JPS63121140A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to improve a driving force, by arranging a cylindrical coil perpendicularly to an optical axis on a second movable part side, and arranging a tracking magnetic circuit so that a magnet is positioned at the outside of the cylindrical coil and also on a side opposite to a recording medium plane, and an inner yoke is positioned in the inside of the cylindrical coil. CONSTITUTION:By arranging the tracking magnetic circuit 9c on the second movable part 3 side so that the tracking cylindrical coil 14 is arranged perpendicularly to the optical axis, and the magnet 13 is arranged at the outside of the tracking cylindrical coil 14 and also on the side opposite to the recording medium plane, and the inner yoke at the inner side of the cylindrical coil 14, the shape of the second movable part 3 can be simplified. Also, by arranging the magnet 13 perpendicularly to the optical axis, and also, in parallel with the second movable part 3, the shape of an objective lens driving device can be formed in a small size, and furthermore, coil effective length can be increased compared with a flat coil. In such way, it is possible to facilitate processing, to miniaturize the device, and to improve the driving force.

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 Objective lens drive devices drive the objective lens in two axes, the focus direction and the tracking direction, in order to correct focus deviations due to vertical movement of warped recording media such as compact discs, and tracking deviations due to eccentricity, etc. It is configured as follows.

A conventional objective lens driving device of this type is shown in Fig. 3.

It had a structure like B.

That is, 1 is an objective lens of a device for optically writing or reading information on a recording medium, 2 is a lens holder that holds this objective lens 1, and the objective lens 1 and lens holder 2 are in a first movable state. 3 is a second movable part fixed rotatably only in the tracking direction Td by a shaft 6. Magnetic circuit ga, sb and focusing coil 1
1, the driving force generated from the 1st. Only the first movable section is movable in the focus direction Fd via leaf springs 4a to 4d that connect it to the second movable section. Also,
Magnetic circuit 91L, 9Cj and tracking j coil 12
The first and second movable parts rotate about the shaft 5 due to the driving force generated from the shaft 5. At this time, the tracking spring 8 attached to the second movable part 3 returns the movable part to its original position.

Problems to be Solved by the Invention However, with such a structure, the second movable portion 3 has a complicated shape as shown in FIG. 4, making it difficult to process the parts. Furthermore, if the magnetic circuit 9C on the second movable part 3 side is vertical as shown in FIG. 3, the shape of the objective lens driving device becomes long. Furthermore, in order to make the center of gravity of all movable parts near the axis 6, the weight of the second movable part 3 becomes heavy, and in the flat tracking coil 12 as shown in FIG. There were problems such as limited space to increase the generated driving force.

Accordingly, the present invention provides an objective lens driving device that includes a second movable portion that is easy to process, and that can further be downsized and improve driving force.

Means for solving the problem The technical means of the present invention for solving the above problem is to arrange a cylindrical coil perpendicular to the optical axis on the second movable part side,
The tracking magnetic circuit is arranged such that the magnet is placed outside the cylindrical coil and on the side opposite to the surface of the recording medium, and the inner yoke is placed inside the cylindrical coil.

action The effect of this technical means is as follows.

That is, in the tracking magnetic circuit on the second movable part side, a cylindrical coil is arranged perpendicular to the optical axis, and a magnet is placed outside the cylindrical coil and on the side opposite to the recording medium surface.
By arranging the inner yoke and the inner yoke inside the cylindrical coil, the shape of the second movable part is simplified;
Furthermore, by arranging the magnet perpendicular to the optical axis and parallel to the second movable part, the shape of the objective lens driving device can be shortened, and unlike a flat coil, the driving force in the tracking direction can also be improved. I can do it.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a plan view of the objective lens driving device of this embodiment.
FIG. 1B is a front view of the same. In the figure, components having the same configuration as those of the conventional example are designated by the same numerals and explanations thereof will be omitted. Objective lens 1
and lens holder 2 are first movable parts, and 3 is a second movable part fixed rotatably only in the tracking direction T11 by shaft 6. The first. Only the first movable part can be moved in the focus direction F (1) via the focusing leaf springs 4 & ~ 4d that connect the second movable part. The generated driving force causes the first p
The second movable part rotates around the shaft 6, and the tracking spring 8 attached to the second movable part 3 returns the movable part to its original position.

Furthermore, FIG. 2 is a perspective view of the second movable part 3 of the objective lens drive device of this embodiment, which is much easier to process than the second movable part 3 of the conventional objective lens drive device shown in FIG. A tracking cylindrical coil 1 is attached to a second movable part 3 having a prismatic shape.
It is constructed by pasting 4.

By attaching the magnet 13 of the magnetic circuit 9J 90 on the second movable part 3 side to the base 10 as shown in FIG. Tracking coil 12
However, with a flat coil, the coil effective length is short and it is difficult to obtain thrust, but with the tracking cylindrical coil 14 as shown in FIG. 2, the coil effective length is large and it is easy to obtain thrust. In addition, 6 in the figure
is a bearing of the shaft 6, and 7 is a viscoelastic body provided on the leaf springs 4&~4d.

Here, in this embodiment, the direction of the driving force generated from each coil in the tracking direction Td is F&~Fc in Fig. 1.
The relationship is as follows.

Effects of the Invention The present invention is an objective lens drive device that obtains drive in the tracking direction by rotating around an axis, and the tracking magnetic circuit on the second movable part side is moved so that the tracking cylindrical coil is aligned with the optical axis. The second movable part In addition, by arranging the magnet perpendicular to the optical axis and parallel to the second movable part, the shape of the objective lens drive device can be shortened, and the coil effectiveness is improved compared to a flat coil. Since the length is shortened, the driving force in the tracking direction is also improved, so that it is possible to design an objective lens driving device that is easy to process, downsized, and can improve the driving force.

[Brief explanation of the drawing]

FIG. 1 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, FIG. 2 is a perspective view of a second movable part of the objective lens drive device, and FIG. FIG. 3B is a front view of the conventional objective lens driving device, and FIG. 4 is a perspective view of a second movable part of the conventional objective lens driving device. 1... One objective lens, 2... Lens holder,
3...-second movable part, 41L to 4d...
Leaf spring, 6... shaft, 6... bearing, 8...
...Tracking spring, 9&~9C...
Magnetic circuit, 1o...Base, 11...
Focusing coil, 13... Magnet, 1
4...-Typical coil for tracking. heart f7 7J 2nd figure 3rd figure

Claims (1)

[Claims] Drives the objective lens of a device that optically writes or reads information on a recording medium in the focusing direction, which is perpendicular to the surface of the recording medium and in the direction of the optical axis, and in the tracking direction, which is perpendicular to the optical axis and in the radial direction. In order to do this, a first movable part consisting of the objective lens and a lens holder that holds the objective lens, and a second movable part fixed rotatably only in the tracking direction by a shaft or the like, are attached to the shaft. one or more leaf springs connecting the first and second movable parts so that the center of gravity of all the movable parts is located, and only the first movable part can move in the focusing direction; , one or more tracking springs for returning the first and second movable parts to their original positions after moving in the tracking direction, and one for driving the first movable part in the focus direction. one or more focusing magnetic circuits, and one or more tracking magnetic circuits that drive the first and second movable parts in the tracking direction, the tracking on the second movable part side. A tracking cylindrical coil is arranged perpendicularly to the optical axis, a magnet is placed outside the tracking cylindrical coil and on the side opposite to the recording medium surface, and an inner yoke is placed outside the cylindrical coil. Objective lens drive device placed on the inside.