JP2003257060A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of stably detecting a servo area mark to an optical disk of which the servo area has a specific length in the radial direction. <P>SOLUTION: The optical disk drive is provided with a time measuring circuit 4 for detecting a time in which a light spot passes through at least a part of the servo area in the circumferential direction, a timing generator 5 for detecting timing of appearance of a servo area wobble mark based on the detected time, and a tracking error detector 7 for detecting a tracking error signal based on the reproduction signal at the timing of the detected wobble mark. Thus, the drive can easily detect the timing of the wobble mark appearance, and can also detect the tracking error signal irrespective of the revolving speed and the radial position of the optical disk. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording information on an optical disk or reproducing recorded information,
In particular, the present invention relates to detection of a mark in a servo area when an optical disk having a format in which servo areas are provided radially from the center of rotation and the length of the servo area is constant.

[0002]

2. Description of the Related Art Conventionally, as an optical disk device using a disk in which clock marks are preliminarily recorded in a radial pattern from the center of the disk, a constant angular velocity (CAV) method in which the disk is rotated at a constant rotational speed has been the mainstream. On the other hand, the MCAV system, which is advantageous in terms of capacity, and an optical disk device in which a disk is rotated at a substantially constant linear velocity (MCLV) as described in Japanese Patent Application Laid-Open No. 7-114775 have also been used.

In any method, a clock mark is detected, a signal synchronized with a servo clock is generated by a PLL circuit, and an address code and a wobble mark are detected based on the servo clock signal. .

FIG. 8 is a block diagram showing an example of a tracking error signal generating circuit of an optical disk device. 1 in the figure
Is a reproduced analog signal reproduced from the optical disk, and 13 is a clock detection circuit for detecting a clock signal from the reproduced analog signal. The clock detection circuit includes a circuit for binarizing the reproduced signal. 15 is a phase comparison circuit, 1
6 is a loop filter, 17 is a VCO (voltage controlled oscillator), and 18 is a 1 / N frequency divider.

Further, 5 is a timing generator for generating wobble timing, 6 is an AD converter for A / D converting the reproduced analog signal with the timing signal from the timing generator 5, and 7 is two wobble detection of the AD converter. It is a track error detector that detects a tracking error signal from a signal. A tracking control circuit (not shown) performs tracking control using the detected tracking error signal.

FIG. 9A is a diagram showing an example of a pattern of servo segments on an optical disk. Numerical values of 1, 2, 3, ... In FIG. 9A indicate one unit of the servo clock. In the example of FIG. 9A, there are 256 servo clocks from the servo clock mark to the next servo clock mark. T indicated by a broken line in the drawing is the track center, and the access code mark and the servo clock mark are located at the track center. The wobble mark is located between the tracks. The signal shown in FIG. 9B is a reproduced signal waveform when a light spot scans an arbitrary track.

In the example of FIG. 9A, since there are 256 servo clocks from the servo clock mark to the next mark,
If 256 is set as N of the 1 / N frequency divider 18 in FIG.
Since the output of CO17 is the servo clock itself,
By counting this, the access code mark,
You can see the position of wobble marks.

That is, assuming that the position where the servo clock mark is in FIG. 9A is "23" in the servo clock, the first group of access codes is between "7" and "9",
It can be seen that the second group is between "14" and "15" and the wobble marks are at "19" and "27". At this time, at the timing of the wobble marks of "19" and "27" generated by the timing generator 5, the reproduced analog signal is digitized by the AD converter 6 and sampled at "27" from the value sampled at "19". By subtracting the value, the tracking error signal can be detected.

As described above, in the conventional sample servo system, since marks such as clock marks are radially recorded from the center of the optical disk, each mark can be extracted if there is a clock synchronized with the servo clock. There was an advantage. However, in the conventional sample servo system, since the area occupied by the mark increases toward the outer circumference of the optical disk, the area occupied by the mark cannot be ignored in response to the recent demand for higher linear recording density.

Therefore, in order to solve such a drawback,
As shown in FIG. 10, a format is conceivable in which the length of the servo area occupied by the sample servo marks is constant in the inner and outer circumferences. FIG. 10 shows the relationship between the clock mark and the wobble mark. The physical lengths a and b from each clock mark to the wobble mark are constant values regardless of the radial position of the optical disk, but the lengths c and d from the clock mark to the clock mark are different lengths.

Since only the clock marks are arranged radially from the center of the optical disk like the clock marks of a general sample servo, it is possible to create a clock synchronized with the clock marks. By arranging the marks of the sample servo in this way, the area of the data area can be increased and the recording capacity of the optical disk can be increased.

[0012]

However, as shown in FIG.
When an optical disc having a format in which the servo area has a constant length is used, the timing of marks such as wobble marks in the servo area varies in the radial direction when the optical disc is rotated at a constant rotation speed. for that reason,
Especially when the servo is turned on for the first time, or after seeking, before the track position is known, the timing for detecting the wobble mark and the timing for determining the address are not known, so it is necessary to add new information to an optical disc with a constant servo area length. A method of detecting the mark in the servo area was needed.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to easily wobble regardless of the radial position of an optical disc when an optical disc having a constant servo area length is used. An object is to provide an optical disk device capable of detecting the timing of marks and the like.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to intermittently perform servo control on an optical disk radially arranged from the center and having a servo area having a constant circumferential length by using wobble marks in the servo area. An optical disc device for recording information or reproducing recorded information while performing the operation, comprising means for detecting a time during which a light spot passes in at least a part of a servo area in a circumferential direction, and servo based on the detected time. An optical disc comprising: means for detecting a wobble mark appearance timing in the area; and means for detecting a servo signal corresponding to the wobble mark based on a reproduction signal level at the detected wobble mark appearance timing. Achieved by the device.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a first embodiment of the optical disk device of the present invention. In FIG. 1, reference numeral 101 denotes an optical disc which is an information recording medium, and is referred to as an optical disc including a phase change optical recording medium, a magneto-optical recording medium, a write-once type optical recording medium and the like. The optical disc 101 is an optical disc having a format similar to that of FIG. 10, and servo regions are provided in advance radially from the center of rotation, and servo regions having a constant length are provided in the circumferential direction regardless of the inner circumference and the outer circumference. The optical disc 101 is driven by the MCLV method. That is, the optical disc 101 is divided into a plurality of zones in the radial direction, the rotation speed is constant in the same zone, and the linear velocity is approximately constant between all the zones.

Reference numeral 102 records information on the optical disc 101,
It is an optical pickup for reproduction, and has a recording / reproducing laser light source (not shown) inside, an objective lens for converging a light beam from the laser light source on the optical disc, an optical sensor for detecting reflected light from the optical disc, an objective lens for tracking direction and It includes a tracking actuator and a focus actuator that are driven in the focus direction. A magnetic head 111 applies a modulation magnetic field to the optical disc 101 during recording.

Further, 103 is a spindle motor for rotating the optical disc 101, and 104 is an optical pickup 10.
A reproduction signal detection circuit for detecting a reproduction analog signal from the light reception signal of the optical sensor in the reference numeral 2, 105 is a reproduction circuit which performs signal processing such as demodulation processing using the reproduction signal of the reproduction signal detection circuit 104 during reproduction to generate reproduction data. Circuit. Also, 1
Reference numeral 06 is a recording circuit that modulates recording data at the time of recording information to generate a recording signal, and 107 is a magnetic head drive circuit that drives the magnetic head 111 according to the recording signal from the recording circuit 106.

Further, reference numeral 108 is a tracking error signal generating circuit for generating a tracking error signal from the reproduced analog signal from the reproduced signal detecting circuit 104. The configuration and operation of this tracking error signal generation circuit will be described later in detail. The tracking error signal is sent to the servo control circuit 109 to be subjected to phase compensation processing and the like, and then is supplied to the actuator driver 110. The actuator driver 110 drives the tracking actuator in the optical pickup 102, so that the optical pickup 102 outputs the tracking error signal. Tracking control is performed so that the light spots of 1) follow the tracks on the optical disk. Actually, a circuit for detecting a focus error signal, a circuit for performing focus control, and the like are provided, and the focus control is performed so that the light spot focuses on the information surface of the optical disc.

At the time of recording information, the optical disk 10 is used.
Information is recorded by applying a recording modulation magnetic field from the magnetic head 111 while irradiating the recording light beam from the optical pickup 102 to the optical disc 1. When reproducing information, the optical pickup 102 irradiates the optical disc 101 with a reproduction light beam, and the reflected light from the optical disc 101 is detected by an optical sensor in the optical pickup 102. The reproduction signal detection circuit 104 detects a reproduction analog signal from the detection signal of the optical sensor, and the reproduction circuit 105 reproduces the recorded information by performing predetermined signal processing using the reproduction analog signal. Although FIG. 1 shows an optical disk device of the magnetic field modulation system, the present invention is not limited to this, and can be used for a device of the optical modulation system or the like.

FIG. 2 is a block diagram showing an example of the tracking error signal generation circuit 108 of FIG. In the figure, 1 is a reproduced analog signal reproduced from the optical disc 101, 2 is a groove end detection circuit for detecting the end of a groove (track for recording information) of the optical disc 101, and 3 is a groove start for detecting the start of the groove. It is a part detection circuit. Further, 4 is a time measuring circuit for measuring the time between the detected start and end of the groove, 5 is a timing generator for generating the timing signal of each mark such as a wobble mark in the servo area, and 6 is a reproducing circuit. An AD converter for A / D converting the analog signal 1 with a timing signal from the timing generator 5, and a track error detector 7 for detecting a tracking error signal from the output signal of the AD converter 6.

FIG. 3A is a diagram showing an example of an optical disk having grooves (tracks for recording information) other than the sample servo area used in this embodiment. The grooves before the numeral 0 and after the numeral 25 shown in FIG. 3A are the groove portions. A mirror portion is provided between the groove portions, and a servo area is provided in the mirror portion.

Here, the numerical value "0" is the end of the groove, "2".
5 "is the start end of the groove. The end of the groove is 0 and is" 4 ".
From "12" to the access code mark indicating the access code, the position "17" is the first wobble mark, the position "21" is the second wobble mark,
"25" is the groove start end. The numerical value in FIG. 3A represents the distance from the groove end portion, and one unit is 0.2 μm. That is, it indicates that the groove start end is at a position 5 μm away from the groove end.

Such a servo area is used for the optical pickup 1
When the light beam emitted from 02 scans in the circumferential direction, a signal waveform as shown in FIG. 3B is obtained.

The groove end detection circuit 2 receives the reproduced analog signal 1 as described above and detects the groove end timing. Similarly, when the reproduced analog signal 1 is input, the groove start edge detection circuit 3 detects the groove start edge timing. These can be detected by comparing the reproduced analog signal 1 with a predetermined level and binarizing it.

The time measuring circuit 4 measures the time interval between the two points of the groove end and the groove start detected by the groove end detection circuit 2 and the groove start end detection circuit 3, and outputs it to the timing generator 5. The timing generator 5 determines the access code mark position and the wobble mark position from the groove end timing and the time interval, and the AD converter 6 uses the timing of these two positions as the conversion timing of the reproduced analog signal.

That is, as shown in FIG. 3, the access code mark position and the first and second wobble mark positions in the servo area are known in advance, and the timing generator 5
Detects the appearance timing of the access code mark and the first and second wobble marks based on the groove end timing and the time between the groove start end and the groove end. The AD converter 6 is the first
And the level of the reproduced analog signal is AD-converted at the timing at which the second wobble mark appears. The track error detector 7 generates a tracking error signal by subtracting the AD conversion value of the reproduced analog signal at the two wobble expression timings, and outputs the tracking error signal to the servo control circuit 109. The servo control circuit 109 intermittently performs tracking control of the light spot using the generated tracking error signal.

FIG. 4 is a block diagram showing a concrete example of the time measuring circuit 4 and the timing generator 5. In FIG. 4, the time measuring circuit 4 includes a voltage holding circuit 8 and a ramp waveform generating circuit 1.
0 (the output of the ramp waveform generation circuit is shared by the time measurement circuit and the timing generator), the voltage holding circuit 8 receives the groove start edge detection signal from the groove edge detection circuit 3, and the ramp waveform generation circuit 10 receives the groove edge. The groove end detection signals from the end detection circuit 2 are supplied. The ramp waveform generation circuit 10 is reset by the groove end detection signal and outputs a voltage signal that rises with a predetermined time constant. The voltage holding circuit 8 holds the voltage signal value of the ramp waveform generating circuit 10 at the groove start timing until the next groove start timing.

The timing generation circuit 5 comprises a ramp waveform generation circuit 10, a level conversion circuit 11 and a comparison circuit 12. The level conversion circuit 11 converts the voltage signal value output from the time measurement circuit 4 by a predetermined calculation. , To the comparison circuit 12. That is, the voltage signal value of the time measuring circuit 4 corresponds to the time from the groove end to the groove start end, that is, the time of 25 units, and the level conversion circuit 11 determines each servo area based on the signal value expressed in 25 units. Each mark is converted into a signal value corresponding to the timing of each mark.

For example, when the timing of the first wobble mark is created, as shown in FIG. 3, the first wobble mark is at the position of 17 units, so the level conversion circuit 11 sets the voltage signal value of the time measurement circuit 4 to 17 units. / 25 times the voltage signal,
When the timing of the second wobble mark is created, the second
21/25 because the wobble mark is at the position of 21 units
The converted voltage signals are converted and output to the comparison circuit 12. Similarly, the voltage signal of the access code mark is also converted. For example, the mark at the position of 4 units is a voltage signal of 4/25 times, and the mark at the position of 11 units is a signal of 11/25 times. Conversion is performed and output to the comparison circuit 12.

The voltage signal of the level conversion circuit 11 is compared with the ramp waveform signal of the ramp waveform generation circuit 10 in the comparison circuit 12, and the timing signal is output from the comparison circuit 12 based on the comparison result. That is, the ramp waveform signal of the ramp waveform generating circuit 10 is 17/2 of the voltage signal value of the voltage holding circuit 8.
The timing signal corresponding to the first wobble mark is output when the number becomes 5 times, and the timing signal corresponding to the second wobble mark when the time becomes 21/25 times.
Is output from.

Similarly, the ramp waveform signal of the ramp waveform generating circuit 10 is 4/25 times the voltage signal value of the voltage holding circuit 8,
5/25 times, 6/25 times, 11/25 times, 12/25
The timing signals corresponding to the respective access code marks are output from the comparison circuit 12 when the number of signals becomes 13 times or 13 times, respectively. Here, since the unit number of the servo area does not change regardless of the number of rotations of the optical disc 101, the level conversion circuit 11 calculates the mark position with respect to the voltage signal of the time measurement circuit 4 and uses it for the address code. The calculation is performed 5 times and twice for the wobble mark.

When the result of the time measuring circuit 4 is known, since all the mark positions have already passed,
This value is used only when the next groove end comes.
There are 1280 sample servo areas in one round of the disk. For example, if the optical disk rotates at 1800 rpm, the interval is about 26 μS, and the rotation speed does not suddenly change in this short time. There is no problem even if you use a previous value that does not occur. Further, in order to prevent malfunction due to noise or the like, the time of the average value of several times may be used as the result of the time measuring circuit.

Further, in FIG. 4, it is also possible to use a counter which is reset at the groove end portion instead of the ramp waveform generating circuit 10 and to form a digital circuit for counting 1 from the groove end portion for each clock. The clock frequency is
For example, the frequency is set to 45 MHz, but an appropriate frequency with which resolution can be obtained may be used. In this case, the time measuring circuit 4 receives the groove start signal and the counter value of the ramp waveform generating circuit (referred to as a counter), holds the counter value of the ramp waveform generating circuit (counter) at the groove starting end until the next timing, The level conversion circuit 11 converts the counter value output from the time measurement circuit 4 by a predetermined calculation, and the comparison circuit 12
And input.

The output count value of the time measuring circuit 4 represents the time from the groove end to the groove start, that is, 25 units of time, as in the case of the analog circuit.
For example, when creating the timing of the first wobble mark, the level conversion circuit 11 increases the output count value of the time measuring circuit 4 by 17/25 times, and when creating the timing of the second wobble mark, the count value of the time measuring circuit 4. 21
/ 25 times, and the obtained conversion value is output to the comparison circuit 12. Similarly, the level conversion circuit 11 calculates the comparison count value of the access code mark and outputs it to the comparison circuit 12.

For example, assuming that the optical disc is rotated at 1800 rpm at a radius of about 20 mm, the time from the end of the groove of 5 μm to the start of the groove is about 2 μS, and it is about 90 when counted with a clock of 45 MHz. The count value of one wobble mark is 90 × 17/25, which is 61 counts. Even if digitized in this way, the tracking error signal can be detected as in the above description. Also, the timing of the access code can be detected.

In this embodiment, since the sampling points are discrete due to the digitization, sample values before and after the clock at the fetch timing may be averaged. For example, in the case of the first wobble mark, since the take-in timing is 61, the average value of the AD conversion results of the three counts 60 to 62 is set. Of course, each sampling value may be weighted and averaged. In this case, the AD conversion clock needs to be the same as the counter clock of the ramp waveform generation circuit 10. That is,
In this case, it becomes 45 MHz.

Also in this case, the number of units in the servo area does not change regardless of the number of rotations of the optical disk 101.
The level conversion circuit 1 for the count value of the time measurement circuit 4
1 is the same as the calculation of the position of the mark. In this embodiment, all the circuits can be configured by digital circuits, and therefore, there is an advantage that they can be easily integrated into an IC.

FIG. 5A is a diagram showing another example of the format of the optical disc 101 used in this embodiment. Also in the optical disc of this format, the length of the servo area is constant regardless of the radial direction. In FIG. 5 (a), a point having a numerical value of 0 is a clock mark, plus 4 to 12 from the clock mark are access code marks, 17 is a first wobble mark, and 21 is a position. Is the second wobble mark. The numerical value represents the distance from the clock mark, and one unit is 0.2 μm. That is, it indicates that the second wobble mark is at a position 4.2 μm away from the center of the clock mark.
FIG. 5B is a reproduction signal waveform when a light beam is scanned on an arbitrary track of the optical disc of FIG.

In the case of the optical disc format of FIG. 5A, a clock mark detecting circuit for detecting a clock mark is used instead of the groove end detecting circuit 2 of FIG. 2, and a second wobble is used instead of the groove start detecting circuit 3. Second to detect the mark
By using the wobble mark detection circuit, it is possible to generate a timing signal corresponding to each mark with the same circuit configuration as that shown in FIG. However, the voltage signal value of the time measuring circuit 4 corresponds to 21 units of time from the clock mark to the second wobble mark, and the level converting circuit 11 converts the voltage signal value of the time measuring circuit 4 in accordance with this format. It is necessary.

Specifically, since the first wobble mark is at the position of 17 units, the level conversion circuit 11 multiplies the voltage signal value (21 units) of the time measurement circuit 4 by 17/21, and the second wobble mark is 21 units. Since it is at the position, the voltage signals are respectively converted to 21.21 times the voltage signals and output to the comparison circuit 12.
The comparison circuit 12 compares the converted value of the level conversion circuit 11 with the ramp waveform signal of the ramp waveform generator 10, and the ramp waveform signal of the ramp waveform generator 10 becomes 17/21 times the voltage signal of the time measurement circuit 4. The timing signal corresponding to the first wobble mark when
Timing signals corresponding to the wobble marks are output respectively.

Further, the timing signals corresponding to the other access code marks and the like are similarly output. Therefore, it is possible to output the timing signal corresponding to each mark exactly as in the case of the optical disc of FIG. Of course, the AD converter 6 AD-converts the reproduced analog signal at the timing of appearance of the first wobble mark and the second wobble mark, and the track error detector 7 detects the tracking error signal by calculating the difference. Is.

In the case of the optical disk of FIG. 5, the time measuring circuit 4 measures the time from the clock mark to the second wobble mark, but even in the case of the optical disk of the format of FIG. The time from the groove end portion to the second wobble mark may be measured instead of the portion.
Naturally, since the measurement time of the time measurement circuit is different, the level conversion circuit 11 performs the conversion operation accordingly.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of a tracking error signal generation circuit used in the second embodiment of the optical disc apparatus of the present invention. The overall configuration of the optical disc device is the same as that shown in FIG. In the figure, 1 is a reproduced analog signal reproduced from the optical disc 101, and 13 is a clock detection circuit for detecting a clock mark from the reproduced analog signal. A circuit for binarizing the reproduction signal is included in this circuit.

Further, 14 is a second wobble detection circuit for detecting the second wobble mark in the servo area, 4 is a time measurement circuit for measuring the time from the clock mark to the second wobble mark in the servo area, and 5 is a clock detection circuit. Circuit 13,
A timing generator that generates a timing signal corresponding to each mark based on the output signal of the time measuring circuit 4, 6 is an AD converter that performs A / D conversion of the reproduced analog signal with the timing signal of the timing generator 5, and 7 is an AD It is a track error detector that detects a tracking error signal from the AD conversion value of the reproduced analog signal from the converter.

FIG. 7A is a diagram showing an example of the format of the optical disc 101 used in this embodiment. Figure 7
In (a), the position where the numerical value is 0 is the clock mark, and the position where it is plus 4 from the clock mark is the second position.
The first wobble mark is located at -4 from the wobble mark and the clock mark, and the access code mark is located at -16 to -8. The numerical value represents the distance from the clock mark, and one unit is 0.2 μm. In other words, the second wobble mark is from the center of the clock mark,
It is shown that they are located at a distance of 0.8 μm.

Although not shown in FIG. 7, there are 1280 clock marks per disk rotation, and the same number of sample servo areas exist. 7 (b) is shown in FIG.
This is a reproduction signal when a light beam scans an arbitrary track in (a).

Next, the operation of this embodiment will be described. First, when the light beam scans the servo area in the circumferential direction, the reproduced analog signal 1 from the reproduced signal detection circuit 104 is detected.
Is supplied to the clock detection circuit 13, and the clock mark included in the reproduced analog signal is detected by the clock detection circuit 13.
Detected in.

Further, the second wobble detection circuit 14 detects the second wobble mark included in the reproduced analog signal, similarly to the clock mark detection circuit 13. The timings of the marks respectively detected by the clock detection circuit 13 and the second wobble detection circuit 14 are input to the time measurement circuit 4, and the time measurement circuit 4 measures the time from the clock mark to the second wobble mark. In this way, by measuring the time from the clock mark to the second wobble mark, the time corresponding to 4 units from the clock mark to the second wobble mark can be measured, and the time per unit can be known.

The time measuring circuit 4 transmits the time for one unit to the timing generator 5, and the time for one unit is known, so that the positions of the first and second wobble marks are fixed. Therefore, the timing generator 5 outputs a conversion command to the AD converter 6 at a fixed timing. The AD converter 6 converts the value of the reproduced analog signal into digital data with the timing signal from the timing generator 5. The track error detector 7 calculates the difference between the data converted by the AD converter 6 and detects the tracking error signal. The servo control circuit 109 intermittently performs tracking control using the tracking error signal detected in the same manner.
The timing generator 5 also outputs a timing signal of the access code.

Next, as the time measuring circuit 4 and the timing generator 5, the circuit shown in FIG. 4 can be used. In this case, the time measuring circuit 4 is composed of the voltage holding circuit 8 and the ramp waveform generating circuit 10 (the output of the ramp waveform generating circuit is shared by the time measuring circuit and the timing generator). The timing of the second wobble mark is input to the voltage holding circuit 8 in the time measuring circuit 4, and the timing of the clock mark is input to the ramp waveform generating circuit 10. Ramp waveform generation circuit 1
0 is reset at the timing of the clock mark and outputs a voltage signal that rises with a predetermined time constant. The voltage holding circuit 8 holds the voltage signal value of the ramp waveform generation circuit 10 at the timing of the second wobble mark until the timing of the next second wobble mark.

The timing generator 5 comprises a ramp waveform generating circuit 10, a level converting circuit 11 and a comparing circuit 12. The level converting circuit 11 performs a predetermined calculation based on the voltage signal value output from the voltage holding circuit 8. Done, comparison circuit 1
Output to 2. The voltage signal value of the voltage holding circuit 8 is the time from the clock mark to the second wobble mark, that is, 4
Equivalent to a unit of time. For example, when creating the timing of the first wobble mark, the level conversion circuit 11 subtracts 4 units of voltage signal value from the voltage signal value immediately before being reset by the clock mark of the ramp waveform generation circuit 10. The value is output to the comparison circuit 12. Further, when creating the timing of the second wobble mark, the level conversion circuit 11 adds the voltage signal value of 4 units to the voltage signal value when the ramp waveform generation circuit 10 is reset and compares the voltage signal value with the comparison circuit. Output to 12.

The comparing circuit 12 compares the voltage signal value from the level converting circuit 11 with the ramp waveform signal of the ramp waveform generating circuit 10, and the ramp waveform signal of the ramp waveform generating circuit 10 is the ramp waveform generating circuit as described above. The timing signal corresponding to the first wobble mark is output when the voltage signal value obtained by subtracting the voltage signal value of 4 units from the voltage signal value immediately before being reset by the clock mark 10 is reached. Further, the ramp waveform signal of the ramp waveform generating circuit 10 has a voltage signal value of 4 when the ramp waveform generating circuit 10 is reset.
When the voltage signal value obtained by adding the voltage signal values for the unit is reached, the timing signal corresponding to the second wobble mark is output.

Similarly, the level conversion circuit 11 also calculates the comparison voltage signal value for the access code mark. For example, the mark at the position of -16 units has a voltage value four times that of 4 units and the position of -15 units. The mark in 4 is 3.
The ramp waveform generating circuit 1 is calculated by multiplying by 75 times.
A value obtained by subtracting a voltage signal value 4 times 4 units and a voltage signal value 3.75 times 4 units from the voltage signal value immediately before 0 is output to the comparison circuit 12. Similarly, the comparison circuit 12 compares the signal value from the level conversion circuit 11 with the ramp waveform signal of the ramp waveform generation circuit 10,
A timing signal corresponding to each access code mark is output.

Also in this embodiment, the optical disc 101 is used.
Since the unit number does not change irrespective of the number of revolutions, the level conversion circuit 11 calculates the mark position with respect to the voltage signal value of the time measurement circuit 4, and outputs a timing signal corresponding to each mark.

Here, in FIG. 4, a counter which is reset by a clock mark instead of the ramp waveform generating circuit and receives a predetermined clock as an input can be digitized as in the first embodiment. The difference from the first embodiment is that the points for measuring the time do not have to be at both ends of the sample servo area. This embodiment has an advantage that the format of the sample servo is not limited.

As the measurement interval of the time measuring circuit,
It is not limited to the distance from the clock mark, but any distance between two detectable points with a fixed distance may be used. For example, the time between the first wobble mark and the clock mark may be measured.

Further, in the case of the format of FIG. 3, it is possible to select the first wobble mark or the like from the groove end for time measurement. Further, when there is a clock mark at a predetermined position in the sample servo area in the format of FIG. 3, the time between the groove end and the clock mark is measured, or the track address is indicated in the servo area in the format of FIG. Even when the access code mark is at a predetermined position, it is needless to say that the time between the groove end and the access code mark may be measured in the same manner, and the expression timing of each mark can be detected based on the measured time.

[0059]

As described above, according to the present invention, when an optical disc having a format in which the length of the servo area is a fixed length is used, the wobble mark expression timing can be easily detected. The tracking error signal can be detected regardless of the number and the radial position, and the servo control can be performed without any trouble while increasing the recording capacity of the optical disc.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing in detail the tracking error signal generation circuit of FIG.

FIG. 3 is a diagram showing an example of a sample servo format of an optical disc used in the apparatus of FIG.

FIG. 4 is a block diagram showing in detail the time measuring circuit and timing generator of FIG.

5 is a diagram showing another example of the sample servo format of the optical disc used in the embodiment of FIG.

FIG. 6 is a block diagram showing a tracking error signal generation circuit used in the second embodiment of the present invention.

FIG. 7 is a diagram showing an example of a sample servo format of an optical disc used in the second embodiment.

FIG. 8 is a block diagram showing a conventional tracking error signal generation circuit.

FIG. 9 is a diagram showing an example of a sample servo format of an optical disc.

FIG. 10 is a diagram showing an example of a sample servo format in which the length of a servo area is constant on the inner circumference and the outer circumference.

[Explanation of symbols]

1 Playback analog signal 2 groove end detection circuit 3 Groove start detection circuit 4 hours measuring circuit 5 Timing generator 6 AD converter 7 Track error detector 8 Voltage holding circuit 10 Ramp waveform generation circuit 11 Level conversion circuit 12 Comparator 13 Clock detection circuit 14 Second wobble detection circuit 101 optical disc 102 optical pickup 103 spindle motor 104 reproduction signal detection circuit 105 playback circuit 106 recording circuit 107 magnetic head drive circuit 108 tracking error signal generation circuit 109 Servo control circuit 110 actuator driver 111 magnetic head

Claims (7)

[Claims] 1. Information is recorded or recorded on an optical disk having a servo area radially arranged from the center and having a constant length in the circumferential direction while intermittently performing tracking control using wobble marks in the servo area. An optical disc device for reproducing the data, a means for detecting a time for a light spot to pass through at least a part of the servo area in the circumferential direction, and a timing for generating a wobble mark in the servo area based on the detected time. An optical disc apparatus comprising: a means and a means for detecting a tracking error signal corresponding to the wobble mark based on a reproduction signal level at the detected wobble mark appearance timing. 2. The optical disk device according to claim 1, wherein the optical disk is rotated by an MCLV system. 3. The servo area is provided in a mirror portion sandwiched between groove portions where information is recorded, and the time detecting means has a passage time with reference to end portions of the groove portions located before and after the mirror portion. 3. The optical disk device according to claim 1, wherein 4. A clock mark whose arrangement position in the servo area is fixed is provided in the servo area,
3. The optical disk device according to claim 1, wherein the time detection unit detects the passage time based on one of the end portions of the groove and the clock mark. 5. An access code mark whose arrangement position in the area is fixed is provided in the servo area, and the time detecting means passes through one of the ends of the groove and the access code mark as a reference. The optical disk device according to claim 1, wherein time is detected. 6. The reproduction signal is sampled at a predetermined frequency, and the tracking error signal detecting means selects the tracking error signal by selecting one of the sampled reproduction signals that corresponds to the wobble mark expression timing. The optical disk device according to any one of claims 1 to 5, wherein the optical disk device is detected. 7. The tracking error signal detecting means detects the tracking error signal by taking an average value of sample values of the reproduction signal at several points in the vicinity of the wobble mark appearance timing. The optical disk device according to any one of 1 to 5.