JPH0445894B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording and reproducing apparatus that records or reproduces information on a disk-shaped information recording medium (hereinafter referred to as a disk) using a laser or the like as a light source. The present invention relates to an optical pickup device that performs focusing control to correct focus deviations caused by shake, etc., and tracking control to correct tracking deviations caused by disk eccentricity, etc.

Conventional configurations and their problems In recent years, with the practical use of optical recording and reproducing devices such as video disks, DADs, and optical disk files, there has been a need for smaller optical pickups and higher performance.
It's increasing. First, an example of a conventional optical pickup device will be explained. FIG. 1 is a sectional view of a conventional optical pickup device. In Figure 1, 1 is a semiconductor laser, 3 is a reflection mirror, 4
is the objective lens, 5 is the disk, 6 is the lens barrel,
7a, 7b are tracking drive coils; 8a,
8b is a tracking drive magnetic circuit, 9 is a focusing drive coil, 10a, 10b, and 10c are focusing drive magnetic circuits, 11 and 12 are elastic support members, and 2 is an optical axis. XX indicates the radial direction of the disk 5, and ZZ indicates the thickness direction of the disk 5.

The operation of the conventional optical pickup configured as described above will be explained below.

From the tracking error detection circuit (not shown),
When the tracking correction current is applied to the tracking drive coils 7a, 7b, an electromagnetic force based on Fleming's left hand rule is generated between the tracking drive magnetic circuits 8a, 8b, and the objective lens 4 moves in the X-X direction in the figure. Then, tracking control is performed by moving in a manner that balances the elastic forces of the elastic support members 11 and 12. Similarly, focusing control is performed by electromagnetic force generated between the focusing drive coil 9 and the focusing drive magnetic circuits 10a to 10c.

However, in the device configured as described above, the tracking drive coils 7a and 7b and the focus drive coil 9 are arranged separately above and below the lens barrel 6, and the magnetic fields for tracking and focusing are different from each other. Since the circuit forms a completely closed magnetic path, gaps a, b, c, and d provided for movement during focus drive as shown in FIG. 1 are required, which increases the height of the optical pickup. Therefore, it has the disadvantage that it is difficult to make the entire optical recording/reproducing device thinner, and the XX direction of the magnetic circuit 8 and the magnetic circuit 10, that is, the disk 5
Since the radial dimension of the disc 5 is large, it has the disadvantage that the inner peripheral part of the disc 5 cannot be used effectively. Furthermore, the structure of the focus and tracking driving magnetic circuits is complicated, and it is necessary to position a coil in each magnetic gap, making the assembly work complicated.

Purpose of the Invention The present invention aims to eliminate the above-mentioned conventional drawbacks, such as not being able to effectively use the inner circumference of the disk, and the drawback that the magnetic circuit becomes complicated. The object of the present invention is to reduce the directional dimension, effectively utilize the inner circumference of the disk, simplify the structure of the focus and tracking drive magnetic circuit, and improve the ease of assembly.

Structure of the Invention The present invention provides a lens barrel housing an objective lens for converging light emitted from a light source onto a disk-shaped information recording medium, and a coil axis is attached to the outer periphery of the lens barrel. A first coil is wound so that the coil axis coincides with the optical axis, and a second coil is wound so that the coil axis coincides with the radial direction of the recording track formed on the disk-shaped information medium. , having a magnetic pole in the tangential direction of the recording track,
In the optical pickup device, magnets are arranged such that magnetic poles face the winding surfaces of the first coil and the second coil.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 2 and 3, a focus drive coil 15 is wound around a lens barrel 14 housing an objective lens 13. Therefore, the coil axis of this focus drive coil 15 coincides with the optical axis of the objective lens 13. Next, the tracking drive coils 16a and 16b are placed on the protruding part of the lens barrel 14 so that the focus drive coil 15 is slightly spaced apart from the focus drive coil 15 as shown in the figure.
fixed at the same height. The coil axes of the tracking drive coils 16a and 16b are connected to the objective lens 13.
This corresponds to the radial (XX) direction of the recording track of the disk, which is illuminated by the light that has passed through it. Yoke plate 19
Drive magnet units 21a and 21b with magnets 20a and 20b attached to coils 1 and 19b are connected to coil 1.
5, 16a, and 16b. At this time, the magnets 20a and 20b are arranged so that their north poles face each other.

Therefore, the magnets 20a and 20b generate magnetic flux that interlinks from the magnets 20a and 20b side to the lens barrel 14 side with respect to the two sides of the focus drive coil 15 wound in the XX direction. That is, opposing magnetic fluxes are generated. On the other hand, the currents flowing in the XX direction on these two sides flow in opposite directions. Further, the magnets 20a and 20b generate magnetic flux that interlinks from the magnets 20a and 20b side to the lens barrel 14 side for each of the two sides wound in the ZZ direction of the tracking drive coils 16a and 16b. That is,
Generates opposing magnetic flux. On the other hand, ZZ on these two sides
Currents flowing in one direction flow in opposite directions. Therefore, the focusing drive coil 15 and the tracking drive coils 16a and 16b each have 2
The driving force acting on the sides acts as a resultant force.

Now, in a magnetic circuit that does not constitute a closed magnetic path, such as the drive magnet units 21a and 21b, the yoke plates 19a and 19b direct magnetic flux in the direction of the lens barrel 14, that is, the focus drive coil 15 and the tracking drive coils 16a and 16b. The magnetic flux density in front of the magnetic pole, that is, on the lens barrel 14 side, is approximately inversely proportional to the square of the distance from the magnetic pole surface.
In this embodiment, the end portions of the focus drive coil 15, tracking drive coil 16a, and coil 16b are arranged at positions approximately equal distances from the magnets 20a and 20b, as shown in the figure. These items are housed in a housing 17, with elastic support members 18 at the top and bottom.
They are held together by a and 18b.

In Figures 2 and 3, XX is the radial direction of the recording track formed on the disk, and ZZ is the radial direction of the recording track formed on the disk.
indicates the thickness direction of the disk, and YY indicates the tangential direction of the recording track on the disk.

Next, the operation of this device will be explained. When a focus drive current based on a focus error signal detected by a focus error detection circuit (not shown) flows through the focus drive coil 15, the magnetic flux generated by the magnet units 21a and 21b and
A driving force based on Fleming's left-hand rule is generated in the ZZ direction between the current flowing in the XX direction and the current flowing in the XX direction.
The elastic support members 18a and 18b due to this driving force
By displacing in the ZZ direction, the objective lens 13 moves and focus control is performed. In tracking control, similarly to focus control, when a tracking drive current based on a tracking error signal flows through the coils 16a and 16b, the magnet unit 2
A driving force based on Fleming's left hand rule is generated in the XX direction between the magnetic flux emitted by 1a and 21b and the current flowing in the ZZ direction. As the elastic support members 18a and 18b are displaced in the XX direction by this driving force, the objective lens 13 is moved in the XX direction and tracking control is performed.

In addition, in the above-mentioned embodiment, the coils 16a, 16
(b) Although the magnet units 21a and 21b are provided, only one coil or one magnet unit may be used. Further, although the coil 15 and the coils 16a, 16b are provided in an overlapping manner, the lens barrel 14 may be made longer, and the coils 15, 16a, 16b may be overlapped.
may be arranged vertically. In this case, the magnet units 21a and 21b also need to be lengthened in the vertical direction.

Effects of the Invention As described above, according to the present invention, since the magnets provided opposite to the focus drive coil and the tracking drive coil are used, the movement of the optical pickup is not restricted by the extra magnets. Therefore, the size of the optical pickup in the disk radial direction can be reduced, making it possible to effectively utilize the inner circumference of the disk, and also simplifying the structure.

[Brief explanation of drawings]

FIG. 1 is a sectional front view of a conventional optical pickup device, FIG. 2 is a sectional front view of an optical pickup device according to an embodiment of the present invention, and FIG. 3 is a plan view of the same device. 13...Objective lens, 14...Lens barrel, 1
5...Focus drive coil, 16a, 16b...
...Tracking drive coil, 17... Housing, 21
a, 21b... magnet unit, 18a, 18b...
...Elastic member.

Claims (1)

[Scope of Claims] 1. A lens barrel housing an objective lens, and a first coil for focusing control wound around the outer periphery of the lens barrel so that its coil axis coincides with the optical axis of the objective lens. , fixed to the outer periphery of the lens barrel at a slight distance from the first coil so that the coil axis coincides with the radial direction of the recording track formed on the disk-shaped recording medium; a second coil for tracking control configured such that the center of the coil at the position where the coil is wound around the lens barrel in the optical axis direction and the center of the coil at the fixed position in the optical axis direction substantially coincide; 1. An optical pickup device comprising: a magnet having a magnetic pole in the tangential direction of a recording track and arranged so that the same magnetic pole faces the winding surfaces of the first coil and the second coil.