JP2001312833A - Tilt detector, optical disk device and tilt control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for correcting tilt of an optical head by detecting the tilt as an inclination of an optical disk, since this inclination sometimes occurs depending on the setting of the optical head while the optical disk is desirably to receive the optical beam of the optical head perpendicularly. SOLUTION: In a tracking-on state with a position controlled on a track using a push/pull signal that is the differential signal of a bisected photodetector; the bisected photodetector receives a reflected light beam from a first shift pit preliminarily formed on the optical disk, in which case the first differential signal is the difference of outputs from the first and second light receiving elements; the bisected photodetector receives a reflected light beam from a second shift pit following the first shift pit, in which case the second differential signal is the difference of outputs from the first and second light receiving elements; and, by making a comparison between the first and second differential signals, the tilt is detected on the recording face of the optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk for recording information by irradiating an optical disk medium with laser light, and an optical disk device for the same.

[0002]

2. Description of the Related Art In recent years, optical disk apparatuses have been actively developed as means for recording and reproducing large-capacity data, and approaches for achieving higher recording densities have been made. There is a phase-change type optical disk device using a reversible state change between a crystal and an amorphous.

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

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

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

FIG. 2 shows a conventional tilt position correcting method.

In FIG. 2, reference numeral 201 denotes an optical disk;
2 is an optical head for condensing a light beam on an optical disk, 2
03 is a tilt table, 204 is an arithmetic circuit, 205 is a focus control unit that controls the focus position of the light spot on the optical disk surface, 206 is a tracking control unit that controls the position of the light spot on the track, and 207 is the light of the light beam. The optical disk is irradiated with light for detecting the inclination of the recording surface of the optical disk with respect to the axis, and the light reflected by the optical disk is received.
A tilt sensor 208 for detecting the tilt of the recording surface of the optical disk with respect to the optical axis of the light beam, based on the detected value of the tilt sensor, tilts the tilt table to determine the tilt of the recording surface of the optical disk with respect to the optical axis of the light beam. It is a tilt control unit as a means for controlling.

FIG. 3 is a graph showing a case where a tilt position is interpolated on the inner and outer circumferences of an optical disk in a conventional optical disk device.

[0009]

However, in the conventional configuration, a tilt sensor and a tilt control unit as shown in FIG. 2 are used to detect the tilt position of the optical disk. When correcting the tilt of the recording surface of the optical disk, a tilt sensor 207 for tilt detection is required separately from the optical head 202. The two optical systems of the optical head and the tilt sensor complicate the optical disk device, increase the implementation scale of the device, 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 operation, and the inclination (tilt angle) of the recording surface of the optical disc with respect to the optical axis of the light beam and the tilt angle. Therefore, an error occurs between the tilt sensor and the tilt sensor, and it is difficult to accurately detect the tilt angle.

The present invention solves all of the above-mentioned problems. In order to make the detection value of the tilt detection means an appropriate value, the light beam is emitted at each of the inner, middle and outer radial positions of the optical disk. An object of the present invention is to correct the tilt of an optical disk with respect to the optical axis and improve the quality of a light spot and the recording / reproducing characteristics.

[0011]

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

The first aspect is as follows.

A track formed continuously in a concentric circle or spiral shape and a first track formed at regular intervals on the track and shifted from the center of the track to the first side and the second side of the track, respectively. What is claimed is: 1. A tilt detecting device for detecting an inclination of a recording surface of an optical disc having shift pits and second shift pits, wherein an optical head for recording and reproducing a signal by irradiating a light spot with a light beam focused on the optical disc; A two-divided photodetector that receives reflected light from an optical disk along first and second light-receiving elements divided into two along a track direction line, and a push-pull that is a difference signal between the light spot and the two-divided photodetector Tracking control means for controlling a position on a track by using a signal; and first and second light receiving elements, wherein reflected light from the first shift pit is received by a two-divided photodetector. And a fourth sum signal which is a sum of outputs from the first and second light receiving elements. Off-track detecting means for outputting an offset amount that is a shift amount between the center of the track and the center of the light spot by comparing the output of the off-track detecting means to the tracking control means,
In a state where the light spot is located at the center of the track, the reflected light from the first shift pit is received by a two-segment photodetector, and a first difference signal which is a difference between outputs from the first and second light receiving elements. And the reflected light from the second shift pit is received by a two-segment photodetector, and is compared with a second difference signal, which is a difference between outputs from the first and second light receiving elements, to thereby obtain a recording surface of the optical disk. A tilt detecting device comprising a tilt detecting means for detecting a tilt.

The second aspect particularly corresponds to the upper signal level shown in FIG.

In the tilt detecting device according to a first aspect, the tilt detecting means includes a level having a higher absolute value of an envelope of the first difference signal and a level having a higher absolute value of an envelope of the second difference signal. And comparing with.

The third aspect particularly corresponds to the amplitude shown in FIG.

In the tilt detecting device according to the first aspect, the tilt detecting means compares the amplitude of the first difference signal with the amplitude of the second difference signal.

The fourth aspect corresponds to the interval between shift pits.

In the optical disc used in the tilt detecting device according to the present invention, the first shift pit is provided repeatedly and continuously, and subsequently, the second shift pit is provided repeatedly and continuously.

The fifth aspect corresponds to the case where the interval between shift pits is small (FIG. 8).

In the optical disc used in the tilt detecting device according to a fifth aspect, the space Ls, which is the interval at which the first shift pit is repeated, satisfies Lp <Ls <2Lp when the pit length is Lp. And

The sixth viewpoint is as follows.

A track formed continuously in a concentric circle or spiral shape, and a first track formed at regular intervals on the track and shifted from the center of the track to the first side and the second side of the track, respectively. An optical disk device for detecting and correcting the inclination of a recording surface of an optical disk having shift pits and second shift pits, wherein an optical head for recording and reproducing a signal by irradiating a light spot with a narrowed light beam on the optical disk, The first and second divided light beams from the optical disc are divided into two parts along a line in the track direction.
A two-segment detector for receiving light by a light-receiving element, tracking control means for controlling the position of the light spot on a track using a push-pull signal which is a difference signal between the two-segment photodetectors, the first shift pit and the second shift An off-track detecting means for generating an off-track detecting signal generated from a reproduced signal of a pit reproduced by the optical head, and an output of the off-track detecting means are added to the tracking control means, so that a light spot is located at the center of the track. In this state, the reflected light from the first shift pit is received by a two-segment photodetector, and a first difference signal, which is a difference between the outputs from the first and second light receiving elements, and the second shift pit. Of the recording surface of the optical disk by detecting the reflected light of the optical disc by a two-segment photodetector and comparing the reflected light with a second difference signal which is a difference between outputs from the first and second light receiving elements. A tilt detection unit that is an optical disk apparatus characterized by having a tilt correction means for correcting the angle of the optical disk by the tilt amount detected by the tilt detecting means.

The seventh aspect is as follows.

A track formed continuously in a concentric circle or spiral shape and a first track formed at regular intervals on the track and shifted from the center of the track to the first side and the second side of the track, respectively. A tilt detection method for detecting an inclination of a recording surface of an optical disk having a shift pit and a second shift pit, wherein a light spot where a light beam is narrowed is applied to the optical disk, and reflected light from the optical disk is emitted in a track direction. The first and second light receiving elements divided into two along the line receive light, and perform tracking control for controlling the position of the light spot on a track using a push-pull signal that is a difference signal of a two-part light detector, 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; The output of the off-track detection signal is added to the signal for performing the switching control, and while the light spot is located at the center of the track, the reflected light from the first shift pit is received. An optical disc by receiving a reflected light from the second shift pit and a second difference signal as a difference between outputs from the first and second light receiving elements. The tilt detection method is characterized by detecting the inclination of the recording surface of the tilt angle.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The common features of the embodiments of the present invention and reference examples will be described below with reference to the drawings.

FIG. 1 shows a configuration diagram of an optical disk device.

In FIG. 1, reference numeral 101 denotes an optical disk,
2 is an optical head for condensing a light beam on an optical disk, 1
00 is a quadrant photodetector composed of photodetectors a, b, c and d, 103 is a tilt table, 104 is an arithmetic circuit, 105
Is a focus control unit for controlling the focus position of the light spot on the optical disk surface, 106 is a tracking control unit for controlling the position of the light spot on the track, and 107 is for detecting the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam. A tilt detector for detecting the tilt of the recording surface of the optical disk from the output of the photodetector; and 108 tilting the optical head from the detected value of the tilt detector to record the optical disk with respect to the optical axis of the light beam. This is a tilt correction unit that corrects the inclination of the surface. 110 is an off-track detector, 111
Is an off-track control unit. In addition, when a and d are regarded as an integral object and b and c are regarded as an integral object, the four-segmented photodetector can be regarded as a two-segmented photodetector divided into two in parallel in the track direction.

Next, the recording / reproducing operation will be described.

The optical head 102 allows the optical disk 10
The light spot focused on the focus control unit 10
5 focuses on the optical disc 101, and the tracking control unit 106 tracks the light spot to 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 marks of different shades such as a phase-change optical disc by using the focused and tracked light spot.

The recording operation will be described with reference to FIG.

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

Since the reflectivity differs between a mark and a space, the difference between the reflectivities during reproduction is determined by reading a signal recorded using a reproduction 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 disk 501 is
A line connecting the light spots focused on the optical disk 501 from the optical head 502 is called a radial direction 504, and a direction perpendicular to the radial direction 504 on a plane of the optical disk 501 is called a tangential direction 505. A direction perpendicular to a plane on the optical disk 501 is called a z-axis direction 506.

The tilt is classified into a radial tilt perpendicular to the track and a tangential tilt parallel to the track, as distinguished by direction.

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

In FIG. 6, reference numeral 601 denotes an optical disk;
Denotes an optical head, and 603 denotes a tilt table. The radial tilt (R tilt) includes a disc R tilt 604 caused by a warp of the disc, a runout caused by rotation of the disc, and the like, and the optical disc 60 with respect to the optical axis of the light beam.
The drive R tilt 6 in which the tilt (tilt) of the recording surface 1 occurs due to the mounting error of the optical head or the tilt of the tilt table.
05. Essentially, the disc R tilt and the drive R tilt are referred to as R tilt without distinction.

Referring to FIG. 7, tangential tilt (T
Tilt) will be described.

In FIG. 7, reference numeral 701 denotes an optical disk;
Denotes an optical head, and 703 denotes a tilt table. The tangential tilt (T tilt) includes a disk T tilt 70 caused by disk rotational vibration, disk surface accuracy error, and the like.
4, the drive T tilt 705 in which the tilt (tilt) of the recording surface of the optical disk 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 referred to as T tilt without distinction.

Next, a method for detecting the R tilt will be described. FIG.
The R tilt detection method in the tilt detection unit 107 of
There are the following: (1) In a tracking-on state, that is, in a state in which a light beam is operating along a track, a differential signal (push-pull) of a two-segment photodetector that receives light diffracted by a guide groove formed in advance on an optical disc. A method of detecting R tilt by detecting the voltage of TE). (2) In a tracking-off state, that is, in a state in which the light beam is operating while traversing the track, the differential signal of the two-segment 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 an R tilt by detecting the amplitude of a wobble signal of a guide groove formed while periodically wobbling the optical disc in advance while tracking is on. (4) The amplitude of the first half and the second half of the reproduction signal of the sum signal output of the two-segment photodetector when reproducing the continuous pit in the form of a dot mark pre-pitted on the optical disk 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-segment photodetector when reproducing a continuous pit in the form of a dot mark pre-pitted on the optical disk in the tracking-on state. A method of detecting the R tilt by comparing the level (upper envelope) of R. (6) Amplitude or lower side of the first half and second half of the reproduced signal of the sum signal output of the two-segment photodetector when reproducing the isolated pit in the form of a dot mark pre-pitted on the optical disk in the tracking-on state. There is a method of detecting the R tilt by comparing the signal level (lower envelope).

Of the above, (1), (3), (4),
In the methods (5) and (6), the R tilt is detected while the tracking is on. Even if an R tilt or a T tilt occurs, the off-track detection unit 11
0, the light spot can be positioned at the center of the track by the off-track control unit 111. Therefore, regarding (1), (3), and (5), first, the off-track detection unit 110 and the off-track control unit 111 position the light spot at the center of the track. In that state, pass through the center of the light spot (the center of the perfect circle)
The light spot is divided into two parts by a line parallel to the track direction, and the light quantity of each divided part is examined. When the light amounts of the two divided portions are equal, there is no R tilt, and when there is a difference, there is an R tilt.

The following (1), (3), (4), (5),
In the description of the method (6), the off-track detector 1
10. The description will be made assuming that the light spot is positioned at the center of the track by the off-track control unit 111. The 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 (5) is used as an embodiment, and the methods (1) to (4)
The method of (6) and the method (6) will be described below as reference examples.

REFERENCE EXAMPLE 1 First, the voltage of the differential signal (push-pull TE) of the two-segment photodetector that receives the light obtained by diffracting the light spot of (1) by the guide groove formed in advance on the optical disk is detected. A method for detecting the R tilt will be described as Reference Example 1.

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

In the example shown in FIG. 18, the tracking on control is performed and the off track control is performed, that is, the light spot is controlled to operate along the center of the track. . The waveform diagram shown in FIG. 18 shows a difference signal output (a push-pull TE signal) of the two-segment photodetector at the time of reproduction.

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

The tilt control section corrects the tilt angle by regarding the detected tilt value as a tilt angle.

FIG. 11 shows a simulation result of the relationship between the amount of R tilt and the detection value G detected by the tilt detector in the state where R tilt has occurred as described above. The optical conditions used in the simulation are wavelength 650 nm, NA
= 0.6, the RIM intensity, which is the normalized light intensity of the outer periphery of the objective lens in the radial direction, is 0.25, and the RIM intensity in the tangential direction is 0.83. The spot is the result when tracking is performed at the center of the track. In FIG. 11, when no R tilt occurs, the offset G of the push-pull TE signal is zero. 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 primary light spot having a hump shape is formed on the side of the light spot. When the R tilt angle is in the + direction (see FIG. 6), a + 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 minus direction, a minus first order light spot is generated on the left side of the perfect circle (see FIG. 18A). R tilt is +0.4
The 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-segment photodetector occurs between the case of the degree and the case of the R tilt of −0.4 degree. FIG. 1 shows a plot of the offset G of the push-pull TE signal.
It becomes a curve of 1.

The tilt detector detects a tilt angle using the offset G of the push-pull TE signal as a detected value of the tilt angle.

For example, the offset G of the push-pull TE signal which is a detection value detected by the tilt detection unit 107
Is −0.08, the R tilt is +
Since the tilt angle is 0.4 degrees, the tilt correction unit 108 transmits a tilt correction amount corresponding to the detected value to the tilt control unit 109, and the tilt control unit 109 moves the tilt table 103, thereby obtaining the R tilt angle. Is corrected.

The present R tilt detection method is not limited to the optical conditions used in the simulation, but can be implemented.

The tilt detection value is defined as the light amount when the reflected light from the mirror unit returns to the two-segment photodetector by 100%.
It is standardized as

REFERENCE EXAMPLE 2 Next, in the tracking-off state (2), a differential signal (push-pull TE) of a two-segment photodetector whose light spot receives light diffracted from a guide groove formed in advance on the optical disc is received. The method for detecting the R tilt by detecting the amplitude of (2) will be described as Reference Example 2.

Here, since the tracking is off, the light spot operates so as to cross the track. FIG. 19 shows the arrangement 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 a track which is the center of a guide groove, 19
03 is a guide groove formed in advance on the optical disc.

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

When the R tilt is 0 degrees, the amplitude K of the push-pull TE signal is large. If R tilt occurs 0.4 degrees, R
The tilt causes an aberration in the light spot. At this time,
The amplitude K of the push-pull TE signal also decreases due to diffraction. When the R tilt occurs at −0.4 degrees, an 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 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 degree. 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 detected tilt value as a tilt angle.

FIG. 12 shows a simulation result of the relationship between the amount of R tilt and the detection value K detected by the tilt detector in the state where R tilt has occurred as described above. The optical conditions used in the simulation are wavelength 650 nm, NA
= 0.6, RIM intensity in the radial direction 0.25, and RIM intensity in the tangential direction 0.83. In FIG. 12, when no R tilt occurs, the amplitude K of the push-pull TE signal
Is 1.0. When the R tilt occurs, the light spot has an aberration and the diffracted light from the guide groove is divided into two when the R tilt is ± 0.4 degrees and when the R tilt is ± 0 degrees. A difference occurs in the output (push-pull TE signal) of the differential signal when light is received by the detector. FIG. 12 shows a curve obtained by plotting the amplitude K of the push-pull TE signal.

The tilt detector detects the tilt angle using the amplitude K of the push-pull TE signal as a detected value of the tilt angle.

For example, if the amplitude K of the push-pull TE signal, which is a detection value detected by the tilt detection unit 107, is equal to 0.
In FIG. 12, since the R tilt is +0.4 degrees or −0.4 degrees from FIG.
Calculates the tilt correction amount corresponding to the detected value to the tilt control unit 1.
09, and the tilt control unit 109 moves the tilt table 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.

The tilt detection value is calculated by subtracting the amount of light when the reflected light from the mirror portion returns to 100% to the two-segment photodetector by one.
It is standardized as

REFERENCE EXAMPLE 3 Next, a differential signal of a two-segment photodetector which receives light diffracted from a guide groove formed while the light spot of (3) is periodically meandered (wobbled) on the optical disk in advance. 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 a layout of guide grooves on the optical disk and a push-pull TE signal waveform at that time. Reference numeral 2001 denotes a light spot, 2002 denotes a track center which is the center of the guide groove, and 2003 denotes a guide groove formed by wobbling in advance.

In this case, since the tracking is on, the light spot is operating along the center of the track. FIG. 20 shows a difference signal output (a wobble signal in this case) of the two-segment photodetector at the time of reproduction.

When the R tilt is 0 degree, the amplitude H of the wobble signal is
Is the largest. When R tilt occurs by 0.4 degrees, aberration occurs in the light spot due to R tilt. At this time, the amplitude H of the wobble signal also decreases due to diffraction. When the R tilt occurs at −0.4 degrees, an aberration occurs in the light spot due to the R tilt. At this time, the amplitude H of the wobble signal is
The amplitude also decreases due to the effect 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 degree.
The tilt detection unit holds the amplitude H of the wobble signal as a detection value of the tilt detection unit.

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

FIG. 13 shows a simulation result of the relationship between the amount of R tilt and the detection value H detected by the tilt detector in the state where R tilt has occurred as described above. The optical conditions used in the simulation are wavelength 650 nm, NA
= 0.6, RIM intensity in the radial direction 0.25, and RIM intensity in the tangential direction 0.83. The spot is the result when tracking is performed at the center of the track. In FIG. 13, when no R tilt occurs, the amplitude H of the wobble signal is 0.09. When the R tilt occurs, the light spot has an aberration and the diffracted light from the guide groove is divided into two 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 detector. FIG. 13 shows a curve obtained by plotting the amplitude H of the wobble signal.

The tilt detector detects a tilt angle using the amplitude H of the wobble signal as a detected value of the tilt angle.

For example, when the amplitude H of the wobble signal, which is a detection value detected by the tilt detection unit 107, is 0.083,
In FIG. 13, the R tilt is +0.4 degrees or −0.4 degrees from FIG.
A tilt correction amount corresponding to the detected value is calculated by the tilt control unit 109.
To the tilt table 10 by the tilt control unit 109.
By moving 3, the R tilt angle is corrected.

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 defined as the light amount when the reflected light from the mirror section returns to 100% to the two-segment photodetector.
It is standardized as

REFERENCE EXAMPLE 4 Next, the reproduction of the continuous pits in the form of a dot mark pre-pitched on the optical disc (4) will be described.
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 Reference Example 4.

FIG. 8 is a pit arrangement diagram 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 denotes a land track sandwiched between the groove tracks. 803
Is a first half repetitive pit row wobbled from the center of the groove track to the outer or inner circumference side, and 804 is the first half repetition pit row from the center of the groove track following the first half repetition pit row. The repetitive pit row of the section is a repetitive pit row of the rear half formed by wobbling at a symmetrical position with respect to the track center. Repetitive pattern of a wobble pit row having a radial pit interval of 1.19 μm, a pit width of 0.36 μm, a pit depth of λ / 6, a pit length of 0.462 μm, and a tangential pit interval of 1.12 μm, from the track center These pits are wobbled on the outer or inner peripheral side with a swing width of 0.3 μm to the pit center. The space Ls, which is the interval at which the shifted pit is repeated, is Lp <Ls <2 when the pit length is Lp.
Lp is satisfied.

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

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

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

As for the amplitude 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 held value Ab of the sum signal output of the first half and the held value of the sum signal output of the second half are obtained. The tilt control unit corrects the tilt angle by regarding the difference Ab−Bb of Bb as a tilt detection value and regarding the tilt detection value as a tilt angle.

FIG. 14 shows a simulation result of the relationship between the amount of R tilt and the detection value Ab-Bb detected by the tilt detector in the state where R tilt has occurred as described above. The optical conditions used in the simulation were 650 n wavelength.
m, NA = 0.6, RIM intensity in radial direction 0.25,
The RIM intensity in the tangential direction is 0.83. The spot is the result when tracking is performed at the center of the track. In FIG. 21, when no R tilt occurs, the difference Ab-Bb of the lower level 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 first half repeated pit and the amount of diffracted light from the second half repeated pit among the diffracted light from the pit. The curve of FIG. 14 is obtained by plotting the difference Ab-Bb between the lower level Ab of the sum signal output of the first half and the lower level Bb of the sum signal output of the second half.

The tilt detector detects the lower signal level difference A
The tilt angle is detected using b-Bb as a detected value of the tilt angle.

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

Here, the difference between the lower signal levels of the sum 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 unit. 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 row may be used.

Here, the difference between the lower signal levels of the sum signal output in the first half and the latter half of the repetitive pit train has been described as the detection value of the tilt control unit, but the lower signal level difference Ab of the sum signal output is used as the tilt detection value. Instead of -Bb, a signal amplitude difference CD of the sum signal output of the repeated pit train may be used.

As will be described later with reference to FIGS. 26 and 27, the difference between the sum signal of the first half repeated pit train and the sum signal of the second half repeated pit train is also used in off-track detection. As is clear from the above description, the sum signal fluctuates in a substantially sinusoidal curve, so that the value of the sum signal takes (i) an upper signal level and (ii) a lower signal level. There are three ways of taking the case and (iii) taking the amplitude of the sine wave curve. When the tilt detection method of (4) is performed, (i), (ii), (ii)
If any one of i) is adopted, the other one is adopted in off-track detection. This prevents the signal used for tilt detection and the signal used for off-track detection from being exactly the same.

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 defined as the light amount when the reflected light from the mirror section returns to 100% to the two-segment photodetector.
It is standardized as

REFERENCE EXAMPLE 5 Next, the lower half of the former half and the latter half of the reproduction signal of the sum signal output of the two-segment photodetector when reproducing the isolated pit in the form of a dot mark pre-pitted on the optical disk of (6) in advance. A method of 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 on an optical disk having isolated pits and a reproduced signal waveform at that time. 901
Is a groove track of a guide groove dug in a spiral to record data, and 902 is a land track sandwiched between the groove tracks. Reference numeral 903 denotes an isolated pit in the first half formed by wobbling from the center of the groove track to the outer peripheral side or the inner peripheral side;
Reference numeral 4 denotes a second half isolated pit which is wobbled from the center of the groove track to a position symmetrical with respect to the track center, following the first half isolated pit. The pit interval of the wobbled pit in the radial direction is 1.19 μm, the interval of the isolated pit in the track direction is 10 μm or more, the pit width of the isolated pit is 0.36 μm, the pit depth is λ / 6, the pit length is 0.462 μm, and the pit is from the track center. These pits are wobbled on the outer or inner peripheral side with a swing width of 0.3 μm to the center. Here, the space Ls, which is the interval at which the shifted pit is repeated, satisfies 20Lp <Ls when the pit length is Lp.

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

When the reproduced signal waveform has an R tilt of 0 degree, when the isolated pits in the first half and the isolated pits in the second half are reproduced, the lower levels E and F of the sum signal output modulated by the pits are obtained. Are in a relationship of E = F. R tilt is +
When it occurs at 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 is different from the lower level F of the sum signal output reproduced from the isolated pits in the latter half. The tilt detection unit holds the lower signal level difference EF of the sum signal output of the first half and the second half as a detection value of the tilt detection unit.

When R tilt 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 is different from the lower level F of the sum signal output reproduced from the isolated pits in the latter half. The tilt detection unit holds the lower signal level difference EF of the sum signal output of the first half and the second half as a detection value of the tilt detection unit.

As for the amplitude 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 held value E of the sum signal output of the first half and the held value of the sum signal output of the second half are obtained. The difference EF of F is set 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 and the detection value EF detected by the tilt detector in the state where R tilt has occurred as described above.
The optical conditions used in the simulation were a wavelength of 650 nm,
NA = 0.6, RIM intensity in the radial direction 0.25, and RIM intensity in the tangential direction 0.83. The spot is the result when tracking is performed at the center of the track. In FIG. 17, when no R tilt occurs, the lower signal level difference EF of the sum signal output is zero. When the R tilt occurs, the light spot has an aberration, and a difference occurs between the diffracted light amount from the isolated pit in the first half and the diffracted light amount from the isolated pit in the latter half of the diffracted light from the pit. FIG. 17 is a curve obtained by plotting the difference EF between the lower signal level E of the first half sum signal output and the lower signal level F of the second half sum signal output.

The tilt detector detects the tilt angle using the lower signal level difference EF of the sum signal output as a detected value of the tilt angle.

For example, the lower signal level difference E− of the sum signal output, which is a detection value detected by the tilt detector 107,
When F is +0.06, the R tilt is +
Since the tilt angle is 0.6 degrees, the tilt correction unit 108 transmits a tilt correction amount corresponding to the detected value to the tilt control unit 109, and the tilt control unit 109 moves the tilt table 103 to obtain the R tilt angle. Is corrected.

Note that the present R tilt detection method can be implemented without being limited to the optical conditions used in the simulation.

The tilt detection value is defined as the light amount when the reflected light from the mirror section returns to 100% to the two-segment photodetector.
It is standardized as

The tilt angle is calculated by the tilt correction unit, the tilt base is moved by the tilt control unit, the R tilt is eliminated, and the signal quality of the recording / reproducing signal is detected. Improve.

In order to detect the R tilt by the above-described methods (1), (3) to (6), it is necessary that the light spot scans the center of the track formed in advance by the guide groove. desirable. The deviation between the center of the track of the optical disc 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 disk, the above-mentioned (1)
When the R tilt is detected by the methods (3) to (6), the R tilt can be detected with higher accuracy.

Embodiment Next, (5) a method of reproducing a continuous pit in the form of a dot mark, which is pre-pitted on the optical disc, is described below.
A method for 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 an embodiment.

FIG. 23 is a pit arrangement diagram on the optical disk. Reference numeral 2301 denotes a groove track of a guide groove dug in a spiral shape for recording data, and reference numeral 2302 denotes a land track sandwiched between the groove tracks. 23
03 is a first half repeated pit row formed by wobbling from the center of the groove track to the outer side or the inner circumference side; 2304 is the first half of the repeated pit row following the first half repeated pit row; The first half repeated pit row is a second half repeated pit row formed wobbled at a symmetrical position with respect to the track center. 1.19 μm radial pit interval of wobbled pit row, 0.36 μm pit width
m, pit depth λ / 6, pit length 0.462 μm, tangential pit spacing 1.12 μm, repetitive pattern, swing width from track center to pit center is 0.
This is a pit wobbled on the outer or inner peripheral side of 3 μm.

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

In FIG. 23, one of the two split photodetectors is N1,
The other detector is N2. When playing back a continuous pit that is wobbled from the center of the track, one of the detectors is greatly modulated by the light diffracted by the pit, while the other is less affected by the pit diffraction, and the light intensity Little change. The difference signal output is the difference signal output N1-N2 between N1 and N2, and becomes the N- output.

FIG. 22 shows an example of reproducing the difference signal output of the two-segment photodetector.

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

As for the amplitude of the difference signal output between the first half and the second half, the DC value of the voltage is held by the sample hold circuit, and the held value I of the difference signal output of the first half and the held value of the difference signal output of the second half are obtained. The difference I-J of J is set 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. 15 shows 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 R tilt has occurred as described above.
The optical conditions used in the simulation were a wavelength of 650 nm,
NA = 0.6, RIM intensity in the radial direction 0.25, and RIM intensity in the tangential direction 0.83. The spot is the result when tracking is performed at the center of the track. In FIG. 15, when no R tilt occurs, the difference IJ 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 first half repeated pit and the amount of diffracted light from the second half repeated pit among the diffracted light from the pit. The plot of the amplitude difference IJ between the amplitude I of the first half difference signal output and the amplitude J of the second half difference signal output is the curve in FIG.

The tilt detector detects the tilt angle using the amplitude difference IJ of the difference signal output as a detected value of the tilt angle.

For example, when the amplitude difference IJ of the difference signal output, which is the detection value detected by the tilt detection section 107, is -0.0.
In the case of 09, from FIG. 15, the R tilt is +0.4 degrees, so the tilt correction unit 108 transmits a tilt correction amount corresponding to the detected value to the tilt control unit 109, and the tilt control unit 109 By moving the tilt table 103, the R tilt angle is corrected.

In the above case, the simulation result of the relationship between the amount of R tilt and the detection value IJ detected by the tilt detection unit when the light spot is off-track by +0.02 μm from the center of the track. Is shown in FIG.
It is. The optical condition used in the simulation was a wavelength of 65.
0 nm, NA = 0.6, RIM intensity in radial direction 0.2
5. The tangential RIM intensity is 0.83.
In FIG. 16, when no R tilt occurs, the difference IJ 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 first half repeated pit and the amount of diffracted light from the second half repeated pit among the diffracted light from the pit. FIG. 16 is a curve obtained by plotting the amplitude difference IJ between the amplitude I of the first half difference signal output and the amplitude J of the second half difference signal output. The curve in FIG. 16 is almost the same as the curve in FIG. This is because the detection result of the tilt angle is the same between the case where the light spot is at the center of the track (FIG. 15) and the case where the light spot is shifted from the center of the track by +0.02 μm (FIG. 16). Is shown.

The tilt detector detects a tilt angle using the amplitude difference IJ of the difference signal output as a detected value of the tilt angle.

For example, when the amplitude difference IJ of the difference signal output, which is the detection value detected by the tilt detection unit 107, is -0.0.
In the case of 09, since the R tilt is +0.4 degrees from FIG. 16, the tilt correction unit 108 transmits a tilt correction amount corresponding to the detected value to the tilt control unit 109, and the tilt control unit 109 By moving the tilt table 103, the R tilt angle is corrected.

In this case, it is possible to accurately detect the R tilt angle even if the light spot is off-track from the center of the track.

Here, the amplitude difference between the difference signal outputs in the first half and the second half of the repetitive pit train has been described as the detection value of the tilt control unit, but the amplitude difference IJ of the difference signal output is used as the tilt detection value.
, The upper signal level difference It-Jt of the difference signal output of the repeated pit train may be used.

Note that the present R tilt detection method can be implemented without being limited to the optical conditions used in the simulation.

The tilt detection value is defined as the light amount when the reflected light from the mirror unit returns to the two-segment photodetector by 100%.
It is standardized as

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

In the off-track, a repetitive pit row formed by wobbling the optical disk in advance is controlled by using a sum signal output of a signal reproduced by a light spot.

FIG. 24 is a pit arrangement diagram on the optical disk. Reference numeral 2401 denotes a groove track of a guide groove dug in a spiral shape for recording data, and 2402 denotes a land track sandwiched between the groove tracks. 24
03 is a first half repeated pit row formed by wobbling from the center of the groove track to the outer circumference or inner circumference side, and 2404 is the first half repeated pit row from the center of the groove track following the first half repeated pit row. The first half repeated pit row is a second half repeated pit row formed wobbled at a symmetrical position with respect to the track center. 1.19 μm radial pit interval of wobbled pit row, 0.36 μm pit width
m, pit depth λ / 6, pit length 0.462 μm, tangential pit spacing 1.12 μm, repetitive pattern, swing width from track center to pit center is 0.
This is a pit wobbled on the outer or inner peripheral side of 3 μm.

FIG. 25 shows an example of reproduction of the sum signal output of the two-segment photodetector.

When the reproduced signal waveform is off-track 0, when the first half repeated pits are reproduced and when the second half repeated pits are reproduced, the amplitudes L and M of the signal modulated by the pit train are L = M. In a relationship. When the off-track is generated by 0.02 μm, the off-track causes a light amount difference between the two detectors of the two-segment photodetector. At this time, the amplitude L of the sum signal output reproduced from the first half repeated pit train is different from the amplitude M of the sum signal output reproduced from the second half repeated pit train. The amplitude of the sum signal output of the first half and the second half is determined by the sample and hold circuit.
The DC value of the voltage is held, and the difference L−M between the held value L of the sum signal output of the first half and the held value M of the sum signal output of the second half is defined as the off-track detection value, and this detected 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, the R at different radial positions on the optical disc is determined.
A tilt correction method will be described with reference to FIG.

Since the R tilt is generated by the warpage 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, reference numeral 1001 denotes an actual tilt curve representing how the inclination (tilt) of the recording surface of the optical disk with respect to the optical axis of the light beam changes with the radial position of the optical disk. The amount of tilt (or tilt angle) at a predetermined radial position on the inner circumference on the tilt curve 1001, and 1003 is the tilt curve 10
A tilt amount at a predetermined radius position on the middle circumference on 01, 1004
Is a tilt amount at a predetermined radius position on the outer circumference on the tilt curve 1001.

Next, the amount of tilt estimated from the detected value detected by the tilt detecting section will be described. 100
Reference numeral 5 denotes a tilt amount estimated from a detection value detected at a predetermined radial position on the inner periphery of the optical disk by the tilt detecting unit. Reference numeral 1006 denotes a tilt amount detected at a predetermined radial position on the outer periphery of the optical disk by the tilt detecting unit. The tilt amount estimated from the detected value, 1007 is the tilt amount estimated from the detected value detected by the tilt detection unit at a predetermined radial position on the center of the optical disc, and 1008 is the estimated tilt on the center. An interpolated curve 1008 obtained by linearly interpolating the calculated tilt amount 1007, the estimated tilt amount 1005 at the inner periphery, and the estimated tilt amount 1006 at the outer periphery.

When the optical disc tilts, the amount of tilt differs between the inner circumference and the outer circumference. In order to detect the difference of the tilt amount due to the radial position, the optical disk device of the present invention detects the tilt amount 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 middle radius 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 detected value at the middle position. Curve 10 obtained by linearly interpolating the calculated tilt amount 1007
The value on 08 is the estimated tilt amount at a desired radial position between the inner circumference and the middle circumference. The tilt amount at the radial position between the outer and middle radius positions where the tilt angle is detected is:
The tilt amount 1006 estimated from the detected value at the outer circumference
And the tilt amount 100 estimated from the detected value at the middle circumference.
The value on the curve 1008 obtained by interpolating 7 with a straight line is the estimated tilt amount at a 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 in the middle of the optical disc and the actual tilt amount 1003 in the middle of the optical disc, as compared with the conventional method. In addition, the tilt position can be accurately and accurately corrected at each radial position with respect to an optical disk having different amounts of tilt between the inner and outer circumferences, and the signal quality during recording and reproduction of the optical disk can be significantly improved.

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 radius position. Alternatively, the tilt angle on the inner circumference is relatively set to 0 degree. The tilt angle of the outer circumference of the optical disc is larger than that of the inner circumference due to the deflection of the disc. This deflection varies from disk to disk, and the characteristics of the magnitude of the tilt angle with respect to the radial position differ for each disk.

The radial position at which the light spot converges on the optical disk surface moves outward, and the tilt angle is detected by the tilt detecting section at the middle or outer circumference, and the tilt angle in the tilt curve interpolated by 1008 is changed. If the difference is more than a threshold value (for example, 0.4 degrees) compared to the tilt angle on the inner circumference,
The tilt correction unit instructs the tilt table 103 to move so that the tilt angle becomes 0 at a radial position where the tilt angle is the threshold value.

Thus, it is possible to reduce the tilt angle caused by the deflection of the disk from the inner circumference to the outer circumference by moving the tilt base, thereby improving the signal quality during recording and reproduction of the optical disk. 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, four quadrant detector 100
The operation of the arithmetic circuit 104 that operates upon receiving the outputs a, b, c, and d from the two light receiving elements 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 used to control the tracking position of the light spot on the track of the optical disk. The FE signal is sent to the focus control unit 105, and is used to control the focal position of the light spot on the optical disc. The R
The F signal reads out the data recorded on the optical disc and becomes a reproduction signal, which is subjected to data processing. Further, the RF signal is sent to the off-track detecting section 110 and used for off-track position detection. The off-track detection signal (OF signal) is sent to the off-track detection section 110 and used for off-track position detection.

Next, a process in which the off-track position is detected from the off-track detection signal by the off-track detection section 110 will be described.

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

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

Here, as shown in FIG.
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 that the phase difference between the diagonal difference signals (a + c) and (b + d) is 0. Even when the disk 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. The light spot deviates from the track, and FIG.
As shown in FIG. 27C, with the rotation of the disk, FIG.
, The diagonal difference signals are both sinusoidal outputs, but these are the RF signals (a + b +
c + d), the phase has a relationship of +90 degrees and -90 degrees. Therefore, if the phase difference of the diagonal difference signal with respect to the RF signal is detected, it is possible to detect how much the light spot is off-track from the center of the pit. it can.

In the off-track detection, the difference between the sum signal of the first half repeated pit train and the sum signal of the second half repeated pit train is used. As described with reference to FIG. 21, the diagonal sum signal fluctuates in a substantially sinusoidal curve, so that 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 of the diagonal difference signal and off-track. In the figure, (Bsi
g) shows an output point when the light spot passes through the center of the pit, and an output point when (Asig) and (Csig) pass through the left and right sides of the pit, respectively. Using this phase difference, the off-track position from the center of the pit can be detected.

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

FIG. 28B is a graph of the phase difference signal of the diagonal difference signal centered on the pit. When the light spot passes through the center of the groove track in the first half pre-pit row,
The output of the phase difference signal is Pa, and the output of the phase difference signal is Pb when the light spot passes through the center of the groove track in the latter half prepit row. The phase difference signal in the first half prepit row and the phase difference signal in the second half prepit row are held,
FIG. 28 shows the result of calculating the sum of the output of the first half pre-pit train and the output of the second half repeated pit train by the off-track detector.
(C). When the light spot passes through the center of the track, the phase difference sum signal becomes zero.

A description will be given of the result of performing a computer simulation based on the above conditions. 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, cycle of repeated pits in the linear direction is 1.12 μm, pit length 0.46 μm
m is a repeated wobble pit row.

FIG. 29 shows the characteristics when R tilt occurs.

In FIG. 29, when the R tilt is given at −0.6 degrees, ± 0.0 degrees, and +0.6 degrees in the order of (a), (b), and (c), the phase difference signal is defined as the first half wobble pit. The off-track detection signal calculated in the latter 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 (b), it can be seen from the graph that an off-track detection signal corresponding to the off-track amount is obtained. When the off-track position is 0, the off-track detection signal is also 0.

Next, when an R tilt occurs, for example, (a)
It can be seen from the graph that the off-track detection signal corresponding to the off-track amount is obtained when the inclination is −0.6 degrees. When the off-track position is 0, the off-track detection signal is also 0.

The same applies to the case (c).

As described above, by reproducing the phase difference signal and the continuous prepits arranged in the form of a wobble, the off-track amount can be accurately detected without affecting the R tilt. By using the present method in the off-track detecting section of the embodiment, good results of tilt detection and tilt control can be obtained.

As a result, the accuracy of tracking is improved,
It is possible to improve the signal quality of the signal recorded on the adjacent track, except for the effect of cross erasure that erases the adjacent track during recording.

[0149]

As described above, according to the optical disc apparatus and the tilt control method of the optical disc of the present invention, an optical system for detecting a tilt angle is not required separately from an optical system for a recording / reproducing signal. Using a repetitive pit row formed by shifting the center of the groove track, land track and groove track from the center to the outer or inner circumference side, independently or in combination, detects the tracking signal and tilt angle, and corrects tilt It is possible to improve the signal quality at the time of recording / reproducing by correcting the tilt angle using the unit and the tilt control unit. As a result, it is not necessary to provide a separate tilt detector, so that the implementation scale of the apparatus can be reduced and the cost can be reduced.

As in the tilt detecting method shown in FIG. 10, the tilt amount at a desired radial position of the optical disk is estimated from at least three detected 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 the drawings]

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

FIG. 2 is a configuration diagram of a conventional optical disk device.

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

FIG. 4 is a diagram for explaining recording and reproduction in the optical disc device according to the embodiment of the present invention;

FIG. 5 is a configuration diagram showing a relationship between an optical disk and an optical disk device in the embodiment of the present invention.

FIG. 6 is a diagram for explaining R tilt according to the present invention;

FIG. 7 is a view for explaining a T tilt according to the present invention;

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

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

FIG. 10 is a graph showing a relationship between a radial position and an R tilt in 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 first embodiment of the present invention.

FIG. 12 is a graph showing the relationship between the R tilt and the 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 the R tilt and the wobble signal amplitude in the third embodiment of the present invention.

FIG. 14 is a graph showing the relationship between the R tilt and the lower signal level difference of the sum signal of the repeated continuous pit row in the case of Embodiment 4 of the present invention.

FIG. 15 is a graph showing a relationship between an R tilt and a difference signal amplitude difference between repeated continuous pit strings in the case of the embodiment of the present invention.

FIG. 16 is a graph showing the relationship between the R tilt and the difference signal amplitude difference between repeated pit strings when there is off-track in the embodiment of the present invention.

FIG. 17 is a graph showing the relationship between the R tilt and the signal level difference below the sum signal of the isolated pits in the case of the fifth embodiment of the present invention.

FIG. 18 is a diagram for explaining the relationship between the R tilt and the push-pull TE signal in the first embodiment of the present invention.

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

FIG. 20 is a diagram for explaining the relationship between the R tilt and the wobble signal amplitude in the third embodiment 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 train in the case of Embodiment 4 of the present invention;

FIG. 22 is a diagram for explaining the relationship between the R tilt and the difference signal output between repeated continuous pit strings in the case of the embodiment of the present invention.

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

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

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

FIG. 26 is a diagram illustrating an off-track detection method according to a sixth embodiment of the present invention.

FIG. 27 is a diagram for explaining a phase difference signal according to Embodiment 6 of the present invention;

FIG. 28 is a view for explaining an off-track detection method according to the sixth embodiment 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]

Reference Signs List 100 quadrant photodetector 101 optical disk 102 optical head 103 tilt table 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 Repeated pit train 804 Second half repeated pit train 903 First half isolated pit 904 Second half isolated pit

Claims (7)

[Claims] 1. A track formed continuously in a concentric circle or spiral shape and a track provided on the track at regular intervals and shifted from the center of the track to the first side and the second side of the track, respectively. What is claimed is: 1. A tilt detection device for detecting an inclination of a recording surface of an optical disk having a first shift pit and a second shift pit, wherein a light spot obtained by focusing a light beam on the optical disk is applied.
An optical head for recording and reproducing signals; a two-divided photodetector for receiving reflected light from the optical disc with first and second light-receiving elements divided into two along a track direction line; Tracking control means for controlling a position on a track using a push-pull signal which is a difference signal of the two-divided photodetector; and a first and second divided photodetector receiving reflected light from the first shift pit. The third which is the sum of the outputs from the light receiving elements
The sum signal and the reflected light from the second shift pit are received by a two-segment photodetector, and a fourth sum signal, which is the sum of the outputs from the first and second light receiving elements, is compared with each other. An off-track detecting unit that outputs an offset amount that is a deviation amount between the center and the center of the light spot; and adding an output of the off-track detecting unit to the tracking control unit, so that the light spot is positioned at the center of the track. Receiving the reflected light from the first shift pit by a two-segment photodetector, and calculating a first difference signal which is a difference between outputs from the first and second light receiving elements, and a reflected light from the second shift pit. A tilt detecting means for detecting the inclination of the recording surface of the optical disk by receiving the light with the two-segment photodetector and comparing a second difference signal which is a difference between outputs from the first and second light receiving elements. And j Default detector. 2. The apparatus according to claim 1, wherein said tilt detecting means includes a level having a higher absolute value of an envelope signal of said first difference signal and said second level.
2. The tilt detecting device according to claim 1, wherein the difference signal is compared with a level having a higher absolute value of an envelope signal. 3. The tilt detecting device according to claim 1, wherein the tilt detecting means compares the amplitude of the first difference signal with the amplitude of the second difference signal. 4. The tilt according to claim 1, wherein in the optical disc, the first shift pit is repeatedly provided continuously and the second shift pit is continuously provided repeatedly. Detection device. 5. The tilt according to claim 4, wherein in the optical disc, a space Ls, which is an interval at which the first shift pit is repeated, satisfies Lp <Ls <2Lp when a pit length is Lp. Detection device. 6. A track formed continuously in a concentric circle or spiral shape, and formed at regular intervals on the track and formed so as to be shifted from the center of the track to the first side and the second side of the track, respectively. What is claimed is: 1. An optical disk device for detecting and correcting the inclination of a recording surface of an optical disk having a first shift pit and a second shift pit, wherein a light spot with a light beam focused on the optical disk is applied.
An optical head for recording and reproducing signals; a two-division detector for receiving reflected light from the optical disk by first and second light-receiving elements divided into two along a track direction line; Tracking control means for controlling a position on a track using a push-pull signal which is a difference signal of a split photodetector; and off-track generated from a reproduction signal obtained by reproducing the first shift pit and the second shift pit by the optical head. An off-track detecting means for generating a detection signal; and an output of the off-track detecting means being added to the tracking control means, and the reflected light from the first shift pit is divided by two with the light spot positioned at the center of the track. A first difference signal which is received by the split photodetector and which is a difference between outputs from the first and second light receiving elements and a reflected light from the second shift pit are detected by the two split photodetector. Tilt detecting means for detecting the tilt of the recording surface of the optical disk by receiving the light and comparing it with a second difference signal which is a difference between outputs from the first and second light receiving elements; and a tilt amount detected by the tilt detecting means An optical disk device comprising: a tilt correction unit configured to correct an angle of the optical disk by using the tilt correction unit. 7. A track formed continuously in concentric circles or spirals, and a track provided on the track at regular intervals and formed so as to be shifted from the center of the track to the first side and the second side of the track, respectively. What is claimed is: 1. A tilt detection method for detecting an inclination of a recording surface of an optical disk having a first shift pit and a second shift pit. The first and second light receiving elements divided into two along the direction line receive light, and perform tracking control for controlling the position of the light spot on a track using a push-pull signal which is a difference signal of a two-part light detector. 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; The output of the off-track detection signal is added to the signal for performing the docking control, and the reflected light from the first shift pit is received while the light spot is located at the center of the track. The difference between the outputs of
The inclination of the recording surface of the optical disc is detected by comparing the difference signal with the reflected light from the second shift pit and comparing the difference signal with the second difference signal, which is the difference between the outputs from the first and second light receiving elements. A tilt detection method, characterized in that: