JP2978863B2 - Objective lens drive mechanism for optical information recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving mechanism of an objective lens for focusing a laser beam on a recording medium in an optical information recording apparatus.

[0002]

2. Description of the Related Art An objective lens driving mechanism of an optical information recording apparatus accurately condenses laser light emitted from a semiconductor laser light source on a recording medium and optically records and reproduces information. In that case, the drive mechanism is operated to move the objective lens supported on the support mechanism in a focus direction perpendicular to the recording medium and a track direction parallel to the radial direction of the recording medium. Generally, the supporting mechanism employs a supporting method using a spring member, and the driving mechanism utilizes an electromagnetic force generated by a coil and a magnet.

FIG. 3 shows a conventional objective lens driving mechanism 21.
FIG. The movable member 24 holding the objective lens 22 is coupled to a track holder 34 via a focus spring 29. The track holder 34 is connected to the column 33 via the track spring 30.

[0004] That is, the objective lens 22 moves in the focus direction perpendicular to the recording medium (not shown) via the movable member 24 by the elastic bending of the focus spring 29.
Further, the objective lens 22 can be moved in the track direction parallel to the radial direction of the recording medium by the elastic bending of the track spring 30.

[0005] The operation of the objective lens 22 in the focus direction and the track direction utilizes the electromagnetic force generated by the focus coil 31 and the track coil 32 provided on the movable member 24 and the magnets 23a and 23b. The magnets 23a and 23b form a parallel magnetic field perpendicular to the focus direction and the track direction. The focus coil 31 is wound in the track direction, and the track coil 32 is wound in the focus direction.

[0006] The magnets 23a and 23b have magnet support portions 26a and 26b on the back opposite to the front facing the focus coil 31 and the track coil 32, respectively.
6b and is positioned and supported.

With the above configuration, the focus coil 31
When the power is turned on, an electromagnetic force is generated in the focus direction along the optical axis of the objective lens 22. Track coil 32
When an electric current is supplied to the objective lens 22, an electromagnetic force is generated in a track direction perpendicular to the optical axis of the objective lens 22. With these electromagnetic forces, the movable member 24 carrying the objective lens 22 moves in two directions orthogonal to the focus direction and the track direction.

[0008]

However, the objective lens driving mechanism 21 shown as a conventional example has the following problems to be solved.

[0009] Magnets 23a and 23 for generating electromagnetic force
b is positioned with its back surfaces in contact with the magnet support portions 26a and 26b. If the thickness error of the magnet or the processing dimension of the magnet support portion varies in accuracy, the magnetic field strength in the focus coil 31 and the track coil 32 becomes unbalanced. The movable member 24 is displaced in a focus direction perpendicular to the recording medium and a track direction which is a radial direction by a combined force of two generated magnetic forces of the focus coil 31 and the track coil 32.

Therefore, if the resultant force of the magnetic forces generated by the coils 31 and 32 becomes unbalanced, the posture of the movable member 24 becomes unstable, and the objective lens 22 is displaced with respect to the drive current in the focus direction and the track direction. Disturbance occurs in the phase at a frequency characteristic of several kHz, which causes the servo characteristics of the objective lens driving mechanism to deteriorate in reliability.

In view of the above problems, it is an object of the present invention to improve the frequency characteristics of displacing an objective lens in a focus direction and a track direction by balancing the electromagnetic forces generated by a focus coil and a track coil, thereby improving servo characteristics. It is an object of the present invention to provide an objective lens driving mechanism that enhances the reliability of the lens and enables high-speed response.

[0012]

The objective lens driving mechanism of the optical information recording apparatus according to the present invention has an objective lens for condensing a laser beam on a recording medium supported by a movable member, and energizing a focus coil and a track coil. By generating an electromagnetic force in a focus direction along the optical axis of the objective lens and in a track direction perpendicular to the optical axis, the movable member can move in two directions orthogonal to the focus direction and the track direction. A pair of magnets at positions corresponding to the focus coil and the track coil and opposed around the optical axis of the objective lens, each being supported by a magnet support member; The pair of magnets facing each other with the center as the center is fixed to the magnet positioning member so that the facing distance is determined. Both constituted by bonding the magnet support member by an adhesive layer on the back opposite to the respective facing surfaces of the opposed pair of magnets.

In this case, the magnet positioning member positions and fixes only the opposing surfaces of the pair of opposing magnets so that the opposing distance is determined, and the back surface on which the adhesive layer is provided on the side opposite to the opposing surface is provided. I am free. Also, when the magnet positioning member is used as a positioning jig, the pair of magnets is fixed to the magnet support member via the adhesive layer on the back surface by determining the facing distance of the pair of magnets, and can be detached. Can be configured.

The adhesive layer has a thickness enough to absorb a dimensional accuracy error between the pair of opposed magnets, when the error is present.

According to this configuration, the generated electromagnetic forces of the focus coil and the track coil are balanced, the posture of the movable member is stabilized, and the frequency characteristic of the displacement of the objective lens with respect to the drive current in the focus direction and the track direction is changed. Improve.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an objective lens driving mechanism of an optical information recording apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an objective lens driving mechanism 1 according to the present embodiment, and FIG. 2 is a cross-sectional view showing a magnet mounting portion.

A movable member 4 carrying the objective lens 2 and movable in a predetermined direction is connected to a track holder 14 via a focus spring 9, and the track holder 14 is connected via a track spring 10. To the support 13. Thereby, the objective lens 2 is moved in the focus direction perpendicular to the recording medium (not shown) via the movable member 4 by the flexure of the focus spring 9, and the objective lens 2 is moved via the movable member 4 by the flexure of the track spring 10. Lens 2
Can be moved in the track direction parallel to the radial direction of the recording medium.

The operation of the movable member 4 in the focus direction and the track direction is performed by the electromagnetic force of the magnetic field generated by the focus coil 11, the track coil 12, and the magnets 3a and 3b provided on the movable member 4. Magnets 3a, 3
By b, parallel magnetic fields are formed in the directions perpendicular to the focus direction and the track direction, respectively. The focus coil 11 is wound in the track direction,
2 is wound in the focus direction.

Therefore, when the power supply to the focus coil 11 is turned on, an electromagnetic force is generated in the focus direction which is the optical axis direction of the objective lens 2. Also, the track coil 12
When the power is turned on, an electromagnetic force is generated in a track direction perpendicular to the optical axis direction of the objective lens 2. With these electromagnetic forces, the movable member 4 carrying the objective lens 2 can be driven in two axial directions, the focus direction and the track direction.

Further, the precision error absorbing mechanism which is the gist structure of the present invention is configured as follows. Magnet 3a,
3b is supported by supporting portions 6a and 6b, respectively. In the case of one of the magnets 3a, the magnet 3a is joined to a magnet supporting portion 6a that supports the magnet 3a via an adhesive layer 7a. The other magnet 3b is also joined to the magnet support 6b via an adhesive layer 7b.

Further, both magnets 3a and 3b are provided with a single magnet positioning member (jig) 5 from below.
And is positioned and fixed. That is, the track coils 12 of the two magnets 3a, 3b
In order to keep the facing distance L between the surfaces A and B on the side facing
Both magnets 3a, 3b are fixed by magnet positioning members 5 from below.

In the above configuration, the magnets 3a, 3
Even if there is some processing error in the thickness dimension of b, since the facing distance L of the surfaces A and B facing each other is fixed at a fixed position by the magnet positioning member 5, the processing error is reduced by the adhesive layer 7a on the back. , 7b.

The absorption of the accuracy error suppresses the variation of the magnetic field strength, that is, the electromagnetic force generated at the two places of the focus coil 11 and the track coil 12, and maintains the good balance of the electromagnetic force. Posture is stabilized.

When the magnet positioning member 5 is used as a positioning jig, a pair of magnets 3 facing each other are used.
After the facing distance L between the magnet support members a and 3b is determined, the magnet support member 6 is attached to the back surface of each magnet via the adhesive layers 7a and 7b.
a, 6b. Thereafter, the magnet positioning member 5 may be configured to be removable.

[0026]

As described above, the objective lens driving mechanism of the optical information recording apparatus according to the present invention can absorb the dimensional accuracy error of the magnet and the member supporting the magnet. Variations in the magnetic field strength in the track coil are suppressed, and a stable frequency characteristic is obtained, whereby the reliability of high-speed response can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an objective lens driving mechanism according to the present invention.

FIG. 2 is a cross-sectional view illustrating a magnet mounting portion according to the embodiment.

FIG. 3 is a plan view showing a conventional example of an objective lens driving mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens drive mechanism 2 Objective lens 3a, 3b Magnet 4 Movable member 5 Other magnet placement member 6a, 6b Magnet support part 7a, 7b Adhesive layer 9 Focus spring 10 Track spring 11 Focus coil 12 Track coil 13 Column 14 Track holder

Claims (6)

(57) [Claims] An objective lens for converging a laser beam on a recording medium is supported by a movable member, and when a focus coil and a track coil are energized, a focus direction along the optical axis of the objective lens and a direction perpendicular to the optical axis. By generating an electromagnetic force in the track direction, the movable member is movable in two directions orthogonal to the focus direction and the track direction, and at a position corresponding to the focus coil and the track coil, and the optical axis of the objective lens is changed. An objective lens driving mechanism for an optical information recording device, wherein a pair of magnets opposed to each other at a center are supported by a magnet support member, wherein the pair of opposed magnets centered on an optical axis of the objective lens. Attached and fixed to the magnet positioning member so that the facing distance is determined, and the pair of facing magnets An objective lens driving mechanism, wherein the objective lens driving mechanism is joined to the magnet support member by an adhesive layer on a back surface opposite to the opposing surface. 2. The magnet positioning member according to claim 1, wherein only the opposing surfaces of the pair of opposing magnets are positioned and fixed so that the opposing distance is determined. The back surface on which the adhesive layer is provided on the opposite side to the opposing surface is free. 2. The objective lens driving mechanism according to claim 1, wherein: 3. The magnet positioning member is used as a positioning jig, the distance between the pair of opposed magnets is determined, and after being fixed to the magnet support member via the adhesive layer on the back surface thereof, the magnet is removable. The objective lens driving mechanism according to claim 1, wherein the objective lens driving mechanism is configured as follows. 4. The adhesive layer according to claim 1, wherein when the pair of opposed magnets has a dimensional accuracy error, the adhesive layer has a thickness enough to absorb the error. 2. The objective lens driving mechanism according to 1. Wherein said movable member is supported on the track the holder via the focus springs, one of the claims 1-4 track holder, characterized in that has been supported to the strut through the track spring an objective lens drive mechanism crab according. 6. The moving member according to claim 5, wherein the movable member moves in a focusing direction by an elastic bending of the focus spring, and is movable in a track direction by an elastic bending of the track spring. The objective lens driving mechanism described in the above.