JPH0481813B2 - - Google Patents

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.

2. Description of the Related Art An objective lens drive device moves an objective lens in a direction perpendicular to the surface of the recording medium in order to correct focus deviation caused by vertical movement of a warped disk-shaped recording medium such as a compact disk, and tracking deviation caused by eccentricity. Optical axis direction (hereinafter referred to as focus direction F)
) and the radial direction parallel to the surface of the recording medium (hereinafter referred to as the tracking direction T)
It is driven by two axes.

A conventional objective lens driving device of this type has a structure as shown in FIG.

That is, when driving in the focus direction F, the lens holder 22 to which the objective lens 21 is attached is driven by the magnet 26.
An electrodynamic transducer in which a focus coil 29 is placed in the gap of a magnetic circuit consisting of magnetic yokes 27a and 27b and leaf springs 25a and 27b
It is obtained by translational movement via 5b, 25c, and 25d.

The driving in the tracking direction T is performed by the objective lens 21.
The lens holder 22 with attached magnets 26a, 26
Tracking coils 28a, 28b are placed in the gap of the magnetic circuit consisting of magnetic yokes 27a, 27c and magnetic yokes 27a, 27c.
It is obtained by rotating around the shaft 24 by an electrodynamic transducer arranged with a .

In addition, the entire objective lens drive device is access-driven by a motor in the access direction Ad (same direction as the tracking direction T) on the recording medium.

Problems to be solved by the invention However, with the structure shown in Figure 3,
When the entire objective lens driving device is access-driven by a motor, by aligning the center of gravity of all movable parts with the center of the shaft 24 so as to prevent unnecessary vibration from occurring in the objective lens 21, an external force acting on all movable parts is generated. is always received by shaft 24, but the center of gravity of all movable parts and shaft 2
4, the second movable part 2
3 is large, making it difficult to reduce the size and weight required for the objective lens drive device in order to shorten access time and improve sensitivity, and also use a cartridge to protect the recording medium. In this case, there was a problem in that the entire objective lens driving device could not be placed inside the cartridge window.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an objective lens driving device that can be made smaller and lighter.

Means for Solving the Problems In order to achieve the above object, the present invention integrates the second movable part magnetic circuit that drives the second movable part in the radial direction with the second movable part, and The center of gravity of the section is made to coincide with the center of the axis.

Effects The present invention can reduce the total length of the second movable portion and the magnetic circuit due to the upright configuration, so that the objective lens driving device can be made smaller and lighter.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1A is a plan view of an objective lens driving device according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along the line X--X in FIG. 1A.

In FIG. 1, a lens holder 2 holding a lens 1 is movable in a focus direction F by four leaf springs 5a, 5b, 5c, and 5d arranged on the upper, lower, left, and right sides of the lens holder 2. The first movable part consisting of the lens holder 2 and the leaf springs 5a, 5b,
a second movable part 3 connected by 5c and 5d;
A magnetic circuit consisting of a magnet 6c and a magnetic yoke 7c, which are integrated with the second movable portion 3, is configured to be rotatable in the tracking direction T about the shaft 4. Note that 9 is a focusing coil, and 10 is a tracking spring material.

Movement in the tracking direction T is achieved by an electrodynamic transducer in which a tracking coil 8a attached to the lens holder 2 is arranged in the gap of a magnetic circuit consisting of a magnet 6a and a magnetic yoke 7a, and a second movable part 3.
Rotational motion about the axis 4 is achieved by an electrodynamic transducer in which a tracking coil 8b fixed to the base 11 is arranged in the gap of a magnetic circuit consisting of a magnet 6c and a magnetic yoke 7c integrated with the becomes.

At this time, when the entire objective lens drive device is access-driven by a motor, as in the conventional objective lens drive device shown in FIG. The objective lens driving device is of a type in which the center of the magnet 26c is aligned with the center of the magnet 26c, which drives the second movable part 23 in the tracking direction T as shown in FIG. 2B.
The magnetic circuit consisting of the magnetic yoke 27c is shown in Fig. 2A.
By integrating the magnetic circuit with the second movable part 3, such as the magnetic circuit consisting of the magnet 6c and the magnetic yoke 7c shown in FIG. Therefore, the dimensions of the second movable part 3 can be made smaller than the second movable part 23 of the conventional objective lens drive device shown in FIG. 2B, making the entire objective lens drive device small and lightweight. can be converted into

Further, as shown in FIG. 2, when the recording medium 40 is stored in a cartridge 41 to protect it, if the objective lens driving device is larger than the window of the cartridge, the recording medium 40 is stored in a cartridge 41 as shown in FIG. 2B. In the conventional objective lens driving device, in order to ensure the working distance between the recording medium 40 and the objective lens 21, the objective lens 21 must be brought close to the recording medium 40. Therefore, it is necessary to install a balance weight 32 to prevent extra vibrations from occurring in the objective lens 21 due to external impact force. There was a drawback that the second movable part 23 became heavier due to the weight 32.

In the objective lens drive device of this embodiment as shown in FIG. By making the dimension (total height) smaller than the dimension in the focus direction F of the second movable section 3, a part of the movable section can be placed inside the window of the cartridge 41, and the recording medium 4
In order to secure the working distance between 0 and objective lens 1, no balance weight is required, which reduces the weight of the moving parts compared to conventional objective lens drive devices, and at the same time reduces the sensitivity. Improvements can be achieved.

Effects of the Invention The present invention allows a second movable part that is rotatable only in the tracking direction about an axis and a first movable part consisting of an objective lens and a lens holder to rotate only in the focusing direction. This objective lens drive device is connected by a plurality of parallel leaf springs so that it can move, and the center of gravity of all movable parts is aligned with the axis center. By integrating the magnetic circuit consisting of the magnetic yoke with the second movable part, the entire objective lens driving device can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1A is a plan view of an objective lens driving device according to an embodiment of the present invention, FIG. 1B is a sectional view taken along the line X-X of FIG. 1A, and FIG. 2A is an objective lens according to an embodiment of the present invention. FIG. 2B is a cross-sectional view of the main parts of a conventional objective lens driving device, FIG. 3A is a plan view of the conventional objective lens driving device, and FIG. 3B is a cross-sectional view of the conventional objective lens driving device. It is a sectional view taken along YY line. DESCRIPTION OF SYMBOLS 1... Lens, 2... Lens holder, 3... Second movable part, 4... Shaft, 5a-5d... Leaf spring,
6a-6c...Magnet, 7a-7c...Magnetic yoke, 8a, 8b...Tracking coil, 9...
...Focusing coil, 10...Tracking spring material, 11...Base.

Claims (1)

[Claims] 1. An objective lens of a device for optically writing or reading information on a recording medium, an optical axis direction in a radial direction parallel to the surface of the recording medium and in a direction perpendicular to the surface of the recording medium. It has a mechanism that drives the
A first movable part consisting of the objective lens and a lens holder for holding it, and a second movable part that can rotate only in the radial direction about an axis, and only the first movable part moves in the optical axis direction. one or more optical axis direction magnetic circuits movably connected by a plurality of parallel plate springs and driving the first movable part in the optical axis direction; and the first and second magnetic circuits. one or more of the radial magnetic circuits for driving the movable part in the radial direction, and for returning to the original position when the first and second movable parts move in the radial direction. the second movable part magnetic circuit for driving the second movable part in the radial direction of the radial direction magnetic circuit is integrated with the second movable part; An objective lens driving device characterized in that the center of gravity of all movable parts including the first movable part, the second movable part, the leaf spring, and the magnetic circuit for the second movable part is aligned with the axial center. . 2. The objective lens according to claim 1, wherein the dimension of the second movable part magnetic circuit in the optical axis direction is smaller than the dimension of the second movable part in the optical axis direction. Drive device. 3. The objective lens driving device according to claim 1, wherein a magnet is disposed inside a U-shaped magnetic yoke as the second movable part magnetic circuit. 4. The objective lens driving device according to claim 1, wherein a magnet is disposed inside a square-shaped magnetic yoke as the second movable part magnetic circuit.