JPH0536105A - Optical head - Google Patents

Abstract

PURPOSE:To provide the small-sized optical head which reads the information of a recording medium. CONSTITUTION:An objective lens support 2 fixed with an objective lens 1 for reading the information of the recording medium recorded with the information in the form of tracks is formed with a frame-shaped aperture in the direction perpendicular to the medium surface of the recording medium. A focusing coil 15, tracking coils 16, 17 and a magnetic field generating means 19 are disposed in this frame-shaped aperture to reduce the size of the optical head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for reproducing information recorded on an optical recording disc or recording information on such a disc.

[0002]

2. Description of the Related Art Conventionally, a support mechanism for movably supporting an objective lens for irradiating a light spot on a recording medium in a focusing direction parallel to the optical axis and a tracking direction orthogonal to the focusing direction, and an objective lens. An optical head having a driving mechanism for driving in the focusing direction and the tracking direction is known, and is described in, for example, Japanese Patent Laid-Open No. 59-104733. In this known optical head, a focusing leaf spring and a tracking leaf spring extending in the focusing direction and the direction orthogonal to the tracking are provided between a support member that supports the objective lens and the base, and one end of the focusing leaf spring is provided. Is fixed to the objective lens support member and the other end is fixed to the relay member, and one end of the tracking leaf spring is fixed to the relay member and the other end is fixed to the base to support the objective lens so that it can move in the focusing direction and the tracking direction. is doing. Then, tracking coils are provided on both sides of the objective lens support member in the tracking direction, a bobbin is attached to the lower side of the objective lens in the optical axis direction, a focusing coil is attached to this bobbin, and a driving current is supplied to the focusing coil and the tracking coil. Focusing control and tracking control are performed.

[0003]

However, in this known optical head, a focusing coil is attached to the lower side of the objective lens in the optical axis direction, and a magnet is attached to surround the focusing coil to supply a magnetic flux to the focusing coil. With this configuration, a focusing coil extending in the optical axis direction is mounted on the lower side of the objective lens in the optical axis direction, and there is a drawback that the optical head becomes large in the optical axis direction of the objective lens.

An object of the present invention is to provide a compact and high-performance optical head which eliminates the above-mentioned drawbacks.

[0005]

In order to achieve the above object, the optical head of the present invention has a lens which is perpendicular to the surface of the recording medium in order to read information on the recording medium on which information is recorded in a track form. 1. An optical head adapted to be driven in one direction and in a second direction which is parallel to the surface and traverses an information track, in which a frame-shaped opening along the first direction is formed in a support body to which the lens is fixed. And a focusing coil, a tracking coil and a magnetic field generating means are arranged in the frame-shaped opening.

[0006]

The focusing lens, the tracking coil, and the magnetic field generating means are arranged in the frame-shaped opening formed in the lens support, so that the lens moves in the first direction and the second direction.
Since the optical head is driven in this direction, the optical head becomes compact.

[0007]

1 to 3 show the construction of an example of an optical head according to the present invention. FIG. 1 is an exploded perspective view, FIG. 2 is a plan view showing a part of a section, and FIG. 3 is a section view. is there. Objective lens 1 for irradiating a light spot on a recording medium such as an optical disc
Is mounted on the objective lens support member 2. This support member 2
Is made by lightweight integral molding, and the objective lens 1, the substrate 3 on which the focusing coil and the tracking coil are mounted, and the balancer 4 are mounted.

The support member 2 is displaced in the focusing direction F parallel to the optical axis of the objective lens 1 to focus the light spot on the recording medium, and in the tracking direction T orthogonal to the information track on the recording medium and the optical axis. The objective lens support member 2 is connected to the base 5 via a support mechanism in order to displace it so that the light spot follows the information track. In this example, this support mechanism is composed of a pair of focusing leaf springs 6 and 7, a relay member 8, and a pair of tracking leaf springs 9 and 10.

A pair of focusing leaf springs 6 and 7
Has a "U" shape composed of two legs 6a and 7a and bridges 6b and 7b, respectively, and the legs 6a and 7a face each other in parallel with each other when viewed in the focusing direction. Is the focusing direction F and the tracking direction T
The respective end portions of the leg portions 6a and 7a are fixed to the supporting member 2 by the four holding plates 11a to 11d so as to extend in the direction orthogonal to the holding member 12a and the bridge portions 6b and 7b. And 12
It is fixed to the relay member 8 by b. In addition, the pair of flat plate-shaped tracking leaf springs 9 and 10 are
Mounted on the left and right grooves 8a and 8b formed in the relay member 8 so that one ends thereof extend in a direction substantially orthogonal to the focusing direction F and the tracking direction T while facing each other at an angle α shown in FIG. And the groove 13 formed in the posts 13 and 14 with the other end integrally formed with the base 5.
a and 14a.

In this way, the objective lens 1 has the relay member 8
Focusing direction F and tracking direction T via
Movably supported by.

Next, the objective lens 1 is moved in the focusing direction F.
A drive mechanism for driving in the tracking direction T will be described.

The focusing coil is composed of one flat coil 15 having a "square" shape, and the tracking coil is also composed of two flat coils 16 and 17 having a "square" shape. Is mounted on one surface of the substrate 3, and two tracking coils 16 and 17 are arranged in the tracking direction and mounted on the other surface of the substrate 3.
Then, the substrate 3 on which each coil is mounted is formed with the groove 2 formed between the objective lens 1 of the objective lens support member 2 and the relay member 8.
The focusing coil 15 and the tracking coils 16 and 17 are mounted between a and 2b so as to be parallel to the focusing direction F and the tracking direction T, respectively. A magnetic field generating member that generates a magnetic field that cooperates with the focusing coil 15 and the tracking units 16 and 17 is composed of a yoke 18 made of a magnetic material and a permanent magnet 19. The yoke 18 includes two leg portions 18a and 18b which are parallel to each other in the focusing direction F and the tracking direction T and face each other. A permanent magnet 19 is fixed to one leg portion 18a to fix the yoke 18 to the base 5. Further, one coil portion 15a of the coil portions parallel to the tracking direction T of the focusing coil 15 is provided.
Is placed in a plane where the permanent magnet 19 and the leg portion 18b of the yoke 18 face each other, and only one of the coil portions 16a and 17a of the coil portions parallel to the focusing direction T of each tracking coil 16 and 17 is made permanent. The magnet 19 and the leg portion 18b of the yoke 18 are located in the opposing surfaces. With this configuration, when a driving current is supplied to each coil, the coil portion 15a of the focusing coil 15 receives a force acting in the focusing direction F, and the tracking coils 16 and 17 are received.
Means that the coil portions 16a and 17a receive a force acting in the tracking direction T.

Now, when a focusing driving current having a amplitude and a polarity depending on the magnitude and direction of the focusing error is passed through the focusing coil 15, the focusing coil 15 and hence the objective lens support are supported by the interaction with the magnetic field passing through this coil. The member 2 and the objective lens 1 receive a force in the focusing direction F, and are displaced in the focusing direction by the bending of the pair of focusing leaf springs 6 and 7, so that the light beam can be focused as a minute light spot on the recording medium. .. In this case, since the objective lens 1 shifts in the focusing direction F with the relay member 8 as a fulcrum, if the focusing coil 15 is mounted between the objective lens 1 and the relay member 8, the shift amount of the focusing coil 15 can be reduced. Since it is substantially determined by the ratio of the distance from the relay member 8 to the objective lens 1 and the distance to the focusing coil 15, the deviation amount of the objective lens 1 can be increased even if the deviation amount of the focusing coil 15 is small. In this case, the relay member 8 also receives a force in the focusing direction via the focusing leaf springs 6 and 7, but since the main planes of the tracking leaf springs 9 and 10 are parallel to the focusing direction F, Is almost not deformed, so that the relay member 8 does not change in the focusing direction.

On the other hand, a pair of tracking coils 16 supplies a tracking drive current having an amplitude and a polarity according to the magnitude and direction of the deviation of the light spot with respect to the information track.
And 17, the tracking coils 16 and 17, and hence the support member 2 and the objective lens 1 receive a force in the tracking direction T due to the interaction with the magnetic field, and the objective lens 1 is tracked by the bending of the tracking leaf springs 9 and 10. It will be displaced in the direction T.

In this case, the relay member 8 receives a force in the tracking direction T, but since the main surfaces of the focusing leaf springs 6 and 7 extend in the tracking direction T, they are not displaced in this direction, so that they are not moved in the tracking direction. Will be accurately transmitted to the relay member 8, that is, the tracking leaf springs 9 and 10. Therefore, the objective lens is accurately driven in the tracking direction T according to the tracking drive current.

FIG. 4 is a sectional view showing the structures of the leaf springs 6 and 7 for focusing and the leaf springs 9 and 10 for tracking. In this example, the leaf spring is a viscoelastic sheet such as butyl rubber.
Elastic sheets 22 and 23 made of phosphor blue steel or the like are sandwiched between both sides of 21. The damping characteristic of such a leaf spring is extremely good for focusing and tracking drive, resonance in a desired frequency range can be effectively prevented, and accurate drive control can be performed. However, the leaf spring is not limited to such a leaf spring, and may be composed of, for example, one phosphor bronze plate, or a viscoelastic sheet attached to at least one surface of this plate. You can also

As shown in FIG. 3, the objective lens 1 and the supporting member 2 for supporting the objective lens 1 have small dimensions in the optical axis direction.
A prism 20 is arranged below this to reflect the light from the light source toward the objective lens 1 or to reflect the light flux reflected by the recording medium and passing through the objective lens 1 toward the light receiver. With such a configuration, the size of the entire optical head when viewed in the optical axis direction of the objective lens 1 can be significantly reduced, which is extremely advantageous in terms of downsizing.

[0018]

As described above, according to the present invention, the support having the lens fixed thereto is provided with a frame-shaped opening along the first direction perpendicular to the surface of the recording medium. Since the focusing coil, the tracking coil and the magnetic field generating means are arranged, the optical head becomes extremely small.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is a sectional view of the first embodiment.

FIG. 4 is a cross-sectional view showing a configuration of a leaf spring.

[Explanation of symbols]

 1 objective lens 2 support member for objective lens 5 base 15 focusing coil 16,17 tracking coil 18 yoke 19 permanent magnet 20 prism 21 viscoelastic sheet 22,23 elastic sheet

Front page continued (72) Inventor Kazumasa Ishikawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Yoichi Sugimoto 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optics Industrial Co., Ltd. (72) Inventor Shohei Kobayashi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Toru Musha 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optics Industry Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. In order to read information on a recording medium on which information is recorded in a track shape, a lens is provided with a lens parallel to a first direction perpendicular to the surface of the recording medium and the information track. In an optical head configured to be driven in a second direction traversing the optical axis, a frame-shaped opening along the first direction is provided in a support body to which the lens is fixed, and focusing is performed in the frame-shaped opening. An optical head in which a coil, a tracking coil and a magnetic field generating means are arranged.