JP2606509B2 - Optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for recording information on an optical disk or reproducing the recorded information by using a light spot focused on a semiconductor laser. The present invention relates to an optical disk device that performs track detection and correction.

[0002]

2. Description of the Related Art In recent years, an optical disk capable of recording digital audio has been developed for a read-only optical disk represented by a compact disk. In write-once (W / O) recording is possible only once, a dye-based recording film is used. In a rewritable type in which recording can be repeated, two types of recording films of magneto-optical (MO) and phase change (PC) are employed. In both the write-once and rewritable discs, tracks are wobbled (meandering) in the track width direction, and management information such as position information is recorded.

[0003] A conventional optical disk device using these recordable optical disks will be described below.

FIG. 10 shows a block diagram around a servo circuit of the conventional optical disk apparatus. In FIG. 10, 1 is a recordable optical disk, 2 is an optical disk 1
Is a spindle motor for rotating the optical disc 1. The light output of the semiconductor laser 4 serving as a light source is controlled by a laser drive circuit 5. The light beam emitted from the semiconductor laser 4 is converted into parallel light by a collimating lens 6 and then passes through a polarizing beam splitter 7 to
The light is converted into circularly polarized light by the λ / 4 plate 8, narrowed down by the objective lens 9, and forms a light spot on the recording medium 2 of the optical disk 1.

The objective lens 9 is provided with a focus actuator 10a for controlling the position of a light spot in a focus direction parallel to the optical axis. Also,
The objective lens 9 is provided with a tracking actuator 10b for controlling the position of a light spot in the radial direction of a track on the optical disc 1.

The light incident on the optical disk 1 is reflected by the recording medium 2 of the optical disk 1, passes through the objective lens 9, is converted into linearly polarized light by the λ / 4 plate 8, is reflected by the polarization beam splitter 7, and Enter the detector 11.

The arithmetic circuit 12 calculates the output of the divided photodetector 11, and outputs a focus error signal FE indicating a defocus of the light spot and a tracking error signal TE indicating a deviation from the track center. The tracking error signal is detected using a push-pull method in order to detect a wobble signal.

The focus control means 13 drives the focus actuator 10a in a focus direction parallel to the optical axis in accordance with the focus error signal FE. The tracking control means 14 drives the tracking actuator 10b in the radial direction of the track according to the tracking error signal TE.

The wobble signal detection circuit 15 extracts the band of the wobble signal by passing the tracking error signal TE through a band-pass filter, and detects an analog wobble signal. A wobble signal WB obtained by digitizing the analog wobble signal is output to the wobble decoding circuit 16.

The wobble decode circuit 16 decodes the wobble signal WB and reproduces management information such as position information. Also, a wobble error WBER included in the wobble signal WB is detected.

Next, the wobbled track of the optical disk 1 will be described with reference to FIG. In FIG.
The top figure shows the track in the radial direction.
The middle diagram shows the track viewed in a tangential direction perpendicular to the radial direction. The lower diagram shows a tracking error signal TE when a light spot crosses the track.

Here, the track has 100 lands and 10 lands.
It is composed of one groove. The land 100 and the groove 101 are cut in the radial direction at a pitch P. 10
Numeral 2 is a view of the track in the tangential direction. As can be seen from the figure, the track 2 wobbles at a predetermined cycle. Reference numeral 103 denotes a center line of the wobbled groove 101. 104 is an average center line of the groove 101 (hereinafter, referred to as a center line).
Called the average centerline. ). Reference numeral 105 denotes a deviation amount of the average center line 104 from the center line 103. This shift amount is expressed as a
If the light spot traces on the average center line 104, this a indicates the deviation from the center line 103 of the wobbled track. This means that when the light spot traces on the average center line 104, a wobble signal W having a component corresponding to the shift amount a is generated in the push-pull tracking error signal TE.

Assuming that the amplitude of the tracking error signal TE is A and the tracking error signal TE is approximated by a sine wave, the amplitude of the wobble signal W can be expressed as W = A * sin (2πa / P). The wobble signal W changes sinusoidally in the track tangential direction as the shift amount a changes. Here, assuming that the maximum amplitude of the wobble signal is A1 and the time change of the wobble signal is w (t), w (t) = A1 * sin (ωt).

Next, the recording operation of the conventional optical disk device configured as described above will be described with reference to FIG.

FIG. 12 shows, from the top, a waveform diagram of the light output of the semiconductor laser, the state of the track before recording, and the state of the track after recording. Here, the waveform diagram of the light output basically corresponds to a write-once or magneto-optical type recording medium, and has two levels of a reproduction level PPLY and a recording level PREC.
In a phase-change type recording medium, an erasing level is basically added, and the recording medium becomes ternary. During playback, the low output playback level PPLY
Thus, the light is controlled in a DC manner. At the time of recording, the signal is modulated by a recording signal between the high output recording level PREC and the vicinity of the reproduction level PPLY. The difference between the light outputs at the time of modulation is indicated as δP1.

Before recording, the blank track
Recording pits are recorded where the optical output reaches the recording level.

[0017]

In the above-mentioned conventional configuration, when an offset exists in the tracking control means 14, the light spot goes off-track from the center of the track, and the recording or reproducing characteristics deteriorate. Offsets that cause off-track include deviation of the optical detector 11 in the optical head, deviation of the optical components, inclination of the optical head and the optical disk, manufacturing variation of the optical disk track, electrical offset of the arithmetic circuit 12, tracking control. There are various sources of occurrence, such as the electrical offset of the means 14. For this reason, even if the offset is adjusted in the initial setting, there is a problem that the offset occurs due to a change over time and the light spot goes off-track. Further, simply adjusting the electrical offset cannot adjust the optical offset, and the light spot goes off-track. Furthermore, since the off-track of the light spot cannot be detected with high accuracy, it is difficult to correct the off-track of the light spot.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an optical disk apparatus having stable recording and reproduction characteristics by reliably detecting and correcting off-track of a light spot.

[0019]

In order to achieve this object, an optical disc apparatus according to the present invention comprises a wobble signal detection circuit for detecting a wobble signal included in a tracking error signal, and a wobble error by decoding the wobble signal. A wobble decoding circuit, a wobble error measuring circuit for measuring a wobble error and outputting a wobble error rate, an offset adding means for adding an offset to a tracking control means to offtrack an optical spot, and increasing or decreasing the offset. The offset variable means includes: an offset variable means for holding; and an offset searching means for causing the offset variable means to hold the searched offset after searching for an offset that minimizes the wobble error rate during recording.

[0020]

According to the present invention, the offset set by the offset varying means is added to the tracking control means to off-track the light spot. In this state, the optical output is set to the recording state, and the wobble error rate during recording is measured by the wobble error measurement circuit. When the optical output is modulated in the recording state, the error of the wobble signal with respect to off-track is larger at the time of reproduction than when the optical output is DC, the off-track detection sensitivity is increased, and the wobble error rate is reliably detected. be able to. The offset searching means searches for an offset at which the wobble error rate during recording is near the minimum while varying the offset. The off-track of the light spot is set to an optimum position while holding the offset searched by the offset varying means. In this way, the off-track of the light spot is reliably detected from the wobble error rate during recording, the tracking offset is set, and the off-track of the light spot is corrected, so that the recording / reproducing characteristics of the optical disk device are stabilized. It can be.

[0021]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical disk device according to an embodiment of the present invention. A description will be given of a newly added portion in FIG. 10 which is a block diagram of the conventional example described above. In FIG. 1, reference numeral 17 denotes a wobble error measurement circuit which measures a wobble error WBER from the wobble decode circuit 16 for a predetermined time and outputs a wobble error rate WBERR which is an error rate per time. A comparison circuit 18 compares the wobble error rate WBERR with a predetermined comparison value VREF and outputs the result. The predetermined comparison value VREF is a value of the wobble error rate WBERR when off-track is optimal. Reference numeral 19 denotes an offset search circuit which searches for an optimum offset for an off-track where the wobble error rate WBERR during recording is close to the minimum based on the output of the comparison circuit 18. Reference numeral 20 denotes an offset variable circuit which varies the offset VOF to be added to the tracking control means 14 and holds the searched optimum offset. The offset variable circuit 20 includes a counter 20
a and a DA converter 20b. Counter 20
a is controlled by three signals. The UP signal is output from the counter 2
The counter 20a is counted in the direction in which the output of 0a increases. The DW signal is output from the counter 2 in the direction in which the output decreases.
0a is counted. The HLD signal is output from the counter 20a.
Stop the counting operation. The digital output DATA of the counter 20a is connected to the DA converter 20b, and an analog voltage corresponding to the magnitude of the digital output DATA is output. This analog voltage becomes the offset VOF of the tracking control means 14. An offset adding circuit 21 adds the offset VOF of the variable offset circuit 20 to the tracking control means 14.

The wobble error rate WBER of the optical disk device of the present embodiment configured as described above will be described below.
The off-track correction based on the detection of R will be described.

First, the relationship between the wobble error rate WBERR and the off-track will be described with reference to FIG.
In the graph of FIG. 2, the off-track amount is plotted on the horizontal axis, and the wobble error rate WBERR is plotted on the vertical axis. The data shown is
The wobble error rate WBERR during reproduction and the wobble error rate WBERR during recording. Basically, the recording is assumed to be a write-once type modulated at the recording level or a magneto-optical type. A broken line VREF indicates a predetermined comparison value of the comparison circuit 18. The Spec of the broken line indicates the specification of the wobble error rate WBERR. The wobble error rate WBERR during reproduction changes gently with respect to the off-track amount and has little effect. On the other hand, the wobble error rate WBERR during recording has a large change with respect to the off-track amount. Thus, the wobble error rate W during recording is
BERR has higher off-track detection sensitivity. Satisfaction of the general wobble error rate WBERR specification of 10 minus the first power is required when the off-track amount is in a range of ± 0.1 μm. By utilizing this, an offset for correcting the off-track to an optimum value can be set by reliably searching for an off-track having a wobble error rate WBERR near the minimum during recording.

The difference between the wobble error rate WBERR, which is the off-track detection sensitivity in recording and reproduction, can be explained as follows. First, when the light output is constant at DC during reproduction, the time change of the wobble signal is expressed as w (t) = A1 * sin (ωt) as described above. If the light spot is off-track, a DC offset is also applied to the wobble signal. Since the wobble signal has a wobbled width smaller than the track pitch, the offset is significantly increased. Assuming that the offset component is ADC, the wobble signal is expressed as w (t) = ADC + A1 * sin (ωt).

Next, at the time of recording, the light output is modulated by the recording signal. EFM for digital audio
(Eight To Fourteen modulation).
If the light at the time of recording is md (t), the wobble signal wr (t) to be read during recording is wr (t) = w (t) * md (t) = ADC * md (t) + A1 * sin (Ωt) * md
(T). To remove the wobble signal component sin (ωt), the bandpass filter removes the recording EFM component md (t). However, since the md (t) component cannot be completely removed, the influence of the EFM component appears as noise. Further, when the light spot is off-track, a large offset component ADC is generated in the wobble signal, and the noise caused by the offset component ADC affects the signal, so that the signal S / N is further deteriorated.

For the reasons described above, the off-track wobble error rate WBERR is greatly affected and deteriorated during the light-modulated recording as compared with the reproduction, so that the off-track detection sensitivity is increased.

Next, the operation of the offset search circuit 19 of this embodiment for searching for an off-track whose wobble error rate WBERR is near the minimum will be described with reference to FIG.

FIG. 3 is a graph of FIG. 2 and shows the wobble error rate WBERR during recording where the off-track is around 0.02 μm.
It is an expansion of. Although the off-track amount is plotted on the horizontal axis, this is a linear relationship with the offset VOF added to the tracking control means 14. The offset at which the wobble error rate WBERR is minimized is when the off-track of the light spot is almost equal to zero. In case B below, the offset at which the wobble error rate WBERR is the minimum is when the off-track of the light spot is +0.0.
This is the case where it is shifted to 1 μ.

The operation of the offset search circuit 19 will be described with reference to the graph of Case A. First, the offset search circuit 19 sets the data of the counter 20a of the offset variable circuit 20 to 0, and sets the offset output VOF of the DA converter 20b.
Is set to 0. This corresponds to an off-track amount of 0μ,
This is a point indicated by n = 1 in the graph. At this time, the wobble error rate WBERR in the recording state is compared with the comparison circuit 18.
To compare with VREF. Wobble error rate WBERR is V
It is determined that it is smaller than REF. Based on the result, the offset search circuit 19 counts up the counter 20a and increases the offset VOF. This corresponds to the off-track amount of 0.005 μ indicated by n = 2, and the wobble error rate WBERR in the recording state at this time is compared with the comparison circuit 18.
Is compared with VREF. The wobble error rate WBERR is VR
Determined to be less than EF. Based on this result, the offset search circuit 19 counts up the counter 20a and repeats the same operation as above. This operation is repeated until the wobble error rate WBERR exceeds the comparison value VREF of the comparison circuit 18, and n = 1, 2, 3, 4,
5 is indicated. When the offset is 0.02 μm of off-track indicated by n = 5, the wobble error rate WBERR exceeds the comparison value VREF.

At this time, the offset search circuit 19 shifts the counter 20a from data 0 to a countdown operation, and sets the offset VOF to a negative value. This is n
= The off-track amount represented by = −0.005 μ, and the wobble error rate WBERR in the recording state at this time.
Is compared with VREF by the comparison circuit 18. It is determined that the wobble error rate WBERR is smaller than VREF. Based on this result, the offset search circuit 19 counts down the counter 20a and repeats the same operation as above. This is because the comparison value VREF of the comparison circuit 18 is changed to the wobble error rate WB.
The process is repeated until the ERR is exceeded.
7, 8, and 9 are indicated. When the offset VOF corresponds to -0.02 μm of the off-track indicated by n = 9, the wobble error rate WBERR exceeds the comparison value VREF.

At this time, the offset search circuit 19 sets the wobble error rate WBERR to a value near the minimum from the offsets n = 1, 2, 3, 4, 6, 7, and 8 indicating the wobble error rate WBERR lower than the comparison value VREF. The offset VOF of n = 1 is selected. This is specifically possible if the data is stored in a memory. Alternatively, the determination may be made by software.

Data for generating the selected offset VOF is generated in the counter 20a, and thereafter, the operation of the counter 20a is stopped by the HLD signal. Based on the data DATA held by the counter 20a, the D / A converter 20b holds the offset VOF that makes the wobble error rate WBERR close to the minimum.
1 is added to the tracking control means 14. As a result, the light spot is controlled at the optimal track position of the off-track 0 μ where the wobble error rate WBERR is near the minimum. This means that the wobble error rate WBE is not only in the recording state but also in the reproducing state.
The offset VOF at which RR is close to the minimum is maintained.

In case B, the operation of the offset search circuit 19 is the same. Starting with n = 1 on the graph,
The offset VOF increases so that the off-track is in the plus direction until n = 7, at which the wobble error rate WBERR during recording of the comparison value VREF of the comparison circuit 18 is exceeded. When the wobble error rate WBERR exceeds the comparison value VREF at n = 7, the offset VOF increases to the negative side. If the wobble error rate WBERR exceeds the comparison value VREF at n = 9, the offset search circuit 19 sets an offset n = 9 indicating a wobble error rate WBERR lower than the comparison value VREF.
From 1,2,3,4,5,6,8, the wobble error rate W
An n = 3 offset corresponding to off-track +0.01 μ with BERR as the minimum neighborhood is selected.

Data for generating the selected n = 3 offset VOF is generated in the counter 20a, and the operation of the counter 20a is stopped by the HLD signal. Counter 20a
By the data DATA held by the D / A converter 20b,
The offset VOF that keeps the wobble error rate WBERR in the vicinity of the minimum is held, and the offset VOF is added to the tracking control unit 14 by the offset adding circuit 21.
As a result, the light spot is controlled to an optimum track position of off track +0.01 μ where the wobble error rate WBERR is near the minimum.

As described above, according to this embodiment, the wobble signal detection circuit for detecting the wobble signal included in the tracking error signal, the wobble decoding circuit for decoding the wobble signal to detect the wobble error, and the wobble error A wobble error measuring circuit for measuring a predetermined time and outputting a wobble error rate; an offset adding means for adding an offset to the tracking control means to off-track the light spot; and comparing the wobble error rate with a predetermined comparison value A comparing unit, an offset varying unit that increases or decreases or holds the offset; and an offset varying unit that controls the offset varying unit in accordance with a result of the comparing unit to search for an offset that minimizes a wobble error rate during recording. Off that causes the variable means to retain the searched offset By providing the Tsu bets searching means, the off-track of the light spot is corrected to reliably detect the recording and reproducing characteristics of the optical disk apparatus can be stabilized. Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that the comparison circuit 18 is eliminated and the plurality of offset VOFs set by the variable offset variable circuit 20 and the wobble error rate WBERR during recording corresponding to the plurality of offsets VOF are obtained. The relationship is approximated by a predetermined formula, and an offset at which the wobble error rate WBERR during recording becomes near the minimum is searched.

The operation of the second embodiment will be described with reference to FIG. In FIG. 4, the horizontal axis represents the offset VOF and the linear off-track amount, and the vertical axis represents the wobble error rate WBE during recording.
RR is taken. In FIG. 4, an offset search circuit 19 causes a variable offset circuit 20 to generate five offsets VOF corresponding to off-track ± 0.02 μ. First, off-track −0.02 indicated by n = 1
An offset VOF corresponding to μ is set. The wobble error rate WBERR during recording at the time of the offset VOF is measured by the wobble error measurement circuit 17 and is held in the memory.

Similarly, the wobble error rate WB during recording corresponding to the offset VOF represented by n = 2, 3, 4, 5
ERR is measured and stored in memory.

From the relationship between the offset VOF at the five points n = 1, 2, 3, 4, and 5 and the wobble error rate WBERR during recording, the wobble error rate during recording is calculated using an approximate expression such as the least square method. An offset VOF with WBERR near the minimum is searched for. In FIG. 4, the off-track +0.01 μ corresponding to the offset VOF at the point n = 4 is searched for the wobble error WBERR rate during recording being the minimum. The searched offset VOF is the offset variable circuit 2
It is held at 0. The held offset VOF is output from the tracking control means 1 by the offset adding circuit 21.
4 is added.

Thus, without using the comparison circuit, the light spot is controlled to the optimum track position of off-track +0.01 μ where the wobble error rate WBERR during recording is near the minimum. Since the approximate expression is used, the number of measurement points is relatively small and the accuracy can be improved. Further, the calculation by the approximate expression using the measurement points can be performed by software.

As described above, according to the present embodiment, the relationship between the plurality of offsets set by the offset varying means and the wobble error rate during recording corresponding to the plurality of offsets is approximated by a predetermined formula, and the recording is performed. Since the wobble error rate in the medium is searched for an offset that is close to the minimum, the circuit configuration can be simplified as compared with the one using a comparison circuit, and the number of measurement points is small, and the accuracy can be improved.

Next, a third embodiment of the present invention will be described.
The third embodiment is an optical disc apparatus including a phase change optical disc and a laser drive circuit for modulating the light of a semiconductor laser between an erasing level and a recording level by a recording signal, and reproducing the erasing level. Recording is performed at a level near or below the level, and off-track of the light spot is detected and corrected.

The operation of the phase change optical disk during overwriting will be described with reference to FIG. FIG. 5 shows a waveform diagram of the light output of the semiconductor laser, a state of the track before overwriting, and a state of the track after overwriting from above. At the time of overwriting, the light is modulated by δP2 between the erasing level and the recording level with respect to the reproducing level that emits at DC.

The recording pits recorded before overwriting are erased by irradiating the overwriting light, and new recording pits are recorded at the same time. Basically, a phase-change disk is crystalline in an erased state and amorphous in pits in a recorded state. That is, when light of a recording level is applied, the film is heated to a temperature higher than the melting point and rapidly cooled to be in an amorphous state. When light at the erasing level is applied, the light is heated to a temperature higher than the crystallization temperature and lower than the melting point, and becomes a crystalline state.

Here, in the optical output waveform diagram of the conventional example shown in FIG. 12, the difference in optical output at the time of modulation was δP1. The greater the difference δP1 between the optical outputs, the greater the wobble error rate WB
Since the ERR deteriorates, the off-track detection sensitivity increases.

In contrast to the optical output difference δP1 during modulation in the conventional example, the optical output difference δP2 during phase change type modulation is between the recording level and the erasing level. This is because the light output difference is smaller by the erasing level, the wobble error rate WBERR is less deteriorated, and the detection sensitivity is lower.

Therefore, in the third embodiment of the present invention, as shown in FIG. 6, the recording light waveform is set to an erasing level near or below the reproducing level to minimize the wobble error rate WBERR during recording. Search for an offset to be nearby. The optical output difference at the time of modulation is δP3, which is larger than δP2 at the time of overwriting. In a phase change type disk, if the erasing level is low, erasing cannot be performed, and overwriting operation becomes impossible. However, if the track to be searched for the offset is a blank in which no recording is performed, the recording operation does not cause any problem.

FIG. 7 shows the relationship between the off-track amount and the wobble error rate WBERR in the third embodiment of the present invention. In FIG. 7, the horizontal axis represents the off-track amount, and the vertical axis represents the wobble error rate WBERR. The data indicates two types of data other than reproduction and recording. One is in the overwrite mode, and the other is in the write-once mode in which the erase level is set to the reproduction level or lower.

Even in the overwrite mode, off-track detection sensitivity is higher than during reproduction, and the off-track detection and correction can be performed using this. However, the write-once mode has higher off-track detection sensitivity than the overwrite mode. By utilizing this, by recording in the write-once mode, it is possible to reliably and reliably search for an off-track with a wobble error rate WBERR near the minimum during recording, and to set an offset for correcting the off-track to an optimum value. Can be set.

As described above, according to this embodiment, the phase-change optical disk, the laser drive circuit for modulating the light of the semiconductor laser between the erasing level and the recording level by the recording signal, and the erasing level After searching for an offset that sets the wobble error rate during recording to a value near or below the reproduction level at or near the reproduction level, the offset variable means includes offset search means for holding the searched offset. Also in an optical disk, the off-track of a light spot can be reliably detected and corrected, and the recording / reproducing characteristics of the optical disk device can be stabilized.

Next, a fourth embodiment of the present invention will be described.
The fourth embodiment is an optical disc apparatus including a phase-change optical disc and a laser drive circuit for modulating the light of a semiconductor laser between an erasing level and a recording level by a recording signal. The track is erased before searching for an offset that makes the wobble error rate WBERR during recording close to the minimum.

In order to search for an offset that makes the wobble error rate WBERR near the minimum during recording in the write-once mode on a phase-change optical disc, the track must be blank. This is for every offset search,
A predetermined blank track for the test is always used, and the area of the optical disc that can be recorded as user data is reduced.

Therefore, in the fourth embodiment of the present invention, first, the track on which the offset search is performed is deleted. This is because, for a phase-change optical disk, the light is set to an erasing level and D
This can be easily realized by erasing C or overwriting the recording signal with zero. Wobble error rate WBER during recording in write-once mode on erased track
An off-track with R near the minimum can be reliably searched for, and an offset for correcting the off-track to an optimum value can be set.

As described above, according to the present embodiment, the phase-change optical disk, the laser driving circuit for modulating the light of the semiconductor laser between the erasing level and the recording level by the recording signal, and the track erasing. Then, after searching for an offset that sets the erasure level to near or below the reproduction level and makes the wobble error rate during recording near the minimum, the offset variable means holds the searched offset. With this arrangement, in a phase-change optical disk, off-track of a light spot can be reliably detected and corrected, the recording / reproducing characteristics of the optical disk device can be stabilized, and the use efficiency of the recording area of the optical disk can be increased.

Next, a fifth embodiment of the present invention will be described.
In the fifth embodiment, an offset search with the wobble error rate WBERR in the vicinity of the minimum is executed in a predetermined track. If an offset is recorded on the tracking control means in the data area of the user, the light spot goes off-track, and there is a possibility that data on an adjacent track may be destroyed. For this reason, in a track in a predetermined area other than the data area of the user, an offset for setting the wobble error rate WBERR in the vicinity of the minimum is searched.

As described above, according to this embodiment, the offset search with the wobble error rate WBERR in the vicinity of the minimum is executed in a predetermined track, so that the recording / reproducing characteristics of the optical disk device are stabilized and the data of the user Can be prevented from being recorded off-track and destroyed.

Next, a sixth embodiment of the present invention will be described. In the sixth embodiment, when an optical disk is inserted into an optical disk device, an offset search for setting the wobble error rate WBERR in the vicinity of the minimum is executed in a predetermined track.

The off-track of the optical disk device does not change much if the correction is set once for one optical disk. Therefore, if the offset search is performed every time the optical disk is inserted into the optical disk device, the off-track can be surely corrected.

As described above, according to the present embodiment, when an optical disk is inserted into the optical disk device, the offset search for setting the wobble error rate WBERR in the vicinity of the minimum is executed in a predetermined track. It is possible to stabilize the reproduction characteristics, absorb variations of the optical disk, and improve the system operation efficiency of the optical disk device.

Next, a seventh embodiment of the present invention will be described. In the seventh embodiment, the offset search means uses the wobble error rate WBER obtained by subtracting the wobble error rate WBERR during reproduction from the wobble error rate WBERR during recording.
This is to execute an offset search in which R is near the minimum.

The operation will be described with reference to FIG. FIG.
Is the off-track amount on the horizontal axis and the wobble error rate W on the vertical axis.
Takes BERR. The data includes three types of data: a wobble error rate WBERR during normal reproduction, and a wobble error rate WBERR during reproduction and recording when a wobble error rate is lower than that during normal reproduction due to a defect in a track of an optical disc. Is shown.

In a defective track, the wobble error rate WBERR becomes even worse during reproduction. Point P
As shown by 1, even off-track 0 μm is 10 −4, which is worse than 10 −5 during normal reproduction. When the offset search of the present invention is performed on such a track, the predetermined comparison value VREF does not cross the wobble error rate WBERR during recording and is not compared.

For this reason, the wobble error rate WBERR during reproduction indicated by the point P1 is held, and the corrected wobble error rate WBER obtained by subtracting the wobble error rate WBERR during reproduction from the wobble error rate WBERR during recording.
R is used. The corrected wobble error rate WBERR is
An error uniformly generated due to a track defect or the like is corrected, and the comparison circuit 18 makes it possible to make a comparison using a predetermined comparison value VREF. As a result, an offset search can be performed, and off-track correction can be performed without being affected by a defective track.

As described above, according to this embodiment, the wobble error rate WBERR obtained by subtracting the wobble error rate WBERR during reproduction from the wobble error rate WBERR during recording.
, The off-track can be reliably corrected without being affected by variations in the optical disc, track defects, and the like.

Next, an eighth embodiment of the present invention will be described. In the eighth embodiment, the wobble error rate WB at the time of reproduction is
In the case of a track having an ERR exceeding a predetermined error rate, an offset search is not performed, and an offset is set in another track so that the wobble error rate WBERR being recorded is in the vicinity of the minimum.

Wobble error rate WBERR exceeding the specification due to a large defect or the like in the track for which the offset search is performed.
At the time of reproduction, the offset search recorded on such a track is not reliable. For this reason, in the track on which the offset search is performed, first, it is checked whether the wobble error rate WBERR during reproduction does not exceed a predetermined error rate. If the wobble error rate WBERR during reproduction exceeds a predetermined error rate, the track for offset search is moved to another track. The wobble error rate WBE during recording is varied by changing the offset
An offset at which RR is near the minimum is searched for.

The wobble error rate WBERR during reproduction is
If the error rate is lower than the predetermined error rate, an offset search is performed on the track. That is, the offset search is performed only on the track whose wobble error rate WBERR during reproduction is lower than the predetermined error rate, and the reliability is greatly improved.

As described above, according to this embodiment, when a wobble error rate WBERR at the time of reproduction exceeds a predetermined error rate, the track is shifted to another track and the wobble error rate WBERR during recording is set to a value near the minimum. An offset search is performed, and the reliability of the searched offset can be improved.

Next, a ninth embodiment of the present invention will be described. The ninth embodiment is characterized in that the comparison circuit 18 varies a predetermined comparison value VREF. The operation will be described with reference to FIG. FIG. 9 shows the off-track amount on the horizontal axis and the wobble error rate WBERR on the vertical axis. The data indicates wobble error rate WBERR data during recording when a track has a defect or the like.

The minimum value of the wobble error rate during recording does not cross the predetermined comparison value VREF, and the offset search circuit 19 cannot find an offset having the wobble error rate WBERR in the vicinity of the minimum. In this case, the predetermined comparison value VREF is changed to VREF2.
As a result, the wobble error rate WBERR during recording crosses the predetermined comparison value VREF2, and the offset search circuit 19
Can find an offset that makes the wobble error rate WBERR a minimum neighborhood.

As described above, according to the present embodiment, the comparison circuit 18 makes the predetermined comparison value VREF variable so that the off-track can be reliably performed without being affected by variations in the optical disk or track defects. Correction can be applied.

Next, a tenth embodiment of the present invention will be described. In the tenth embodiment, the level of the predetermined comparison value VREF of the comparison circuit 18 is changed to the wobble error rate WBE during reproduction.
It is variable according to RR.

When the wobble error rate WBERR during recording does not cross the predetermined comparison value VREF due to a track defect or the like, the predetermined comparison value VREF is variably dealt with.
At this time, the variable level of the predetermined comparison value VREF is set based on the wobble error rate WBERR during reproduction. As a result, an appropriate comparison circuit 1 can be selected according to the state of the disk.
8, the level of the comparison value VREF can be determined, and the offset search circuit 19 can find the offset that makes the wobble error rate WBERR the minimum.

As described above, according to the present embodiment, the comparison circuit 18 makes the level of the predetermined comparison value VREF variable according to the wobble error rate WBERR during reproduction. Irrespective of the defect of the device, the off-track correction can be performed reliably.

In this embodiment, the laser drive circuit for controlling the light output to the ternary level of recording, erasing and reproduction is made compatible with a phase-change type optical disk. The present invention can be applied as it is.

In the second embodiment, the least square method is used to determine the wobble error rate in the vicinity of the minimum. However, any approximation may be used as long as the approximation of the point in the vicinity of the minimum is obtained. Absent.

[0077]

As described above, according to the present invention, the off-track of a light spot is reliably detected from the wobble error rate during recording, and the off-track of the light spot is corrected, thereby improving the recording / reproducing characteristics of the optical disk device. Can be stable.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a wobble error rate WBERR and off-track in the embodiment.

FIG. 3 is a characteristic diagram showing a relationship between an off-track amount and a wobble error rate for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between an off-track amount and a wobble error rate for explaining the operation of the second embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining an overwrite state of a phase-change optical disc according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram for explaining a state of recording in a write-once mode in the third embodiment.

FIG. 7 is a characteristic diagram for explaining a wobble error rate at the time of overwriting and write-once in the third embodiment.

FIG. 8 is a characteristic diagram for explaining a wobble error rate during normal reproduction and abnormal reproduction in a seventh embodiment of the present invention.

FIG. 9 is a characteristic diagram for explaining variation of a predetermined comparison value VREF of a comparison circuit according to a ninth embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration around a servo circuit of a conventional optical disk device.

FIG. 11 is an explanatory diagram for explaining a wobbled track of a conventional optical disc.

FIG. 12 is an explanatory diagram for explaining a recording operation of a conventional optical disk device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 recordable optical disk 2 recording medium 4 semiconductor laser 5 laser drive circuit 14 tracking control means 15 wobble signal detection circuit 16 wobble decode circuit 17 wobble error detection circuit 18 comparison circuit 19 offset search circuit 20 offset variable circuit 21 offset addition circuit

Claims (11)

(57) [Claims] 1. A recordable optical disk having a wobble track, an optical system that uses a light of a semiconductor laser as a light source as an aperture light spot, an actuator that drives the optical system in a focus direction or a track direction, and a light of the semiconductor laser. A laser drive circuit that controls the read / erase / record level and modulates it with a recording signal, a photodetector that detects reflected light from an optical disk, and generates a tracking error signal by calculating the signal of the photodetector An arithmetic circuit; a wobble signal detection circuit for detecting a wobble signal included in the tracking error signal; a wobble decoding circuit for decoding the wobble signal to reproduce information included in the wobble signal and detecting a wobble error; Wobble error measurement circuit that measures and outputs the wobble error rate Tracking control means for controlling the actuator in the track direction by the tracking error signal to control the light spot on the track; offset adding means for adding an offset to the tracking control means to off-track the light spot; An optical disc apparatus comprising: an offset varying means for increasing, decreasing, or holding the offset; and an offset searching means for causing the offset varying means to hold the searched offset after searching for an offset that minimizes the wobble error rate during recording. 2. The apparatus according to claim 1, further comprising a comparing unit that compares the wobble error rate with a predetermined comparison value and outputs a result of the comparison. 2. The optical disk device according to claim 1, wherein after searching for an offset having an error rate near the minimum, the offset varying means holds the searched offset. 3. The wobble during recording is approximated by a predetermined formula, wherein the relationship between the plurality of offsets set by the offset varying means and the wobble error rate during recording corresponding to the plurality of offsets is determined. 2. The optical disk device according to claim 1, wherein after searching for an offset having an error rate near the minimum, the offset varying means holds the searched offset. 4. A rewritable phase-change optical disk having wobbled tracks, a laser drive circuit for modulating the light of a semiconductor laser between an erasing level and a recording level by a recording signal, and a erasing level at a reproducing level. 4. An offset searching means for searching for an offset which is set to a value close to or less than the wobble error rate during recording, and causing the offset variable means to hold the searched offset. Optical disk device. 5. A rewritable phase-change optical disk having wobbled tracks, a laser drive circuit for modulating the light of a semiconductor laser between an erasing level and a recording level by a recording signal, and after erasing the tracks. Offset search means for setting the level of erasure near or below the reproduction level, searching for an offset that minimizes the wobble error rate during recording, and then causing the offset variable means to hold the searched offset. Item 5. The optical disk device according to item 1, 2, 3, or 4. 6. The offset searching means, wherein a predetermined wobble error rate in a predetermined track is searched for an offset which is close to the minimum, and then the offset variable means holds the searched offset. 2,
The optical disk device according to 3, 4, or 5. 7. The offset searching means searches for an offset that minimizes the wobble error rate during recording on a predetermined track when the optical disk is inserted into the optical disk device, and then holds the searched offset in the offset variable means. Claims 1, 2, 3,
7. The optical disk device according to 4, 5, or 6. 8. An offset searching means for searching for an offset which makes a wobble error rate obtained by subtracting a wobble error rate at the time of reproduction from a wobble error rate during recording a minimum value, and then causing the variable offset means to hold the searched offset. The method according to claim 1, 2, 3, 4, 5, 6, or 7.
An optical disk device as described in the above. 9. The offset search means, when a wobble error rate during reproduction exceeds a predetermined error rate, for a track,
4. The method according to claim 1, further comprising the step of: searching for an offset that minimizes the wobble error rate during recording in another track, and then holding the searched offset in an offset variable unit.
An optical disk device according to 4, 5, 6, 7 or 8. 10. The optical disk apparatus according to claim 2, wherein the comparing means changes a level of a predetermined comparison value to be compared with the wobble error rate. 11. The apparatus according to claim 2, wherein said comparing means varies a level of a predetermined comparison value according to a wobble error rate during reproduction.
An optical disk device as described in the above.