JP2006040372A - Optical disk recording device and method of recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in the recording accuracy of a short pulse width signal caused by a spot shape of an optical pickup. <P>SOLUTION: The device is provided with an astigmatic difference measuring means for measuring the amount of the astigmatic difference of a laser beam from reflected light of an optical disk, a strategy setting means for setting a recording strategy (recording power and recording pulse width) of the laser beam irradiated to the optical disk based on the amount of the measured astigmatic difference, and a recording means for recording data based on the set recording strategy. The astigmatic difference measuring means determines the amount of the astigmatic difference from a difference (A-B) between an amount (A) of a focus offset to maximize the amplitude of a push pull signal detected from a prewrite region of the optical disk and an amount (B) of a focus offset to minimize the PI error of the signal reproducing the data recorded in a prewrite region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disk recording apparatus and a recording method for optimally setting recording laser conditions, particularly a recording strategy, when recording data on an optical disk.

  As the capacity of optical discs increases and the recording speed increases, the writing conditions for optical discs are becoming stricter. In particular, during short pulse width recording such as 3T and 4T pulses in a write-once medium such as a DVD-R disc, the recording accuracy is deteriorated such that the shape of the recording mark is distorted or the recording position of the recording mark is shifted.

  Such a phenomenon is caused by residual heat due to laser light, and a good recording mark is formed by appropriately compensating the recording pulse waveform in accordance with the optical disk medium and the recording speed. Such compensation means is called a recording strategy, and the optimum values of the recording laser beam power and pulse width are determined.

  Further, as the cause of deterioration in recording accuracy, the assembly accuracy and temporal change of the optical pickup are raised, and it is necessary to cope with this. For example, the following proposals have been made as countermeasures against recording degradation caused by an optical pickup.

  Patent Document 1 measures a spot diameter of a laser beam output from an optical pickup, and sets a recording strategy that is set in advance as a function of a recording mark length that is formed corresponding to the spot diameter in accordance with variations and fluctuations in the spot diameter. A technique for correcting the recording strategy based on the amount of correction is disclosed.

  In Patent Document 2, trial writing is performed using a plurality of strategies in which the laser irradiation time is adjusted, and the irradiation time is optimized based on the result of the trial writing. Disclosed is a technology that enables this.

JP 2002-183960 A JP 2003-331427 A

  Patent document 1 measures the spot diameter of a laser beam source and corrects the recording strategy, and is effective in increasing the spot diameter. However, no consideration is given to the influence of distortion (astigmatism) of the spot shape of the laser light source.

  Japanese Patent Application Laid-Open No. 2004-228561 performs trial writing under a plurality of conditions, and corrects a recording strategy based on a result of reproducing the data. In this case, it takes time for trial writing, which hinders speeding up of the recording adjustment.

  An object of the present invention is to solve the above problems and to ensure recording accuracy in high-speed recording without performing trial writing.

  An optical disk recording apparatus according to the present invention is based on an optical pickup that irradiates a laser beam to an optical disk, an astigmatism measuring unit that measures an astigmatic difference of a laser beam from reflected light of the optical disk, and an astigmatic difference that is measured. Strategy setting means for setting a recording strategy of a laser beam to be irradiated on the optical disc, and recording means for recording data based on the set recording strategy. The recording strategy includes a laser beam recording power and a recording pulse width.

  Furthermore, it has a memory | storage means which memorize | stores the correction amount of the recording strategy with respect to the astigmatic difference amount beforehand, and a strategy setting means sets the optimal recording strategy based on this correction amount.

  The astigmatic difference measuring means includes, as the astigmatic difference amount, a focus offset amount (A) at which the amplitude of the push-pull signal detected from the prewrite area of the optical disc is maximized, and a signal obtained by reproducing the data recorded in the prewrite area The difference (A−B) from the focus offset amount (B) that minimizes the PI error is used.

  In the recording method to the optical disk of the present invention, the laser beam is irradiated onto the optical disk, the astigmatic difference amount of the laser beam is measured from the reproduction signal from the optical disk, and the optical disk is irradiated based on the measured astigmatic difference amount. A beam recording strategy is set, and data is recorded based on the set recording strategy.

  In the present invention, attention is paid to the astigmatic difference of the laser spot irradiated on the disk, and the influence is corrected. Here, the astigmatic difference means that the laser spot shape is not a perfect circle but is distorted into an ellipse. Therefore, the astigmatic difference is measured from the reproduction signal of the optical disc, and the recording strategy is corrected based on the astigmatic difference.

  According to the present invention, it is possible to quickly adjust recording conditions for ensuring recording accuracy in high-speed recording.

  Embodiments of an optical disk recording apparatus and a recording method of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an optical disk recording apparatus according to the present invention.

  When the optical disc 1 is inserted from a disc insertion opening (not shown), the spindle motor 2 rotates the linear velocity (CLV), and the optical pickup 3 records and reproduces data on the optical disc 1. The recording data is EFM modulated by the recording signal generation circuit 6, and the recording conditions (recording laser power and recording pulse width) are corrected by the strategy correction unit 5. The corrected recording pulse signal is input to the laser driver 4, and the laser driver 4 irradiates the optical disc 1 with the laser beam from the optical pickup 3 based on the input recording pulse signal.

  On the other hand, among the signals reproduced from the optical disc 1, the RF signal is amplified by the RF signal amplification circuit 7, and the reproduction data is demodulated by the data demodulation circuit 8. The focus / tracking error signal detector 9 detects a focus error signal (FE) and a tracking error signal (TE) from the read signal, and these error signals are input to the focus / tracking control circuit 10. Used for focus control and tracking control of the optical pickup 3. The system controller 11 receives the reproduction data, the focus error signal, and the tracking error signal, and analyzes the astigmatic difference therefrom. Then, based on the relationship between the astigmatism difference stored in the memory 12 and the strategy correction amount, the optimum recording strategy condition is sent to the strategy correction unit 5.

  FIG. 2 is a flowchart showing an example of a recording strategy setting using the optical disk recording apparatus of FIG.

  Here, a case where a recording strategy is set using data pre-recorded in a prewrite area of the optical disc 1 when the optical disc 1 is loaded will be described. It is assumed that data such as a disc manufacturer ID and a recommended recording strategy (laser power and light emission timing) are recorded in the prewrite area.

  In step 21, the optical pickup 3 is moved to the prewrite area of the optical disc 1 and the optical disc 1 is irradiated with laser light. While the focus offset amount is changed by the focus / tracking control circuit 10, a position where the focus error obtained from the reflected light is minimized is set as a focus offset reference point.

  In step 22, the focus / pull signal amplitude of the tracking error signal obtained from the reflected light in the prewrite area of the disc is changed to the focus / tracking error signal detector 9 while the focus / offset control circuit 10 changes the focus offset amount. To measure. Then, push-pull signal amplitude value data for each focus offset amount is sent to the system controller 11.

  In step 23, the system controller 11 obtains a focus offset amount (A) that maximizes the push-pull signal amplitude from the transmitted data.

  In step 24, the data recorded in the prewrite area of the optical disc 1 is read while changing the focus offset amount, and the PI error (parity inner error) is measured by the RF signal amplification circuit 7 and the data demodulation circuit 8. To do. Then, PI error data for each focus offset value is sent to the system controller 11.

  In step 25, the system controller 11 obtains the focus offset amount (B) that minimizes the PI error from the sent data.

  In step 26, the system controller 11 obtains an offset difference (A−B) from the focus offset amount (A) and the focus offset amount (B). This offset difference (A−B) is an amount reflecting the astigmatic difference of the laser spot emitted from the optical pickup 3 (this will be described later).

  In step 27, the strategy correction is performed based on the relationship (correction table) between the astigmatism difference amount, that is, the offset difference (AB) and the recording strategy correction amount (recording power and recording pulse width) stored in advance in the memory 12. An optimum recording strategy is set for the section 5.

  In step 28, data recording is started based on the set recording strategy.

  In the above description, the case where the recording strategy is set using the data recorded in the prewrite area of the optical disc has been described, but the present invention is not limited to this. That is, the optimum recording strategy can also be set by reproducing the signal recorded with the focus offset value that maximizes the push-pull signal in the data recording area.

  Hereinafter, the operation of each step will be specifically described.

  FIG. 3A shows an example of the relationship between the focus offset amount and the push-pull signal amplitude value in steps 22 to 23, and point A is the position where the amplitude is maximum.

  FIG. 3B shows an example of the relationship between the focus offset amount and the PI error in steps 24 to 25, and point B is the position where the error is minimized. In this embodiment, the position where the PI error is minimized is obtained as the average position of the position (C) where the PI error rapidly decreases and the position (D) where the PI error increases rapidly. The minimum position may be determined by appropriately judging from the shape of the curve.

  FIG. 3 shows the relationship between the focus offset amount, the push-pull signal, and the PI error when the astigmatic difference amount is large. FIG. 4 shows the relationship between the focus offset amount, push-pull signal, and PI error when the astigmatic difference is small.

  FIG. 5 shows an example of the relationship between the astigmatic difference amount and the recording strategy used in step 27. That is, in this relationship, when the astigmatic difference amount is small, a standard recording strategy may be used. However, when the astigmatic difference amount is large, the recording power is increased and the recording pulse width is corrected to be short. This is because in the case of a distorted laser spot with a large astigmatic difference, it is better to increase the power and to record in a short time.

  This relationship is stored in the memory 12 by experimentally obtaining an optimum condition in advance. It is possible to set the optimum condition according to the curve in the figure, and it is possible to set it continuously and faithfully to each astigmatic amount, but practically, a table that ranks the astigmatic amount is ranked. It is also possible to prepare and set a representative value for each rank.

  Further, the higher the recording speed, the shorter the recording pulse width and the larger the recording power.

  6 and 7, the measurement principle of the astigmatic difference method employed in the present invention will be described. FIG. 6 is a diagram for explaining the astigmatic difference in a model manner. When an astigmatic difference exists in the laser light source, the laser spot shape becomes an ellipse and changes from a horizontally long ellipse 61 to a vertically long ellipse 65 with respect to the focus offset position. The astigmatic difference is the distance between the position A of the shape 62 where the vertical diameter of the ellipse is minimum and the position B of the shape 64 where the horizontal diameter of the ellipse is minimum.

  FIG. 7 shows the amplitude and resolution of the reproduction signal with respect to the spot shape. When the spot shape is a horizontally long ellipse, the amplitude is large because it is along the longitudinal direction of the recording mark, but the resolution is low and the error is large. On the other hand, when the spot shape is a vertically long ellipse, the amplitude is small because it is orthogonal to the recording mark, but the resolution is high and the error is small for short pulses.

  The position A where the push-pull amplitude obtained in this embodiment is maximized is the state 62 where the spot shape is most narrowed in the circumferential direction, and the position B where the PI error is minimized is the position where the spot shape is most narrowed in the radial direction. It is the state 64. Therefore, the astigmatic difference can be obtained from the difference between the maximum amplitude position A and the minimum error position B of the reproduction signal.

  As described above, according to this embodiment, it is possible to reduce the deterioration of the recording characteristics due to the variation in astigmatism of individual lasers of the optical pickup, and to realize good recording characteristics. In addition, in this embodiment, the recording strategy adjustment is only reproduction from the optical disk, and there is no need for trial writing. Therefore, it is possible to reduce the time until recording is started.

  Moreover, it is possible to deal with when the astigmatic difference increases or decreases depending on the temperature of the use environment. That is, when writing is performed again at a certain time interval, it is possible to change the recording strategy using only the reproduction signal of the already recorded portion without performing trial writing for changes in the environmental temperature.

1 is a block diagram showing an embodiment of an optical disk recording apparatus according to the present invention. 3 is a flowchart showing an example of a recording strategy setting using the apparatus of FIG. The figure which shows an example of the relationship between a focus offset amount and a push pull signal amplitude value, and the relationship between a focus offset amount and PI error. The figure which shows an example of the relationship between a focus offset amount and a push pull signal amplitude value, and the relationship between a focus offset amount and PI error. The figure which shows an example of the relationship between an astigmatic difference amount and a recording strategy. The figure explaining an astigmatic difference like a model. The figure which shows the amplitude and resolution | decomposability of the reproduction signal with respect to a spot shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Spindle motor, 3 ... Optical pick-up, 4 ... Laser driver, 5 ... Strategy correction | amendment part, 6 ... Recording signal formation circuit, 7 ... RF signal amplification circuit, 8 ... Data demodulation circuit, 9 ... Focus tracking Error signal detector, 10... Focus / tracking control circuit, 11... System controller, 12.

Claims (10)

In an optical disc recording apparatus for recording data on an optical disc,
An optical pickup for irradiating an optical disc with a laser beam;
Astigmatism measuring means for measuring the amount of astigmatism of the laser beam from the reflected light of the optical disc;
Strategy setting means for setting a recording strategy of a laser beam irradiated on the optical disk based on the astigmatic difference amount;
Recording means for recording data based on the recording strategy;
An optical disc recording apparatus comprising: The optical disk recording apparatus according to claim 1,
The optical disc recording apparatus, wherein the recording strategy includes a recording power and a recording pulse width of a laser beam. The optical disk recording apparatus according to claim 1,
Storage means for storing the correction amount of the recording strategy for the astigmatic difference amount in advance;
The optical disc recording apparatus, wherein the strategy setting means sets the optimum recording strategy based on the correction amount. The optical disk recording apparatus according to claim 1,
The astigmatic difference measuring means includes, as the astigmatic difference amount, a focus offset amount (A) that maximizes the amplitude of the push-pull signal detected from the prewrite area of the optical disc, and data recorded in the prewrite area. An optical disc recording apparatus using a difference (A−B) from a focus offset amount (B) that minimizes a PI error of a reproduced signal. The optical disk recording apparatus according to claim 1,
The astigmatic difference measuring means records the focus offset amount (A) at which the amplitude of the push-pull signal detected from the prewrite area of the optical disc is maximized and the data recording area of the optical disc as the astigmatic difference amount. An optical disc recording apparatus using a difference (A−B) from a focus offset amount (B) that minimizes a PI error of a signal obtained by reproducing existing data. In a recording method for recording data by irradiating an optical disc with a laser beam,
Irradiating the optical disk with a laser beam, measuring the astigmatic difference of the laser beam from the reproduction signal from the optical disk,
Based on the astigmatic difference amount, set a recording strategy of the laser beam that irradiates the optical disc,
A recording method on an optical disk for recording data based on the recording strategy. In the recording method to the optical disk of Claim 6,
The method for recording on an optical disk, wherein the recording strategy includes a recording power and a recording pulse width of a laser beam. In the recording method to the optical disk of Claim 7,
When the astigmatic difference is small, the standard recording power and the recording pulse width are set.When the astigmatic difference is large, the recording power is set larger than the standard value and the recording pulse width is corrected to be short. A method for recording on an optical disc. In the setting method of the recording condition of the laser beam irradiated to the optical disc,
Obtain the astigmatic difference of the laser beam by reproducing the signal from the area where the signal is already recorded on the optical disc,
A recording condition setting method, wherein a recording power and a recording pulse width of a laser beam are set according to the astigmatic difference amount. In the recording condition setting method according to claim 9,
If the astigmatic difference is small, set the recording power of the laser beam small and the recording pulse width long,
When the astigmatic difference is large, the recording condition setting method is characterized in that the recording power of the laser beam is increased and the recording pulse width is shortened.

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