JPS61216135A - Objective lens driver - Google Patents

Abstract

PURPOSE:To prevent the generation of the undesired resonance and cross actions with high band frequencies by using the 1st yoke interlocking a bearing part provided to a mobile member to perform the focusing and tracking drives in a free rotary support state. CONSTITUTION:The 1st yoke 21 functions as a support shaft which interlocks with play a bearing part 20a provided to a mobile member 20 and supports a mobile matter 34 in a rotatable state. The member 20 contains a pair of T-shaped cut parts 20e and 20f where each end of resetting rubber members 30 and 31 is inserted and fixed by adhesion respectively. While the other end of each resetting rubber members is fixed to the projected parts 25c and 25d via the resetting rubber holders 32 and 33. Thus the matter 34 is kept at the neutral position in the tracking direction. The parts 25c and 25d also functions to control so that the turning angle of the matter 34 does not exceeds the fixed value.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a disk-shaped recording medium (hereinafter referred to as a disk).
In an optical recording and reproducing device that records or reproduces information on a disk, an objective lens that controls the position of the objective lens relative to the disk surface in order to accurately correct and control the position of the light spot with respect to the information track. This relates to a drive device.

2. Description of the Related Art In general, an optical recording/reproducing device includes a focusing control mechanism for driving and controlling an objective lens in the optical axis direction of an optical system, and a focusing control mechanism for driving and controlling the objective lens in a direction perpendicular to the optical axis direction. A tracking control mechanism is required. The former is used to correctly focus a light beam onto the disk surface on which various information such as video signals is recorded, while the latter is used to focus the light beam onto information tracks recorded spirally or concentrically on the disk surface. It is impossible to make it follow correctly.

In conventional focusing control mechanisms and tracking control mechanisms, the objective lens is supported by a suspension mechanism using an elastic support member such as a metal spring or rubber, and the objective lens is moved in the focusing direction and the tracking direction by electromagnetic force generated by a coil and a magnet. A driving method is known.

A conventional objective lens driving device will be explained below. FIG. 5 is a sectional view of a conventional objective lens driving device. 1 is a semiconductor laser, 2 is an optical axis, 3 is a reflecting mirror, 4 is an objective lens, 5 is a disk, 6 is a lens barrel, 7a and 7b are tracking drive coils, 8a and sb are tracking drive magnetic circuits, 9 is a focusing The drive coil, 1o is a focusing drive magnetic circuit, and 11.12 is an elastic support member.

The operation of the conventional objective lens drive device configured as described above will be described below.

When a tracking correction current is applied to the tracking drive coils 7a, 7b from a tracking error detection circuit (not shown), an electromagnetic force based on Flessing's left hand rule is generated between the tracking drive magnetic circuits 8a, 8b, and the objective The lens 4 has an elastic support part, lJ'1, in the X-X direction in the figure.
Tracking control is performed by moving in balance with the elastic force of 1.12.

Similarly, focusing control is performed based on the electromagnetic force generated between the focusing drive coil 9 and the focusing drive magnetic circuit 1°.

Problems to be Solved by the Invention By the way, when the objective lens 4 is supported by using the elastic support members 11 and 12 as metal springs, there is a drawback that the metal springs themselves resonate at high frequencies.

In fact, if the objective lens 4 is supported by using elastic support members 11 and 12 as rubber, the drawbacks of metal springs as described above are overcome, but cross action due to the interaction between focusing and tracking may occur. A disadvantage arises that the position of the objective lens 4 becomes unclear.

The present invention solves the problems of the suspension mechanism using an elastic support member, such as the occurrence of resonance at high frequencies and the occurrence of cross action, and has a small size and high performance that drives the objective lens in two substantially orthogonal directions with a simple configuration. The object of the present invention is to provide an objective lens driving device.

Means for Solving the Problems In order to solve the above problems, the present invention provides a movable member that is provided with a focusing drive magnetic circuit and a tracking drive magnetic circuit, and a focusing coil and a tracking coil are arranged to interact electromagnetically with these. A bearing part is provided in the movable member, an objective lens is disposed at a position eccentric to the axis of the bearing part of the movable member, and a part of the yaw constituting the focus magnetic circuit is made loose with the bearing part. The movable member is slidably supported as a mating support shaft.

j Effect 1 Oh □. □2o, ga, ya,, Kara 2,7 (
Focusing drive and tracking drive of 61.
- By using a slidable and rotatable support and eliminating a suspension mechanism based on elastic support, unnecessary resonance and cross action at high frequencies are eliminated, and a part of the yoke that forms the focus drive magnetic circuit is eliminated. This is intended to reduce the size of the device by using it as a support shaft for the sliding and rotation of the movable member.

EXAMPLE Hereinafter, an example of an objective lens driving device according to the present invention will be described in detail with reference to the drawings.

1 is an exploded perspective view, FIG. 2 is an overall perspective view, FIG. 3 is a plan view, and FIG. 4 is a sectional view taken along line A-0-B in FIG. 3.

The movable member 20 includes a bearing portion 20a having an axis parallel to an optical axis (not shown), and an objective lens 22 is fitted into a hole 20b provided eccentrically from the axis of the bearing portion 20a. It is fixed. Furthermore, a focus coil 23 is wound and fixed to a cylindrical part 20c that is provided coaxially with the bearing part 20a and forms a part of the movable member, and a tracking coil 24 wound in a substantially rectangular shape is wound to a protrusion part 20d. It is fixed.

A shaft-shaped first yaw 21 is installed in a hole 25a provided in a part of the fixed part 25, and a first yaw 21 is fixed to the fixed part 25 in a spaced apart manner on the outer periphery of the first yaw 21. A focus drive magnetic circuit is constituted by an annular first magnet 26 and a second yaw 27 which is further fixed to the first magnet and is arranged so as to have an air gap with the first yoke.

The fixing member 25 is spaced apart from the outer periphery of the second yaw 27.
A second magnet 28.
29 are fixed so that their magnetic poles are in opposite directions to form a tracking drive magnetic circuit.

The first yoke 21 functions as a support shaft that plays with a bearing portion 20a provided on the movable member 20, and supports the movable body 34 in a slidable manner.

The movable member 2o has a pair of T-shaped notches 20e.

2Of is provided, and one end of the return rubber 30 and 31 is inserted therein and fixed with adhesive.

Further, the other ends of the return rubbers 30, 31 are fixed to the projections 25C, 25d by return rubber holders 32, 33, respectively, and these return rubbers 30, 31 keep the movable body 34 at a neutral position in the tracking direction. There is. The projections 25c and 25d also restrict the rotation of the movable body 34 so that it does not rotate beyond a certain angle.

The focus coil 23 is disposed in a magnetic gap formed by the first yoke 21 and the second yoke 27, and is configured to generate electromagnetic force between it and the focus drive magnetic circuit. The tracking coil 24 uses vertical sides a and b for tracking drive.
The side a of the tracking coil 24 is placed at a position opposite to the second magnet 28 that generates a magnetic field in one direction in the radial direction, and the side a of the tracking coil 24 is placed opposite to the second magnet 29 that generates a magnetic field in the other direction in the radial direction. By arranging the side of the tracking coil 24 at the same position and making the directions of the magnetic fields applied to side a and side of the coil opposite to each other, the electromagnetic force acting on side a and side of the coil can be made to be the same. I try to align it in the correct direction.

Effect of the invention 9 - As mentioned above, the conventional objective lens drive device using a suspension mechanism made of an elastic support member has drawbacks such as the occurrence of resonance at high frequencies and the occurrence of cross action. The objective lens driving device according to the present invention allows the first yoke that engages with the bearing provided on the movable member to act as a support shaft to support the movable body in a slidable and rotatable manner. The objective lens, which is held at an eccentric position relative to the axis of the bearing, is driven in two substantially perpendicular directions by electromagnetic force generated by a coil and a magnet, which solves the drawbacks of the prior art described above.

The diameter (corresponding to the area in FIG. 3) of the focus drive magnetic circuit can be reduced by allowing a part of the yoke constituting the focus drive magnetic circuit to act as a support shaft. In other words, the movable member can be made smaller in the radial direction, the weight of the movable body and the moment of inertia can be reduced, and a compact, high-performance objective lens driving device can be realized.

1o...-

[Brief explanation of drawings]

1, 2, 3, and 4 are an exploded perspective view, an overall perspective view, a plan view, and a sectional view of an objective lens driving device according to an embodiment of the present invention, and FIG. 5 is a conventional objective lens drive device. It is a sectional view of a lens drive device. 2o: Movable member, 20a: Bearing portion, 21: First yoke, 22: Old objective lens, 23: Focus coil, 24...
...Tracking coil, 26...Fixing member, 26b...Third yoke, 26...
1st magnet, 27... Group 2nd yoke, 28° 29.
...Second magnet, 30.31...Returning rubber, 32.33...Returning rubber holder. Name of agent: Patent attorney Toshio Nakao (1 person)
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Claims (1)

[Claims] a movable member having a bearing portion; an objective lens held at a position eccentric to the axis of the bearing portion of the movable member; a first shaft-shaped yoke mounted on a fixed member; an annular first magnet fixed to the fixing member while being spaced apart from the outer periphery of the first yoke; a second annular yoke disposed, a third yoke protruding from the fixing member in a spaced apart manner from the outer periphery of the second yoke, and a second yoke fixed to the third yoke. and a first yoke wound along a cylindrical surface coaxial with the bearing extending from the movable member and disposed in the magnetic gap formed by the first yoke and the second yoke. and a coil of
a second coil wound in a substantially rectangular shape fixed to the movable body and disposed to face the second magnet with an air gap; An objective lens driving device characterized in that the movable member is slidably and rotatably supported with respect to the first yoke as a support shaft that engages with the bearing portion.