JP2004310822A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive capable of correctly adjusting eccentricity with a simple mechanism without giving damage to an optical disk. <P>SOLUTION: A rotation holding part 2 has a spindle motor for rotating a magneto-optic disk 8 and a turntable which supports the magneto-optic disk 8. A detection signal processing circuit 12 detects track eccentricity on the basis of a radial push-pull signal from the optic disk. A track eccentricity picture is adjusted on the basis of an output of the detection signal processing circuit 12. An aligning actuator 42 brings an aligning bar 41 into contact with the hub 84 of the magneto-optic disk 8 in rotation to change a relative configuration angle between the magneto-optic disk 8 and the turntable. Since the rotation center of the optic disk itself does not coincide with the rotation center of tracks of the optic disk, resulting from difference that usually occurs at the time of manufacturing the optic disk, which can adjust the track eccentricity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical disk device provided with a method for reducing track eccentricity of an optical disk.
[0002]
[Prior art]
Generally, in recording / reproducing of an optical disk, the center of a track of the optical disk formed in a spiral shape is deviated from the rotation center of the optical disk. The so-called track eccentricity occurs. If track eccentricity occurs, tracking will be hindered. Therefore, it is desirable that there be no track eccentricity. However, in general, track eccentricity always occurs due to mechanical errors generated during manufacturing and use.
[0003]
On the other hand, in recent years, a high-density optical disk that performs recording / reproduction using a blue laser instead of the conventional red laser has been put into practical use. The spot diameter of the laser beam on the optical disk surface is proportional to the value obtained by dividing the NA (Numerical Aperture) of the objective lens by the wavelength of the laser. In the DVD (Digital Versatile Disk) standard, a red laser having a wavelength of 650 nm and an objective lens having an NA of 0.6 have been used. On the other hand, in the Blu-Ray standard that is being put to practical use, a blue laser having a wavelength of 405 nm and an objective lens having an NA of 0.85 are used, so that the spot diameter is less than half that of the DVD standard. it can be. Therefore, while the track pitch is 0.6 μm in the DVD standard, the track pitch can be 0.32 μm in the Blu-Ray standard.
[0004]
However, when the track pitch becomes narrow as described above, the adverse effect of the track eccentricity on the tracking becomes larger than before. For example, if the track eccentricity is 50 μmp-p, it corresponds to eccentricity of about 83 tracks in the DVD standard, while it corresponds to eccentricity of about 156 tracks in the Blu-Ray standard. Therefore, in a high-density optical disc such as the Blu-Ray standard, it is more important to reduce track eccentricity during recording / reproduction.
[0005]
The invention for reducing track eccentricity is divided into an invention having a feature on the disk side and an invention having a feature on the recording / reproducing apparatus side. Since the present invention belongs to the latter, a conventional technique having characteristics on the recording / reproducing apparatus side will be examined.
[0006]
[Patent Document 1] JP-A-61-189063
[Patent Document 2] JP-A-10-79133
Japanese Patent Application Laid-Open No. H10-199127 discloses a tracking servo assisting device that adjusts eccentricity by pressing a peripheral portion of a rotating disk that is semi-fixed to a holding mechanism to displace the disk. It is.
[0009]
Patent Literature 2 discloses an eccentricity correction method for a disk device in which eccentricity is adjusted by hitting a disk holding unit with a hammer.
[0010]
Patent Document 3 discloses a mechanism that corrects the eccentricity by eccentricizing the eccentricity correction clamper using a plunger and that can vary the chucking force so that the eccentricity correction clamper does not move the correction position during high-speed rotation. An optical disk device provided with an added eccentricity correction mechanism is disclosed.
[0011]
[Problems to be solved by the present invention]
However, in the invention of Patent Document 1, the peripheral portion of the disk semi-fixed to the holding mechanism is pressed, so that the disk is damaged. In order to reduce the damage to the disk, it is only necessary to weaken the fixing during the eccentricity adjustment. However, since the rotation becomes unstable, the eccentricity cannot be accurately adjusted.
[0012]
In the invention of Patent Document 2 described above, a mechanism for hitting the disk holding portion with a hammer is required, so that the device is complicated.
[0013]
According to the invention of Patent Document 3, the eccentricity of the disk can be changed by hitting the eccentricity correcting clamper with the plunger. However, this invention relates to the invention of eccentricity correction, and the problem to be solved is different. Further, since the eccentricity correction clamper is hit, there is a problem that the eccentricity correction clamper and the disk held thereby are damaged.
[0014]
In view of the above problems, it is an object of the present invention to provide an optical disk device that can accurately adjust eccentricity with a simple mechanism without damaging the disk.
[0015]
According to the present invention is to solve the problems]
The invention of claim 1 relates to an optical disk device for reproducing an optical disk having a hub made of a metal magnetic material at a central portion. The optical disk device includes a holding unit, an eccentricity detecting unit, and an alignment unit.
[0016]
The holding means includes a spindle motor, a center shaft rotated by the spindle motor, a magnetic body fixed to the center shaft and magnetically attaching the hub, and a support fixed to the center shaft and supporting the optical disk. A turntable having a surface; and provisional alignment means for aligning the center of the optical disc with the center of the center shaft.
[0017]
The eccentricity detecting means detects track eccentricity during rotation of the optical disc. The alignment means changes an arrangement angle of the rotating optical disc with respect to the holding means so that track eccentricity detected by the eccentricity detection means is minimized.
[0018]
Even if the center of rotation of the optical disk and the center of the optical disk are matched, the rotation center of the optical disk itself and the center of rotation of the tracks of the optical disk generally do not match due to an error generated during the manufacturing of the optical disk. Therefore, the track eccentricity of the optical disk can be adjusted by changing the arrangement angle of the optical disk with respect to the holding means as in the first aspect of the present invention.
[0019]
Further, according to the first aspect of the present invention, since no impact force is applied to the disk or the clamper for fixing the disk, the disk is not damaged.
[0020]
The invention according to claim 2 is the optical disc device according to claim 1, wherein the alignment means further includes a contact member that is brought into contact with the hub to change an arrangement angle of the optical disc with respect to the holding means. . Thus, the center of the track of the optical disc and the center of the rotation driving unit can be made to coincide with each other, so that track eccentricity can be eliminated.
[0021]
The invention according to claim 3 is the optical disc apparatus according to claim 1, wherein the alignment means further includes a contact member that is brought into contact with an outermost periphery to change an arrangement angle of the optical disc with respect to the holding means. . The arrangement angle is shifted. Thereby, track eccentricity can be eliminated.
[0022]
The invention according to claim 4 is the optical disc apparatus according to claim 1, wherein the alignment means further reduces a magnetic force between the hub and the magnetic body for fixing the optical disc, thereby rotating the rotating optical disc. comprises demagnetization means of reducing the speed. Thereby, track eccentricity can be eliminated.
[0023]
【Example】
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a configuration diagram of a magneto-optical disc recording / reproducing apparatus 1 which is an embodiment of the optical disc apparatus of the present invention. The magneto-optical disk recording / reproducing apparatus 1 includes a rotation holding unit 2, an optical pickup 3, an alignment mechanism 4, a detection signal processing circuit 12, a PLL circuit 13, a control unit 14, a motor control circuit 15, an oscillator 16, and an eccentricity detection circuit 17. consisting of. The magneto-optical disk recording / reproducing apparatus 1 can be broadly divided into a mechanism for rotating and driving the magneto-optical disk 8 and a mechanism for adjusting track eccentricity during rotation of the magneto-optical disk 8.
[0024]
First, components for rotating and driving the magneto-optical disk 8 will be described. The rotation holder 2 includes a spindle motor 21 for rotating the magneto-optical disk 8 and a turntable 25 for supporting the magneto-optical disk 8 as shown in FIG. The rotation holding unit 2 will be described later in detail.
[0025]
The detection signal processing circuit 12 performs processing such as A / D conversion on the signal detected by the optical pickup 3. The PLL circuit 13 creates a synchronization signal for the motor control circuit 15 to use for motor control. The motor control circuit 15 drives the spindle motor 21 to rotate. The motor control circuit 15 controls the rotation speed of the spindle motor 21 by comparing the phase of the synchronization signal generated by the PLL circuit 13 based on the signal extracted from the disk with the reference clock pulse generated by the oscillator 16. .
[0026]
A signal from which the spindle motor 21 of the magneto-optical disk recording / reproducing apparatus 1 is rotationally driven includes a signal from a fine clock mark provided on the magneto-optical disk 8 and a signal from a recording magnetic domain on the magneto-optical disk 8. there is a playback signal, and the like. The PLL circuit 15 creates a synchronization signal based on these signals.
[0027]
Next, components for adjusting track eccentricity during rotation of the magneto-optical disk 8 will be described. The eccentricity detecting circuit 17 detects the track eccentricity amount based on the output from the detection signal processing circuit 12 and the output from the spindle motor 21 (here, one pulse signal per rotation). Specifically, the number of output pulses from the detection signal processing circuit 12 detected from the rise of the output pulse from the spindle motor 21 to the rise of the next output pulse is counted. The magnitude of the eccentricity is determined by the magnitude of the pulse number. Note that, as a signal used as a basis for detecting track eccentricity in the magneto-optical disk recording / reproducing apparatus 1, there are a track cross signal, a radial push-pull signal, and the like.
[0028]
The alignment mechanism 4 includes an alignment rod 41 and an alignment actuator 42. The alignment rod 41 presses a hub 84 provided at the center of the magneto-optical disk 8 from above. Thereby, the relative position between the center of the magneto-optical disk 8 and the center of rotation can be adjusted. The alignment actuator 42 controls the alignment rod 41 based on an instruction from the eccentricity detection circuit 17. With the magneto-optical disk recording / reproducing apparatus 1, an embodiment of the present invention can be realized.
[0029]
The operation of the magneto-optical disk recording / reproducing apparatus 1 will be described with reference to the flowchart of FIG. When the magneto-optical disk 8 is mounted on the rotation holder 2 of the magneto-optical disk recording / reproducing device 1 (step S1), the magneto-optical disk 8 starts rotating (step S2). The details of the operation of the magneto-optical disk drive 1 when the magneto-optical disk 1 is mounted in step S1 will be described later.
[0030]
When the number of rotations reaches a predetermined value, a laser beam is emitted from the optical pickup 3 to the magneto-optical disk 8, and the focus is turned on (step S3). Next, based on the track cross signal or the radial push-pull signal quantized and sampled by the detection signal processing circuit 12, the number of tracks straddled by the laser light during one rotation of the magneto-optical disk 8 is determined as shown in FIG. It is counted by the lead detection circuit 17 (step S4). The magnitude of the track eccentricity is determined based on the number of tracks (step S5).
[0031]
If it is determined in step S5 that the track eccentricity is large, the process proceeds to step S6 for performing the alignment operation. Then, the process proceeds to step S4 for measuring the track eccentricity amount again. The details of the alignment operation in step S6 will be described later. If it is determined in step S5 that the track eccentricity is small, the process proceeds to step S7 for performing an operation of turning on tracking. Then, the recording / reproducing operation is started (step S8).
[0032]
FIG. 3 is a diagram showing the structure of the magneto-optical disk 8. On the magneto-optical disk 8 having the translucent substrate 83, lands 811 and 812, and lands 821 and 822 are formed spirally or concentrically from the outer periphery to the inner periphery. The magneto-optical disk 8 includes a dielectric layer (not shown) for preventing the magnetic film from being oxidized, a magnetic layer for recording / reproducing, a dielectric layer for a protective layer, and a heat radiation layer for heat radiation on the translucent substrate 83. Are sequentially laminated, and a UV curable resin for preventing scratches is further applied.
[0033]
With reference to FIGS. 4 to 8, a mechanism for rotating the magneto-optical disk 8 and an operation when the magneto-optical disk 8 is mounted on the rotation holding unit 2 in step S1 of the flowchart in FIG. 2 will be described. FIG. 4 is a diagram showing a cross section of the magneto-optical disk 8, and FIG. 5 is a diagram showing the rotation holding unit 2. FIG. 7 is a diagram showing a state immediately before fixing the magneto-optical disk 8 to the rotation holding unit 2, and FIG. 8 is a diagram showing a state after fixing the magneto-optical disk 8 to the rotation holding unit 2.
[0034]
Referring to FIG. 4, a projection 831 and a center hole 86 are provided in the center of the substrate 83 of the magneto-optical disk 8. A hub 84 made of a metal magnetic material is bonded onto the center hole 86.
[0035]
5 includes a spindle motor 21, a center shaft 22, an annular magnet 23, a tubular member 24, and a turntable 25. The turntable 25 is fixed to a center shaft 22 rotated by a spindle motor 21. An annular concave groove is formed on the upper surface of the turntable 25 concentrically with the center shaft 22, and an inner peripheral cylindrical portion 251 and an outer peripheral cylindrical portion 252 are formed. An annular magnet 23 is fixed to the upper surface of the inner cylindrical portion 251 concentrically with the center shaft 22, and the hub of the magneto-optical disk 8 having the hub 84 is magnetically attached.
[0036]
A compression coil spring 26 is loosely fitted between the inner cylindrical portion 251 and the outer cylindrical portion 252. Above the compression coil spring 26, a cylindrical member 24 for centering is slidably inserted in the vertical direction. A flange 241 having a conical outer peripheral surface is provided at the upper end of the cylindrical member 24, and the cylindrical member 24 is urged upward by abutting the compression coil spring 26 on the lower surface of the flange 241. ing. A flange 254 having a flat support surface 253 for supporting the magneto-optical disk 8 is provided above the outer cylindrical portion 252.
[0037]
The reason why the outer peripheral surface of the flange portion 241 of the cylindrical member 24 is conical is that the center of the magneto-optical disk 8 and the center of the rotation holding portion 2 are easily matched. For example, when the cylindrical member 29 as shown in FIG. 6 is used, the magneto-optical disk 8 is supported by the upper surface 292 of the flange 291, but the diameter of the center hole 86 of the magneto-optical disk 8 is If the outer diameter D of the portion other than the flange portion 291 is smaller than the outer diameter D, the magneto-optical disk 8 cannot be mounted on the tubular member 29. When the diameter of the center hole 86 of the magneto-optical disk 8 is significantly larger than the outer diameter D, it is difficult to make the center of the magneto-optical disk 8 coincide with the center of the rotation holding unit 2. However, if the cylindrical member 24 having the conical outer peripheral surface of the flange portion 241 as shown in FIG. 5 is used, even if the diameter of the center hole 86 of the magneto-optical disk 8 has an error from the design value, the magneto-optical The disk 8 can be mounted, and the center of the magneto-optical disk 8 and the center of the rotation holding section 2 can be made substantially coincident.
[0038]
As shown in FIG. 7, when the magneto-optical disk 8 is mounted on the flange 241 of the cylindrical member 24 of the rotation holding unit 2, the annular magnet 23 fixed to the center shaft 22 and the hub of the magneto-optical disk 8 A magnetic force acts between the cylindrical member 24 and the cylindrical member 24 slidable in the vertical direction.
[0039]
Then, as shown in FIG. 8, the lower surface 832 of the convex portion 831 of the substrate 83 is held by the magnetic force between the annular magnet 23 and the hub 84 while being supported by the support surface 253 of the turntable 25.
[0040]
Next, a first embodiment of the alignment operation in step S6 of the flowchart of FIG. 2 will be described with reference to FIG. When the hub 84 is pressed by the alignment rod 41 installed above the magneto-optical disk 8 while the magneto-optical disk 8 is rotating, friction occurs between the alignment rod 41 and the hub 84. As a result, a difference occurs between the rotational moments of the magneto-optical disk 8 and the turntable 25, and a difference occurs between the rotational speed of the rotation holding unit 2 and the rotational speed of the magneto-optical disk 8. Therefore, the relative arrangement angle of the magneto-optical disk 8 with respect to the turntable 25 changes.
[0041]
If the center of rotation of the disk 8 is coincident with the center of the track (land 81, groove 82) of the magneto-optical disk 8, only the relative angle between the magneto-optical disk 8 and the rotation holding unit 2 is changed. In can not be alignment. In this case, the alignment can be performed only by changing the relative position of the center between the magneto-optical disk 8 and the rotation holding unit 2.
[0042]
However, usually, the center of rotation of the magneto-optical disk 8 does not coincide with the center of the track (land 81, groove 82) of the magneto-optical disk 8 due to an error generated during manufacturing. Therefore, even if the magneto-optical disk 8 is fixed to the turntable 25 so that the center of the magneto-optical disk 8 and the center of the rotation holding portion coincide, track eccentricity occurs when the magneto-optical disk 8 rotates. Therefore, if the relative arrangement angle between the magneto-optical disk 8 and the rotation holding unit 2 is changed, the relative position between the track of the magneto-optical disk 8 and the center of the rotation holding unit 2 can be changed. By pressing the hub 84 of the magneto-optical disk 8 from above with an appropriate force using the alignment rod 41, the relative arrangement angle between the magneto-optical disk 8 and the rotation holding unit 2 is adjusted to minimize the track eccentricity. it can be of. This can be regarded as an embodiment of the second aspect of the present invention.
[0043]
With reference to FIG. 10, a second embodiment of the alignment operation in step S6 of the flowchart of FIG. 2 will be described. The magneto-optical disk 8 is fixed to the rotation holding unit 2 by a magnetic force acting between the annular magnet 23 of the rotation holding unit 2 and the hub 84 of the magneto-optical disk 8. The tip of the alignment rod 43 provided near the outermost peripheral portion of the magneto-optical disk 8 is brought into contact with the outer peripheral portion of the magneto-optical disk to cause friction between the alignment rod 43 and the magneto-optical disk 8. This causes a difference between the rotation speed of the magneto-optical disk 8 and the rotation speed of the rotation holding unit 2. When the center of rotation of the magneto-optical disk 8 does not normally coincide with the center of the track of the magneto-optical disk 8 due to an error generated during manufacturing, the magneto-optical disk 8 can be aligned by the above-described method. This can be regarded as an embodiment of the third aspect of the present invention.
[0044]
With reference to FIG. 11, a third embodiment of the alignment operation in step S6 of the flowchart of FIG. 2 will be described. An electromagnet 48 is provided above the hub 84, and a current is applied to the coil of the electromagnet 48 to generate a magnetic field in a direction to cancel the magnetic force between the annular magnet 23 and the hub 84. Since the magnetic adhesion of the magneto-optical disk 8 is weakened, slippage occurs between the substrate 83 of the magneto-optical disk 8 and the turntable 25, and the relative arrangement angle between them can be changed. Thereby, the alignment of the magneto-optical disk 8 can be performed.
[0045]
With reference to FIG. 12, a fourth embodiment of the alignment operation in step S6 of the flowchart of FIG. 2 will be described. A permanent magnet 49 is provided above the hub 84. The polarity of the permanent magnet 49 is set so as to repel the polarity of the annular magnet 23. For example, if the lower surface of the permanent magnet 49 is an S pole, the upper surface of the annular magnet 23 is also installed so as to be an S pole. At the time of alignment, the magnetic force between the annular magnet 23 and the hub 84 is weakened by bringing the permanent magnet 49 closer to the hub 84. Since the magnetic adhesion of the magneto-optical disk 8 is weakened, slippage occurs between the substrate 83 of the magneto-optical disk 8 and the turntable 25, and the relative arrangement angle between them can be changed. Thereby, the alignment of the magneto-optical disk 8 can be performed. At the time of non-alignment, the permanent magnet 49 is moved away from the hub 84.
[0046]
With reference to FIG. 13, a fifth embodiment of the alignment operation in step S6 of the flowchart in FIG. 2 will be described. An electromagnet 27 is provided below the annular magnet 23, and a current is applied to the coil of the electromagnet 27 to generate a magnetic field in a direction to cancel the magnetic force between the annular magnet 23 and the hub 84. Since the magnetic adhesion of the magneto-optical disk 8 is weakened, slippage occurs between the substrate 83 of the magneto-optical disk 8 and the turntable 25, and the relative arrangement angle between them can be changed. Thereby, the alignment of the magneto-optical disk 8 can be performed.
[0047]
In the above embodiment, the magneto-optical disk recording / reproducing apparatus 1 for measuring the track eccentricity of the magneto-optical disk has been described as an example. ), An R (Read Once) type disc can be applied to a recording / reproducing apparatus for measuring track eccentricity. That is, the present invention is applicable to all optical disk recording / reproducing apparatuses capable of measuring the track eccentricity based on a tracking error signal or the like.
[0048]
【The invention's effect】
According to the present invention, track eccentricity can be adjusted by changing the arrangement angle of the optical disk while the optical disk is kept rotating. Compared to a method of adjusting the track eccentricity after stopping the optical disk once, there is an effect that the initial movement waiting time is shortened for the user because there is no rotation waiting time. Further, the eccentricity can be accurately adjusted by a simple mechanism without damaging the optical disk.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a magneto-optical disk recording / reproducing apparatus 1.
FIG. 2 is a flowchart showing an operation of the magneto-optical disk recording / reproducing apparatus 1.
FIG. 3 is a diagram showing a structure of a magneto-optical disk 8;
FIG. 4 is a diagram showing a central portion of the magneto-optical disk 8;
FIG. 5 is a diagram showing a first example of a rotation holding unit 2.
FIG. 6 is a view showing a second example of the rotation holding unit 2.
FIG. 7 is a diagram showing a state immediately before the magneto-optical disk 8 is mounted on the turntable 25 of the rotation holding unit 2;
FIG. 8 is a diagram showing a state where the magneto-optical disk 8 is mounted on the turntable 25 of the rotation holding unit 2.
FIG. 9 is a first embodiment showing a means for correcting track eccentricity with the magneto-optical disk 8 mounted.
FIG. 10 is a second embodiment showing a means for correcting track eccentricity with the magneto-optical disk 8 mounted.
FIG. 11 is a third embodiment showing means for correcting track eccentricity in a state where the magneto-optical disk 8 is mounted.
FIG. 12 is a fourth embodiment showing a means for correcting track eccentricity with the magneto-optical disk 8 mounted.
FIG. 13 is a fifth embodiment showing a means for correcting track eccentricity with the magneto-optical disk 8 mounted.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 magneto-optical disk recording / reproducing device 2 rotation holding unit 3 optical pickup 4 alignment mechanism 8 magneto-optical disk 12 detection signal processing circuit 13 PLL circuit 14 control unit 15 motor control circuit 16 oscillator 17 eccentricity detection circuit 21 spindle motor 22 center shaft 23 annular magnet 24, 29 cylindrical member 25 turntable 26 compression coil spring 27 electromagnet 41, 43 alignment rod 42 alignment actuator 48 electromagnet 49 permanent magnet 81 land 82 groove 83 translucent substrate 84 hub 86 center hole

Claims (4)

An optical disc device for reproducing an optical disc having a hub made of a metal magnetic material at a center portion,
A turntable having a spindle motor, a center shaft rotated by the spindle motor, a magnetic body fixed to the center shaft and magnetizing the hub, and a support surface fixed to the center shaft and supporting the optical disc. Holding means including temporary alignment means for aligning the center of the optical disc with the center of the center shaft;
Eccentricity detecting means for detecting track eccentricity during rotation of the optical disc,
An optical disk device, comprising: an alignment unit that changes an arrangement angle of the rotating optical disk with respect to the holding unit so that track eccentricity detected by the eccentricity detection unit is minimized. 2. The optical disc apparatus according to claim 1, wherein the alignment means includes a contact member that is brought into contact with the hub to change an arrangement angle of the optical disc with respect to the holding means. 2. The optical disc apparatus according to claim 1, wherein the centering means includes a contact member which is brought into contact with an outermost periphery to change an arrangement angle of the optical disc with respect to the holding means. 2. The centering means according to claim 1, further comprising a demagnetizing means for reducing a magnetic force between the hub for fixing the optical disk and the magnetic body to reduce a rotation speed of the rotating optical disk. Optical disk device.

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