JP2620221B2 - Optical pickup actuator - Google Patents

Description

The present invention relates to an improvement in an actuator for an optical pickup.

[Conventional technology]

2. Description of the Related Art In recent years, information-related industries have been remarkably advanced, and the amount of information to be handled tends to increase dramatically. for that reason,
Instead of a pickup that records and reproduces information using a conventional magnetic head, an optical pickup that uses an optical pickup that uses light to record at high density and reproduce at high speed There is a situation where information recording / reproducing devices are receiving attention.

The optical pickup converges and irradiates a recording medium with a light beam through an objective lens, and when performing recording or reproduction, focus control means for condensing the light beam in a spot-like focus state, and follows a target track. Tracking control means is required. For this purpose, it is necessary to control the objective lens to move in a minute amount in a direction perpendicular to the surface of the recording medium by a focus control signal, and to control the minute amount to move in a direction crossing a recording track of the recording medium by a tracking control signal. An actuator is used as a movable mechanism.

As a conventional example of the above actuator, for example,
-121541. In the technology disclosed in this publication, a U-shaped tracking coil is used to cause a magnetic flux to cross only on one side of a coil conductor parallel to the lens optical axis, and the tracking drive force is reduced by the electromagnetic force generated in this coil conductor. Is occurring. However, the tracking drive as described above cannot efficiently generate a driving force.

[Means and actions for solving the problems]

In order to move the lens in a focusing direction, which is the direction of the lens optical axis, and in a tracking direction perpendicular to the lens, the actuator for an optical pickup according to the present invention has a lens holder fixed to the lens, which is parallel to the lens optical axis. A surface is formed, and a focusing coil and a tracking coil are mounted on the lens holder so as to overlap each other. ("Attach to overlap" means that one of the focusing coil and the tracking coil is placed on the surface of the lens holder. The other coil is disposed on the upper side, so that both coils are connected to the lens holder), and the focusing is performed by directing a magnetic flux generated from a permanent magnet to both the coils. Optical pickup that moves in the direction and tracking direction In actuator flop, with coupling the focusing coil to the surface so as to wind the first axis is the lens optical axis,
Winding a second axis orthogonal to the first axis ("winding the second axis" means that the coil conductor of the tracking coil surrounds the second axis). Not only in the case of winding in a direction substantially perpendicular to the second axial direction as shown in the figure, but also in the case of winding in a direction non-perpendicular to the second axial direction as shown in FIG. ) To the first surface so as to sandwich the focusing coil and to sandwich the focusing coil ("clamping" means to sandwich the focusing coil through a space in which the focusing coil can move in a small amount). A first permanent magnet and a second permanent magnet are arranged along a first direction perpendicular to an axial direction of the axis, and the tracking coil is further imagined to include the first axis and the second axis. When divided into a first coil portion and a second coil portion in a plane, A third permanent magnet configured to direct magnetic fluxes of opposite polarities to the first coil portion and the second coil portion is disposed, and the lens is displaced only in both the focusing direction and the tracking direction. Fixing one end of the obtained elastic member to the lens holder and fixing the other end of the elastic member to the base;
When the optical pickup actuator is viewed in the lens optical axis direction (meaning "when the pickup actuator is viewed in the lens optical axis direction from the side where the recording medium is arranged"), The third permanent magnet, the lens, and the elastic member are sequentially arranged along a second direction substantially perpendicular to both the direction of the first direction and the direction of the lens optical axis ("sequentially arranged"). Is
The third permanent magnet, the lens, and the elastic member are generally arranged in the order of the third permanent magnet, the lens, and the elastic member along the second direction). .

〔Example〕

Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.

1 to 3 relate to a first embodiment of the present invention. FIG. 1 is an exploded view of the first embodiment, FIG. 2 is a plan view of the first embodiment, and FIG. FIG. 3 is a sectional view taken along line AA ′ of FIG. 2;

In the actuator 1 for an optical pickup of the first embodiment, a substantially U-shaped outer yoke 3 is fixed to a base 2 integrally or separately. In the center of this base 2,
For example, a square through hole is provided, and a pair of inner yokes 4a and 4b each having an arcuate concave center in the center are attached to the through hole. The permanent magnets 5A, 5B, which are attached to the inner surface of the
Is fixed so as to face the end face in the longitudinal direction.
A trapezoidal permanent magnet 7 is attached to the inner surface of the outer yoke 3 opposite to the opening via a plate-shaped non-magnetic member 6 so as to face one yoke 4b. Magnetic members 8, 8 are attached to both sides.

On the other hand, near the opening of the outer yoke 3, the inner yoke 4
AA 'line connecting the centers of the a and 4b and the center of the permanent magnet 7 (second line
Fixing members 9A, 9B are erected on both sides of each of the fixing members 9A, 9B. Each of the fixing members 9A, 9B has a U-shaped leaf spring 11A, 11B which slightly expands to one side from the state of the parallel plate. Is fixed at the end. A relay member 13 is fixed to the other end of each of the leaf springs 11A and 11B, and one end of a leaf spring 15, 15 parallel to the surface of the base 2 is provided at an upper end and a lower end of the relay member 13. The lens holder 16 is fixed to the other end.

A lens barrel 17 is formed in the center of the lens holder 16, and an objective lens 18 is attached thereto.
A focus coil 19 is formed by winding a conductive wire around the outer periphery of the 16 square cylindrical bodies (bobbins). Above lens barrel 17
Is provided with a circular opening at the center of the upper surface of the lens holder 16 and fixed inside the lens opening. Also, this lens holder
A tracking coil 21 formed by winding a conductive wire (without interposing the outer periphery of the rectangular cylinder (bobbin) or this bobbin) on the opposite side surface to which the ends of the plate springs 15 and 15 in 16 are fixed is provided. Installed.

The lens holder 16 is disposed so as to be loosely fitted to the outside of the inner yokes 4a and 4b, and one end of each of the leaf springs 11A and 11B fixed to the fixing members 9A and 9B, and each of the leaf springs 11A and 11B. It is elastically supported by leaf springs 15 and 15 each having one end fixed to a relay member 13 attached to the other end. Then the inner yokes 4a, 4
A pair of permanent magnets 5A and 5B are disposed on both sides of the b. For example, the magnetic flux from the N pole of the permanent magnet 5A penetrates through the focus coil 19 on the side facing the N pole, and the inner yoke 4a , 4b, respectively, further penetrates the focus coil 19, flows to the other permanent magnet 5B side, and the magnetic flux passing through the permanent magnet 5B further passes through the outer yoke 3, the base 2 formed of magnetic members, and the outer yoke 3. A closed magnetic path returning to the permanent magnet 5A through the above is formed. Therefore, between the permanent magnet 5A and the inner yokes 4a and 4b facing each other and the inner yoke 4 facing the permanent magnet 5B.
The focus coil 19 (or the focus coil 19 to which the focus coil 19 is attached) Lens holder 16) has an objective lens
A force is applied to the focus coil 19 along the optical axis direction F, and focus control can be performed by supplying a current to the focus coil 19.

The magnetic flux emitted from the N pole of the permanent magnet 7 passes through one magnetic member 8, passes through a vertical winding portion of the tracking coil 21 facing the magnetic member 8, and passes through the inner yoke 4b in the longitudinal direction. Penetrates the other vertical winding portion of the tracking coil 21 facing the inner yoke 4b, flows into the other magnetic member 8, passes through the magnetic member 8, and passes through the permanent magnet 7
A closed magnetic path returning to the S pole of FIG. Therefore, by supplying a current to the tracking coil 21, the leaf spring 11
In FIG. 2, the vertical direction T in FIG.
The lens holder 16 can be moved at the same time so that tracking control can be performed.

The fixing members 9A, 9B of the leaf springs 11A, 11B are fixed by positioning members 22A, 22B attached to the base 2 adjacent to the fixing members 9A, 9B.
Positioning of the mounting height to A and 9B is performed.

The actuator 1 of the first embodiment is characterized in that a magnetic circuit forming a movable mechanism for focus control and a magnetic circuit forming a movable mechanism for tracking control are formed in a horizontal plane direction parallel to the base 2. It has become.

According to the first embodiment configured as described above, since the focus control and tracking control magnetic circuits are formed on the same plane, the thickness can be reduced.

Further, since the focus control and tracking control magnetic circuits are formed almost independently in the direction perpendicular to each other on the same plane, the adjustment of each magnetic circuit can be performed independently. The mutual interference in which the magnetic flux passing through the other coil changes due to the current flowing through 17 or 19 can be reduced.

 FIG. 4 shows a second embodiment of the present invention.

In the actuator 31 of the second embodiment, tracking coils 32, 33 are provided as shown in FIG. 5, and a permanent magnet 34 is provided at a portion facing each of the tracking coils 32, 33 as shown in FIG. , 35 are installed. Magnetic members 34A, 34B; 3 on both sides of these permanent magnets 34, 35, respectively.
5A and 35B are provided.

Also, the inner yokes 4a and 4b are mounted in a direction different from the arrangement direction of the first embodiment by 90 °.

Others are the same as the first embodiment. In this case, the magnetic flux from the N pole of one of the permanent magnets 5A forming the focus control magnetic circuit passes through the horizontal winding of the focus coil 19, and the inner yoke 4a, the base 2, the outer A closed magnetic path returning to the S pole of the permanent magnet 5A via the yoke 3 is formed. In addition, counter balances 38 and 39 are attached to the lower surface of the lens holder 16 so that the center of the lens holder 16 when an electromagnetic force is applied coincides with the center of gravity.

The operation and effect of the second embodiment are almost the same as those of the first embodiment.

FIG. 6 shows a reference example of the present invention. A concave portion is formed in each of the U-shaped outer yokes 62 outside the inner yokes 4a and 4b, and the two magnetic members 64 are vertically arranged through the non-magnetic members 63 and 63 as shown in FIG. , 65; permanent magnets 66, 66 sandwiched between 64, 65, respectively, are attached. Also, permanent magnets 67, 68; 67, 68 for tracking are formed separately on both sides before and after the permanent magnets 66, 66, respectively. Thus, as shown in FIG. 6 or 8, the movable lens holder 69 is provided with two tracking permanent magnets 67, 67;
Tracking coils 71 and 72, which are windings in the vertical direction, are wound around the upper and lower surfaces along the direction connecting 8 and the portions opposed to the permanent magnets 67 and 68, respectively.

Also, in the part opposing each focusing permanent magnet 66,
The focus coil 73 is formed such that portions opposed to the magnetic members 63 and 64 on both the upper and lower sides form horizontal windings.

In this reference example, the leaf springs 74, 74 forming the tracking drive mechanism are formed by forming a semi-circular loop in the middle of the C shape as shown in FIG. 6 or FIG.
In this case, the leaf springs 74, 74 and the leaf springs 15, 15 are integrally formed without using a relay member. Of course, a relay member may be used.

〔The invention's effect〕

In the optical pickup of the present invention, the lens (for example, the objective lens 18 in the above embodiment) is moved in a focusing direction (for example, the F direction in FIG. 1) which is a lens optical axis direction and a tracking direction (for example, in a direction perpendicular to the focusing direction) In order to move the lens in the direction T in FIG. 1, a surface parallel to the lens optical axis is formed in a lens holder to which the lens is fixed, and a focusing coil (for example, The focus coil 19) and a tracking coil (for example, the tracking coil 2 of the embodiment)
1, 32, 33) and an optical pickup actuator which moves the lens in the focusing direction and the tracking direction by directing a magnetic flux generated from a permanent magnet to the two coils. And coupling the focusing coil to the surface so as to wind a first axis that is the lens optical axis,
A second axis orthogonal to the first axis (for example, taking the configuration of FIG. 2 as an example, this is a horizontal axis passing through the optical axis of the objective lens 18, and the racking coil 21 is wound therearound. 4, the axis orthogonal to the objective lens optical axis and substantially passing through the center of the coil of the tracking coil 32 and the axis orthogonal to the objective lens optical axis and substantially equal to the coil of the tracking coil 33. A tracking coil wound around an axis passing through the center is coupled to the surface, and a first permanent coil is arranged along a first direction perpendicular to the axial direction of the first axis so as to sandwich the focusing coil. Magnet (for example, 2nd, 4th
A permanent magnet 5A in the figure and a second permanent magnet (for example, the permanent magnet 5B in FIGS. 2 and 4) are arranged, and the tracking coil is imaginary including the first axis and the second axis. When divided into a first coil portion and a second coil portion on a plane,
A third permanent magnet (for example, a permanent magnet 7 in the configuration of FIG. 2 and a permanent magnet 7 in the configuration of FIG. 4) configured to direct magnetic fluxes of opposite polarities to the first coil portion and the second coil portion. Magnets 34, 35), one end of an elastic member capable of displacing the lens only in both the focusing direction and the tracking direction is fixed to the lens holder, and the other end of the elastic member is fixed to the base. When the optical pickup actuator is viewed in the lens optical axis direction, the optical pickup actuator is arranged along a second direction substantially perpendicular to both the first direction and the lens optical axis direction. Since the third permanent magnet, the lens, and the elastic member are sequentially arranged, the present invention has the following effects.

While the focusing coil and the tracking coil are compactly combined in a lens holder, both the driving force of the focusing drive and the tracking drive can be generated with maximum efficiency, and as a result, the actuator of the present invention can be expected to drive with high precision There are advantages. Furthermore, the device according to the present invention has the advantage of being inexpensive due to the low assembly cost of the device.

[Brief description of the drawings]

1 to 3 show a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the first embodiment, FIG. 2 is a plan view, FIG. 3 is a sectional view taken along line AA 'of FIG. 2, FIG. 4 is a plan view of the second embodiment, and FIG. FIGS. 6 and 7 show a perspective view of a lens holder according to a second embodiment, and FIG.
FIG. 7 is a plan view, FIG. 7 is a sectional view taken along line BB 'of FIG.
FIG. 9 is a perspective view showing a lens holder used in the third embodiment, and FIG. 9 is a perspective view showing a leaf spring used in the reference example. DESCRIPTION OF SYMBOLS 1 ... Actuator 2 ... Base 3 ... Outer yoke 4a, 4b ... Inner yoke 5A, 5B ... Permanent magnet, 7 ... Permanent magnet 8 ... Magnetic member 11A, 11B, 15 ... Leaf spring 16 …… Lens holder, 18 …… Objective lens 19 …… Focus coil 21 …… Tracking coil

Claims (1)

(57) [Claims] 1. A lens holder in which a lens is fixed has a surface parallel to the lens optical axis for moving the lens in a focusing direction which is a lens optical axis direction and a tracking direction perpendicular to the lens. An optical system in which a focusing coil and a tracking coil are mounted on the lens holder so as to overlap each other, and the lens is moved in the focusing direction and the tracking direction by directing a magnetic flux generated from a permanent magnet to the both coils. In the pickup actuator, the focusing coil is coupled to the surface by winding a first axis that is the lens optical axis, and a second axis that is orthogonal to the first axis is wound. The tracking coil is connected to the surface, and the focusing coil is sandwiched. As described above, a first permanent magnet and a second permanent magnet are arranged along a first direction perpendicular to the axial direction of the first axis, and the tracking coil is further connected to the first axis and the second axis. When divided into a first coil portion and a second coil portion on an imaginary plane including the axis of?, Magnetic fluxes of opposite polarities are directed to the first coil portion and the second coil portion. A third permanent magnet is arranged, one end of an elastic member capable of displacing the lens only in both the focusing direction and the tracking direction is fixed to the lens holder, and the other end of the elastic member is fixed to the base. When the optical pickup actuator is viewed in the lens optical axis direction, the optical pickup actuator is arranged along a second direction substantially perpendicular to both the first direction and the lens optical axis direction. Third Permanent magnet, the lens, the actuator for an optical pickup that said elastic member is characterized in that it is arranged in order.