JPH0576704B2 - - Google Patents

Description

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

Conventional technology An objective lens drive device moves an objective lens along two axes, a focus direction and a tracking direction, in order to correct focus deviation due to vertical movement of a warped disk-shaped recording medium such as a compact disk, and tracking deviation due to eccentricity, etc. drive

A conventional objective lens driving device of this type is, for example, as shown in Japanese Patent Application Laid-Open No. 58-64649.
The structure was as shown in Figure 4. FIG. 4 is a perspective view of a conventional objective lens driving device, FIG. 5A is a plan view of its main parts, and FIG. 5B is a front view of its main parts.

4 and 5, first, the leaf spring 15a
The main body supported by ~15d is connected to the magnetic circuit 16
a, 16b and the tracking coil 13 in the tracking direction, the magnetic circuits 16a, 16
b and the focus coil 14 in the focus direction. When driving in the tracking direction, driving forces T ₁ and T ₂ from the two magnetic circuits 16a and 16b act on the center of gravity G of the movable part as shown in FIG.
It moves in the tracking direction supported by the deflection of the tracking plate spring portion 15b.

Similarly, when driving in the focus direction, driving forces F ₁ and F ₂ act on the center of gravity G of the movable part from the two magnetic circuits as shown in FIG. and move in the focus direction as shown by the dotted line.

The entire objective lens driving device is access-driven by a motor in the access direction (same direction as the tracking direction) shown by arrow S on the recording medium.

Problems to be Solved by the Invention However, with such a structure, the objective lens 11 swings in the tracking direction due to movement in the access direction during high-speed access required for data transfer. That is, in FIG. 5A, an inertial force _T3 due to the access drive acts on the center of gravity G of the movable part, and the objective lens 11 is driven in the tracking direction as in the case of driving in the tracking direction.

In addition, in response to disturbances in the vertical direction (same direction as the focus direction), inertia force _F3 acts on the center of gravity G of the movable part in Fig. 5B, and the objective lens is driven in the focus direction as in the case of driving in the focus direction. be done.

As mentioned above, since the objective lens drive device itself is susceptible to vertical and horizontal disturbances, the current situation is that a structure for absorbing the disturbances must be separately provided in the system in which the objective lens drive device is mounted.

Therefore, the present invention provides a stable objective lens driving device that is not affected by vertical and horizontal disturbances in driving in the focus and tracking directions.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to align the center of gravity of the movable part in the focusing direction and the tracking direction with the center of each driving force and the support point from the fixed part. , the disturbance is supported by the support system fixing part.

Effects With the above-described configuration, the present invention makes the center of gravity of the movable part in the focusing direction and the tracking direction coincide with the center of each driving force and the support point from the fixed part, so that the movement in the focusing direction and the tracking direction is controlled by each movable part. Rotating around the center of gravity, that is, the support point from the fixed part, and the position of the center of gravity does not change even if it moves, and it is resistant to disturbances in the vertical direction (same direction as the focus direction) and horizontal direction (same direction as the tracking direction). In contrast, it is supported by the support system fixing part.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1A is a plan view of an objective lens driving device in one embodiment of the present invention, FIG. 1B is a front view of the same, and FIG.
Figure A is an enlarged plan view of the same essential part, and Figure 2B is an enlarged longitudinal sectional view of the same essential part.

In FIGS. 1 and 2, 1 is an objective lens (hereinafter referred to as a lens), 2 is a lens holder that holds the lens 1, and the lens 1 and the lens holder 2 constitute a movable part. The lens holder 2 has four conical concave pivot receivers 7a and 7b symmetrically with respect to the optical axis in a plane containing the lens optical axis. The count weight 3 has the same weight as the movable part and has a pivot receiving part having the same conical recess as the lens holder.

Reference numerals 4a and 4b denote pivot plates, which are H-shaped and have pivot portions 41a and 41b with conical protrusions extending inward at both ends, and pivot receiving portions 42a and 42b with a single conical recess in the center. A part of the tip is inserted into a pivot receiving part of the recess of the movable part, and the other end is inserted into a pivot receiving part of the recess of the count weight 3, so that the movable part and the count weight 3 are rotatably supported.

A support 9 is fixed to the center of the base 10, and the support 9 has a box shape and has conical projections 9a and 9b inside the central axis parallel to the optical axis. The pivot plates 4a, 4b are rotatably supported by being inserted into pivot receiving portions 42a, 42b in the central recesses of the plates 4a, 4b.

The two pivot plates 4a and 4b are perpendicular to the optical axis,
In addition, the movable part and the count weight are positioned equidistantly across a plane passing through the center of gravity of the count weight. Further, the combined center of gravity of all movable parts, including the movable part, the countway 3, and the pivot plates 4a and 4b, is arranged on the central axis of the support body 9. 8
8d also has the function of a magnetic circuit for tracking that drives the movable part and the count weight 3 in the tracking direction in a rotational motion about the center of gravity of all the movable parts.

The operation of this embodiment will be explained below. First, a lens holder 2 holding a lens 1 and a count weight 3 having the same weight as its movable part are supported by four pivot parts each of pivot plates 4a and 4b having sufficient rigidity, as shown in FIG. 2A, By supporting the pivot receivers 42a and 42b near the center of gravity of the pivot plate by the pivots 9a and 9b fixed to the base 10 as shown in FIG.
It is balanced like a seesaw using a and 9b as fulcrums.

The movement in the tracking direction is caused by the magnetic circuit 8a,
8d, as shown in FIG. 3A, the rotational movement is made around the center of gravity _G0 of all movable parts, that is, the support point from the base 10. Even if a disturbance in the tracking direction such as high-speed access is applied, the force exerted by the disturbance on the movable part is all applied to the center of gravity _G0 , so the center of gravity is fixed to the base 10 by the support system. Therefore, if the fixed part is strong enough, the movable part is equivalent to being unaffected by disturbance.

Further, in the focus direction, magnetic circuits 8a, 8
b drives the center of gravity g of the lens holder ₂ in the focus direction, and at the same time, the magnetic circuits 8c and 8d drive the center of gravity g of the count weight ₃ in the direction opposite to that of the lens holder. Overall, Figure 3B
As shown, the rotational motion is centered around the center of gravity G ₀ of all moving parts. Even if a vertical disturbance is applied, all the force applied to the movable part will be applied to the entire movable center of gravity G ₀ point.
At this time, pivot _9a ,
9b, and the pivots 9a, 9b are fixed to the base 10, so if the fixed part is strong enough, the movable part is equivalent to not being affected by disturbance.

In this embodiment, a return mechanism for returning to the original position after driving in the focusing and tracking directions is not shown for convenience, but it goes without saying that an elastic body such as a spring may be provided.

Effects of the Invention The present invention makes the center of gravity of the movable part in the focus direction and the tracking direction of the objective lens drive device coincide with the center of each driving force and the support point from the fixed part, so that the movement in the focus direction and the tracking direction is controlled by each movable part. By rotating around the center of gravity of the part, that is, the support point, the fixed part of the support system supports against disturbances in the vertical direction (same direction as the focus direction) and the horizontal direction (same direction as the tracking direction). , even if the above-mentioned disturbance occurs at the movable center of the objective lens drive device, the drive in the focus direction and the tracking direction is not affected at all, so it is possible to easily design a system in which the objective lens drive device is mounted. It is possible.

[Brief explanation of the drawing]

1A is a plan view of an objective lens drive device according to an embodiment of the present invention, FIG. 1B is a front view of the same objective lens drive device, FIG. 2A is an enlarged plan view of the same essential parts, and FIG. 2B 3A is a plan view of the main part showing the function of the objective lens, FIG. 3B is a front view of the main part, and FIG. 4 is a perspective view showing a conventional objective lens drive device. 5A is a plan view of the same essential part, and FIG. 5B is a front view of the same essential part. 1... Lens, 2... Lens holder, 3... Count weight, 4a, 4b... Pivot plate, 5
a, 5b...Focusing coil, 6...Tracking coil, 7...Pivot receiver, 8a to 8d
...Magnetic circuit, 9a, 9b...Pivot, 10...
…base.

Claims (1)

[Claims] 1. An objective lens 1 of a device for optically writing or reading information on a recording medium is aligned with the optical axis in a direction perpendicular to the surface of the recording medium, that is, in the optical axis direction (hereinafter referred to as the focus direction). An objective lens driving device that drives in a vertical radial direction (hereinafter referred to as tracking direction), which has four conical recesses symmetrical to the optical axis in a plane that includes the objective lens 1 and its optical axis. A movable part consisting of a lens holder 2, a count weight 3 which has the same weight as the movable part and has the same conical recess as the lens holder, and a count weight 3 which is H-shaped and has conical protrusions extending inward at both ends. is inserted into the recess of the movable part and the other end is inserted into the recess of the count weight to be rotatably supported, and there are two sufficiently rigid pivot plates 4a and 4b with one recess in the center, and a box-shaped pivot plate. , a support body 9 having a conical protrusion inside the central axis of the box, being inserted into the recess at the center of the two pivot plates to rotatably support the pivot plates, and fixed to the center of the base 10; one or more focusing magnetic circuits that drive the center of gravity of the movable part and the count weight in the focusing direction; and one that rotates around the combined center of gravity of the movable part and the count weight and drives it in the tracking direction. An objective lens driving device characterized by comprising one or more tracking magnetic circuits. 2. The two pivot plates 4a and 4b are arranged in parallel and are positioned equidistantly across a plane that includes a straight line connecting each center of gravity of the movable part and the count weight 3 and is perpendicular to the optical axis. Claim 1
The objective lens drive device described in .