JPH0533464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses a laser or the like as a light source and focuses it on a desired position on a disk-shaped information recording medium (hereinafter referred to as a disk) to record information such as images and audio information. The present invention relates to a lens actuator for an optical recording and reproducing device that records or reproduces data.

2. Description of the Related Art A conventional lens actuator is disclosed in Japanese Utility Model Application Publication No. 168844/1983, for example. FIG. 7 shows a cross-sectional view of this conventional lens actuator, in which 1 is a semiconductor laser, 2 is a laser beam, 3 is a reflecting mirror, 4 is an objective lens, 5 is a disk, and 6 is a lens barrel. , 7, 7' are tracking drive coils that drive the lens barrel 6 in its radial direction;
8 and 8' are tracking drive magnetic circuits; 9 is a focusing drive coil that drives the lens barrel 6 in its axial direction; 10 is a focusing drive magnetic circuit;
1 and 12 indicate elastic support members. In this conventional optical pickup, when a tracking correction current is applied from a tracking error detection circuit (not shown) to the tracking drive coils 7, 7', an electromagnetic force is generated between the tracking drive magnetic circuits 8, 8'. The objective lens 4 moves in the XX direction (radial direction of the lens barrel 6) in the figure until the elastic force of the elastic support members 11 and 12 is balanced, and tracking control is performed. Similarly, focusing control is performed by moving the objective lens 4 to Z by electromagnetic force between the focusing drive coil 9 and the focusing drive magnetic circuit 10.
This is done by moving in the direction.

Problems to be Solved by the Invention However, in the above configuration, since the tracking and focusing coils and magnetic circuits are separated and arranged independently, it is difficult to downsize the focusing control direction, that is, to reduce the size of the lens actuator. It is difficult to reduce the height.

Also, gaps are provided in the focusing control direction between the tracking drive coils 7, 7' and the tracking drive magnetic circuits 8, 8', and between the focusing drive coil 9 and the focusing drive magnetic circuit 10, respectively, by the movable range during focusing movement. Therefore, there was a problem in that the height of the lens actuator could not be lowered.

An object of the present invention is to solve the problems of the prior art described above and provide a thinner lens actuator.

Means for Solving the Problems The present invention includes a lens barrel having an objective lens, a pair of coils fitted into the lens barrel and located coaxially with the focus adjustment direction, and a magnetic flux linking these coils. This is a lens actuator equipped with a fixed magnet that generates an image.

Effects According to the present invention, the tracking drive and focusing drive coils can be configured by a pair of coils that are flat in the focusing control direction. In addition, since the magnetic circuit can also be used for both focusing drive and tracking drive, there is no need to provide separate gaps during focusing movement.
The lens actuator can be made thinner.

Embodiment FIG. 1 is a plan view of a lens actuator in a first embodiment of the present invention, and FIG. 2 is a sectional view thereof.

4 is an objective lens, 5 is a disk, 6 is a lens barrel, and 13a and 13b are elastic support members that hold the lens barrel 6 movably in the focusing control direction ZZ and the tracking control direction XX, and are shown in FIG. In this way, the vicinity of the vertical center of the lens barrel 6 is elastically supported. Also 14a, 14b
is arranged so that its axial direction is in the ZZ direction, and so that it is approximately symmetrical with respect to the elastic support members 13a and 13b as shown in FIG. 2, and its center is located on the central axis of the lens barrel 6. The elastic support member 13
A pair of flat coils a and 13b are fitted near the attachment position to the lens barrel 6. Also, 15a is a magnet having a U-shaped cross section and magnetized in the radial direction thereof. In this example, all inner surfaces are N.
It is magnetized to form a pole.

15b is a magnet that has a U-shaped cross section like the magnet 15a and is magnetized in the radial direction, but in this embodiment, the two opposing inner surfaces of the U-shape are S poles, and the remaining inner surfaces are N poles. It is polarized. Further, as shown in FIG. 2, the magnetic poles of the magnets 15a and 15b are arranged to coincide with the focus control direction ZZ and the tracking control direction XX, respectively.

16 is a base for the entire lens actuator, and magnets 15a, 15b and an elastic support member 13
One ends of a and 13b are fixed.

The operation of the lens actuator of this embodiment configured as described above will be explained below with reference to FIGS. 3 and 4.

Coils 14a, 14b in the direction shown in FIG.
When driving currents I _a and I _b are applied to the coils 14
Due to the electromagnetic action between a and the magnet 15a, the
A focusing control force indicated by F _a1 and a tracking control force indicated by T _a1 are generated. With this F _a1
The resultant force of T _a1 is indicated by A1. Similarly, the focusing control force generated between the coil 14a and the magnet 15b is indicated by F _a2 , the tracking control force by T _a2 , and the resultant force by A2.

In addition, F _b1 is the focusing control force generated between the coil 14b and the magnet 15a, T _b1 is the tracking control force and B1 is the resultant force, F b2 is the focusing control force generated between the coil 14b and the magnet 15b, and F _b2 is the tracking control force generated between the coil 14b and the magnet 15b. The control force is T _b2 and the resultant force is B
It is shown as 2.

In this embodiment, the flat coils 14a, 14
b so that its axis direction is the ZZ direction, and the second
As shown in the figure, elastic support members 13a, 13b
It is fitted near the vertical center of the lens barrel 6 so that it is substantially symmetrical with respect to the lens barrel 6 and its center is located on the central axis of the lens barrel 6 . Therefore, the third
Focusing control forces F _a1 , F _a2 and F _b1 in the figure,
The direction in which F _b2 acts coincides with the ZZ axis direction, and acts near the center of the lens barrel 6. Also,
The direction in which the tracking control forces T _a1 , T _a2 and F _b1 , F _b2 act coincides with the XX direction and is applied to the elastic support members 13 a, 13 near the center of the lens barrel 6.
It acts at a position that is approximately symmetrical to b. the result,
The points of action of the resultant forces A ₁ , A ₂ , B ₁ , and B ₂ are all located near the center of the lens barrel 6.

Therefore, the control force generated by the current I _a and the control force generated by the current I _b are respectively A in FIG.
and B. Also, A and B's ZZ
and the XX direction component force, that is, the focusing control force and the tracking control force, are respectively F _A , F _B , T _A ,
It is represented by T _B. In addition, these focusing control forces and tracking control forces F _A , F _B , T _A ,
Each of T _B has its point of action near the center of the lens barrel 6.

Figure 4 shows the coil 14a and magnet 1 due to the current I _a .
5a, 15b and the current
_Ib indicates the resultant force A+B of the control force B generated between the coil 14b and the magnets 15a, 15b. The component force F A+B in the ZZ direction of this resultant force _A+B is the focusing control force of the entire lens actuator.
F _A+B , and the component force in the XX direction becomes the tracking control force T _A+B .

That is, by controlling the magnitude and magnetism of currents I _a and I _b , desired focusing control force F _A+B and tracking control force T _A+B can be obtained.

Therefore, with the elastic support members 13a and 13b, ZZ
The objective lens 4 supported movably in the and XX directions is driven by focusing control force F _A+B and tracking control force T _A+B obtained by controlling the magnitude and polarity of currents I _a and I _b . This allows focusing control and tracking control to be performed.

As described above, according to this embodiment, the pair of coils 14a and 14b flat in the Z direction and the magnetic circuit 15
Both focusing control and tracking control can be performed by a and 15b.

Therefore, unlike the conventional example, there is no need to provide separate coils and magnetic circuits for focusing control and tracking control, and a gap is created between the tracking drive coil magnetic circuits in the focusing control direction by the movable range during focusing movement. It is no longer necessary to provide the focusing drive coil and the magnetic circuit independently, and the lens actuator can be made thinner.

Further, although the material of the magnets 15a and 15b is arbitrary, by using plastic magnets, a radially magnetized hollow rectangular cross-section magnet can be constructed at low cost.

A second embodiment of the present invention will be described using FIG. 5. The same numbers in the figures are in Figures 1 and 2.
Shows the same thing as the figure. 15c, 15d, 15
e and 15f are fixed magnets each having an L-shaped cross section and magnetized in the radial direction. The lens actuator configured in this manner can also perform the same operation as the first embodiment, and can be made thinner as well. Furthermore, this embodiment has the advantage that the fixed magnet can be made smaller and lighter.

Note that the polarity of the magnetic poles of the magnets shown in the first embodiment and the second embodiment is not limited to that of the sixth embodiment.
The same effect can be obtained by arranging the magnetic poles as shown in the figure.

Effects of the Invention As described above, according to the present invention, a pair of coils fitted into a lens barrel having an objective lens and located coaxially with the focus adjustment direction, and a magnetic flux interlinked with the pair of coils are provided. Due to the fixed magnet generated,
By performing focusing control and tracking control, the lens actuator can be made thinner. As a result, the entire optical recording/reproducing device can be made thinner, which has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a lens actuator according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the lens actuator, FIG.
5 is a sectional view of a lens actuator according to another embodiment of the present invention, and FIG.
The figure is a sectional view of a lens actuator according to still another embodiment of the present invention, and FIG. 7 is a sectional view of a conventional lens actuator. 4...Objective lens, 6... Lens barrel, 14a, 14
b... Drive coil, 15a, 15b... Magnet.

Claims (1)

[Scope of Claims] 1. A lens barrel having an objective lens, and a holding means that is fixed near the center of the lens barrel in the vertical direction and holds the lens barrel movably in a focus control direction and a tracking control direction. and a pair of coils fixed to the lens barrel at positions substantially symmetrical to the fixing point of the holding means so as to be coaxial with the focus control direction, and magnetic poles of the same polarity face each other on the outer peripheral surface and upper and lower end surfaces of the coils. and a second fixed magnet arranged so that the polarity of the magnetic pole facing the outer peripheral surface of the coil and the magnetic pole facing the upper and lower end surfaces of the coil are different from each other. lens actuator. 2. The lens actuator according to claim 1, wherein the first and second fixed magnets are plastic magnets.