JP2000099970A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device capable of maintaining the floating height of a floating type optical head constantly regardless of the track position of an optical disk. SOLUTION: Arms 12 are attached to an arm driving part 30 and a load adding device 20 is attached at the top end of one arm of the arms 12. Moreover, a floating type optical head 10 is attached to the drive member 22 of the load adding device 20 with a leaf spring 13. The head 10 is moved in the radial direction of an optical disk 100 by allowing the arm 12 to rock in the horizontal plane. A rotation angle detecting circuit 41 detects the rotation angle of the arm 12 and a voltage converting circuit 42 converts the detected rotation angle into a voltage. A drive circuit 43 controls a load to be added to the head 10 so that the floating height of the head 10 is to be maintained constantly by driving the device 20 based on a voltage to be applied from the circuit 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording or reproducing information on an optical disk as an optical recording medium.

[0002]

2. Description of the Related Art Various optical disks such as DVD (digital video disk), CD-R (writable compact disk), and MO disk (magneto-optical disk) have been developed as optical recording media. An optical disk device is used to record or reproduce information on or from such an optical disk.

In an optical disk apparatus, an optical disk in which a plurality of tracks are formed concentrically or spirally is rotated, and an optical head provided with an objective lens is moved in a radial direction of the optical disk to record the data on each track of the optical disk. To play back the information.

A floating optical head is one of the optical heads. The floating type optical head on the optical disk floats at a certain distance from the surface of the optical disk by an air flow accompanying the rotation of the optical disk. Thereby, when the optical disc is rotated, the distance between the objective lens of the floating optical head and the optical disc is kept constant.

In an optical disk device provided with a linear movement type track seek mechanism (hereinafter, referred to as a linear movement type optical disk device), an arm provided with a floating optical head at the tip moves linearly in the radial direction of the optical disk.

On the other hand, in an optical disk device provided with a swing arm type track seek mechanism (hereinafter, referred to as a swing arm type optical disk device), an arm provided with a floating type optical head at its tip swings in a horizontal plane. The floating optical head moves in an arc shape in the radial direction of the optical disk.

[0007]

In the above-mentioned linear movement type optical disk apparatus, the optical disk is driven at a constant angular velocity (CA).
When rotated at V), the linear velocity at the outer peripheral portion of the optical disk is higher than the linear velocity at the inner peripheral portion. Thereby,
At the outer periphery of the optical disk, the flying height of the flying optical head increases, and a focus error occurs.

In the swing arm type optical disk apparatus, when the optical disk is rotated at a constant angular velocity (CAV), the linear velocity is similarly different at the track position, and the floating amount of the floating optical head is different. As a result, a focus error occurs.

In particular, in the swing arm type optical disk apparatus, even when the optical disk is rotated at a constant linear velocity (CLV), the skew angle of the floating type optical head in the direction of the track changes depending on the track position. The flying height of the head differs depending on the track position, and a focus error occurs.

It is an object of the present invention to provide an optical disk apparatus capable of keeping a floating amount of a floating type optical head constant regardless of a track position of the optical disk.

[0011]

An optical disk device according to a first aspect of the present invention is an optical disk device for recording or reproducing information on or from an optical disk having a plurality of tracks formed thereon. A rotary drive unit for driving, a floating optical head provided on an optical disc that is rotationally driven by the rotary drive unit, and an objective lens for irradiating the optical disc with light, and a floating optical head that is driven to rotate by the rotary drive unit. And a load applying means for applying a load to the floating optical head so that the floating amount of the floating optical head on the optical disk becomes constant.

In the optical disk device according to the present invention,
While the optical disk is rotated by the rotation driving unit, the floating optical head is moved in the radial direction of the optical disk by the head moving unit, and a desired track is irradiated with light by the objective lens of the floating optical head. At this time, a load is applied to the floating optical head by the load applying means so that the floating amount of the floating optical head on the optical disk becomes constant.

Accordingly, the distance between the optical disk and the floating optical head is kept constant regardless of the track position of the optical disk. As a result, occurrence of a focus error is prevented.

An optical disk device according to a second aspect of the present invention comprises:
In the configuration of the optical disc apparatus according to the invention, the load applying means includes a detecting means for detecting a track of the optical disc on which the flying optical head is located, and a load applied to the flying optical head according to the track detected by the detecting means. And load control means for controlling.

In this case, the track of the optical disk on which the floating optical head is located is detected, and the relationship between the previously determined track position and the flying height of the floating optical head, the load applied to the floating optical head, and the floating optical head The load applied to the flying optical head is controlled on the basis of the relationship with the flying height. Thus, the flying height of the flying optical head on the optical disk can be kept constant regardless of the track position of the optical disk.

An optical disk device according to a third aspect of the present invention has a
In the configuration of the optical disk device according to the invention, the light is guided to the objective lens of the floating optical head and the return light from the optical disk transmitted through the objective lens of the floating optical head is received to generate a data signal and a focus error signal. An optical system is further provided, and the load control means further controls a load applied to the floating optical head based on a focus error signal generated by the optical system.

In this case, the light is guided to the objective lens of the floating optical head by the optical system, and the optical disk is irradiated with the light by the objective lens. The return light from the optical disk passes through the objective lens of the floating optical head and is received by the optical system. Thereby, a data signal and a focus error signal are generated. Then, the load applied to the flying optical head is further controlled based on the generated focus error signal.

As described above, the load applied to the flying optical head is controlled according to the track on which the flying optical head is located, and the load applied to the flying optical head is further controlled based on the focus error signal. Thus, the focusing of light on the optical disk is performed accurately.

An optical disc device according to a fourth aspect of the present invention has a second
Alternatively, in the configuration of the optical disc apparatus according to the third aspect of the invention, the head moving means comprises: a supporting means for supporting the floating optical head; Swing means for swinging in a parallel plane, and the detecting means detects a track on which the floating optical head is located based on the rotation angle of the supporting means by the swing means.

In this case, the support means swings in a plane parallel to the surface of the optical disk by rotating about a predetermined rotation axis. This causes the floating optical head supported by the support means to move in the radial direction of the optical disk. Then, the track on which the flying optical head is located is detected based on the rotation angle of the support means.

An optical disc device according to a fifth aspect of the present invention has a second
Alternatively, in the configuration of the optical disk device according to the third invention, the head moving means includes: a supporting means for supporting the floating optical head; and a linear moving means for linearly moving the supporting means in a radial direction of the optical disk. The means detects the track on which the flying optical head is located based on the amount of movement of the support means by the linear moving means.

In this case, the support means moves linearly in the radial direction of the optical disk. This causes the floating optical head supported by the support means to move in the radial direction of the optical disk. Then, the track on which the flying optical head is located is detected based on the amount of movement of the support means.

An optical disk device according to a sixth aspect of the present invention has a first
In the configuration of the optical disk device according to any one of the fifth to fifth aspects, the floating optical head further includes a solid immersion lens that collects light transmitted through the objective lens and irradiates the optical disk with near-field light. It is.

In this case, in the floating optical head, the beam spot diameter is reduced by the solid immersion lens, so that the areal recording density of the optical disk is increased.

An optical disc device according to a seventh aspect of the present invention has a sixth aspect.
In the configuration of the optical disc device according to the invention, the solid immersion lens has a partially spherical entrance surface and a lower surface including a planar exit surface with a predetermined diameter at the center, and the lower surface around the exit surface is the solid immersion lens. It is formed on a surface different from the emission surface.

In this case, since the lower surface around the exit surface of the solid immersion lens is formed on a surface different from the exit surface, the optical axis of the solid immersion lens can be easily aligned.

[0027]

FIG. 1 is a schematic diagram showing a schematic configuration of an optical disk apparatus according to a first embodiment of the present invention, FIG. 2 is a schematic plan view of the optical disk apparatus shown in FIG. 1, and FIG. 3 is an optical disk apparatus shown in FIG. FIG. 3 is a schematic diagram showing a detailed configuration of a part of FIG. The optical disk device of the present embodiment is a swing arm type optical disk device.

In FIG. 1, the optical disc 100 is a DV
Optical recording media such as D, CD-R, and MO disks.
A floating optical head 10 is arranged on an optical disk 100. The arm 12 is attached to the arm drive unit 30, and the load applying device 20 is attached to a lower end of the arm 12. The floating optical head 10 is attached to a driving member 22 of the load applying device 20 via a leaf spring (suspension) 13. A mirror 14 is attached to the upper end of the arm 12. Further, the arm 12 is provided with an optical system 15.

As shown in FIGS. 2 and 3, the arm drive unit 30 includes a support rod 31 and a voice coil motor 32. As shown in FIG.
Includes a permanent magnet 33 and a coil 34. Arm 12
Is fixed to the support rod 31, and the coil 3 is attached to the end of the arm 12.
4 is attached. By changing the direction of the current flowing through the coil 34, the support rod 31 rotates, and the arm 12 swings in a horizontal plane as shown by an arrow Q in FIG. As a result, the floating optical head 10 is
It moves in an arc shape in the radial direction of 00.

As shown in FIG. 3, the load applying device 20
The voice coil motor includes a permanent magnet 21, a driving member 22, and a coil 23. By changing the direction of the current flowing through the coil 23, the driving member 22 moves in the vertical direction as indicated by the arrow Z. The load applied to the flying optical head 10 is controlled by adjusting the magnitude of the current flowing through the coil 23.

FIG. 4 shows the optical system 15 of the optical disk apparatus shown in FIG.
It is a schematic diagram which shows the schematic structure of. As shown in FIG. 4, the optical disc 100 is
Is driven to rotate. The signal recording film of the optical disc 100 has a plurality of tracks formed concentrically or spirally. The floating optical head 10 includes an objective lens 11.

The linearly polarized laser light emitted from the semiconductor laser element 62 is diffracted by the diffraction grating 63 into the 0th, + 1st and −1st orders, and is converted into a parallel light by the collimator lens 64. The parallel light is transmitted to the beam splitter 65,
The light passes through the mirror 66, is reflected by the mirror 14, and is focused on the signal recording film of the optical disc 100 by the objective lens 11 of the floating optical head 10.

Return light (reflected light) from the optical disk 100
Transmits through the objective lens 11 of the floating optical head 10,
The light is reflected by the mirror 14. The return light reflected by the mirror 14 is split into two by the beam splitter 66.

The return light reflected by the beam splitter 66 is condensed by the condensing lenses 69 and 70 on the light receiving surface of the photodetector 71 as three light spots. Photodetector 7
A tracking error signal and a focus error signal are generated from three light spots on one light receiving surface.

The tracking control is performed by moving the objective lens 11 of the flying optical head 10 in the radial direction of the optical disc 100 based on the tracking error signal. Further, focus control is performed by moving the objective lens 11 of the flying optical head 10 in a direction perpendicular to the surface of the optical disc 100 based on the focus error signal.

The return light transmitted through the beam splitter 66 is reflected by the beam splitter 65, and the half-wave plate 72 converts the polarization angle of the linearly polarized light to 45 °.
The return light is split by the polarization beam splitter 73 into two return lights having opposite polarization directions.

The return light reflected by the polarization beam splitter 73 is condensed on a light receiving surface of a photodetector 75a by a condenser lens 74a. Further, the polarization beam splitter 73
Is returned to the light receiving surface of the photodetector 75b by the condenser lens 74b. By taking the difference between the output signals of these two photodetectors 75a and 75b, the data signal from which the noise component has been removed is reproduced.

In FIG. 1, the rotation angle detection circuit 41
The rotation angle of the arm 12 is detected based on the output signal of the arm drive unit 30. The voltage conversion circuit 42 converts the rotation angle detected by the rotation angle detection circuit 41 into a voltage and supplies the voltage to the drive circuit 43. The focus error signal detection circuit 44 detects a focus error signal based on an output signal of the photodetector 71 of the optical system 15 in FIG. 4 and supplies the focus error signal to the drive circuit 43.

The drive circuit 43 generates a signal based on the voltage supplied from the voltage conversion circuit 42 and the focus error signal supplied from the focus error signal detection circuit 44.
The load applying device 20 is driven as described later.

The recording / reproducing signal processing circuit 45 reproduces and outputs a data signal based on the output signals of the photodetectors 75a and 75b of the optical system 15 shown in FIG. 4 and outputs the data signal based on an externally applied data signal. The optical system 15 is controlled.

In the optical disk device of this embodiment, the relationship between the rotation angle of the arm 12 by the arm driving unit 30 and the flying height of the flying optical head 10 and the relationship between the load applied to the flying optical head 10 and the flying height are determined in advance. Is controlled by controlling the load applied to the floating optical head 10 according to the rotation angle of the arm 12.
Is kept constant.

First, the rotation angle of the arm 12 is detected by the rotation angle detection circuit 41, and a voltage corresponding to the rotation angle is supplied to the drive circuit 43 by the voltage conversion circuit 42. The load applying device 20 is driven by the drive circuit 43 based on the voltage supplied from the voltage conversion circuit 42.
Thus, the load on the flying optical head 10 is controlled, and the flying height of the flying optical head 10 is kept constant.
That is, control is performed so that the load on the floating optical head 10 increases as the floating optical head 10 moves to the outer peripheral portion of the optical disc 100.

Further, the focus error signal detection circuit 4
The focus error signal is detected by 4 and the load applying device 20 is driven by the drive circuit 43 based on the focus error signal. Thereby, focusing of the laser beam on the optical disk 100 by the objective lens 11 of the flying optical head 10 is accurately performed.

FIG. 5 is a schematic diagram showing a schematic configuration of an optical disk device according to a second embodiment of the present invention, FIG. 6 is a schematic plan view of the optical disk device of FIG. 5, and FIG. It is a schematic diagram which shows a detailed structure. The optical disk device of the present embodiment is a linear movement type optical disk device.

The optical disk device of FIG. 5 differs from the optical disk device of FIG. 1 in that the arm 12 is linearly moved in the radial direction of the optical disk 100 by the arm driving unit 35 as indicated by an arrow X.

As shown in FIG. 6, the arm 12 is provided movably in the direction of arrow X along a pair of rails 36 via a support member 37.

As shown in FIG. 7, the load applying device 20
As with the load applying device 20 shown in FIG.
1, a voice coil motor including a driving member 22 and a coil 23. By changing the direction of the current flowing through the coil 23, the driving member 22 moves in the vertical direction as indicated by the arrow Z. The load applied to the flying optical head 10 is controlled by adjusting the magnitude of the current flowing through the coil 23.

The configuration of the optical system 15 in the optical disk device shown in FIGS. 5 to 7 is the same as the configuration of the optical system 15 shown in FIG.

In FIG. 5, the track position detecting circuit 46
Detects the track position of the optical disc 100 based on the amount of movement of the arm 12 by the arm driving unit 35. The voltage conversion circuit 42 converts the track position detected by the track position detection circuit 46 into a voltage,
Give to. The focus error signal detection circuit 44
A focus error signal is generated based on the output signal of the photodetector 71 of the optical system 15 of FIG. The drive circuit 43 drives the load applying device 20 based on the voltage supplied from the voltage conversion circuit 42 and the focus error signal supplied from the focus error signal detection circuit 44 as described later.

The recording / reproducing signal processing circuit 45 reproduces and outputs a data signal based on the output signals of the photodetectors 75a and 75b of the optical system 15 shown in FIG. 4 and outputs the data signal based on an externally applied data signal. The optical system 15 is controlled.

In the optical disk device of the present embodiment, the relationship between the amount of movement of the arm 12 by the arm drive unit 35 and the amount of floating of the flying optical head 10 and the relationship between the load applied to the floating optical head 10 and the flying amount are determined in advance. By controlling the load applied to the floating optical head 10 according to the amount of movement of the arm 12, the floating amount of the floating optical head 10 is kept constant.

First, the amount of movement of the arm 12 is detected by the track position detection circuit 46, and a voltage corresponding to the track position is supplied to the drive circuit 43 by the voltage conversion circuit 42. The load applying device 20 is driven by the drive circuit 43 based on the voltage supplied from the voltage conversion circuit 42. Thus, the load on the flying optical head 10 is controlled, and the flying height of the flying optical head 10 is kept constant. That is, the floating optical head 10 is
0 as it moves to the outer periphery of the optical head 1
Control is performed so that the load to zero increases.

Further, the focus error signal detection circuit 4
The focus error signal is detected by 4 and the load applying device 20 is driven by the drive circuit 43 based on the focus error signal. Thereby, focusing of the laser beam on the optical disk 100 by the objective lens 11 of the flying optical head 10 is accurately performed.

In the optical disk devices of the first and second embodiments, a floating optical head of a near-field (near field) recording / reproducing system and an optical disk may be used.
FIG. 8 is a schematic diagram showing a floating optical head and an optical disk of a near-field recording / reproducing method.

As shown in FIG. 8, in an optical disk 300 used in the near-field recording / reproducing method, a signal recording film 302 is formed on the surface side of a substrate 301.
Further, the floating optical head 50 includes the objective lens 51 and S
An IL (Solid Immersion Lens) 52 is provided. The laser light is narrowed down by the objective lens 51 and enters the SIL 52.

The SIL 52 is obtained by flattening and polishing a part of a sphere made of a transparent material having a large refractive index such as glass. The focal point of the laser light incident on the SIL 52 coincides with the polished surface, and the polished surface corresponds to the laser light emission surface.

Assuming that the refractive index of the SIL 52 is n and the wavelength of the laser beam in the air is λ, the wavelength of the laser beam at the SIL 52 is λ / n. Therefore, the spot diameter of the laser beam on the emission surface of the SIL 52 is 1 / n of the spot diameter collected by the objective lens 51.

When the laser beam emitted from the SIL 52 enters the air, it returns to the original spot diameter again. However, SIL5
In the range where the distance from the emission surface of No. 2 is up to １ ／ of the wavelength of the laser light (about 100 nm or less), that is, in the near-field region, the laser light seeps out with the same properties as in the SIL 52. The light leached in this way is called evanescent light. The spot diameter of the evanescent light is as small as 1 / n of the spot diameter collected by the objective lens 51. By using such evanescent light, it is possible to increase the areal recording density of the optical disc 300.

When the floating optical head 50 of the near-field recording / reproducing method is used in the optical disk devices of the first and second embodiments, the floating optical head 50 is placed close to the optical disk. Since the flying height of 50 can be kept constant, the effect of the near-field recording / reproducing method is sufficiently exhibited.

FIG. 9 is a diagram showing another example of the SIL used for the floating optical head of the optical disk device.

The SIL 81 of FIG. 9A has a substantially hemispherical upper surface and a flat lower surface, and has a columnar convex portion 82 at the center of the flat lower surface. The center of the lower surface of the convex portion 82 and SI
The distance R between the top of the spherical surface of L81 is set to be the same as the radius of the spherical surface. As a result, the laser light that is perpendicularly incident on the spherical surface is focused on the center of the lower surface of the projection 82. This SI
In L81, the lower surface of the convex portion 82 becomes the emission surface of the laser beam.

When the SIL 81 is used, the optical axis of the SIL 81 can be adjusted by aligning the convex portion 82 with the optical axis of the optical system, so that the assembling and adjustment of the floating optical head are facilitated.

The SIL 83 shown in FIG. 9B has a partially spherical upper surface and an inverted truncated conical lower surface. The distance R between the center of the central portion 84 on the lower surface of the SIL 83 and the top of the spherical surface
Is set to be the same as the radius of the spherical surface. As a result, the laser beam that is perpendicularly incident on the spherical surface is focused on the center of the central portion 84 on the lower surface. In this SIL 83, the central portion 84 on the lower surface serves as a laser light emission surface.

When this SIL 83 is used, the central portion 84 on the lower surface is aligned with the optical axis of the optical system, thereby
Can be aligned, so that the assembling and adjustment of the floating optical head are facilitated.

The SIL 85 shown in FIG. 9C has a substantially hemispherical upper surface and a flat lower surface, and has a cylindrical concave portion 86 at the center of the flat lower surface. The distance R between the center of the bottom surface of the recess 86 and the top of the spherical surface is set to be the same as the radius of the spherical surface. As a result, the laser beam that is perpendicularly incident on the spherical surface is focused on the center of the bottom surface of the concave portion 86. In this SIL85,
The bottom surface of the concave portion 86 serves as a laser light emission surface.

When the SIL 85 is used, the optical axis of the SIL 85 can be adjusted by aligning the concave portion 86 with the optical axis of the optical system, so that the assembling and adjustment of the floating optical head are facilitated.

[Brief description of the drawings]

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

FIG. 2 is a schematic plan view of the optical disk device of FIG.

FIG. 3 is a schematic diagram showing a detailed configuration of a part of the optical disk device of FIG. 1;

FIG. 4 is a schematic diagram showing a schematic configuration of an optical system of the optical disk device of FIG. 1;

FIG. 5 is a schematic diagram showing a schematic configuration of an optical disc device according to a second embodiment of the present invention.

FIG. 6 is a schematic plan view of the optical disk device of FIG.

FIG. 7 is a schematic diagram showing a detailed configuration of a part of the optical disk device of FIG. 5;

FIG. 8 is a schematic diagram showing a flying optical head of a near-field recording / reproducing method.

FIG. 9 is a diagram showing another example of the SIL used for the flying optical head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spindle motor 2 Rotation axis 10, 50 Floating optical head 11, 51 Objective lens 12 Arm 13 Leaf spring 14 Mirror 15 Optical system 20 Load applying device 21, 33 Permanent magnet 22 Drive member 23, 34 Coil 30, 32 Arm drive part 41 rotation angle detection circuit 42 voltage conversion circuit 43 drive circuit 44 focus error signal detection circuit 46 track position detection circuit 52 SIL

Continued on the front page F term (reference)

Claims (7)

[Claims] 1. An optical disk device for recording or reproducing information on an optical disk on which a plurality of tracks are formed, comprising: a rotation driving unit for driving the optical disk to rotate; and an optical disk driven to rotate by the rotation driving unit. A floating optical head provided with an objective lens for irradiating the optical disc with light; a head moving means for moving the floating optical head in a radial direction of the optical disc rotationally driven by the rotation driving means; An optical disc apparatus, comprising: a load applying means for applying a load to the floating optical head so that a floating amount of the floating optical head on the optical disc is constant. 2. The load applying unit includes: a detecting unit configured to detect a track of the optical disk on which the floating optical head is located; and a load applied to the floating optical head according to the track detected by the detecting unit. 2. The optical disk apparatus according to claim 1, further comprising a load control unit for controlling the optical disk apparatus. 3. A method for guiding light to the objective lens of the floating optical head and receiving feedback light from the optical disk that has passed through the objective lens of the floating optical head,
An optical system that generates a data signal and a focus error signal is further provided, wherein the load control unit further controls a load applied to the flying optical head based on the focus error signal generated by the optical system. 3. The optical disk device according to claim 2, wherein: 4. The head moving means comprises: a supporting means for supporting the floating optical head; and a supporting means for rotating the supporting means around a predetermined rotation axis to thereby make the supporting means parallel to the surface of the optical disk. And a swinging means for swinging the floating optical head. The detecting means detects a track on which the flying optical head is located based on a rotation angle of the supporting means by the swinging means. 4. The optical disk device according to 2 or 3. 5. The head moving unit includes: a supporting unit that supports the floating optical head; and a linear moving unit that linearly moves the supporting unit in a radial direction of the optical disc. 4. The optical disk apparatus according to claim 2, wherein a track on which the flying optical head is located is detected based on a moving amount of the supporting means by the linear moving means. 6. The floating optical head further comprises a solid immersion lens for condensing light transmitted through the objective lens and irradiating near-field light to the optical disc. 6. The optical disk device according to any one of 5. 7. The solid immersion lens has a partially spherical entrance surface and a lower surface including a planar exit surface having a predetermined diameter at a central portion, and a lower surface surrounding the exit surface is defined as an exit surface. 7. The structure according to claim 6, wherein the surfaces are formed on different surfaces.
An optical disk device as described in the above.