JP2001034972A - Optical disk apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk apparatus containing an optical head in which the neutral position of the optical head by which the prescribed position of a recording medium is irradiated with a light beam can be maintained properly. SOLUTION: This apparatus is provided with an optical head which is composed of objective lenses 7a, 7b by which light beams are condensed in prescribed positions on a recording medium and by which the light beams reflected from the recording medium are collected. The optical head is composed of a lens holder 6 by which the objective lenses 7a, 7b are held so as to be movable to a prescribed direction. The optical head is composed of a two-pole magnetized plane magnet which is installed so as to face a face coming into contact with the lens holding face 6a of the lens holder 6 and which provides a magnetic field toward the lens holder 6. The optical head is composed of a core 16 which is offset and arranged with reference to the center of the movement in the direction of an axis passing the objective lenses 7a, 7b of the magnetic field generated by the plane magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for recording information on a recording medium by using a light beam and reading the already recorded information from the recording medium. The present invention relates to a method for controlling the position of an objective lens of an optical head that irradiates a position.

[0002]

2. Description of the Related Art An optical disk apparatus used for optical information recording and reproduction using a light beam includes an objective lens, a lens holder for movably holding the objective lens, and a lens holder while moving the lens holder to a predetermined position. An optical head moved in the radial direction of the recording medium, a head driving mechanism for moving the optical head to a predetermined position, a recording signal processing unit for processing information to be recorded on the recording medium, and information obtained by the optical head And an interface for exchanging signals between external devices.

An optical head guides a laser light source that generates a light beam, a light beam generated by the laser light source to an objective lens, and guides a light beam reflected by a recording medium and collected by the objective lens to a photodetector. It comprises an optical element and a lens moving mechanism provided around the lens holder to move the lens holder, that is, the objective lens in a predetermined direction. It is also known that a laser light source and a photodetector are provided independently of an optical head.

A lens moving mechanism is provided around a lens holder (objective lens), and is formed into a plate-shaped and planar substantially rectangular magnet by dipole magnetization for applying a magnetic field in a predetermined direction, and a rectangular parallelepiped or a polyhedron. Lens holder
A focus coil and a track coil that are provided on a plurality of surfaces in contact with the surface on which the objective lens is fixed and generate a magnetic force of a polarity that is attracted or repelled to lines of magnetic force from a magnet, for example, an elongated substantially rectangular parallelepiped iron piece; And a magnetic body (core) arranged at a predetermined position of the lens holder so that the longitudinal direction is parallel to a direction orthogonal to the focus direction, and for positioning the lens holder at a neutral position.

[0005]

A core (magnetic material) for maintaining the lens holder in the neutral position in the above-described optical head.
Is a slender rectangular parallelepiped parallel to the direction orthogonal to the focus direction, so that 2 is provided around the lens holder.
The attraction and repulsion generated by acting on the magnetic force lines provided by the pole magnetized magnets are small, and as a result, the neutral position in the focus direction cannot be maintained.

This requires a large force to move the objective lens in the focusing direction, and increases the current flowing through the focusing coil. In this case, there is a problem that power consumption increases.

[0007] In addition, a shift in the position of the objective lens tends to cause a focus error, so that information recorded on a recording medium cannot be accurately reproduced.

An object of the present invention is to provide an optical disk device including an optical head capable of appropriately maintaining a neutral position of an optical head for irradiating a predetermined position of a recording medium with a light beam.

[0009]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems, and an object for converging a light beam at a predetermined position on a recording medium and collecting the light beam reflected from the recording medium. A lens, a lens holder that movably holds the objective lens in a predetermined direction, and a magnetic field that is provided to face a predetermined position around the lens holder, and is directed toward a predetermined position of the lens holder. And two rows are arranged at positions facing the magnets of the lens holder so as to face both ends of the magnets in a direction orthogonal to a direction of an axis passing through the objective lens. A magnetic material capable of generating a thrust for moving the lens holder in the direction of an axis passing through the objective lens by the action of the provided magnetic force. Than it is.

According to another aspect of the present invention, an objective lens for condensing a light beam at a predetermined position on a recording medium and collecting the light beam reflected from the recording medium, and holding the objective lens movably in a predetermined direction. A lens holder, a two-pole magnetized planar magnet provided to face a predetermined position around the lens holder, and providing a magnetic field toward a predetermined position of the lens holder; A surface that is in contact with the surface on which the objective lens is provided, and is arranged on a surface that can face the planar magnet so that a change in magnetic flux of the magnetic flux from the planar magnet is maximized, and a magnetic force provided by the planar magnet is provided. And a magnetic body capable of generating a thrust for moving the lens holder in the direction of an axis passing through the objective lens by the action of (1).

Further, the present invention condenses a light beam at a predetermined position on a recording medium and collects the light beam reflected from the recording medium, and holds the objective lens movably in a predetermined direction. A lens holder, a two-pole magnetized planar magnet that is provided to face a predetermined position around the lens holder, and provides a magnetic field toward a predetermined position of the lens holder; An optical disk device including an optical head, comprising: two rows of magnetic bodies arranged offset from a center of movement of a generated magnetic field in the direction of an axis passing through the objective lens. is there.

[0012]

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

FIG. 1 is a schematic diagram illustrating an optical disk device to which an embodiment of the present invention is applied.

As shown in FIG. 1, an optical disk device 1
Has an optical head device (pickup) 5 that is moved along first and second guide rails 3 and 4 extending from the chassis 2 and parallel to each other.

The pickup 5 can move to a predetermined position in a direction parallel to the direction in which the first and second guide rails 3 and 4 extend and in a direction perpendicular to the plane defined by the two guide rails 3 and 4. Is provided.

At a predetermined position of the lens holder 6, for example, a laser beam (light beam) emitted from a semiconductor laser element (not shown) provided at a predetermined position in the pickup 5 is focused on a predetermined position of a recording medium. Objective lens 7 for collecting the laser beam reflected by the recording medium
a, 7b are provided. In addition, each objective lens 7a,
7b have different aperture ratios, and can converge the laser beam to different beam diameters. Thus, information can be reproduced from two types of recording media having different recording densities.

The pickup 5 is also supplied with a control signal to a laser drive circuit (not shown) for driving a semiconductor laser element (not shown), and the laser beams collected by the objective lenses 7a and 7b are photoelectrically converted by a photodetector (not shown). A flexible cable 8 for transmitting an electric signal obtained from the pickup 5 to an external device and supplying a control signal to a control mechanism (not shown) for controlling the position of the objective lens (lens holder) is connected.

The flexible cable 8 includes a signal processing unit 9 for reproducing information recorded on a recording medium, one of which is collected by the selected objective lenses 7a and 7b and converted into an electric signal, and an optical element (not shown). A track error signal for controlling the positions of the objective lenses 7a and 7b detected by the photodetector and a track control signal corresponding to the focus error signal and a focus and track control circuit 10 for generating a focus control signal are connected. The signal processing unit 9 is connected to, for example, a host computer via an interface (not shown).

FIGS. 2 and 3 are schematic diagrams illustrating the lens holder 6 of the pickup 5 of the optical disk apparatus 1 shown in FIG. 1 and the vicinity thereof.

As shown in FIGS. 2A and 2B, the lens holder 6 includes a housing 1 serving also as a yoke.
It is provided at a predetermined position in the pickup 5 so as to be able to reciprocate along one shaft 11a and to be rotatable around the shaft 11a. The direction in which the axis 11a extends is orthogonal to the recording surface of the recording medium (not shown), and is the axis passing through the objective lens defined between the objective lenses (7a, 7b) and the recording surface of the recording medium. The direction is parallel to This direction is usually called a focus direction.

At predetermined positions on the outer periphery of the lens holder 6, track control coils 12a and 12b and focus control coils 13a and 13b are arranged so that axes connecting their center lines are orthogonal to each other. In addition, the intersection of both axes usually coincides with the axis 11 a of the housing 11.

At positions opposed to the track control coils 12a, 12b and the focus control coils 13a, 13b, respectively, are substantially rectangular planar magnets 14a, 14a, which are magnetized in two poles in the horizontal direction as shown in FIG. 14 (b), and substantially rectangular planar magnets 15a, 15b which are vertically polarized in two poles as shown in FIG. 2 (d).

As shown in FIG. 3A, the planar magnets 14a and 14b described with reference to FIGS.
In each of two planes that are opposed to the lens holder 6 and that are in contact with the objective lens holding surface 6a on the outer periphery of the lens holder 6, elongated rectangular areas arranged in at least two rows in a direction orthogonal to the focus direction are provided. Is provided. Therefore, the core 16
Are positioned substantially parallel to two ends of the planar magnets 14a and 14b in a direction orthogonal to the respective focus directions and close to the two ends. The core 16
FIG.
As shown in (b), the central portions of the two rows of rectangles may be integrally formed by joining the same members or independent magnetic members.

FIGS. 4 (a) and 4 (b) show plane magnets (facing a core) provided on a side surface of a lens holder (a plane in contact with an objective lens holding surface). FIG. 4 is a schematic diagram illustrating a force (focus direction) acting from a two-pole magnetized magnet).

As described above with reference to FIG.
The lens holder 6 is held movably along the axis 11a, and when no current is supplied to each of the coils 12a, 12b, 13a, and 13b, the lens holder 6 receives light from the planar magnets 14a and 14b acting on the core 16. Due to the force, the lens holder 6 enters a neutral state at a predetermined position of the shaft 11a. At this time, the lens holder 6 is also in a neutral state with respect to rotation about the axis 11a. Note that the neutral state of the lens holder 6 is such that each core 16 is placed in a plane magnet (represented by M here) facing each other.
It is needless to say that the thrust provided by being drawn toward the center of the planar magnet M by the attraction action from the lens holder 6 is obtained, and the thrust (attraction force) is defined by being balanced with the weight of the lens holder 6. .

As shown in FIGS. 4A and 4B, the force acting on the core 16 from the planar magnet M facing the core 16 is such that the end of the planar magnet M and the core 16 are close to each other. In this state, the force f1 is larger than the force f2 generated when the core 16 is close to the vicinity of the center of the planar magnet M in the height direction (focus direction).

Therefore, the distance d1 between the midpoint in the height direction of the planar magnet M and the core 16 in a state of being close to each other.
By arranging the core 16 in the lens holder 6 such that the distance d2 between the midpoint in the height direction of the planar magnet M and the core 16 is larger than the above, the lens holder 6 can be easily positioned at the neutral position. Can be done.

This is shown in FIGS. 3A and 3B.
The example of cores arranged in at least two rows in a direction perpendicular to the focus direction as shown in FIG. That is, when the core 16 is disposed with respect to the lens holder 6, the plane magnet M is positioned at a position away from the midpoint in the height direction of the plane magnet M with respect to the plane magnet M facing the core 16. By disposing at a position close to the end, the restoring force to the neutral position can be set to the maximum.

FIG. 5 is a schematic diagram for explaining the relationship between the size (h) and core width (w) of the core in the focus direction and the restoring force of the lens holder 6 to the neutral position.

As shown in FIG. 5, the length of the plane magnet (dipole magnetized magnet) M in the direction perpendicular to the focus direction is 1; the length of the core 16 of the lens holder 6 in the same direction is w; Assuming that the length in the direction orthogonal to the length w of the core 16, that is, the length of the core 16 in the focus direction is h, h is defined as “h1 <h
Looking at the magnitude of the restoring force as “2”, it is recognized that the restoring force increases as “h2”, that is, as the length in the focusing direction increases. Further, even if the length l of the planar magnet M changes, the fluctuation of the restoring force is small.

From this, the core 16 of the lens holder 6
It is preferable to increase the size in the height direction (focus direction) within the range that is structurally possible (including the weight).

FIGS. 6 (a) and 6 (b) show plane magnets (which are arranged opposite to the core) with respect to the core provided on the side surface (the plane in contact with the objective lens holding surface) of the lens holder. FIG. 3 is a schematic diagram illustrating a force (a track direction orthogonal to a focus direction) acting from a two-pole magnetized magnet).

As is clear from FIGS. 6A and 6B, the force acting on the core 16 from the planar magnet M facing the core 16 has a length in a direction perpendicular to the focus direction of the core 16. Is short (d1), and the force f1 acting when the distance d between the core 16 and the midpoint in the longitudinal direction of the planar magnet M is d.
The length of the core 16 in the same direction is longer (d2),
The force f2 generated when the distance d between the core 16 and the midpoint in the longitudinal direction of the planar magnet M is small.

Therefore, the magnitude of the restoring force can be adjusted by changing the width of the core 16 in the direction orthogonal to the focus direction. This adjustment can provide the required neutral position force.

FIG. 7 is a schematic diagram illustrating the relationship between the size (h) and core width (w) of the core in the track direction and the restoring force of the lens holder to the neutral position.

As shown in FIG. 7, the length of the plane magnet (dipole magnetized magnet) M in the direction orthogonal to the focus direction is 1, the length of the core 16 of the lens holder 6 in the same direction is w, Assuming that the length in the direction orthogonal to the length w of the core 16, that is, the length of the core 16 in the focus direction is h, h is defined as “h1 <h
Looking at the magnitude of the restoring force as “2”, it is recognized that the restoring force increases as “h2”, that is, as the length in the focusing direction increases.

However, when the difference between the length l of the planar magnet M and the length h in the focusing direction decreases, it is recognized that the restoring force decreases. From the figure, the appropriate size of the length h of the plane magnet M in the focus direction is approximately 1 in the length l of the plane magnet M in the direction orthogonal to the focus direction.
/ 2.

Accordingly, the core 16 of the lens holder 6
The size “h” in the height direction (focus direction) of FIG.
Considering an appropriate size defined by the restoring force in the focus direction described with reference to the above, it is preferable that the length l of the plane magnet M in the direction orthogonal to the focus direction is approximately １ ／.

As described above, in the configuration described with reference to FIGS. 3 to 7, the cores 16 provided on some of the surfaces of the lens holder 6 which are in contact with the objective lens holding surface 6a are provided with the planar magnets 14a. , 14b are provided in a space where the change of the magnetic flux provided from the first and the second magnets becomes large. That is, the core 16 is offset from the center of the magnetic flux provided by the planar magnets 14a and 14b in the focus direction and is positioned on the side surface of the lens holder 6.

Thus, the holding force for holding the lens holder 6 at the neutral position in the focus direction is increased,
The lens holder 6 can be positioned at the neutral position without applying a bias current or increasing the drive current supplied to the focus control coil.

[0041]

As described above, according to the present invention,
In the optical head of the optical disk device, there is no need to supply a bias current for positioning the lens holder at the neutral position or a large current to the focus control coil.

Further, the lens holder can be easily held at the neutral position.

Accordingly, an optical head which consumes less power and hardly causes a focus error can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing the periphery of a lens holder of the optical head of the optical disk device shown in FIG.

FIG. 3 is a schematic diagram illustrating a configuration of a core of the lens holder illustrated in FIG. 2;

FIG. 4 is a schematic diagram illustrating a focus direction force acting on the lens holder shown in FIGS. 2 and 3;

FIG. 5 is a schematic diagram illustrating the relationship between the size of the core in the focus direction shown in FIG. 4 and the restoring force of the lens holder to a neutral position.

FIG. 6 is a schematic diagram illustrating a track-direction force acting on the lens holder shown in FIGS. 2 and 3;

FIG. 7 is a schematic diagram for explaining the relationship between the size of the core in the track direction shown in FIG. 6 and the restoring force of the lens holder to a neutral position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk apparatus, 2 ... Chassis, 3 ... 1st guide rail, 4 ... 2nd guide rail, 5 ... Pickup, 6 ... Lens holder, 7 ... Objective lens 8 Flexible cable 9 Signal processing unit 10 Focus and track control circuit 11 Housing 11a Shaft 12a Track control coil 12b ··· Track control coil, 13a: Focus control coil, 13b: Focus control coil, 14a: Plane magnet, 14b: Plane magnet, 15a: Plane magnet, 15b: Plane magnet, 16 ... core (magnetic material).

Claims (9)

[Claims] An objective lens for condensing a light beam at a predetermined position on a recording medium and collecting the light beam reflected from the recording medium, and a lens holder for holding the objective lens movably in a predetermined direction. A magnet provided to face a predetermined position around the lens holder and providing a magnetic field toward a predetermined position on the lens holder; and a magnet facing the magnet on the lens holder, The magnets are arranged in two rows so as to face both ends in a direction perpendicular to the direction of the axis passing through the objective lens, and the lens holder is moved by the action of the magnetic force provided by the magnet. An optical disk device including an optical head, comprising: a magnetic body capable of generating a thrust for moving in a direction. 2. The magnetic body according to claim 1, wherein said magnetic body has a length substantially half as long as a length of said magnet in a direction orthogonal to a direction of an axis passing through said objective lens. An optical disk device as described in the above. 3. The optical disk according to claim 1, wherein the magnetic body has a length that is 1/5 of a length of the magnet along an axis passing through the objective lens. apparatus. 4. The optical disk device according to claim 1, wherein the magnetic bodies are connected to each other at an arbitrary position along an axis passing through the objective lens. 5. An objective lens for converging a light beam at a predetermined position on a recording medium and collecting a light beam reflected from the recording medium, and a lens holder for holding the objective lens movably in a predetermined direction. A two-pole magnetized planar magnet provided to face a predetermined position around the lens holder and providing a magnetic field toward the predetermined position of the lens holder; and the objective of the lens holder. A surface that is in contact with the surface on which the lens is provided, and is arranged on a surface that can face the planar magnet so that a change in magnetic flux of the magnetic flux from the planar magnet is maximized. An optical disc device including an optical head, comprising: a magnetic body capable of generating a thrust for moving the lens holder in a direction of an axis passing through the objective lens. 6. The optical disk apparatus according to claim 5, wherein said magnetic bodies are arranged in two rows in a direction orthogonal to a direction of an axis passing through said objective lens. 7. The optical disk device according to claim 6, wherein said magnetic bodies are connected to each other at a central portion of a length in a direction orthogonal to a direction of an axis passing through said objective lens. 8. The optical disk device according to claim 5, wherein said planar magnet is capable of providing a symmetric magnetic flux to said magnetic body. 9. An objective lens for condensing a light beam at a predetermined position on a recording medium and collecting a light beam reflected from the recording medium, and a lens holder for holding the objective lens movably in a predetermined direction. A two-pole magnetized planar magnet that is provided to face a predetermined position around the lens holder and provides a magnetic field toward the predetermined position of the lens holder; and a magnetic field generated by the plane magnet. An optical disk device including an optical head, comprising: two rows of magnetic bodies arranged offset from the center of movement in the direction of an axis passing through the objective lens.