JP2004110995A - Disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk drive capable of setting optimum recording power to various disks. <P>SOLUTION: This disk drive 10 includes a disk 22, and when a signal is recorded, a laser diode 20 is driven by two-stage recording power Ph and Pm. For example, a recording mark following a test pattern 1 and a recording mark following a test pattern 2 are recorded in a prescribed area of the disk 22. Then, the two recording marks are reproduced and a modulation factor of each reproduced signal is detected. When the modulation factors are equal to each other, a fixed modulation factor is judged to be always obtained without depending upon laser power, and the laser power at that time is determined as optimum power. Meanwhile, unless the modulation factors are equal, the second laser power is detected and optimum laser power is determined from a modulation factor obtained by recording and reproducing the test patterns 1 and 2 and the above modulation factor. Optimum laser power can be set to each disk regardless of a light strategy. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a disk drive, and more particularly to, for example, a disk drive that drives a laser diode with first and second laser powers and records a signal on a disk by laser light emitted from an optical pickup.
[0002]
[Prior art]
An example of a conventional disk device of this type is disclosed in Japanese Patent Application Laid-Open No. H11-163,837. In this conventional recording / reproducing apparatus, jitter is measured based on an RF signal, and a recording power at which the jitter is minimized is determined as an optimum recording power value.
[0003]
[Patent Document 1]
JP-A-2000-137918 (pages 4, 5 and FIG. 4)
[0004]
[Problems to be solved by the invention]
In these prior arts, it is necessary to separately provide a circuit for measuring jitter, which has led to an increase in the cost of the apparatus. In such a case, it is possible to obtain the optimum recording power from the write strategy pre-recorded on the disc, but this write strategy has an optical system and a laser wavelength defined in the standard. This is the optimum recording condition when recording with an optical pickup device, and the drive device (optical pickup device) that is actually commercially available is different from the optical system and the like defined in the standard. Not always.
[0005]
In addition, usually, the manufacturer (maker) obtains the optimum write strategy of the disc of each company by experiment before commercializing the drive device, and records the optimum recording conditions in the drive device. After the drive device was sold, the optimum recording conditions were not stored for the sold disk, and the write strategy for the past disk of the same maker was used. Also, for a new product disk, it was necessary to obtain the recording conditions from the write strategy recorded on the disk. For this reason, the deterioration of the recording characteristics was inevitable.
[0006]
Therefore, a main object of the present invention is to provide a disk device capable of setting an optimum recording power for various disks.
[0007]
[Means for Solving the Problems]
According to the present invention, in a disc reproducing apparatus for driving a laser diode with first and second laser powers and recording a signal on a disc by laser light emitted from an optical pickup, the laser diode is driven by a first predetermined laser power and a first predetermined laser power. (2) a first mark recording means for driving at a predetermined laser power to record a first recording mark according to a first pattern and a second recording mark according to a second pattern different from the first pattern in a predetermined area of the disk; First mark reproducing means for reproducing the first recording mark and the second recording mark recorded by the means, and detecting a first modulation degree of a first reproduction signal corresponding to the first recording mark reproduced by the first mark reproducing means. First detecting means for detecting the second modulation degree of the second reproduced signal corresponding to the second recording mark; First determining means for determining whether the degree of modulation is equal to the second degree of modulation, and when the first degree of modulation determines that the first degree of modulation and the second degree of modulation are equal, the first predetermined laser power and the second predetermined degree of modulation are determined. 2 This is a disk device that determines a predetermined laser power as an optimum laser power.
[0008]
[Action]
A disk such as a DVD-R / RW is mounted on the disk device. For example, when recording a signal, a laser diode is driven by the first and second laser powers. That is, the laser diode is driven with two levels of power. For example, prior to recording of the signal, the mark recording means sets the laser diode to a first recording mark according to the first pattern and a second recording mark according to the second pattern with a first predetermined laser power and a second predetermined laser power. Record at different positions (addresses) in the area. The mark reproducing means reproduces the first recording mark and the second recording mark recorded by the mark recording means, respectively, and obtains the first modulation degree of the first reproduction signal and the second modulation degree of the second reproduction signal obtained as a result of the reproduction. The degree of modulation is detected. The detected first modulation degree and second modulation degree are discriminated by the first discriminating means as to whether they are equal or substantially equal to each other. As a result of the determination, when they are equal to each other, it is determined that a constant modulation degree is always obtained without depending on the laser power, and the first predetermined laser power and the second predetermined laser power are respectively equal to the first laser power and the second laser power. The optimum laser power of laser power 2 is determined.
[0009]
However, if the first modulation degree and the second modulation degree are not equal, the second predetermined laser power is corrected, and the first recording mark and the second recording mark according to the first pattern are corrected by the first predetermined laser power and the corrected laser power. A second recording mark according to the pattern is recorded in a predetermined area of the disc. That is, the modulation degree (the third modulation degree and the fourth modulation degree) of the first pattern and the second pattern is detected by changing the second laser power as described above. Then, the optimum power is determined based on the first to fourth modulation degrees.
[0010]
Specifically, the first modulation degree and the second modulation degree obtained first, and the third modulation degree and the second modulation degree obtained when the first predetermined laser power is fixed and the second predetermined laser power is used as the correction laser power. The four degrees of modulation are plotted on two-dimensional coordinates, the first degree of modulation and the third degree of modulation obtained for the first pattern are connected by a straight line, and the second degree of modulation and the fourth degree of modulation obtained for the second pattern are connected. With a straight line. Then, the intersection of the two straight lines is determined to be in a state where a constant degree of modulation is obtained, and the laser power at that time is determined as the optimum power of the second laser power. As described above, by determining the optimum second laser power when the first laser power is fixed, the optimum ratio between the first laser power and the second laser power can be obtained. Thereafter, an OPC (Optimum Power Control) process is performed, and when the optimum first laser power is determined, the second laser power can be set to an optimum value in accordance with the ratio obtained previously.
[0011]
Further, the first pattern and the second pattern include a first mark recorded with only a first predetermined laser power and a first space having the same length as the first mark length of the first mark. A second mark longer than the first mark length recorded with the laser power and the second predetermined laser power and a second space having the same length as the second mark length of the second mark are included. However, in the first pattern and the second pattern, the first mark, the first space, the second mark, and the second space have the same appearance frequency (number), but are arranged in a different order.
[0012]
For example, in the first pattern, the second marks are arranged immediately before the first space, and in the second pattern, the first marks are arranged immediately before the first space.
[0013]
In the embodiment, the first pattern (inspection pattern 1) is arranged as “11M-3S-4M-4S-3M-11S”, and the second pattern (inspection pattern 2) is arranged as “11M-4S”. -3M-3S-4M-11S ". Here, M is a mark, and S is a space. Also, the first mark is 3M, the first space is 3S, the second mark is 11M, and the second space is 11S.
[0014]
In this way, by preparing patterns having different arrangements, it is possible to always find a constant modulation degree based on a reproduction signal (reproduction waveform) without depending on the laser power.
[0015]
【The invention's effect】
According to the present invention, the recording power is determined to be the optimum power in a state where a constant modulation degree is always obtained without depending on the recording power. Therefore, the optimum recording power is set for various disks regardless of the write strategy. can do.
[0016]
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.
[0017]
【Example】
Referring to FIG. 1, a disk device 10 of this embodiment includes an optical pickup 12, and the optical pickup 12 is provided with an objective lens. This objective lens 14 is supported by a tracking actuator 16 and a focus actuator 18. The laser light emitted from the laser diode 20 is applied to the recording surface of a disk 22 such as a DVD-R or DVD-RW via an optical system (not shown) and the objective lens 14.
[0018]
The disk 22 is mounted (chucking) on a turntable 24 and rotated by a spindle motor 26. For example, the disk 22 can rotate in a CLV (Constant Linear Velocity) system, and the number of rotations decreases as the optical pickup 12 moves from the inner circumference to the outer circumference.
[0019]
As shown in FIG. 2, on the recording surface of the disk 22, convex land tracks and concave groove tracks are formed alternately for each track, and land tracks between adjacent groove tracks have a predetermined period (a predetermined interval). ) To form land pre-pits (LPP).
[0020]
Referring to FIGS. 3A and 3B, the laser beam irradiated on the recording surface of disk 22 is composed of one main beam M and two sub beams S1 and S2. Of these, the main beam M is applied to a desired track (groove track), and the sub-beams S1 and S2 are applied to tracks adjacent to both sides of the desired track (land track).
[0021]
The laser light reflected on the recording surface of the disk 22 is irradiated on the photodetector 28 via the objective lens 14 and the optical system. The main beam M is detected by the light detecting elements 28a to 28d, the sub beam S1 is detected by the light detecting elements 28e and 28f, and the sub beam S2 is detected by the light detecting elements 28g and 28h.
[0022]
The main beam M, the sub beam S1, and the sub beam S2 detected by the photodetectors 28a to 28h are respectively converted into currents and output to the matrix amplifier 30. The matrix amplifier 30 subjects the outputs of the photodetectors 28 (the photodetectors 28a to 28h) to well-known arithmetic processing as shown in Expressions 1 to 4, and performs a tracking error (TE) signal and a focus error (FE). A signal, a wobble signal, and an RF signal are detected, respectively. However, the TE signal is detected by a differential push-pull (DPP) method, and the wobble signal is detected by a push-pull (PP) method.
[0023]
(Equation 1)
TE = {(A + B) − (C + D)} − α {(E + H) − (F + G)}
[0024]
(Equation 2)
FE = (A + C)-(B + D)
[0025]
[Equation 3]
Wobble = (A + B)-(C + D)
[0026]
(Equation 4)
RF = A + B + C + D
Note that “A” to “H” in Equations 1 to 4 correspond to the outputs of the photodetectors 22a to 22h, respectively.
[0027]
Returning to FIG. 1, the TE signal, the FE signal, and the wobble signal detected by the matrix amplifier 30 are respectively supplied to the DSP 32 via an A / D converter (not shown). The DSP 32 executes tracking servo and sled servo based on the digitally converted TE signal, and generates a tracking actuator control signal and a sled motor control signal. The generated tracking actuator control signal and sled motor control signal are converted into a tracking actuator control voltage and a sled control voltage by the driver 34b and the driver 34c, respectively, and supplied to the tracking actuator 16 and the sled motor 36, respectively. Thus, the position of the optical lens 14 in the radial direction (sled direction), the rotational speed and the rotational direction of the sled motor 36 are controlled. However, since the thread motor 36 is connected to the optical pickup 12 by a rack and pinion method or the like, as is well known, the moving direction (moving speed) and position (displacement) of the optical pickup 12 are controlled by the thread servo.
[0028]
The DSP 32 executes focus servo based on the digitally converted FE signal, and generates a focus control signal. The generated focus control signal is converted into a focus control voltage by the driver 34 a and provided to the focus actuator 18. Thereby, the focus, that is, the position (lens position) on the optical axis of the objective lens 14 is adjusted. That is, the position in the focus direction is adjusted.
[0029]
Further, the DSP 32 executes a spindle servo (hereinafter, referred to as “CLV servo”) based on the digitally converted wobble signal, and generates a spindle control signal. The generated spindle control signal is converted into a spindle motor control voltage by the driver 34 d and supplied to the spindle motor 26. Thus, the rotation speed and the rotation direction of the spindle motor 26 (turntable 24), that is, the disk 22, are adjusted.
[0030]
However, at the beginning when the disk 22 is mounted on the disk device 10, the signal of the disk 22, that is, the wobble signal cannot be read accurately, so that the spindle servo by the FG pulse is executed. That is, the rotation speed of the spindle motor 26 is pulse-converted by an encoder (not shown), and the FG pulse generated thereby is given to the DSP 32. The DSP 32 detects the number of rotations of the spindle motor 26 based on the given FG pulse, and generates a spindle control signal so that the number of rotations reaches a desired value. The generated spindle control signal is converted into a spindle motor control voltage by the driver 34 d and supplied to the spindle motor 26.
[0031]
As described above, the spindle servo (FG servo) can be executed based on the FG pulse, but the rotation control is coarser than that of the CLV servo.
[0032]
The RF signal (reproduced signal) detected by the matrix amplifier 30 is provided to the encoder / decoder 38. The encoder / decoder 38 is an IC or the like in which an encode and a decoder are integrally formed. The encoder / decoder 38 decodes an RF signal in accordance with address information given from an address detection circuit (decoder) 42 under the instruction of the CPU 40, and sends the decoded signal to a host computer such as a PC (not shown) via an interface (I / F). Output.
[0033]
Although not shown, the decoder 42 detects a pre-pit signal included (superimposed) in a wobble signal obtained when the DVD-R or DVD-RW disc 22 is reproduced, and detects based on the pre-pit signal. The obtained address information and the timing information at the time of recording are provided to the encoder / decoder 38.
[0034]
Further, the encoder / decoder 38 encodes a signal (recording signal) input from the host computer to generate a pit signal (recording pulse), and generates the pit signal (recording pulse) according to the address information and timing information from the decoder 42. Give to 44. The laser drive circuit 44 drives the laser diode 20 according to a recording pulse provided from the encoder / decoder 38 under the instruction of the CPU 40. Therefore, a recording signal given from the host computer is recorded at a desired position (address) on the recording surface of the disk 22.
[0035]
For example, in a disk 22 such as a DVD-R / DVD-RW, an EFM + modulation method is adopted, and modulation data of RLL (2, 10) is executed from a recording signal (recording data) to obtain modulation data. . The modulated data is further subjected to NRZI modulation to obtain NRZI code data. The NRZI code data includes pulses having pulse widths of 3T to 11T and 14T. Here, T is the reciprocal (about 38.2 nsec) of the channel clock (26.16 MHz in this embodiment) of the drive device (disk device 10).
[0036]
Although not shown in the drawings, the recording mark corresponding to 14T is formed only as a synchronization signal.
[0037]
For example, at the time of standard speed recording, modulated data as shown in FIG. 4A is NRZI-modulated, and NRZI code data as shown in FIG. 4B is obtained. The modulation data is digital data represented by "0" and "1", and is subjected to NRZI modulation (pulse conversion) to generate NRZI code data.
[0038]
As can be seen from FIG. 4B, in the NRZI code data, a low-level 3T period and a high-level 3T period are provided alternately after a low-level 11T period and a high-level 11T period.
[0039]
When an optimal laser power (optimal power) is set in accordance with the NRZI code data, a recording pulse (write pulse) as shown in FIG. 4C is generated. The write pulse includes a top pulse corresponding to a 3T period and a multi-pulse in a 4T period or longer. That is, in the high-level 3T period, only the top pulse is generated, but in the high-level 11T period, eight (corresponding to 8T) multipulses are generated following the top pulse. The peak value of such a write pulse is the laser power Po. As described above, since it is assumed that the optimum power is set, the laser power Po in the drawing is the optimum power.
[0040]
In the figure, Ttop indicates a top pulse width, and Tmp indicates a multi-pulse width. Hereinafter, the same applies to this embodiment.
[0041]
When a signal is recorded on the disk 22 according to such a write pulse, a mark (M) and a space (S) are formed on the disk 22 as shown in FIG. That is, following the space (S) corresponding to the 11T period and the mark (M) corresponding to the 11T period, the space corresponding to the 3T period and the mark corresponding to the 3T period are alternately formed.
[0042]
When such a recording mark or the like is reproduced, an ideal reproduction signal waveform (reproduction waveform) as shown in FIG. 4E is obtained. Furthermore, data obtained by binarizing the reproduced signal (reproduced binarized data) is shown in FIG. 4 (F).
[0043]
Here, paying attention to the multi-pulse included in the write pulse shown in FIG. 4C, the laser power is switched in a short time (short period) at the time of high-speed recording (for example, quadruple speed or octuple speed). There is a need. If the response characteristics of the laser diode 20 are poor, the laser power may not reach the above-described optimum power Po, which may have a great influence on the recording characteristics. Therefore, it is necessary to prepare an expensive laser diode 20 (optical pickup 12) having excellent response characteristics. Therefore, in this embodiment, a relatively inexpensive optical pickup 12 is used by adopting a non-multi-pulse system.
[0044]
Specifically, a write pulse as shown in FIG. 5C is generated. Note that the modulation data, NRZI code data, recording marks, reproduced waveform, and reproduced binarized data are the same as those shown in FIG. 4, and a detailed description thereof will be omitted.
[0045]
As shown in FIG. 5C, in the write pulse corresponding to the high-level 11T period of the NRZI code data, a pulse having a smaller peak value than the top pulse following the top pulse (hereinafter, for convenience of explanation, “non-pulse”). Multi-pulse ") is generated. That is, the top pulse corresponding to the 3T period and the non-multi-pulse corresponding to the 8T period are integrally (continuously) generated. That is, when forming a recording mark of 4T or more, the laser power is adjusted in two stages. Therefore, unlike the multi-pulse method, ON / OFF is not repeated in a short period, and a high response characteristic is not required for high-speed recording.
[0046]
As described above, when a recording mark of 4T or more is formed, the laser power of the write pulse is adjusted in two stages, but the laser power (the peak value of the top pulse) Ph and the laser power (the non-multi-pulse wave). When the ratio to (high value) Pm is optimum, optimum power is obtained. This means that, as shown in FIGS. 6A and 6B, the values of Ph / Pm are fixed at 1.43, 1.38, 1.30, and 1.26, respectively, and the recording power is reduced. It can be derived from the recording characteristics at the time of change. 6A is a graph showing the relationship between the laser power (recording power) Ph and the jitter, and FIG. 6B is a graph showing the relationship between the recording power Ph and the β value.
[0047]
As can be seen from FIG. 6 (A), when the value of Ph / Pm is changed, the recording power at which the bottom jitter is obtained also changes. Therefore, the signal is changed according to a plurality of combinations of conditions using the value of Ph / Pm and the recording power as parameters. It is necessary to record and derive the optimum Ph / Pm and the optimum power. From the experimental results, it can be seen that the optimum value of Ph / Pm is about 1.30 in the disk device (optical pickup device) used in the experiment.
[0048]
The optimum value of Ph / Pm when the disk used in this experiment was evaluated by a standard-compliant recording device was 1.49. Considering the results shown in FIG. It is assumed that the optimum power cannot be obtained with any recording power.
[0049]
Also, in FIG. 6B, it is assumed that when the value of Ph / Pm is 1.38, an OPC (Optimum Power Control) process is performed. In simple terms, the OPC process is a process for determining (determining) the recording power Ph at which a target β (hereinafter referred to as “target β”) is obtained as the optimum recording power. The value of the target β in the OPC process is usually near 0, and here, it is assumed that the target β is 0. Referring to FIG. 6B, when Ph / Pm is 1.38, β = 0 when the recording power is about 20.8 mW, which is determined to be the optimum power. Actually, when recording is performed under the recording conditions of Ph / Pm = 1.38 and Ph = 20.8 (mW), as shown in FIG. 6A, the reproduction jitter is about 12%, It can be seen that the recording condition is extremely poor, whereas the bottom jitter when Pm = 1.38 is about 7.6% (Ph = 19.4 mW). Thus, it can be said that the value of Ph / Pm is a very important value in the control system including the OPC process, and it is necessary to set the value of Ph / Pm to an optimum value.
[0050]
When the optimum power is set (determined) from the optimum value of Ph / Pm, as shown in FIG. 5D, the width of the pit is constant, and the appropriate pit length (pit length) is determined. Marks for the 11T period and the 3T period are formed on the disk 22. That is, ideal pits are formed.
[0051]
However, in such a disk 22, since the material and the like are different depending on the manufacturer (manufacturer), the optimum recording conditions (recording power and the like) are different. Therefore, it is standardized that an optimum write strategy is recorded on the disk 22 in advance. The write strategy includes information such as a top pulse width, a multi-pulse width, a target β value in an OPC process for deriving a write power and an optimum recording power, and the like. Therefore, when recording a signal, such a write strategy is usually read and the recording conditions are adjusted.
[0052]
However, such a write strategy is an optimal recording condition when recording is performed using an optical pickup device having an optical system and a laser wavelength defined in the standard, and a commercially available disk device is the same. Since it is different from the optical system and laser wavelength defined in the standard, it does not always satisfy the optimum recording condition.
[0053]
Therefore, prior to commercialization of the drive device, the drive device manufacturer acquires an optimum write strategy for each manufacturer's disk by experiment and stores it in the drive device. However, in the write strategy stored in the drive device, since the write power is determined based on information such as the width of the top pulse determined in advance, if the peak value Ph or the like of the top pulse is not appropriate, the OPC processing is performed. , The optimum power could not be set.
[0054]
That is, even when information such as the width of the top pulse is obtained from the write strategy recorded on the disk 22 or the disk device 10, as shown in FIGS. If the ratio of the pulse to the peak value Pm is not optimal, the shape of the pit is deformed, which adversely affects the reproduction quality.
[0055]
For example, as shown in FIG. 7 (C), when the peak value Pm of the non-multi-pulse is larger than the optimum value, the recording power after 4T is too large, and as shown in FIG. The shape is not formed linearly. That is, as compared with the ideal pit shape shown in FIG. 5D, the pit width gradually increases in time series and the pit length increases. For this reason, as shown in FIG. 7 (E), a shift occurs in the reproduced waveform, and therefore, as shown in FIG. 7 (F), a shift also occurs in the reproduced binary data.
[0056]
Further, as shown in FIG. 8C, when the peak value Pm of the non-multi-pulse is smaller than the optimum value, the recording power after 4T is too small, and as shown in FIG. As compared with the ideal pit shape shown in FIG. 5 (D), the pit width gradually becomes smaller and the pit length becomes shorter in time series. For this reason, as shown in FIG. 8E, a shift occurs in the reproduced waveform, and therefore, as shown in FIG. 8F, a shift also occurs in the reproduced binary data.
[0057]
As described above, even if a write pulse is generated based on Ph / Pm or the like according to a write storage previously recorded on the disk 22 or the like, the recording power is not always optimal. Therefore, in this embodiment, prior to the signal recording processing, the optimum power for the disk 22 is determined.
[0058]
In this example, for example, an inspection pattern 1 shown in FIG. 9A and an inspection pattern 2 shown in FIG. 9B were prepared in advance. As shown in FIG. 9A, the test pattern 1 is a pattern in which “11M-3S-4M-4S-3M-11S” is repeated, and corresponds to a 3T period because 11M is arranged immediately before 3S. It can be said that the amplitude Va3 is a pattern that is easily affected by the magnitude relationship of the recording power Pm (see FIGS. 5, 7, and 8). On the other hand, as shown in FIG. 9B, the test pattern 2 is a pattern in which “11M-4S-3M-3S-4M-11S” is repeated, and 3M is arranged immediately before 3S. Is a pattern that is not affected by the magnitude relationship of the recording power Pm (see FIGS. 5, 7, and 8).
[0059]
That is, the inspection pattern 1 and the inspection pattern 2 include the same type of mark (M) and space (S), that is, include 3M, 3S, 4M, 4S, 11M, and 11S, and their respective appearance frequencies. Although the (number) is the same, they are arranged differently from each other.
[0060]
For example, when the recording power Ph is fixed at 20 mW and the recording power Pm is changed between 14.3 mW and 16.1 mW, the I of pattern 1 and pattern 2 is changed. ₃ FIG. 10A shows the result of the measurement of the degree of modulation (experimental result). In FIGS. 10A and 10B, the measurement is performed when the recording power Pm is 14.3 mW, 14.9 mW, 15.6 mW, or 16.1 mW.
[0061]
Where I ₃ The modulation degree is the amplitude of the reproduced waveform corresponding to the 3T period with respect to the amplitude Va11 of the reproduced waveform corresponding to the 11T period detected from the envelope of the reproduced signal (RF signal) as shown in FIGS. It refers to the ratio of Va3 and is calculated according to Equation 5.
[0062]
(Equation 5)
I ₃ Modulation degree = Va3 / Va11
The envelope of the RF signal is detected by the encoder / decoder 38 shown in FIG. 1, and the amplitude Va11 and the amplitude Va3 are measured by the encoder / decoder 38 according to the instruction of the CPU 40. However, a separate IC for detecting such an envelope and measuring the amplitude Va11 and the amplitude Va3 may be provided.
[0063]
Returning to FIG. 10A, the inspection pattern 1 is strongly affected by the recording power Pm because 11M exists immediately before 3S as described above. Therefore, for example, when the recording power Pm is insufficient, the amplitude Va3 of the reproduced waveform corresponding to the 3T period increases, and I ₃ The degree of modulation also increases. On the other hand, in the inspection pattern 2, since the influence of the recording power Pm is small, I ₃ The change in the degree of modulation is also reduced.
[0064]
Here, the optimum recording power is the I ₃ Modulation Degree and I of Test Pattern 2 ₃ This is the power when the degree of modulation is equal or substantially equal. That is, a state in which a constant modulation degree is always obtained without depending on the recording power. In this embodiment, the laser power at the intersection of the straight line connecting the modulation degrees for the inspection pattern 1 and the straight line connecting the modulation degrees for the inspection pattern 2 is about 15.2 mW. This is determined to be the optimum recording power (optimum power) Pm. At this time, the value of Ph / Pm is 20 mW / 15.2 mW = 1.32.
[0065]
FIG. 10B shows the measurement results of the jitter and β when the recording power Ph is fixed at 20 mW and the Pm power is changed. The bottom jitter of the recording power Pm is between 15 mW and 15.5 mW. It can be seen that That is, it is appropriate to determine that the optimum power Pm is about 15.2 mW.
[0066]
Specifically, the CPU 40 shown in FIG. 1 executes a recording power determination process as shown in FIGS. As shown in FIG. 11, when the recording power determination process is started, the CPU 40 seeks a predetermined area (inspection area) of the disk 22, that is, a PCA (Power Calibration Area) in step S1. Since such a seek operation is already known, a detailed description thereof will be omitted in this embodiment.
[0067]
Next, in step S3, an initial value of the recording power is set. That is, the initial value Pm is added to the recording power Pm. ₀ And the initial value Ph for the recording power Ph ₀ Is assigned. Such an initial value Pm ₀ And Ph ₀ May be obtained from a write strategy recorded on the disk 22, or a developer or a designer may obtain it from an experiment and obtain it from a write storage stored in the disk device 10. However, in this embodiment, the initial value Pm is based on the experimental result described with reference to FIG. ₀ Is 14.3 mW, and the initial value Ph is ₀ Is about 20 mW.
[0068]
In a succeeding step S5, an inspection pattern 1 as shown in FIG. 9A is recorded. Specifically, modulation data as shown in FIG. 9A is provided from the CPU 40 to the encoder / decoder 38, and the modulation data is modulated into NRZI code data by the encoder / decoder 38. Subsequently, the encoder / decoder 38 generates a write pulse based on the NRZI code data. That is, although not shown, as described with reference to FIG. 5C, a write pulse whose write power is adjusted in two stages is generated for 4T or more. Then, the encoder / decoder 38 supplies a write pulse to the laser drive circuit 44 according to the address information and the timing information from the decoder 42. At this time, an instruction to drive the laser diode 20 is given from the CPU 40 to the laser drive circuit 44. Therefore, a mark or the like according to the inspection pattern 1 is recorded at a predetermined position (first predetermined address) in a predetermined area of the disk 22.
[0069]
Subsequently, in step S7, an inspection pattern 2 as shown in FIG. 9B is recorded. A mark or the like according to such an inspection pattern 2 is recorded at a second predetermined address in a predetermined area of the disk 22 as in the case of the inspection pattern 1 described above.
[0070]
Next, in step S9, a recorded mark or the like according to the recorded inspection pattern 1 is reproduced, and I ₃ Degree of modulation (I _3-01 ) Is measured. Specifically, as shown in FIGS. 5, 7, and 8, the amplitude Va11 of the reproduced waveform corresponding to the 11T period and the amplitude Va3 of the reproduced waveform corresponding to the 3T period are determined from the envelope of the reproduced signal (RF signal). And according to equation 5 above, I ₃ The degree of modulation is calculated (measured).
[0071]
Subsequently, in step S11, similarly to the processing in step S9, a recording mark or the like according to the inspection pattern 2 recorded on the disk 22 is reproduced, and ₃ Degree of modulation (I _3-02 ) Is measured.
[0072]
Then, in step S13, I ₃ Degree of modulation (I _3-01 ) And I ₃ Degree of modulation (I _3-02 ) Is equal to or not. It should be noted that, in the flowchart, it is indicated by “=”, but it is not necessary that they completely match, and it is determined that they are almost the same when they almost match (approximately). This approximate range is determined in advance by a developer or a designer.
[0073]
If “YES” in the step S13, that is, I ₃ Degree of modulation (I _3-01 ) And I ₃ Degree of modulation (I _3-02 ) Are equal, it is determined that the optimum power has already been set, and the optimum power determination processing ends, as shown in FIG. On the other hand, if “NO” in the step S13, that is, I ₃ Degree of modulation (I _3-01 ) And I ₃ Degree of modulation (I _3-02 ) Is not equal, then I is determined in step S15. ₃ Degree of modulation (I _3-01 ) Is I ₃ Degree of modulation (I _3-02 ) To determine if it is greater than.
[0074]
If “NO” in the step S15, that is, I ₃ Degree of modulation (I _3-01 ) Is I ₃ Degree of modulation (I _3-02 If the recording power is smaller than Pm, the recording power Pm is set to Pm in step S17. ₀ After substituting + Pmd, the process proceeds to step S21 shown in FIG. Here, Pmd is the initial value Pm of the recording power Pm. ₀ In this embodiment, as described with reference to FIG. 10, the initial value Pm ₀ Is 14.3 mW and Pmd is set to 0.6 mW. However, as shown in FIG. 10, Pmd may be 1.3 mW (Pm = 14.9 mW) or 1.8 mW (Pm = 16.1 mW). This is determined in advance by a developer or a designer, but the recording power Ph (initial value Ph) ₀ = 20 mW), which is set to a value slightly less than 10% (less than 2 mW).
[0075]
On the other hand, if “YES” in the step S15, that is, if I ₃ Degree of modulation (I _3-01 ) Is I ₃ Degree of modulation (I _3-02 ), The recording power Pm is set to Pm in step S19. ₀ After substituting −Pmd, the process proceeds to step S21 shown in FIG.
[0076]
In step S21 shown in FIG. 12, a mark or the like according to the inspection pattern 1 is recorded at a third predetermined address in a predetermined area of the disk 22, using the corrected recording power Pm, as in step S5. Subsequently, in step S23, a mark or the like according to the inspection pattern 2 is recorded at a fourth address of a predetermined area of the disk 22, using the updated recording power Pm, as in step S7.
[0077]
In a succeeding step S25, a recording mark or the like according to the inspection pattern 1 recorded at the third address is reproduced, and similarly to the step S9, the I mark is reproduced. ₃ Degree of modulation (I _3-11 ) Is measured, and in step S27, a recording mark or the like according to the inspection pattern 2 recorded at the fourth address is reproduced. ₃ Degree of modulation (I _3-12 ) Is measured.
[0078]
Then, in step S29, the two types of recording power Pm and the four I ₃ The optimum power Pma is calculated (determined) based on the modulation factor. Specifically, as shown in FIG. 12, two types of recording power (Pm ₀ And Pm ₀ + Pmd) corresponding to the four obtained I ₃ The degree of modulation is plotted on a graph. Subsequently, I obtained from the same inspection pattern ₃ A straight line passing through the plots of the modulation is drawn (obtained). Then, the recording power Pm indicated by the intersection A of the two straight lines is determined as the optimum power Pma.
[0079]
In FIG. 13, two straight lines represent Pm. ₀ And Pm ₀ + Pmd, that is, an intersection A exists between the straight line segments, but considering the experimental results shown in FIG. 10, Ph = 20 mW, Pm ₀ = 14.3 mW, Pm0 + Pmd = 14.9 mW, the intersection of the two straight lines is Pm ₀ And Pm ₀ + Pmd does not exist. However, since a straight line passing through the plot is obtained, the intersection can be obtained with certainty.
[0080]
Thereafter, in step S31, the determined optimum power Pma is substituted for the recording power Pm, and the process ends. That is, the optimum Ph / Pm can be obtained by obtaining the optimum value of the recording power Pm when the recording power Ph is fixed. Therefore, when the optimum power Ph is obtained in the subsequent OPC process, the optimum recording power Pm can be set based on the optimum Ph / Pm.
[0081]
According to this embodiment, the optimum value of Ph / Pm is obtained by using the recording power in the case where a constant modulation degree is always obtained irrespective of the recording power. Optimal power can be set for the disc. Therefore, the reproduction quality does not deteriorate.
[0082]
In this embodiment, the non-multi-pulse method is adopted, but the present invention is not limited to this. For example, in the case of the multi-pulse method as shown in FIG. 4, the recording power in the case where the ratio (duty ratio) between the pulse width of the top pulse and the pulse width of the multi-pulse is optimized is adopted. Good.
[0083]
Further, in this embodiment, the pattern 1 and the pattern 2 are used as the inspection pattern, but this is merely an example and should not be limited to this.
[0084]
Further, in this embodiment, only DVD-R and DVD-RW have been described as disks, but it goes without saying that the present invention can be applied to other recordable disks, such as MO, CD-R, CD-RW, and DVD + RW.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of the present invention.
FIG. 2 is an illustrative view showing one portion of a structure of a disk shown in FIG. 1 embodiment;
FIG. 3A is an illustrative view showing a state in which a main beam and a sub beam are irradiated on a recording surface of a disk, and FIG. 3B is an illustrative view showing a configuration of a photodetector;
FIG. 4 is an illustrative view showing one example of a recording / reproducing characteristic when a multi-pulse method is adopted;
FIG. 5 is an illustrative view showing one example of a recording / reproducing characteristic when a non-pulse method is adopted;
FIG. 6 is an illustrative view showing recording characteristics in a case where recording power is varied while Ph / Pm is fixed at four values in quadruple speed recording.
FIG. 7 is an illustrative view showing another example of the recording / reproducing characteristics when the non-pulse method is adopted;
FIG. 8 is an illustrative view showing another example of the recording / reproducing characteristics when the non-pulse method is adopted;
FIG. 9 is an illustrative view showing one example of an inspection pattern used in a recording power determination process;
FIG. 10A is a graph showing the results of measuring the modulation factor for the inspection pattern and the modulation factor for the inspection pattern 2 when the recording power Ph is fixed and the recording power Pm is changed. B) is a graph showing the result of measuring the jitter and β when the recording power Pm is changed while the recording power Ph is fixed.
FIG. 11 is a flowchart showing a part of a recording power determination process of the CPU shown in the embodiment in FIG. 1;
FIG. 12 is a flowchart showing another part of the recording power determination process of the CPU shown in FIG. 1 embodiment.
FIG. 13 is an illustrative view for explaining a method for determining an optimum power of the recording power Pm;
[Explanation of symbols]
10… Disk device
12 ... Optical pickup
30… Matrix amplifier
32 ... DSP
40 ... CPU
42 ... Address detection circuit (decoder)

Claims (5)

In a disc reproducing apparatus for recording a signal on a disc by driving a laser diode with first and second laser powers and emitting laser light from an optical pickup,
The laser diode is driven with a first predetermined laser power and a second predetermined laser power, and a first recording mark according to a first pattern and a second recording mark according to a second pattern different from the first pattern are formed in a predetermined area of the disk. First mark recording means for recording
First mark reproducing means for reproducing the first recording mark and the second recording mark recorded by the first mark recording means;
First detection means for detecting a first modulation degree of a first reproduction signal corresponding to the first recording mark reproduced by the first mark reproduction means;
Second detection means for detecting a second modulation degree of a second reproduction signal corresponding to the second recording mark;
First determining means for determining whether the first modulation degree is equal to the second modulation degree, and when the first modulation degree is determined to be equal to the second modulation degree by the first determining means. A disk device for determining the first predetermined laser power and the second predetermined laser power to be the optimum laser power. The determining means includes: comparing means for comparing the magnitudes of the first modulation degree and the second modulation degree when the first modulation degree and the second modulation degree are not equal; and a comparison result of the comparing means. Setting means for correcting the second predetermined laser power based on the first predetermined laser power and setting the corrected laser power based on the first predetermined laser power and the corrected laser power. A second mark recording means for recording in the area, a second mark reproducing means for reproducing the first recording mark and the second recording mark recorded by the second mark recording means, and a second mark reproducing means for reproducing the first and second recording marks. Third detection means for detecting a third modulation degree of a third reproduction signal corresponding to the first recording mark, and the second recording mark reproduced by the second mark reproduction means. And a fourth detection means for detecting a fourth modulation degree of a fourth reproduction signal corresponding to the first phase, and an optimum power determination means for determining the optimum laser power based on the first to fourth modulation degrees. The disk device as described above. The optimum power determining means plots the first to fourth modulation degrees with respect to the second predetermined laser power and the correction laser power on a two-dimensional coordinate when the first predetermined laser power is fixed, and A laser power indicated by an intersection of a first straight line connecting the first and third modulation degrees and a second straight line connecting the second and fourth modulation degrees is determined as the optimum laser power of the second laser power. 3. The disk device according to claim 2, wherein The first pattern and the second pattern are a first mark recorded with only the first predetermined laser power, a first space having the same length as a first mark length of the first mark, and the first predetermined laser. A second mark longer than the first mark length and a second space having the same length as the second mark length of the second mark recorded with the power and the second predetermined laser power,
4. The disk device according to claim 1, wherein the first marks, the first spaces, the second marks, and the second spaces have the same appearance frequency but different arrangements. 5. The disk drive according to claim 4, wherein said first pattern arranges said second marks immediately before said first space, and said second pattern arranges said first marks immediately before said first space. .

Images