JPH1166585A - Apparatus for driving objective lens in optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed reading by bonding via an adhesive layer a reinforcing member of a material of higher rigidity than a material of a bobbin to a lower face and/or an upper face in a focusing direction of the bobbin, and increasing a secondary resonant frequency of an actuator while restricting a thickness increase to a minimum. SOLUTION: A bobbin 22 of synthetic resin holds an objective lens 7 at the center, with having a focusing coil 2b wound at an outer circumferential side face, thus forming a main body of a movable part 2. The bobbin 22 is fixed to a free end of an elastic member which has one end fixed to a fixed part 3 and is constituted of a parallel spring or the like. The bobbin 22 is accordingly supported to be movable in a focusing direction subsequent to a bend of the elastic member. A reinforcing plate 2a of aluminum alloy or the like is bonded to a lower face of the bobbin 22 in the focusing direction via an adhesive layer 2e which is formed by applying thick a highly viscous adhesive to an elastic body such as rubber or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device in an optical pickup for reading information from an optical disk.

[0002]

2. Description of the Related Art Optical disks are widely used today as storage media for computers and music / image information in audiovisual equipment.
In the case of this optical disk, the recording density is designed to be very high, and the speed of an optical pickup for reading recorded information is also increasing. Achieving high speed 1
One of the techniques is a technique of increasing the number of rotations of an optical disc.

The method of increasing the number of rotations of the disk has the following problems. First, in the optical disk system,
It is necessary to always control the spot collected by the objective lens on the optical disc in the focus direction and the tracking direction. Therefore, closed-loop servos are respectively formed, and the servo band is determined mainly by the rotation speed of the disk. For example, the current CD
Assuming that the focus servo band of the 8 × speed drive of the ROM is designed at 2 kHz, the focus servo band of the 16 × speed drive is simply designed at 4 kHz. In order to realize a stable servo, the secondary resonance frequency of the actuator of the optical pickup, for example, the biaxial actuator needs to be at least 5 to 10 times the servo band. Therefore, as the speed of the optical disk increases and the number of rotations increases, the servo band increases and the secondary resonance frequency of the biaxial actuator must be increased. However, 2
Since the secondary resonance frequency of the axis actuator is the structural resonance frequency of the movable part, there is a limit depending on the structure. Therefore, for high-speed reading of an optical disk, it is necessary to develop a new two-axis actuator with a higher structural resonance frequency. When the structural resonance frequency is increased, the thickness of the biaxial actuator generally increases, and it becomes difficult to reduce the thickness of the optical pickup.

[0004]

As described above, in the conventional optical pickup, the thickness of the biaxial actuator increases when high-speed reading is performed, and the thickness of the optical pickup also increases, thereby sacrificing the thickness reduction. There was a problem of becoming.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to minimize the increase in thickness.
It is an object of the present invention to provide an objective lens driving device in an optical pickup that can realize high-speed reading by increasing the structural resonance frequency. Still other objects will be sequentially clarified in the contents described below.

[0006]

The present invention has the following technical means in order to achieve the above object. That is,
A fixed part, a movable part having an annular bobbin having a focusing coil mounted on the outer peripheral side with an objective lens fixed substantially at the center, and one end fixed to the fixed part and the other end An objective member driving device for an optical pickup, comprising: an elastic member that movably supports the movable portion in a focusing direction by flexural deformation, wherein the bobbin is provided on a lower surface and / or an upper surface of the bobbin in the focusing direction. This is a configuration in which a reinforcing member made of a material having a higher rigidity than the constituent material is attached. In the configuration of the present invention, it is more preferable that an elastic body such as rubber or an adhesive layer provided with a thick adhesive having a high viscosity is interposed between the bobbin and the reinforcing member.

According to this, by attaching the reinforcing member to the bobbin, the rigidity of the entire movable part is increased, and the secondary resonance frequency of the actuator (the structural resonance frequency of the movable part) is increased.
Can be raised. This is more effective than simply increasing the thickness of the bobbin. That is, in principle,
In order to realize the same secondary resonance frequency, it is possible to reduce the thickness of the movable part by attaching a material having a higher rigidity than when simply increasing the thickness of the bobbin. Further, when an elastic body such as rubber or a thick adhesive layer is sandwiched between the bonded portions, a damping effect is generated, and the peak level of the secondary resonance frequency can be suppressed.

[0008]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to these embodiments unless otherwise specified in the following description of the embodiments.

1 to 3 show an objective lens driving device according to one embodiment of the present invention. FIG. 1 is a sectional view taken along line AA of FIG. 2, and FIG. 2 is a schematic plan view of the objective lens driving device according to the present invention. FIG. 3 and FIG. 3 are schematic external perspective views of the device of the present invention. 1 to 3, the objective lens 7 is made of a synthetic resin or the like, and a bobbin 22 having a through hole 21 in the center and made in an annular shape is connected to the optical axis of the objective lens 7 through the through hole. 2
1 and fixed with an adhesive or the like in a state of being aligned with the center. The bobbin 22 serves as a main body of the movable section 2,
A focusing coil 2b is wound around the outer peripheral side surface. A reinforcing plate 2a as a reinforcing member is provided on the lower surface of the bobbin 22 in the focusing direction.

The reinforcing plate 2a is made of a material of the bobbin 22;
For example, if the bobbin 22 is made of a synthetic resin, a material having a higher rigidity than that is used. Specific examples thereof include materials such as an aluminum alloy and a magnesium alloy. Then, the reinforcing plate 2a is bonded or laminated with an elastic layer such as rubber or an adhesive layer 2e formed by applying a thick adhesive such as a thick adhesive such as this one between the bobbin 22 and the reinforcing plate 2a. It is fixed in the form of a system. Here, the shape of the reinforcing plate 2a is substantially the same as the projected surface of the lower surface of the bobbin 22, that is, substantially the same surface shape as the corresponding surface of the bobbin 22. However, the present invention is not limited to this, and the plate shape of the reinforcing plate 2a may be a rectangular or triangular corner or a semicircular rod. In this case, it is also possible to configure the reinforcing member as an arbitrary number of rods, and it is relatively easy to obtain an optimum state according to the design value. The surface of the reinforcing plate 2a may have, for example, a convex shape or a waveform other than a flat surface. This is particularly effective, for example, in a case where the adhesive layer 2e is formed by providing a thick viscous adhesive between the bobbin 22 and the reinforcing plate 2a.

Therefore, in this structure, the overall rigidity of the movable part 2 is increased by the reinforcing plate 2a attached to the bobbin 22 as compared with the conventional structure,
In order to realize the next resonance frequency, it is possible to make the bobbin thinner than a conventional method of simply increasing the thickness. Further, since the reinforcing plate 2a is provided in a state where the elastic body such as rubber or the adhesive layer 2e is interposed, a damping effect is generated, and the peak level of the secondary resonance frequency of the actuator (the structural resonance frequency of the movable portion) is reduced. It will be extremely effective in suppressing it.

More specifically, the movable portion 2 has an elastic member 4 having one end fixed to the fixed portion 3 and the other end formed by a pair of parallel springs extending from the fixed portion 3. The bobbin 22 is fixedly supported on the free end (the other end side) of the member 4, and the bobbin 22 is movable together with the objective lens 7 in the focusing direction by obtaining the bending deformation of the elastic member 4. The fixing portion 3 is fixed to a yoke base 5 made of a magnetic material such as iron. The yoke base 5 is formed with a pair of yokes 5a, each of which is partly bent in the focusing direction.
The magnet 6 is fixed to the opposing surface of the substrate by an adhesive or the like. When a current flows through the focusing coil 2b, the movable section 2 holding the objective lens 7 is driven in the focusing direction while bending and deforming the elastic member 4 based on the magnitude and direction of the current.

FIG. 4 is a schematic configuration diagram showing an example of an optical pickup device using the objective lens driving device 1. As shown in FIG. This optical pickup device is called a separation type in which a movable part is reduced in weight to cope with high-speed access. The movable optical system mainly includes a fixed optical system 17 and an objective lens driving device 1. It consists of eight. The fixed optical system 17 includes a semiconductor laser 9 as a light source, a light receiving element 10 for detecting a focusing error signal, a tracking error signal, an RF signal, and the like, a galvanomirror 12 that rotates based on the tracking error signal, and the like. The fixed optical system 17 is fixed to a chassis or the like of the optical recording / reproducing apparatus, and the movable optical system 8 can be moved in the tracking direction by driving means (not shown) such as a driving linear motor.

Next, the operation of the optical pickup device will be described. First, the laser light emitted from the semiconductor laser 9 is converted into parallel laser light by the collimator lens 13, reflected by the total reflection surface 14 a and the polarizing film formation surface 14 b of the beam splitter 14, and
It is led to. The laser light reflected by the galvanomirror 12 is reflected by the mirror 15 of the movable optical system 8 toward the optical recording medium (optical disk) 11, and is held by the movable section 2 of the objective lens driving device 1. Is focused on the optical recording medium 11. The laser beam reflected by the optical recording medium 11 passes through the objective lens 7, is reflected by the mirror 15 and the galvanometer mirror 12, passes through the beam splitter 14 and the condenser lens 16, is focused on the light receiving element 10, and is focused. Error signal, tracking error signal, RF
A signal or the like is detected.

In the above embodiment, as a means for increasing the rigidity and damping of the movable portion 2 of the objective lens driving device 1, a reinforcing plate 2 is provided on the lower surface of the movable portion 2 in the focusing direction.
Although the structure in which a is fixed is disclosed, the reinforcing plate 2a may be fixed on the upper surface of the movable portion 2 in the focusing direction.
If the reinforcing plate 2a and the elastic body such as rubber or the adhesive layer 2e are fixed to the upper and lower surfaces in the focusing direction of the movable portion 2, respectively,
The rigidity of the movable portion 12 can be further increased. Also,
The objective lens driving device 1 is not limited to a configuration in which the objective lens 7 is driven only in the focusing direction, and may be a so-called two-axis actuator in which the objective lens 7 can be moved in both the focusing direction and the tracking direction. That is, also in this biaxial actuator, only the reinforcing plate 2a or the reinforcing plate 2a is fixed to the lower surface in the focusing direction of the movable portion 2 holding the objective lens 7 with an elastic body such as rubber or an adhesive layer 2e sandwiched therebetween. Method, only the reinforcing plate 2a, or a method in which the reinforcing plate 2a is fixed to the upper surface in the focusing direction with an elastic body such as rubber or an adhesive layer 2e sandwiched therebetween, only the reinforcing plate 2a, or the reinforcing plate 2a
Is fixed to the upper and lower surfaces in the focusing direction with an elastic body such as rubber or an adhesive layer 2e sandwiched therebetween, thereby increasing the rigidity of the movable portion 2.

As described above, in the objective lens driving device 1 according to the present invention, the rigidity and the damping of the movable portion 2 to which the objective lens 7 is fixed can be increased, so that the multiple resonance frequency is shifted to a higher frequency range. In addition, it is possible to provide the objective lens driving device 1 in which the peak level is suppressed. When the optical pickup device is realized using the objective lens driving device 1, it is possible to increase the focusing and tracking servo bands.

[0017]

As described above, according to the objective lens driving device for the optical pickup according to the present invention, the following effects can be obtained. By increasing the secondary resonance frequency (structural resonance frequency) of the biaxial actuator of the optical pickup, higher-speed reading of the optical disk can be realized. In order to increase the secondary resonance frequency (structure resonance frequency), the increase in the thickness of the biaxial actuator can be minimized. Since only a predetermined structural material (reinforcing member) is attached without a major design change of the current two-axis actuator, the secondary resonance frequency (structural resonance frequency) can be easily increased, and The peak level of resonance can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along line AA of FIG.

FIG. 2 is a schematic plan view of the device of the present invention.

FIG. 3 is a schematic external perspective view of the device of the present invention.

FIG. 4 is a schematic configuration diagram showing an example of an optical pickup device using the objective lens driving device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens driving device 2 Movable part 2a Reinforcement plate (reinforcement member) 2e Adhesive layer 3 Fixed part 4 Elastic member 7 Objective lens 22 Bobbin

Claims (5)

[Claims] A movable section having a fixed section, an objective lens fixed substantially at the center, and a bobbin on which a focusing coil is mounted on an outer peripheral side, and one end side fixed to the fixed section; An objective lens driving device for an optical pickup, comprising: an elastic member that supports the movable portion in the focusing direction by bending deformation on the other end side; wherein a lower surface and / or an upper surface of the bobbin in the focusing direction are provided; An objective lens driving device for an optical pickup, wherein a reinforcing member made of a material having a higher rigidity than a material forming the bobbin is attached. 2. The objective lens driving device according to claim 1, wherein the reinforcing member has a plate shape substantially equivalent to a corresponding projection surface of the bobbin. 3. The objective lens driving device according to claim 1, wherein the reinforcing member has a rod shape. 4. The objective lens driving device in an optical pickup according to claim 1, wherein an elastic body such as rubber is interposed between the bobbin and the reinforcing member. 5. The objective lens driving device for an optical pickup according to claim 1, wherein an adhesive layer is interposed between the bobbin and the reinforcing member.