JPH0786980B2 - Objective lens drive - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device of an apparatus for optically writing or reading information.

2. Description of the Related Art An objective lens driving device is used for a focus shift due to a vertical movement of a warp of a disc-shaped recording medium such as a compact disc,
In order to correct tracking deviation due to eccentricity or the like, the objective lens is driven in two axes of the focus direction and the tracking direction.

A conventional objective lens driving device of this type is disclosed in, for example, JP-A-58-58.
As shown in Japanese Patent No. 64649, the structure was as shown in FIG.

That is, the main body having the lens 14 supported by the leaf springs 18a to 18d is attached to the magnetic circuits 19a and 19b and the tracking coil 1
Tracking direction T by electrokinetic converter using 6
_{At r} , the focus F ₀ is driven by the electrokinetic converter using the magnetic circuits 19a and 19b and the focusing coil 17. The movement is driven by the driving forces T ₁ and T ₂ generated from the two magnetic circuits with respect to the center of gravity g _{0 of the} movable part as shown in FIG. It is supported by the flexure of its body and moves in the tracking direction.
Similarly, when driving in the focus direction, the driving force from the two magnetic circuits is applied to the center of gravity g _{0 of the} movable portion as shown in FIG. 5 (B).
F ₁ and F ₂ are actuated to move in the focusing direction while being supported by the deflection of the leaf spring for focusing of the leaf spring.

In addition, the entire objective lens driving device is access-driven by a motor in the access direction A _C (the same direction as the tracking direction) on the recording medium.

However, in such a structure, the objective lens swings in the tracking direction due to movement in the access direction at the time of high-speed access required for data transfer or other impact, that is, In FIG. 5 (A), the inertial force T ₃ due to the access drive acts on the center of gravity of the movable portion, and the objective lens is driven in the tracking direction as in the case of driving in the tracking direction.

As described above, since the objective lens driving device itself is weak against shock, even a compact disc player may cause skipping due to shock while moving, or a recording error may occur when writing data in a data recording system. Therefore, it is the current situation that a structure for absorbing the impact must be separately provided in the system for mounting the objective lens driving device.

Therefore, the present invention provides a stable objective lens driving device that is not affected by such impact during driving.

Means for Solving the Problems The present invention allows a first movable part composed of an objective lens and a lens holder, and a shaft or a pivot part to rotate only in a tracking direction which is parallel to the recording medium surface and is a radial direction. The fixed second movable part is configured such that the center of gravity of all the movable parts is located on the axis or pivot part, and only the first movable part is an optical axis perpendicular to the recording medium surface. A leaf spring that connects the first movable portion and the second movable portion with a shape having high rigidity in a direction parallel to the surface of the recording medium so that the first movable portion and the second movable portion can be moved in a focus direction that is a direction. 1, a spring member for returning to the original position after the second movable portion moves in the tracking direction, a magnetic circuit for focusing for driving the first movable portion in the focus direction, How to track 2 movable parts It has a configuration that includes a tracking magnetic circuit which drives the.

Action The present invention has the above-described configuration, and even if the first and second movable parts are moved, the position of the center of gravity of the total movable part does not change, and the support system fixed part supports the shock against the shock. Not affected. Further, by the configuration including the tracking magnetic circuit for driving each of the first and second movable parts in the tracking direction, it is possible to respond at high speed in the tracking direction.

Further, the optical system other than the objective lens is separated, and the first movable portion and the second movable portion are provided so that only the first movable portion including the objective lens can move in the focus direction. Since it is connected and supported by a leaf spring that is configured to have a high rigidity in the parallel direction, it is possible to obtain a large stroke in the focus direction while responding to high speed response in the focus direction despite its compact shape. It is possible, and the leaf spring itself can be integrally rotated around the rotation axis even when driven in the tracking direction without bending.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 (A) is a plan view of the objective lens driving device of the present embodiment, and FIG. 1 (B) is a front view of the same, showing a state in which the base portion and the movable portion are assembled. Further, FIG. 6 is an exploded perspective view showing the movable portion and the base portion (fixed portion) separately.

Reference numeral 1 denotes an objective lens (hereinafter referred to as a lens) of a device that optically writes or reads information on a recording medium. Reference numeral 2 denotes a lens holder that holds the lens 1. The lens 1 and the lens holder 2 constitute a first movable portion. To do. Reference numeral 3 denotes a second movable portion which is rotatably fixed only by a shaft 5 in a tracking direction which is parallel to the surface of the recording medium and which is a radial direction. The center of gravity of all the movable portions is located at the center of the shaft 5. It is configured. Reference numerals 4a to 4d denote leaf springs that connect only the first movable portion and the first and second movable portions so as to be movable in the optical axis direction perpendicular to the recording medium surface, that is, the focus direction, 6 is a bearing, 7 is an elastic material attached to a part, one side or both sides of the leaf springs 4a to 4d, and the elastic material 7 prevents resonance of the leaf springs. 8 is a spring material for returning the first and second movable parts to their original positions after moving in the tracking direction, and 9a and 9b are magnetic materials for driving the first movable part in the focus direction. Circuit, 9a, 9c are the first,
A magnetic circuit for driving the second movable part in the tracking direction, 10 a fixed system part, 11 a focusing coil, 12
Is a tracking coil, and 13 is a base. As shown in FIG. 6, the magnetic circuits 9a, 9b and 9c are formed in the base 13 and are composed of a yoke and a magnet. A focusing coil and a tracking coil are arranged in the magnetic gap between the yoke portion and the magnet portion to obtain a driving force.

The operation of the present embodiment configured as described above will be described below.

First, the movement in the tracking direction is shown in FIG. 2 (A) by the driving forces F ₁ and F ₂ generated from the magnetic circuits 9a and 9c and the coil 12.
As shown in, the center of gravity G of all movable parts (hereinafter referred to as the center of gravity G),
That is, the rotational movement from the base 13 about the axis 5 is performed. At this time, the driving forces F ₁ and F ₂ are adjusted as follows so that an unreasonable force is not applied to the leaf springs 4a to 4d.

FIG. 3 shows the configuration of the present embodiment simplified for explaining the operation. In FIG. 3, G is the center of gravity of the shaft and the entire system, m ₁ and m ₂ are the masses of the movable parts, l ₁₀ and l ₂₀ are the distances from the shaft to the center of gravity of the movable parts, and l ₁ and l ₂ are the axes. The distance to the point of action of each driving force, f ₁ , f ₂ is the force acting on the center of gravity of each movable part, F ₁ ,
F ₂ is each driving force, and θ ₁ and θ ₂ are each displacement angle t seconds after the start of driving.

That is, in the model diagram of FIG. 3, the force exerted by the center of gravity G
f ₁ and f ₂ are expressed by the following equation (1).

Here, since the center of gravity of the entire system is the center of gravity G point, the following (2)
The formula holds.

m ₁ l ₁ = m ₂ l ₂ (2) If the leaf springs that connect the movable parts are rigid, then θ ₁
= Θ _2, that is, the angular acceleration becomes constant, and the following expression (3) is established. ₁ = ₂ (3) From equations (1) to (3), equations (4) and (5) hold.

f ₁ = f ₂ (4) By rearranging the equations (4) and (5), the following equation (6) is established.

If the driving force F ₁ F ₂ is adjusted by the equation (6), it can be seen that even if the rigidity of the leaf spring is small, an unreasonable force is not applied to the leaf spring.

Further, even if an impact is applied in the tracking direction _Tr such as high-speed access, all the force exerted on the movable part by the impact is applied to the center of gravity G, so that the center of gravity is fixed to the base 13 by the shaft 5 which is the support system. As a result, if the fixed portion and the leaf spring have sufficient lateral rigidity, it is equivalent to that the movable portion is not affected by the impact at all.

In the focus direction F ₀ , the magnetic circuits 9a and 9b and the coil 1
The driving force F ₃ generated by 1 drives the center of gravity g ₁ of the lens holder 2 including the lens in the focus direction F ₀ . At this time, since the leaf springs 4a to 4d supporting the movable portion are connected on the extension line 1 from the center of gravity as shown in FIG. 2B, there is no dynamic disturbance of the movable portion due to driving.

In order to suppress higher-order resonance of the leaf spring, an elastic material such as rubber may be attached to at least one of the front surface and the back surface of the leaf spring with an adhesive.

According to the present invention, the center of gravity of the movable portion of the objective lens driving device in the tracking direction is made to coincide with the center of the support system such as the shaft or the pivot, and the movement in the tracking direction is supported by the center of gravity of the movable portion, that is, the support of the shaft or the pivot. Since the system is rotated around the system, the support system fixing part supports the impact in the direction perpendicular to the optical axis, so even if the objective lens driving device is in operation, it is not affected by the impact as described above. Since there is no effect, the system for mounting the objective lens driving device can be easily designed.

Further, the optical system other than the objective lens is separated, and the first movable portion and the second movable portion are provided so that only the first movable portion including the objective lens is movable in the focus direction. Since it is connected and supported by a leaf spring that is configured to have a high rigidity in the parallel direction, it is possible to obtain a large stroke in the focus direction while responding to high speed response in the focus direction despite its compact shape. It is possible, and the leaf spring itself can be integrally rotated around the rotation axis even when driven in the tracking direction without bending.

[Brief description of drawings]

1 (A) is a plan view of an objective lens driving device according to an embodiment of the present invention, FIG. 1 (B) is a front view of the objective lens driving device, and FIG. 2 (A) is the same objective lens driving device. 2B is a front view of the main part, FIG. 3 is a model diagram showing the function of the objective lens driving device, and FIG. 4 is a conventional objective lens driving device. 5A is a perspective view, FIG. 5B is a front view of the main part, and FIG. 6 is an exploded perspective view showing the movable part and the base part (fixed part). . 1 ... Lens, 2 ... Lens holder, 3 ... 2nd movable part, 4a-4d ... Leaf spring, 8 ... Spring material, 9a-9c ... Magnetic circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaei Sato 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toru Nakamura, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP 59-178631 (JP, A) JP 58-169345 (JP, A)

Claims (4)

[Claims] 1. A tracking which is parallel to the surface of the recording medium and is radial by a first movable part comprising an objective lens and a lens holder of a device for optically writing or reading information on the recording medium, and an axis or pivot part. A second movable portion fixed rotatably only in the direction, such that the center of gravity of all the movable portions is located on the shaft or pivot portion, and only the first movable portion has the recording medium surface. The first movable portion and the second movable portion are connected to each other in a shape having high rigidity in a direction parallel to the recording medium surface so as to be movable in a focus direction which is an optical axis direction perpendicular to One or a plurality of leaf springs, one or a plurality of spring members for returning to the original position after the first and second movable parts move in the tracking direction, and the first and second leaf springs. How to focus the moving part An objective including one or a plurality of focusing magnetic circuits for driving in the tracking direction and one or a plurality of tracking magnetic circuits for driving the first and second movable parts in the tracking direction. Lens drive device. 2. The objective lens driving device according to claim 1, wherein an elastic material such as rubber is adhered to at least one of the front surface and the back surface of the leaf spring. 3. The center of the driving force generated from the magnetic circuit for focusing and the center of gravity of the first movable portion are aligned with each other, and are supported by the leaf spring on the extension line of the center of gravity of the first movable portion in the tracking direction. The objective lens driving device according to claim 2, wherein 4. A first tracking magnetic circuit for driving the first movable portion in the tracking direction, and a second tracking magnetic circuit for driving the second movable portion in the tracking direction, each movable. 4. The objective lens driving device according to claim 3, wherein the magnetic circuits are adjusted so that the driving forces of the magnetic circuits applied to the center of gravity of the parts are substantially equal to each other.