranged between the quiescent level and the intermediate level.
  • the pre- pulse level is below a threshold level associated with a laser coupled to receive the laser drive signal.
  • a laser driver which provides the laser drive signal in accordance with the invention, preferably comprises a memory, an address generator, and a pattern generator.
  • the memory stores respective pattern definitions for the laser drive signal.
  • the address generator successively causes one of the respective pattern definitions to be read from the memory in dependence on an input data signal.
  • the pattern generator generates the laser drive signal on the basis of the respective pattern definitions that are successively read from the memory.
  • a digital-to- analog converter provides the laser drive signal on the basis of the respective values, which are read from the respective registers in response to the respective pattern definitions that are successively read from the memory.
  • respective values corresponding with respective intermediate levels are stored within respective registers.
  • the pattern generator preferably comprises a timing circuit that can be programmed by a pattern definition.
  • the timing circuit provides a series of timing pulses, which defines respective time intervals during which respective values are converted.
  • FIG. 1 is a composite diagram that illustrates a process of reading from a rewritable optical disk.
  • FIG. 2 is a composite diagram that illustrates a process of recording on a rewritable optical disk.
  • FIG. 3 is a signal diagram that illustrates a process of recording on a write-once optical disk.
  • FIG. 4 is a block diagram that illustrates an optical recorder.
  • FIG. 5 is a flow chart diagram that illustrates several operations, which the optical disk recorder carries out when a user inserts a recordable optical disk.
  • FIG. 6 is a block diagram that illustrates a laser driver, which forms part of the optical recorder.
  • FIGS. 7, 8, and 9 are signal diagrams, each of which illustrates a desired laser beam write pulse and a laser current pattern associated therewith.
  • FIG. 10 is a signal diagram that illustrates two practical laser current pulses, which the laser driver can generate.
  • FIG. 11 is a signal diagram that illustrates two laser beam power pulses, which result from the two practical laser current pulses.
  • FIGS. 12, 13, and 14 are signal diagrams, each of which illustrates a desired laser beam write pulse and an alternative laser current pattern associated therewith.
  • FIG. 15 is a flow chart diagram that illustrates a write strategy data calculation, which allows appropriate programming of the laser driver.
  • FIG. 1 illustrates a process of reading from a rewritable optical disk on which data has been recorded.
  • FIG. 1 has an upper section that is a photo of a portion of a track TR on the rewritable optical disk. The photo shows that the optical disk track TR comprises amorphous regions and crystalline regions. The amorphous regions have a relatively uniform, grayish shading. An amorphous region constitutes a mark. A crystalline region constitutes a space. These regions are formed in a phase change material of a particular type.
  • FIG. 1 has a lower section, which illustrates the process of reading from the optical disk track TR.
  • the lower portion comprises a graph with a horizontal axis, which represents time T, and a vertical axis, which represents reflectivity R.
  • a horizontal dashed line represents a reflectivity threshold Rth, which is commonly referred to as "slicer level".
  • Vertical grid lines represent channel clock periods Teh within an optical disk reader that reads the optical disk track TR at a correct speed. Accordingly, the optical disk reader reads a particular point on the optical disk track TR at a particular instant, both of which correspond with a particular point on the horizontal axis.
  • the graph comprises a curve that, for any given instant, indicates the reflectivity of the point on the optical disk that is read at that given instant.
  • the curve represents variations in reflectivity along the portion of the optical disk track TR, which is illustrated in the upper section of FIG. 1.
  • the curve can also be seen as representing a transducer output signal of an electro-optical interface within an optical disk reader.
  • the curve comprises negative pulses that correspond with the amorphous regions on the optical disk track TR. That is, a negative pulse represents a mark.
  • a negative pulse has a falling edge, which crosses the reflectivity threshold Rth at a particular point, and a rising edge, which crosses the reflectivity threshold Rth at another particular point. These respective points have a given distance with respect to each other, which represents the length of the mark concerned.
  • a series of so-called channel bits CHB which is represented below the graph, is generated on the basis of the curve.
  • the series of channel bits CHB constitutes channel-coded data that is read from the rewritable optical disk.
  • a decision is made on the basis of the reflectivity within the channel clock period and the reflectivity threshold Rth. This decision determines whether the channel bit for that clock period is a one (1) or a zero (0).
  • a mark on the optical disk track TR produces a string of ones.
  • a space produces a string of zeros. Consequently, the series of channel bits CHB alternately comprises strings of ones and strings of zeros.
  • the length of a mark can be expressed in terms of n T, whereby n is a natural number that corresponds with the number of ones that the mark represents, and whereby T corresponds with the channel clock period Teh.
  • the length of a space can be expressed in similar terms.
  • the portion of the optical disk track TR illustrated in FIG. 1 comprises, in order of occurrence, a 6T space, a 2T mark, a 3T space, a 3T mark, a 4T space, and a 4T mark.
  • bit error may occur if a mark has an imprecise length. A zero may be mistaken for a one, and vice versa. Nonetheless, data that has been recorded on an optical disk may correctly be reproduced even if bit errors occur in the channel-coded data that is read from the rewritable optical disk. This is because the channel-coded data is an error-correction coded version of the data that has been recorded. An error-correction algorithm is applied to the channel-coded data, which allows correction of a given amount of bit errors.
  • the data that is read from the optical disk will be corrupted if the amount of bit errors in the channel-coded data exceeds a critical threshold.
  • FIG. 2 illustrates a process of recording on a rewritable optical disk, which produces the portion of the optical disk track TR illustrated in FIG. 1.
  • FIG. 2 has an upper section that is identical to the upper section of FIG. 1, which is the photo of the portion of the optical disk track TR.
  • FIG. 2 also reproduces the series of channel bits CHB, which is below the graph in FIG. 1.
  • the series of channel bits CHB is optically recorded by subsequently writing the aforementioned marks and spaces on the optical disk track TR: the 6T space, the 2T mark, the 3T space, the 3T mark, the 4T space, and the 4T mark.
  • FIG. 2 has a lower section, which comprises a graph with a horizontal axis, which represents time T, and a vertical axis, which represents laser beam power PW.
  • Vertical grid lines represent channel clock periods Teh within an optical disk recorder. It is assumed that the optical disk spins at a correct speed.
  • the laser beam power PW hits a particular point on the optical disk track TR at a particular instant, both of which correspond with a particular point on the horizontal axis.
  • the graph comprises a curve that, for any given instant, indicates the laser beam power PW that hits of the point on the optical disk at that given instant.
  • the curve thus represents modulation of the laser beam power PW along the portion of the optical disk track TR, which is illustrated in the upper section of FIG. 2.
  • the curve can also be seen as representing a laser current that drives a laser, which produces the laser beam power PW.
  • the laser beam power PW can have three different levels: a bias level Pb, an erase level Pe, and a write level Pw.
  • the laser beam power PW is switched between these three levels in dependence on the series of channel bits CHB that are to be written on the optical disk.
  • the series of channel bits CHB comprise a string of two successive ones, which is surrounded by zeros, for which the 2T mark should be written on the optical disk track TR.
  • a mark is written by switching the laser beam power PW in accordance with a particular pattern.
  • the laser beam power pattern for the 2T mark comprises two relatively short write pulses.
  • the respective laser beam power pattern for the 3T mark and the 4T mark comprise three and four relatively short write pulses, respectively.
  • a write pulse heats the optical disk track TR. Each write pulse is followed by an interval of time during which the laser beam power PW is at the bias level Pb. This corresponds with a relatively short cooling period, which prevents a mark from becoming too large.
  • Each laser beam power pattern illustrated in FIG. 2 comprises a similar first write pulse and a similar last write pulse.
  • the respective first write pulses have the following in common.
  • the laser beam power PW is switched from the erase level Pe to the write level Pw shortly before the channel clock period in which the first one (1) occurs.
  • the laser beam power PW is subsequently switched from the write level Pw to the bias level Pb at the beginning of this channel clock period.
  • the respective last write pulses are each followed by a relatively long time interval during which the laser beam power PW is at the bias level Pb.
  • the laser beam power pattern for the 3T and 4T marks comprise one or more middle write pulses.
  • the respective middle write pulses each have a rising edge from the bias level Pb to the write level Pw and a corresponding falling edge, from the write level
  • FIG. 3 illustrates a process of recording on a write-once optical disk, which may comprise, for example, a Cu:Si alloy as recording material.
  • FIG. 3 is a graph similar to the graph in FIG. 2.
  • a horizontal axis represents time T.
  • a vertical axis represents laser beam power PW.
  • Vertical grid lines represent channel clock periods Teh within an optical disk recorder.
  • a series of channel bits CHB, which needs to be recorded on the optical disk, is represented below the graph.
  • the laser beam power PW can have five different levels: a cool level Pc, a bias level Pb, and three different write levels: a first write level PwI, a second write level Pw2, and a third write level Pw3.
  • the laser beam power PW is switched between these five levels in dependence on the channel bits CHB, which are to be written on the optical disk.
  • the channel bits CHB comprise a string of two ones, which is surrounded by zeros, for which a 2T mark should be written on the write-once optical disk.
  • the channel bits CHB comprise a string of five ones, which is surrounded by zeros, for which a 5T mark should be written on the write-once optical disk.
  • FIGS. 2 and 3 In terms of laser beam power modulation, there is a significant difference between the processes illustrated in FIGS. 2 and 3.
  • FIG. 2 which concerns the rewritable optical disk, there are various write pulses for each mark.
  • FIG. 2 illustrates a particular example in which the number of write pulses is equal to the length of the mark in terms of channel clock periods Teh.
  • FIG. 3 which concerns the write -once optical disk, there is a single write pulse for each mark.
  • the cool level Pc is used for introducing a relatively short cooling period immediately after a write pulse, as in FIG. 2. That is, the cool level Pc forms part of a mark writing process, as in FIG. 2.
  • the bias level Pb which is somewhat higher than the cool level Pc, is used for leaving a space.
  • the single write pulse for the 2T mark exclusively comprises the second write level Pw2.
  • the single write pulse for the 5T mark comprises various levels.
  • This single write pulse begins and ends with the third write level Pw3, which is relatively high.
  • the single write pulse has the first write level PwI in a middle portion.
  • the first write level PwI is somewhat lower than the third write level Pw3.
  • This fashion of writing a mark can be characterized as "thermo balanced writing".
  • the recording material is heated to relatively great extent at the beginning and at the end of the mark.
  • the recording material is heated to a lesser extent in the middle portion of the mark. This allows writing a relatively long mark with relatively great precision.
  • the laser beam power patterns illustrated in FIG. 2 form part of a write strategy for a rewritable optical disk of a particular type.
  • the laser beam power patterns illustrated in FIG. 3 form part of a write strategy for a write-once optical disk of a particular type.
  • a write strategy defines the respective levels of a laser beam power pattern and the respective instants when the laser beam power PW needs to be switched from one level to another level.
  • the write strategy may depend on the type of recording material. For example, a write strategy with various write pulses for a mark, as illustrated in FIG. 2, can be used for a write-once optical disk. In any case, precise timing is essential in order to ensure that each mark has an appropriate length.
  • the mark may be too short or too long or may be displaced, or both.
  • Such an imprecise mark may cause a bit error in an optical disk player, which reads the optical disk.
  • FIG. 4 illustrates an optical disk recorder ODR, which operates, for example, in accordance with the so-called Blu-ray Disc standard.
  • the optical disk recorder ODR is capable of storing input data on an optical disk DSK so that another apparatus, which can operate in accordance with the same standard, can reproduce the input data that has been stored on the optical disk DSK.
  • the optical disk DSK may be of a write-once type or of a rewritable type.
  • the optical disk recorder ODR comprises various functional entities: an input interface INP, an error-correction coder ERC, a channel coder CHC, a laser driver LDR, and an electro-optical interface EOI, which includes a laser LA. These functional entities constitute a recording path.
  • the optical disk recorder ODR further comprises a reader RDR.
  • the electro-optical interface EOI and the reader RDR constitute a reproduction path, which can reproduce data that is present on the optical disk.
  • the optical disk recorder ODR further comprises a disk rotation motor DRM and a load mechanism LDM, which are electromechanical entities.
  • the optical disk recorder ODR further comprises functional entities at a system level: a clock generator CKG, a controller CTRL, and a system memory MEMS.
  • the clock generator CKG provides a channel clock signal CCK, which defines the channel clock periods Teh illustrated in FIGS. 2 and 3.
  • the controller CTRL may interact with a user interface, such as, for example, a remote control device RCD.
  • the system memory MEMS comprises generic descriptions of various write strategies WSl, WS2, WS3, ... and a write strategy implementation program PWS.
  • a generic write strategy description specifies, in a behavioral fashion, an appropriate set of laser beam power patterns that should be used for writing data on a particular type of disk.
  • a particular type of disk has specific physical properties, which determine the appropriate set of laser beam power patterns for that particular type of disk. Consequently, the write strategy may differ from one disk to another.
  • the optical disk recorder ODR which is functionally represented in FIG. 4, can be implemented in numerous different manners.
  • the system memory MEMS may comprise a nonvolatile memory module for storing the generic write strategy descriptions WSl, WS2, WS3, ... and the write strategy implementation program PWS.
  • the nonvolatile memory module is preferably of the erasable and programmable type so that a generic write strategy description can be updated, as well as the write strategy implementation program PWS.
  • the laser driver LDR may be implemented in the form of a dedicated integrated circuit, which is programmable. An example will be given hereinafter.
  • a functional entity may be implemented by means of software or hardware, or a combination of software and hardware.
  • the error- correction coder ERC and the channel coder CHC may each be implemented by suitably programming a processor.
  • a software module may cause the processor to carry out specific operations that belong to the error-correction coder ERC and the channel coder CHC.
  • the controller CTRL is typically implemented in the form of a suitably programmed processor.
  • a single suitably programmed processor may form a combined implementation of various functional entities, such as, for example, the controller CTRL, the error-correction coder ERC, and the channel coder CHC.
  • each of the aforementioned functional entities may be implemented in the form of one or more dedicated circuits. This is a hardware-based implementation. Hybrid implementations may involve software modules as well as one or more dedicated circuits.
  • FIG. 5 illustrates several operations, in the form of a series of steps S1-S5, which the optical disk recorder ODR carries out when a user inserts an optical disk into the optical disk recorder ODR. It is assumed that the optical disk is a recordable optical disk, which may be of the write-once or of the rewritable type.
  • step Sl the controller CTRL receives an indication that the optical disk is inserted.
  • the controller CTRL causes the load mechanism LDM to appropriately position the optical disk (CTRL ⁇ LDM: POS[DSK]).
  • the controller CTRL activates the disk rotation motor DRM, which causes a spinning of the optical disk at an appropriate speed (CTRL ⁇ DRM: ROT[DSK]).
  • the controller CTRL activates the laser within the electro-optical interface EOI, which produces an optical spot on the optical disk for the purpose of reading (CTRL ⁇ EOI: POS[SP]).
  • the controller CTRL controls the electro-optical interface EOI so that the optical spot is on a particular track on which identification data has been stored.
  • the identification data provides general information concerning the optical disk, including type information, that is, information about the type to which the optical disk belongs.
  • step S2 the reader RDR receives a transducer output signal TO from the electro-optical interface EOI.
  • the transducer output signal TO is an analog signal of relatively small magnitude, which represents optical variations on the particular track of interest.
  • the transducer output signal TO may be similar to the curve in FIG. 1.
  • the read data RD comprises the aforementioned identification data.
  • the controller CTRL receives the identification data from the reader RDR (IDeRD ⁇ CTRL).
  • step S3 the controller CTRL selects a generic write strategy description WS* on the basis of the identification data, which includes type information (CTRL: ID ⁇ WS*).
  • the sign "*" is a wildcard, which indicates that the selected generic write strategy description WS* may be any of the generic write strategy descriptions WSl, WS2, WS3, ... that are present in the system memory MEMS.
  • the generic write strategy description WS* which the controller CTRL selects, applies to the type to which the optical disk belongs.
  • the controller CTRL loads the generic write strategy description WS* of interest into a working memory(CTRL ⁇ MEMS: LD[WS*]).
  • the controller CTRL further loads the write strategy implementation program PWS into the working memory (CTRL ⁇ MEMS: LD[PWS]).
  • step S4 the controller CTRL executes the write strategy implementation program PWS.
  • step S5 the controller CTRL loads the write strategy data WSD into the laser driver LDR (CTRL ⁇ LDR: LD[WSD]).
  • the laser driver LDR has a functional behavior that depends on the write strategy data WSD, which has been loaded into the laser driver LDR. More specifically, the write strategy data WSD causes the laser driver LDR to provide a particular output signal, which drives the laser LA, in response to a particular sequence of bits, which the channel coder CHC applies to the laser driver LDR. This will be discussed in greater detail hereinafter.
  • step S5 the optical disk recorder ODR is ready to record data on the optical disk.
  • Data recording involves a signal flow through the recording path, which will be discussed hereinafter with reference to FIG. 4.
  • the input interface INP of the optical disk recorder ODR receives an input signal IS, which may be analog or digital.
  • the input interface INP converts the input signal IS into a digital signal, which may temporarily be stored in a buffer memory.
  • the input signal IS may directly be applied to the buffer memory for temporary storage.
  • the input interface INP may further carry out a data rate conversion when the input signal IS and the recording path have different data rates.
  • the error-correction coder ERC receives write data WD from the input interface INP.
  • the write data WD represents at least a portion of the input signal IS, which should be recorded on the optical disk.
  • the error-correction coder ERC applies an error-correction encoding algorithm to the write data WD. Accordingly, the error-correction coder ERC provides error-protected data ED, which comprises a given amount of redundancy.
  • the write data WD can correctly be retrieved from the error-protected data ED, even if a part of the error- protected data ED is corrupted.
  • the channel coder CHC converts the error-protected data ED into channel-coded data CD.
  • the channel-coded data CD has a format that facilitates optical recording.
  • the channel- coded data CD typically comprises strings of bits that have an identical value as illustrated in FIGS. 1, 2, and 3. Each string has a length, which is comprised in a predefined range.
  • the Blu-ray Disc standard defines that the minimum length is 2 and the maximum length is 8 in terms of number of channel bits.
  • a string of ones corresponds with a mark on the optical disk. The mark should have a length that corresponds with the length of the string of ones, as illustrated in FIG. 2.
  • a string of zeros corresponds with a space on the optical disk. The space should have a length that corresponds with the length of the string of zeros, as illustrated in FIG. 2.
  • the laser driver LDR generates a laser current LC on the basis of the channel-coded data CD and the write strategy data WSD, which the controller CTRL has loaded into the laser driver LDR.
  • the write strategy data WSD defines particular patterns for the laser current
  • the laser driver LDR causes the laser current LC to have the particular laser current pattern that belongs to that given length as specified by the write strategy data WSD.
  • This particular laser current pattern should cause the laser LA to write a mark of a given length on the optical disk.
  • the laser driver LDR plays an important role in the optical disk recorder ODR.
  • the laser driver LDR and the electro-optical interface EOI effectively transform a string of ones in the channel-coded data CD into a mark on the optical disk.
  • the mark should have a precise length, which depends on the number of ones in the string, in order to promote that an optical disk player precisely reproduces the string of ones when reading the mark. More specifically, the mark should have a length that is within a relatively narrow range, which is characteristic for the number of ones within the string concerned. A reading error will occur if the length of the mark is outside this specific range, that is, if the mark is too short or too long. Consequently, the laser driver LDR can reduce the probability of readings errors by writing marks of precise length.
  • FIG. 6 illustrates the laser driver LDR, which forms part of the optical disk recorder ODR illustrated in FIG. 4.
  • the laser driver LDR comprises the following functional entities: an address generator ADG, a driver memory MEMD, a buffer FIFO of the f ⁇ rst-in first-out type, a digital pattern generator DPG, and a digital-to-analog converter DAC. These functional entities constitute a driver path, which transforms the channel-coded data CD into laser current patterns.
  • the driver path transforms the channel-coded data CD into laser current patterns in a particular fashion, which depends on the write strategy data WSD that has been loaded into the driver memory MEMD.
  • the laser driver LDR further comprises a phaselock loop PLL, which receives the channel clock signal CCK.
  • the aforementioned functional entities of the laser driver LDR may form part of, for example, an integrated circuit.
  • the driver memory MEMD may be in the form of, for example, a random access memory.
  • the laser driver LDR operates as follows.
  • the address generator ADG receives the channel-coded data CD, which may be in a run-length encoded form. In that case, the address generator ADG may apply a run-length decoding to the channel-coded data CD, so as to obtain the zeros and the ones that constitute the channel-coded data CD.
  • the address generator ADG recognizes, as it were, respective strings of ones in the channel-coded data CD. Each string constitutes a particular mark that needs to be written.
  • the address generator ADG may comprise a lookup table, which associates particular address data ADD with each particular length that a string of ones may have.
  • the address generator ADG generates the address data ADD that belongs to a particular length, when a string of ones of this particular length occurs in the channel-coded data CD.
  • the address generator ADG applies this address data ADD to the driver memory MEMD.
  • the address data ADD may indicate a single address in the driver memory MEMD or a set of addresses.
  • the write strategy data WSD which is stored in the driver memory MEMD, comprises a pattern definition for each length that a string of ones may have in the channel-coded data CD.
  • the pattern definition defines a particular laser current pattern, which produces a mark of an appropriate length.
  • Each pattern definition is stored in a particular address, or a particular set of addresses, as defined by the address data ADD for the length concerned in the aforementioned lookup table. Consequently, the driver memory MEMD provides a specific pattern definition PDF when a string of ones of a given length occurs in the channel-coded data CD.
  • the specific pattern definition PDF belongs to the given length of the string of ones.
  • the buffer FIFO temporarily stores successive pattern definitions PDF, which the driver memory MEMD provides in response to successive address data ADD from the address generator ADG.
  • the buffer FIFO stores the successive pattern definitions PDF on a first-in first-out basis. Accordingly, the buffer FIFO releases the pattern definition PDF that has been in the buffer FIFO for the longest time, when the buffer FIFO receives a read request
  • the digital pattern generator DPG converts a pattern definition PDF, which the buffer FIFO has released, into a series of digital values SDV and an accompanying series of timing pulses TP.
  • the digital pattern generator DPG may comprise a set of registers RGl, RG2, RG3, ... and a timing circuit TIM, as illustrated in FIG. 6.
  • Respective registers RGl, RG2, RG3, ... store respective digital values DVl, DV2, DV3, ..., which corresponds with respective laser current levels.
  • the pattern definition PDF may comprise, for example, several bits that define a particular level by designating a particular register.
  • the laser beam power patterns illustrated in FIG. 2 comprises the following laser beam power levels: the bias level Pb, the erase level Pe, and the write level Pw.
  • a first register RGl in the digital pattern generator DPG may store a digital value DVl that corresponds with the bias level Pb.
  • a second register RG2 may store a digital value DV2 that corresponds with the erase level Pe.
  • a third register RG3 may store a digital value DV3 that corresponds with the write level Pw.
  • the digital pattern generator DPG comprises further registers, which store so-called intermediate values. This will be explained in greater detail hereinafter.
  • the timing circuit TIM generates the series of timing pulses TP, which accompanies the aforementioned series of digital values SDV.
  • the first of the two successive timing pulses defines an instant when the digital-to-analog converter DAC should begin converting the digital value concerned.
  • the last of the two successive timing pulses defines an instant when the digital-to-analog converter DAC should end converting the digital value concerned and begin converting another digital value, which succeeds the digital value concerned. Consequently, two successive timing pulses, which belong to a particular digital value, determine an interval of time during which the digital-to-analog converter DAC should convert that particular digital value.
  • the digital-to-analog converter DAC generates the laser current LC on the basis of the series of digital values SDV and the accompanying series of timing pulses TP, which the digital pattern generator DPG provides. More specifically, the digital-to-analog converter
  • the DAC converts the digital value that the symbolic digital pattern generator DPG provided when the most recent timing pulse occurred.
  • the laser current LC has a magnitude, which depends on the digital value that the digital pattern generator DPG provided when the most recent timing pulse occurred. Consequently, the magnitude of the laser current M[LC] can only change when a timing pulse occurs.
  • the timing circuit TIM generates the series of timing pulses TP on the basis of a driver clock signal DCK, which the digital pattern generator DPG receives from the phaselock loop PLL.
  • the timing circuit TIM may comprise a set of counters, which receives the driver clock signal DCK.
  • Respective counters are associated with respective digital values that the pattern definition PDF specifies.
  • a counter defines the interval of time during which the digital value, which is associated with the counter, determines the magnitude of the laser current M[LC].
  • the respective counters are programmed on the basis of the pattern definition PDF so that the respective intervals of time for the respective digital values correspond with a desired laser beam power pattern.
  • a first counter is associated with a first digital value, which occurs in the pattern definition PDF.
  • the timing circuit TIM issues a timing pulse at the instant when the first counter starts counting.
  • the first counter is programmed so that the counter counts a specific number of driver clock periods, which is defined in the pattern definition PDF.
  • the specific number of driver clock periods corresponds with the time interval during which the first digital value should determine the magnitude of the laser current M[LC].
  • the timing circuit TIM issues a timing pulse at the instant when the first counter has counted the specific number of driver clock periods.
  • a second counter which is associated with a second digital value, is enabled at that instant.
  • the second counter is programmed to count a specific number of driver clock periods, which is defined in the pattern definition PDF.
  • the specific number of driver clock periods corresponds with the time interval during which the second digital value should determine the magnitude of the laser current
  • the timing circuit TIM issues a timing pulse at the instant when the second counter has counted the specific number of driver clock periods. Further counters may be programmed to provide further timing pulses for further digital values in a similar manner.
  • the phaselock loop PLL generates the driver clock signal DCK on the basis of the channel clock signal CCK.
  • the phaselock loop PLL operates as a frequency multiplier.
  • the driver clock signal DCK typically has a frequency that is a multiple of the channel clock frequency. This multiple will be referred to as frequency multiplication factor K.
  • the driver clock signal DCK thus has a period that is equal to the channel clock period divided by the frequency multiplication factor K.
  • the driver clock signal DCK defines a time grid with a pitch that is equal to the driver clock period.
  • the magnitude of the laser current M[LC] can only change at a grid point in this time grid. This is because the timing circuit TIM can only provide a timing pulse at a grid point.
  • K 5.
  • the laser current LC should produce laser beam power patterns that fully comply with the selected generic write strategy description WS*.
  • the driver clock signal DCK should provide a sufficiently fine time grid in order to achieve such fully compliant laser beam power patterns.
  • the time grid should comprise a grid point for each possible instant when the laser beam power could be switched in accordance with the selected generic write strategy description WS*. This may require a relatively great number of grid points per channel clock period, which implies that the frequency multiplication factor K should be relatively high.
  • FIG. 2 represents an ideal laser beam power pattern for the writing of the 2T mark.
  • FIG. 2 illustrates that the laser beam power should be switched from the erase level Pe to the write level Pw at a particular instant. This particular instant lies somewhere between the beginning and the end of the channel clock period that immediately precedes the string of two ones for which the 2T mark needs to be written.
  • This particular instant may be expressed as a negative offset from the beginning of the channel clock period for the first of the two zeros.
  • the negative offset can be expressed in terms of a fraction of the channel clock period. Let it be assumed that the negative offset is equal to 3/10 of the channel clock period. In that case, the frequency multiplication factor K should conventionally be 10 so that the driver clock period is 1/10 of the channel clock period.
  • the channel clock frequency is relatively high in the case of high-speed high-density recording such as, for example, in accordance with the Blu-ray Disc standard.
  • the Blu-ray Disc standard defines a nominal channel clock frequency of 66 Megahertz (MHz), which corresponds with a nominal channel clock period of 15.151 nanoseconds (ns).
  • the nominal channel clock frequency applies to a standard playback speed, whereby 66 million channel bits are read per second.
  • High-speed recording may involve writing R times 66 million channel bits on an optical disk, R being a natural number, which is often referred to as "speed race factor".
  • a speed race factor R of 10 is desired for an optical recording in accordance with the Blu-ray Disc standard.
  • the channel clock frequency is 10 times 66 MHz.
  • the channel clock period is 1.515 ns, which is 1/10 of the standard channel clock period.
  • the driver clock signal DCK should provide a time grid with a grid point for each power-switching instant in the selected generic write strategy description WS*.
  • the driver clock period should be 1/10 of the channel clock period. In that case, the driver clock period should be 151.5 picoseconds (ps), which corresponds with a frequency of 6.6 Gigahertz (GHz).
  • FIGS. 7, 8, and 9 illustrate three desired laser beam write pulses LBPl, LBP2, LBP3 respectively, by means of relatively thick broken lines.
  • FIGS. 7, 8, and 9 each comprise a graph with a horizontal axis, which represents time T in units of nanoseconds (ns), and a vertical axis, which represents the magnitude of the laser current M[LC].
  • Vertical grid lines represent the time grid.
  • the vertical axis indicates a bias level Pb and a write level Pw.
  • the three desired laser beam write pulses LBPl, LBP2, LBP3 may each be considered as a simplified version of any write pulse illustrated in FIG. 2 or in FIG. 3.
  • the bias level Pb that precedes the three desired laser beam write pulses LBPl, LBP2, LBP3 is a generic representation of a start level of a laser beam power transition from low to high.
  • the bias level Pb that precedes the three desired laser beam write pulses LBPl, LBP2, LBP3 may corresponds with the erase level Pe in FIG. 2.
  • the bias level Pb that succeeds the three desired laser beam write pulses LBPl, LBP2, LBP3 is a generic representation of an end level of a laser beam power transition from high to low.
  • the bias level Pb that succeeds the three desired laser beam write pulses LBPl, LBP2, LBP3 may corresponds with the cool level Pc in FIG. 3.
  • the laser beam power should be at the write level Pw in a time interval that extends from 0.875 ns to 3.875 ns.
  • the laser beam power should be switched from the bias level Pb to the write level Pw at 0.875 ns and should be switched back from the write level Pw to the bias level Pb at 3.875 ns.
  • the laser beam power should be switched from the bias level Pb to the write level Pw at 0.95 ns and should be switched back from the write level Pw to the bias level Pb at 3.95 ns.
  • the laser beam power should be switched from the bias level Pb to the write level Pw at 0.8 ns and should be switched back from the write level Pw to the bias level Pb at 3.8 ns.
  • the time grid does not allow switching the magnitude of the laser current M[LC] at any of these instants.
  • FIGS. 7, 8, and 9 each illustrate a laser current pattern in gray shading.
  • Each laser current pattern will cause the laser to produce the desired laser beam write pulse illustrated in the same figure, or at least a sufficiently good approximation thereof. This is possible despite the fact that the magnitude of the laser current M[LC] can only change at an instant that is a multiple of 0.25 ns, which excludes switching at any of the aforementioned instants that characterize the respective desired laser beam write pulses. It should be noted that a delay, which may occur in a signal path between the laser driver LDR and the laser LA, has been ignored in FIGS. 7, 8, and 9, for the sake of complicity
  • the respective laser current patterns comprise a write level Pw and a bias level Pb that correspond with the write level Pw and the bias level Pb, respectively, of the laser beam power. That is, the laser beam power will typically have the write level Pw when the magnitude of laser current LC is at the write level Pw. The laser beam power will typically have the bias level Pb when the magnitude of the laser current M[LC] is at the bias level Pb.
  • the respective laser current patterns further have the following in common.
  • the magnitude of the laser current M[LC] is at the write level Pw in each driver clock period during which the laser beam power should exclusively be at the write level Pw. Consequently, in FIGS. 7, 8, and 9, the magnitude of the laser current M[LC] is at the write level Pw from 1 ns to 3.75 ns. This is the largest possible time-grid aligned interval that fits within the time interval in which the laser beam power should be at the write level Pw.
  • the magnitude of the laser current M[LC] is at the bias level Pb in each driver clock period during which the laser beam power should exclusively be at the bias level Pb. Consequently, in FIGS. 7, 8, and 9, the magnitude of the laser current M[LC] is at the bias level Pb from 0 ns to 0.75 ns and from 4.0 ns onwards.
  • the laser current pattern illustrated in FIG. 7 comprises a 50% intermediate level Pi50%, which is halfway the bias level Pb and the write level Pw.
  • the magnitude of the laser current M[LC] is at the 50% intermediate level Pi50% during the driver clock period 0.75- 1.0 ns.
  • the laser beam power should be switched from the bias level Pb to the write level Pw in this driver clock period.
  • the 50% intermediate level Pi50% produces a bias-to-write level transition in the laser beam power that has an effective transition point at 0.875 ns. This is precisely the instant when the laser beam power should be switched from the bias level Pb to the write level Pw.
  • the bias-to-write level transition which the 50% intermediate level Pi50% produces, substantially corresponds with a bias-to-write level transition that would have been obtained if the laser current LC was switched at 0.875 ns.
  • the magnitude of the laser current M[LC] is also at the 50% intermediate level Pi50% during the driver clock period 3.75-4.0 ns in which the laser beam power should be switched back from the write level Pw to the bias level Pb.
  • the 50% intermediate level Pi50% produces a write-to-bias level transition in the laser beam power that has an effective transition point at 3.875 ns, which is the instant when the laser beam power should be switched back from the write level Pw to the bias level Pb.
  • the bias-to-write level transition, which the 50% intermediate level Pi50% produces substantially corresponds with a write-to-bias level transition that would have been obtained if the laser current LC was switched at 3.875 ns.
  • the laser current pattern illustrated in FIG. 8 comprises a 20% intermediate level Pi20% and an 80% intermediate level Pi80%.
  • the 20% intermediate level Pi20% corresponds with the bias level Pb to which 20% of the difference between the write level Pw and the bias level Pb has been added.
  • the 80% intermediate level Pi80% corresponds with the bias level Pb to which 80% of the difference between the write level Pw and the bias level Pb has been added.
  • the magnitude of the laser current M[LC] is at the 20% intermediate level Pi20% during the driver clock period 0.75-1.0 ns in which the laser beam power should be switched from the bias level Pb to the write level Pw.
  • the 20% intermediate level Pi20% produces a bias- to-write level transition in the laser beam power that has an effective transition point at 0.95 ns. This is precisely the instant when the laser beam power should be switched from the bias level Pb to the write level Pw.
  • the bias-to-write level transition, which the 20% intermediate level Pi20% produces substantially corresponds with a bias-to-write level transition that would have been obtained if the laser current LC was switched at 0.95 ns.
  • the magnitude of the laser current M[LC] is at the 80% intermediate level Pi80% during the driver clock period 3.75-4.0 ns in which the laser beam power should be switched back from the write level Pw to the bias level Pb.
  • the 80% intermediate level Pi80% produces a write-to-bias level transition in the laser beam power that has an effective transition point at 3.95 ns. This is precisely the instant when the laser beam power should be switched back from the write level Pw to the bias level Pb.
  • the write-to-bias level transition which the 80% intermediate level Pi80% produces, substantially corresponds with a write-to-bias level transition that would have been obtained if the laser current LC was switched at 3.95 ns.
  • the laser current pattern illustrated in FIG. 9 also comprises the 20% intermediate level Pi20% and the 80% intermediate level Pi80%. However, these intermediate levels have swapped positions with respect to FIG. 8.
  • the magnitude of the laser current M[LC] is at the 80% intermediate level Pi80% during the driver clock period 0.75-1.0 ns in which the laser beam power should be switched from the bias level Pb to the write level Pw.
  • the magnitude of the laser current M[LC] is at the 20% intermediate level Pi20% during the driver clock period 3.75-4.0 ns in which the laser beam power should be switched back from the write level Pw to the bias level Pb.
  • the 80% intermediate level Pi80% produces a bias-to-write level transition in the laser beam power that has an effective transition point at 0.8 ns.
  • the 20% intermediate level Pi20% produces a write-to-bias level transition in the laser beam power that has an effective transition point at 3.8 ns. This is precisely the instant when the laser beam power should be switched back from the write level Pw to the bias level Pb.
  • the bias-to-write level transition which the 80% intermediate level Pi80% produces, substantially corresponds with a bias-to-write level transition that would have been obtained if the laser current LC was switched at 0.8 ns.
  • FIGS. 7, 8, and 9 illustrate that a relatively fine time resolution for effective transition points in the laser beam power can be obtained by introducing one or more intermediate levels in the laser current LC. An effective transition point can be made to occur at an instant that lies between two successive grid points in the time grid. The instant can be defined with relatively great precision by choosing an appropriate intermediate level.
  • FIGS. 7, 8, and 9 illustrate that there is a substantially linear relationship between the intermediate level and the instant when the effective transition point occurs.
  • the effective transition point of the bias-to-write level transition is at 0.875 ns, which is halfway the driver clock period 0.75-1.0 ns. This is because the laser current LC is at the 50% intermediate level Pi50% in this driver clock period.
  • the effective transition point of the bias-to-write level transition is at 0.95 ns. In terms of driver clock periods, the effective transition point is 20% before the grid point that corresponds with 1.0 ns. This is because the laser current LC is at the 20% intermediate level Pi20% in the driver clock period 0.75-1.0 ns, which ends at this grid point.
  • the effective transition point of the bias-to-write level transition is at 0.8 ns. In terms of driver clock periods, the effective transition point is 80 % before the grid point that corresponds with
  • the effective transition point of the write-to-bias level transition occurs at 3.95 ns.
  • the effective transition point is 80% after the grid point that corresponds with 3.75 ns. This is because the laser current LC is at the 80% intermediate level Pi80% in the driver clock period 3.75-4.0 ns, which begins with this grid point.
  • the effective transition point of the write-to-bias level transition occurs at
  • the effective transition point is 20% after the grid point that corresponds with 3.75 ns. This is because the laser current LC is at the 20% intermediate level Pi20% in the driver clock period 3.75-4.0 ns, which begins with this grid point.
  • FIGS. 10 and 11 illustrate practical results, which have been obtained by introducing intermediate levels as described hereinbefore with reference to FIGS. 7, 8, and 9.
  • FIG. 10 is a graph with a horizontal axis, which represents time T in units of nanoseconds (ns), and a vertical axis, which represents the magnitude of the laser current M[LC].
  • FIG. 11 is a graph with a horizontal axis, which represents time T in units of nanoseconds (ns), and a vertical axis, which represents the laser beam power PW.
  • the practical results illustrated in FIG. 10 and 11 have been obtained with the laser driver LDR illustrated in FIG. 6.
  • the driver clock period Tdr is 250 ps.
  • FIG. 10 illustrates two practical laser current pulses that the laser driver LDR can generate: a standard laser current pulse SCP and a so-called power-controlled-transition laser current pulse XCP.
  • the standard laser current pulse SCP has been generated without any intermediate value.
  • the digital-to-analog converter DAC converts a digital value corresponding with the bias level Pb during a first time interval, subsequently converts a digital value corresponding with the write level Pw during a second time interval, and finally converts again the digital value corresponding with the bias level Pb during a third time interval.
  • Each time interval corresponds with a specific number of driver clock cycles, which the pattern definition PDF defines.
  • the power-controlled-transition laser current pulse XCP has been generated by introducing the 50% intermediate level Pi50% between the bias level Pb and the write level Pw and between the write level Pw and the bias level Pb as illustrated in FIG. 7. Referring to FIG.
  • the digital pattern generator DPG comprises a register that stores a digital value corresponding with the 50% intermediate level Pi50%.
  • the series of digital values SDV which the digital pattern generator DPG provides, comprises, in order of succession: the digital value corresponding with the bias level Pb; the digital value corresponding with the 50% intermediate level Pi50%; the digital value corresponding with the write level Pw; - the digital value corresponding with the50% intermediate level Pi50%; the digital value corresponding with the bias level Pb.
  • the digital-to-analog converter DAC converts each of these digital values during a particular time interval corresponding with a specific number of driver clock cycles defined by the pattern definition PDF.
  • the power-controlled-transition laser current pulse XCP illustrated in FIG. 10 has a bias- to-write level transition that is less steep and that occurs somewhat sooner than the corresponding transition of the standard laser current LC pulse.
  • the power- controlled-transition laser current pulse XCP has a write-to-bias level transition that is less steep and that occurs somewhat sooner than the corresponding transition of the standard laser current LC pulse.
  • FIG. 11 illustrates two laser beam power pulses: a standard laser beam power pulse SLP and a time-shifted laser beam power pulse XLP.
  • the standard laser beam power pulse SLP emanates from the laser LA in response to the standard laser current pulse SCP illustrated in FIG. 10.
  • the time-shifted laser beam power pulse XLP emanates from the laser LA in response to the power-controlled-transition laser current pulse XCP illustrated in FIG. 10.
  • the time-shifted laser beam power pulse XLP occurs 125 ps sooner than the standard laser beam power pulse SCP. This has been achieved by introducing the 50% intermediate level Pi50% as described hereinbefore.
  • the respective laser beam power pulses SLP, XLP have a substantially similar shape. More specifically, bias-to-write level transitions and write -to- bias level transitions are similar, despite differences between corresponding transitions in the respective laser current pulses SCP, XCP illustrated in FIG. 10. Since the respective laser beam power pulses SLP, XLP have a substantially similar shape, these pulses will affect optical recording material in a similar manner.
  • the standard laser current pulse SCP and the power-controlled-transition laser current pulse XCP will produce similarly shaped marks on the optical disk. Accordingly, precise time shifting can be achieved without distortion by introducing an intermediate level.
  • FIGS. 7-11 particularly apply under the two following conditions.
  • the laser LA has a relaxation oscillation period, which is greater than the driver clock period Tdr.
  • the laser LA experiences, as it were, effective control pulses having a typical rise time that is smaller than that the relaxation oscillation period of the laser LA.
  • An effective control pulse results from an output pulse from the laser driver LDR, which is effectively filtered by an electrical network that extends from the laser driver LDR to the laser LA, including the laser LA itself. That is, the laser LA has a given electrical impedance, which forms part of this electrical network.
  • an intermediate level is preferably preceded by a so-called pre-pulse.
  • the pre-pulse is an interval of time during which the laser current LC is below a threshold level, which is associated with the laser LA.
  • the threshold level of the laser LA constitutes a switch on/off point: the laser LA is effectively switched on or off depending on whether the laser current LC is above or below the threshold level, respectively.
  • the pre-pulse introduces a switch-on delay, which is a typical dynamical response of lasers, in particular injection lasers.
  • the switch-on delay contributes to translating, as it were, the intermediate level into a time shift, in particular if the aforementioned conditions do not apply.
  • FIGS. 12, 13 and 14 each illustrate an alternative laser current pattern, which comprises a pre-pulse, in gray shading.
  • FIGS. 12, 13 and 14 correspond with FIGS. 7, 8, and 9, respectively, except for the pre-pulse.
  • FIGS. 12, 13 and 14 indicate the threshold level Pth, which is associated with the laser LA.
  • the pre-pulse occurs in the driver clock period 0.5- 0.75 ns. In this driver clock period, the magnitude of the laser current M[LC] is below the threshold level Pth.
  • the driver clock period 0.5-0.75 ns in which the pre-pulse occurs immediately precedes the driver clock period 0.75-1.0 ns in which the magnitude of the laser current M[LC] is at the intermediate level.
  • FIG. 15 illustrates a write strategy data calculation, which introduces an intermediate level.
  • the write strategy data calculation comprises a series of steps S4-1, ..., S4-6, which form part of step S4 in FIG. 5.
  • the controller CTRL illustrated in FIG. 4 carries out these steps when executing the write strategy implementation program PWS. That is, the write strategy implementation program PWS comprises a set of instructions that causes the controller CTRL to carry out the write strategy data calculation illustrated in FIG. 12.
  • the write strategy data calculation is based on the selected generic write strategy description WS* and the driver clock period Tdr within the laser driver LDR.
  • step S4-1 the controller CTRL loads a generic write pulse description WRP, which is present in the selected generic write strategy description WS*, into a working register (WRPeWS*).
  • the generic write pulse description WRP defines a particular instant when the laser beam power should be switched from the bias level Pb to the write level Pw. This instant will be referred to as power-up switch instant Tsu hereinafter.
  • the generic write pulse description WRP further defines another particular instant when the laser beam power should be switched from the write level Pw to the bias level Pb. This instant will be referred to as power-down switch instant Tsd hereinafter (WRP: Tsu, Tsd).
  • the power-up grid number Gu is a natural number (Gu e K) that defines a grid point, namely the driver clock period Tdr multiplied by the power-up grid number Gu.
  • the power-up grid number Gu that is calculated defines the grid point that constitutes the best approximation of the power-up switch instant Tsu, while being somewhat later than that instant. This grid point will be referred to as power-up grid point hereinafter.
  • the power-up grid offset Toffu that is calculated is the difference between the power-up switch instant Tsu and the power-up grid point.
  • the power-up grid offset Toffu is a rational number in a range comprised between zero (0) and the driver clock period Tdr (Toffre9 ⁇ 0,Tdr>).
  • the power-up switch instant Tsu is obtained when the driver clock period Tdr is multiplied by power-up grid number Gu, which multiplication provides the power-up grid point, and the power-up grid offset Toffu is subtracted from the power-up grid point .
  • the power-up intermediate level Piu is obtained by summing the bias level Pb and a power-up offset level.
  • the power-up offset level is equal to the difference between the write level Pw and the bias level Pb multiplied by a normalized power-up grid offset.
  • the normalized power-up grid offset is equal to the power-up grid offset Toffu divided by the driver clock period Tdr. That is, the normalized power-up grid offset expresses, in units of driver clock period Tdr, the difference between the power-up switch instant Tsu and the power-up grid point.
  • the power-up intermediate level Piu varies proportionally with the (normalized) power-up grid offset Toffu.
  • the further the power-up switch instant Tsu is away from the power-up grid point the larger the power-up grid offset Toffu is, and the closer the power-up intermediate level Piu is to the write level Pw.
  • the power-down grid number Gd is a natural number (Gde K) that defines a grid point, namely the driver clock period Tdr multiplied by the power-down grid number Gd.
  • the power-down grid number Gd that is calculated defines the grid point that constitutes the best approximation of the power-down switch instant Tsd, while being somewhat sooner than that instant. This grid point will be referred to as power-down grid point hereinafter.
  • the power-down grid offset Toffd that is calculated is the difference between the power-down switch instant Tsd and the power-down grid point. Accordingly, the power-down grid offset Toffd is a rational number in a range comprised between zero
  • the power-down switch instant Tsd is obtained when the driver clock period Tdr is multiplied by power- down grid number Gd, which multiplication provides the power-down grid point, and the power-down grid offset Toffd is added to the power-down grid point.
  • the power-down intermediate level Pid is obtained by summing the bias level Pb and a power-down offset level.
  • the power-down offset level is equal to the difference between the write level Pw and the bias level Pb multiplied by a normalized power-down grid offset.
  • the normalized power-down grid offset is equal to the power-down grid offset Toffd divided by the driver clock period Tdr. That is, the normalized power-down grid offset expresses, in units of driver clock period Tdr, the difference between the power-down switch instant Tsd and the power-down grid point.
  • the power-down intermediate level Pid varies proportionally with the (normalized) power- down grid offset Toffd.
  • the further the power-down switch instant Tsd is away from the power-down grid point the larger the power-down grid offset Toffd is, and the closer the power-down intermediate level Pid is to the write level Pw.
  • step S4-6 the controller CTRL prepares write pulse generation parameters, which are send to the laser driver LDR.
  • the write pulse generation parameters constitute a translation, as it were, of the generic write pulse description WRP mentioned hereinbefore with regard to step S4-1.
  • the write pulse generation parameters define that the laser current LC should have the power-up intermediate level Piu, or a sufficiently good approximation thereof, during the driver clock period Tdr that immediately precedes the power-up grid point. That is, in terms of grid numbers, the laser current LC should have the power-up intermediate level Piu between grid number Gu-I, which immediately precedes the power-up grid number Gu, and the power-up grid number Gu itself (Piu@[(Gd-l)-Tdr, Gd-Tdr]).
  • the write pulse generation parameters further define that the laser current LC should have the power-down intermediate level Pid, or a sufficiently good approximation thereof, during the driver clock period Tdr that immediately follows the power-down grid point. That is, in terms of grid numbers, the laser current LC should have the power-up intermediate level Piu between the power-down grid number Gd and the grid number Gd+ 1, which immediately follows the power-down grid number Gd (Pid@[Gd-Tdr, (Gd+1)-Tdr]).
  • the set of registers RGl, RG2, RG3, ... within the laser driver LDR illustrated in FIG. 6, comprise a set of digital values that may be applied to the digital-to-analog converter DAC.
  • the laser driver LDR may comprise a register that stores a digital value corresponding with the 50% intermediate level Pi50% illustrated in FIG. 7.
  • the laser driver LDR may comprise further registers for storing respective digital values that correspond with respective intermediate levels in units of, for example, 10%.
  • the laser driver LDR can set the laser current LC to the 20% intermediate level Pi20% and to the 80% intermediate level Pi80% illustrated in FIGS. 8 and 9.
  • the laser driver LDR may further set the laser current LC to a 10%, a 30%, a 40%, a 60%, a 70%, and a 90% intermediate level.
  • An intermediate level which is calculated in the write strategy data calculation illustrated in FIG. 12, may not exactly correspond with any of the digital values that are stored within the laser driver LDR.
  • the write strategy data calculation may round the calculated power-up intermediate level Piu off to a nearest possible level for which the digital value is present in the laser driver LDR.
  • the set of registers RGl, RG2, RG3, ... in the laser driver LDR may be reprogrammed so that the respective registers comprise respective digital values that correspond with intermediate levels, which have been calculated.
  • the invention can be applied for recording any type of optical disk, which may be a rewritable optical disk or a write-once optical disk.
  • optical disk which may be a rewritable optical disk or a write-once optical disk.
  • FIG. 2 which relates to a rewritable optical disk
  • This immediate transmission may be replaced by a step-wise transition in accordance with the invention, which includes an intermediate level that is chronologically arranged between the erase level Pe and the write level Pw.
  • the erase level Pe is a quiescent level for leaving a space as illustrated in FIG. 2.
  • FIG. 3 which relates to a write-once optical disk, there is an immediate transition from the bias level Pb to the second write level Pw2.
  • This immediate transmission may be replaced by a step-wise transition in accordance with the invention, which includes an intermediate level that is chronologically arranged between the bias level Pb and the second write level Pw2.
  • the bias level Pb is a quiescent level for leaving a space as illustrated in FIG. 3.
  • FIGS. 7, 8, 9, 12, 13, 14 merely illustrate a few examples.
  • a time interval in which the laser drive signal has the intermediate level is limited to one driver clock period.
  • such a time interval may also comprise two or more driver clock periods.
  • Similar remarks apply to the pre-pulse, which is present in FIGS. 12, 13, 14.
  • the pre-pulse may be two or more driver clock periods long.
  • FIG. 6 merely illustrates an example, in which the laser driver comprises respective registers RGl, RG2, RG3, ... that store respective values DVl, DV2, DV3, ... corresponding with respective levels for the laser drive signal.
  • a pattern definition designates a particular level by referencing a corresponding register.
  • a pattern definition may explicitly define a particular level.
  • a laser driver need not have the aforementioned respective registers RGl , RG2, RG3, ... illustrated in FIG. 6.
  • a laser driver need not comprise a programmable memory.
  • the laser driver may only need to implement a single write strategy, which may be achieved with, for example, a read-only memory or wired logic. All what matters is that a laser driver is capable of providing a pattern that comprises an intermediate level in accordance with the invention.
  • a laser driver is capable of providing a pattern that comprises an intermediate level in accordance with the invention.
  • FIG. 15 merely illustrates an example.
  • a time offset may refer to a grid point that precedes or follows the desired switch instant.
  • a time shift need not necessarily depend on the intermediate level in accordance with a linear function. That is, that may be a nonlinear relationship between the time shift and the intermediate level.
  • the intermediate level is preferably calculated by means of nonlinear equations, or approximations thereof, which reflect that nonlinear relationship.

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

Abstract

L'invention concerne un enregistreur optique qui comprend un pilote laser permettant de générer un signal de commande de laser dans lequel les changements de niveaux sont alignés sur une trame temporelle avec un écart donné (Tdr). Le pilote laser délivre le signal de commande de laser avec un motif qui comprend un niveau intermédiaire (Pi50%). Le niveau intermédiaire (Pi50%) est disposé chronologiquement entre un niveau de repos (Pb) pour laisser un espace vide sur une piste de disque optique et un niveau d'écriture (Pw) pour écrire une marque sur la piste du disque optique. Le niveau intermédiaire (Pi50%) est compris entre le niveau de repos (Pb) et le niveau d'écriture (Pw).
PCT/IB2006/053764 2006-06-23 2006-10-13 Enregistrement optique à grande vitesse WO2008001164A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
TW096122096A TW200818148A (en) 2006-06-26 2007-06-20 High-speed optical recording

Applications Claiming Priority (2)

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CN200610093290.4 2006-06-23
CN200610093290 2006-06-23

Publications (1)

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WO2008001164A1 true WO2008001164A1 (fr) 2008-01-03

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4744055A (en) * 1985-07-08 1988-05-10 Energy Conversion Devices, Inc. Erasure means and data storage system incorporating improved erasure means
US6153063A (en) * 1996-03-11 2000-11-28 Matsushita Electric Industrial Co., Ltd. Optical information recording medium, producing method thereof and method of recording/erasing/reproducing information
WO2003071524A2 (fr) * 2002-02-22 2003-08-28 Koninklijke Philips Electronics N.V. Procedes et dispositifs servant a enregistrer des reperes sur la surface d'enregistrement d'un support d'enregistrement optique et supports d'enregistrement optique correspondants
WO2005001819A1 (fr) * 2003-06-30 2005-01-06 Samsung Electronics Co., Ltd. Support de stockage de donnees et procede et dispositif d'enregistrement et de lecture de donnees

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4744055A (en) * 1985-07-08 1988-05-10 Energy Conversion Devices, Inc. Erasure means and data storage system incorporating improved erasure means
US6153063A (en) * 1996-03-11 2000-11-28 Matsushita Electric Industrial Co., Ltd. Optical information recording medium, producing method thereof and method of recording/erasing/reproducing information
WO2003071524A2 (fr) * 2002-02-22 2003-08-28 Koninklijke Philips Electronics N.V. Procedes et dispositifs servant a enregistrer des reperes sur la surface d'enregistrement d'un support d'enregistrement optique et supports d'enregistrement optique correspondants
WO2005001819A1 (fr) * 2003-06-30 2005-01-06 Samsung Electronics Co., Ltd. Support de stockage de donnees et procede et dispositif d'enregistrement et de lecture de donnees

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