JP4370567B2 - Optical disc apparatus and optical disc control method - Google Patents

Description

  The present invention relates to a method of controlling an optical disc by detecting a relative radial tilt between the optical disc and an objective lens, and an optical disc apparatus using the same.

で示される。ここで、ＮＡは対物レンズの開口数、ｔは光ディスクの基板厚、λは光ディスク上に照射されるレーザー光の波長、θは光ディスクのチルト量である。このチルトに依存するコマ収差が存在すると、対物レンズにより光ディスクの記録面上に集光された光スポットがコマ収差により変形し、記録再生特性が悪化する。 Conventionally, in a DVD (Digital Versatile Disc), recording and reproduction are performed through a 0.6 mm transparent substrate in order to protect the recording layer. In the current optical disc, warpage occurs in the manufacturing process of the disc. In particular, warping in the radial direction (radial direction) is likely to occur. When the optical disk is warped, a relative tilt shift, that is, a tilt occurs between the normal to the recording surface of the optical disk and the optical axis of the objective lens of the optical disk apparatus. In general, the coma aberration generation amount W due to the relative tilt between the optical disk and the objective lens of the optical disk apparatus is expressed by the following equation (1).

Indicated by Here, NA is the numerical aperture of the objective lens, t is the substrate thickness of the optical disk, λ is the wavelength of the laser light irradiated onto the optical disk, and θ is the tilt amount of the optical disk. When coma aberration depending on the tilt exists, the light spot collected on the recording surface of the optical disk by the objective lens is deformed by coma aberration, and the recording / reproducing characteristics deteriorate.

  In order to suppress the deterioration of the recording / reproducing characteristics due to the tilt, the optical disc apparatus detects the relative tilt between the optical disc and the objective lens of the optical disc apparatus, and the objective lens and the optical disc of the optical disc apparatus are matched with the tilt amount. Tilt control for tilting is performed, thereby ensuring stable recording and reproduction characteristics.

  In recent years, in order to increase the storage capacity further than DVD, development of a next-generation optical disk apparatus using a blue semiconductor laser having a short wavelength λ as a light source and using an objective lens having a large numerical aperture NA is in progress. In this next-generation optical disk device, if an optical disk having the same substrate thickness t as that of a conventional DVD is used, the wavelength λ of the light source is short and the numerical aperture NA of the objective lens is large. growing. Therefore, it is necessary to detect the tilt in the radial direction between the optical disk and the objective lens of the optical disk apparatus with higher accuracy than in the conventional DVD. A highly accurate radial tilt detection method has been proposed in the 64th JSAP Scientific Lecture 31a-YD-12 (Conventional Example 1: Non-Patent Document 1).

  FIG. 1A is a diagram showing the relationship between the radial tilt detection pattern and the sum signal waveform of the optical disc apparatus in the case of the land / groove recording method described in Conventional Example 1. FIG. A radial tilt detection pattern 7 is formed in a part of the area not used for recording on the optical disc. The radial tilt detection pattern 7 has a first cut part 4 and a second cut part 5.

  The radial tilt is detected using the light spot 1 on the land recording track 2. When the light spot 1 passes beside the first cut portion 4 and the second cut portion 5, the amount of reflected light changes. The sum signal level of the reflected light when the light spot 1 passes the side of the first cut portion 4 is SA, and the sum signal level of the reflected light when the light spot 1 passes the side of the second cut portion 5 is SB. As shown in FIG. 1B, when there is no radial tilt, there is no difference between the sum signal levels SA and SB. However, as shown in FIG. 1C, when a radial tilt exists, a difference occurs between the sum signal levels SA and SB. This sum signal difference (SA-SB) is a signal indicating radial tilt. Hereinafter, (SA−SB) is set to ΔS.

  In relation to the above description, a tilt detection apparatus is disclosed in Japanese Patent Application Laid-Open No. 2000-242952. In this conventional tilt detection apparatus, the tilt of the recording surface of the optical disc is detected. On the optical disc, tracks are continuously formed in a concentric or spiral shape, and first shift pits and second shift pits are formed on the first side and the second side of the track from the center of the track. The optical head records and reproduces signals by irradiating the optical disc with a light spot obtained by narrowing the light beam. The two-divided light detector receives the reflected light from the optical disc with the first and second light receiving elements that are divided into two along the line in the track direction. The tracking control unit controls the position of the light spot on the track. The tilt detector receives the reflected light from the continuous track with a two-divided photodetector, and uses the difference signal that is the difference between the signals from the first and second light receiving elements to record the optical disk recording surface relative to the optical axis of the light beam. Detect the slope of.

  An information reproducing apparatus is disclosed in Japanese Patent Application Laid-Open No. 2003-59071. In this conventional information reproducing apparatus, the first detector outputs the difference between the individual output signals optically obtained by a pair of detectors that read the information of the first track. The second and third detection units output a difference between output signals optically obtained by a pair of detectors that respectively read information on the second track and the third track located on both sides of the first track. The crosstalk extraction unit extracts crosstalk derived from the second track and the third track included in the detection signal output from the first detection unit. The tracking control unit performs tracking control of the first detection unit based on a balance between the crosstalk of the second track and the crosstalk of the third track extracted by the crosstalk extraction unit.

The 64th Japan Society of Applied Physics Academic Lecture 31a-YD-12 JP 2000-242952 A JP 2003-59071 A

An object of the present invention is to provide a method for detecting a relative radial tilt between an optical disc and an objective lens with high accuracy, and an optical disc apparatus using the same.
Another object of the present invention is to provide a method for detecting a radial tilt separately from the effects of lens shift of an objective lens and off-track of a light spot, and an optical disk apparatus using the method.
An object of the present invention is to provide a method for controlling an optical disc based on the radial tilt detected by the detection method, and an optical disc apparatus using the same.

  The means for solving the problem will be described below using the numbers and symbols used in the [Embodiments of the Invention]. These numbers and symbols are added to clarify the correspondence between the description of [Claims] and the description of the embodiments of the invention, but are described in [Claims]. It should not be used to interpret the technical scope of the invention.

  In a first aspect of the present invention, a radial tilt control method includes (a) a step of rotating an optical disc (14) having spiral or concentric tracks, and a light spot on the optical disc via an objective lens. Forming a step. The optical disc includes a first track, and at least one radial tilt detection pattern (7, 34, 38) is provided in association with the first track. The radial tilt control method further includes (b) an original mode when the light spot is positioned on the first track, an off-track mode in which an off-track is given to the light spot in the original mode, and the original mode. Setting a lens shift mode in which a lens shift is given to the objective lens in step (c), and (c) in each of the original mode, the off-track mode, and the lens shift mode, the light spot passes through the first track. Generating a first to a third electrical signal from a reflected light signal from the radial tilt detection pattern via the objective lens during scanning. Here, the first electric signal includes a component that depends on a radial tilt of the optical disc, and the second electric signal includes a component that does not depend on the radial tilt but depends on the lens shift, and the third electric signal. The electrical signal does not depend on the radial tilt but includes a component that depends on off-track. The radial tilt control method further includes (d) a radial tilt using a set of final coefficient ratios calculated from the first to third electric signals in each of the original mode, the off-track mode, and the lens shift mode. And (e) correcting the influence of the radial tilt based on the detected radial tilt.

  In another aspect of the present invention, an optical disc control method includes: (f) irradiating a rotating optical disc with a light spot so that at least one radial tilt detection pattern provided in association with the first track of the optical disc. Generating first to third electric signals from the reflected light signals of the optical disc, the first electric signal includes a component that depends on a radial tilt of the optical disc, and the second electric signal depends on the radial tilt. The third electrical signal does not depend on the radial tilt but includes an off-track dependent component, and (g) is calculated from the first to third electrical signals. Detecting a radial tilt using a set of final coefficient ratios, and (h) the radial tilt based on the detected radial tilt And a step of correcting the influence.

  As described above, in the present invention, the radial tilt is calculated using the ratio obtained from the electrical signal detected in the original mode, the electrical signal detected in the off-track mode, and the electrical signal detected in the lens shift mode. The influence can be corrected. For this reason, it is not necessary to go through the troublesome procedure of performing a theoretical simulation and comparing the measured value with the measured value.

Here, the radial tilt detection pattern includes the first portion (4) including an extended portion provided in the inner circumferential direction from the first track, and the extended portion provided in the outer peripheral direction from the first track. The second portion (5), the first portion, and the third portion other than the second portion. Preferably, the extended portion of each of the first portion and the second portion has the same height as the first track.
Further, in the (c) generating step, when an electric signal of the sum of electric signal components detected from the reflected light signal is a sum signal, each of the original mode, the off-track mode, and the lens shift mode is used. The first electric signal is defined as a difference between the sum signal when the light spot passes through the first portion of the radial tilt detection pattern and the sum signal when the light spot passes through the second portion. In the original mode, the off-track mode, and the lens shift mode, when generating a difference between two electrical signals obtained by dividing the reflected light into two in the radial direction, as a difference signal, The difference signal when the light spot passes through the first part, and the difference signal when the light spot passes through the second part. And generating the second electrical signal as a difference between the signal, the light spot is and a step of generating the third signal as the difference signal when it passes through the third portion.
The electric signals used in the optical disc control method of the present invention are a sum signal difference, a difference signal difference, and a difference signal, and these can be measured without adding a special device.

When the radial tilt detection pattern is provided in relation to the first track, and the set of final coefficient ratios includes first to third final coefficient ratios, the detection step (d) includes: A difference between the first electric signal in the lens shift mode and the first electric signal in the original mode, and a difference between the second electric signal in the lens shift mode and the second electric signal in the original mode. Calculating a first coefficient ratio as a ratio; a difference between the first electrical signal in the off-track mode and the first electrical signal in the original mode; and the third electrical signal in the off-track mode and the original Calculating a second coefficient ratio as a ratio to a difference from the third electrical signal in a mode; and As a ratio of the difference between the second electric signal in the mode and the second electric signal in the original mode and the difference between the third electric signal in the off-track mode and the third electric signal in the original mode Calculating a three-coefficient ratio; and maintaining the first to third coefficient ratios as the first to third final coefficient ratios.
In the present invention, the radial tilt can be easily determined at any time by determining the ratio between the electrical signals. No simulation is necessary.

A plurality of radial tilt detection patterns are provided in relation to the first track, and the set of final coefficient ratios includes the first to third final coefficient ratios, and the plurality of radial tilt detection patterns. In each of the patterns, the detection step (d) includes the difference between the first electric signal in the lens shift mode and the first electric signal in the original mode, the second electric signal in the lens shift mode, and the original. Calculating a first coefficient ratio as a ratio with a difference from the second electric signal in the mode; and a difference between the first electric signal in the off-track mode and the first electric signal in the original mode and the off A difference between the third electric signal in the track mode and the third electric signal in the original mode; Calculating a second coefficient ratio as a difference between the second electric signal in the off-track mode and the second electric signal in the original mode and the off-track mode in each of the plurality of radial tilt detection patterns Calculating a third coefficient ratio as a ratio of a difference between the third electric signal in the original mode and the third electric signal in the original mode; and each of the first to third coefficient ratios is set to the plurality of radial tilts. Averaging over the detection pattern and holding the averaged first to third coefficient ratios as the first to third final coefficient ratios.
By providing a plurality of radial tilt detection patterns for the same track, the average radial tilt on the same track can be obtained, and more practical radial tilt control is possible.

In the detection step (d), when the first electric signal, the second electric signal, and the third electric signal in the original mode are set to ΔS, ΔD1, and ΔD2, the following expression f = ΔS−AΔD1−BΔD2 (A, B: coefficients)
The coefficient A is the first final coefficient ratio, and the coefficient B is [(the second final coefficient ratio) − (the first final coefficient ratio). ) X (the third final coefficient ratio)}.

  In another aspect of the present invention, the optical disc apparatus includes a rotation drive unit that rotates an optical disc (14) having spiral or concentric tracks, and the optical disc (14) includes a first track. At least one radial tilt detection pattern (7, 34, 38) is provided in association with the first track. The optical disc apparatus also includes a control unit (27) for setting an original mode, an off-track mode, and a lens shift mode, and an objective lens, and irradiates the optical disc (14) with a light spot through the objective lens. And an optical system (8, 9, 10, 11, 13, 12, 15, 16,...) That generates an electrical signal from the reflected light signal from the radial tilt detection pattern (7, 34, 38) via the objective lens. 17) and controlling the optical system (8, 9, 10, 11, 13, 12, 15, 16, 17) to position the light spot on the first track in response to a seek command, A lens position control unit (43, 40, 42) for giving a lens shift to the objective lens in response to a lens shift command from the control unit; and the optical spot on the track. An off-track control unit (39, 45) for controlling an error in the radial direction of the control unit to give off-track to the light spot in response to an off-track command from the control unit, and in response to a tilt signal generation instruction, First to third electrical from the electrical signal from the optical system (8, 9, 10, 11, 13, 12, 15, 16, 17) in each of the original mode, the off-track mode, and the lens shift mode A computation unit (23, 24, 25, 26, 29) that generates a signal, calculates a set of final coefficient ratios from the first to third electrical signals, and generates a radial tilt signal using the set of final coefficient ratios. 30) and a tilt control unit (31) for controlling the tilt of the objective lens in response to the radial tilt signal. The control unit (27) controls the off-track control unit (39.45) to control the position of the light spot on the first track in the original mode. The arithmetic unit (23, 24, 25, 26, 29, 30) is controlled to generate a third electric signal, and the off-track command is sent to the off-track control unit (39.45) in the off-track mode. Controlling the arithmetic units (23, 24, 25, 26, 29, 30) so as to generate the first to third electric signals in the off-track mode, and the lens shift command in the lens shift mode. Is output to the lens position control unit, and the arithmetic unit is configured to generate the first to third electrical signals in the lens shift mode. 23, 24, 25, 26, 29, 30), and sends the tilt signal generation instruction to the arithmetic units (23, 24, 25, 26, 29, 30). , 29, 30). Here, the first electric signal includes a component that depends on a radial tilt of the optical disc (14), and the second electric signal does not depend on the radial tilt but includes a component that depends on the lens shift, The third electrical signal includes a component that does not depend on the radial tilt but depends on off-track.

  As described above, in the present invention, the radial tilt is calculated using the ratio obtained from the electrical signal detected in the original mode, the electrical signal detected in the off-track mode, and the electrical signal detected in the lens shift mode. The influence can be corrected. There is no need to add special units in this way. Moreover, it is not necessary to go through the troublesome procedure of performing a theoretical simulation and comparing the measured value with the measured value.

  The radial tilt detection patterns (7, 34, 38) are provided in the first portion (4) including an extended portion provided in the inner circumferential direction from the first track, and in the outer circumferential direction from the first track. The second part (5) including an extended part, and the third part other than the first part and the second part. It is preferable that the extended portion of each of the first portion (4) and the second portion (5) has the same height as the first track.

  When the arithmetic unit (23, 24, 25, 26, 29, 30) uses a sum signal of the sum of electric signal components detected from the reflected light signal, the original mode, the off-track mode, And in each of the lens shift modes, the sum signal when the light spot passes through the first portion of the radial tilt detection pattern (7, 34, 38), and the light spot passes through the second portion. A sum signal detector (23) that generates the first electric signal as a difference between the sum signals, and a difference signal between two electric signals obtained by dividing the reflected light into two in the radial direction. The difference signal when the light spot passes through the first portion in each of the original mode, the off-track mode, and the lens shift mode. The second electrical signal is generated as a difference from the difference signal when the light spot passes through the second portion, and the third signal is used as the difference signal when the light spot passes through the third portion. And a difference signal detector (24) for generating a signal.

  When the radial tilt detection pattern (7, 34, 38) is single, the arithmetic unit (23, 24, 25, 26, 29, 30) is configured to output the single radial tilt detection pattern (7, 34, 38). 38), a coefficient ratio calculation unit (25, 26) for calculating a set of coefficient ratios from the first to third electric signals in each of the original mode, the off-track mode, and the lens shift mode; A coefficient ratio storage unit (29) for storing the set of coefficient ratios as the set of final coefficient ratios, and the radial tilt signal from the set of the first to third electrical signals and the final coefficient ratio in the original mode. And a radial tilt calculation unit (30) for generating

  When there are a plurality of radial tilt detection patterns (7, 34, 38), the calculation unit (23, 24, 25, 26, 29, 30) includes a coefficient ratio storage unit (29) and the single radial For the tilt detection pattern (7, 34, 38), a coefficient ratio set is calculated from the first to third electrical signals in each of the original mode, the off-track mode, and the lens shift mode, and the coefficient ratio is stored. When the calculation of the set of coefficient ratios from the plurality of radial tilt detection patterns (7, 34, 38) is completed, the corresponding coefficient ratios are stored in the plurality of radial tilt detection patterns (7, 34, 38). And a coefficient ratio calculation unit (25, 26) that stores the average coefficient ratio group in the coefficient storage unit (29) as the final coefficient ratio group, and the originator It comprises radial tilt calculation unit for generating the radial tilt signal third electrical signal from the first in the mode from the set of final coefficients ratio and (30).

The radial tilt calculation unit (30) sets the following formula f = ΔS−AΔD1 when ΔS, ΔD1, and ΔD2 are the first electric signal, the second electric signal, and the third electric signal in the original mode. -BΔD2 (A, B: coefficient)
Is used to generate the radial tilt signal f. At this time, the coefficient A is the first final coefficient ratio, and the coefficient B is [(the second final coefficient ratio) − (the first final coefficient ratio) × (the third final coefficient ratio)}. It is.

  In the present invention, a radial tilt, an objective lens lens shift, and a signal that fluctuates in the off-track of the light spot are used to calculate the radial shift by subtracting the signal that fluctuates in the objective lens lens shift and the off-track of the light spot by a coefficient. Tilt is detected. For this reason, the radial tilt signal can be detected separately from the influence of the lens shift of the objective lens and the off-track of the light spot, and the detection accuracy of the radial tilt is improved.

  In the present invention, the influence of tilt can be corrected based on the radial tilt signal detected separately from the influence of lens shift of the objective lens and off-track of the light spot. Therefore, stable tilt control of the optical disc apparatus can be realized.

Next, the optical disk apparatus of the present invention will be described with reference to the accompanying drawings.
FIG. 6 is a diagram showing the relationship between the radial tilt detection pattern 7 and the difference signal waveform in the case of the land groove recording method in the optical disc apparatus according to the first embodiment of the present invention. A track is formed in a spiral on the optical disk 14. Thus, there are a plurality of tracks on the optical disk 14. The radial tilt detection pattern 7 is arranged on a plurality of tracks in the radial direction. Further, the radial tilt detection patterns 7 may be arranged at a plurality of locations on the same track.
In the radial tilt detection pattern 7, the land recording track 2 is formed with an extended portion having the same height as the track 2, and the extended portion is formed on both sides of the track 2 so as to form a first cut portion 4 and a second cut portion 5. Partially connected to the recording track. That is, the first cut portion 4 and the second cut portion 5 are connected to the recording track on the right side of the recording track and the recording track on the left side. In other words, an extended portion having the same height as the height of the land recording track 2 is formed on the left and right of the traveling direction of the light spot from the land recording track 2 associated with the radial tilt detection pattern, and is coupled to the left and right recording tracks. Yes.
The first cut portion 4 and the second cut portion 5 are preferably provided close to each other, but cannot be provided at the same position in the traveling direction of the light spot. At least some misalignment is necessary.

  FIG. 2 is a diagram showing the configuration of the optical head device of the optical disk device according to the first embodiment of the present invention. Referring to FIG. 2, the optical head device according to the first embodiment includes a light source 8, a collimator lens 9, a polarizing beam splitter 10, a quarter wave plate 11, a bobbin 12 wound with a coil, an objective lens 13, and a condensing element. A lens 15, a cylindrical lens 16, and a photodetector 17 are provided. The objective lens 13 is inserted into the bobbin 12 and mounted on an actuator (not shown).

  The light emitted from the light source 8 is converted into parallel light by the collimator lens 9 and passes through the polarization beam splitter 10 and the quarter wavelength plate 11. The parallel light is condensed on the optical disk 14 by the objective lens 13. The light reflected on the optical disk 14 passes through the objective lens 13 and is guided in the direction of the photodetector 17 by the quarter wavelength plate 11 and the polarization beam splitter 10. Thereafter, the light passes through the condenser lens 15, is given astigmatism by the cylindrical lens 16, and enters the photodetector 17.

  With reference to FIG. 7, the photodetector 17 includes four photodetectors 18 to 21. The light spot 22 is received by the light detection units 18 to 21 and photoelectrically converted to obtain electrical detection signals V18 to V21, respectively. Since astigmatism is given by the cylindrical lens 16, the light spot 22 extends in the Z1 direction and the X1 direction when the optical disk 14 changes in the positive and negative Z directions. The focus error signal is expressed as {(V18 + V20) − (V19 + V21)} by a known astigmatism method. When the optical disk 14 is placed as shown in FIG. 3, the track error signal is detected as {(V18 + V19)-(V20 + V21)} by a known push-pull method. Although the focus error signal and the track error signal are not shown, the focus error signal and the track error signal are sent to the focus servo and track servo circuits in the subsequent stage, and the objective lens 13 emits light emitted from the objective lens 13 by an actuator (not shown). It is controlled in the Z direction so as to focus on the top, and is controlled in the radial direction so that the light spot 1 is at the center of the track to be recorded or reproduced. The RF signal is detected as (V18 + V19 + V20 + V21). In the present invention, the radial tilt signal is calculated from the sum signal (V18 + V19 + V20 + V21) of the output of the photodetector 17 and the difference signal {(V18 + V19) − (V20 + V21)}. The difference signal is derived as a difference between detection electric signals when the detection unit of the photodetector is divided into two in the radial direction.

  FIG. 6 is a diagram showing the relationship between the radial tilt detection pattern 7 and the difference signal waveform in the case of the land groove recording method in the optical disc apparatus according to the first embodiment of the present invention. Referring to FIG. 6A, the difference signal level of the reflected light when the light spot 1 passes the side of the first cut portion 4 is DA, and the light spot passes the side of the second cut portion 5. DB is the difference signal level of the reflected light when the light is traveling, and ΔD2 is the difference signal level of the reflected light when the light spot 1 is passing between the side of the first cut part 4 and the side of the second cut part 5. To do. When there is no off-track and lens shift, as shown in FIG. 6B, there is no difference between (DA + ΔD2) and (DB−ΔD2). However, when there is an off-track or lens shift, as shown in FIG. 6C, the difference signal difference ΔD1 {= (DA + ΔD2) − (DB−ΔD2) between (DA + ΔD2) and (DB−ΔD2). } Occurs.

  FIG. 3 is a diagram showing the configuration of the radial tilt control unit of the optical disc apparatus according to the first embodiment of the present invention. The radial tilt control unit according to the first embodiment of the present invention is provided in the subsequent stage of the optical head device, and includes a sum signal detection unit 23, a difference signal detection unit 24, a signal storage unit 25, a coefficient ratio calculation unit 26, a control unit 27, A coefficient ratio storage unit 29, a radial tilt calculation unit 30, and a tilt servo unit 31 are provided.

  When the optical disk is being rotated by a rotation drive device (not shown), the control unit 27 responds to an input radial tilt correction command or when the optical disk is set in the optical disk control device, Various instructions are generated to control the driving device based on the detection and the detected radial tilt. The sum signal detector 23 detects a sum signal from the detection signal from the photodetector 17. The difference signal detector 24 detects the difference signal from the detection signal from the photodetector 17. In response to an instruction from the control unit 27, the detected sum signal and difference signal are stored in the signal storage unit 25 as to the track position associated with the radial tilt detection pattern 7 and the position of the radial tilt detection pattern 7 in the circumferential direction. Stored in association. In response to an instruction from the control unit 27, the coefficient ratio calculation unit 26 reads the sum signal and the difference signal from the signal storage unit 25 and determines a coefficient ratio (described in detail below). The determined coefficient ratio is stored in the coefficient ratio storage unit 29 in response to an instruction from the control unit 27. Thereafter, the sum signal and the difference signal detected by the sum signal detection unit 23 and the difference signal detection unit 24 are supplied to the radial tilt calculation unit 30. The radial tilt calculation unit 30 reads the coefficient ratio from the coefficient ratio storage unit 29 in response to an instruction from the control unit 27, and based on the detected sum signal and difference signal and the read coefficient ratio, the radial tilt signal Is output to the tilt servo unit 31. The tilt servo unit 31 controls an actuator (not shown) so as to rotate the bobbin 12 to which the objective lens 13 is attached in response to the radial tilt signal.

  FIG. 4 shows an off-track control unit. In FIG. 4, the optical system of the optical head device shown in FIG. 2 is shown as an optical head 44. The off-track control unit includes the control unit 27, the track servo unit 39, the arithmetic circuit 45, and the optical head 44. The arithmetic circuit 45 calculates a tracking error signal based on the electrical detection signal from the photodetector 17 of the optical head 44 and generates a tracking error signal. Normally, the track servo unit 39 receives a track error signal from the arithmetic circuit 45, and a coil (not shown) wound around the bobbin 12 so that the objective lens 13 is positioned at a position where the track error signal becomes zero. Is controlled in the radial direction. At this time, the light spot 1 is located at the center of the track.

  During off-track control, the track servo unit 39 adds an offset to the track error signal in response to an instruction from the control unit 27 to drive the coil. As a result, the objective lens 13 moves in the radial direction based on the offset, and the light spot 1 is shifted from the center of the track. Thus, the off-track L1 is given to the light spot 1.

  FIG. 5 shows a lens shift control unit. Here, in FIG. 5, the optical system of the optical head device shown in FIG. The optical head 44 is mounted on the carriage 41. The lens shift control unit includes the control unit 27, seek control unit 43, sled servo unit 40, carriage drive motor 42, and carriage 41 on which the optical head 44 is mounted.

  Normally, the sled servo section 40 moves the carriage 41 by the carriage drive motor 42 so as to reach the target track position in the radial direction of the optical disc 14 in response to the seek signal from the seek control section 43. When the carriage 41 is moved to the target track position, focus servo control and track servo control are executed on the objective lens 13. A lens position detector (not shown) separately provided beside the objective lens 13 generates a lens position signal indicating a positional deviation of the objective lens 13 with respect to the carriage 41. The sled servo unit 40 drives the carriage drive motor 42 to move the carriage 41 so that the lens position signal becomes zero. At this time, the objective lens 13 exists at a position where its optical axis coincides with the optical axis of the incident light.

  At the time of lens shift control, the thread servo unit 40 gives an electrical offset to the lens position signal in response to an instruction from the control unit 27 while the focus servo control and the track servo control are performed on the objective lens 13. The carriage 41 is moved. As a result, the carriage 41 is moved in the radial direction so that the optical axis of the objective lens 13 deviates from the optical axis of the incident light, and a lens shift L2 is given to the objective lens 13.

  FIGS. 8 to 10 show the calculation results of the fluctuation of the sum signal difference ΔS and the difference signal difference ΔD1 with respect to the radial tilt of the optical disc 14, the lens shift of the objective lens 13, and the off-track of the light spot 1 in the radial tilt detection method of the present invention. It is a figure which shows an example.

  The radial tilt signal in the prior art does not change depending only on the radial tilt, but also changes due to the lens shift of the objective lens and the off-track of the light spot 1 as shown in FIGS. Therefore, in the conventional optical disc apparatus, when there is a lens shift of the objective lens or off-track of the light spot 1, it is impossible to detect them separately from the radial tilt, and the accuracy of the radial tilt detection is lowered. It was.

In the present invention, even when there is a lens shift of the objective lens or an off-track of the light spot 1, the radial tilt can be detected with high accuracy. The detection method will be described below.
As is apparent from FIGS. 8 to 10, the sum signal difference ΔS representing the difference between the sum signals is approximately proportional to the radial tilt θ, the lens shift ΔL_Lens, and the off-track ΔL_off. Therefore, the sum signal difference ΔS is expressed by the following equation (4).
ΔS = sθ + aΔL_lens + bΔL_off (4)
(S, a, b: coefficients). As is apparent from FIGS. 8 to 10, the difference signal level difference ΔD1 is proportional to the lens shift ΔL_Lens and the off-track ΔL_off and does not depend on the radial tilt θ. Therefore, the difference signal level difference ΔD1 is expressed by the following equation (5).
ΔD1 = cΔL_lens + dΔL_off (5)
(C, d: coefficient). Further, although not shown in FIGS. 8 to 10, the difference signal level ΔD2 in the portion other than the cut portion is proportional only to the off-track ΔL_off and does not depend on the lens shift ΔL_Lens or the radial tilt θ. Therefore, the difference signal level ΔD2 is expressed by the following equation (6).
ΔD2 = eΔl_off (6)
(E: coefficient).

From equations (4), (5), and (6), a pure radial tilt signal f {θ} is obtained using ΔS, ΔD1, and ΔD2,
f (θ) = sθ = ΔS− (a / c) ΔD1 − {(b / e) − (ad / ce) ΔD2
(7)
Is calculated. Here, if A = a / c and B = b / e-ad / ce, then f = ΔS−AΔD1−BΔD2.

  The ratios a / c, b / e, and d / e of coefficients necessary for the calculation of Expression (6) are different depending on the optical disc apparatus and the optical disc 14 used for recording and reproduction. Therefore, when the new optical disk 14 is used in the optical disk apparatus, it is necessary to estimate the above three coefficient ratios for the set of the optical disk 14 and the optical disk apparatus to be used in order to detect the radial tilt. However, once the ratio of the three coefficients is estimated for a certain optical disk 14 and optical disk device combination, it does not vary unless the optical disk 14 is removed from the optical disk device.

Next, a method for determining the coefficient ratios b / e and d / e will be described.
First, the optical disc 14 is placed on the optical disc apparatus, and the optical disc 14 is rotated by a rotation drive unit (not shown). Thereafter, in response to the radial tilt correction command, the control unit 27 sets the original mode. In the original mode, after the optical head is moved to a predetermined first track position, focus servo control and track servo control are executed. When the light spot 1 passes through the radial tilt detection pattern 7, the sum signal detector 23 detects the sum signal difference ΔS, and the difference signal detector 24 detects the difference signal difference ΔD1 and the difference signal ΔD2, respectively. (1), ΔD1 (1), and ΔD2 (1) are stored in the signal storage unit 25. In this state, assuming that the radial tilt is θ (1), the off-track is ΔL_off (1), and the lens shift is ΔL_Lens (1), Equations (4), (5), and (6)
ΔS (1) = sθ (1) + aΔL_lens (1) + bΔL_off (1)
(8)
ΔD1 (1) = cΔL_lens (1) + dΔL_off (1) (9)
ΔD2 (1) = eΔL_off (1) (10)
It is.

Next, the control unit 27 sets an off-track mode, and in response to an instruction from the control unit 27, the off-track control unit shown in FIG. 4 gives the off-track L 1 to the light spot 1. With the off track L1 applied, ΔS is detected by the sum signal detector 23, and the difference signal difference ΔD1 and the difference signal ΔD2 are detected by the difference signal detector 24, which are ΔS (2) and ΔD1 (2 ), ΔD2 (2) and stored in the signal storage unit 25. Therefore,
ΔS (2) = sθ (1) + aΔL_lens (1)
+ B (ΔL_off (1) + L1) (11)
ΔD1 (2) = cΔL_lens (1)
+ D (ΔL_off (1) + L1) (12)
ΔD2 (2) = e (ΔL_off (1) + L1) (13)
It is. In response to an instruction from the control unit 27, the coefficient ratio calculation unit 26 calculates the coefficient ratio by the following procedure using the value stored in the signal storage unit 25.
From equations (8) and (11), b = (ΔS (2) −ΔS (1)) / L1 (14)
From Equations (9) and (12), d = (ΔD1 (2) −ΔD1 (1)) / L1 (15)
From Equations (10) and (13), e = (ΔD2 (2) −ΔD2 (1)) / L1 (16)
From equations (14) and (16), b / e = {ΔS (2) −ΔS (1)} / {ΔD2 (2) −ΔD2 (1)}
(17)
From equations (15) and (16)
d / e = {ΔD1 (2) −ΔD1 (1)} / {ΔD2 (2) −ΔD2 (1)}
(18)
As described above, the coefficient ratios b / e and d / e are determined.

  Note that equations (17) and (18) do not include off-track L1. Therefore, the amount of off-track L1 added for learning is not particularly limited, and the amount of off-track L1 need not be estimated. The sum signal difference ΔS, the difference signal difference ΔD1, and the difference signal ΔD2 may be arbitrarily added to the extent that they change. Further, Expressions (17) and (18) include the radial tilt θ (1), the off-track ΔL_off (1), and the lens shift ΔL_Lens (1) when the optical disc 14 is first placed on the optical disc apparatus. In the state in which the optical disk 14 is first installed in the optical disk apparatus, the ratio of the coefficients can be learned even if there is a radial tilt, off-track, or lens shift.

Next, a method for determining the coefficient ratio a / c will be described. The control unit 27 sets the lens shift mode. In a state where the focus servo control and the track servo control are performed on the objective lens 13, the lens shift control unit shown in FIG. 5 gives the lens track L 2 to the light spot 1 in response to an instruction from the control unit 27. That is, the carriage 41 is moved in the radial direction so that the optical axis of the objective lens 13 is shifted from the optical axis of the incident light, and a lens shift L2 is given to the objective lens 13. With the lens shift L2 applied, the sum signal detector 23 detects the sum signal difference ΔS, the difference signal detector 24 detects the difference signal difference ΔD1, and stores the signals as ΔS (3) and ΔD1 (3). Stored in the unit 25. in this case,
ΔS (3) = sθ (1) + a (ΔL_lens (1) + L2) + bΔL_off (1)
(19)
ΔD1 (3) = c (ΔL_lens (1) + L2) + dΔL_off (1)
(20)
It is.
The coefficient ratio calculation unit 26 calculates the coefficient ratio according to the following procedure.
From equations (8) and (19)
a = (ΔS (3) −ΔS (1)) / L2 (21)
From equations (8) and (20)
c = (ΔD1 (3) −ΔD1 (1)) / L2 (22)
From equations (21) and (22)
a / c = {ΔS (3) −ΔS (1)}
/ {ΔD1 (3) −ΔD1 (1)} (23)
As described above, the coefficient ratio a / c is determined.

  Note that the lens shift L2 is not included in Expression (23). Accordingly, the lens shift amount L2 given for learning is not particularly limited, and the lens shift amount L2 need not be estimated. The sum signal difference ΔS and the difference signal difference ΔD1 may be arbitrarily given to the extent that they change. Further, Expression (23) does not include the radial tilt θ (1), the off-track ΔΔL_off (1), and the lens shift ΔΔL_Lens (1) when the optical disc 14 is first placed on the optical disc apparatus. In the state in which the optical disk 14 is initially placed on the optical disk device, the ratio of the coefficients can be learned even if there is radial tilt, off-track, and lens shift.

When the coefficient ratios b / e and d / e are first determined in the off-track mode and then the coefficient ratio a / c is determined in the lens shift mode, the coefficient ratio a / c is determined in the subsequent process. Using the determined coefficient ratios b / e and d / e, signals ΔDS1 and ΔDS2 obtained by converting the sum signal difference ΔS, difference signal difference ΔD1, and difference signal ΔD2 as follows may be used.
ΔS− (b / e) ΔD2 = sθ + aΔL_lens = ΔDS1
(24)
ΔD− (d / e) ΔD2 = cΔL_lens = ΔDS2 (25)

The coefficient ratio a / c in this case is ΔDS1 and ΔDS2 before the lens shift is given, ΔDS1 (4) and ΔDS2 (4), ΔDS1 and ΔDS2 after the lens shift is given, ΔDS1 (5), Assuming ΔDS2 (5),
a / c = {ΔDS1 (5) −ΔDS1 (4)}
/ {ΔDS2 (5) −ΔDS2 (4)} (26)
Given in. The ΔDS1 and ΔDS2 are signals that do not depend on the off-track ΔL_off. Therefore, by using the above-described ΔDS1 and ΔDS2, the coefficient ratio a / c can be obtained even if off-track occurs erroneously when controlling the lens shift.

A process of determining a coefficient ratio and calculating a radial tilt signal in the optical disc apparatus according to the first embodiment of the present invention will be described.
As described above, the optical disc 14 has a plurality of radial tilt detection patterns 7 arranged in one circle. In the process of determining the coefficient ratio and calculating the radial tilt signal, the light spot 1 tracks to the inner peripheral side of the optical disk 14 so that the spiral optical disk 14 always follows the same land recording track 2 after one rotation. Jumped. However, this operation is not necessary when the tracks are formed concentrically.

  First, in the first rotation of the optical disk 14, in response to an instruction from the control unit 27, the sum signal difference ΔS (1), difference signal difference ΔD1 (1), and the like in each radial tilt detection pattern 7 in the periphery, The difference signal ΔD2 (1) is detected and stored in the signal storage unit 25 in relation to the track position and the position in the circumference of the detection pattern. Subsequently, in the second round of rotation of the optical disc 14, an off-track L1 is electrically supplied in response to an instruction from the control unit 27, and each radial tilt detection pattern in the circumference is the same as in the first round. 7, the sum signal difference ΔS (2), the difference signal difference ΔD 1 (2), and the difference signal ΔD 2 (2) are detected and stored in the signal storage unit 25 in relation to the track position of the detected pattern and the position within the circumference. The After the above signals are detected in all the radial tilt detection patterns 7 within one turn, the coefficient ratio calculation unit 26 responds to an instruction from the control unit 27 and the ΔS (1 at the position of each radial tilt detection pattern 7 ), ΔD1 (1), ΔD2 (1) and ΔS (2), ΔD1 (2), ΔD2 (2) are used to determine the coefficient ratios b / e and d / e by the above method, and all radials in the circumference are determined. Average over the tilt detection pattern 7. Thus, the averaged coefficient at the track position is obtained. The averaged coefficient is stored in the coefficient ratio storage unit 29 in response to an instruction from the control unit 27.

  The coefficients b / e and d / e do not include the off-track L1 itself given from outside for learning. Therefore, the off-track L1 given to the second round may vary during the rotation of the optical disk 14 once.

  In response to an instruction from the control unit 27 on the third rotation of the optical disk 14, the off-track L1 is returned to the original value, and ΔS (1), ΔD1 ( 1) and ΔD2 (1) are detected again and stored in the signal storage unit 25 in association with the track position and the position in the circumference of the detected pattern.

  In response to an instruction from the control unit 27 on the fourth turn of the rotation of the optical disk 14, for example, while track servo control is being executed, the carriage of the optical head device is moved in the radial direction, and the objective lens has a lens. A shift L2 is given. Therefore, ΔS (3), ΔD1 (3), and ΔD2 (3) are detected in each radial tilt detection pattern 7 in the circumference, and in response to an instruction from the control unit 27, the track position and the circumference of the detection pattern are detected. Is stored in the signal storage unit 25 in relation to the position in After the above signals are detected in all the radial tilt detection patterns 7 in one turn, in response to an instruction from the control unit 27, the coefficient ratio calculation unit 26 calculates ΔS (1), The coefficient ratio a / c is determined by the above method from ΔD1 (1), ΔD2 (1) and ΔS (3), ΔD1 (3), ΔD2 (3), and all radial tilt detection patterns 7 in the circumference are covered. Average. In this way, the averaged coefficient ratio a / c is determined. The determined average coefficient a / c is stored in the coefficient ratio storage unit 29 in association with the track in response to an instruction from the control unit 27.

The coefficient ratio a / c does not include the lens shift L2 itself given from outside for learning. Therefore, the lens shift L2 given to the fourth turn may vary during one rotation of the disk.
After the fifth rotation of the rotation of the optical disc 14, the lens shift L2 is returned to the original value, and a radial tilt signal is calculated in response to an instruction from the control unit 27. The pure radial tilt signal is calculated by the radial tilt calculator 30. Specifically, the sum signal difference ΔS detected by the sum signal detection unit 23, the values of the difference signal difference ΔD1 and the difference signal ΔD2 detected by the difference signal detection unit 24, and the coefficient ratio storage unit 29 are stored. Using the coefficient ratios a / c, b / e, and d / e, the radial tilt signal is calculated by the above equation (7). The calculated radial tilt signal f (θ) is sent to the tilt servo unit 31. The tilt servo unit 31 tilts the objective lens 13 in the direction of arrow A by an actuator (not shown) so that the calculated radial tilt signal becomes zero, and the influence of the relative tilt between the optical disc 14 and the objective lens 13 is achieved. Correct.

  If the correction of the radial tilt is executed at a plurality of track positions in the radial direction of the optical disc, the tilt of the optical disc can be corrected with higher accuracy.

  In the present embodiment, the cylindrical lens 16 is used to give astigmatism to the reflected light from the optical disk 14, but a parallel plate inclined with respect to the optical axis may be used. In addition, a compound lens combining the functions of the condenser lens 15 and the cylindrical lens 16 may be used.

  In this embodiment, the astigmatism method is used to detect the focus error signal, but another focus error signal detection method such as a knife edge method may be used. Further, it is possible to use a method in which reflected light from the optical disk is separated by a hologram element or the like, and a focus error signal, a track error signal, and an RF signal are independently detected by the separated light.

  Furthermore, in the present embodiment, all of the error signal, the RF signal, and the tilt signal are detected only by the photodetector 17, but a half-wave plate and a polarizing beam splitter are disposed in front of the condenser lens 15. Thus, the reflected light from the optical disk 14 may be separated into two, an error signal may be detected with one light, and an RF signal and a tilt signal may be detected with the other light.

  Further, the lens shift L2 is given to the objective lens 13 in the second round of rotation of the optical disc 14, and the coefficient ratio a / c is determined. In the fourth round, the off-track L1 of the light spot 1 is given and the coefficient ratio b / e and d / e may be determined. Further, if there is no difference between the lens shift of the objective lens 13 and the off-track of the light spot 1 in the first and third rotations of the optical disk 14, the third rotation of the optical disk 14 is performed for speeding up. The process of detecting ΔS (1), ΔD1 (1), and ΔD2 (1) again may be omitted. Also, the coefficient ratio a / c may be determined using the signals ΔDS1 and ΔDS2 defined by the above equations (24) and (25).

  Further, in order to correct the influence of the relative tilt between the optical disk 14 and the objective lens 13, the entire optical head device including the objective lens 13 may be tilted by a motor. The optical disk 14 may be tilted. Furthermore, a liquid crystal element that applies wavefront aberration so as to cancel out aberration generated by radial tilt may be installed inside the optical head device.

Further, the radial tilt detection pattern 7 shown in FIGS. 1 and 6 is merely an example. The positions of the first cut part 4 and the second cut part 5 may be reversed. Moreover, as long as the position of the 1st cut part 4 and the 2nd cut part 5 has not overlapped, a part of position of the 1st cut part 4 and the 2nd cut part 5 may overlap.
Further, the difference signal difference ΔD1 may be replaced with a signal representing the radial position of the objective lens 13 such as an output from a lens position detector separately provided beside the objective lens 13.
Further, the difference signal ΔD <b> 2 may be detected not on the first cut part 4 and the second cut part 5 but on the left side of the first cut part 4 or the right side of the second cut part 5.

  The present invention can also be applied to a groove recording type optical disc. FIG. 11 is a diagram showing a radial tilt detection pattern in the groove recording method. Referring to FIG. 11, in the case of the groove recording method, the radial tilt detection pattern 34 has a groove of one groove recording track and a groove of the groove recording track 3 out of two groove recording tracks adjacent to the target groove recording track 3. And a second coupling portion 33 in which the groove of the other groove recording track and the groove of the groove recording track 3 are partially coupled. By adopting such a configuration, it is possible to detect a signal similar to the radial tilt signal f (θ) in the land / groove recording method.

  Furthermore, the present invention can also be applied to ROM optical disks. FIG. 12 is a diagram showing a radial tilt detection pattern on the ROM optical disc. In the case of a ROM optical disc, the radial tilt detection pattern 38 includes a portion of a pit on one recording track and a long pit on the recording track 35 out of two recording tracks adjacent to the recording track 35 formed by a pit row. The first coupling portion 36 is disposed in a coupled manner, and the second coupling portion 37 is disposed in such a manner that a pit on the other recording track and a long pit on the recording track 35 are partially coupled. By adopting such a configuration, it is possible to detect a signal similar to the radial tilt signal f (θ) in the land / groove recording method.

  According to the present invention, the signal that fluctuates due to the radial tilt, the lens shift of the objective lens, and the light spot off-track is subtracted by multiplying the signal that fluctuates by the objective lens lens shift and the light spot off-track by a coefficient. Therefore, a pure radial tilt signal can be detected separately from the influence of the lens shift of the objective lens and the off-track of the light spot, and the detection accuracy of the radial tilt is improved.

  In addition, according to the present invention, since tilt control is performed based on the radial tilt signal separated from the effect of lens shift of the objective lens and off-track of the light spot, stable tilt control of the optical disc apparatus can be realized.

FIG. 1 is a diagram showing a relationship between a radial tilt detection pattern and a sum signal waveform in a conventional optical disc. FIG. 2 is a block diagram showing a configuration of the optical head device in the optical disc apparatus according to the embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the radial tilt control unit in the optical disc apparatus according to the embodiment of the present invention. FIG. 4 is a block diagram showing a configuration of the off-track control unit in the optical disc apparatus according to the embodiment of the present invention. FIG. 5 is a block diagram showing a configuration of the lens shift control unit in the optical disc apparatus according to the embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the radial tilt detection pattern and the difference signal waveform in the optical disc of the present invention. FIG. 7 is a diagram showing a light receiving unit and a light spot of the photodetector 17 in the optical disc apparatus according to the embodiment of the present invention. FIG. 8 is a diagram illustrating an example of calculation results of fluctuations in the sum signal difference ΔS and the difference signal difference ΔD1 with respect to the radial tilt of the optical disc. FIG. 9 is a diagram illustrating an example of a calculation result of fluctuations in the sum signal difference ΔS and the difference signal difference ΔD1 with respect to the lens shift of the objective lens. FIG. 10 is a diagram illustrating an example of calculation results of fluctuations in the sum signal difference ΔS and the difference signal difference ΔD1 with respect to the off-track of the light spot. FIG. 11 is a diagram showing a radial tilt detection pattern in the case of the groove recording method. FIG. 12 is a diagram showing a radial tilt detection pattern on the ROM optical disc.

Explanation of symbols

1: Light spot 2: Land recording track 3: Groove recording track 4: First cut portion 5: Second cut portion 6: Radial tilt signal 7: Radial tilt detection pattern 8: Light source 9: Collimator lens 10: Polarizing beam splitter 11 : 1/4 wavelength plate 12: Bobbin 13: Objective lens 14: Optical disk 15: Condensing lens 16: Cylindrical lens 17: Photo detector 18-21: Photo detector 22: Light spot 23: Sum signal detector 24: Difference Signal detection unit 25: signal storage unit 26: coefficient ratio calculation unit 27: control unit 29: coefficient ratio storage unit 30: radial tilt calculation unit 31, tilt servo unit 32: first coupling unit 33: second coupling unit 34: radial tilt Detection pattern 35: recording track 36: first coupling portion 37: second coupling portion 38: radial tilt detection pattern 39: tracking servo section 40: sled servo unit 41: Carriage 42: Carriage drive motor 43: seek control unit 44: optical head 45: arithmetic circuit

Claims (15)

(A) rotating the optical disc; forming a light spot on the optical disc via an objective lens; and the optical disc includes a first track, and detecting at least one radial tilt in relation to the first track. Pattern is provided,
(B) An original mode when the light spot is positioned on the first track, an off-track mode in which off-track is given to the light spot in the original mode, and a lens shift in the objective lens in the original mode. Setting a given lens shift mode;
(C) In each of the original mode, the off-track mode, and the lens shift mode, reflection from the radial tilt detection pattern through the objective lens when the light spot scans the first track. Generating a first to a third electrical signal from an optical signal, the first electrical signal depends on a radial tilt, a lens shift, and off-track of the optical disc, and the second electrical signal is the radial It does not depend on tilt, depends on the lens shift and the off-track, and the third electrical signal depends only on the off-track,
(D) calculating a plurality of coefficient ratios as a ratio of a difference between the first to third electrical signals in the lens shift mode to the off-track mode and the first to third electrical signals in the original mode; Calculating a set of final coefficient ratios from a plurality of coefficient ratios, and detecting a radial tilt using the set of final coefficient ratios;
And (e) correcting the influence of the radial tilt based on the detected radial tilt. (F) By irradiating a rotating optical disc with a light spot, first to third electric signals are generated from reflected light signals from at least one radial tilt detection pattern provided in association with the first track of the optical disc. And the first electric signal depends on the radial tilt, lens shift, and off-track of the optical disc, and the second electric signal does not depend on the radial tilt, and the lens shift and off-track. And the third electrical signal depends only on the off-track,
(G) A mode in which the light spot is positioned on the first track is referred to as an original mode, a mode in which off-track is given to the light spot in the original mode is referred to as an off-track mode, and the objective lens is applied to the objective lens in the original mode. When a lens shift mode is defined as a lens shift mode, the first to third electrical signals in the lens shift mode to the off-track mode and the first to third electrical signals in the original mode Calculating a plurality of coefficient ratios as a ratio to the difference, calculating a set of final coefficient ratios from the plurality of coefficient ratios, and detecting a radial tilt using the set of final coefficient ratios;
And (h) correcting the influence of the radial tilt based on the detected radial tilt. In the optical disk control method according to claim 1 or 2,
The radial tilt detection pattern includes the first portion including an extended portion provided in an inner circumferential direction from the first track, and the second portion including an extended portion provided in an outer peripheral direction from the first track; An optical disc control method comprising the first portion and the third portion other than the second portion. In the optical disk control method according to claim 3,
The optical disc control method, wherein the extended portion of each of the first portion and the second portion has the same height as the first track. In the optical disk control method according to any one of claims 1 to 4,
Before Kisei formation step,
When the sum electric signal of the electric signal components detected from the reflected light is a sum signal, the light spot is the radial tilt detection pattern in each of the original mode, the off-track mode, and the lens shift mode. Generating the first electrical signal as a difference between the sum signal when it passes through the first portion and the sum signal when the light spot passes through the second portion;
When the difference between two electrical signals obtained by dividing the reflected light into two in the radial direction is used as a difference signal, the light spot in each of the original mode, the off-track mode, and the lens shift mode is Generating the second electrical signal as a difference between the difference signal when it passes through the first portion and the difference signal when the light spot passes through the second portion;
Generating the third signal as the difference signal when the light spot passes through the third portion. An optical disc control method. The optical disk control method according to claim 4,
One radial tilt detection pattern is provided in relation to the first track,
The set of final coefficient ratios includes first to third final coefficient ratios;
The detection step (d) or (g) includes:
The ratio of the difference between the first electrical signal in the lens shift mode and the first electrical signal in the original mode and the difference between the second electrical signal in the lens shift mode and the second electrical signal in the original mode. Calculating a first coefficient ratio as:
The difference between the first electrical signal in the off-track mode and the first electrical signal in the original mode, and the difference between the third electrical signal in the off-track mode and the third electrical signal in the original mode. Calculating a second coefficient ratio as a ratio;
The ratio of the difference between the second electrical signal in the off-track mode and the second electrical signal in the original mode and the difference between the third electrical signal in the off-track mode and the third electrical signal in the original mode. Calculating a third coefficient ratio as:
Holding the first to third coefficient ratios as the first to third final coefficient ratios. An optical disc control method. The optical disk control method according to claim 5, wherein
A plurality of the radial tilt detection patterns are provided in relation to the first track,
The set of final coefficient ratios includes first to third final coefficient ratios;
The detection step (d) or (g) includes:
In each of the plurality of radial tilt detection patterns, a difference between the first electric signal in the lens shift mode and the first electric signal in the original mode, the second electric signal in the lens shift mode, and the original mode. Calculating a first coefficient ratio as a ratio to a difference from the second electrical signal;
In each of the plurality of radial tilt detection patterns, the difference between the first electrical signal in the off-track mode and the first electrical signal in the original mode, the third electrical signal in the off-track mode, and the original mode Calculating a second coefficient ratio as a ratio to a difference from the third electrical signal;
In each of the plurality of radial tilt detection patterns, the difference between the second electric signal in the off-track mode and the second electric signal in the original mode, the third electric signal in the off-track mode, and the original mode Calculating a third coefficient ratio as a ratio to a difference from the third electrical signal;
Averaging each of the first to third coefficient ratios over the plurality of radial tilt detection patterns;
Holding the averaged first to third coefficient ratios as the first to third final coefficient ratios. An optical disc control method. In the optical disk control method according to claim 6 or 7,
The detection step (d) or (g) includes:
When the first electric signal, the second electric signal, and the third electric signal in the original mode are ΔS, ΔD1, and ΔD2, the following formulas f = ΔS−AΔD1−BΔD2 (A, B: coefficients)
Detecting the radial tilt f using
The coefficient A is the first final coefficient ratio, and the coefficient B is {(the second final coefficient ratio) − (the first final coefficient ratio) × (the third final coefficient ratio)}. Control method. A rotation drive unit for rotating the optical disc, and the optical disc includes a first track, and at least one radial tilt detection pattern is provided in association with the first track;
A control unit for setting an original mode, an off-track mode, and a lens shift mode;
An optical system having an objective lens, forming a light spot on the optical disc through the objective lens, and generating an electrical signal from a reflected light signal from the radial tilt detection pattern through the objective lens;
A lens position control unit that controls the optical system to position the light spot on the first track in response to a seek command and applies a lens shift to the objective lens in response to a lens shift command from the control unit When,
An off-track control unit that controls an error in a radial direction of the light spot on a track, and gives off-track to the light spot in response to an off-track command from the control unit;
In response to a tilt signal generation instruction, first to third electrical signals are generated from the electrical signals from the optical system in each of the original mode, the off-track mode, and the lens shift mode, and the lens shift mode to A plurality of coefficient ratios are calculated as a ratio of a difference between the first to third electrical signals in the off-track mode and the first to third electrical signals in the original mode, and a final coefficient ratio is calculated from the plurality of coefficient ratios. A calculation unit that generates a radial tilt signal using the final coefficient ratio set; and
A tilt control unit that corrects the influence of the radial tilt in response to the radial tilt signal;
The control unit controls the off-track control unit to control the position of the light spot on the first track in the original mode, and generates the first to third electric signals in the original mode. The off-track command is output to the off-track control unit in the off-track mode, and the off-track control unit is controlled to generate the first to third electrical signals in the off-track mode. And outputting the lens shift command to the lens position control unit in the lens shift mode, controlling the calculation unit to generate the first to third electric signals in the lens shift mode, Outputting the tilt signal generation instruction to the arithmetic unit;
The first electrical signal depends on the radial tilt, lens shift, and off-track of the optical disc, and the second electrical signal does not depend on the radial tilt, and depends on the lens shift and off-track. The third electrical signal depends only on the off-track optical disc apparatus. The optical disc apparatus according to claim 9, wherein
The radial tilt detection pattern includes the first portion including an extended portion provided in an inner circumferential direction from the first track, and the second portion including an extended portion provided in an outer peripheral direction from the first track; An optical disc apparatus comprising the first portion and the third portion other than the second portion. The optical disk apparatus according to claim 10, wherein
The extended portion of each of the first portion and the second portion has the same height as the first track. The optical disc apparatus according to any one of claims 9 to 11,
The computing unit is
When the sum of the electrical signal components detected from the reflected light signal is a sum signal, the light spot is the radial tilt detection pattern in each of the original mode, the off-track mode, and the lens shift mode. A sum signal detector that generates the first electric signal as a difference between the sum signal when the first portion of the light signal passes through the second portion and the sum signal when the light spot passes through the second portion;
When the difference between two electrical signals obtained by dividing the reflected light into two in the radial direction is used as a difference signal, the light spot in each of the original mode, the off-track mode, and the lens shift mode is The second electrical signal is generated as a difference between the difference signal when the first portion passes and the difference signal when the light spot passes the second portion, and the light spot is the third portion. An optical disc apparatus comprising: a difference signal detection unit that generates the third signal as the difference signal when the signal passes through the optical disc. The optical disk device according to claim 12, wherein
One radial tilt detection pattern is provided in relation to the first track,
The computing unit is
A coefficient ratio calculation unit for calculating a set of coefficient ratios from the first to third electrical signals in each of the original mode, the off-track mode, and the lens shift mode with respect to the single radial tilt detection pattern;
A coefficient ratio storage for storing the set of calculated coefficient ratios as the set of final coefficient ratios;
An optical disc apparatus comprising: a radial tilt calculation unit that generates the radial tilt signal from a set of the first to third electrical signals and the final coefficient ratio in the original mode. The optical disk apparatus according to claim 12, wherein
A plurality of the radial tilt detection patterns are provided in relation to the first track,
The computing unit is
A coefficient ratio storage unit;
For the plurality of radial tilt detection patterns, a set of coefficient ratios is calculated from the first to third electric signals in each of the original mode, the off-track mode, and the lens shift mode, and stored in the coefficient ratio storage unit. When the calculation of the coefficient ratio set from the plurality of radial tilt detection patterns is completed, the corresponding coefficient ratio is averaged over the plurality of radial tilt detection patterns, and the set of average coefficient ratio is set to the final A coefficient ratio calculation unit that stores the coefficient ratio as a set in the coefficient storage unit;
An optical disc apparatus comprising: a radial tilt calculation unit that generates the radial tilt signal from a set of the first to third electrical signals and the final coefficient ratio in the original mode. The optical disc apparatus according to claim 13 or 14,
The radial tilt calculator is
When the first electric signal, the second electric signal, and the third electric signal in the original mode are ΔS, ΔD1, and ΔD2, the following formulas f = ΔS−AΔD1−BΔD2 (A, B: coefficients)
The radial tilt signal f is generated using
The coefficient A is the first final coefficient ratio, and the coefficient B is {(the second final coefficient ratio).
-(The first final coefficient ratio) x (the third final coefficient ratio)}.

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