JP3401460B2 - Tilt detection device, optical disk device, and tilt control method - 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 disc for recording information by irradiating an optical disc medium with a laser beam and an optical disc device thereof.

[0002]

2. Description of the Related Art In recent years, an optical disk device has been actively developed as a means for recording and reproducing a large amount of data, and an approach for achieving a higher recording density has been made. There is a phase change type optical disk device that utilizes reversible state change between crystal and non-crystal.

In a phase-change type optical disk device, a semiconductor laser is irradiated on the optical disk medium with two powers, a peak power for amorphizing a crystal part and a bias power for crystallizing an amorphous part, so that a mark is formed on the optical disk medium. (Amorphous part) and a space (crystal part) sandwiched between marks are formed.

There is a land / groove recording technique in which these marks and spaces are recorded on both the tracks of the land and groove of the guide groove on the disk.

In order to improve the reliability of the optical disc, it is necessary to record and reproduce a high quality signal on the optical disc.
If there is an inclination (tilt angle) of the recording surface of the optical disc with respect to the optical axis of the light beam, the light spot has aberration, and it is difficult to record and reproduce a high-quality signal on the optical disc.
Therefore, in order to record and reproduce signals on the optical disc,
It is necessary to accurately detect the tilt angle and correct the tilt angle.

FIG. 2 shows a conventional method for correcting the tilt position.

In FIG. 2, reference numeral 201 denotes an optical disk, 20
2 is an optical head for converging a light beam on an optical disk, 2
Reference numeral 03 is a tilt base, 204 is an arithmetic circuit, 205 is a focus control unit that controls the focal position of the light spot on the optical disc surface, 206 is a tracking control unit that controls the position of the light spot on the track, and 207 is the light beam. A tilt sensor for irradiating the optical disc with light for detecting the inclination of the recording surface of the optical disc with respect to the optical axis, receiving the light reflected by the optical disc, and detecting the inclination of the recording surface of the optical disc with respect to the optical axis of the light beam; Reference numeral 208 denotes a tilt control unit as means for controlling the tilt of the recording surface of the optical disc with respect to the optical axis of the light beam by tilting the tilt table based on the detection value of the tilt sensor.

FIG. 3 is a graph when the tilt position is interpolated between the inner circumference and the outer circumference of the optical disk in the conventional optical disk device.

[0009]

However, in the conventional configuration, since the tilt sensor and the tilt control unit as shown in FIG. 2 are used to detect the tilt position of the optical disk, the optical axis of the light beam with respect to the optical axis is detected. When correcting the inclination of the recording surface of the optical disc, a tilt sensor 207 for tilt detection is required in addition to the optical head 202. The two optical systems of the optical head and the tilt sensor complicate the optical disc device, increase the scale of the device implementation, and increase the cost. In addition, the optical axis must be adjusted for the two optical systems of the optical head and the tilt sensor, which complicates the adjustment work and causes the tilt (tilt angle) of the recording surface of the optical disc with respect to the optical axis of the light beam. However, it is difficult to accurately detect the tilt angle because an error occurs between the tilt sensor and the tilt sensor.

The present invention solves all of the above-mentioned problems, and the light beam is emitted at each of the inner, middle, and outer radial positions of the optical disc so that the detection value of the tilt detection means becomes an appropriate value. The objective is to correct the tilt of the optical disc with respect to the optical axis and improve the quality of the light spot and the recording / reproducing characteristics.

[0011]

In order to solve the above problems, the present invention has the following aspects.

The first aspect is as follows.

A track continuously formed in a concentric circle shape or a spiral shape, and a first track which is provided on the track at regular intervals and is deviated from the center of the track to the first side and the second side of the track, respectively. It has a shift pit and a second shift pit, and the first shift pit is
Repeatedly and continuously provided, and then the second shift pick
A tilt detecting device for detecting the tilt of a recording surface of an optical disc, which is repeatedly provided in succession , wherein an optical head for recording and reproducing a signal by applying a light spot with a narrowed light beam to the optical disc, The reflected light from the optical disc is divided into two along the line in the track direction.
A two-division photodetector that receives light by a light receiving element, and tracking control means that controls the position of the light spot on a track,
Off-track detection means for generating an off-track detection signal generated from a reproduction signal reproduced from the first shift pit and the second shift pit by the optical head, and two-split light detection of reflected light from the first shift pit Received by the vessel, the first,
The first sum signal, which is the sum of the outputs from the second light receiving element, and the reflected light from the second shift pit are received by the two-split photodetector, and is the sum of the outputs from the first and second light receiving elements. A first comparison signal that compares the lower absolute values of the envelope signals of the first sum signal and the second sum signal using the second sum signal, and an envelope signal of the first sum signal and the second sum signal. A second comparison signal for comparing the levels having higher absolute values of
In addition to having tilt detecting means for detecting the tilt of the recording surface of the optical disc using any one of the third comparison signals for comparing the amplitudes of the first sum signal and the second sum signal,
The off-track detection means uses one of the two comparison signals, which are not used by the tilt detection means, among the first to third comparison signals, to determine the center of the track and the center of the light spot. The amount of deviation is detected and the tilt
The comparison signal used by the detection means is the first comparison signal,
The comparison signal used by the off-track detection means is the third comparison signal.
A tilt detection device, characterized in that it.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

The second aspect corresponds to the tracking control means and off-track detection in the embodiment.

In the tilt detecting device of the present invention, the tracking control means for controlling the position of the light spot on the track uses a push-pull signal from a continuous groove due to a difference output of each detector of the two-division photodetector, The output of the off-track detection means is added to the tracking control means.

[0022]

[0023]

The third aspect corresponds to the case where the shift pit spacing is small (FIG. 8).

In the optical disc used in the tilt detecting device of the third aspect, the space Ls, which is the interval at which the first shift pits are repeated, is Lp <Ls <2Lp when the pit length is Lp. And

The fourth viewpoint is as follows.

A track continuously formed in a concentric circle shape or a spiral shape, and a first track provided on the track at regular intervals and offset from the center of the track to the first side and the second side of the track, respectively. It has a shift pit and a second shift pit, and the first shift pit is
Repeatedly and continuously provided, and then the second shift pick
Is an optical disc device that detects and corrects the inclination of the recording surface of an optical disc that is repeatedly and continuously provided .
Apply a light spot with a narrowed light beam to the optical disc,
An optical head for recording / reproducing signals, a two-division photodetector for receiving reflected light from the optical disc by first and second light receiving elements divided in two along a line in the track direction, and the optical spot. Tracking control means for controlling the position on a track; off-track detection means for generating an off-track detection signal generated from a reproduction signal for reproducing the first shift pit and the second shift pit by the optical head; and the tracking control. Means for detecting the reflected light from the first shift pit by the two-division photodetector, with the light spot positioned at the center of the track by the means and the off-track detection means, and outputs from the first and second light receiving elements. The first sum signal, which is the sum of the two, and the reflected light from the second shift pit
The level of the lower absolute value of the envelope signal of the first sum signal and the second sum signal is obtained by using the second sum signal , which is the sum of the outputs from the first and second light receiving elements, received by the split photodetector. A first comparison signal that compares the two signals, a second comparison signal that compares the levels of the higher absolute values of the envelope signals of the first sum signal and the second sum signal, and a second comparison signal that compares the first sum signal and the second sum signal. Tilt detecting means for detecting the inclination of the recording surface of the optical disc by using one of the third comparison signals for comparing the amplitudes, and tilt for correcting the angle of the optical disc by the tilt amount detected by the tilt detecting means. In addition to the correction means, the off-track detection means uses one of the two comparison signals, which are not used by the tilt detection means, of the first to third comparison signals to detect the track. Center and light To detect the amount of deviation between the Tsu door of the center,
The comparison signal used by the tilt detection means is the first comparison signal.
And the comparison signal used by the off-track detection means is
The optical disk device is characterized in that it has three comparison signals .

A fifth aspect relates to the tilt detection position of the optical disk device, and is characterized in that the tilt detection value is detected by at least three radial positions of the inner circumference, middle circumference and outer circumference of the optical disk.

A sixth aspect is that in the optical disk device of the present invention, the tracking control means for controlling the position of the light spot on the track is a push-pull from a continuous groove due to a difference output of each of the two-split photodetectors. The output of the off-track detecting means is added to the tracking control means by using a signal.

The seventh viewpoint is as follows.

A track continuously formed in a concentric circle or spiral shape, and a first track provided at a constant interval on the track and offset from the center of the track to the first side and the second side of the track, respectively. have a shift pits and second shifted pits, said first shifted pits
Repeatedly and continuously provided, and then the second shift pick
Is a tilt detection method for detecting the tilt of the recording surface of an optical disc in which the optical disc is repeatedly provided continuously, and a reflected light from the optical disc in the track direction The first and second light receiving elements divided into two along the line receive light, and tracking control is performed to control the position of the light spot on the track.
An off-track detection signal generated from a reproduction signal obtained by reproducing the first shift pit and the second shift pit by the optical head is generated, and an optical spot is positioned at the center of the track by the tracking control and the off-track detection signal. In this state, the reflected light from the first shift pit is received and the first output is the sum of the outputs from the first and second light receiving elements.
The sum signal and the second sum signal, which is the sum of the outputs from the first and second light receiving elements that receive the reflected light from the second shift pit, are used to determine the absolute value of the first sum signal and the second sum signal. A first comparison signal for comparing the envelope signals with lower values, a second comparison signal for comparing the envelope signals with higher absolute values in the first sum signal and the second sum signal, and
The inclination of the recording surface of the optical disc is detected using any one of the third comparison signals for comparing the amplitudes of the sum signal and the second sum signal, and the off-track detection signal is the first, Of the second and third comparison signals, one of the remaining two comparison signals not used in the detection of the inclination of the disc recording surface is used to determine the deviation amount between the track center and the light spot center. In the tilt detecting method, the comparison signal detected and used for detecting the inclination of the disk recording surface is the first comparison signal, and the comparison signal used for the off-track detection signal is the third comparison signal.

An eighth aspect is the tilt detecting method of the present invention, wherein the tracking control is performed continuously.
Each of the two split photodetectors on a track
The push-pull signal which is the difference output of the signal obtained from
In addition, the off-track detection signal is added to the push-pull signal .

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Common matters in the embodiments and the reference examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of the optical disk device.

In FIG. 1, 101 is an optical disk and 10
2 is an optical head for converging a light beam on an optical disk, 1
00 is a four-division photodetector consisting of a, b, c, and d photodetectors, 103 is a tilt base, 104 is an arithmetic circuit, and 105
Is a focus control unit that controls the focal position of the light spot on the optical disc surface, 106 is a tracking control unit that controls the position of the light spot on the track, and 107 is for detecting the inclination of the recording surface of the optical disc with respect to the optical axis of the light beam. Further, a tilt detector for detecting the inclination of the recording surface of the optical disc from the output of the photodetector, 108 inclines the optical head from the detection value of the tilt detector, and records the optical disc on the optical axis of the light beam. A tilt correction unit that corrects the tilt of the surface. 110 is an off-track detector, 111
Is an off-track controller. The four-division photodetector can be regarded as a two-division photodetector divided into two parallel to the track direction, when a and d are regarded as one body and b and c are regarded as one body.

Next, the recording / reproducing operation will be described.

By the optical head 102, the optical disk 10
The light spot condensed on the first spot is the focus control unit 10
The optical spot is focused on the optical disc 101 by 5, and the optical spot is tracked by the tracking control unit 106 at a desired track position at a desired radial position on the optical disc 101. Data recorded on the optical disc is read by reproducing uneven pits on the optical disc or light and shade marks having different reflectances on the optical disc by the focused and tracked light spot.

The recording operation will be described with reference to FIG.

In the phase-change type optical disk device, a semiconductor laser is irradiated onto the optical disk medium with two powers, a peak power 401 for amorphizing the crystal part and a bias power 402 for crystallizing the amorphous part. Mark (amorphous part) 40
4 and a space 405 (crystal part) sandwiched between the marks.

Since the mark and the space have different reflectivities, at the time of reproducing, the difference in the reflectivities is used to read a signal recorded by using the reproducing power 403 which is lower than the peak power 401 and the bias power 402. .

Next, the tilt will be described with reference to FIG.

As shown in FIG. 5, the center of the optical disc 501,
A line connecting the light spots condensed on the optical disc 501 from the optical head 502 is called a radial direction 504, and a direction on the plane where the optical disc 501 is perpendicular to the radial direction 504 is called a tangential direction 505. The direction perpendicular to the plane on the optical disc 501 is called the z-axis direction 506.

The tilt is classified into a direction and a tilt in the radial direction orthogonal to the track and a tilt in the tangential direction parallel to the track.

Radial tilt (R tilt) with reference to FIG.
Will be described.

In FIG. 6, reference numeral 601 denotes an optical disk and 602.
Is an optical head, and 603 is a tilt base. The radial tilt (R tilt) includes a disc R tilt 604 caused by a warp of the disc, a surface wobbling caused by the rotation of the disc, and the optical disc 60 with respect to the optical axis of the light beam.
The tilt (tilt) of the recording surface of No. 1 is caused by the mounting error of the optical head and the tilt of the tilt base.
There is 05. Essentially, the disc R tilt and the drive R tilt are called R tilt without making a distinction.

The tangential tilt (T
The tilt will be described.

In FIG. 7, reference numeral 701 is an optical disk and 702.
Is an optical head, and 703 is a tilt base. The tangential tilt (T tilt) includes the disk T tilt 70 caused by disk rotation vibration, disk surface accuracy error, and the like.
4 and the tilt (tilt) of the recording surface of the optical disc 701 with respect to the optical axis of the light beam is caused by an error in mounting the optical head or the tilt of the tilt base.
There is. Essentially, the disc T tilt and the drive T tilt are called T tilt without distinguishing from each other.

Next, the method of detecting the R tilt will be described. Figure 1
The R tilt detection method in the tilt detection unit 107 of
There are the following: (1) The differential signal (push-pull) of the two-split photodetector that received the light diffracted by the guide groove formed in advance on the optical disk while the tracking was on, that is, the light beam was operating along the track. TE) voltage is detected to detect the R tilt. (2) In the tracking-off state, that is, when the light beam is operating while crossing the track, the differential signal of the two-division photodetector that receives the light diffracted by the guide groove formed in advance on the optical disc ( A method of detecting R tilt by detecting the amplitude of push-pull TE). (3) A method of detecting the R tilt by detecting the amplitude of the wobble signal of the guide groove formed while wobbling the optical disk in advance in the tracking on state. (4) The amplitude of the first half and the second half of the reproduction signal of the sum signal output of the 2-split photodetector when reproducing the continuous pits in the form of a bird's-eye mark that are pre-pitted on the optical disc in the tracking-on state. A method of detecting the R tilt by comparing the signal level (lower envelope) or the upper signal level (upper envelope). (5) The amplitude of the first half and the second half of the reproduced signal of the difference signal output of the two-division photodetector when the continuous pits in the shape of a bird's mark that are pre-pitted on the optical disc are reproduced in the tracking-on state, or the upper signal. A method of detecting the R tilt by comparing the levels (upper envelope) of. (6) Amplitudes of the first half and the second half of the reproduction signal of the sum signal output of the two-division photodetector when the isolated pits in the shape of a bird mark that are pre-pitted on the optical disc are reproduced in the tracking-on state or the lower side There is a method of detecting the R tilt by comparing the signal levels (lower envelope).

Among the above, (1), (3), (4),
With respect to the methods (5) and (6), the R tilt is detected in the tracking-on state. Even if the R tilt or the T tilt occurs, the off-track detection unit 11
0, it is possible to position the light spot at the center of the track by the off-track control unit 111. In particular,
Regarding (1), (3), and (5), first, the off-track detector 110 and the off-track controller 111 position the light spot at the center of the track. In that state, the light spot is divided into two by a line that passes through the center of the light spot (the center of the perfect circle portion) and is parallel to the track direction, and the light amount of each divided portion is examined. The case where the light amounts of the two divided portions are equal is the case where there is no R tilt, and the case where there is a difference is the case where there is R tilt. Of the above,
With respect to the methods (1), (3), (4), (5), and (6), the R tilt is detected in the tracking-on state. Even if the R tilt or the T tilt occurs, the off-track detector 110 and the off-track controller 1
With 11, it is possible to position the light spot at the center of the track. In particular, regarding (1), (3), and (5), first, the off-track detector 110 and the off-track controller 111 position the light spot at the center of the track. In that state, the light spot is divided into two by a line that passes through the center of the light spot (the center of the perfect circle portion) and is parallel to the track direction, and the light amount of each divided portion is examined.
The case where the light amounts of the two divided portions are equal is the case where there is no R tilt, and the case where there is a difference is the case where there is R tilt.

The following (1), (3), (4), (5),
In the description of the method (6), the off-track detector 1
10. It is assumed that the light spot is positioned at the center of the track by the off-track control unit 111. Details of the off-track detector 110 and the off-track controller 111 will be described later with reference to FIGS.
This will be described with reference to FIG. In the present invention, the method (4) is used as an embodiment, and the method (1) to
The methods (3), (5) and (6) will be described below as reference examples.

Reference Example 1 First, the voltage of the differential signal (Push-pull TE) of the two-divided photodetector that received the light diffracted by the light spot of (1) in the guide groove formed in advance on the optical disc was detected. A method of detecting the R tilt will be described as Reference Example 1.

FIG. 18 is a cross-sectional view of the guide groove on the optical disk and a push-pull TE signal waveform which is a reproduction signal showing a tracking error at that time. 1801 is a groove track and 1802 is a land track.

The example shown in FIG. 18 is in the state where the tracking-on control is performed and the off-track control is performed, that is, the light spot is controlled so as to operate along the center of the track. . The waveform diagram shown in FIG. 18 shows the difference signal output (push-pull TE signal) of the two-division photodetector during reproduction.

When the R tilt is 0 degrees, the push-pull TE signal is at the reference level of 1803. R tilt is +0.4
Then, the R tilt causes aberration in the light spot. At this time, a phase shift occurs in the push-pull TE signal, and an offset + G occurs in the reproduction signal of the push-pull TE signal from the reference level when the R tilt is 0 degree. R
When the tilt is −0.4 degrees, the R tilt causes aberration in the light spot. At this time, a phase shift occurs in the push-pull TE signal, and an offset -G occurs in the reproduction signal of the push-pull TE signal from the reference level when the R tilt is 0 degree. The offset G from the reference level of the push-pull TE signal is different when the R tilt is +0.4 degrees and when the R tilt is -0.4 degrees. The tilt detection unit holds the offset G as a detection value of the tilt detection unit.

The tilt controller corrects the tilt angle by regarding the tilt detection value as a tilt angle.

FIG. 11 shows a simulation result of the relationship between the amount of R tilt when the R tilt occurs as described above and the detection value G detected by the tilt detecting section. The optical conditions used in the simulation are wavelength 650 nm, NA
= 0.6, RIM intensity which is the light intensity of the normalized outer peripheral portion of the objective lens in the radial direction is 0.25, and tangential direction RIM intensity is 0.83. The spot is the result when the spot is tracked to the center of the track. When the R tilt is not generated in FIG. 11, the offset G of the push-pull TE signal is 0. When the R tilt occurs, the light spot has an aberration, and the diffracted light from the guide groove does not become a perfect circle, and a bump-shaped primary light spot is formed on the side of the light spot. When the R tilt angle is in the + direction (see FIG. 6), the + 1st-order light spot is generated on the right side of the perfect circle (see FIG. 18C), and the R tilt angle is
In the case of the − direction, the −first order light spot is generated on the left side of the perfect circle (see FIG. 18A). R tilt is +0.4
There is a difference between the output of the differential signal (push-pull TE signal) when the diffracted light from the guide groove is received by the two-division photodetector when the R tilt is −0.4 degrees. A plot of the offset G of the push-pull TE signal is shown in FIG.
It becomes a curve of 1.

The tilt detecting section detects the tilt angle by using the offset G of the push-pull TE signal as the tilt angle detection value.

For example, the offset G of the push-pull TE signal, which is the detection value detected by the tilt detection unit 107,
Is −0.08, from FIG. 11, the R tilt is +
Since it is 0.4 degrees, the tilt correction unit 108 transmits the tilt correction amount according to the detected value to the tilt control unit 109, and the tilt control unit 109 moves the tilt base 103 to thereby obtain the R tilt angle. To correct.

The present R tilt detection method can be carried out without being limited to the optical conditions used in the simulation.

The tilt detection value is 1 when the reflected light from the mirror portion returns to the 2-split photodetector by 100%.
Is standardized as.

Reference Example 2 Next, in the tracking-off state of (2), the differential signal (push-pull TE) of the two-split photodetector which received the light whose light spot was diffracted from the guide groove formed in advance on the optical disk. A method of detecting the R tilt by detecting the amplitude of) will be described as a reference example 2.

Here, since the tracking is off, the light spot operates so as to cross the track. FIG. 19 shows the layout of the guide grooves on the optical disk and the push-pull TE signal waveform at that time. 1901 is a light spot, 1902 is the center of the track which is the center of the guide groove,
Reference numeral 03 is a guide groove formed in advance on the optical disk.

This is an example of reproducing the difference signal output (in this case, the push-pull TE signal) of the two-division photodetector when tracking off.

When the R tilt is 0 °, the amplitude K of the push-pull TE signal is large. When R tilt is 0.4 degree, R
The tilt causes aberration in the light spot. At this time,
The amplitude K of the push-pull TE signal also decreases due to the influence of diffraction. When the R tilt is −0.4 degrees, aberration occurs in the light spot due to the R tilt. At this time, the amplitude K of the push-pull TE signal also decreases due to the influence of diffraction. The amplitude K of the push-pull TE signal when the R tilt is +0.4 degrees and when the R tilt is −0.4 degrees is different from the amplitude K when the R tilt is 0 degrees. The tilt detector holds the amplitude K of the push-pull TE signal as a detection value of the tilt detector.

The tilt controller corrects the tilt angle by regarding the tilt detection value as a tilt angle.

FIG. 12 shows a simulation result of the relationship between the amount of R tilt when the R tilt occurs as described above and the detection value K detected by the tilt detecting section. The optical conditions used in the simulation are wavelength 650 nm, NA
= 0.6, radial direction RIM intensity 0.25, tangential direction RIM intensity 0.83. In FIG. 12, when the R tilt does not occur, the amplitude K of the push-pull TE signal
Is 1.0. When the R tilt occurs, the light spot has aberration, and the diffracted light from the guide groove is detected as two-split light when the R tilt is ± 0.4 degrees and when the R tilt is ± 0 degrees. A difference occurs in the output of the differential signal (Push-pull TE signal) when light is received by the device. A plot of the amplitude K of the push-pull TE signal is the curve in FIG.

The tilt detecting section detects the tilt angle by using the amplitude K of the push-pull TE signal as the tilt angle detection value.

For example, the amplitude K of the push-pull TE signal, which is the detection value detected by the tilt detection unit 107, is 0.
In the case of 8, the R tilt is +0.4 degrees or −0.4 degrees from FIG.
Displays the tilt correction amount according to the detected value.
09, and the tilt control unit 109 moves the tilt base 103 to correct the R tilt angle.

The present R tilt detection method can be carried out without being limited to the optical conditions used in the simulation.

[0070]

Reference Example 3 Next, the differential signal of the two-division photodetector that received the light diffracted from the guide groove formed while the optical spot of (3) was meandering (wobbled) in advance on the optical disk. A method for detecting the R tilt by detecting the amplitude of the (wobble signal) will be described as Reference Example 3.

FIG. 20 shows the layout of the guide grooves on the optical disk and the push-pull TE signal waveform at that time. 2001 is a light spot, 2002 is a track center which is the center of the guide groove, and 2003 is a guide groove formed while wobbled in advance.

Here, since the tracking is on, the light spot is operating along the center of the track. FIG. 20 shows the difference signal output (wobble signal in this case) of the two-division photodetector during reproduction.

When the R tilt is 0 degrees, the amplitude H of the wobble signal is
Is the maximum. When the R tilt is 0.4 degree, aberration occurs in the light spot due to the R tilt. At this time, the amplitude H of the wobble signal also decreases due to the influence of diffraction. When the R tilt is −0.4 degrees, aberration occurs in the light spot due to the R tilt. At this time, the amplitude H of the wobble signal
Also, the amplitude decreases due to the influence of diffraction. The amplitude H of the wobble signal when the R tilt is +0.4 degrees and when the R tilt is −0.4 degrees is different from the amplitude H when the R tilt is 0 degrees.
The tilt detector holds the amplitude H of the wobble signal as a detection value of the tilt detector.

The tilt control section regards the tilt detection value as a tilt angle and corrects the tilt angle.

FIG. 13 shows a simulation result of the relationship between the amount of R tilt when the R tilt is generated as described above and the detection value H detected by the tilt detector. The optical conditions used in the simulation are wavelength 650 nm, NA
= 0.6, radial direction RIM intensity 0.25, tangential direction RIM intensity 0.83. The spot is the result when the spot is tracked to the center of the track. When R tilt is not generated in FIG. 13, the amplitude H of the wobble signal is 0.09. When the R tilt occurs, the light spot has aberration, and the diffracted light from the guide groove is detected as two-split light when the R tilt is ± 0.4 degrees and when the R tilt is ± 0 degrees. A difference occurs in the output (wobble signal) of the differential signal when light is received by the device. A plot of the amplitude H of the wobble signal is the curve in FIG.

The tilt detecting section detects the tilt angle by using the amplitude H of the wobble signal as a tilt angle detection value.

For example, the amplitude H of the wobble signal, which is the detection value detected by the tilt detection unit 107, is 0.083.
If R tilt is +0.4 degrees or −0.4 degrees from FIG. 13, the tilt correction unit 108
The tilt control unit 109 determines the tilt correction amount according to the detected value.
To the tilt table 10 by the tilt control unit 109.
R tilt angle is corrected by moving 3.

The R tilt detecting method is not limited to the optical conditions used in the simulation and can be implemented.

The tilt detection value is 1 when the reflected light from the mirror portion returns to the 2-split photodetector by 100%.
Is standardized as.

REFERENCE EXAMPLE 4 Next, there will be described 2 when reproducing the continuous pits in the form of a bird's eye mark which are pre-pitted in advance on the optical disc of (5).
A method of detecting the R tilt by comparing the amplitudes of the first half and the second half of the reproduced signal of the difference signal output of the split photodetector will be described as Reference Example 4.

FIG. 23 is a layout view of pits on the optical disk. Reference numeral 2301 is a groove track of a guide groove dug in a spiral shape for recording data, and 2302 is a land track sandwiched between the groove tracks. 23
Reference numeral 03 denotes a repeated pit row in the first half portion formed by wobbling from the center of the groove track to the outer peripheral side or the inner peripheral side, and 2304 denotes a row of the repeated pit row in the first half portion, and then from the center of the groove track. The repeated pit row in the first half is a repeated pit row in the latter half formed by wobbling at symmetrical positions with respect to the center of the track. Radial pit spacing of wobbled pit rows 1.19 μm, pit width 0.36 μm
m, pit depth λ / 6, pit length 0.462 μm, tangential direction pit interval 1.12 μm, repetitive pattern, swing width from track center to pit center is 0.
A pit wobbled on the outer or inner side of 3 μm.

The difference signal output of the 2-split photodetector when tracking is on will be described. Here, since the tracking is on, the light spot moves along the center of the track.

In FIG. 23, one of the two-division photodetectors is N1,
The other detector is N2. When reproducing continuous pits that are wobbled from the center of the track, one of the detectors is greatly modulated by the light diffracted by the pits, while the other one is less affected by the diffraction by the pits and has a light intensity. Little change. The difference signal output is the difference signal output N1-N2 of N1 and N2, which is N-.

FIG. 22 shows an example of reproducing the difference signal output of the 2-split photodetector.

When the replay signal waveform has an R tilt of 0 degrees, the amplitude I and J of the signal modulated by the pit train is I = when the repetitive pits in the first half and the repetitive pits in the latter half are reproduced. There is a relationship of J. When the R tilt is 0.4 degree, aberration occurs in the light spot due to the R tilt. At this time, the amplitude I of the difference signal output reproduced from the repeated pit train in the first half portion and the amplitude J of the difference signal output reproduced from the repeated pit train in the latter half portion are different. The tilt detector holds the amplitude difference I-J of the difference signal output between the first half and the second half as a detection value of the tilt detector. R tilt is −
When 0.4 degree occurs, aberration occurs in the light spot due to R tilt. At this time, the amplitude I of the difference signal output reproduced from the repeated pit train in the first half portion and the amplitude J of the difference signal output reproduced from the repeated pit train in the latter half portion are different. The tilt detection unit detects the amplitude difference I of the difference signal output between the first half and the second half.
Hold -J as the detection value of the tilt detection unit.

With respect to the amplitudes of the difference signal outputs of the first half and the second half, the DC value of the voltage is held by the sample hold circuit, and the holding value I of the difference signal output of the first half and the holding value of the difference signal output of the second half are held. The difference I−J of J is used as the tilt detection value, and the tilt control unit considers the tilt detection value as the tilt angle and corrects the tilt angle.

FIG. 15 shows a simulation result of the relationship between the amount of R tilt when the R tilt is generated as described above and the detection value IJ detected by the tilt detector.
The optical condition used in the simulation is a wavelength of 650 nm,
NA = 0.6, radial direction RIM intensity 0.25, and tangential direction RIM intensity 0.83. The spot is the result when the spot is tracked to the center of the track. When the R tilt is not generated in FIG. 15, the difference I-J in the amplitude of the difference signal output is zero. When the R tilt occurs, the light spot has an aberration, and a difference occurs between the amount of diffracted light from the repeated pits in the first half and the amount of diffracted light from the repeated pits in the latter half of the diffracted light from the pits. The curve of FIG. 15 is obtained by plotting the amplitude difference I-J of the amplitude I of the first-half difference signal output and the amplitude J of the second-half difference signal output.

The tilt detector detects the tilt angle by using the amplitude difference I-J of the difference signal output as the tilt angle detection value.

For example, the amplitude difference I-J of the difference signal output, which is the detection value detected by the tilt detector 107, is -0.
15, the R tilt is +0.4 degrees from FIG. 15, and therefore the tilt correction unit 108 transmits the tilt correction amount corresponding to the detected value to the tilt control unit 109, and the tilt control unit 109 causes the tilt correction unit 109 to perform tilt correction. , R tilt angle is corrected by moving the tilt base 103.

In the above case, a simulation result of the relationship between the amount of R tilt and the detection value IJ detected by the tilt detector in the state where the light spot is +0.02 μm off-track from the center of the track. Figure 16
Is. The optical condition used in the simulation is a wavelength of 65
0 nm, NA = 0.6, radial direction RIM intensity 0.2
5, the RIM intensity in the tangential direction is 0.83.
In FIG. 16, when the R tilt does not occur, the difference I-J in the amplitude of the difference signal output is zero. When the R tilt occurs, the light spot has an aberration, and a difference occurs between the amount of diffracted light from the repeated pits in the first half and the amount of diffracted light from the repeated pits in the latter half of the diffracted light from the pits. A plot of the amplitude difference I-J of the amplitude I of the first half difference signal output and the amplitude J of the second half difference signal output is the curve of FIG. 16. The curve of FIG. 16 is almost the same as the curve of FIG. This is because the tilt angle detection results are the same when the light spot is at the center of the track (FIG. 15) and when the light spot is at a position displaced by +0.02 μm from the center of the track (FIG. 16). Indicates.

The tilt detector detects the tilt angle by using the amplitude difference I-J of the difference signal output as the tilt angle detection value.

For example, the amplitude difference I-J of the difference signal output, which is the detection value detected by the tilt detector 107, is -0.
In the case of 09, since the R tilt is +0.4 degrees from FIG. 16, the tilt correction unit 108 transmits the tilt correction amount corresponding to the detected value to the tilt control unit 109, and the tilt control unit 109 causes the tilt correction unit 109 to perform tilt correction. , R tilt angle is corrected by moving the tilt base 103.

[0094]

Here, the amplitude difference of the difference signal output in the first half and the latter half of the repeated pit train has been described as the detection value of the tilt control section. However, as the tilt detection value, the amplitude difference I-J of the difference signal output.
Instead of, the upper signal level difference It-Jt of the difference signal output of the repeated pit train may be used.

The R tilt detecting method is not limited to the optical conditions used in the simulation and can be implemented.

The tilt detection value is 1 when the reflected light from the mirror portion returns to the 2-split photodetector by 100%.
Is standardized as.

Reference Example 5 Next, under the first half and the second half of the reproduction signal of the sum signal output of the two-division photodetector when reproducing the isolated pit of the mark mark which is pre-pitted in advance on the optical disk of (6) A method for detecting the R tilt by comparing the levels of the side signals will be described as Reference Example 5.

FIG. 9 is a layout diagram of pits of an optical disc having isolated pits and a reproduction signal waveform at that time. 901
Is a groove track of a guide groove dug in a spiral shape for recording data, and 902 is a land track sandwiched between the groove tracks. Numeral 903 denotes an isolated pit in the first half portion formed by wobbling from the center of the groove track to the outer peripheral side or the inner peripheral side,
The reference numeral 4 denotes an isolated pit in the latter half part formed by wobbling in a symmetrical position from the center of the groove track to the isolated pit in the first half part, following the isolated pit in the first half part. The wobbled pits have a radial pit spacing of 1.19 μm, a track-wise isolated pit spacing of 10 μm or more, an isolated pit width of 0.36 μm, a pit depth λ / 6, a pit length of 0.462 μm, and a pit from the center of the track. It is a pit wobbled to the center by 0.3 μm on the outer or inner circumference side. Here, the space Ls, which is the interval at which the shifted pits are repeated, satisfies 20Lp <Ls when the pit length is Lp.

The reproduced signal waveform is an example when the sum signal of the two-division photodetector is reproduced. Here, since the tracking is on, the light spot moves along the center of the track.

When the R tilt is 0 °, the reproduced signal waveform is such that when the isolated pits in the first half part are reproduced and when the isolated pits in the latter half part are reproduced, the lower levels E and F of the sum signal output modulated by the pits are reproduced. Has a relation of E = F. R tilt is +
When it occurs at 0.6 degrees, aberration occurs in the light spot due to R tilt. At this time, the lower level E of the sum signal output reproduced from the isolated pits in the first half and the lower level F of the sum signal output reproduced from the isolated pits in the latter half are different. The tilt detector holds the lower signal level difference E-F of the sum signal output of the first half and the latter half as a detection value of the tilt detector.

When the R tilt is -0.6 degrees, aberration occurs in the light spot due to the R tilt. At this time, the lower level E of the sum signal output reproduced from the isolated pits in the first half and the lower level F of the sum signal output reproduced from the isolated pits in the latter half are different. The tilt detector holds the lower signal level difference E-F of the sum signal output of the first half and the latter half as a detection value of the tilt detector.

With respect to the amplitudes of the sum signal outputs of the first half and the second half, the DC value of the voltage is held by the sample hold circuit, and the hold value E of the sum signal output of the first half and the hold value of the sum signal output of the second half The difference E−F of F is used as a tilt detection value, and the tilt control unit corrects the tilt angle by regarding the tilt detection value as a tilt angle.

FIG. 17 shows a simulation result of the relationship between the amount of R tilt when the R tilt occurs as described above and the detection value EF detected by the tilt detecting section.
The optical condition used in the simulation is a wavelength of 650 nm,
NA = 0.6, radial direction RIM intensity 0.25, and tangential direction RIM intensity 0.83. The spot is the result when the spot is tracked to the center of the track. When the R tilt is not generated in FIG. 17, the lower signal level difference EF of the sum signal output is 0. When the R tilt occurs, the light spot has an aberration, and a difference in the amount of diffracted light from the isolated pit in the first half of the diffracted light from the pit and the amount of diffracted light from the isolated pit in the latter half occurs. The curve of FIG. 17 is obtained by plotting the difference E-F between the lower signal level E of the sum signal output of the first half and the lower signal level F of the sum signal output of the latter half.

The tilt detecting section detects the tilt angle by using the lower signal level difference E-F of the sum signal output as the tilt angle detection value.

For example, the lower side signal level difference E− of the sum signal output, which is the detection value detected by the tilt detection unit 107,
When F is +0.06, from FIG. 17, the R tilt is +
Since it is 0.6 degrees, the tilt correction unit 108 transmits the tilt correction amount according to the detected value to the tilt control unit 109, and the tilt control unit 109 moves the tilt base 103 to thereby obtain the R tilt angle. To correct.

The present R tilt detection method can be carried out without being limited to the optical conditions used in the simulation.

The tilt detection value is 1 when the reflected light from the mirror portion returns to the 2-split photodetector by 100%.
Is standardized as.

The tilt value of the detection value thus detected by the tilt detecting section is calculated by the tilt correcting section, and the tilt control section moves the tilt base to eliminate the R tilt, thereby eliminating the signal quality of the recording / reproducing signal. Improve.

In order to detect the R tilt by the above methods (1), (3) to (6), it is necessary that the light spot scans the center of the track previously formed by the guide groove. desirable. The shift between the center of the track of the optical disk and the light spot is called off-track. When the off-track is 0, that is, when the light spot scans the center of the guide groove formed in advance on the optical disc, the above (1),
The R tilt can be detected more accurately when the R tilt is detected by the methods (3) to (6).

Embodiment Next, there will be described 2 when reproducing continuous pits in the form of a bird's eye mark which are pre-pitted in advance on the optical disc of (4).
A method of detecting the R tilt by comparing the levels of the lower signals of the first half and the second half of the reproduction signal of the sum signal output of the split photodetector will be described as an embodiment.

FIG. 8 is a layout view of pits on the optical disk. Reference numeral 801 denotes a groove track of a guide groove dug in a spiral shape for recording data, and 802 is a land track sandwiched between the groove tracks. 803
Is a repeated pit row in the first half portion formed by wobbling from the center of the groove track to the outer peripheral side or the inner peripheral side, and 804 is a row of pit rows repeated from the center of the groove track, following the repeated pit row in the first half portion. The repetitive pit row of the part is a repetitive pit row of the latter half part formed by wobbling at a symmetrical position with respect to the track center. Repeated pattern of radial pit spacing of wobbled pits 1.19 μm, pit width 0.36 μm, pit depth λ / 6, pit length 0.462 μm, tangential pit spacing 1.12 μm, from track center It is a pit wobbled to the center of the pit with a swing width of 0.3 μm on the outer or inner circumference side. The space Ls, which is the interval at which the shifted pits are repeated, is Lp <Ls <2 when the pit length is Lp.
Satisfies Lp.

FIG. 21 shows an example of reproducing the sum signal output of the two-division photodetector. Here, since the tracking is on, the light spot moves along the center of the track.

When the R tilt is 0 °, the reproduced signal waveform shows the lower level Ab of the sum signal output modulated by the pit train when the repeated pits in the first half and the repeated pits in the latter half are reproduced. Bb has a relationship of Ab = Bb. When the R tilt is 0.4 degree, aberration occurs in the light spot due to the R tilt. At this time, the lower level Ab of the sum signal output reproduced from the repeated pit train in the first half
And the lower level Bb of the sum signal output reproduced from the repeated pit train in the latter half is different. The tilt detector holds the lower signal level Ab-Bb of the sum signal output of the first half and the latter half as a detection value of the tilt detector.

When the R tilt is −0.4 degrees, aberration occurs in the light spot due to the R tilt. At this time, the lower level Ab of the sum signal output reproduced from the repeated pit train in the first half portion is different from the lower level Bb of the sum signal output reproduced from the repeated pit train in the latter half portion. The tilt detector is
The lower signal level Ab of the sum signal output of the first half and the latter half
-Bb is held as the detection value of the tilt detection unit.

With respect to the amplitudes of the sum signal output of the first half and the second half, the DC value of the voltage is held by the sample hold circuit, and the hold value Ab of the sum signal output of the first half and the hold value of the sum signal output of the second half The difference Ab-Bb of Bb is used as a tilt detection value, and the tilt control unit regards the tilt detection value as a tilt angle and corrects the tilt angle.

FIG. 14 shows a simulation result of the relationship between the amount of R tilt in the state where the R tilt occurs as described above and the detected value Ab-Bb detected by the tilt detecting section. The optical condition used in the simulation is a wavelength of 650n
m, NA = 0.6, radial direction RIM intensity 0.25,
The RIM intensity in the tangential direction is 0.83. The spot is the result when the spot is tracked to the center of the track. In FIG. 21, when R tilt is not generated, the difference Ab-Bb between the lower levels of the sum signal output is zero. When the R tilt occurs, the light spot has an aberration, and a difference occurs between the amount of diffracted light from the repeated pits in the first half and the amount of diffracted light from the repeated pits in the latter half of the diffracted light from the pits. The difference Ab-Bb between the lower level Ab of the sum signal output of the first half portion and the lower level Bb of the sum signal output of the latter half portion is plotted to be the curve of FIG.

The tilt detector is arranged to detect the lower signal level difference A
The tilt angle is detected using b-Bb as the tilt angle detection value.

For example, the lower signal level difference Ab of the sum signal output, which is the detection value detected by the tilt detection unit 107.
When −Bb is −0.06, the R tilt is +0.4 degrees from FIG. 14, so the tilt correction unit 108
The tilt control unit 109 determines the tilt correction amount according to the detected value.
To the tilt table 10 by the tilt control unit 109.
R tilt angle is corrected by moving 3.

Here, the difference between the lower signal level of the sum signal output in the first half and the latter half of the repeated pit train is described as the detection value of the tilt control section. However, the lower signal level difference Ab of the sum signal output is used as the tilt detection value. Instead of -Bb, the upper signal level difference At-Bt of the sum signal output of the repeated pit train may be used.

[0121]

As will be described later with reference to FIGS. 26 and 27, the difference between the sum signal of the repeated pit string in the first half and the sum signal of the repeated pit string in the latter half is also used in the off-track detection. As is clear from the above, since the sum signal fluctuates approximately in a sine wave curve, the value of the sum signal takes (i) the upper signal level and (ii) the lower signal level. And (iii) there are three ways of taking the amplitude of the sine wave curve. When performing the tilt detection method of (4), (i), (ii), (ii)
If any one of i) is adopted, any one of the other is adopted in the off-track detection. This avoids that the signal used for tilt detection and the signal used for off-track detection are exactly the same.

The R tilt detecting method is not limited to the optical conditions used in the simulation and can be implemented.

The tilt detection value is 1 when the reflected light from the mirror portion returns to the 2-split photodetector by 100%.
Is standardized as.

A method of correcting the off-track in the R tilt detecting method of (4) will be described below as an embodiment. Further, the following method for correcting off-track is not limited to the R tilt detection method in (4), but the above (1),
It can also be used as a method for correcting off-track in the R tilt detection method of (3) and (5).

The off-track is controlled by using a sum signal output of signals for reproducing a repetitive pit train formed by wobbled on an optical disk in advance with a light spot.

FIG. 24 is a pit layout on the optical disk. Reference numeral 2401 is a groove track of a guide groove dug in a spiral shape for recording data, and 2402 is a land track sandwiched between the groove tracks. 24
Reference numeral 03 indicates a repeating pit row in the first half portion formed by wobbling from the center of the groove track to the outer peripheral side or the inner peripheral side, and 2404 follows the repeating pit row in the front half portion, and then from the center of the groove track. The repeated pit row in the first half is a repeated pit row in the latter half formed by wobbling at symmetrical positions with respect to the center of the track. Radial pit spacing of wobbled pit rows 1.19 μm, pit width 0.36 μm
m, pit depth λ / 6, pit length 0.462 μm, tangential direction pit interval 1.12 μm, repetitive pattern, swing width from track center to pit center is 0.
A pit wobbled on the outer or inner side of 3 μm.

FIG. 25 shows an example of reproducing the sum signal output of the two-division photodetector.

When the reproduced signal waveform is off-track 0, the amplitudes L and M of the signal modulated by the pit train are L = M when the repeated pits in the first half are reproduced and when the repeated pits in the latter half are reproduced. Have a relationship. When the off-track is 0.02 μm, the off-track causes a light amount difference between the two detectors of the two-divided photodetector. At this time, the amplitude L of the sum signal output reproduced from the repeated pit train in the first half portion is different from the amplitude M of the sum signal output reproduced from the repeated pit train in the latter half portion. The amplitude of the sum signal output of the first half and the second half is
The DC value of the voltage is held, and the difference LM between the holding value L of the sum signal output of the first half and the holding value M of the sum signal output of the second half is set as the off-track detection value, and this detection value is regarded as the off-track position. To correct the off-track position. In this case, the off-track position can be corrected without depending on the tilt.

Next, based on the detection value detected by the tilt detecting section, R at different radial positions of the optical disk is detected.
A tilt correction method will be described with reference to FIG.

Since the R tilt is generated by the warp of the disk, the magnitude of the R tilt changes from the inner circumference to the outer circumference of the optical disk as shown by a curve 1001 in FIG.

In FIG. 10, 1001 is an actual tilt curve showing how the tilt (tilt) of the recording surface of the optical disc with respect to the optical axis of the light beam changes with the radial position of the optical disc, and 1002 is A tilt amount (or tilt angle) at a predetermined radial position on the inner circumference on the tilt curve 1001, 1003 indicates the tilt curve 10
01, tilt amount at a predetermined radial position in the middle circumference, 1004
Is a tilt amount at a predetermined radial position on the outer circumference on the tilt curve 1001.

Next, the tilt amount estimated from the detection value detected by the tilt detector will be described. 100
5 is a tilt amount estimated from a detection value detected at a predetermined radial position on the inner circumference of the optical disc by the tilt detection unit, and 1006 is detected at a predetermined radial position on the outer circumference of the optical disc by the tilt detection unit. The tilt amount estimated from the detected value 1007 is the tilt amount estimated from the detection value detected by the tilt detection unit at a predetermined radial position on the middle circumference of the optical disc, and 1008 is the estimation at the middle circumference. An interpolated curve 1008 is obtained by linearly interpolating the tilt amount 1007, the estimated tilt amount 1005 on the inner circumference and the estimated tilt amount 1006 on the outer circumference.

When the optical disk is tilted, the tilt amount differs between the inner circumference and the outer circumference. In order to detect the difference in the tilt amount depending on the radial position, the optical disc device of the present invention detects the tilt amounts at at least three radial positions of the inner circumference and the outer circumference of the optical disk and the middle circumference therebetween as shown in FIG. . The tilt amount at the radial position between the inner and inner radial positions where the tilt angle is detected is estimated from the tilt amount 1005 estimated from the detected value at the inner periphery and the tilt amount at the medium periphery. Curve 10 obtained by linearly interpolating the tilt amount 1007
The value on 08 is the estimated tilt amount at the desired radial position between the inner circumference and the middle circumference. The tilt amount at the radial position between the outer and middle radial positions where the tilt angle is detected is
Tilt amount 1006 estimated from the detection value at the outer circumference
And the tilt amount 100 estimated from the detected value in the middle lap.
The value on the curve 1008 obtained by linearly interpolating 7 is set as the estimated tilt amount at the desired radial position between the outer circumference and the middle circumference.

In this case, it is possible to correctly correct the tilt amount 1007 estimated at a predetermined radial position on the inner circumference of the optical disc and the tilt amount 1003 on the actual inner circumference of the optical disc, and compared with the conventional method. It is possible to accurately and accurately correct the tilt position at each radial position for optical discs having different tilt amounts on the inner and outer circumferences, and it is possible to significantly improve the signal quality during recording and reproduction of the optical disc.

Next, the operation of the tilt correction section 108 will be described. In FIG. 10, the tilt angle (R tilt) is 0 degree at the inner radial position. Alternatively, the tilt angle of the inner circumference is set to be relatively 0 degree. The tilt angle at the outer peripheral portion of the optical disc is larger than that at the inner peripheral portion due to the deflection of the disc. This flexure varies from disc to disc, and the characteristics of the magnitude of the tilt angle with respect to the radial position are different for each disc.

The radial position where the light spot is converged on the optical disk surface moves outward, and the tilt angle is detected by the tilt detecting unit at the middle or outer circumference, and the tilt angle in the interpolated tilt curve of 1008 is obtained. When the tilt angle at the inner circumference differs by more than a threshold value (for example, 0.4 degrees),
The tilt correction unit gives an instruction to move the tilt table 103 so that the tilt angle becomes 0 at the radial position where the tilt angle is the threshold value.

As a result, it is possible to reduce the tilt angle caused by the deflection of the disc, which occurs from the inner circumference to the outer circumference, by moving the tilt base, and to improve the signal quality during recording / reproduction of the optical disc. Is possible. Reference Example 6 Further, with respect to off-track detection and control, a method different from the off-track correction method described in the embodiment of the present invention will be described as Reference Example 6.

Referring to FIG. 26, 4 of the 4-division detector 100
The operation of the arithmetic circuit 104 which operates by receiving the outputs a, b, c, d from one light receiving element will be described. Arithmetic circuit 1
From 04, TE signal: (a + d)-(b + c), FE signal: (a + c)-(b + d), RF signal: (a + b + c + d), off-track detection signal (OF signal): diagonal sum signal (a + c), A diagonal sum signal (b + d) is generated.

The TE signal is supplied to the tracking controller 10
6 and is used to control the tracking position of the light spot on the track of the optical disc. The FE signal is sent to the focus control unit 105 and used to control the focus position of the light spot on the optical disc. R
For the F signal, the data recorded on the optical disk is read out and becomes a reproduction signal for data processing. Further, the RF signal is sent to the off-track detector 110 and used for off-track position detection. The off-track detection signal (OF signal) is sent to the off-track detector 110 and used for off-track position detection.

Next, the process in which the off-track detector 110 detects the off-track position from the off-track detection signal will be described.

The off-track position is detected by extracting the phase difference between the two sets of off-track detection signals.

Details of the phase difference signal will be described with reference to FIG.

Here, as shown in FIG. 27, a light spot 270.
When 1 is at the center of the track, the intensity of the diffracted light on the detector is as shown in FIG. 27B, so the phase difference between the diagonal sum signals (a + c) and (b + d) is 0. Even if the disc rotates and the relationship between the light spot and the pit advances as shown by the arrow, this value is always zero and does not change. 27A and 27B, the light spot is displaced from the track.
As shown in FIG. 27C, as the disc rotates, FIG.
When moving in the direction of the arrow, the diagonal sum signals are both of the output of the sine wave, they, RF signal (a + b + c
+ D) phase contrast, since the relationship between +90 degrees and -90 degrees, or the light spot by detecting the phase difference between the diagonal sum signal with respect to the RF signal is off track much from the center of the pit Can be detected.

Also in the off-track detection, the difference between the sum signal of the repeated pit train in the first half and the sum signal of the repeated pit train in the latter half is used. As described with reference to FIG. 21, since the diagonal sum signal changes approximately in a sine wave curve, the value of the diagonal sum signal is (i) when the upper signal level is taken, and (ii) When taking the lower signal level,
(Iii) There are three ways to take the amplitude of the sine wave curve.

FIG. 27D shows a waveform representing the relationship between the phase difference signal and off-track. In the figure, (Bsig) is the output point when the light spot passes through the center of the pit, (Asi
g) and (Csig) show output points when passing through the left and right sides of the pit, respectively. The off-track position from the center of the pit can be detected using this phase difference.

As shown in FIG. 28 (A), the uneven pre-pits 2805 previously recorded on the optical disk were swung by Wa (= Tp / 4) with respect to the center of the groove track of the guide groove across the track. The pits continuously arranged at the positions are referred to as the first half pre-pit row 2803, and the pit row continuously arranged at the position swung to the opposite side from the center of the groove track is referred to as the second half pre-pit row 2804. To do. Here, the swing width Wa of the first half pre-pit and the swing width Wb of the second half pre-pit are arranged equal (Wa = Wb). The pits arranged are consecutive pits of a single frequency.

[0148] Figure 28 (B) is a graph of the phase difference signal centered on a pit. When the light spot passes the center of the groove track of the first half pre-pit row, the output of the phase difference signal is Pa, and when the light spot passes the center of the groove track of the second half pre-pit row, the output of the phase difference signal is Pb. The result of calculating the sum of the output of the first half pre-pit row and the output of the second half repetitive pit row by the off-track detector is shown by holding the phase difference signal of the first half pre-pit row and the phase difference signal of the second half pre-pit row. 28 (C). This phase difference sum signal becomes 0 when the light spot passes through the center of the track.

The result of the computer simulation based on the above conditions will be described. The conditions used in the simulation are as follows. Laser wavelength (λ) 650 nm, objective lens NA 0.6, tangential RIM intensity 0.83, radial RIM intensity 0.25, disk track pitch 1.19 μm,
Pit depth λ / 6, pit width 0.36 μm, repeated pits have a line direction cycle of 1.12 μm, and pit length 0.46 μm.
It is a repeating wobble pit sequence of m.

FIG. 29 shows the characteristics when the R tilt occurs.

In FIG. 29, when the R tilt is given in the order of (a), (b), and (c) by -0.6 degrees, ± 0.0 degrees, and +0.6 degrees, the phase difference signal is divided into the first half wobble pits. The off-track detection signal calculated in the second half wobble pit is shown. The horizontal axis represents the off-track amount based on the track center. The vertical axis is the off-track detection signal. The case where the off-track detection signal is 0 is the track center. When there is no R tilt in the curve of (b), it can be seen from the graph that the off-track detection signal corresponding to the off-track amount is obtained. Further, when the off-track position is 0, the off-track detection signal is also 0.

Next, when R tilt occurs, for example, (a)
It is understood from the graph that the off-track detection signal corresponding to the off-track amount is obtained when the tilt angle is −0.6 degrees. Further, when the off-track position is 0, the off-track detection signal is also 0.

The same applies to the case of (c).

[0154] By reproducing this way the continuous pre-pits arranged on the phase difference signal and the wobble shape, it is possible to accurately detect the amount of off-track without influence on R tilt.

Therefore, the tracking accuracy is improved,
It is possible to improve the signal quality of the signal recorded on the adjacent track, except for the influence of cross erasing that erases the adjacent track during recording.

[0156]

As described above, according to the optical disc apparatus and the tilt control method for an optical disc of the present invention, an optical system for detecting a tilt angle is not required in addition to an optical system for recording / reproducing signals, and the optical disc is recorded in advance. groove tracks being, with repetition row of pits is formed by shifting the center to the outer circumferential side or the inner circumferential side from the center of the land track and the groove track, detecting a tracking signal and a tilt angle, the tilt correction portion, tilt By correcting the tilt angle using the control unit, it is possible to improve the signal quality during recording and reproduction. As a result, it is not necessary to separately provide a tilt detector, and it is possible to reduce the implementation scale of the device and reduce the cost.

As in the tilt detection method shown in FIG. 10, the tilt amount at the desired radial position of the optical disc is estimated from at least three detection values of the inner circumference, the middle circumference, and the outer circumference,
It is possible to remarkably improve the recording / reproducing characteristics without deteriorating the signal quality at the time of recording / reproducing.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a conventional optical disc device.

FIG. 3 is a diagram showing a conventional tilt correction method for an optical disc.

Figure of order to you explain the recording and reproduction of the optical disk device in an embodiment of the present invention; FIG

FIG. 5 is a configuration diagram showing a relationship between an optical disc and an optical disc device according to an embodiment of the present invention.

FIG. 6 is a diagram for explaining R tilt of the present invention.

FIG. 7 is a diagram for explaining T tilt of the present invention.

FIG. 8 is an enlarged view of the pit arrangement on the optical disc.

FIG. 9 is a waveform diagram and a pit arrangement diagram of the optical disc in the case of Reference Example 5 of the present invention.

FIG. 10 is a graph showing the relationship between the radial position and R tilt according to the embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the R tilt and the push-pull TE signal in the case of Reference Example 1 of the present invention.

FIG. 12 is a graph showing the relationship between R tilt and push-pull TE signal amplitude in the case of Reference Example 2 of the present invention.

FIG. 13 is a graph showing the relationship between R tilt and wobble signal amplitude in the case of Reference Example 3 of the present invention.

FIG. 14 is a graph showing the relationship between the R tilt and the sum signal lower side signal level difference of a repeating continuous pit row in the case of the embodiment of the present invention.

FIG. 15 is a graph showing the relationship between the R tilt and the difference signal amplitude difference between repetitive continuous pit rows in the case of Reference Example 4 of the present invention.

FIG. 16 is a graph showing the relationship between the R tilt in the case of off-track and the difference signal amplitude difference between repetitive continuous pit rows in the case of Reference Example 4 of the present invention.

FIG. 17 is a graph showing the relationship between the R tilt and the signal level difference of the sum signal lower side of the isolated pit in the case of Reference Example 5 of the present invention.

FIG. 18 is a diagram for explaining the relationship between the R tilt and push-pull TE signal in the case of Reference Example 1 of the present invention.

FIG. 19 is a diagram for explaining the relationship between R tilt and push-pull TE signal amplitude in the case of Reference Example 2 of the present invention.

FIG. 20 is a diagram for explaining the relationship between R tilt and wobble signal amplitude in the case of Reference Example 3 of the present invention.

FIG. 21 is a diagram for explaining the relationship between the R tilt and the sum signal output of the repetitive continuous pit row in the case of the embodiment of the present invention.

FIG. 22 is a diagram for explaining the relationship between the R tilt and the difference signal output of a repeating continuous pit row in the case of Reference Example 4 of the present invention.

FIG. 23 is a diagram for explaining a pit arrangement diagram of an optical disc and difference signal output.

FIG. 24 is an enlarged view of the pit arrangement on the optical disc.

FIG. 25 is a diagram for explaining the relationship between the off-track and the sum signal output of the repeating continuous pit row in the case of the embodiment of the present invention.

FIG. 26 is a diagram for explaining an off-track detection method according to Reference Example 6 of the present invention.

FIG. 27 is a diagram for explaining a phase difference signal in Reference Example 6 of the present invention.

FIG. 28 is a diagram for explaining an off-track detection method in Reference Example 6 of the present invention.

FIG. 29 is a diagram showing a simulation result of an off-track error with respect to R tilt in Reference Example 6 of the present invention.

[Explanation of symbols]

100 4-division photodetector 101 Optical disc 102 Optical head 103 Tilt base 104 Arithmetic circuit 105 Focus control unit 106 Tracking control unit 107 Tilt detection unit 108 Tilt correction unit 109 Tilt control unit 110 Off-track detection unit 111 Off-track control unit 803 First half Repeating pit row 804 Second half repeating pit row 903 First half isolated pit 904 Second half isolated pit

Front page continuation (72) Inventor Takashi Ishida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-59-38939 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G11B 7/095

Claims (8)

(57) [Claims] 1. A track which is continuously formed in a concentric circle or spiral shape, and which are provided on the track at regular intervals and are deviated from the center of the track to the first side and the second side of the track, respectively. An inclination of a recording surface of an optical disc having a first shift pit and a second shift pit, the first shift pit being repeatedly provided continuously, and the second shift pit being repeatedly provided continuously, A tilt detecting device for detecting, wherein a light spot obtained by narrowing a light beam is applied to the optical disc,
An optical head for recording / reproducing a signal, a two-split photodetector for receiving reflected light from the optical disc by first and second light receiving elements split in two along a line in the track direction, and the optical spot Tracking control means for position control on a track; off-track detection means for generating an off-track detection signal generated from a reproduction signal obtained by reproducing the first shift pit and the second shift pit by the optical head; and the tracking control Means for detecting the reflected light from the first shift pit by the two-division photodetector, with the light spot positioned at the center of the track by the means and the off-track detection means, and outputs from the first and second light receiving elements. And a reflected light from the second shift pit is received by a two-split photodetector, and a second sum signal is a sum of outputs from the first and second light receiving elements. Using the door, the first sum signal and the lower envelope signal of the absolute value of the second sum signal (A
b, Bb) , a first comparison signal, and a second comparison signal, which compares the envelope signals (At, Bt) having higher absolute values in the first sum signal and the second sum signal with each other;
Tilt detection means for detecting the tilt of the recording surface of the optical disc using any one of the third comparison signals for comparing the respective amplitudes (C, D) of the sum signal and the second sum signal. The off-track detection means uses one of the remaining two comparison signals not used by the tilt detection means among the first, second, and third comparison signals to determine the center of the track. The amount of deviation of the light spot from the center is detected, and the comparison signal used by the tilt detection means is the first comparison signal, and the comparison signal used by the off-track detection means is the third comparison signal. Detection device. 2. The off-track detection means uses the push-pull signal which is a difference output of signals obtained from the respective detectors of the two-division photodetector on the continuously formed tracks. The tilt detection device according to claim 1, wherein the output of the above is added to the tracking control means. 3. The space Ls, which is the interval at which the first shift pits are repeated, has a pit length of Lp,
The tilt detection device according to claim 1, wherein Lp <Ls <2Lp. 4. A track continuously formed in a concentric circle or spiral shape, and provided on the track at regular intervals, and formed by being shifted from the center of the track to the first side and the second side of the track, respectively. An inclination of a recording surface of an optical disc having a first shift pit and a second shift pit, the first shift pit being repeatedly provided continuously, and the second shift pit being repeatedly provided continuously, An optical disc device for detecting and correcting, wherein a light spot obtained by narrowing a light beam is applied to the optical disc,
An optical head for recording / reproducing a signal, a two-split photodetector for receiving reflected light from the optical disc by first and second light receiving elements split in two along a line in the track direction, and the optical spot Tracking control means for position control on a track; off-track detection means for generating an off-track detection signal generated from a reproduction signal obtained by reproducing the first shift pit and the second shift pit by the optical head; Means for detecting the reflected light from the first shift pit by the two-division photodetector, with the light spot positioned at the center of the track by the means and the off-track detection means, and outputs from the first and second light receiving elements. And a reflected light from the second shift pit is received by a two-split photodetector, and a second sum is a sum of outputs from the first and second light receiving elements. Signal and the envelope signal of the lower absolute value of the first sum signal and the second sum signal (A
b, Bb) , a first comparison signal, and a second comparison signal, which compares the envelope signals (At, Bt) having higher absolute values in the first sum signal and the second sum signal with each other;
Tilt detection means for detecting the tilt of the recording surface of the optical disc using any one of the third comparison signals for comparing the respective amplitudes (C, D) of the sum signal and the second sum signal. The off-track detecting means uses one of the remaining two comparison signals not used by the tilt detecting means among the first, second, and third comparison signals to determine the center of the track. An optical disc characterized in that the comparison signal used by the tilt detection means is the first comparison signal and the comparison signal used by the off-track detection means is the third comparison signal by detecting the deviation amount of the light spot from the center. apparatus. 5. The tilt detecting means, at least at three radial positions of an inner circumference, a middle circumference and an outer circumference of the optical disc,
The optical disk device according to claim 4, wherein the inclination of the recording surface is detected. 6. The off-track detection means uses the push-pull signal which is a difference output of signals obtained from the respective detectors of the two-division photodetector on the continuously formed tracks. The optical disc device according to claim 4, wherein the output of the above is added to the tracking control means. 7. A track formed continuously in a concentric circle or spiral shape, and provided on the track at regular intervals, and formed by being shifted from the center of the track to the first side and the second side of the track, respectively. An inclination of a recording surface of an optical disc having a first shift pit and a second shift pit, the first shift pit being repeatedly provided continuously, and the second shift pit being repeatedly provided continuously, A tilt detecting method for detecting, wherein a light spot obtained by narrowing a light beam is applied to the optical disc, and reflected light from the optical disc is received by first and second light receiving elements divided into two along a line in a track direction. Then, tracking control for controlling the position of the light spot on the track is performed, and the first shift pit and the second shift pit are reproduced by the optical head. An off-track detection signal generated from the signal is generated, and the reflected light from the first shift pit is received by the tracking control and the off-track detection signal while the light spot is located at the center of the track. 1st and 1st sum signal which is the sum of the output from 2nd light sensing element,
The reflected light from the second shift pit is received and a second sum signal which is the sum of the outputs from the first and second light receiving elements is used,
A first comparison signal for comparing the envelope signals (Ab, Bb) having a lower absolute value in the first sum signal and the second sum signal, and the envelope having a higher absolute value in the first sum signal and the second sum signal. Second comparing signals (At, Bt)
Amplitude of each of the comparison signal, the first sum signal, and the second sum signal
The inclination of the recording surface of the optical disc is detected by using one of the third comparison signals for comparing (C, D), and the off-track detection signal is the first, second, and third comparison signals. Among the signals, one of the remaining two comparison signals not used for detecting the inclination of the disc recording surface is used to detect the deviation amount between the center of the track and the center of the optical spot, and the disc recording is performed. A tilt detecting method, wherein the comparison signal used for detecting the inclination of the surface is the first comparison signal, and the comparison signal used for the off-track detection signal is the third comparison signal. 8. The tracking control uses a push-pull signal which is a difference output of signals obtained from respective detectors of the two-division photodetector on the continuously formed track, and the off-track detection signal is detected. 8. The tilt detecting method according to claim 7, wherein the tilt detecting method is added to the push-pull signal.