JP2597973B2 - Optical head device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical head device for recording and reproducing information on and from an optical recording medium.

[Technical Background of the Invention and its Problems] With the recent improvement in digital signal processing technology, various digital recording methods have been developed, and problems in the conventional analog recording method have been improved to improve the recording signal. The noise and distortion of information are reduced, and the density of recorded information is increased. Among them, for example, using a disk on which a metal thin film is applied, various kinds of information are recorded by forming holes (pits) corresponding to the digitized data on the disk, and further, by detecting the presence or absence of these bits, the recording information is recorded. A device for regenerating an image is being put to practical use.

By the way, such a disk (hereinafter, "optical disk")
The pits are formed with a diameter of about 1.0 μm or less and with a track pitch of 1.0 to 2.0 μm as the density of recording information increases. Therefore, light is used to form pits for recording information on an optical disk or to detect the presence or absence of pits formed for reproducing information. For this purpose, an optical head is suitable for an optical disk. It is required that the optical head has a function of accurate tracking control and focus control, and a function of accurately positioning a light spot formed by the optical head for recording and reproducing information.

To meet such demands, the following optical head devices have been proposed. FIGS. 7 and 8 show a cross-sectional configuration and a planar configuration thereof, in which a relay member 16 is supported by a cylindrical fixing member 15 via a diaphragm diaphragm 17 for focusing, and an optical head is mounted on the relay member 16. It has a configuration in which a movable member 19 to which an objective lens 18 as a main body is attached is supported via a parallel plate spring 20 for tracking, and the movable member 19 is moved in focus and tracking directions in arrows A and B.

9 and 10 show a sectional configuration and a perspective view thereof, in which a relay member 22 is supported on a fixed member 21 by a parallel leaf spring 23 for focusing, and the relay member 22 is optically mounted on the relay member 22. A movable member 25 to which an objective lens 24 as a head body is attached is supported by a parallel leaf spring 26 for tracking.

By the way, in the optical head device having the structure in which the movable members 19 and 25 are movably supported two-dimensionally, the tracking control and the focus control can be stably performed even in response to an external shock. is required.
For this purpose, the servo band usually needs to be 2 kHz or more. Thus, in order to secure the servo band at about 2 kHz, the characteristics of the suspension in the device having the structure shown in FIG. 7 and FIG.
In other words, in the operating characteristics determined by the spring characteristics and the mass of the relay member and the movable member, the secondary resonance whose displacement phase is delayed by 360 degrees with respect to the driving force as shown in FIG.
It is necessary to reduce the vibration amplitude in the high-frequency region above Hz, and also to reduce the amplitude of other abnormal resonances.

However, in the configuration shown in FIG. 7, since the objective lens 18 is driven in the focusing direction via the parallel leaf spring 20 by applying a driving force to the relay member 16, the driving is performed in the focusing direction. In this case, the resonance frequency of the vibration system formed between the parallel leaf spring 20 and the objective lens 18, that is, the secondary resonance frequency was low, and a sufficient servo band could not be obtained.

Further, in the apparatus shown in FIG. 9, since the driving force in the focus direction and the tracking direction is directly applied to the movable member 25, the secondary resonance shown in FIG. 11 does not appear. However, a parallel leaf spring displaced in the focus direction
23 and the parallel leaf spring 26 displaced in the tracking direction, due to the mass of the relay member 22, an abnormal resonance point as shown in FIG. The movable body resonates at the resonance frequency, and the control system becomes unstable. In addition, when the movable member 25 is moved and displaced in the focus direction, a reaction force of inertia force received by the relay member acts on the movable member 25, and the reaction force induces abnormal vibration.

[Object of the Invention] The present invention has been made in view of such circumstances.
It is an object of the present invention to provide an optical head device having an objective lens support mechanism that does not generate abnormal vibration, has good vibration characteristics, and is capable of highly accurate tracking control and focusing control.

[Summary of the Invention] An objective lens, a holder for holding and fixing the objective lens, a first elastic member having one end fixed to the holder and capable of moving the objective lens in the optical axis direction, and the elasticity A relay member for fixing the other end of the member, a second elastic member for fixing one end to the relay member and enabling movement of the objective lens in a direction orthogonal to the optical axis, and a second elastic member. A fixing member for fixing an end, wherein the first elastic member includes a plurality of leaf springs having flexibility in the direction of gravity, and the second elastic member has a direction perpendicular to the direction of gravity. An optical head device comprising a plurality of leaf springs having flexibility and being arranged substantially crosswise with each other.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing the present invention, and FIG. 2 is a plan view thereof.

An objective lens 1 for converging a light spot on a disk surface is fixed to a coil unit 2 formed of a rigid body. One end of a focus spring 3 composed of two parallel leaf springs made of a metal or other elastic member arranged perpendicular to the optical axis in order to move the entirety in parallel in the focus direction F which is the optical axis direction without twisting. Are fixed to the coil unit 2, and the other end is fixed to the relay member 4. The above is the support structure in the focus direction.

On the other hand, one end of a tracking spring 5 composed of two sets of cross springs orthogonal to each other is fixed to the relay member 4 so as to form a vertical plane with the focus spring 3. The other ends of these tracking springs 5 are fixed to a fixed support 6. The above is the support structure in the tracking direction. In this way, the focus spring 3 composed of a pair of parallel leaf springs is deformed while maintaining a parallelogram relationship, and the tracking spring 5 composed of a pair of cross springs is formed.
Is rotationally deformed around the optical axis of the objective lens 1,
In any moving direction, the optical axis of the objective lens 1 itself is perpendicular to the disk.

The coil unit 2 includes a movable body 7, a focus coil 8, and a tracking coil 9, which form a frame. The focus coil 8 is attached to the movable body 7 in parallel with the upper end or the lower end of the movable body 7, that is, the objective lens 1. The planar tracking coil 9 wound perpendicular to the optical axis direction and wound in a substantially rectangular shape has a side parallel to the optical axis of the objective lens 1 of the tracking coil 9 and a tracking direction T of the movable body 2. It is fixed so that it is arranged at both ends of the parallel side.

The coil drive system 10 includes magnetic pole members 11 and 12 made of a material such as iron that allows a magnetic force to pass therethrough, and a permanent magnet 13 that magnetizes the magnetic pole members. The magnetic pole members 11 and 12 have magnetic poles 11a and 12a which are disposed at both ends of the long side of the coil unit 2 so as to be parallel to the sides and spaced from the coil unit 2 by an appropriate length.

Next, the operation of the optical head device thus configured will be described. The focus coil 8 of the coil unit 2 surrounds the side surface of the frame portion of the movable body 7,
The movable body 7 extends in parallel with the upper edge and the lower edge. That is, the conductor from the focus coil 8 is perpendicular to the force direction. On the other hand, the magnet 13 applies a magnetic field between the magnetic poles 11a and 12a. This magnetic field crosses the conductor of the focus coil 8 so as to be orthogonal to the focus direction F and the tracking direction T. Therefore, when the focus coil 8 is energized, a force acts on the focus coil 8 and the coil unit 2 in a direction orthogonal to the current and the magnetic field, that is, a focus direction F, according to Fleming's law. The magnitude and direction of this force are determined by the magnitude and direction of the current flowing through the focus coil 8. Under this force, the focus spring 3 is deformed while keeping the coil unit 2 and the relay member 4 parallel, as shown in FIG. 3, and the coil unit 2 and thus the objective lens 1 are moved in parallel in the focus direction F.

On the other hand, between the magnetic poles 11a and 12a, there are portions of the tracking coil 9 located at both ends of the long side of the coil unit 2 and sandwiched between the magnetic poles 11a and 12a. When the tracking coil 9 is energized, the direction between the current flow and the direction perpendicular to the magnetic field, that is, the tracking direction, is applied to the rectangular portion 9a extending in the focus direction F between the magnetic poles 11a and 12a by the Fleming's law. Power works on T. Therefore,
By passing a current through the tracking coil 9, the tracking coil 9, and eventually the coil unit 2, receive a force in the tracking direction T, and the direction and magnitude of the force are determined by the direction and magnitude of the current flowing through the coil. By this force, the tracking spring 5 is elastically deformed as shown in FIG. 4 (before deformation (a) and after deformation (b)), and the relay member 4 rotates and moves with respect to the fixed support 6. , Resulting in coil unit 2 and objective lens 1
Moves in the tracking direction T.

In the device configured as described above, the objective lens 1
The movement in the tracking direction T has a structure in which the rotational deformation of the tracking spring 9 is enlarged by the focus spring 3. And the relay member 4 is
Since the tracking spring 5 is disposed at a position close to the rotation center, the equivalent mass of the relay member 4 is sufficiently smaller than the equivalent mass of the coil unit 2 (the equivalent mass is proportional to the square of the radius from the rotation center). Therefore, the resonance frequency of the abnormal resonance conventionally appearing at 1 to 2 kHz can be shifted to a high frequency range which does not affect the tracking and the focus servo. Further, since the equivalent mass of the relay member 4 is reduced, the coil unit 2 is moved in the focus direction F.
Alternatively, when moving and displacing in the tracking direction T, the reaction force of the inertial force of the relay member 4 received by the coil unit 2 is small, and the abnormal vibration amplitude is sufficiently small. As described above, since the relay member causing the vibration reduces the force exerted on the movable body, the resonance frequency of the abnormal resonance can be shifted to a high frequency which does not affect the control system. It can be realized, and a great effect can be obtained in practical use.

[Other Embodiments of the Invention] The present invention is not limited to the above embodiments.
For example, as shown in FIG.
A single leaf spring 14 that is parallel to the focus direction F and perpendicular to the focus spring 3 may be used as the elastic support member that is rotated and displaced with respect to.

[Brief description of the drawings]

1 is a partially cutaway perspective view showing a principle view in one embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 4 is a side view showing an operation principle, and FIG. 4 is a plan view showing an operation principle. 5 is a partially cutaway perspective view showing the second embodiment, FIG. 6 is a plan view of FIG. 5, FIG. 7 is a cross-sectional view showing a conventional example, and FIG. 8 is a plan view of FIG. 9, FIG. 9 is a cross-sectional view showing another conventional example, FIG. 10 is a perspective view, and FIGS. 11 and 12 are diagrams illustrating resonance often appearing in an optical head device. DESCRIPTION OF SYMBOLS 1 ... Objective lens 2, ... Coil unit, 3 ... Focus spring, 4 ... Relay member, 5 ... Tracking spring, 6 ... Fixed support, 7 ... Movable body, 8 ... Focus coil, 9 ... Tracking coil, 9 ... Coil drive system, 11 ... Magnetic pole member, 12 ... Magnetic pole member, 13 ... Permanent magnet.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-138903 (JP, A) JP-A-58-62832 (JP, A) JP-A-58-62836 (JP, A) 179661 (JP, U)

Claims (2)

(57) [Claims] An objective lens; a holder for holding and fixing the objective lens; a first elastic member fixed at one end to the holder for enabling the objective lens to move in the optical axis direction; A relay member that fixes the other end of the member, a second elastic member that fixes one end to the relay member and allows the objective lens to move in a direction perpendicular to the optical axis, and a second elastic member. A fixing member for fixing an end, wherein the first elastic member is constituted by a plurality of leaf springs having flexibility in the direction of gravity, and the second elastic member is in a direction orthogonal to the direction of gravity. An optical head device comprising: a plurality of leaf springs having flexibility and being arranged substantially crosswise with each other. 2. The optical head device according to claim 1, wherein said first elastic member comprises a plurality of leaf springs arranged in parallel with each other.