JP2957377B2 - Optical head actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head actuator, and more particularly to an optical head actuator for moving an objective lens in the direction of an optical disk to adjust a focus and also moving the objective lens in a track direction to adjust a tracking. Related to actuators.

[0002]

2. Description of the Related Art Next-generation disk devices are required to have large capacity and high-speed transfer. For this reason, it is necessary to use a high-resolution objective lens for the optical head and to control the objective lens at high speed and with high accuracy. Therefore, an actuator for driving the objective lens is required to be small and light and have high torque.

FIGS. 3A and 3B are views showing an example of a conventional optical head actuator, wherein FIG. 3A is an exploded perspective view, and FIG. 3B is a plan view showing the arrangement of driving coils and magnets.

The objective lens 32 is mounted on an oval lens holder 31. A bearing 33 and an actuator base 41 provided at the center of the lens holder 31
The lens holder 31 is supported so as to be rotatable about the support shaft 42 and slidable in the axial direction by loosely fitting the support shaft 42 provided on the lens holder 31. In order to hold the lens holder 31 at the neutral position, a heart-shaped damper spring 45 is attached to the actuator base 41 side.
5 and the pin 39 on the lens holder 31 side are engaged.

A focus drive coil 34 is wound around the outer peripheral wall of the lens holder 31.
Flat tracking drive coils 35, 36, 37, 38 are attached to the surface of the focus drive coil 34. On the other hand, magnets 43, 44 are arranged on both sides of the support shaft 42 of the actuator base 41 so as to face each other, and the magnets 43, 44 and the focus driving coil 34 and the tracking driving coils 35, 36, 37, 38 interact with each other. The lens holder 31 is driven by the action. Here, by passing a current through the focus drive coil 34, the lens holder 31 slides along the support shaft 42 to perform focus control. In addition, the tracking drive coils 35 and 3
By passing a current through 6, 37, 38, the lens holder 31 rotates around the support shaft 42 to perform tracking control.

As shown in FIG. 3B, the tracking drive coils 35 and 36 are disposed opposite to both ends of the magnet 43.
The reference numerals 7 and 38 are arranged to face both end portions of the magnet 44. The magnetic fields H1, H2 and H3, H4 generated by the magnets 43 and 44 respectively act on one side of each of the tracking drive coils 35, 36 and 37, 38.

Now, when a current is applied from one side to the other side of the tracking drive coil on which the magnetic fields H1, H2 and H3, H4 are acting, respectively, from above to below, the direction of the white arrow in the direction of the white arrow is determined by Fleming's left-hand rule. Force is generated. When a current in the opposite direction is applied, a force is generated in the direction indicated by a black arrow. Therefore, by controlling the current of the tracking drive coil, the lens holder 31 is controlled.
Rotates about the support shaft 42. On the other hand, when a current flows through the focus drive coil 34, a vertical force is generated on the paper surface.
Slide along 2.

[0008] Such an actuator for an optical head is disclosed in Japanese Patent Application Laid-Open No. 1-178134.

[0009]

In the conventional optical head actuator described above, when a current is applied to the tracking drive coils, a driving force is generated only on one side of each tracking drive coil. Therefore, there is a problem that the electromagnetic force conversion efficiency of the tracking drive coil is poor.

Further, a damper spring is used to hold the lens holder at the neutral position. However, since a biased force acts between the bearing of the lens holder and the support shaft of the actuator base, the influence of friction is exerted. As a result, the displacement characteristics with respect to the drive current become non-linear. In particular, in the case of an objective lens having a large depth of focus, there is a problem that it is difficult to secure the accuracy of focus control.

An object of the present invention is to provide an actuator of an optical head capable of improving the electromagnetic force conversion efficiency of a tracking drive coil and improving the linearity of displacement with respect to a drive current.

[0012]

The actuator of the optical head according to the present invention is an elliptical lens holder having an objective lens at one end of a long axis, wherein the objective lens has a linear shape.
The lens holder has an outer peripheral wall in which a circle is cut by a chord so as to avoid the objective lens so that a 45 ° mirror can be disposed below, and the lens holder in which a focus driving coil is wound around the surface of the outer peripheral wall is used as an actuator base. An actuator of an optical head, which is loosely fitted to a provided support shaft, rotates about the support shaft, and slides in the axial direction of the support shaft, wherein the focus drive coil on a side remote from the objective lens Two magnetic bodies arranged symmetrically adjacent to the long axis on the surface of the flat body, and two flat magnetic bodies respectively arranged on the magnetic body.
Two tracking drive coils; an arc-shaped first magnet disposed on the actuator base such that the two tracking drive coils face one side of the two tracking drive coils on the adjacent side; 2 are arranged such that one end side faces the other one side portion of each of the two tracking drive coils and the other end side faces the arc-shaped portion of the focus drive coil. It has two arc-shaped second magnets, and is arranged and arranged such that the direction of the magnetic field generated by the first magnet is opposite to the direction of the magnetic field generated by the second magnet.

[0013] The actuator of the optical head according to the present invention is an oval lens holder having an objective lens at one end of a long axis, and is located at 45 ° directly below the objective lens.
The lens holder has an outer peripheral wall in which a circle is cut by a chord avoiding the objective lens so that a mirror can be arranged , and a lens holder having a focus driving coil wound around the surface of the outer peripheral wall is provided on a support provided on an actuator base. An actuator for the optical head, which is loosely fitted to a shaft and rotates about the support shaft and slides in the axial direction of the support shaft, and is provided on a surface of the focus drive coil on a side remote from the objective lens. Two magnetic bodies arranged symmetrically adjacent to the long axis, two flat tracking drive coils respectively arranged on the magnetic body, and two tracking drive coils on the side where the two tracking drive coils are adjacent to each other. An arc-shaped first magnet arranged on the actuator base so as to face one side of the two tracking drive coils, and adjacent to both sides of the first magnet, Two arc-shaped second magnets arranged so that one end side faces the other one-side portion of each of the two tracking drive coils, and two arc-shaped second magnets adjacent to the second magnet, It has two arc-shaped third magnets arranged to face the arc-shaped portion, and the direction of the magnetic field generated by the first magnet and the direction of the magnetic field generated by the second magnet are opposite to each other. It is arranged and configured so that

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are views showing a first embodiment of the present invention, wherein FIG. 1A is an exploded perspective view, and FIG. 1B is a plan view showing the arrangement of drive coils and magnets.

An objective lens 12 is mounted on one end side of the long axis of the oval lens holder 11. The bearing 13 provided at the center of the lens holder 11 and the support shaft 2 provided at the center of the actuator base 21.
The lens holder 11 is supported so as to be rotatable about the support shaft 22 and slidable in the axial direction by loosely fitting the lens holder 2 with the lens holder 11.

A focus drive coil 14 is wound around the outer peripheral wall of the lens holder 11. The outer peripheral wall is formed in a shape obtained by cutting a circle with a chord so as to avoid the objective lens 12. By forming in this manner, a 45 ° mirror (not shown) that reflects laser light can be arranged below the objective lens 12, so that the thickness of the actuator can be reduced.

A lens holder 11 is provided on the surface of the focus drive coil 14 remote from the objective lens 12.
The magnetic bodies 15 and 16 are arranged adjacent to each other symmetrically with respect to the major axis. The magnetic members 15 and 16 are for magnetically holding the lens holder 11 at a neutral position.
Further, flat tracking drive coils 17, 18 are mounted on the magnetic bodies 15, 16, respectively. In this case, the magnetic bodies 15 and 16 are located at the centers of the tracking drive coils 17 and 18, respectively.

On the other hand, arc-shaped magnets 23, 24 and 25 are arranged adjacent to each other on the inner wall surface of the actuator base 21 facing the focus drive coil 14. Here, as shown in FIG. 1B, the magnet 24 is disposed so as to oppose the portion where the tracking drive coils 17 and 18 are adjacent to each other, and oppose the arc-shaped portion of the focus drive coil 14. Magnets 23 and 25 are arranged. One end of each of the magnets 23 and 25 faces one side of each of the tracking drive coils 17 and 18, respectively.

Incidentally, the magnets 23, 24 and 25 generate magnetic fields in the directions indicated by arrows H1, H2, H3, H4, H5 and H6, respectively. Here, the directions of the magnetic fields H3, H4 generated by the magnet 24 and the directions of the magnetic fields H1, H2, H5, H6 generated by the magnets 23, 25 are opposite to each other.

Now, when the current of one side of each of the tracking drive coils 17 and 18 to which the magnetic fields H3 and H4 are applied is applied so as to flow downward from above the paper, the magnetic fields H2 and H5 Since current flows from the lower side of the drawing to the upper side of the other side of each coil on which the coil operates, the left and right sides of each of the tracking driving coils 17 and 18 on the left and right sides according to Fleming's rule. At the same time, a counterclockwise driving force is respectively generated. Therefore, the electromagnetic force conversion efficiency of the tracking drive coil is doubled as compared with the case where the driving force is generated only on one side of each coil as in the conventional example. When a current is applied in the opposite direction, a driving force in the opposite direction is generated, and the lens holder 11 rotates around the support shaft 22 in the opposite direction. Further, when a current flows through the focus drive coil 14, a vertical driving force is generated with respect to the plane of the drawing according to the direction of the current, so that the lens holder 11 slides along the support shaft 22.

When no current is applied to the focus driving coil 14 and the tracking driving coils 17, 18, the magnetic members 15 and 1 disposed adjacent to each other are not provided.
6 on a magnetic flux loop formed by magnetic fields H2 and H3 ;
Located on a magnetic flux loop formed by magnetic fields H4 and H5
Accordingly , each of the magnetic fields receives the action of the magnetic field most efficiently to function as a magnetic spring, and magnetically holds the lens holder 11 at the neutral position. Therefore, the bearing 1 of the lens holder
Since a well-balanced force acts between the shaft 3 and the support shaft 12 of the actuator base to increase the stability of the shaft, a straight line of the displacement with respect to the drive current as compared with the case where a damper spring is used as in the conventional example. Performance can be improved.

FIG. 2 shows a second embodiment of the present invention, and shows the arrangement of drive coils and magnets.

The difference from the first embodiment shown in FIG.
The magnet that acts on the focus drive coil and the magnet that acts on the tracking drive coil are arranged separately. That is, as shown in FIG.
8 acts on the focus drive coil 14 and the three magnets 2
7a, 27b, 27c act on the two tracking drive coils 17, 18.

Here, the magnet 27b is arranged at a portion adjacent to the tracking drive coils 17, 18, and the magnet 27b
a and 27c are arranged corresponding to one side portions of the coils of the tracking drive coils 17 and 18, respectively. Further, the magnets 26 and 28 are the focus driving coils 1
4 are arranged facing the arc portion. Then, the magnets 27a, 27b, 27c are arrows Ha, Hb, Ri Contact with each generating direction of the magnetic field indicated by Hc, the direction and the magnet 27a of the magnetic field magnet 27b is generated, the direction of the magnetic field 27c is generated The opposite is true.

Even in such a configuration, similarly to the first embodiment, since the driving force is simultaneously generated in both left and right sides of each of the tracking drive coils 17, 18, the electromagnetic force of the tracking drive coil is generated. The conversion efficiency can be improved twice as compared with the conventional example. In addition, the magnetic members 15, 16
Is held at a fixed position by the action of the magnetic fields Ha, Hb, Hc, so that the linearity of the displacement with respect to the drive current can be improved.

[0027]

As described above, according to the present invention, the oval lens holder having the objective lens at one end of the long axis is loosely fitted to the support shaft provided on the actuator base. In an actuator of an optical head that rotates around an axis and slides in an axial direction, two magnetic bodies are arranged adjacent to each other on a surface of a focus drive coil provided on an outer peripheral wall of a lens holder. Two flat tracking drive coils are arranged adjacent to each other such that the magnetic material is located at the center portion on the magnetic material, and both left and right sides of each of the two tracking drive coils are disposed on the inner wall surface of the actuator base. By arranging magnets so as to apply magnetic fields in opposite directions to the respective parts, when current is applied to the tracking drive coil, both left and right sides of each coil In the driving force is generated at the same time,
The electromagnetic force conversion efficiency of the tracking drive coil can be doubled as compared with the conventional example. In addition, since the magnetic body can be magnetically held at a fixed position, a well-balanced force acts between the bearing of the lens holder and the support shaft of the actuator base, thereby increasing the stability of the shaft. As compared with the case where the damper spring is used as described above, there is an effect that the linearity of the displacement with respect to the drive current can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, in which (a)
FIG. 2 is an exploded perspective view, and FIG. 2B is a plan view showing an arrangement state of drive coils and magnets.

FIG. 2 is a diagram showing a second embodiment of the present invention.

3A and 3B are diagrams illustrating an example of a conventional actuator of an optical head, in which FIG. 3A is an exploded perspective view, and FIG. 3B is a plan view illustrating an arrangement state of a drive coil and a magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Lens holder 12 Objective lens 14 Focus drive coil 15, 16 Magnetic body 17, 18 Tracking drive coil 21 Actuator base 22 Support shaft 23, 24, 25 Magnet 26, 28 Magnet for focus drive 27a, 27b, 27c For tracking drive magnet

Continuation of front page (56) References JP-A-62-65245 (JP, A) JP-A-63-247923 (JP, A) JP-A-60-44225 (JP, U) JP-A-61-136327 (JP) , U) Japanese Utility Model Showa 58-179635 (JP, U) Japanese Utility Model Showa 58-163908 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/09

Claims (2)

(57) [Claims] 1. An oval lens holder having an objective lens on one end side of a long axis, the lens holder being directly below the objective lens.
The lens holder is provided on an actuator base and has an outer peripheral wall having a shape obtained by cutting a circle with a chord so as to avoid the objective lens so that a mirror can be arranged at 45 °. A focus driving coil is wound around the surface of the outer peripheral wall. An optical head actuator that loosely fits with the provided support shaft and rotates about the support shaft and slides in the axial direction of the support shaft, wherein the focus drive coil on the side remote from the objective lens. Two magnetic bodies arranged symmetrically adjacent to the major axis on the surface, two flat tracking drive coils respectively arranged on the magnetic body, and the two tracking drive coils are adjacent to each other Arc-shaped first magnets arranged on the actuator base so as to face one side of the two tracking drive coils on the side of the first and second tracking drive coils, respectively, on both sides of the first magnets Adjacent, two arc-shaped second ends arranged so that one end side faces the other one-side portion of each coil of the two tracking drive coils and the other end side faces the arc-shaped portion of the focus drive coil. Wherein the direction of the magnetic field generated by the first magnet is opposite to the direction of the magnetic field generated by the second magnet. 2. An oval lens holder having an objective lens on one end side of a long axis, wherein the lens holder is located immediately below the objective lens.
The lens holder is provided on an actuator base and has an outer peripheral wall having a shape obtained by cutting a circle with a chord so as to avoid the objective lens so that a mirror can be arranged at 45 °. A focus driving coil is wound around the surface of the outer peripheral wall. An optical head actuator that loosely fits with the provided support shaft and rotates about the support shaft and slides in the axial direction of the support shaft, wherein the focus drive coil on the side remote from the objective lens. Two magnetic bodies arranged symmetrically adjacent to the major axis on the surface, two flat tracking drive coils respectively arranged on the magnetic body, and the two tracking drive coils are adjacent to each other Arc-shaped first magnets arranged on the actuator base so as to face one side of the two tracking drive coils on the side of the first and second tracking drive coils, respectively, on both sides of the first magnets Two arc-shaped second magnets which are adjacent to each other and one end of which is arranged to face the other one side of each coil of the two tracking drive coils; and wherein the focus is adjacent to the second magnet and A second magnet having two arc-shaped third magnets disposed so as to face the arc-shaped portion of the drive coil, wherein a direction of a magnetic field generated by the first magnet and a direction of a magnetic field generated by the second magnet The actuator of the optical head, characterized in that: