JP2007149238A - Optical disk device and information recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for obtaining good recording quality even when the temperature is changed in an optical disk device. <P>SOLUTION: The temperature of a laser diode or its vicinity is monitored during recording, when the temperature exceeds the reference value and changed, recording operation is stopped temporarily, measurement of a β value of a recording mark, operation of a correction rate of recording power of a high power level side of recording strategy based on the measured β value and a target β value, recording power correction of the high power level side of the recording strategy by the calculated correction rate are performed, and recording operation is restarted by the corrected recording power. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information recording technique in an optical disc apparatus, and more particularly to a technique for correcting a recording strategy when the temperature in the apparatus changes.

  In relation to the present invention, as conventional techniques for controlling the recording power of laser light applied to a recording medium such as an optical disk, Japanese Patent Application Laid-Open No. 2005-92950 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2005-228410 (Patent Document) There are those described in Reference 2). Japanese Patent Laid-Open No. 2005-92950 discloses that the rotation speed of an optical disk is changed from the inner peripheral side to the outer peripheral side in order to enable proper pit formation and suppression of reading errors even when the optical disk is warped. When recording information by increasing it stepwise, when switching the rotational speed of the optical disc, the recording operation is temporarily stopped, the β value at this point is measured, and the measured β value and the target β value are obtained. In comparison, a technique is described in which the β value is corrected, and the recording power of the laser beam is adjusted in accordance with the correction of the β value, and Japanese Patent Application Laid-Open No. 2005-228410 records the information on an information recording medium. In order to improve the reproduction quality of data, trial data recording is performed by changing the pulse ratio Po / Pm of the top pulse Po and middle pulse Pm as recording drive pulses, and the result of the trial data recording is A technique is described in which the optimum ratio of the pulse ratio Po / Pm is detected based on the correlation information between the reproduction quality and the pulse ratio Po / Pm.

JP 2005-92950 A JP 2005-228410 A

  In recent years, in optical disk devices, for the purpose of high-speed recording, high-density recording, etc., in addition to an increase in recording current, introduction of a laser diode for blue laser emission has been promoted. When the recording current is increased or when a laser diode for blue laser light emission is used, the temperature of the laser diode rises, and as a result, the light emission characteristic (IL characteristic) of the laser diode changes and is emitted. The recording power of the laser beam is reduced. A decrease in recording power decreases the recording quality of information and the reproduction quality thereof. For this reason, a technique for correcting the recording power by correcting the recording strategy corresponding to the temperature change of the laser diode is required.

  Among the techniques described in the above publications, the technique described in Japanese Patent Application Laid-Open No. 2005-92950 is a technique for enabling proper pit formation and reading errors to be suppressed even when the optical disk has a defect such as a warp. Since the recording power is adjusted by correcting the β value from the measured β value and the target β value, the recording power on the low power level side changes with the recording power on the high power level side of the recording strategy. For this reason, a problem remains as a technique for correcting only the recording power on the high power level side, for example, corresponding to the change in the light emission characteristics of the laser diode. In the technique described in the publication, the recording power is adjusted when the rotational speed of the optical disk is switched, and is not a technique for correcting the recording power during a recording operation in which the rotational speed of the optical disk is constant. Further, the technology described in Japanese Patent Laid-Open No. 2005-228410 performs test data recording by changing the pulse ratio Po / Pm between the top pulse Po and the middle pulse Pm, evaluates the reproduction quality obtained from the test data recording, and Since the correlation with the pulse ratio Po / Pm is obtained and the optimum pulse ratio Po / Pm is determined based on the correlation, it takes a long time to obtain the optimum pulse ratio Po / Pm. For this reason, a problem remains as a technique for correcting the recording power in a short time during the recording operation in response to a temperature change or the like.

In view of the above-described prior art, the problem of the present invention is that, in the optical disc apparatus, even during the recording operation, mainly in response to the change in the light emission characteristics of the laser diode due to the change in the apparatus temperature, The recording power can be corrected in a short time.
An object of the present invention is to solve the above-described problems, and to provide a technique capable of improving the reliability and usability of an optical disc apparatus so that good recording quality can be obtained even when the temperature changes.

  In order to solve the above problems, in the present invention, as an optical disc apparatus, the temperature of a laser diode or its vicinity is monitored during recording, and when the temperature changes exceeding a reference value, the recording operation is suspended. , Measurement of the β value of the recording mark, calculation of the recording power correction rate on the high power level side of the recording strategy based on the measured β value and the target β value, and high recording strategy based on the calculated correction rate The recording power on the power level side is corrected, and the recording operation is resumed after the correction.

  According to the present invention, in an optical disk apparatus, good recording quality can be obtained even when the apparatus temperature changes during recording, and reliability and usability can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1-6 is explanatory drawing of embodiment of this invention. FIG. 1 is a structural example diagram of an optical disc apparatus as an embodiment of the present invention, and FIG. 2 is a diagram showing a state of change in β value during OPC (Optimum Power Control) before recording operation and subsequent recording in the optical disc apparatus of FIG. FIG. 3 is a diagram illustrating a change in the light emission characteristics (hereinafter referred to as IL characteristics) of the laser diode when the apparatus temperature changes in the optical disk apparatus of FIG. 1, and a change in the recording power of the corresponding recording strategy (write strategy). FIG. 4 is an explanatory diagram of the recording power correction state of the recording strategy (write strategy) in the optical disk apparatus of FIG. 1, and FIG. 5 is a diagram for explaining the characteristic points of the recording power correction state shown in FIG. FIG. 6 is an explanatory diagram of the operation of the optical disk apparatus of FIG.

  In FIG. 1, 1 is an optical disc apparatus as an embodiment of the present invention, 2 is an optical disc such as a DVD or a blue laser disc, 3 is a disc motor that rotationally drives the optical disc 2, 4 is an optical pickup, The objective lens 6 is a laser diode that generates laser light of a predetermined intensity for recording or reproduction, 7 is a laser drive circuit that drives the laser diode 6, and 8 is recording on the optical disc 2 via the objective lens 5. A light receiving unit 9 that receives reflected laser light from a surface (hereinafter also referred to as an optical disc surface), converts it into an electrical signal, and outputs it. An analog front end for performing analog processing such as amplifying a signal from the light receiving unit 8 Is a temperature sensor as temperature detecting means for detecting the temperature of the laser diode 6 in the optical pickup 4 or the vicinity thereof, and 11 is a straight line , A moving / guide mechanism unit for moving the optical pickup 4 in a substantially radial direction of the optical disk 2, and a moving / guide mechanism unit 11. A slide motor for rotating a lead screw member (not shown), 15 is a motor drive circuit for driving the disk motor 3 and the slide motor 12, 30 is a DSP (Digital Signal Processor), and 31 is in the DSP 30. A motor control unit 32 for controlling the motor drive circuit 15, a recording signal generation unit 32 for generating a recording signal, and 33, a reproduction signal from the light receiving unit 8 in the DSP 30, an RF signal and a tracking error signal The reproduction signal processing unit 34 for processing as a focus error signal is provided in the DSP 30. The β measuring unit 35 serving as β measuring means for measuring the β value of the recording mark recorded on the optical disc from the reproduction signal, the target β value preset in the laser driving circuit 7, and the above A difference from the β value measured by the β measurement unit 34 is obtained, and a recording power correction factor on the high power level side of the recording strategy is calculated according to the difference, and a signal of the calculation result is output to the laser drive circuit 7 side. A recording power correction rate calculation unit as a recording power correction rate calculation unit to perform, 36 is a memory in the DSP 30, and 40 is a microcomputer as a control unit for controlling the DSP 30.

The microcomputer 40 controls at least the motor control unit 31, the β measurement unit 34, and the recording power correction factor calculation unit 33 in the DSP 30. The microcomputer 40 causes the optical disc apparatus 1 to perform normal OPC processing before the optical disc apparatus 1 starts the recording operation, and sets a target β value and correspondingly applies a laser to the recording surface of the optical disc 2. The optimum recording power of light (the recording power in the optimum range and the recording power in the range sufficient to effectively constitute the present invention) is set. The microcomputer 40 also causes the optical disc apparatus 1 to perform an OPC process corresponding to a change in apparatus temperature during the subsequent recording operation. In the OPC process during the recording, the emission power of the laser diode 6 corresponding to the recording power on the high power level side of the recording strategy is controlled in response to the change of the IL characteristic of the laser diode 6 due to the change of the apparatus temperature. To do. That is, when the temperature of the laser diode 6 or the vicinity thereof changes beyond the reference value, the microcomputer 40 controls the motor control unit 31 based on the output of the temperature sensor 10 and rotates the slide motor 12 by the motor drive circuit 15. The recording operation of the optical disc apparatus 1 is temporarily stopped to cause the β measurement unit 34 to measure the β value of the recording mark, and based on the measurement result, the recording power correction factor calculation unit 35 is caused to have a high power level of the recording strategy. The recording power correction factor on the side is calculated, and the recording power on the high power level side of the recording strategy is corrected based on the calculated correction factor. The recording power correction factor calculation unit 35 does not correct the recording power on the low power level side of the recording strategy. After the recording power correction factor calculation unit 35 corrects the recording power, the microcomputer 40 controls the motor control unit 31 to restart the disk motor 3 and the slide motor 12 so that the optical disk apparatus can operate with the corrected recording power. 1 to resume the recording operation.
In the following description, the same reference numerals as those in FIG. 1 are used for the components of the optical disc apparatus 1 in FIG. 1 used in the description.

FIG. 2 is an explanatory diagram of the OPC performed before the recording operation and the change state of the β value during recording in the optical disc apparatus 1 of FIG. (A) is an explanatory diagram of OPC performed before the recording operation, and (b) shows a change in β value corresponding to a change in apparatus temperature and a change in β value due to recording strategy correction in OPC during recording. FIG.
2A, the horizontal axis indicates the input power (hereinafter referred to as recording power) input to the recording surface of the optical disc 2 by OPC before the recording operation of the optical disc apparatus 1, and the vertical axis indicates the recording surface of the optical disc 2. This is the β value of the recording mark. In the OPC before the recording operation of the optical disc apparatus 1, the recording surface of the optical disc 2 is irradiated with a laser beam whose recording power is changed, and the β value of the recording mark corresponding to each recording power is calculated from the reproduction signal by the reflected laser beam. Measure and obtain characteristic curve Q. Thereafter, βt, which is the target β value, is set, and based on the characteristic curve Q, the optimum recording power (optimum recording power) Po of the laser beam corresponding to the target β value is set. The optimum recording power (optimal recording power) Po is an optimum range of recording power and is a range of recording power sufficient to effectively constitute the present invention.

In FIG. 2B, the horizontal axis represents the disk radius position of the optical disk 2, and the vertical axis represents the β value of the recording mark on the recording surface of the optical disk 2. r ₁ is a disk radial position where the optical disk apparatus 1 starts a recording operation, r ₂ is a disk radial position where the temperature change of the laser diode 6 or its vicinity exceeds a reference value, and βe is a disk radial position r ₂ The β value measured by the β measuring unit 34. In disc radial position r _1, it is performed OPC before recording operation of the optical disk apparatus 1, and βt is the β value of the target, and the optimum recording power Po of the laser beam is set. Thereafter, the recording operation is started, moving and guiding mechanism 11 which is driven by the slide motor 12, recording is performed while moving the optical pickup 4 in the direction of the disc radial position r _2. At this time, the temperature of the laser diode 6 or the vicinity thereof increases with the elapse of time by the light emitting operation of the laser diode 6. Further, the temperature of the laser diode 6 or the vicinity thereof also rises due to a temperature rise inside and outside the apparatus. As the temperature of the laser diode 6 increases, the IL characteristic of the laser diode 6 itself changes, and the power (recording power) of the laser light emitted from the laser diode 6 decreases. As the recording power decreases, the β value of the recording mark on the recording surface of the optical disc 2 also decreases. If a change in temperature of the laser diode 6 or the vicinity thereof exceeds a reference value when the objective lens 5 of the optical pickup 4 has reached the disc radial position r _2, the microcomputer 40, via the motor controller 31 and the motor driving circuit 15 Then, with the rotation of the slide motor 12 suspended and the recording operation of the optical disc apparatus 1 suspended, the β measuring unit 34 measures βe as the β value at that time, and βe and βt are calculated. The optical disk apparatus 1 is made to perform the used OPC process. Disc radial position r ₂ may form a recording portion terminating the recording operation is paused. In the OPC process at the disk radius position r ₂ , the recording power correction rate calculation unit 35 calculates the correction rate of the recording power on the high power level side of the recording strategy based on the difference between βt and βe, and the calculated correction The recording power on the high power level side of the recording strategy is corrected by the rate. When the conversion coefficient between the β value and the recording strategy recording power is k, and the recording power on the high power level side is Po, the recording power correction factor calculator 35 calculates the high power level after correcting the recording strategy. The recording power on the side is calculated as {1 + k (βt−βe)} Po. The conversion coefficient k is, for example, about 0.5. By correcting the recording power, the β value returns from the βe level to the βt level. The microcomputer 40 activates the slide motor 12 again, and causes the optical disc apparatus 1 to resume the recording operation with the corrected recording power.

  FIG. 3 is an explanatory diagram of a change in the IL characteristic of the laser diode 6 when the temperature changes in the optical disc apparatus 1 of FIG. 1 and a change in the recording power of the corresponding recording strategy. (A) shows the IL characteristics ((A)) and the recording strategy recording power ((B)) in the initial state before the apparatus temperature changes, and (b) shows when the apparatus temperature changes. The IL characteristics ((A)) and the recording power of the recording strategy ((B)) are shown.

In FIG. 3A, A is an IL characteristic curve of the laser diode 6 in the initial state, and Im is an energization current of the laser diode 6 corresponding to the recording power Pm on the low power level side of the recording strategy (hereinafter referred to as “low”). Io is a current applied to the laser diode 6 corresponding to the recording power (optimum recording power) Po on the high power level side of the recording strategy (hereinafter referred to as a high power corresponding current). In FIG. 3B, B is an IL characteristic curve when the apparatus temperature is changed, and Po ₁ is a high power level of the recording strategy corresponding to the high power corresponding current Io when the apparatus temperature is changed. Side recording power.

As apparent from FIGS. 3A and 3B, when the IL characteristic curve of the laser diode 6 changes from A to B due to the change in the apparatus temperature, the recording strategy is at the position of the low power corresponding current Im. The recording power Pm on the low power level side hardly changes, but at the position of the high power corresponding current Io, the recording power on the high power level side of the recording strategy decreases from the optimum recording power Po to the recording power Po ₁ . For this reason, it is necessary to correct the recording power Po ₁ to return to the optimum recording power Po.

FIG. 4 is an explanatory diagram of the recording power correction state of the recording strategy when the apparatus temperature changes in the optical disc apparatus 1 of FIG. (A) shows the correction state of the recording power in the IL characteristic of the laser diode 6, and (b) shows the correction state of the recording power of the recording strategy.
In FIG. 4A, Io ₁ indicates the energization of the laser diode 6 necessary to obtain the optimum recording power Po on the high power level side of the recording strategy on the IL characteristic curve B when the apparatus temperature changes. The current ΔIo is the current of the laser diode 6 when the optimum recording power Po on the high power level side of the recording strategy is obtained on the current Io ₁ and the IL characteristic curve A before the apparatus temperature changes. This is the difference from the energization current Io. Other symbols are the same as those in FIG.
As is apparent from FIGS. 4A and 4B, when the apparatus temperature changes, the energizing current Io of the laser diode 6 is increased by ΔIo to obtain the energizing current Io ₁ , thereby recording power Po. It is possible to correct ₁ and return to the optimum recording power Po. In the optical disc apparatus 1, the increase in the energization current I is based on the correction factor of the recording power on the high power level side of the recording strategy calculated by the recording power correction factor calculator 35 based on the difference between βt and βe. This is done by driving the laser diode 6 by the drive circuit 7.

FIG. 5 is a diagram for explaining the characteristic points of the recording power correction state shown in FIG. (A) is an energization current for both the recording power on the high power level side and the recording power on the low power level side of the recording strategy on the IL characteristic curve B of the laser diode 6 when the apparatus temperature changes. The state when the correction by the increase is performed is shown, and (b) shows the correction state of the recording power in the recording strategy at that time.
In FIG. 5A, Im ₁ is used to obtain a recording power correction on the high power level side of the recording strategy, that is, an optimum recording power Po on the IL characteristic curve B when the apparatus temperature changes. The energization current corresponding to the recording power on the low power level side, ΔIm, increased in association with the correction to increase the energization current Io of the laser diode 6 to Io ₁ is the energization current Im ₁ and the apparatus temperature. The difference between the current Im of the laser diode 6 when the recording power Pm on the low power level side of the recording strategy is obtained on the IL characteristic curve A before the change of Pm ₁ , Pm ₁ is the IL characteristic curve The recording power corresponding to the energization current Im ₁ on B is shown in FIG. Other reference numerals are the same as those in FIGS. 3 and 4.
If the device temperature changes, FIG. 5 (a), the as is clear from (b), at the same time as the supply current Io of the laser diode 6 △ and Io increases the energizing current Io _1, the electric current Im △ If Im is increased to an energization current Im ₁ , the recording power Po ₁ is corrected and returned to the optimum recording power Po on the high power level side of the recording strategy, but on the low power level side, the optimum on the high power level side The recording power Pm suitable for the recording power Po is changed to Pm ₁ having a value close to the optimum recording power Po. Changing the recording power on the low power level side of the recording strategy from Pm to Pm ₁ leads to a decrease in recording quality.

FIG. 6 is an explanatory diagram of the OPC processing operation during the recording operation of the optical disc apparatus 1 of FIG.
In FIG.
(1) During the recording operation of the optical disc apparatus 1, when the temperature of the laser diode 6 detected by the temperature sensor 10 or in the vicinity thereof changes beyond the reference value, the microcomputer 40 triggers the recording power of the recording strategy. The correction operation is started (step S601).
(2) The microcomputer 40 controls the motor control unit 31 based on the output of the temperature sensor 10 and temporarily stops the rotation of the slide motor 12 by the motor driving circuit 15 to temporarily stop the recording operation of the optical disc device 1 (step). S602).
(3) Thereafter, the β measuring unit 34 measures the β value of the recording mark (step S603).
(4) Further, based on the measurement result of the β value, the recording power correction factor calculator 35 calculates the correction factor of the recording power on the high power level side of the recording strategy (step S604).
(5) The recording power correction rate calculation unit 35 corrects the recording power on the high power level side of the recording strategy by the correction rate obtained in step S604 (step S605). The recording power on the low power level side of the recording strategy is not corrected.
(6) After the recording power correction factor calculation unit 35 corrects the recording power, the optical disc apparatus 1 restarts the rotation of the slide motor 12, and restarts the recording operation with the corrected recording power (step S606). This correction is finished (step S607).
The series of steps from step S601 to step S607 are automatically executed by the microcomputer 40 according to a program stored in a storage unit such as the memory 36 in the optical disc apparatus 1.

  According to the optical disc apparatus 1 of the above embodiment, even when the apparatus temperature changes during recording, the recording power of the recording strategy can be corrected. Further, since the correction of the recording power is a correction corresponding to the change of the IL characteristic of the laser diode 6, it is possible to improve the correction accuracy and shorten the correction processing time. As a result, good recording quality can be obtained even when the apparatus temperature changes during recording, and the reliability and usability of the apparatus can be improved.

  In the above-described embodiment, the case where the recording power on the high power level side is corrected in response to the temperature change has been described. However, the technique of the present invention can also be applied to, for example, a zone having a plurality of zones. At the time of switching, it is also possible to measure the β value at the end of the zone, triggered by the zone switching, and to correct the recording power on the high power level side of the next zone based on the measurement result.

1 is a configuration example diagram of an optical disc apparatus as an embodiment of the present invention. FIG. 2 is an explanatory diagram of OPC and β value change in the optical disc apparatus of FIG. 1. FIG. 2 is an explanatory diagram of a change in light emission characteristics and a change in recording power when the temperature changes in the optical disc apparatus of FIG. 1. It is explanatory drawing of the correction state of the recording power in the optical disk apparatus of FIG. FIG. 5 is a diagram for explaining a feature point of correction of recording power shown in FIG. 4. FIG. 2 is an operation explanatory diagram of the optical disc apparatus of FIG. 1.

Explanation of symbols

1 ... Optical disk device,
2 ... Optical disc,
3 ... Disc motor,
4 ... Optical pickup,
5 ... Objective lens,
6 ... Laser diode,
7 ... Laser drive circuit,
8: Light receiving part,
9 ... Analog front end,
10 ... temperature sensor,
11 ... movement / guide mechanism,
12 ... Slide motor,
15 ... Motor drive circuit,
30 ... DSP,
31 ... Motor control unit,
32. Recording signal generator,
33. Reproduction signal processing unit,
34 ... β measuring section,
35. Recording power correction factor calculation unit,
36 ... Memory,
40: Microcomputer.

Claims (7)

An optical disc apparatus that records or reproduces information by irradiating an optical disc with a laser beam,
A disk motor for rotating the optical disk;
A motor drive circuit for driving the disk motor;
A laser diode that emits the laser light;
A laser driving circuit for driving the laser diode;
Temperature detecting means for detecting the temperature of the laser diode or the vicinity thereof;
Β measuring means for measuring a β value of a recording mark recorded on the optical disc from a reproduction signal based on a reflected laser beam from the optical disc;
A difference between a preset target β value and the measured β value is obtained, a recording power correction factor on the high power level side of the recording strategy is calculated according to the difference, and the signal of the calculation result is calculated as described above. A recording power correction factor calculating means for outputting to the laser drive circuit side;
Control means for controlling the motor drive circuit, the β measuring means and the recording power correction factor calculating means;
When the temperature of the laser diode or the vicinity thereof exceeds a reference value, the recording operation is temporarily stopped based on the output of the temperature detecting means, and the β value of the recording mark is measured by the β measuring means, A configuration for calculating a recording power correction rate on the high power level side of the recording strategy based on the measurement result, and correcting the recording power on the high power level side of the recording strategy based on the calculated correction rate. An optical disc apparatus characterized by the above.   The recording power correction factor calculating means is characterized in that the measured β value is βe, the target β value is βt, a conversion coefficient between the recording power and β value of the recording strategy is k, and the high power level of the recording strategy is 2. The optical disc apparatus according to claim 1, wherein the recording power on the high power level side is calculated as {1 + k (βt−βe)} Po when the recording power on the side is Po.   3. The optical disk apparatus according to claim 2, wherein the recording power correction factor calculation means calculates a recording power correction factor on the high power level side of the recording strategy with the conversion coefficient k being about 0.5.   4. The optical disc apparatus according to claim 1, wherein the recording power correction rate calculating means is configured not to correct the recording power on the low power level side of the recording strategy. An information recording method for recording information by irradiating an optical disk with laser light from a laser diode,
A first step of temporarily stopping the recording operation when the temperature of the laser diode or the vicinity thereof exceeds a reference value;
A second step of measuring a β value of a recording mark recorded on the optical disc from a reproduction signal based on a reflected laser beam from the optical disc;
A third step of obtaining a difference between the measured β value and a preset target β value, and calculating a recording power correction factor on the high power level side of the recording strategy according to the difference;
A fourth step of correcting the recording power on the high power level side of the recording strategy based on the calculation result;
A fifth step of resuming recording of information with the corrected recording power recording strategy;
An information recording method comprising recording information through   In the third step, the measured β value is βe, the target β value is βt, the conversion coefficient between the β value and the recording power of the recording strategy is k, and the high power level side of the recording strategy is 6. The information recording method according to claim 5, wherein when the recording power is Po, the corrected recording power on the high power level side is calculated as {1 + k (βt−βe)} Po. An optical disc apparatus that records or reproduces information by irradiating an optical disc with a laser beam,
A laser diode that emits the laser light;
Temperature detecting means for detecting the temperature in the vicinity of the laser diode;
Β measuring means for measuring a β value of a recording mark recorded on the optical disc from a reproduction signal based on a reflected laser beam from the optical disc;
A recording power correction means for calculating a difference between a preset target β value and the measured β value and correcting the recording power according to the difference;
Control means for controlling the β measurement means and the recording power correction means;
An optical disc apparatus comprising: a control unit configured to temporarily stop a recording operation and to correct a recording power by the recording power correction unit when a temperature near the laser diode changes by a predetermined value or more.

Images