JPH09320082A - Objective lens driving apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an elastic member, which supports displaceably a lens bobbin to which an objective lens is attached, from plastic deformation, even when an external impact is applied. SOLUTION: Clank means 17, 18 which are narrower than the linear portion of the plate springs 15, 16 supporting a lens bobbin body 19 mounting an objective lend 21 to displace are provided at the base end portion of the plate spring members 15, 16. When an impact is applied from the external side, the crank portions 17, 18 are displaced to prevent bending of the linear portion of the spring portions 15, 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of an objective lens driving device used for constructing an optical pickup device for writing and reading an information signal to and from an optical recording medium such as an optical disk or a magneto-optical disk. Belong to

[0002]

2. Description of the Related Art Hitherto, optical recording media such as optical disks and magneto-optical disks have been proposed, and optical pickup devices for writing and reading information signals to and from these optical recording media have been proposed. The optical recording medium includes a transparent substrate made of a synthetic resin or glass, and a signal recording layer made of a magnetic material or a metal material formed on the main surface of the transparent substrate. The optical pickup device has a semiconductor laser as a light source, and focuses a light beam emitted from the semiconductor laser on the signal recording layer of the optical recording medium through the transparent substrate via an objective lens. It is configured to be. Further, the optical pickup device has a photodetector for detecting the reflected light of the light beam condensed on the signal recording layer by the signal recording layer.

[0003] In the optical recording medium, the signal recording layer is converged and irradiated with the light beam, or the irradiation of the light beam and the application of an external magnetic field are used in combination. Is written in the information signal. Further, in this optical recording medium, the information signal written on the signal recording layer is read out by detecting a change in the amount of reflected light of the light beam applied to the signal recording layer or a change in the polarization direction. It can be carried out.
In this optical pickup device, the semiconductor laser and the photodetector are positioned and held by the same frame. The frame is made of a material having sufficient rigidity such as metal or synthetic resin material.

In the above-described optical pickup device, it is necessary to always focus a light beam transmitted through the objective lens at a position where an information signal is written on the optical recording medium.

[0005] For example, when the optical recording medium is an optical disk, an information signal is formed along a recording track formed in a substantially concentric spiral on the signal recording layer of the optical disk. Written. The optical pickup device is moved in the radial direction of the optical disk while being opposed to the optical disk which is rotated and operated while holding the center portion, so that the relative position with respect to the optical disk is on the recording track. The information signal is written or read to or from the recording track while being moved along. Then, the optical pickup device has to make the condensing position of the light beam by the objective lens follow the displacement of the position of the recording track due to surface deflection and eccentricity of the optical disk.

Therefore, the above optical pickup device is
The objective lens is moved in a direction perpendicular to the optical axis direction (ie, focus direction) of the objective lens and the tangent line of the optical axis and the recording track (ie, tracking direction).
And an objective lens driving device (a two-axis actuator) for performing a moving operation. This objective lens driving device is movable in two directions of the focus direction and the tracking direction by supporting the objective lens via an elastic member such as a leaf spring member, and the objective lens is moved by an electromagnetic force. It is configured to move and operate in two directions. The objective lens driving device is mounted on the frame. Then, this objective lens driving device moves the objective lens based on an error signal (focus error signal and tracking error signal) indicating the amount of deviation between the recording position and the focus position of the light flux by the objective lens. To do. Therefore, the objective lens driving device is synchronized with the rotation cycle of the optical disc,
The objective lens is periodically moved.

[0007]

By the way, in an optical pickup device having the above-mentioned objective lens driving device, when an impact or strong vibration is applied from the outside, an elastic member for supporting the objective lens is provided. May be plastically deformed. When the elastic member is plastically deformed as described above, not only the position of the objective lens in the natural state is displaced, but also it is not possible to secure an appropriate moving range of the objective lens, and thus the optical recording medium It becomes impossible to write and read the information signal with respect to.

Therefore, the present invention is proposed in view of the above situation, and plastic deformation of the elastic member for supporting the objective lens even when vibration or impact is applied from the outside. SUMMARY OF THE INVENTION It is an object of the present invention to provide an objective lens driving device in which the above-mentioned problems are prevented and writing and reading of a good information signal with respect to an optical recording medium are not hindered.

[0009]

In order to solve the above-mentioned problems, an objective lens driving device according to the present invention has a lens bobbin to which an objective lens is attached, a linear portion and a crank portion, and a base end side is fixed. An elastic member that is mounted on the lens bobbin so that the lens bobbin is displaceably supported by the lens bobbin by being attached to the lens bobbin, and the elastic member is a base end of the elastic member. When an impact is applied in the direction of generating an inertial force toward the side, the lens bobbin is displaced in the crank portion until it comes into contact with a stopper member provided in the fixed portion.

Further, according to the present invention, in the objective lens driving device, the crank portion is provided on the base end side of the elastic member.

Further, according to the present invention, in the above-mentioned objective lens driving device, the crank portion is formed to be thinner than the linear portion.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, the objective lens driving device according to the present invention is used as an objective lens driving device (biaxial actuator) which constitutes an optical pickup device for writing and reading information signals to and from an optical disc which is an optical recording medium. It is a configured embodiment.

As the optical disc, a so-called magneto-optical disc capable of writing and reading information signals, or a disc capable of only reading information signals is used. The magneto-optical disk is made of polycarbonate (PC)
And a disc-shaped transparent substrate made of synthetic resin or glass,
A signal recording layer made of a magnetic material is formed on the main surface of the transparent substrate. In this magneto-optical disc, the signal recording layer is focused and irradiated with a laser beam to locally heat the signal recording layer to a temperature equal to or higher than the Curie temperature of the magnetic material forming the signal recording layer,
An information signal is written by applying an external magnetic field to this heated portion. In this magneto-optical disk, the signal recording layer is irradiated with a laser beam, and the change in the polarization direction of the laser beam reflected by the signal recording layer is detected, whereby the signal is written to the signal recording layer. Information signal can be read.

Further, the optical disk capable of reading only the information signal has a disk-shaped transparent substrate made of a synthetic resin such as polycarbonate (PC), and the information signal is formed by the pits formed on the main surface of the transparent substrate. A reflection film made of a metal material such as aluminum is adhered and formed on the main surface of the transparent substrate on which the pits are recorded and which is formed. In this optical disc, the reflection film serves as a signal recording layer. In this optical disc, the signal recording layer is irradiated with a laser beam, and a change in the amount of light reflected by the signal recording layer of the laser beam is detected to read an information signal written in the signal recording layer. It can be performed.

A chucking hole for positioning and holding the optical disk is provided at the center of the optical disk. When this optical disk is mounted on a recording / reproducing apparatus that records and reproduces information signals on the optical disk, it is positioned and held on a disk table of the recording / reproducing apparatus. The above disk table is
It is formed in a disk shape, and has a central portion attached to a drive shaft of a spindle motor of the recording / reproducing apparatus. A centering protrusion having a substantially truncated cone shape is provided in the central portion of the upper surface of the disc table. When the central portion of the optical disc 1 is placed on the disc table, the disc table fits the centering projections into the chucking holes to center and hold the optical disc. The optical disk held on the disk table is rotated by the spindle motor.

The optical pickup device equipped with the objective lens driving device according to the present invention has a frame. This frame is formed of a material having sufficient rigidity, such as aluminum die casting or a composite material of glass fiber and synthetic resin. As shown in FIG. 1, a semiconductor laser 26 serving as a light source is positioned and held in this frame. The semiconductor laser 26 emits a laser light flux and makes the laser light flux incident on the objective lens 21 supported by the objective lens driving device. The objective lens 21 irradiates the incident laser beam onto the signal recording layer of the optical disc by condensing it. The optical axis of the objective lens 21 is supported so as to be perpendicular to the signal recording layer of the optical disc, that is, parallel to the drive axis of the spindle motor.

This objective lens driving device has a base portion 1 which constitutes a fixed portion fixedly arranged on the frame. The objective lens driving device has a lens bobbin body 19 to which the objective lens 21 is attached. The lens bobbin body 19 is made of a synthetic resin material and has a frame-like shape. The objective lens mounting hole 2 into which the objective lens is fitted is attached to the front end side portion.
0 is provided. The objective lens 21 is fitted into the objective lens mounting hole 20 from above and mounted. The lens bobbin main body portion 19 is supported on both side portions with respect to the upper fixed block 9 constituting the fixed portion via a pair of leaf spring members 15 and 16 serving as elastic members.

The leaf spring members 15 and 16 are integrally formed in a thin and long plate shape from a metal material having appropriate elasticity such as phosphor bronze. The lens bobbin main body 19, the upper fixed block 9, and the leaf spring members 15 and 16 are formed by so-called outsert molding, so that the distal end portion and the proximal end portion of the leaf spring members 15 and 16 are the lenses. The bobbin main body 19 and the upper fixed block 9 are embedded and connected to each other. The base end portions of these leaf spring members 15 and 16 are connected to the upper fixed block 9.
And protrudes rearward from the rear end face as connection terminals. The tip portions of these leaf spring members 15 and 16 are
The rear end portion is embedded in the lens bobbin main body 19 and is connected to a terminal plate whose rear end is projected rearward from the rear end surface of the lens bobbin main body 19 as a connection terminal 31.

A bobbin support frame 14 is attached to the lower surface of the lens bobbin body 19. The bobbin supporting frame 14 is made of the same material as the lens bobbin main body 19 and is formed into a frame shape that supports both side portions of the lens bobbin main body 19. This bobbin support frame 1
4, a pair of positioning protrusions 33, 33 are provided on the upper surface of the lens protrusion 4, and the positioning protrusions 33, 33 position the lens bobbin main body portion 19 to the lens bobbin main body portion 19. It is adhered and fixed by. The bobbin support frame 14 has both side portions,
Via a pair of leaf spring members 10 and 11 which are elastic members,
It is supported by the lower fixed block 8 that constitutes the fixed portion.

The leaf spring members 10 and 11 are integrally formed in a thin and long plate shape with a metal material having an appropriate elasticity such as phosphor bronze. These bobbin support frames 14
And the lower fixed block 8 and the leaf spring members 10,
11 is connected by a so-called outsert molding in a state in which the front end side portion and the base end side portion of each of the leaf spring members 10 and 11 are buried inside the bobbin supporting frame 14 and the lower fixing block 8. ing. These leaf spring members 10, 1
A base end portion of the base 1 protrudes rearward from a rear end surface of the lower fixed block 8 as a connection terminal. Further, the tip end portions of the leaf spring members 10 and 11 are embedded in the bobbin supporting frame 14 and the rear end portions thereof are connected to a terminal plate which is projected rearward from the rear end surface of the bobbin supporting frame 14 as a connecting terminal 31. It is set up.

The lower fixed block 8 and the upper fixed block 9 are fixedly arranged on the base 1 via a fixing plate 6. That is, the lower fixing block 8 is bonded and fixed on the fixing plate 6 with an adhesive, and the upper fixing block 9 is bonded and fixed on the lower fixing block 8 with an adhesive. The fixing plate 6 is adhered to the base 1 with an adhesive (or
The fixing portion is configured by being fixed (by soldering). Positioning projections 7, 7 for positioning the lower fixed block 8 are provided on both sides of the fixed plate 6 so as to project. A positioning protrusion 32 for positioning the upper fixed block 9 is provided on the upper surface of the lower fixed block 8.

The leaf spring members 10, 11, 15, 16 described above
2 and 5, each has a linear portion and crank portions 12, 13, 17, and 18, and is attached to the fixed portion including the fixed blocks 8 and 9 on the base end side, The tip side is attached to the lens bobbin main body 19 or the bobbin supporting frame 14. The leaf spring members 10, 11, 15 and 16 have the linear portions substantially parallel to each other and support the lens bobbin main body 19 and the bobbin support frame 14 so as to be displaceable with respect to the fixed portion. . And the crank parts 12, 13, 17, 1
Numeral 8 is provided at the base end side portion of each of the leaf spring members 10, 11, 15 and 16 mentioned above, and is formed with two 90 ° bending portions in opposite directions. These leaf spring members 1
In 0, 11, 15, and 16, the base end portion of the linear portion and the tip end portions of the crank portions 12, 13, 17, and 18 are connected to each other via a wide connecting plate portion 27. Further, in these leaf spring members 10, 11, 15 and 16, a displacement restricting piece portion 28 is provided so as to surround both sides of the crank end portions 12, 13, 17 and 18 on the base end side and the middle portion. The edges of the displacement regulating piece 28 and the cranks 12, 13, 17, 18 are separated from each other in a natural state where the cranks 12, 13, 17, 18 are not displaced. Further, each of the crank portions 12, 13, 17, 18 is formed thinner (narrower) than the linear portion in each of the leaf spring members 10, 11, 15, 16.

A coil bobbin 22 is attached to the bobbin supporting frame 14 and the lens bobbin body 19. The coil bobbin 22 is formed in the shape of a hollow quadrangular prism having upper and lower sides opened. The coil bobbin 22 is fitted into a through hole provided in the lens bobbin main body 19 and substantially the center of the bobbin supporting frame 14, and a pair of protrusions are provided on the upper surface of the bobbin supporting frame 14. It is positioned by the positioning projections 29, 29, and is fixed to the lens bobbin main body 19 and the bobbin supporting frame 14 with an adhesive.

A focus coil 23 and tracking coils 24, 24 are attached to the coil bobbin 22. The focus coil 23 is wound around the side surface (outer peripheral portion) of the coil bobbin 22, and the central axis of the coil is parallel to the optical axis of the objective lens 21. The tracking coils 24, 24 are wound around the tracking coil bobbins 25, 25, respectively. The tracking coil bobbins 25, 25 are mounted on the coil bobbin 22 by being mounted on the front end surface of the coil bobbin 22. These tracking coils 24, 24 have their central axes parallel to each other, and have their central axes parallel to the linear portions of the leaf spring members 10, 11, 15, 16 and the central axes thereof. 21 is a direction orthogonal to the optical axis.

The lead wires at the beginning and end of winding of the coils 23, 24, 24 are provided with four terminal rods 30, 30, 30, 30 projecting from the rear side of the coil bobbin 22.
Connected corresponding to. And these terminal rods 3
0, 30, 30, 30 are the lens bobbin main body 19
The connection terminals 31, 31, 3 protruding rearward from the rear end surface of the lens bobbin main body 19 and the bobbin supporting frame 14 of the terminal plate embedded in the bobbin supporting frame 14 and in the bobbin supporting frame 14.
1, 31 are connected by soldering.

The lens bobbin main body 19, the bobbin supporting frame 14, and the coil bobbin 22 constitute a lens bobbin of this objective lens driving device.

A pair of front and rear yokes 2 and 3 which serve as stopper members for the lens bobbin are integrally provided on the base 1 so as to stand upright on the base 1. The base portion 1 and the yokes 2 and 3 are made of a magnetic material (high magnetic permeability material) such as iron. As shown in FIGS. 2 and 3, the rear yoke 2 is inserted into the hollow portion of the coil bobbin 22 from below. A magnet 4 serving as a stopper member for the lens bobbin is attached to the front surface of the rear yoke 2 by adhesion using an adhesive. As shown in FIGS. 2 and 3, the front yoke 3 is inserted into the bobbin support frame 14 and the through hole in the central portion of the lens bobbin main body 19 from the lower side, and the front side of the coil bobbin 22, that is, , Located on the front side of each of the tracking coils 24, 24. The upper ends of the yokes 2 and 3 are connected to each other via a connecting plate 5. Like the yokes 2 and 3, the continuous plate 5 is made of a magnetic material (high magnetic permeability material) such as iron.

The distance between the rear edge of the through hole at the center of the lens bobbin main body 19 and the bobbin supporting frame 14 and the front surface of the front yoke 3 is the initial position of the lens bobbin main body 19. When in the (neutral position), FIG.
Also, as indicated by an arrow a in FIG. 3, the predetermined distance is, for example, about 0.4 mm. In addition, the front yoke 3
And the tracking coil bobbins 25, 2 described above.
The distance from the front surface of the lens bobbin 5 is
When 9 is in the initial position (neutral position), as shown by an arrow b in FIGS. 2 and 3, the predetermined distance is, for example, about 0.4 mm. Further, the distance between the front inner wall portion of the hollow portion of the coil bobbin 22 and the front surface portion of the magnet 4 is as shown in FIGS. 2 and 3 when the lens bobbin main body 19 is in the initial position (neutral position). As indicated by the middle arrow c, the predetermined distance is, for example, about 0.4 mm. The distance between the rear surface portion of the rear yoke 2 and the rear inner wall portion of the hollow portion of the coil bobbin 22 when the lens bobbin main body portion 19 is in the initial position (neutral position) is as shown in FIG. Further, as indicated by an arrow d in FIG. 3, the predetermined distance is, for example, about 0.4 mm.

In this objective lens driving device, the objective lens 21 has the optical axis direction of the objective lens 21 (that is, the focus direction shown by the arrow F in FIG. 1) and the tangent line of the optical axis and the recording track of the optical disc. Is supported so as to be movable in two directions orthogonal to (i.e., the tracking direction shown by the arrow T in FIG. 1), and the electromagnetic force generated between the coils 23, 24, 24 and the magnet 4 causes Operated in two directions. The recording track is formed in a substantially concentric spiral shape on the optical disc on the optical disc. In this optical disc, an information signal is written along the recording track.

The objective lens driving device moves the objective lens 21 in order to cause the objective lens 21 to follow the displacement of the optical disk. That is, the optical pickup device always focuses the light beam transmitted through the objective lens 21 at the position where the information signal is written on the signal recording layer of the optical disk.

This optical pickup device faces the optical disk held on the disk table in the chucking hole and rotated by the spindle motor, and is moved in the radial direction of the optical disk to move the optical disk. As a relative position with respect to, the information signal is written in or read from the recording track while being moved along the recording track. Therefore, in this optical pickup device, the focusing position of the laser light flux by the objective lens 21 is
It is necessary to follow the displacement of the position of the recording track due to the surface runout and eccentricity of the optical disc. Therefore, the objective lens driving device moves the objective lens 21 in the focus direction and the tracking direction.

In this objective lens driving device, the focus coil 23 is provided with a connection terminal projecting from the rear end surface of each of the fixed blocks 8 and 9 and each of the leaf spring members 1.
When the focus drive current is supplied through 0, 11, 15, 16 and each of the terminal plates, the lens bobbin main body 19 moves in the focus direction as indicated by an arrow F in FIGS. 1 and 4. Is moved to. Further, in this objective lens driving device, the tracking coils 24, 24 are provided with connection terminals protruding from the rear end surfaces of the fixed blocks 8, 9 and the leaf spring members 10, 1 respectively.
By supplying a tracking drive current through 1, 15, 16 and each of the terminal boards, the lens bobbin body 19 moves in the tracking direction as shown by an arrow T in FIGS. 1 and 4. Operated.

In this objective lens driving device, the focus driving current and the tracking driving current are error signals (focus error signal and focus error signal) indicating the amount of deviation between the recording position of the laser beam focused by the objective lens 21 and the recording track. Tracking error signal). Therefore, this objective lens driving device is
A periodic moving operation of the objective lens 21 is performed in synchronization with the rotation cycle of the optical disk.

The laser beam focused on the signal recording layer is reflected in the signal recording layer by modulating the reflection intensity or the polarization direction according to the information signal written in the signal recording layer. It The reflected light flux reflected by the signal recording layer returns to the objective lens 21, passes through the objective lens 21, and is received by a photodetector (not shown) arranged in the frame. This photodetector has a plurality of photodetectors.
The read signal of the information signal from the optical disc, the focus error signal and the tracking error signal are generated from the output signal from the photodetector.

By the way, in this objective lens driving device, each of the leaf spring members 10, 11, 15 and 16 is arranged as shown in FIG.
Further, as shown by an arrow G in FIG. 6, when an impact is applied to the lens bobbin in a direction that produces an inertial force in a direction toward the base end side of each of the leaf spring members 10, 11, 15 and 16, the lens bobbin is The body portion 19 is the front yoke 3 described above.
To the magnet 4, or until the coil bobbin 22 comes into contact with the magnet 4 (that is, the moving distance of the lens bobbin is the distance between the lens bobbin main body 19 and the front yoke 3 or the coil bobbin 22 and Until the distance between the magnets 4 is reached), as shown in FIGS. 4 and 6, the crank portions 12, 13, 17, 18 are elastically displaced. Each of the above crank parts 1
The displacements of 2, 13, 17, and 18 are caused by the respective crank parts 1
The displacement occurs in such a manner that the portions of 2, 13, 17 and 18 in the direction orthogonal to the straight line portion are inclined.

The leaf spring members 10, 11, 15, 16 described above
In the above, each of the crank parts 12, 13, 17, 18
Are formed thinner (narrower) than the straight line portion.
Therefore, when the above-mentioned impact is applied, the crank portions 12, 13, 17, 18 are always displaced before the linear portion, thereby preventing the plastic deformation of the linear portion. . After the impact is applied, each of the crank parts 12, 13, 17, 18
Elastically returns to the initial state.

In the above-described embodiment, the crank portions 12, 13, 17, 18 are provided on the base end side of the leaf spring members 10, 11, 15, 16 respectively. However, in the objective lens driving device according to the present invention, each of the crank portions 12, 13, 17, 18
May be provided on the tip side or in the middle of each of the leaf spring members 10, 11, 15, and 16.

[0039]

As described above, in the objective lens driving device according to the present invention, the tip end side is attached to the lens bobbin to which the objective lens is attached and the base end side is attached to the fixed portion. The elastic member that displaceably supports the lens bobbin with respect to the fixed portion by being driven by the lens bobbin when the impact is applied in a direction that generates an inertial force in a direction toward the proximal end side of the elastic member. It is supposed that the crank bobbin is displaced until the lens bobbin comes into contact with a stopper member provided on the fixed portion.

Therefore, in this objective lens driving device, the plastic deformation of the linear portion of the elastic member when the lens bobbin is subjected to the impact in the direction of generating the inertial force in the direction toward the base end side of the elastic member. It is prevented.

That is, according to the present invention, even when vibration or impact is applied from the outside, the elastic member for supporting the objective lens is prevented from being plastically deformed, and a good information signal is written to the optical recording medium. Further, it is possible to provide an objective lens driving device which is designed so as not to disturb reading.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of an objective lens driving device according to the present invention.

FIG. 2 is a partially cutaway plan view showing the configuration of the objective lens driving device.

FIG. 3 is a side view showing the structure of the objective lens driving device with a part thereof cut away.

FIG. 4 is a partially cutaway plan view showing a state in which an impact is applied in the objective lens driving device.

FIG. 5 is an enlarged plan view of an essential part showing the configuration of the essential part of the objective lens driving device.

FIG. 6 is an enlarged plan view of an essential part showing a state where an impact is applied to the essential part of the objective lens driving device.

[Explanation of symbols]

1 base part, 2 rear yoke, 3 front yoke, 4 magnets, 10, 11, 15, 16 leaf spring member, 1
2, 13, 17, 18 Crank part, 8 Lower fixed block, 9 Upper fixed block, 19 Lens bobbin, 2
1 objective lens, 22 coil bobbin, 23 focus coil, 24 tracking coil

Claims (3)

[Claims] 1. A lens bobbin to which an objective lens is attached, a linear portion and a crank portion, a base end side is attached to a fixed portion, and a tip end side is attached to the lens bobbin, whereby the lens bobbin is attached. An elastic member that is displaceably supported with respect to the fixed portion, and the elastic member is configured such that when the lens bobbin receives an impact in a direction that generates an inertial force in a direction toward the base end side of the elastic member, An objective lens driving device configured to be displaced in the crank portion until the bobbin comes into contact with a stopper member provided in the fixed portion. 2. The objective lens driving device according to claim 1, wherein the crank portion is provided on the base end side of the elastic member. 3. The objective lens driving device according to claim 1, wherein the crank portion is formed to be thinner than the linear portion.