JPS61142537A - Lens actuator - Google Patents

Abstract

PURPOSE:To thin a lens actuator by executing both focusing control and tracking control by a pair of coils engaged with a body tube having an objective lens and positioned coaxially with a focus adjusting direction and fixed magnets crossing these coils and generating magnetic flux. CONSTITUTION:When driving currents Ia, Ib are supplied to the coils 14a, 14b, focusing control force Fa1 and tracking control force Ta1 are generated by the electromagnetic action between the coil 14a and the magnet 15a and resultant force A1 is formed. Similarly, the focusing control force and tracking control force are generated between the coil 14a and the magnet 15b, between the coil 14a and the magnet 15a and between the coil 14b and the magnet 15b, so that control forces A, B are generated by the currents Ia, Ib. The component force FA+B of the resultant force A+B in the ZZ direction acts as the focusing control force FA+B of the whole actuator and the component force in the XX direction acts as the tracking control force TA+B. Namely, the required focusing control force FA+B and tracking control force TA+B can be obtained by controlling the capacity and polarity of the currents Ia, Ib.

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/reproducing device that records or reproduces data.

Conventional technology As a conventional lens actuator, for example,
There is one shown in Japanese Patent No.-168844.

FIG. 7 shows a cross-sectional view of this conventional lens actuator, in which 1 is a semiconductor laser, 2 is a laser source, and 3 is a sectional view of a conventional lens actuator.
4 is a reflecting mirror, 4 is an objective lens, 6 is a disk, 6 is a lens barrel, 7.7' is a tracking drive coil that drives the lens barrel 6 in its radial direction, 8.8' is a tracking drive magnetic circuit, 9 Reference numeral 10 indicates a focusing drive coil that drives the lens barrel 6 in its axial direction, 10 a focusing drive magnetic circuit, and 11 and 12 elastic support members. In this conventional original pickup, when a tracking correction current is applied to the tracking drive coil 7, 7' from a tracking error detection circuit (not shown), the tracking drive magnetic circuit 8, 8
An electromagnetic force is generated between the objective lens 4 and
tracking control is performed by moving in the direction (radial direction of the lens barrel 6). The mK focusing control consists of a focusing drive filter 9 and a focusing drive magnetic circuit 1.
This is done by moving the objective lens 4 in two directions using an electromagnetic force between zero and zero.

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

In addition, there are gaps in the focusing control direction between the tracking drive coils 7 and 7' and the tracking drive magnetic circuits 8 and 8', and between the focusing drive coil 9 and the focusing drive magnetic circuit 1o, each corresponding to 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 above-mentioned conventional example and provide a thinner lens actuator.

Means for Solving the Problems The present invention comprises 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.

Operation According to the present invention, the tracking drive and focusing drive coils can be configured as a pair of coils that are flat in the seven focusing control directions. Further, since the magnetic circuit can also be used for both focusing drive and tracking drive, there is no need to independently provide a gap during focusing movement, so it is possible to make the lens actuator 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, 6 is a disk, 6 is a lens barrel, 13
a and 13b move the lens barrel 6 in the focusing control direction Z
Z,) Elastic support members 14a and 14b are held movably in the rough king control direction xx, and 14a and 14b are a pair of flat coils fitted onto the lens barrel 6 so that the axial direction thereof is in the Zz force direction; It is a magnet that has a U-shaped cross section and is magnetized in its radial direction. In this embodiment, all the inner surfaces are magnetized to become N poles.

16b 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. Also, as shown in Figure 2, the magnet 1
The magnetic poles sa and 1sb are arranged to coincide with the focus control direction ZZ and the tracking control direction xx, respectively.

16 is the base of the entire lens actuator, and the magnet 1
5a, 15b and the elastic support member 13a.

One end of 13b is fixed.

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

When driving currents I, Ib are applied to the coils 14a and 14b in the direction shown in FIG. 3, the coil 14a and the magnet 1
5a generates a focusing control force indicated by Fal and a tracking control force indicated by Ta1 in the figure. The resultant force of Fal and Ta1 is indicated by A1. Similarly, the focusing control force generated between the coil 14a and the magnet 15b is indicated by F, the tracking control force is indicated by "B2," and the resultant force is indicated by A2.

Further, the focusing control force generated between the coil 14b and the magnet 15a is Fbl, and the tracking control force is Tb.
1 and the resultant force are represented by B1, the focusing control force generated between the coil 14b and the magnet 16b is represented by F, the tracking control force is represented by Tb2, and the resultant force is represented by B22S.

Therefore, the control force generated by the electric current and the control force generated by the electric current can be represented by A and B in FIG. 3, respectively. In addition, the zZ and xx direction component forces of A and B, that is, the focusing control force and the tracking control force, are respectively FA and FB.

It is represented by TA and TB.

FIG. 4 shows a coil 14a and a magnet 15a, made by an electrician.
1sb and the control force B generated between the coil 14b, the magnet 15a, and 1sb due to current. Z of this resultant force A+B
The component force FA+B in the Z direction becomes the focusing control force FA+B of the entire lens actuator, and the component force in the xx direction becomes the tracking control force "A+B."

In other words, electric current! , and the desired focusing control force FA+B and tracking control force TA+B can be obtained by controlling the magnitude and polarity of the biases 22 and xx.
The objective lens 4, which is supported so as to be movable in the direction, is
Focusing control force FA+B and tracking control force TA obtained by controlling the magnitude and polarity of a and Ib
By driving with +B, focusing control and tracking control can be performed.

As described above, according to this embodiment, the pair of coils 14a and 14b and the magnetic circuit 16a are flat in the Z direction.

16b allows both focusing control and tracking control to be performed.

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

Further, although the material of the magnets 16a and 1sb is arbitrary, by using plastic magnets, a radially magnetized hollow rectangular cross-section magnet can be constructed at low cost. I will explain using The same numbers in the figures indicate the same ones as in FIGS. 1 and 2. 1s a * 1s d * 's'
+151 are fixed magnets each having an L-shaped cross section and magnetized in the radial direction. The lens actuator configured in this way can also perform the same operation as the first embodiment,
Moreover, it can also be made thinner.

Furthermore, this embodiment has the advantage that the fixed magnet can be made smaller and lighter.

Note that the present invention is not limited to the polarities of the magnetic poles of the magnets shown in the first and second embodiments, and the same effect can be obtained even if the magnetic poles are arranged as shown in FIG.

Effects of the Invention As explained 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 interlinking with the pair of coils are provided. By performing focusing control and tracking control using the generated fixed magnet, 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 same, Figs. FIG. 6 is a sectional view of a lens actuator according to another embodiment of the present invention, and FIG. 7 is a sectional view of a conventional lens actuator. 4... Objective lens, 6... Lens barrel, 14
a, 14k)... Drive coil, 15a, 15b
······magnet. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure - Figure 2 for Ni Figure 4 Figure 5''''7

Claims (3)

[Claims] (1) A lens barrel having an objective lens, a holding means that holds the lens barrel movably in the focus control direction and the tracking control direction, and a pair of lenses that fit into the lens barrel and are located coaxially with the focus adjustment direction. What is claimed is: 1. A lens actuator comprising: coils; and a fixed magnet that generates magnetic flux that interlinks with these coils. (2) The fixed magnet is a magnet magnetized in the radial direction, and is arranged so that its magnetic pole direction coincides with the focus control direction and the tracking control direction. lens actuator. (3) The lens actuator according to claim 2, wherein the fixed magnet is a plastic magnet.