JPH05314512A - Device for driving objective lens - Google Patents

Abstract

PURPOSE:To thin and miniaturize an objective lens drive device and to stabilize servo control by utilizing materials with different elastic moduli to two leaf springs holding a dumping material therebetween and making their resonance frequencies disagree. CONSTITUTION:In the objective lens drive device, a movable part containing a bobbin 102, a focusing coil 104, a holder 105 and an objective lens 106 is held therebetween by a set of suspensions 101 of a parallel leaf spring shape and supported to a base 103. The suspension 101 is constituted of two leaf springs and a sheet of dumping material and the leaf springs are stuck by the adhesion of the dumping material while holding the dumping material therebetween and they are seemed as a leaf spring in appearance. In an actual operational condition, the leaf spring generates not only first vibration but also some kinds of division vibration, as well simultaneously. Thus, by utilizing the materials with different elastic moduli respectively to two leaf springs, the resonance frequencies of two leaf springs are constituted so as to make disagree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device,
In particular, it relates to an objective lens driving device.

[0002]

2. Description of the Related Art As shown in the structure of the focusing portion in the objective lens driving device described in JP-A-57-103131, a normal plate material is used for the plate spring.

[0003]

Since the conventional objective lens driving device has a problem that the leaf spring causes resonance,
It was difficult to stabilize the servo control.

An object of the present invention is to stabilize servo control by solving the resonance problem in the objective lens driving device.

[0005]

DISCLOSURE OF THE INVENTION The present invention for solving the above-mentioned problems provides an objective lens driving device for controlling the position of an objective lens by electromagnetic action of a coil and a magnet of an optical disk device for optically recording and reproducing information. The suspension supporting the movable part of the objective lens driving device has a three-layer structure in which a damping material is sandwiched between two leaf springs, and the two leaf springs sandwiching the damping material have different elastic coefficients. It is characterized by using materials.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiments. The same reference numerals represent the same members.

FIG. 1 shows a first embodiment of the present invention. Bobbin 102, focusing coil 104, holder 10
The movable portion including the objective lens 106 and the objective lens 106 is sandwiched between a pair of parallel leaf spring suspensions 101, and the base 1
It is supported by 03.

The structure of the objective lens driving device will be described with reference to the exploded view shown in FIG. 2 movable parts on bobbin 102
Attach the focusing coils 104 to the left and right,
A holder 105 on which an objective lens 106 is placed is attached on the top. Further, a balancer 107 is attached below to adjust the center of gravity of the movable part. The movable part configured in this way is sandwiched between the suspensions 101 from above and below, and at the same time, the base 1
03 is also sandwiched and supported.

In the thus-assembled objective lens driving device, the base 103 shown in FIG. 1 is on the fixed side, and the movable part can move up and down.

Next, the role of the objective lens driving device will be described with reference to the drawings. The exploded view shown in FIG. 3 shows the configuration of the optical head driving device in the optical disk device. After attaching the tracking magnet 3 to the lower yoke 5 and inserting the middle yoke 2 and the support shaft 6 into the optical head constituted by the tracking coil 4, the carriage 11, the bearing 9 and the objective lens driving device 12 according to the dashed line in the figure, Attach to the lower yoke 5. Next, the upper yoke 1 having the tracking magnet 3 attached to the lower surface is attached to the middle yoke 2 penetrating the tracking coil 4. As a result of assembling in this way, the optical head driving device shown in FIG. 4 is completed. Figure 4
In FIG. 3, the spindle motor 10 and the optical disk 15 are further described, and the positional relationship between them is shown.

The optical system of this embodiment is divided into a fixed optical system and an optical head. As shown in FIG. 4, laser light emitted from a fixed optical system (not shown) enters the optical head as incident light 17, and the optical path is bent by the prism 16 shown in FIG. Laser light is emitted to the optical disk 15 as the emitted light 18. The irradiated laser light is condensed by the objective lens driving device 12 to form a spot 19 on the recording surface of the optical disc 15. The laser light reflected from the spot 19 travels backward in the above-mentioned incident optical path and returns to the fixed optical system to generate a control signal and a data signal. The position of the spot 19 is controlled along the track 20 on the recording surface of the optical disc 15 by using the control signal.

The position control is performed by controlling the position of the objective lens driving device 12 for controlling the size of the spot 19 in the direction perpendicular to the recording surface of the optical disk 15 and the driving direction 8.
Two types of position control of the optical head in the directions shown in FIG.

The present invention relates to position control in the direction perpendicular to the recording surface of the optical disk 15 with respect to the objective lens driving device 12 among the two types of position control.

FIG. 5 shows a focusing magnet 22 and a focusing yoke 2 in the optical head driving device shown in FIG.
1 shows a combination state with the objective lens driving device 12 to which 1 is added. The objective lens driving device 12 moves between the facing focusing magnets 22 as shown in the driving direction 8.

FIG. 6 shows the positional relationship between the focusing magnet 22 and the focusing coil 104. Four focusing magnets 22 are used, and two pairs of focusing magnets 22 are combined so that the magnetic poles alternate with each other, and the respective pairs are arranged so as to face each other. Two focusing coils 104 attached to the movable part of the objective lens driving device 12 are mounted in the magnet arrangement with the linear parts facing the magnetic poles. The focusing coils 104 are connected in series, and one terminal of each coil is connected to a drive circuit (not shown).

As shown in FIG. 7, the magnetic field 109 produced by the focusing magnet 22 is generated across the focusing coil. The movable portion is driven as shown in the focusing driving direction 108 by causing a current to flow from the driving circuit to the focusing coil 22 in the magnetic field 109 in a direction perpendicular to the paper surface. FIG. 8 is a side view of this driving state. With the base 103 fixed to the carriage 11 as a fixed end, the movable portion is in the driving direction 1
The suspension 101 is bent and moved in the direction of 08.

As shown in FIG. 10, the suspension 10
1 is composed of two leaf springs 110a and 110b and one sheet of damping material 111, and the leaf springs 110a and 110b are joined by sandwiching the damping material 111 due to the adhesiveness of the damping material 111. It looks like an upper leaf spring. Also,
The material of the vibration damping material 111 is a viscoelastic material having a function of suppressing vibration by converting vibration energy into heat energy, and a material containing an acrylic polymer material as a main component is used.

In an actual operating state, the leaf springs 110a and 110b simultaneously generate not only the primary vibration as shown in the suspension 101 of FIG. 8 but also some divided vibrations due to the operation of the movable part. At this time, if the conventional leaf spring is used without using the suspension 101, the structure shown in FIG.
Resonance that makes servo control unstable like the transfer function shown in the Bode diagram of FIG.
If 1 is used, resonance is suppressed like the transfer function shown in the Bode diagram of FIG. 9B.

However, when the flat springs 110a and 110b have the same plane shape, the same thickness and the same material, the flat springs 110 are formed.
Since a and 110b resonate in the same vibration mode, the damping effect by the damping material is small. When the control band is widened in order to increase the speed of the optical disk device, FIG.
If resonance remains like the transfer function shown in the Bode diagram, the servo control becomes unstable.

For this reason, in this embodiment, the resonance frequencies of the two leaf springs do not match because the leaf spring 110a and the leaf spring 110b shown in FIG. 10 are made of materials having different elastic coefficients. I did it. When the resonance frequencies match, the amount of deformation of the viscous material 111 due to bending is small as shown in FIG. 11A, but when the resonance frequencies do not match, one leaf spring is Since only this deforms, the amount of deformation of the viscous material 111 increases, so that the vibration energy absorbed by the viscous material 111 increases.
As a result, the transfer function of the movable portion of the objective lens driving device in this embodiment becomes a resonance-free transfer function as shown in FIG. 9C.

[0021]

According to the present invention, by solving the resonance problem in the objective lens driving device, not only the servo control can be stabilized, but also the speed of the optical disk device can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an objective lens driving device according to an embodiment of the present invention.

FIG. 2 is an exploded view illustrating an objective lens driving device according to an embodiment of the present invention.

FIG. 3 is an exploded view for explaining the purpose of the embodiment of the present invention.

FIG. 4 is a perspective view illustrating an object of an embodiment of the present invention.

FIG. 5 is a perspective view illustrating an entire objective lens driving device according to an embodiment of the present invention.

FIG. 6 is a plan view illustrating the arrangement of the embodiment of the present invention.

FIG. 7 is a plan view illustrating the operation of the embodiment of the invention.

FIG. 8 is an explanatory diagram for explaining the operation of the embodiment of the present invention.

FIG. 9 is an explanatory diagram for explaining the effect of the embodiment of the present invention.

FIG. 10 is an exploded view for explaining details of the embodiment of the present invention.

FIG. 11 is an enlarged view for explaining the effect of the embodiment of the present invention.

[Explanation of symbols]

 1 Outer Yoke 2 Middle Yoke 3 Tracking Magnet 4 Tracking Coil 5 Lower Yoke 6 Support Shaft 7 Magnetic Field Created by Tracking Magnet 8 Driving Direction 9 Bearing 10 Spindle Motor 11 Carriage 12 Objective Lens Drive 13 Optical Head 14 Light Emitting Direction 15 optical disk 16 prism 17 incident light 18 emitted light 19 spot 20 track 21 focusing yoke 22 focusing magnet 101 suspension 102 bobbin 103 base 104 focusing coil 105 holder 106 objective lens 107 balancer 108 driving direction 109 magnetic field created by focusing magnet 110a , 110b Leaf spring 111 Damping material

Claims (1)

[Claims] 1. An objective lens driving device for controlling the position of an objective lens by electromagnetic action of a coil and a magnet of an optical disc device for optically recording and reproducing information, wherein a suspension for supporting a movable part of the objective lens driving device is provided. An objective lens having a three-layer structure in which a damping material is sandwiched between two leaf springs, and the materials of the two leaf springs sandwiching the damping material are materials having different elastic coefficients. Drive.