JPH0426976Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an optical system support device used, for example, in an optical head for reproducing information recorded on an optical recording disk or for recording information on such a disk. It is.

(Prior Art) Conventionally, a support mechanism that supports an objective lens for irradiating a light spot onto a recording medium so as to be movable in a focusing direction parallel to the optical axis of the objective lens and in a tracking direction perpendicular to the focusing direction; Optical heads equipped with drive mechanisms for driving in the focusing and tracking directions are known and are described, for example, in Japanese Patent Application Laid-open No. 104733/1983. In this known optical head, an optical system including an objective lens for irradiating a light spot onto a recording medium is held by a holding member such as a lens frame, and a focusing leaf spring and a tracking leaf spring are provided between the holding member and the base. An optical system support mechanism is provided which supports the objective lens movably in the focusing direction and the tracking direction, and further includes a focusing coil for driving the objective lens in the focusing direction and a focusing coil for driving the objective lens in the tracking direction. The tracking coil is mounted on the objective lens holding member, and a drive current corresponding to a tracking error signal and a focusing error signal is supplied to each coil to perform tracking control and focusing control. However, in this known optical head, the focusing coil and the tracking coil are mounted at different positions on the objective lens holding member when viewed in the optical axis direction, so the center of gravity of the entire objective lens holding member is concentrated. This has the disadvantage that the movement of the objective lens becomes unstable. That is, it is extremely difficult to mount the objective lens, focusing coil, and tracking coil so that the center of gravity of the entire objective lens holder is concentrated. For this reason, the center point on which the driving force for focusing control and tracking control acts does not exactly match the center of gravity, and the rotational torque depending on the distance between the center point and the center of gravity is applied in both the focusing and tracking directions. This occurs around an axis extending in a direction perpendicular to , the objective lens holding member undergoes a rotational movement, and a torsional force acts on the leaf spring. In this case, if the rotational frequency of the rotational movement matches the resonance frequency determined by the moment of inertia of the entire holding member and the torsional rigidity of the leaf spring, a high-order torsional resonance state will occur, making it impossible to accurately control the drive. This torsional resonance vibration will occur even when the focusing coil and tracking coil are installed integrally, if the point of force application and the center of gravity are misaligned, so preventing torsional resonance vibration is a major issue. ing.

(Purpose of the invention) The purpose of the invention is to eliminate the above-mentioned drawbacks, to prevent torsional resonance from occurring in the optical system support device even if the center point of the driving force and the center of gravity do not exactly match, and to prevent the occurrence of torsional resonance of the objective lens. The present invention provides an optical system support device that can stop unstable movement.

(Summary of the invention) An optical system support device according to the present invention is an optical system support device in which a holder holding an objective lens for irradiating a light spot onto a recording medium is movably supported by an elastic support. is composed of a leaf spring, one end of the elastic support is fixed to the fixing member, and the other end is fixed to the holder, and the shape of the leaf spring is configured to be asymmetrical with respect to its central axis. , the leaf spring is characterized in that it has a damping characteristic that damps the torsional force generated around the extending direction of the leaf spring.

(Embodiment) FIGS. 1 to 4 show an embodiment of an optical head equipped with an optical system support device according to the present invention.
FIG. 1 is an exploded perspective view of the main parts, FIG. 2 is a plan view, FIG. 3 is a side view, and FIG. 4 is a sectional view. An objective lens 1 for irradiating a light spot onto a recording medium such as an optical disk is fitted onto a holding member 2.
This holding member 2 is displaced in a focusing direction F parallel to the optical axis of the objective lens 1 to focus the light spot onto the recording medium and to track an information track on the recording medium and a tracking direction T perpendicular to the optical axis.
The objective lens holding member 2 is connected to the base 3 via a support mechanism in order to displace the optical spot so that it follows the information track. In the present invention, this support mechanism consists of a pair of focusing plate springs 4a.
and 4b, a relay member 5, and a pair of tracking leaf springs 6a and 6b.
A pair of focusing plate springs 4a and 4b are arranged such that one end of each is attached to a side wall of the holding member 2 so as to extend in a direction perpendicular to the focusing direction F and the tracking direction T while facing each other in parallel when viewed in the focusing direction F. The other end is fitted into the grooves 2a and 2b formed in the relay member 5.
It is fitted and installed into the upper and lower grooves 5a and 5b bored in the. Further, the pair of tracking leaf springs 6a and 6b are arranged at an angle α as seen in the tracking direction T.
One end of each is fitted into left and right grooves 5c and 5d formed in the relay member 5 so as to extend in a direction substantially orthogonal to the focusing direction F and the tracking direction T while facing each other, and the other end is attached to the base. 3 and are fitted into grooves 7a and 8a formed in posts 7 and 8 integrally formed with each other.
The distance between one end of the above-mentioned pair of tracking leaf springs 6a and 6b on the relay member 5 is shorter than the distance between the other ends of the posts 7 and 8, and the angle α formed by these leaf springs 6a and 6b is preferably about 30°, for example.
In this way, the objective lens 1 can be supported movably in the focusing direction F and the tracking direction T, but the pair of focusing leaf springs 4a and 4b and the pair of tracking leaf springs 6a and 6b are both leaf springs. It can be constructed by simply cutting it to an appropriate length, and there is no need for bending processing as in the past, making it easy to manufacture and achieving the required characteristics relatively easily. On the other hand, the grooves 2a, 2b, and 5a to 5d that fit and hold the ends of these leaf springs can be precisely molded integrally with the support member 2 and the relay member 5.

Next, a driving mechanism for driving the objective lens 1 in the focusing direction F and the tracking direction T will be described. In this example, a pair of focusing coils 9a and 9b are fixed to the side surface facing the tracking direction T of the holding member 2, and a pair of tracking coils 10a and 10b are integrally attached to the outside of these focusing coils. do. The focusing coils 9a and 9b have a "square" shape when viewed in the focusing direction F, whereas the tracking coils 10a and 10
b has a "U-shaped" shape when viewed in the focusing direction F. These focusing coils 9
a, 9b and tracking coils 10a, 10
A magnetic field generating member that generates a magnetic field that cooperates with b includes a pair of yokes 11 and 12 made of a magnetic field material;
Legs 11a and 11 on both sides of one yoke 11
Permanent magnets 13a and 13b attached along b
and permanent magnets 14a and 1 attached along the legs 12a and 12b on both sides of the other yoke 12.
4b. These yokes 11 and 12 have their central legs 11c and 12
c are focusing coils 9a and 9, respectively.
Fix it to the base 3 so that it is inserted into the base 3.
The lead wires (only one of which is shown in FIG. 1) connected to the focusing coils 9a, 9b and the tracking coils 10a, 10b are attached to the holding member 2.
The rear leaf springs 4a, 4 are connected to terminals provided on the side surfaces of the rear leaf springs 4a, 4.
b, 6a, 6b, pass through the hole 5e made in the relay member 5, connect to the terminal of the printed circuit board 15 fixed to the base 3, and connect from there to the circuit. In this way, the lead wires are led together to the outside through the hole 5e drilled in the relay member 5, making it easier to wire the lead wires and reducing the influence of the lead wires on the movement of the objective lens 1. can be destroyed. Furthermore, since the holes 5e are formed in the relay member 5, the weight of the relay member 5 is reduced, and the characteristics of the support mechanism are improved.

Now, a focusing drive current having an amplitude and polarity depending on the magnitude and direction of the focusing error is applied to the focusing coils 9a and 9b.
, the focusing coils 9a and 9b, and therefore the holding member 2 and the objective lens 1, receive a force in the focusing direction F due to the interaction with the magnetic field passing through these coils, and the pair of focusing leaf springs 4a and 4b Due to the deflection of the lens, it is displaced in the focusing direction F, and the light beam can be focused on the recording medium as a minute light spot.
In this case, the relay member 5 also serves as the focusing plate spring 4.
Although the main surfaces of the tracking leaf springs 6a and 6b are parallel to the focusing direction F, they hardly deform in this direction, so the relay member 5 is not displaced in the focusing direction.
Therefore, the objective lens 1 can be accurately driven in the focusing direction F in response to the focusing drive current.

On the other hand, when a tracking drive current having an amplitude and polarity corresponding to the magnitude and direction of the deviation of the optical spot with respect to the information track is supplied to the pair of tracking coils 10a and 10b, the tracking coils 10a and 10b interact with the magnetic field.
0b, therefore the holding member 2 and the objective lens 1
receives a force in the tracking direction T, and the objective lens 1 is displaced in the tracking direction T by the deflection of the tracking leaf springs 6a and 6b. In this case, the relay member 5 receives a force in the tracking direction T, but the focusing leaf spring 4
Since the main surfaces of a and 4b extend in the tracking direction T and are not displaced in this direction, the force in the tracking direction T is accurately transmitted to the relay member 5, that is, the tracking leaf springs 6a and 6b. Therefore, the objective lens is accurately driven in the tracking direction T in response to the tracking drive current.

As mentioned above, focusing coils 9a, 9
By passing a focusing drive current and a tracking drive current through the tracking coils 10a and 10b, these coils receive a force. If the centers of gravity do not match, a rotational torque will be generated around the center of gravity depending on the force and the distance of deviation between the center point and the center of gravity. As in this example, focusing coils 9a and 9b and tracking coil 10a
and 10b are integrally mounted, the center point on which the driving force acts and the center of gravity of the movable part do not exactly match, and rotational torque is generated. In this case, in the conventional optical system support device, since one end of the focusing leaf springs 4a and 4b is firmly fixed to the relay member 5, the rotational torque generated in the movable part is transferred to the focusing leaf springs 4a and 4b.
As a result, a torsional rotational movement occurs at the connecting portion with the relay member 5 as a branch. When the rotational frequency of this torsional rotational motion matches the resonance frequency determined by the moment of inertia of the focusing leaf springs 4a and 4b and the entire movable part, a high-order resonance state occurs, and the movable part does not drive correctly, causing the focusing direction Accurate drive control in F and tracking direction T becomes impossible.

In the present invention, in order to prevent the occurrence of torsional resonance, the focusing plate springs 4a and 4b, which movably support the movable part, are themselves configured to have a damping effect. The rotational torque generated in the movable part is propagated to the flexible focusing plate springs 4a and 4b, and becomes a torsional force using the fixed end of the focusing plate spring, that is, the connection part with the relay member 5 as a fulcrum, and the focusing plate The torsional rigidity of the spring and the moment of inertia of the movable part cause a torsional rotational movement about the direction in which the leaf spring extends. Therefore, if the focusing plate springs 4a and 4b that support the movable parts themselves have a damping effect against the torsional rotational movement,
Torsional resonance occurring in the movable part and the focusing leaf spring can be effectively prevented. In this example, the shape of the focusing leaf spring is asymmetrical with respect to the central axis connecting the holding member 2 and the relay member 5 that constitute the movable part.
A and 4b are given damping characteristics.

5A to 5E are plan views showing various examples of focusing leaf springs according to the present invention. Same figure A~
In E, the central axis connecting the holding member 2 that holds the objective lens and the relay member 5 when the focusing leaf spring is attached is indicated by l. FIG. 5A shows protrusions 20a and 20 located asymmetrically on both sides of the central axis l with respect to the focusing leaf spring 20.
An example of providing asymmetry by providing b is shown. Figure B shows an example in which the leaf spring 21 is formed into a trapezoidal shape asymmetrical with respect to the central axis l to provide damping characteristics. Figure C shows an example in which the leaf spring 22 is shaped like a parallelogram inclined with respect to the central axis l to provide asymmetry. Figure D shows an example in which holes 23a and 23b are provided at asymmetrical positions on both sides of the central axis l for the focusing leaf spring 23 to provide asymmetry. Figure E shows an example in which a notch 24 is provided on one side of the central axis of the focusing leaf spring 24 to provide asymmetry. In other words, the leaf spring for focusing,
If the leaf spring is constructed asymmetrically with respect to the central axis l, the masses on both sides of the central axis l of the leaf spring will be different from each other, and as a result, the rotation moments will be different, thereby achieving a damping effect. The above-mentioned shapes of the focusing leaf springs are merely examples, and the shapes are not limited to these, and may be asymmetrical with respect to the central axis connecting the movable part and the fixed member when installed. All applicable. However, it is necessary that the elastic deformation required to perform focusing control by displacing the objective lens 1 in the direction of its optical axis is not adversely affected.

The present invention is not limited to the embodiments described above, but can be modified and modified in many ways. For example, in the above-described embodiment, the configuration is such that focusing control and tracking control are performed together, but the present invention can also be applied to a case where focusing control or tracking control is performed independently. In addition, in the above-described embodiment, the movable part including the objective lens and the driving coil was movably supported by two focusing plate springs, but the objective lens is held by one elastic support. The member may be supported in a freely movable manner.

Further, in the above-described embodiment, the focusing coil and the tracking coil are integrally attached to the holding member, but it goes without saying that the present invention can also be applied to an arrangement in which these coils are shifted in the direction of the optical axis of the lens. . In such cases, torsional resonance is particularly likely to occur, so the application of the present invention is effective.

(Effects of the invention) As explained above, according to the invention, since the focusing leaf spring that supports the movable part has a damping characteristic that damps the torsional force, the torsional resonance generated in the objective lens holding member can be effectively prevented, and the accuracy of focusing control and tracking control can be improved.

In addition, since the focusing plate spring is configured to have an asymmetrical shape with respect to the central axis connecting the objective lens holding member and the fixing member and has a damping property against torsional force, the focusing plate spring has a damping property. The leaf spring for use can be manufactured by simple processing and molding.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the structure of an embodiment of the optical head of the present invention, FIGS. 2, 3, and 4 are a plan view, side view, and sectional view thereof, and FIG. It is a top view which shows various examples of the leaf spring for focusing by. 1... Objective lens, 2... Holding member, 3... Base, 4a, 4b, 20, 21, 22, 23, 2
4...Focusing leaf spring, 5...Relay member, 6a, 6b...Tracking leaf spring, 7,
8... Post, 9a, 9b... Focusing coil, 10a, 10b... Tracking coil,
11, 12...Yoke, 13a, 13b, 14
a, 14b...Permanent magnet, 15... Printed circuit board.

Claims (1)

[Scope of utility model registration request] In an optical system support device in which a holder for holding an objective lens for irradiating a light spot onto a recording medium is movably supported by an elastic support, the elastic support is constituted by a leaf spring, and one end of the elastic support is The leaf spring is fixed to a fixed member and the other end is fixed to the holder, and the shape of the leaf spring is configured to be asymmetrical with respect to its central axis, and the torsion that occurs around the extending direction of the leaf spring is fixed. An optical system support device characterized in that it is configured to have a damping characteristic that attenuates force.