JPH0555935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information detection head in an apparatus for optically reading and reproducing information recorded in a track shape on a recording medium.

Recording media on which information is recorded in the form of tracks are known, for example, as audio discs or video discs. On these recording media, the information tracks are usually arranged concentrically or spirally. A device for optically reading such information includes an optical system that projects a spot of light onto a recording medium, and means for detecting the relative position of the information track on the recording medium and the spot of light. For example, this method is described in Japanese Patent Application Laid-open No. 10005/1983.

FIG. 1 conceptually shows the known optical information reading device, in which 1 is a disk serving as a recording medium, which rotates around an axis 2-2'. The beam emitted from the laser light source 3 is transmitted through an auxiliary lens 4 and a reflecting mirror 5.
The light passes through the objective lens 6 and is focused onto the disk. The intensity of light transmitted or reflected from the disk changes depending on the information recorded on the disk, so by detecting the intensity of light with the photodetector 7, the information recorded on the disk can be electrically converted. It can be extracted as a physical output signal.

In this device, a light beam system is moved in the direction of arrow A at a constant speed with respect to the disk to roughly track the track. In order to read information correctly, the light from the laser light source 3 must be focused correctly onto the disk by the objective lens 6.
This focal point adjustment mechanism is performed by controlling the objective lens 6 using the output of the error signal detector 8.

Furthermore, the spot of light focused on the disk must be precisely positioned on the track. For this reason, the position of the light spot is controlled by rotating the reflecting mirror 5 around an axis perpendicular to the plane of the drawing.

In this device, it is necessary to accurately rotate the reflector with a small load, which makes the mechanism complicated and requires a large and high-performance objective lens, making it difficult to make the overall structure compact and lightweight. It was hot.

The width of the information track recorded on the disk is 1μ
m or less, and the track spacing is on the order of 1 μm, so
The control target for adjusting the focal point of the objective lens (hereinafter referred to as focusing) must be within ±1.0 μm, and the control target for causing the position of the light spot to follow a track (hereinafter referred to as tracking) must be within ±0.1 μm.

In order to solve this problem, a configuration may be considered in which the objective lens is driven in two-dimensional directions, that is, the focusing direction and the tracking direction.

FIG. 2 shows an information detection head that drives an objective lens in two-dimensional directions, that is, a focusing direction and a tracking direction.

The objective lens 101 includes an objective lens barrel 102,
It is attached to one end of an objective lens holder in which a disk-shaped coil support 103 and a cylindrical coil support are integrally attached and fixed.

A tightly wound spiral coil 103a is fixed to one side of the coil support 103 using an adhesive or the like. A part of the conducting wire of this coil 103a is placed in the magnetic gap of the permanent magnet 104a, and a control current for tracking is supplied through a lead wire (not shown). A cylindrical coil support at the other end of the objective lens barrel 102 has a coil 103c tightly wound around its outer periphery fixed to it with an adhesive or the like. This coil 103c is arranged in a magnetic gap of an annular permanent magnet 104c fixed to the base 110, and is supplied with a control current for focusing via a lead wire (not shown).
As described above, the objective lens and both coils for driving the same are fixed together to the objective lens holder formed integrally, one end of the conical spring 114 is fixed to the objective lens holder, and the other end is fixed to the objective lens holder. base 110
It is fixed at

In this embodiment, when the control current is supplied to the coil 103c, a force in the optical axis direction of the objective lens 101 is applied to the coil 103c by the magnetic field of the permanent magnet 104c, and the objective lens 101 is elastically supported by the conical spring 114. The lens holder, together with a coil fixed thereto, displaces the objective lens 101 in the direction of arrow C to perform focusing. In addition, the coil 103a
When a control current is supplied to the coil 103a, a force in the direction of the arrow A perpendicular to the conductor acts on the coil 103a, and since the objective lens holder is also elastically supported in that direction by the conical spring 114, the force in the direction of the arrow A is applied to the coil 103a. Tracking is performed by displacing the

The conical spring 114 is arranged along the lens optical axis direction c, and its upper end is fixed to the base 110.
The lower end is fixed to the coil support 103.

However, as shown in Fig. 2, if the objective lens support device is such that the conical spring 114 is arranged along the lens optical axis direction, the upper end is fixed to the base, and the objective lens is fixed to the lower end, the dimensions in the lens optical axis direction are There is a major drawback. On the other hand, FIG. 6 of JP-A-51-68121 describes a structure in which an integrally formed elastic member is substantially connected between the lens holder and the base. However, the above-mentioned elastic member has a structure that allows it to bend mainly only in the focusing direction.

It is an object of the present invention to provide an objective lens support device that eliminates such drawbacks.

The objective lens support device of the present invention reads the information by irradiating convergent light with a lens onto a recording medium on which information is recorded in a track shape.
The lens is placed in a first direction perpendicular to the medium surface of the recording medium.
In the optical information reading device, the lens is driven by an electromagnetic driving means in a direction parallel to the medium surface and in a second direction parallel to the medium surface and across the information track, at least both of the first direction and the second direction. an elastic member that is flexible and integrally formed (constructed as a continuous piece without a joint connecting the elastic member in between) extends along the surface of the medium, and , the elastic member is substantially connected between a lens holder for holding the lens and a base, and further includes a focusing coil for driving the lens in the first direction and a focusing coil for driving the lens in the second direction. Both of the coils of the tracking coil for driving are integrally fixed to the lens holder, and the lens holder and both coils are configured to be integrally displaced. It is something.

FIG. 3 shows an embodiment of the objective lens support device of the present invention.

The main configurations in Fig. 3 that differ from Fig. 2 are as follows:
A spirally wound leaf spring 112 is arranged along the surface including the information track, one end is fixed to a fixing member 113 fixed to the base 110, and the other end is fixed to the objective lens 101. The structures of the focusing coil, tracking coil, focusing permanent magnet, and tracking permanent magnet are the same as in FIG. 2.

When a control current is applied to the focusing coil, the objective lens 101 is displaced in the C direction, which is the focusing direction, based on the action of the magnetic field formed by the focusing permanent magnet 104c.
On the other hand, when a control current is applied to the tracking coil, the objective lens 101 becomes a permanent magnet 1 for tracking.
It is displaced in the A direction, which is the tracking direction, based on the action of the magnetic field formed by 04a.

Furthermore, in the case of using an elastic member that can also be displaced in the information tracking direction B, such as the leaf spring 112, the coil support 103 is provided with a tracking coil in addition to the tracking coil.
A coil tightly wound in a spiral shape is fixed inside it,
The magnetic gap of the permanent magnet 104b is faced so as to sandwich the conductive wire of the coil from both sides, and the permanent magnet is arranged so as to be perpendicular to the tracking permanent magnet in a plane perpendicular to the optical axis of the objective lens.
When a control current is supplied to the coil, a force in the perpendicular direction acts on the conductor of the coil, and the objective lens can also be displaced in the direction of arrow B, which is the same direction as the information track.

As described above, the present invention includes an integrally formed elastic member that can be bent in the first direction and the second direction, and extends along the medium surface, and the elastic member is arranged between the lens holder and the base. Since the lenses are configured to be substantially connected, there is an effect that the dimension of the lens in the optical axis direction can be reduced with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the prior art, FIG. 2 is a diagram illustrating an improvement of the prior art, and FIG. 3 is a perspective view of an embodiment of the present invention. 101...Objective lens, 102...Objective lens barrel, 103a...Tracking coil, 10
3c...Focusing coil, 112...Spiral leaf spring, 113...Fixing member.

Claims (1)

[Scope of Claims] 1. When reading the information by irradiating convergent light onto a recording medium on which information is recorded in the form of a track, the lens is directed in a first direction perpendicular to the medium surface of the recording medium. In an optical information reading device, the lens is driven by an electromagnetic drive means in a second direction parallel to the medium surface and across the information track, wherein the lens is deflected in at least both the first direction and the second direction. and extending an integrally formed elastic member along the medium surface;
The elastic member is substantially connected between a lens holder for holding the lens and a base, and further includes a focusing coil for driving the lens in the first direction and a focusing coil for driving the lens in the second direction. Both of the coils of the tracking coil are integrally fixed to the lens holder, and the lens holder and both coils are integrally displaced. Lens support device.