JPH0836768A - Objective lens driver - Google Patents

Abstract

PURPOSE:To reduce the entire apparatus in size and to suppress and out-of-axis aberration by forming a finite optical system by using a finite objective lens. CONSTITUTION:The objective lens driver comprises a finite objective lens 11, a bobbin member 14 assembled with the lens 11 and with a focusing coil 22 and a tracking coil 23, and a base member 17 in which a yoke 24 to which a magnet 28 is connected, is integrally formed rising. The driver also comprises an elastic member 15 in which a bobbin support member 16 fixed to the member 17 and a base end 32 are fixed to the member 17 and an engaging part 34 is fixed to the member 14 to elastically displacebly support the member 14 in focusing and tracking directions. The lens 11 is tilted, when regulating in the tracking direction due to a tracking error signal, in the tracking direction for correcting an abaxial aberration generated by the deviation of the optical axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in a recording / reproducing apparatus for a disc-shaped optical recording medium and drives an objective lens at least in a focusing direction parallel to the optical axis of the objective lens and in a tracking direction orthogonal to the optical axis. The present invention relates to an objective lens driving device that is displaced.

[0002]

2. Description of the Related Art An optical disk recording / reproducing apparatus using a disk-shaped optical recording medium (hereinafter collectively referred to as an optical disk) such as an optical disk and a magneto-optical disk as a recording medium reproduces an information signal recorded on an optical disk or An optical pickup device for recording a signal is provided. This optical pickup device is an optical device such as a beam splitter that separates a semiconductor laser as a light source that emits a laser beam applied to an information signal recording surface of an optical disc and a reflected laser beam reflected from the information signal recording surface of the optical disc. An optical system block composed of parts, and an objective lens driving device that adjusts the objective lens to cause the beam spot of the laser light emitted from the semiconductor laser to follow the recording track formed on the information signal recording surface of the optical disc. There is.

The optical system block is provided with a semiconductor laser and a laser beam emitting surface of the semiconductor laser.
A grating for the spot method, a beam splitter, a Wollaston prism that is joined to the side surface of the beam splitter and guides the separated reflected laser light, a multilens or a photodetector that shapes the reflected laser light that has passed through this Wollaston prism, etc. It is composed of a member such as a photodetector. This optical system block is an infinite specification type in which a collimator lens is arranged in the optical path to collimate the laser light emitted from the semiconductor laser and guide it to the objective lens. It is classified into a finite specification type in which the emitted laser light is directly guided to the objective lens.

In the infinite specification type optical system, even if the objective lens is adjusted in the focusing direction or the tracking direction by the objective lens driving device, the incident condition of the laser beam on the objective lens does not change, and the occurrence of aberration is small. It has such characteristics. On the other hand, the finite specification optical system
Since the collimator lens is not provided, the device can be downsized.

Further, since the objective lens driving device adjusts the objective lens within the range of 2 mm in the focusing direction and 0.8 mm in the tracking direction, the electromagnetic force generated by the control current supplied to the coil arranged in the magnetic field is used. An orthogonal biaxial actuator mechanism is provided.

As the orthogonal biaxial actuator mechanism that has been put into practical use, a spring support structure method that can obtain a smooth drive characteristic without friction, an assembly accuracy is easy to obtain, and an objective lens tilt posture maintaining characteristic is excellent. Shaft rotation sliding structure system is provided. Further, the orthogonal biaxial actuator mechanism of the spring support structure type is divided into a moving coil type and a moving magnet type, and the orthogonal biaxial actuator mechanism of the axial rotation sliding structure type is divided into an inner optical path type and an outer optical path type. To be

On the other hand, in a spring support structure type orthogonal biaxial actuator mechanism, a hinge structure, a wire structure or a leaf spring structure is known as a structure of an elastic member for holding an objective lens. The orthogonal biaxial actuator mechanism of the leaf spring type structure is extremely effective for downsizing the objective lens driving device.

In the objective lens driving device provided with such an orthogonal biaxial actuator mechanism of the leaf spring type structure, since the objective lens is supported by the four elastic members in the upper, lower, left and right directions so as to be elastically displaceable, the load is restrained. The state of the. Therefore, the elastic member may cause rolling without moving the objective lens parallel to the information recording surface of the optical disc when the objective lens is adjusted in the tracking direction.

The rolling of the elastic member causes the optical axis of the objective lens to be tilted, which causes aberrations to distort the reproduced information signal and to superimpose an offset on the tracking control signal. Cause problems. Further, the elastic member may cause a rolling resonance phenomenon at several tens Hz when the objective lens driving device is moved by the feeding device in the radial direction of the optical disc.

Therefore, in the prior art, the orthogonal 2 of the leaf spring type structure is used.
In designing an objective lens driving device equipped with an axial actuator mechanism, in order to prevent the rolling or rolling resonance phenomenon of the elastic member described above when adjusting the objective lens in the tracking direction, "a moving part including an objective lens The basic condition of the design was to make the center of gravity coincide with the center of the driving force that adjusts the movable part in the focusing direction and the tracking direction.

[0011]

In the optical pickup device, the deviation between the defined track of the optical disk and the position of the beam spot of the laser light emitted through the objective lens is detected by the photodetector of the optical system block. Is applied to the tracking coil of the objective lens driving device as a tracking error signal. As a result, the objective lens driving device adjusts the objective lens in the direction orthogonal to the optical axis, and causes the focus position of the objective lens to follow the specified track of the optical disc.

FIG. 18 shows an optical pickup device
It is the figure which showed typically the adjustment operation | movement of the objective lens 2 based on a tracking error signal. The objective lens drive is
If the specified track of the optical disc 1 moves from A to B in the radial direction by Δx for some reason, the beam spot position of the laser beam irradiated through the objective lens 2 is changed from A to B based on the tracking error signal. The objective lens 2 is adjusted by Δy in the tracking direction so as to move to B. On the other hand, the position of the semiconductor laser 3 is constant regardless of the adjustment operation of the objective lens 2 in the tracking direction. Therefore, this semiconductor laser 3
The laser light emitted from is incident on the objective lens 2 at an angle θ _A.

In a miniaturized optical pickup device, a finite specification type optical system is generally adopted, and the objective lens 2 is used.
A finite objective lens is used for. For this reason, the beam spot of the laser beam applied to the information signal recording surface of the optical disc 1 through the objective lens 2 is incident on the objective lens 2 at an angle θ _{A, so} that it contains off-axis aberration. Like The beam spot including the off-axis aberration causes a problem in that the reproduced waveform is distorted and the performance such as a signal conversion point position error (jitter) or an error rate is deteriorated.

As described above, in the objective lens driving device, conventionally, the design has been made on the basic condition that the rolling phenomenon does not occur in the objective lens 2 exclusively. The countermeasure is to measure the semiconductor laser 3 by the objective lens 2.
The purpose is to correctly focus the laser beam emitted from the optical disc 1 on the information recording surface of the optical disc 1, and no consideration is given to the measures against the off-axis aberration due to the displacement of the objective lens 2 with respect to the semiconductor laser 3 described above. It is not an exaggeration to say.

Therefore, according to the present invention, when the objective lens is adjusted in the tracking direction within a range that does not interfere with the basic operation of the objective lens driving device, the objective lens driving device is tilted in the tracking direction so that the axis of movement is reduced. The object of the present invention is to provide an objective lens driving device that suppresses external aberrations to improve the reproduction accuracy of an information signal and improves the optical system block to reduce the size of the pickup device.

[0016]

An objective lens driving device according to the present invention, which has achieved this object, is equipped with a finite objective lens and generates a magnetic driving force acting in a focusing direction parallel to the optical axis of the finite objective lens. A focusing coil and a bobbin member to which a tracking coil that generates a magnetic driving force that acts in a tracking direction orthogonal to the optical axis of the finite objective lens are assembled, and free ends are vertically separated from both side surfaces of the bobbin member. The four elastic members, which are formed by spring materials that support the bobbin member elastically displaceably in the focusing direction and the tracking direction by being fitted, and the magnet, are joined and penetrated inside the focusing coil. Position so that the first yoke piece and the tracking coil face each other. A second yoke piece and a base member to which a bobbin supporting member that supports the base end portion of the elastic member is fixed, and a finite objective lens that moves the finite objective lens in conjunction with the displacement operation of the bobbin member in the tracking direction. And an objective lens tilting means for tilting the lens in the tracking direction for correcting off-axis aberrations caused by the axis shift.

In the objective lens driving device according to the present invention, the finite objective lens is assembled and the focusing coil for generating a magnetic driving force acting in the focusing direction parallel to the optical axis of the finite objective lens and the light of the finite objective lens. A bobbin member to which a tracking coil that generates a magnetic driving force that acts in a tracking direction orthogonal to the axis is assembled, and the free ends are vertically and separately fitted to both side surfaces of the bobbin member. Four elastic members formed of a spring material for elastically displacing the magnet in the focusing direction and the tracking direction, a first yoke piece and a tracking coil to which a magnet is joined and which penetrates inside the focusing coil. A second yoke piece positioned so as to face each other is formed. And it comprises a base member bobbin supporting member is fixed to support the base end portion of the elastic member. Then, in the objective lens driving device, the center of rigidity of the four elastic members is aligned with the center of gravity of the movable portion formed by the bobbin member and the members assembled to the bobbin member, and is generated by the tracking coil. The center of the magnetic driving force is located above the focusing direction.

Further, in the objective lens driving device according to the present invention, the four elastic members are rigid in the tracking direction with respect to the elastic members located on the lower side of both side surface portions of the bobbin member on the upper side. And the center of gravity of the movable part formed by the bobbin member and each member assembled to the bobbin member corresponding to the rigidity center of these elastic members is located on the lower side in the focusing direction. Composed.

Further, in the objective lens driving device according to the present invention, the position of the center of gravity of the movable part is adjusted in the focusing direction by adjusting the mounting position of the focusing coil and the tracking coil mounted on the bobbin member to the lower side in the focusing direction. Is configured to move to the lower side of.

[0020]

According to the objective lens driving device of the present invention configured as described above, when the driving current corresponding to the tracking error signal is supplied to the tracking coil assembled to the bobbin member, the magnetic driving in the tracking direction is performed. A force is generated to elastically displace the elastic member, and the finite objective lens mounted on the bobbin member is adjusted in the tracking direction. When the finite objective lens is adjusted in the tracking direction, the objective lens tilting means tilts the finite objective lens in the tracking direction to reduce the incident angle of the laser light emitted from the semiconductor laser 3 and to obtain the finite objective. The off-axis aberration of the beam spot of the laser beam applied to the information signal recording surface of the optical disc through the lens is suppressed.

Further, according to the objective lens driving device of the present invention, the center of rigidity of each elastic member and the center of gravity of the movable portion are made to coincide with each other, and the center of the magnetic driving force is positioned above the focusing direction. Thus, when the finite objective lens is adjusted in the tracking direction, the elastic member rolls along with the elastic displacement in the tracking direction to tilt the finite objective lens in the tracking direction. Therefore, the laser beam emitted from the semiconductor laser 3 is incident on the finite objective lens with a small incident angle, and the off-axis aberration of the beam spot of the laser beam applied to the information signal recording surface of the optical disc is suppressed. To be done.

Further, according to the objective lens driving device of the present invention, the elastic member disposed on the lower side is configured to increase the rigidity in the tracking direction, and the center of gravity of the movable portion is set to the lower side in the focusing direction. When the finite objective lens is adjusted in the tracking direction, the elastic member rolls along with the elastic displacement in the tracking direction to tilt the finite objective lens in the tracking direction.

Furthermore, according to the objective lens driving device of the present invention, the center of gravity of the movable portion is moved to the lower side in the focusing direction by moving the focusing coil and the tracking coil assembled to the bobbin member downward. It can be easily moved.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. Example Objective lens driving device 10
Is provided in the finite optical type optical pickup device 50 together with each member constituting the finite optical system block 40.
As shown in FIGS. 2 to 4, the objective lens driving device 10 includes a finite objective lens 11, an objective lens holder 12 in which the finite objective lens 11 is assembled, an objective lens holder 12 and a magnetic circuit unit 13. A bobbin member 14 in which the respective members described later are combined, four elastic members 15 (15A to 15D), a bobbin supporting member 16 that supports the base end portions of these elastic members 15, and a base formed of a magnetic material. The member 17 is configured as a main constituent member. In addition, in the following description, like the elastic member 15 described above, a member including a plurality of members and the like will be denoted by a representative symbol unless it is necessary to individually describe each member.

The bobbin member 14 is made of a synthetic resin material and comprises a holder portion 18 to which the above-mentioned objective lens holder 12 is assembled, and a magnetic circuit component assembly portion 19 to which the respective constituent members of the magnetic circuit portion 13 are combined. Has been done. The holder portion 18 is formed as a thin tubular portion as a whole in which an objective lens mounting hole 20 into which an objective lens holder 12 in which a finite objective lens 11 is combined is fitted is formed. In addition, a plurality of holding pieces 21 (21 </ b> A to 21 </ b> A) for holding the outer peripheral surface of the finite objective lens 11 fitted in the objective lens mounting hole 20 are provided in the holder portion 18.
C) is integrally formed.

Magnetic circuit component assembly portion 1 of bobbin member 14
Reference numeral 9 denotes a substantially convex opening, and a focusing coil 22 for generating a driving force for driving and displacing the finite objective lens 11 in a direction parallel to the optical axis, and the finite objective lens 11 are orthogonal to the optical axis. Of the pair of tracking coils 23 (23A, 2A, 2
3B) and the first yoke piece 24 and the second yoke piece 25 are assembled. The focusing coil 22 is located on the side of the slightly wider opening opposite to the objective lens mounting hole 20 and is assembled to the magnetic circuit component assembly portion 19.

Horizontal fittings into which fitting portions 34 (34A to 34D) of elastic members 15A to 15D, which will be described later, are inserted into both side surfaces of the bobbin member 14 corresponding to the magnetic circuit component mounting portion 19. Compound slit 26
(26A to 26D) are provided separately in the vertical direction. Therefore, the bobbin member 14 is supported by these elastic members 20 so as to be elastically displaceable in the vertical direction, that is, the focusing direction and the horizontal direction, that is, the tracking direction.

The focusing coil 22 is formed in a rectangular tube shape having a diameter substantially the same as the opening dimension of the coil assembling opening portion 27 constituting the magnetic circuit component assembling portion 19, and the coil assembling opening portion 27 is formed. Are fitted and combined. Further, the focusing coil 22 is assembled into the coil assembly opening 27, and then the adhesive is filled between the outer peripheral surface and the inner wall of the opening, whereby the bobbin member 1 is formed.
It is firmly fixed to 4. Further, the focusing coil 22 is configured so that the winding direction of the coil is parallel to the optical axis of the finite objective lens 11 when assembled in the coil assembly opening 27.

The pair of tracking coils 23 each have a thin rectangular frame shape, and are arranged between one side surface portion of the focusing coil 22 and the finite objective lens 11 so that one side surface of each of the tracking coils 23 is formed. The parts are overlapped with each other, and the parts are fitted and assembled in the coil assembly opening 27 that constitutes the magnetic circuit component assembly part 19. These tracking coils 23 are installed in the coil assembly opening 2
After assembling to 7, the focusing coil 22 is firmly fixed to one side surface of the focusing coil 22 with an adhesive. Further, these tracking coils 23 are configured to have a linear portion parallel to the optical axis of the finite objective lens 11 at least on opposite sides when assembled to the magnetic circuit component assembly portion 19.

Although the detailed shape of the base member 17 is omitted, the base member 17 is made of a material having a high magnetic permeability, such as silicon steel, and is formed into an approximately H-shape. The yoke piece 24 and the second yoke piece 25 are integrally formed so as to face each other in parallel.

The first yoke piece 24 penetrates the center hole of the focusing coil 22 assembled in the magnetic circuit component assembly portion 19. In addition, the second yoke piece 25,
It faces the tracking coil 23 and penetrates the magnetic circuit component assembly portion 19. First yoke piece 24 and second
A slightly thick plate-shaped magnet 28 (28A, 28B) is firmly attached and fixed to each of the yoke pieces 25 on opposite sides by using an adhesive or the like. The tip portions of the first yoke piece 24 and the second yoke piece 25 have
As shown by the chain line in FIG. 11, a yoke plate 29 made of a magnetic material is combined.

Therefore, the magnetic circuit section 13 includes the above-mentioned base member 17, the first yoke piece 24 and the second yoke piece 25 integrally formed on the base member 17, and these yoke pieces 24, It is composed of a magnet 28 and a yoke plate 29 attached to 25. The focusing coil 22 and the tracking coil 23 are located in the magnetic circuit part 13 so as to cross the magnetic field of the magnetic circuit part 13 and are assembled to the magnetic circuit part assembly part 19. Further, the supply of the current to the focusing coil 22 and the tracking coil 23 is as described below.
This is performed using the elastic member 15.

The bobbin supporting member 16 includes the first yoke piece 2
It is located on the opposite side of the fourth yoke piece 25 and the second yoke piece 25 and is attached to the base member 17 so as to straddle the H-shaped central opening portion. That is, the bobbin supporting member 16 is formed in a block shape as a whole, and an inverted U-shaped optical path concave portion 30 forming an optical path of the laser light emitted from the semiconductor laser is formed on the bottom surface portion, and both side surface portions are formed. The horizontal fitting slits 31 (31A to 31D) into which the base ends 32 of the elastic members 15A to 15D that support the bobbin member 14 are respectively inserted are provided separately in the vertical direction.

The elastic members 15 are members each formed by punching out a thin spring plate material, and the bobbin supporting member 16 is provided.
Elastic member 1 which is vertically mounted on the left side surface of the vehicle
5A and 15B, and elastic members 15C and 15D that are vertically assembled on the right side surface portion and are assembled.
These elastic members 15 are symmetrical with each other and are mounted on the same side surface portion.
5B and the elastic members 15C and 15D have the same shape.

As shown in FIG. 5, the elastic member 15 has a narrow rectangular base end portion 32 (32A to 32D) to be inserted into the fitting slits 31 provided on both side portions of the bobbin supporting member 16, and a narrow width. Elastically deforming portion 33 (33A to 33)
D) and the fitting portion 34 having a substantially rectangular shape to be inserted into the fitting slits 26 provided on both side surfaces of the bobbin member 14, respectively.
(34A to 34D). Further, these elastic members 15 serve as the bobbin supporting member 1 as described later.
6, a part of the base end portion 32 protruding from the outer peripheral surface of the bobbin supporting member 16 is configured as a signal line connecting portion 35, and one end side of the fitting portion 34 is elastically deformed. The coil connecting piece 36 (3
6A to 36D) are integrally formed. The coil connecting piece 36 is provided with a positioning hole 37 corresponding to a hemispherical positioning dowel 38 formed on the upper and lower surfaces of the bobbin member 14.

The elastic member 15 is supported by the bobbin supporting member 16 in a cantilever state by inserting and fixing the base end portions 32 into the fitting slits 31 provided on both side surfaces of the bobbin supporting member 16, respectively. It Then, the elastic member 15 is fixed by inserting the fitting portions 34 on the free end side into the fitting slits 26 provided on both side surfaces of the bobbin member 14 and fixing the bobbin member 14 in the vertical direction and the horizontal direction. It is supported so that it can be elastically displaced.

The elastic member 15 supports the bobbin member 14 on the bobbin supporting member 16 so as to be elastically displaceable.
The positioning hole 37 of the coil connecting piece 35 is relatively engaged with the positioning dowel 38 of the bobbin member 14 in a state of being mounted between these members. Coil connection piece 3
The coil wires of the focusing coil 22 and the tracking coil 23 are connected to 6, respectively. A signal line connecting portion 35 of the base end portion 32 is connected to a signal line that connects the focusing coil 22 and the tracking coil 23 to a drive source that supplies a focus error signal or a drive current based on the tracking error signal. Therefore, the elastic member 15 also functions as a current supply line to the focusing coil 22 and the tracking coil 23.

The objective lens driving device 10 configured as described above is mounted on the holder 51 together with the finite optical system block 40 to form a finite optical type optical pickup device 50 as described later. The objective lens driving device 10 irradiates the laser light emitted from the semiconductor laser 41 of the finite optical system block 40 on the information signal recording surface of the optical disc 1 in the form of a beam spot through the finite objective lens 11, and at the same time, outputs the information signal. The reflected laser light from the recording surface is dispersed by the beam splitter 43 through the finite objective lens 11, and the difference component between the focusing direction and the tracking direction of the incident laser light and the reflected laser light is detected by the photodetector 46. The detected difference component between the focusing direction and the tracking direction is supplied to the focusing coil 22 and the tracking coil 23 as a focus error signal or a tracking error signal.

In the objective lens driving device 10, when the focusing coil 22 is supplied with a driving current according to the focus error signal, the current flowing through the focusing coil 22 and the magnetic flux from the magnet 28 constituting the magnetic circuit section 13 are detected. By this, a magnetic driving force for driving the bobbin member 14 in the focusing direction is generated. This magnetic driving force elastically displaces the elastic member 15 in the vertical direction,
The bobbin member 14, in other words, the finite objective lens 11 is adjusted in the focusing direction parallel to the optical axis to adjust the focusing of the laser light emitted from the semiconductor laser 41 with which the optical disc 1 is irradiated.

The objective lens driving device 10 includes a first tracking coil 23A or a second tracking coil 23.
When a drive current corresponding to the tracking error signal is supplied to B, the current flowing through the tracking coils 23A and 23B and the magnet 2 that constitutes the magnetic circuit unit 13 are supplied.
A magnetic driving force for driving the bobbin member 14 in the tracking direction is generated by the magnetic flux from 8. This magnetic driving force elastically displaces the elastic member 15 leftward or rightward, adjusts the bobbin member 16, in other words, the finite objective lens 11 in the tracking direction orthogonal to the optical axis, and causes the optical disc 1 to move. The tracking of the laser light emitted from the semiconductor laser 41 for irradiation is adjusted.

Next, the finite optical system block 40 will be described with reference to FIG. The finite optical system block 40 includes a semiconductor laser 41, a grating 42, and a beam splitter 43 arranged on the optical axis of the finite objective lens 11 assembled to the objective lens driving device 10, and an optical axis orthogonal to the optical axis of the beam splitter 43. The Wollaston prism 44 joined to the side surface of the
4 is composed of members such as a multi-lens 45 and an optical detector 46 including a photodetector and the like, which are arranged so that their optical axes coincide with each other. These optical components and photodetector 46
Are assembled in a holder 51 described later. As described above, the optical system block is not provided with the collimator lens for collimating the laser light emitted from the semiconductor laser 41, and is configured as a finite optical path.

In the figure, the finite objective lens 11
Although the semiconductor laser 41 and the semiconductor laser 41 are shown as being arranged on the same straight line, the semiconductor laser 4 is actually shown.
A reflection mirror, which bends the laser beam emitted from the laser beam No. 1 through the optical path recess 30 provided on the bobbin supporting member 16 by 90 ° and guides it to the finite objective lens 11, is arranged below the finite objective lens 11. ing. Further, the Wollaston prism 44 is an optical component provided for detecting a magneto-optical signal, and it goes without saying that it is not necessary in the case of a reproduction-only optical pickup device, and the beam splitter 43 is also an oblique plate. It can be replaced.

The laser light emitted from the semiconductor laser 41 is incident on the grating 42 for the three-spot method, which is located opposite to the laser light emission surface of the semiconductor laser 41, and further passes through the beam splitter 43 to be finite. It is incident on the objective lens 11. A beam spot of the laser beam is formed on a predetermined track of the information signal recording surface of the optical disc 1 by the finite objective lens 11, is reflected on the information signal recording surface, and then is incident on the finite objective lens 11 again. This reflected laser light is transmitted to the beam splitter 4
It is incident on the beam No. 3, is bent 90 °, and is split into the incident laser beam.

The reflected laser light dispersed by the beam splitter 43 passes through the Wollaston prism 44,
Photodetector 4 shaped by multi-lens 45
6 is received. Photodetector 46 that receives the reflected laser light
Generates a focusing error signal or a tracking error signal by an operation whose details are omitted, and supplies a driving current to the focusing coil 22 or the tracking coil 23 via a driving source to supply the objective lens driving device 10
Drive.

The objective lens driving device 10 and the finite optical system block 40 configured as described above are mounted on the holder 51. The holder 51, as shown in FIGS. 7 and 8,
Die cast or injection molding of synthetic resin material is performed to form a block body having a substantially rectangular shape as a whole. Holder 51
Is provided with a guide bearing portion 52 through which a feed guide shaft 61 arranged in the recording / reproducing apparatus 60 is penetrated on one side surface in the longitudinal direction, and a thread arranged in the recording / reproducing apparatus 60 on the other side surface. A feed screw portion 53 through which the feed screw shaft 62 is inserted is provided.

The recording / reproducing device 60 is provided with a disc rotation driving device 64 for rotating the optical disc 1 housed in the disc cartridge mounted in the cartridge mounting portion 63 formed in the main body of the device. This disk rotation drive device 64 has an optical disc 1 at the tip of a drive shaft 65.
And a disk table 66 that rotates together with the optical disk 1 is attached.

The recording / reproducing device 60 supports the above-mentioned feed guide shaft 61 and sled feed screw shaft 62, which drive the optical pickup device 40 in the radial direction of the optical disc 1, in parallel with each other. The feed guide shaft 61 and the thread feed screw shaft 62 constitute a drive mechanism of the optical pickup device 50 that rotationally drives the thread feed screw shaft 62, and allows the optical pickup device 50 to move in the radial direction of the optical disc 1. . In this state, the objective lens driving device 10
The elastic member 15 is extended in the tangential direction which is the tangential direction of the track formed on the information signal recording surface of the optical disc 1 and is arranged in the recording / reproducing device 60.

The optical pickup device 50 is fed in the direction of arrow A in FIG. 9 when the thread feed screw shaft 62 is rotationally driven by the pickup feed motor 67. In this case, the rotation of the pickup feed motor 67 is transmitted to the thread feed screw shaft 62 via the transmission gear mechanism 68.

As described above, in the objective lens driving device 10 of the embodiment, the finite objective lens 11 is provided by supplying the driving current according to the tracking error signal to the first tracking coil 23A or the second tracking coil 23B. It is adjusted in either the left or right direction of the tracking direction. In this case, the finite objective lens 11 is configured to simultaneously perform a rolling operation in the operated tracking direction during this adjustment operation.

That is, as shown in FIG. 1, when the finite objective lens 11 moves Δx with respect to the tracking direction, the finite objective lens 11 tilts with respect to the information signal recording surface of the optical disc 1 at an angle θ _L by the rolling operation. To do. Therefore, the laser light emitted from the semiconductor laser 41 enters the finite objective lens 11 at the incident angle θ _B. On the other hand, in the conventional objective lens driving device, the finite objective lens is configured so as not to cause a rolling operation and moves in a state parallel to the information signal recording surface of the optical disc 1, so that the semiconductor laser 4
The laser light emitted from No. 1 is incident at an incident angle θ _A.

As described above, the laser beam emitted from the semiconductor laser 41 has an incident angle θ _B with respect to the finite objective lens 11 as the finite objective lens 11 tilts, and θ _B = θ _A −θ. It will be _L and will be incident at a small angle. In the finite objective lens 11, the off-axis aberration increases as the incident angle of the laser light increases with respect to the optical axis. Therefore, in the objective lens driving device 10 of the embodiment, the generation of the off-axis aberration is gradually reduced to suppress the increase of the jitter or the deterioration of the error rate to reproduce the good information signal.

FIG. 10 is a diagram simulating the change in the amount of wavefront aberration with respect to the amount of movement of the finite objective lens, with the amount of change in wavefront aberration on the vertical axis and the amount of movement of the finite objective lens on the horizontal axis. In the figure, the solid line shows the case where the finite objective lens tilts in the moving direction, the dotted line shows the case where the finite objective lens does not tilt, and the dashed-dotted line shows the case where the finite objective lens tilts in the direction opposite to the moving direction. The respective cases are shown. As is clear from the figure, the wavefront aberration amount gradually increases as the finite objective lens moves.

This increasing amount of wavefront aberration is the largest when the finite objective lens tilts in the direction opposite to the moving direction, and the smallest when the finite objective lens tilts in the moving direction. Therefore, in the optical pickup device, when the finite objective lens is moved, as described above with reference to FIG. 1, the finite objective lens is tilted so that the incident angle of the laser light with respect to the optical axis. The off-axis aberration can be made smaller as the angle of incidence becomes smaller.

In FIG. 11, the vertical axis represents the magnitude of jitter and the horizontal axis represents the amount of movement of the finite objective lens, and the conventional optical pickup device in which the finite objective lens does not tilt and the finite objective lens tilts in the tracking direction. FIG. 6 is a diagram in which jitter is measured for an optical pickup device in which an optical pickup device and a finite objective lens tilt and move in a direction opposite to a tracking direction. In the figure, the solid line represents the case where the finite objective lens tilts with respect to the moving direction.
The dotted line shows the case where the finite objective lens does not tilt, and the alternate long and short dash line shows the case where the finite objective lens tilts in the direction opposite to the moving direction.

As described above, since the off-axis aberration increases as the finite objective lens moves, the jitter gradually increases as the amount of movement of the finite objective lens increases. This increasing jitter is the largest when the finite objective lens tilts in the direction opposite to the moving direction, and the smallest when the finite objective lens tilts in the moving direction. Therefore, in the optical pickup device, when the finite objective lens is moved, the finite objective lens is tilted with respect to the moving direction, whereby a stable device with less jitter can be configured.

As described above, the optical pickup device 50
Is effective to tilt the finite objective lens 11 at the same time when the objective lens driving device 10 is adjusted in the tracking direction. In this way, the tilting means for tilting the finite objective lens 11 during the adjustment operation in the tracking direction is achieved by positively utilizing the rolling phenomenon.

The objective lens driving device 10 is constructed so that the finite objective lens 11 is elastically displaceably supported by four elastic members 15A to 15D formed of a thin spring material. Then, the elastic member 15
The elastically deformable portion 33 is cantilevered by the bobbin supporting member 16 with the thickness direction (Z axis direction in FIG. 2) being the focusing direction and the width direction (Y axis direction in the same figure) being the tracking direction. There is.

Here, regarding the objective lens driving device 10, in the conventional design, "the longitudinal direction of the elastically deformable portion 33 of the movable portion which occurs during the driving operation in the tracking direction (see FIG. 2)
X-axis direction) resonance rotation about the state in (to X-axis rolling) suppressing, in the Z-axis direction position of the movable portion centroid (movable portion center of gravity) G _M, the working point the center of the magnetic driving force in the tracking direction (Point of action) Consists of F _T's
That was the basic condition. The basic condition is that the rigid body M in which the point F _T of the driving force is formed by the elastic member 15 is used.
According to the basic mechanical principle, the rolling phenomenon does not occur at the center of gravity position O.

FIG. 12 is a view for explaining the balance of moments when the elastic member 15 whose both ends are connected to the bobbin member 14 and the bobbin supporting member 16 is regarded as a fixed beam. The elastic member 15 regarded as a fixed beam is located at a position where the rigidity center G is displaced from the center of gravity T of the elastic member 15 having a total length L by Δa, and the acting force F is displaced from the center of gravity T by Δb. When working, the moment balance is represented by the following equation:

F / 2 (L / 2 + Δa) + F (Δb-Δ
a) = F / 2 (L / 2−Δa) As is clear from the moment balance equation, the elastic member 15 regarded as a fixed beam has the center of gravity T and the center of rigidity G coincident with each other, and the acting force F is When acting on the center of gravity T,
No rotation moment is generated.

Further, FIGS. 13A to 13C show four elastic members 15A to 15D arranged at equal positions.
It is the figure which demonstrated typically the balance state of the rigid body M supported by. The basic design conditions of the objective lens driving device described above are satisfied when the elastic members 15 have a sufficient spring action and elastically deform only in the vertical direction in the figure, as shown in FIG. If the driving force F is applied in conformity with the center of gravity O of M, the rolling resonance phenomenon does not occur in the rigid body M.

However, the elastic member 15 in the objective lens driving device 10 is constructed as a member which exerts a sufficient spring action against the rolling phenomenon corresponding to "torsion". Therefore, as shown in FIG.
In the rigid body M, when the operating point position of the driving force F is deviated from the center of gravity G of the rigid body M by Δc in the X-axis direction, the rolling phenomenon in the X-axis direction occurs from the above-described moment balance equation. It is clear to do.

On the other hand, as shown in FIG.
Is, for example, the left elastic member 15 that supports the rigid body M.
When A and 15B have stronger spring properties than the elastic members 15C and 15D on the right side, and the rigidity center G of the elastic member 15 is displaced from the center of gravity O of the rigid body M by Δd in the X-axis direction, the driving force F Even if the action point position of and the center of gravity O of the rigid body M are configured to coincide with each other, the rolling phenomenon in the X-axis direction similarly occurs.

Therefore, in the objective lens driving device 10, not only the position of the point of application of the driving force F but also the position of the rigidity center of the elastic member 15 causes the rolling phenomenon.

As described above, the objective lens driving device 10 of the embodiment positively utilizes the rolling phenomenon of the elastic member 15. 14A to 14C, in the direction in which the elastic member 15 is elastically displaced, that is, in the YZ plane, when viewed from infinity in the X-axis direction, which is the longitudinal direction, the center P of rigidity of the elastic member 15 and the movable portion. FIG. 6 is a diagram illustrating a positional relationship between a center of gravity G _M and an action point F _T of a magnetic driving force in a tracking direction. In the conventional objective lens driving device, as shown in FIG. (A), the point of action of the magnetic driving force from the base member side is positioned on the Z-axis F _T, the movable portion center of gravity G _M
And the rigidity center P are located respectively.

On the other hand, in the objective lens driving device 10 of the embodiment, the objective lens 1 is moved during the movement operation in the tracking direction.
Since 1 is configured to be tilted, the action point F _T of the magnetic driving force, the center of gravity G _{M of} the movable portion, and the rigidity center P are positioned as shown in FIG. 14B or FIG. As a result, the elastic member 15 is configured to generate a rolling phenomenon.

In this case, the objective lens driving device 10 is applied not only to the ideal type shown in FIG. 7B but also to the action point F of the magnetic driving force generated by the tracking coil 23 as shown in FIG. It is configured to allow the displacement of _T. That is, the objective lens driving device 10 includes the elastic member 1
The rigidity center P of 5 and the center of gravity G _{M of the} movable portion are located at the same position on the Z axis, and the point of action F _T of the magnetic driving force is located above the Z axis.

[0068] Here, in the conventional objective lens driving device illustrated in FIG. 14 (A), the center P of the rigidity of the elastic member 15, the movable portion centroid G _M and the point of application of the magnetic actuation force in the tracking direction F _T The specific numerical values are as follows: center of rigidity P = 1.60 mm, center of gravity of movable part G _M = 1.58 mm,
It is constituted by the point of action F _T = 1.60 mm of the magnetic driving force.

With respect to this conventional objective lens driving device,
In the example objective lens driving device 10 configured as shown in FIG. 6C, the focusing coil 22 and the tracking coil 23 are provided with the coil assembly opening 27 of the bobbin member 14.
Tracking direction (Z axis direction)
Has been moved by 0.1 mm. Accordingly, the specific values of the rigidity center P of the elastic member 15, the center of gravity G _{M of} the movable portion, and the point of action F _T of the magnetic driving force in the tracking direction are the center of rigidity P = 1.60 mm, the movable portion Center of gravity G _M
= 1.62 mm, point of action of magnetic driving force F _T = 1.60
configured as mm.

FIG. 15 shows the conventional objective lens driving device and the focusing coil 22 and the tracking coil 23 having the above-described structure in a tracking direction of 0.1.
Example: Objective lens driving device 10 assembled by shifting by mm
FIG. 6 is a diagram showing the positional relationship of each part on the XZ plane by specifically corresponding positions. In the figure, the position of each part of the objective lens driving device 10 of the embodiment is shown by a white circle, and the position of each part of the conventional objective lens driving device is shown by a black circle.

The conventional objective lens driving device and the example objective lens driving device 10 are located at the same position with respect to the positions K ₁ and K ₂ of the finite objective lens 11, and are located 2.7 mm from the base 17. . The positions of the centers of gravity G ₁ and G ₂ of the movable part are the positions K ₁ and K of the finite objective lens 11.
X from the position _{2 in the} X-axis direction at a position of 4.915 mm.
It is located at a position displaced by 0.1 mm in the axial direction. The working positions FT ₁ and FT ₂ of the driving force in the tracking direction are 4.950 mm in the X-axis direction with respect to the objective lens 11 and are at the same position, but in the Z-axis direction, the objective lens driving device 10 of the embodiment is 1.578 mm. The conventional objective lens driving device has a length of 1.500 mm.

The operating positions FF ₁ and FF ₂ of the driving force in the focusing direction are the same position at 5.400 mm in the X-axis direction with respect to the objective lens 11, and the driving force in the tracking direction is in the Z-axis direction. Similarly to the working positions FT ₁ and FT ₂ ,
0 is 1.578 mm, and the conventional objective lens driving device is 1.
It is 500 mm. The angles θ ₁ and θ ₂ of the optical axis of the finite objective lens 11 with respect to the optical path are 7.712 ° for the objective lens driving device 10 of the embodiment and 8.095 ° for the conventional objective lens driving device.

16 and 17 show an optical pickup device 50 having the embodiment objective lens driving device 10 configured as described above and an optical pickup device having a conventional objective lens driving device in the tracking direction ( Finite objective lens 1 from the point of action F _T of the magnetic driving force in the Y-axis direction
FIG. 3 is a diagram showing a change of a transfer function to 1 and an elastic member 15;
Assuming a uniform damping of 0.5% over the entire band of
It is a value calculated using FEM analysis data. 16 shows the change in the transfer function in the focusing direction versus the tracking direction, and FIG. 16 (A) shows the change in the transfer function of the optical pickup device 50 including the objective lens driving device 10 of the embodiment. Also, FIG. 3B shows changes in the transfer function of the optical pickup device including the conventional objective lens driving device.

FIG. 17 shows a rolling pair Y in the X-axis direction.
It is a calculation of the change in the transfer function of the axial rolling,
FIG. 3A shows changes in the transfer function of the optical pickup device 50 including the objective lens driving device 10 according to the embodiment, and
FIG. 1B shows changes in the transfer function of the optical pickup device including the conventional objective lens driving device. As is apparent from these drawings, the objective lens driving device 10 according to the embodiment
Is clearly effective in suppressing the resonance phenomenon with respect to the rolling phenomenon in the X-axis direction, and has the same effect in the low frequency band.

In the above-described objective lens driving device 10, if the position of the operating point F _T of the magnetic driving force in the tracking direction is further shifted to about 1.7 mm, the finite objective lens 11 will be quasi-static rolling. The tilting operation in the same direction as the tracking direction can be easily performed.

The above-described structure can be applied to a combination of elastic members 15. For example, the elastic member 15 includes two elastic members 15 located on the Z-axis side.
By forming A and 15B wider than the two elastic members 15C and 15D on the opposite side, the rigidity in the tracking direction can be increased, the rigidity center P can be reduced, and the weight balance of the movable portion can be improved. Be on the side.

[0077]

As described in detail above, according to the objective lens driving device of the present invention, the finite optical system is constructed by using the finite objective lens, so that the entire device can be downsized, and When the finite objective lens is adjusted in the tracking direction based on the tracking error signal, the finite objective lens tilts so that the incident angle of the laser beam emitted from the semiconductor laser is reduced. , Off-axis aberrations are suppressed. Therefore, the objective lens driving device realizes an optical system having a wide visual field characteristic by preventing the deterioration of the jitter and the error rate, and at the same time, the objective lens whose lateral magnification is close to “1” can be applied to downsize the optical path. Therefore, the device can be further downsized.

Further, according to the objective lens driving device of the present invention, the finite objective lens is adjusted in the tracking direction by adjusting the mounting position of the focusing coil and the tracking coil to the bobbin member or the position adjustment of the rigidity of the elastic member. Since the finite objective lens is configured to be tilted when it is moved, it can be realized without increasing the size of the device or changing the basic structure, and the adjustment and the like can be performed very easily.

[Brief description of drawings]

FIG. 1 is a basic operation diagram illustrating a basic operation of an objective lens driving device according to the present invention.

FIG. 2 is an overall perspective view of an objective lens driving device.

FIG. 3 is an overall plan view of the objective lens driving device.

FIG. 4 is an overall side view of the objective lens driving device.

FIG. 5 is a perspective view showing a partially cutaway elastic member provided in the objective lens driving device.

FIG. 6 is a schematic diagram illustrating a configuration of a finite optical system block of an optical pickup device including the objective lens driving device.

FIG. 7 is a perspective view of a main part showing the optical pickup device and a main part of a recording / reproducing device provided with the optical pickup device.

FIG. 8 is a bottom view of relevant parts for explaining a state in which the recording / reproducing apparatus includes the optical pickup device.

FIG. 9 is a main-portion plan view of a recording / reproducing apparatus including the optical pickup device.

FIG. 10 is a diagram showing changes in the amount of wavefront aberration depending on the amount of movement of the objective lens.

FIG. 11 is a diagram showing changes in jitter depending on the amount of movement of the objective lens.

FIG. 12 is an explanatory diagram of a moment balance state of a fixed beam.

FIG. 13 is a diagram for explaining a state of occurrence of a rolling phenomenon of a rigid body depending on the position of the center of gravity of the rigid body supported by an elastic member and the position where the acting force acts. FIG. 13A shows the position of the center of gravity of the rigid body and the point of action. Shows the case in which the force is shifted, FIG. 11B shows the case where the acting force is deviated, and FIG. 13C shows the case where the elastic force of the elastic member on one side is strong.

FIG. 14 is an explanatory view schematically showing the rigidity center position of the elastic member, the center of gravity of the movable portion, and the center position of the driving force in the tracking direction in the objective lens driving device in the tracking direction, respectively. Shows a conventional objective lens driving device, FIG. 1B shows an ideal type objective lens driving device, and FIG. 3C shows an example objective lens driving device.

FIG. 15 is an explanatory diagram schematically showing the position of the objective lens and the like of the objective lens driving device of the example and the conventional objective lens driving device.

FIG. 16 is a diagram in which a change in the transfer function of the magnetic driving force in the tracking direction to the objective lens in the focusing direction versus the tracking direction is calculated in the objective lens driving device of the example and the conventional objective lens driving device. FIG. 1A shows an objective lens driving device of the embodiment, and FIG. 1B shows a conventional objective lens driving device.

FIG. 17 is a diagram in which the change in the transfer function between the X-axis rolling and the Y-axis rolling of the magnetic driving force in the tracking direction to the objective lens is calculated in the example objective lens driving device and the conventional objective lens driving device. FIG. 1A shows an optical pickup device equipped with an objective lens driving device of the embodiment, and FIG. 1B shows an optical pickup device equipped with a conventional objective lens driving device.

FIG. 18 is a basic operation diagram illustrating the basic operation of the conventional objective lens driving device. 10 Objective Lens Driving Device 11 Finite Objective Lens 13 Magnetic Circuit Section 14 Bobbin Member 15 Elastic Member 16 Bobbin Support Member 17 Base Member 19 Magnetic Circuit Component Assembly Section 22 Focusing Coil 23 Tracking Coil 24 First Yoke Piece 25 Second Yoke Piece 28 Magnet 32 Base end portion 33 Elastic deformation portion 34 Fitting portion 40 Finite optical system block 41 Semiconductor laser 50 Optical pickup device 60 Recording / reproducing device

Claims (4)

[Claims] 1. A focusing coil for mounting a finite objective lens and generating a magnetic driving force acting in a focusing direction parallel to the optical axis of the finite objective lens, and a magnetic field acting in a tracking direction orthogonal to the optical axis of the finite objective lens. The bobbin member, to which the tracking coil that generates the driving force is assembled, and the free ends are vertically and separately fitted on both side surfaces of the bobbin member, thereby elastically displacing the bobbin member in the focusing direction and the tracking direction. The four elastic members formed by freely supporting springs, the first yoke piece which is joined to the magnet and penetrates inside the focusing coil, and the second yoke which is positioned so as to face the tracking coil And a bobbin for supporting the base end portion of the elastic member. An objective lens that tilts the finite objective lens in the tracking direction to correct the off-axis aberration caused by the deviation of the optical axis in conjunction with the displacement of the base member with the holding member fixed and the bobbin member in the tracking direction. An objective lens driving device having a tilting means. 2. A focusing coil that is mounted with a finite objective lens and that generates a magnetic driving force that acts in a focusing direction parallel to the optical axis of the finite objective lens and a magnetism that acts in a tracking direction orthogonal to the optical axis of the finite objective lens. The bobbin member, to which the tracking coil that generates the driving force is assembled, and the free ends are vertically and separately fitted on both side surfaces of the bobbin member, thereby elastically displacing the bobbin member in the focusing direction and the tracking direction. The four elastic members formed by freely supporting springs, the first yoke piece which is joined to the magnet and penetrates inside the focusing coil, and the second yoke which is positioned so as to face the tracking coil And a bobbin for supporting the base end portion of the elastic member. The finite objective lens has a rigid center of the four elastic members and a center of gravity of a movable portion constituted by the bobbin member and each member assembled to the bobbin member. In addition, the center of the magnetic driving force generated by the tracking coil is positioned above the focusing direction, so that the optical axis shifts in conjunction with the displacement operation of the bobbin member in the tracking direction. An objective lens driving device characterized in that off-axis aberrations that occur are corrected. 3. The four elastic members are configured such that the elastic members located on the lower side of both side surface portions of the bobbin member have greater rigidity in the tracking direction than the elastic members located on the upper side. 3. The center of gravity of the movable portion formed by the bobbin member and the members assembled to the bobbin member in correspondence with the rigidity center of the elastic member is positioned on the lower side in the focusing direction. The objective lens drive device according to item 1. 4. By adjusting the assembling position of the focusing coil and the tracking coil assembled to the bobbin member to the lower side in the focusing direction,
The objective lens driving device according to claim 3, wherein the center of gravity of the movable portion is configured to move downward in the focusing direction.