JPH10302280A - Actuator for optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator for optical head in which the focal point of an objective lens is prevented from being shifted through tracking control. SOLUTION: The shaft sliding type actuator can move an objective lens, respectively, in the axial direction of a shaft 2 and the circumferential direction of a circle having the center on the axis with the shaft 2 having the axis extending in the focusing direction of an objective lens 3 as a guide. The actuator is provided, on the movable part side thereof, with a magnet 5 magnetized in the radial direction of the circle. In this regard, an arcuate yoke 10 having the center on the axis is disposed on the fixed part side 1 thereof between the magnet 5 and the shaft 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an actuator for driving an objective lens of an optical head used for recording and reproducing information on and from a recording medium such as an optical disk and a magneto-optical disk.

[0002]

2. Description of the Related Art As a conventional optical head actuator, for example, an actuator shown in an exploded perspective view in FIG. 5 and a front view in FIG. 6 has been proposed. This actuator is
A so-called shaft-sliding type of moving magnet system, in which a spindle 2 fixed to a support base 1 has a lens holder 4 for holding an objective lens 3, and the optical axis of the objective lens 3 is aligned with the axis of the spindle 2. The lens holder 4 is supported rotatably and slidably in the axial direction via a bearing portion 4a so as to be parallel to the lens holder 4a. A magnet 5 magnetized in the radial direction is attached. A magnetic yoke 8 around which a focusing coil 6 and a tracking coil 7 are wound is provided on the support 1 side so as to be located outside the magnet 5. In FIG. 6, illustration of the focusing coil 6 and the tracking coil 7 is omitted.

[0003] Here, the focusing coil 6 is wound around an axis parallel to the support shaft 2 of the magnetic yoke 8 such that an electromagnetic force acts on the magnet 5 in the axial direction of the support shaft 2 when energized. Turned, tracking coil 7
Is wound around the tangential direction such that an electromagnetic force acts on the magnet 5 in the tangential direction of the circumference of the support shaft 2 when energized. The magnetic yoke 8 converges the magnetic flux so that the magnetic flux from the magnet 5 crosses the focusing coil 6 and the tracking coil 7 effectively, and floats the lens holder 4 by the magnetic attraction with the magnet 5. Thus, the objective lens 3 acts so as to be maintained at the reference position roughly positioned in the focusing direction and the tracking direction. In FIG. 5 and FIG. 6, the magnet 5, the focusing coil 6, the tracking coil 7, and the magnetic yoke 8 are each one.
In some cases, two magnets are provided at the axially symmetric positions of the support shaft 2, and a focusing coil and a tracking coil are provided around the magnetic yoke on the support 1 side corresponding to each magnet.

[0004]

However, in the conventional actuator described above, when the lens holder 4 is rotated by tracking control to displace the objective lens 3 from the reference position, the magnet 5 and the magnetic A change occurs in the magnetic attraction force with the yoke 8, which causes a problem that the floating height of the lens holder 4 changes and the focal position of the objective lens 3 shifts, making it impossible to accurately record or reproduce information.

An object of the present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an actuator for an optical head which is appropriately configured so that the tracking control does not cause a defocus of an objective lens. Things.

[0006]

In order to achieve the above-mentioned object, the present invention is directed to a supporting shaft having an axis extending in a focusing direction of an objective lens as a guide. In a shaft sliding type optical head actuator having a magnet magnetized in the radial direction of the circle on the movable portion side, the magnet and the support are movable. An arc-shaped yoke centered on the axis is provided on the fixed portion side between the shaft and the shaft.

[0007]

1 and 2 are an exploded perspective view and a front view, respectively, showing the structure of a main part of an embodiment of the present invention. In this embodiment, for example, a lens holder 4 holding an objective lens 3 is supported on a support shaft 2 fixed to a support base 1 such that the optical axis of the objective lens 3 is parallel to the axis of the support shaft 2. It is rotatably supported via the portion 4a and is slidably supported in the axial direction. Also, the lens holder 4
Is provided with a magnet 5 magnetized in the radial direction on a circumference around the support shaft 2. Although not shown,
On the support 1 side, a focusing coil and a tracking coil are wound around a magnetic yoke and arranged as necessary in the same manner as in the conventional example so as to be positioned outside the magnet 5, for example. Although one magnet 5 is shown in FIGS. 1 and 2, for example, two magnets are provided at an axially symmetric position of the support shaft 2 of the lens holder 4, and the magnet is provided on the support base 1 side corresponding to each magnet. The focusing coil and the tracking coil can be wound around a magnetic yoke as needed.

In this embodiment, the support shaft 2 and the magnet 5
3, the center of the axis of the support shaft 2 as shown in the enlarged perspective view in FIG. 3 so as to face the magnet 5 over the movable range of the magnet 5 by the tracking control of the objective lens 3, An arc-shaped yoke 10 cut in a plane parallel to the axis is fixedly provided on the support 1. Here, the arc-shaped yoke 10 strongly attracts the magnet 5 at three height positions of the upper end, the center, and the lower end in the axial direction. Adjusting the length appropriately and restricting the vertical movement of the lens holder 4 so that the suction force at the upper end of the arc-shaped yoke 10 becomes dominant, etc., from one of the three positions Is configured to select the suction force.

With this structure, even if the lens holder 4 is rotated and displaced from the reference position by the tracking control, the magnetic attraction between the magnet 5 and the arc-shaped yoke 10 may change. Absent. Therefore, since the floating height of the lens holder 4 does not change, the objective lens 3
It is possible to accurately record or reproduce information without causing any defocus. Also, an arc-shaped yoke 1
In the case of 0, a magnetic pole is easily generated on the end face parallel to the axis of the support shaft 2, and the magnet 5 is easily drawn near the end face position. Therefore, a stable tracking reference position of the lens holder 4 can be easily obtained. When a plurality of magnets are provided in the lens holder 4, an arc-shaped yoke may be provided so as to correspond to one or more arbitrary magnets over the movable range thereof.

FIG. 4 is a perspective view showing a modification of the arc-shaped yoke in this embodiment. The arc-shaped yoke 10 has a thick portion 10a formed at an upper end portion thereof, the thickness of which is increased in the radial direction of the axis. With such a configuration, in the thick portion 10a at the upper end, the attractive force with the magnet 5 can be further increased, so that the floating height of the lens holder 4 can be more stably maintained and more stable. The obtained tracking reference position can be easily obtained.

[0011]

According to the present invention, in the shaft-sliding type moving magnet type optical head actuator, the arc-shaped yoke is provided on the fixed portion side between the magnet and the support shaft, so that tracking control is performed. Therefore, even if the lens holder is rotated and displaced from the reference position, the magnetic attraction between the magnet and the arc-shaped yoke does not change. Therefore, since the floating height of the lens holder does not change, there is no defocus of the objective lens,
Information can be accurately recorded or reproduced.
Further, since the magnet can be drawn near the end face parallel to the axis of the arc-shaped yoke, a stable tracking reference position of the lens holder can be easily obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a front view showing a configuration of a main part of one embodiment of the present invention.

FIG. 3 is an enlarged perspective view of an arc-shaped yoke shown in FIG.

FIG. 4 is a perspective view showing a modified example of an arc-shaped yoke.

FIG. 5 is an exploded perspective view showing a configuration of a conventional optical head actuator.

FIG. 6 is a front view showing a configuration of a conventional optical head actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support stand 2 Support shaft 3 Objective lens 4 Lens holder 5 Magnet 10 Arc-shaped yoke

Claims (1)

[Claims] An object lens is movable in an axial direction of the support shaft and in a circumferential direction of a circle centered on the support shaft, using a support shaft having an axis extending in a focusing direction of the objective lens as a guide, In a shaft sliding type optical head actuator having a magnet magnetized in the radial direction of the circle on the movable portion side, an arc-shaped actuator centered on the axis is provided between the magnet and the support shaft. An actuator for an optical head, wherein a yoke is provided on a fixed portion side.