JP2000357338A - Device for driving recording medium and detection of tilt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to detect tilt amount without disposing an exclusive sensor. SOLUTION: This optical disk reproducing device 10 is provided with an optical pickup 11 which has an objective lens 18 irradiating the optical disk with a laser beam and reads out digital data recorded on the optical disk, a sensor output detecting circuit 14 which detects the position of the objective lens 18 in a direction of focus in the focus driving of the optical pickup 11 with respect to the optical disk and a tilt detecting circuit 16 which detects a tilt indicating value. The optical disk reproducing device 10 detects a displacement amount between the reference position which is the position of the objective lens 18 which is detected in the focusing of the objective lens 18 on the reference disk and the position of the objective lens 18 which is detected in the focusing of the objective lens 18 on the optical disk to be reproduced, and, in accordance with the displacement amount, the tilt indicating value is calculated by the tilt detecting circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium drive for rotating a disc-shaped recording medium to record and / or reproduce digital data on the disc-shaped recording medium, and to rotate the disc-shaped recording medium. The present invention relates to a tilt detection method for detecting a tilt amount generated at the time.

[0002]

2. Description of the Related Art For example, optical disks such as so-called CDs (Compact Disks) and DVDs (Digital Versatile Disks) are widely known as recording media for optically recording digital data.

An optical disk drive for recording and / or reproducing digital data on and from such an optical disk has a small spot where a laser beam is condensed by an optical pickup on a rotationally driven optical disk at a desired position. Irradiate and record and / or reproduce digital data. At this time, in order to stably record digital data on the optical disk or to faithfully reproduce the digital data recorded on the optical disk, the optical pickup makes the laser beam follow a track provided on the surface of the optical disk. Operate.

[0004]

Incidentally, in the above-mentioned optical disk, warpage and eccentricity of the optical disk due to environmental influences such as temperature and humidity during use and / or storage and handling conditions, and optical pickup of an optical disk drive device. Radial tilt may occur due to the tilt. Since this tilt causes an aberration in the reproduction optical spot, distortion of the reproduction signal and MTF (Mo
It is known that this causes a decrease in dulation transfer function) and a decrease in recording power efficiency.

In recent years, in order to increase the density of an optical disk, a numerical aperture (numerical aperture) of an objective lens in an optical pickup has been used in an optical disk drive.
e; NA) tends to be increased. For example, an objective lens having an NA value of 0.45 for a CD and an NA value of 0.60 for a DVD is used. Along with this, the thickness of the substrate of the optical disk has been reduced. Therefore, the optical disk is likely to be warped and has a large NA, so that the angle dependence of aberration is also increasing, and the tilt is likely to occur at present.

On the other hand, in an optical disk drive, a dedicated sensor is provided to detect a tilt amount in order to compensate for the tilt, and an objective lens, an actuator and the like in an optical pickup are tilted based on the detected signal. Has been put to practical use.

However, in the conventional optical disk drive, if the optical disk has a small diameter, a place for installing a sensor for detecting the amount of tilt cannot be sufficiently secured, and it is difficult to detect the amount of tilt. there were.

The present invention has been made in view of such circumstances, and solves the problem of the tilt detection method in the conventional optical disk drive, and provides a tilt without providing a dedicated sensor for detecting the amount of tilt. It is an object of the present invention to provide a recording medium driving device for detecting an amount and a tilt detection method.

[0009]

According to the present invention, there is provided a recording medium driving apparatus for rotating a disk-shaped recording medium to record and / or reproduce digital data on the disk-shaped recording medium. A lens for irradiating the disc-shaped recording medium with laser light, and a position detecting means for detecting the position of the lens when the lens is focused on the disc-shaped recording medium. And a tilt detecting means for detecting a tilt instruction value based on the position of the lens detected by the position detecting means.

The recording medium driving apparatus according to the present invention detects the position of a lens that irradiates a laser beam to a disk-shaped recording medium, and detects a tilt instruction value based on the position of the lens.

The tilt detecting method according to the present invention for achieving the above object detects the lens position when the lens for irradiating a laser beam onto a disk-shaped recording medium is focused, and detects the detected lens. Is characterized in that the tilt instruction value is detected based on the position.

In the tilt detecting method according to the present invention, the tilt instruction value is detected based on the position of the lens that irradiates the disk-shaped recording medium with laser light.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In this embodiment, a recording medium drive according to the present invention is used for a CD (Compact Disk) or a DVD, for example.
This is an optical disk reproducing apparatus for reproducing digital data from an optical disk which is a disk-shaped recording medium on which digital data is recorded, such as a (Digital Versatile Disk) and an MD (Mini Disk, trade name of Sony Corporation).

An optical disk reproducing apparatus 10 shown in FIG. 1 includes an optical pickup 11 as optical pickup means for reading digital data recorded on an optical disk (not shown), and a signal output from the optical pickup 11 being supplied with a current-voltage signal. An IV conversion circuit 12 for conversion (IV conversion), a servo circuit 13 for tracking the optical pickup 11 so as to maintain a constant distance from the optical disk, and controlling a rotation driving operation of a spindle motor (not shown), and an optical pickup 11 A sensor output detection circuit 14 which is a position detection means for detecting the position of the objective lens 18 based on a detection signal from a position detection unit 20 which is a sensor having the same; Equalizer 15 which is a waveform equalizing means for performing Comprising a tilt detection circuit 16 is a tilt detection means for performing an amount such as detection, and a tilt drive circuit 17 performs control for driving the actuator 19 of the optical pickup 11 for tilt compensation.

The optical pickup 11 comprises an objective lens 18 for condensing laser light from a laser diode 21 and an actuator 1 for driving the objective lens 18 by electromagnetic force.
9, a position detector 20 for detecting the position of the objective lens 18 in the focus direction, a laser diode (LD) 21 for emitting a laser beam, and the laser diode 21
A prism 22 that transmits the laser light emitted from the optical disk and internally reflects the return light reflected and diffracted on the optical disk surface;
Photodiode (PD) 2 for receiving return light reflected and diffracted on the optical disk surface and incident by prism 22
And 3.

The objective lens 18 includes a laser diode 21
From the laser beam and irradiates the optical disk (not shown).

The actuator 19 has a coil, a magnet and the like, and drives the objective lens 18 by electromagnetic force in order to track the objective lens 18 to a desired position on an optical disk (not shown).

The position detecting section 20 is a sensor attached to the actuator 19 for detecting the position of the objective lens 18 in the focusing direction. The position detection unit 20
The detection signal is output to a sensor output detection circuit 14 described later.

The laser diode 21 has, for example, a light emitting portion formed of a semiconductor laser, and emits laser light. The laser light emitted from the laser diode 21 enters the prism 22.

The prism 22 receives and transmits the laser light emitted from the laser diode 21 and
8 and return light reflected and diffracted on the surface of the optical disk is incident and internally reflected, and the photodiode 2
Emitted to 3.

The photodiode 23 has a photodetector and a photoelectric conversion unit, receives the return light reflected and diffracted on the surface of the optical disk and made incident by the prism 22, converts the light into an electric signal, and outputs the electric signal to the IV conversion circuit 12 at the subsequent stage. I do.

The optical pickup 11 irradiates a laser beam emitted from the laser diode 21 onto an optical disc (not shown) and receives return light reflected and diffracted on the surface of the optical disc, thereby recording on a track on the surface of the optical disc. Read out the digital data.

The IV conversion circuit 12 includes the photodiode 2
3 is subjected to current-voltage conversion. The IV conversion circuit 12 converts the signal obtained by the conversion into a servo circuit 13 in the subsequent stage.
Output to Further, the IV conversion circuit 12 converts the RF (Radio Frequency) signal obtained by the conversion into an equalizer 15 at a subsequent stage.
Output to

The servo circuit 13 drives the optical pickup 11 based on the signal supplied from the IV conversion circuit 12 so as to focus the optical pickup 11 so as to keep the distance from the optical disk constant, and controls the rotation driving operation of a spindle motor (not shown). I do.

The sensor output detection circuit 14 includes the position detection unit 2
0 based on the detection signal supplied from the
Is detected in the focus direction. The sensor output detection circuit 14 outputs a detection signal indicating the result of detecting the position of the objective lens 18 to the subsequent tilt detection circuit 16.

The equalizer 15 receives the RF signal from the IV conversion circuit 12 and performs, for example, a waveform equalization process for correcting a jitter error of the RF signal. This equalizer 15
Adjusts the gain based on a tilt error signal supplied from a tilt detection circuit 16 to be described later, and adjusts the MTF (Modula
Compensation for lowering of Transfer Function).

The tilt detection circuit 16 includes, for example, a CPU (Ce
and a tilt instruction value indicating the amount of tilt based on the detection signal output from the sensor output detection circuit 14, as described later. Further, the tilt detection circuit 16 generates a tilt drive circuit 1 described later based on a tilt error signal indicating the calculated tilt instruction value.
7 is generated and supplied to the tilt drive circuit 17. Further, the tilt detection circuit 16
Supplies the detected tilt error signal to the equalizer 15.

The tilt drive circuit 17 generates a control signal based on the drive signal supplied from the tilt detection circuit 16, and the optical pickup 1 moves in a direction to compensate for the tilt.
The first actuator 19 is driven.

A method of detecting tilt in the optical disk reproducing apparatus 10 will be described with reference to FIGS.

In the optical disk reproducing apparatus 10, generally, an optical pickup 11 is controlled by a servo circuit 13 in order to focus an objective lens 18 on the optical disk.
When the optical disk is driven to focus on the optical disk, the position (height) of the objective lens 18 is changed to the position (height) of the optical disk.
Is located at a certain position (height) determined to follow the following.

Therefore, in the optical disk reproducing apparatus 10, as shown in FIG. 2, a reference disk 30, which is a reference disk-shaped recording medium having no tilt, is inserted into the disk holding section 3.
3 and 34, and the servo circuit 13
1 to rotate the reference disk 30 via the rotating shaft 32, and at the same time, the optical pickup 11 is driven to focus on the reference disk 30 by the servo circuit 13, and the reference disk 3 of the objective lens 18 is driven.
The position with respect to 0 is detected by the position detection unit 20. In the optical disk reproducing device 10, the position of the objective lens 18 on the reference disk 30 is detected by outputting a detection signal detected by the position detection unit 20 to the sensor output detection circuit 14. In the optical disc reproducing apparatus 10, the objective lens 1 on the reference disc 30 is used.
The detection signal indicating the position 8 is supplied to the tilt detection circuit 16 and stored in a storage unit (not shown) as a reference position.

Then, in the optical disk reproducing apparatus 10, as shown in the figure, an optical disk 30 'from which digital data is to be reproduced is held by the disk holding sections 33 and 34 in the same manner as the reference disk 30, and a servo circuit is provided. The motor 13 is driven by the motor 13 to rotate the motor 31 via the rotary shaft 32.

Here, it is assumed that the optical disc 30 'has a certain curvature and tilts downward in the height direction, as indicated by the dashed line in FIG. Further, the distance in the radial direction of the optical disk 30 'from the disk holding portion 33 to the measurement point is defined as r.

At this time, in the optical disk reproducing apparatus 10, when the optical pickup 11 is driven to focus on the optical disk 30 'by the servo circuit 13, the objective lens 18' is located lower than the case of the reference disk 30. . In the optical disk reproducing device 10, the position of the objective lens 18 'on the optical disk 30' is detected by the position detecting section 20 and supplied to the tilt detecting circuit 16, thereby detecting the displacement T from the reference position.

Here, as shown in FIG. 3, there is a distance R between the center of the arc presented by the optical disc 30 'and the reference position and a center angle に 対 す る with respect to the arc, which is represented by the detected displacement T, the distance r, and the tilt. , R / R = sinΘ (1) R (1-cosΘ) = T (2) Therefore, the central angle Θ is expressed as follows from the above equations (1) and (2): Θ = sin ⁻¹ {2rT / (r ² + T ² )} (3)

Further, although not shown, when the optical disk 30 'is tilting occurs downwards straight or linear approximation capable and height direction without a curvature, the center angle theta, theta = tan ^{- 1} (T / r) (4)

In the optical disk reproducing apparatus 10, the tilt detection circuit 16 calculates the central angle Θ using the above equation (3) or (4). The center angle Θ is nothing but a tilt angle, and the tilt detection circuit 16 obtains the center angle Θ as a tilt instruction value.

In the optical disk reproducing apparatus 10, a drive signal for driving the tilt drive circuit 17 is generated by the tilt detection circuit 16 based on the tilt error signal indicating the calculated tilt instruction value and supplied to the tilt drive circuit 17. I do. The tilt drive circuit 17 controls and drives the optical pickup 11 based on the drive signal so that the tilt instruction value approaches “0”.

Further, in the optical disk reproducing apparatus 10, a tilt error signal is supplied to the equalizer 15 by the tilt detecting circuit 16, and the equalizer 15 adjusts the gain based on the tilt error signal to compensate for the decrease in MTF.

Further, in the optical disk reproducing apparatus 10, the sensor output detection circuit 1
If the position of the objective lens 18 detected by the step 4 changes greatly, the tilt detection circuit 16 recognizes that the disk holding sections 33 and 34 are holding foreign matter, and generates a drive signal without generating a drive signal. No compensation.

As described above, the optical disk reproducing apparatus 10
Can perform tilt detection and compensation with high accuracy.

As described above, by detecting the position of the objective lens 18, the optical disk reproducing apparatus 10 can perform tilt detection and compensation without providing a dedicated sensor for tilt detection. For this reason, the optical disk reproducing apparatus 10 controls the numerical aperture (Nume
It is possible to detect and compensate for the amount of tilt even for an optical disk that is thin and has a small diameter with an increase in rical aperture (NA).

The present invention is not limited to the above-described embodiment. For example, the present invention can be applied not only to an optical disk reproducing apparatus for reproducing digital data from an optical disk but also to a recording apparatus for recording digital data on an optical disk. Of course, it is possible.

As described above, it goes without saying that the present invention can be appropriately changed without departing from the spirit of the present invention.

[0046]

As described in detail above, the recording medium driving apparatus according to the present invention drives the disk-shaped recording medium to rotate, and records and / or reproduces digital data on the disk-shaped recording medium. A recording medium drive, comprising: a lens that irradiates a laser beam onto a disc-shaped recording medium; position detection means that detects a position of the lens when the lens is focused on the disc-shaped recording medium; Tilt detecting means for detecting a tilt instruction value based on the position of the lens detected by the detecting means.

Therefore, the recording medium driving device according to the present invention can detect the position of the lens for irradiating the disk-shaped recording medium with the laser beam, and detect the tilt instruction value based on the position of the lens. Thus, tilt detection can be performed without providing a dedicated sensor for tilt detection.

Also, the tilt detecting method according to the present invention
The position of the lens when the lens for irradiating the disk-shaped recording medium with the laser light is focused is detected, and the tilt instruction value is detected based on the detected position of the lens.

Therefore, the tilt detecting method according to the present invention can detect the tilt instruction value based on the position of the lens for irradiating the disk-shaped recording medium with the laser beam, and can use the dedicated tilt detecting value. Tilt detection can be performed without requiring a sensor.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical disk reproducing device shown as an embodiment of the present invention.

FIG. 2 is a diagram for explaining position detection of an objective lens with respect to a reference disk and an optical disk in the optical disk reproducing device.

FIG. 3 is a diagram illustrating a tilt angle, and is a diagram illustrating a method of calculating a tilt instruction value in the optical disc reproducing device.

[Description of Signs] 10 optical disk playback device, 11 optical pickup, 14 sensor output detection circuit, 15 equalizer, 16 tilt detection circuit, 18 objective lens,
Reference Signs List 20 position detector, 21 laser diode, 23
Photodiode

Claims (14)

[Claims] 1. A recording medium drive for rotating a disk-shaped recording medium and recording and / or reproducing digital data on the disk-shaped recording medium, wherein a laser is applied to the disk-shaped recording medium. A lens for irradiating light, position detecting means for detecting the position of the lens when the lens is focused on the disc-shaped recording medium, and a position of the lens detected by the position detecting means. And a tilt detection means for detecting a tilt instruction value. 2. The method according to claim 1, wherein the tilt detecting means includes a reference position which is a position of the lens detected by the position detecting means when the lens is focused on a reference disk-shaped recording medium having no tilt amount. 2. The recording medium according to claim 1, wherein when the lens is focused on the disc-shaped recording medium, an amount of displacement from the position of the lens detected by the position detecting means is detected. Drive. 3. The recording medium driving device according to claim 2, wherein the tilt detecting means calculates a tilt angle of the disk-shaped recording medium indicating the tilt instruction value based on the displacement amount. 4. The recording medium driving device according to claim 1, wherein the tilt detection means generates a drive signal for compensating for tilt based on a tilt error signal indicating the tilt instruction value. 5. An optical pickup means having the lens, irradiating the disk-shaped recording medium with a laser beam, and receiving return light reflected and diffracted on the surface of the disk-shaped recording medium, The tilt detecting means, based on the drive signal,
5. The optical pickup according to claim 4, wherein the optical pickup is controlled and driven so as to compensate for the tilt instruction value.
The recording medium driving device according to claim 1. 6. A waveform equalizer for performing a waveform equalization process on an RF signal based on return light reflected and diffracted on the surface of the disk-shaped recording medium, wherein the waveform equalizer includes the tilt detector 5. The recording medium driving device according to claim 4, wherein gain adjustment is performed based on the tilt error signal obtained by the following. 7. The recording medium drive according to claim 4, wherein the tilt detecting means does not generate the drive signal when a change in the position of the lens detected by the position detecting means is large. apparatus. 8. A method for detecting a position of a lens that irradiates a laser beam onto a disc-shaped recording medium when the lens is focused, and detecting a tilt instruction value based on the detected position of the lens. Characteristic tilt detection method. 9. A reference position which is a position of the lens detected when the lens is focused on a reference disk-shaped recording medium having no tilt amount, and a focus of the lens relative to the disk-shaped recording medium. 9. The tilt detecting method according to claim 8, wherein an amount of displacement from the position of the lens detected when the distance is adjusted is detected. 10. The tilt detecting method according to claim 9, wherein a tilt angle of the disc-shaped recording medium indicating the tilt instruction value is calculated based on the displacement amount. 11. The tilt detecting method according to claim 8, wherein a drive signal for compensating tilt is generated based on a tilt error signal indicating the tilt instruction value. 12. An optical pickup means having said lens for irradiating said disc-shaped recording medium with laser light and receiving return light reflected and diffracted on the surface of said disc-shaped recording medium, said drive means comprising: 12. The tilt detecting method according to claim 11, wherein the driving is controlled so as to compensate for the tilt instruction value based on the following. 13. A gain adjustment in a waveform equalization process performed on an RF signal based on return light reflected and diffracted on the surface of the disk-shaped recording medium based on the tilt error signal. Item 13. The tilt detection method according to Item 11. 14. The tilt detecting method according to claim 11, wherein the drive signal is not generated when the detected change in the position of the lens is large.