JPH10188310A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the objective lens driving device equipped with objective lenses corresponding to various optical information recording media, capable of changing these objective lenses to be correspondent to a recording medium, having enough rigidity against this changeover operation and preventing the occurrence of misalignmenet. SOLUTION: The 1st objective lens 34 and the 2nd objective lens 35 are fixed to a reinforcing part of a lens holder 75. A core member made of a metallic material is burried in this reinforcing part, whose wall thickness is thicker than the other parts. Four magnetic substances are burried symmetrically around a rotary shaft in a surrounding part of the lens holder, and coils are fixed on these magnetic substances. Four permanent magnets 81 and 82 corresponding to the coils are fixed to a supporting body 74 for rotatably supporting the lens holder 75. One set of the permanent magnets 81 opposite to each other function as focus control, and the other set of the permanent magnets 82 opposite to each other function as tracking control and also changing the objective lenses.

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 mounted on an optical disk device, and more particularly to an objective lens driving device capable of switching objective lenses having different numerical apertures according to the type of recording medium.

[0002]

2. Description of the Related Art In recent years, with the development of various types of optical information recording media such as optical disks and magneto-optical disks, the development of an objective lens driving device used for a reproducing device of these optical information recording media has been activated. Objective lens driving devices have already been widely and widely used as driving devices for compact discs (CDs) or CD-ROMs. Recently, objective lens driving devices not only for reproduction but also for recording have been used. Has been developed, especially magneto-optical (Magnet-0ptica
l) A recording method such as a recording method or a phase modulation (Phase-Change) recording method is known. Many of these schemes are currently specified in detail in standards. However, in recent years, a high-density recording type optical disk aiming at higher recording density, that is, a DVD disk has emerged.
The development and application research of the VD disk is rapidly progressing. In such an optical disc, a pit as an information recording unit is formed smaller than a conventional CD for high-density recording, and it is required that the pit be searched with high accuracy. Such a high-density recording type optical disc has a different substrate thickness from a conventional CD.
In the apparatus for reproducing the optical disk, the wavelength of the laser beam for searching for the pits becomes shorter, and the numerical aperture NΑ (Numerical Aperture) of the objective lens is set to be large, so that the diameter of the beam spot formed on the optical disk becomes larger. It is designed to be smaller.

[0003] When various improvements are made to the device measurement in order to support the newly appeared DVD disk as described above, there is a problem that such a device makes it difficult to record and reproduce the optical disk in accordance with the conventional standard. However, there is an inconvenience for the user in preparing a disk device according to the recording medium.

As a method for solving such a problem, as disclosed in US Pat. No. 5,235,581, there is a method in which a plurality of optical character heads having different focal lengths are arranged in the same optical disk device. . In this disk drive,
The two optical heads are arranged independently so as to be capable of tracking drive, and enable recording and reproduction from a conventional optical disc such as a compact disc.

[0005]

However, in such a system, two optical heads are disposed so as to face each other with respect to the center of the optical disk, and two optical heads are disposed adjacent to each other. It is not possible to do. Therefore, in an optical disk apparatus employing such a method, an optical disk (eg, CD-ROM or MO) used in a cartridge (caddy) having a window has a window opening with a limited area. There is a problem that neither of the two objective lenses can be located below. Further, with the spread of the optical disk device, there is a great demand for lowering the price of the device, and the necessity of two optical heads poses an obstacle to such a demand. In the future, research on DVD-ROM discs will be promoted,
It is expected that a new DVD-ROM disc will appear. There is a demand for an optical disk device that can handle newly appearing disks.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an objective lens corresponding to various optical information recording media, and to switch the objective lens according to the recording medium. It is another object of the present invention to provide an objective lens driving device which has sufficient rigidity for the switching operation and can prevent the alignment from being out of order.

[0007]

According to the present invention, there is provided a lens holder having a center of rotation and holding first and second objective lenses, which reinforces a mounting portion for the first and second objective lenses. A lens holder having a reinforcing portion to be rotated, supporting means for allowing the lens holder to rotate around the center of rotation and allowing the lens holder to move along the center of rotation, and a first objective at a predetermined position by rotating the lens holder. Second instead of lens
And a lens switching unit for positioning the objective lens.

[0008] According to the present invention, it has a center of rotation, and the first
A lens holder having a reinforcing portion having a hole for mounting a second objective lens, wherein the lens holder has first and second objective lenses mounted and fixed in the hole of the lens holder; and Support means for allowing the holder to rotate about the center of rotation and moving the holder along the center of rotation; and rotating the lens holder to position the second objective lens in place of the first objective lens at a predetermined position. And an objective lens driving device comprising:

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a DVD disk reproducing apparatus provided with an objective lens driving device according to an embodiment of the present invention. FIG. 1 is a block diagram of an optical disk according to an embodiment of the present invention, that is, a DVD disk reproducing apparatus for reproducing data from a DVD disk.
Shows a block of a disk drive unit for driving the DVD disk shown in FIG. 1, and FIG. 3 shows a structure according to an example of a DVD desk as a recording medium shown in FIGS.

In the DVD disk reproducing apparatus shown in FIG. 1, the user operates the key operation unit and the display unit 4 to reproduce recorded data, that is, video data, sub-video data and audio data from the DVD disk 10. The signal is converted into an audio signal and a video signal in the apparatus, and reproduced as video and audio by the monitor unit 6 and the speaker unit 8 outside the apparatus.

The DVD disk 10 includes a standard DVD disk for reproducing video and the like, and a DVD-RO
M, and as already known DVD disc 1
0 has various structures. Generally, as shown in FIG. 3, for example, a DVD disk is provided with a pair of structures 18 in which a recording layer, that is, a light reflection layer 16 is formed on a transparent substrate 14. Are bonded together via an adhesive layer 20 so that the recording layer 16 is sealed therein. In the optical disc 10 having such a structure, a center hole 22 into which the spindle of the spindle motor 12 is inserted is provided at the center thereof, and a clamping area for holding the optical disc 10 at the time of rotation is provided around the center hole 22. 24 are provided.

An information recording area 25 from which information can be recorded on the optical disk 10 is defined from the clamping area 24 to the outer peripheral end of the optical disk 10. In the DVD disk shown in FIG.
Will be provided. Each information recording area 25 has a lead-out area 26 in which the outer peripheral area is not normally recorded with information.
Similarly, the inner peripheral area adjacent to the clamping area 24 is also the lead-in area 2 where information is not normally recorded.
7, and a data recording area 28 is defined between the lead-out area 26 and the lead-in area 27. In the recording layer 16 of the information recording area 25, usually, tracks are continuously formed in a spiral shape as areas in which data is recorded, and the continuous tracks are divided into a plurality of sectors, and data is recorded based on these sectors. Is recorded. The data recording area 28 of the information recording area 25 is an actual data recording area in which management data, main image data, sub-image data, and audio data are similarly recorded as physical state changes such as pits. In the read-only optical disk 10, a pit row is formed on the transparent substrate 14 by a stamper in advance, and a reflective layer is formed by vapor deposition on the surface of the transparent substrate 14 where the pit row is formed, and the reflective layer is formed as the recording layer 14. Will be done. In the read-only optical disc 10, no groove is usually provided as a track, and a pit row is defined as a track. Normally, such a DVD disk 10 uses a conventional CD, CD-R or CD-ROM.
The transparent substrate of the optical disk has a thickness of 1.2 mm, whereas the transparent substrate 14 has a thickness of 0.6 mm, which is half of the transparent substrate.

In such a disk reproducing apparatus for reproducing data from the DVD disk 10, the DVD disk 10 is loaded and the disk drive unit 30 for driving the DVD disk searches the DVD disk 10 with a light beam. That is, as shown in FIG. 2, the DVD disk 10 is mounted on a spindle motor 12 driven by a motor drive circuit 11, and the spindle motor 1
Rotated by 2. An optical head for condensing a light beam, that is, a laser beam on the DVD disk 10, that is, an optical pickup 32, is provided below the DVD disk 10.
Is provided. The optical pickup 32 will be described in detail. The optical pickup 32 is an optical unit 47 including an objective lens 35 having a small numerical aperture for a CD or CD-ROM, and the high-density recording described with reference to FIG. An optical unit 46 including an objective lens 34 having a large numerical aperture for a type DVD disk is provided. Also,
As shown in FIG. 2, an objective lens switching drive circuit 39 for generating a drive signal for switching the objective lenses 34 and 35.
Is provided. When the type of the DVD disk 10 to be searched, that is, the type of the conventional CD or the like or the type of the high-density recording is specified, the objective lens switching circuit 39 is activated to operate the specified type of DVD. One of the objective lenses 34 and 35 is selected by a drive signal from the objective lens switching drive circuit 39 corresponding to the disk 10 and is arranged in the laser beam optical path.

The optical head 32 has an information recording area 25,
In particular, in order to search the data recording area 28, the DVD drive 10 is mounted on a guide mechanism so as to be movable in the radial direction of the DVD disc 10, and is driven by a drive signal from a drive circuit 37 by a feed motor 33. Moved to In the DVD disk 1 device, as will be described in detail later, the objective lenses 34 and 35 are movably held along the optical axis, and are moved in the optical axis direction in response to a drive signal from the focus drive circuit 36. The objective lenses 34 and 35 are always kept in a focus state, and a minute beam spot is formed on the recording layer 16. Further, the objective lenses 34 and 35 are used for the DVD disc 10 as described later in detail.
And is finely moved in response to a driving signal from a track driving circuit 38, and is always maintained in a tracking state, and tracks on the recording layer 16 of the DVD disk 10 are tracked by a light beam. You.

In the optical head 32, a light beam reflected from the DVD disk 10 is detected, and the detected signal is supplied from the optical head 32 to the servo processing circuit 44 via the head amplifier 40. Servo processing circuit 4
In 4, the focus signal, the tracking signal, and the motor control signal are generated from the detection signal, and these signals are supplied to the drive circuits 36, 38, and 11, respectively. Therefore, the objective lenses 34 and 35 are maintained in the focus state and the tracking state, the spindle motor 12 is rotated at a predetermined rotation speed, and the track on the recording layer 16 is a light beam by the light beam, for example, a constant linear velocity. Tracked at. When a control signal as an access signal is supplied from the system CPU unit 50 to the servo processing circuit 44, a movement signal is supplied from the servo processing circuit 44 to the drive circuit 37, and the optical head 32 is moved along the radial direction of the DVD disk 10. The data is moved, a predetermined sector of the recording layer 16 is accessed, and the reproduced data is amplified by the head amplifier 40 and output from the disk drive unit 30.

The output reproduction data is stored in a system RO.
M and a system processor unit 54 and a system processor unit 54 controlled by a program recorded in the RAM unit 52
Through the data RAM 56. The stored reproduction data is processed by the system processor 54 and classified into video data, audio data, and sub-picture data. The video data, audio data, and sub-picture data are respectively processed by the video decoder 58 and the audio decoder 60. And output to the sub-picture decoder 62 for decoding. The decoded video data, audio data, and sub-picture data are converted into analog video signals, audio signals, and sub-picture signals by a D / A and reproduction processing circuit 64, and are also subjected to mixing processing to produce video signals and sub-picture data. The signal is sent to the monitor 6,
Further, audio signals are supplied to the speakers 8 respectively.
As a result, an image is displayed on the monitor unit 6 and sound is reproduced from the speaker unit 8.

The details of the optical pickup 32 and its guide mechanism shown in FIG. 2 will be described with reference to FIGS.
The spindle motor 12 already described is fixed to a base 71 as shown in FIG. 4, and the DVD disk 10 rotated by the spindle motor 12 is held by chucking means (not shown). Also, DV
Below the D disk 10, a pair of guide rails 73 arranged parallel to the radial direction are fixed to the base 71. The guide rail 73 includes the guide rail 7.
A carriage 72 that runs on the carriage 3 is mounted on the carriage 72, and an objective lens actuator 70 shown in FIGS. 5 and 6 is provided on the carriage 72.

The lens actuator 70 shown in FIGS. 5 and 6 includes a lens holder 75 that can float and rotate, and a lens holder support 74 in which the lens holder 75 is received. An actuator base 76 fixed to the carriage 34 is provided on the lens holder support 74, and a shaft 77 is fixed to the center of the actuator base 76. Also, this support 7
4 includes an arc-shaped yoke 79 along the circumference around the axis 77.
, Which is fixed to the actuator base 76. As shown in FIG. 7, two sets of arc-shaped permanent magnets 81 and 82 in which sets facing each other are magnetized in the same magnetization direction are symmetrically arranged around the axis 7 on the arc-shaped yoke 79. I have. This one set of permanent magnets 81 has a shaft 77,
That is, the magnets are magnetized so that the N and S poles are arranged in the direction along the center line C, and the other set of permanent magnets 82 is magnetized along the arc of the arc-shaped yoke 79.

As shown in FIGS. 8 and 9, the lens holder 75 is formed of a substantially cylindrical frame 46 and a cover 47 for closing the opening of the cylindrical frame 46. An objective lens 35 of a type and a high-density recording type, that is, an objective lens 34 for DVD are fixed. As shown in FIG. 9, the front surface of the cover 47 facing the disk 10 is formed substantially flat, and as shown in FIG. 10, the rear surface has a portion to which the objective lenses 34 and 35 are attached, such as aluminum. Is formed in the reinforcing thick portion buried as a core, and the other portion is formed in a structure having steps formed thin. Each objective lens 34,
A mounting hole is drilled in the lid portion 47 to mount the lens 35, and each of the objective lenses 34 and 35 is arranged in the mounting hole so that the optical axis thereof is arranged on the same circumference around the center of the lens holder 75. Each is fixed.

The lens holder support 74 and the lens holder 75 are made of a resin material in order to enhance moldability.
Rigidity is increased by mixing carbon or glass fiber therein, but since the core material is buried and the reinforcing portions to which the objective lenses 34 and 35 are attached are formed thicker, The rigidity of the objective lens mounting portion is enhanced. In the above-described embodiment, the lens holder 75 has been described as an example in which the cylindrical frame 46 and the lid 47 are formed separately. However, as is apparent, the cylindrical frame 46 and the lid 47 are integrally formed. The cover 47 may be formed with a thick portion in which a core material is incorporated. Furthermore,
When the core material is embedded as described above, each objective lens 3 is placed in the lens holder 75 when the lens holder is molded.
Cavities are provided underneath 4, 35 so that a laser beam can pass therethrough.
In the same manner, an opening for passing a laser beam is formed. A bearing 83 through which a shaft 77 is inserted is fixed to the center of the lens holder 75, and the lens holder 75 is supported by the shaft 77 so as to be rotatable and vertically movable. Around the lens holder 75, a magnetic material 84 is symmetrical with respect to the axis 77.
Are embedded in the magnetic body 84, and four magnetic coils 8 similarly arranged symmetrically with respect to the axis 77.
5, 86 are fixed.

At the center of the lens holder 75,
A bearing 83 through which the shaft 77 is inserted is fixed, and the lens holder 75 can be rotated by this bearing 83, and
It is supported on a shaft 77 so as to be vertically movable. Below this lens actuator, a bending mirror 88 fixed to the carriage 72 is arranged corresponding to each lens,
The light beam guided from the outside is reflected by the bending mirror 8.
8 and is directed to one of the objective lenses 34 and 35 via an optical path in the lens holder 75.

FIG. 11 shows the optical pickup 32 described above and an optical unit 90 of an optical system related to the optical pickup 32. As is clear from FIG. 11, the optical system shown in FIGS. 4 and 5 includes a moving optical system mounted on a carriage 72 and a fixed optical system as an optical unit 90 that sends a light beam to the moving optical system and receives the light beam. Consists of a system. That is, the optical disk 10
Laser 94 that generates a laser beam focused on
The optical unit 90 includes a base 7 as a fixed body.
Fixed to 1. The laser beam emitted from the semiconductor laser 94 of the optical unit 90 is
The light is collimated by a collimator lens 91 inside, is reflected by a beam splitter 93, and is guided to the outside of the optical unit 90. The laser beam from the optical unit 90 is fixed on a carriage 72 as a movable side, is reflected by a mirror 88, and is guided to one of the objective lenses 34 and 35 of the optical pickup 32.
The laser beams are condensed on the recording tracks of the optical disk 10 by 4 and 35. Further, the laser beam reflected from the optical disk 1 is again applied to one of the objective lenses 3.
The light is returned to the fixed-side optical unit 90 via 4 and 35. In the optical unit 90, the laser beam passes through a beam splitter 93, is divided into two systems by a beam splitter 95, is condensed by condenser lenses 96 and 97, respectively, and is provided in a first unit provided in the optical unit 5. Photodetector 9
8 and the second photodetector 99. Based on the detection signals from the photodetectors 98 and 99, an information signal, a focus error signal, a track error signal, and the like are generated as described above. One of the objective lenses 3 selected by using the focus error signal
4, 35 in the focus direction are detected, and the coil 8 is corrected as will be described later so as to correct the position shift.
Current is supplied to one of 5, 86. Further, a positional deviation of the objective lenses 34 and 35 in the track direction is detected by using the track error signal, and a current is supplied to the other of the coils 85 and 86 by correcting the positional deviation. In this way, information is recorded on the recording track of the optical disk 10, and the information is read from the recording track of the optical disk 10. Optical pickup 3 described above
The details of the operation 2 will be described below.

First, the reason why the lens holder 75 is magnetically levitated in the lens holder support 74 by a so-called magnetic spring will be described. As described above, two sets of permanent magnets 81 and 82 are arranged symmetrically around the axis 77 of the lens holder support 74 on the lens holder support 74 as shown in FIG. This permanent magnet 8
A magnetic body 84 is opposed to each of 1 and 82 with a gap. That is, the magnetic body 84 is symmetrically disposed around the axis 77, and the magnetic body 84 is fixed to the lens holder 75. Accordingly, the magnetic material 84 is attracted to the permanent magnets 81 and 82, and the permanent magnets 81 and 82 and the magnetic material 84 are connected to each other as shown in FIG.
13 (b) and a neutral position, which is a stable state as shown in FIG.
5 is magnetically levitated in the lens holder support 74. Here, a disturbance is given to the lens holder 75 and FIG.
When the magnetic body 84 is displaced upward from the neutral position as shown in FIG. 5, the magnetic body 84 has a larger downward force to return the magnetic body 84 to the neutral position than the upward force. As a result, the magnetic body 84 is returned to the neutral position. Similarly, when a disturbance is given to the lens holder 75 and the magnetic body 84 is deflected downward from the neutral position as shown in FIG. 12E, the magnetic body 84 exerts a lower force than a downward force. The upward force that returns the magnetic body 84 to the neutral position is large, and as a result, the magnetic body 84 is returned to the neutral position. When a disturbance is applied to the lens holder 75 and the magnetic body 84 is deviated rightward along the circumferential direction from the neutral position as shown in FIG. Magnetic body 8 rather than force in the direction
The force to the left that returns 4 to the neutral position is large,
As a result, the magnetic body 84 is returned to the neutral position. Similarly, when a disturbance is given to the lens holder 75, and FIG.
When the magnetic body 84 is deviated leftward from the neutral position along the circumferential direction as shown in FIG. 2 (f), the magnetic body 84 is applied to the neutral position more than the leftward force. As a result, the magnetic body 84 is returned to the neutral position as shown in FIG.

Since the magnetic body 84 is mounted at an axially symmetric position, when the objective lens is switched by rotating the lens holder 85 as described below, the neutral position determined by magnetic attraction is set. Since the original position of the first objective lens 34 in the above-mentioned position coincides with the neutral position of the new second objective lens 35, the second objective lens 34 is adjusted as it is by the optical unit 90 and the first objective lens 34, and the second An objective lens 35 can be used.

Next, the switching operation of the objective lenses 34 and 35 for selecting the objective lenses 34 and 35 will be described.
The objective lens 3 having a large numerical aperture as shown in FIG.
In the state where it is arranged at a predetermined position where 4 is valid,
It is assumed that the coil 85 faces the circumferentially magnetized permanent magnet 82, and the coil 85 faces the axially magnetized permanent magnet 81. This state corresponds to the neutral state described above, and the lens holder 75 is stably maintained at the same position. In such a stable state,
As shown in FIG. 15, when a current in the positive direction is supplied to the coil 85 at time t1 as shown by an arrow P0, as shown in FIG.
As shown in FIG. 16, a current interacting with the magnetic field generated by the permanent magnet 82 is supplied to the axis 75 of the coil 85, that is, the axial portions 85A and 85B parallel to the center. As shown in ()), a force FR for generating a rotational force in the circumferential direction is generated, and the lens holder 75 starts rotating. Between the time point t1 and the time point t2, a starting force for sufficiently rotating the lens holder 75 is applied to the coil 85. As shown in FIG. 16 (b), the coil 85 starts rotating, and as shown in FIG. 16 (c), the coil portion 85B on the retreat side of the coil 85 is opposed to the S pole of the permanent magnet 82 at time t2. The supplied current is inverted as shown in FIG. Due to this reversal, a rotational force FR for retreating the coil 85 from the permanent magnet 82 is generated between the coil portion 85B on the retreat side of the coil 85 and the S pole of the permanent magnet 82, and is applied to the coil 85. As a result, the coil 8
5 is rotated toward the front surface of the permanent magnet 81 as shown in FIG. At time t3 during the rotation, the coil 8
5 is stopped, and after time t3, the lens holder 75 is rotated by inertia, and the coil 85 temporarily passes through the neutral point of the permanent magnet 81, but has already been described with reference to FIG. By the principle, the coils 86 and 85 are returned to the stable neutral position. As shown in FIG. 14B, the rotation of the lens holder 75 causes the coil 86 to face the permanent magnet 82, the coil 85 to face the permanent magnet 81, and the aperture instead of the objective lens 34 having a large numerical aperture. A small number of objective lenses 35 are arranged in the optical path of the laser beam, and the objective lenses are substantially switched.

When the lens holder 75 is rotated and the objective lenses 34 and 35 are switched, if the clearance between the rotary shaft 77 and the rotary bearing 83 is set to 10 μm or less, the first objective lens The displacement of the mounting position between the second objective lens 35 and the second objective lens 35 can be ignored.

Further, the optical pickup 32 shown in FIG.
Will be described. When the objective lens 34 having a large numerical aperture is arranged in the optical path of the laser beam as shown in FIGS. 4 and 14A, the objective lens 34 faces the permanent magnet 81 magnetized in the axial direction for focus control. The coil 86 operates as a focus control coil, and the coil 85 facing the permanent magnet 82 magnetized along the circumferential direction for tracking control functions as a tracking control coil. That is, as shown in FIG. 17, when the focus coil driving current Fi is supplied to the coil 86 in response to the focus error signal, the distance between the circumferential portions 86C and 86D of the coil 86 and the magnetic field Bg generated by the permanent magnet 81 is increased. And an upward or downward force FV acts on the permanent magnet 81 in accordance with the direction of the current Fi, and the lens holder 7
5 is moved up and down along the axial direction, and the objective lens 34 is kept in focus. Also, as shown in FIG. 17, when the tracking coil drive current Ti is supplied to the coil 85 in response to the tracking error signal, the axial portions 85A and 85B of the coil 85 and the magnetic field By generated by the permanent magnet 82 Interaction occurs between them, and a rightward or leftward force FR acts on the coil 85 according to the direction of the current Ti to rotate the lens holder 75 in the circumferential direction,
The objective lens 34 is maintained in the combined track state.

After switching to the objective lens 35 as described above, the objective lens 35 having a small numerical aperture is arranged in the optical path of the laser beam as shown in FIG. In this state, the coil 8 opposed to the permanent magnet 81 magnetized in the axial direction for focus control
A coil 86 facing the permanent magnet 82 magnetized along the circumferential direction for tracking control acts as a tracking control coil. That is, when the focus coil driving current Fi is supplied to the coil 85 in response to the focus error signal, an interaction occurs between the circumferential portions 85C and 86D of the coil 85 and the magnetic field generated by the permanent magnet 81,
Depending on the direction of the current Fi, the coil 85 faces upward, or
The downward force FV acts to move the lens holder 75 up and down along the axial direction, and the objective lens 34 is maintained in focus. When the tracking coil drive current Ti is supplied to the coil 86 in response to the tracking error signal, an interaction occurs between the axial portions 86C and 86D of the coil 86 and the magnetic field generated by the permanent magnet 82,
Depending on the direction of the current Ti, the coil 86 is turned rightward, or
A leftward force FR acts to rotate the lens holder 75 along the circumferential direction, and the objective lens 34 is maintained in the combined track state.

As described above, in the objective lens driving device according to the present invention, since the objective lenses 34 and 35 are switched by the coil that performs the tracking operation without applying an external force, an excessive force acts, A stable signal can be reproduced without tilting the axis. Since the roles of the coils 81 and 82 when switching the objective lenses 34 and 35 are switched from the tracking operation to the focusing operation or vice versa, the utilization efficiency of the coils is improved and the driving sensitivity is improved. .

Further, since the lens holder 75 is provided with a thick portion as a reinforcing portion in which a core such as aluminum is incorporated as a core, the rigidity of the lens mounting portion of the lens holder 75 is enhanced, It is possible to reliably prevent an accident such as misalignment of the optical system during the operation.

In the lens holder support 74 and the lens holder 75, the rigidity is increased by mixing carbon or glass fiber into a resin material for improving moldability.
It is said that there is a limit to the density and amount that can be mixed. As described above, by incorporating the core material into the lens mounting portion of the lens holder 75, the rigidity is further increased. Further, since the rigidity of the lens mounting portion that requires rigidity can be reliably increased, the thickness of the lens holder itself can be reduced, and accordingly, the thickness of the lens driving device itself can be reduced.

If a sufficient strength can be obtained simply by increasing the thickness of the lens mounting portion of the lens holder 75, it is not necessary to incorporate the core material into that portion. Further, the core material is not limited to a metal, and may be a ceramic or a carbon phi material. Further, the present invention is not limited to the case where the step is formed in the cover by embedding the core material, but the cover may be formed flat or may be formed in various shapes.

Further, in the above-mentioned objective lens switching and driving device, when the number of objective lenses is n, it is preferable that 2n permanent magnets and coils are circumferentially arranged as a magnetic circuit. With such a relationship, the coils and the permanent magnets facing each other form a magnetic circuit for focus or tracking control, and the lens holder is operated uniformly in focus control and track control. Can be driven. That is, the vibration characteristics can be improved and the driving characteristics can be improved.

As described above, according to the present invention, the coil performs the tracking control based on the rotational force and serves as a drive source for switching the objective lens, so that the structure can be simplified and the objective lens can be made high. Since it is fixed to the rigid portion, it is possible to reliably prevent the alignment error due to the repetition of the rotation operation.

Since the original position of the first objective lens at the neutral position determined by the magnetic attraction coincides with the new neutral position of the second objective lens, the optical unit 5 and the first objective lens are used. The second objective lens can be used as it is in the adjusted state.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an optical disk device according to one embodiment of the present invention.

FIG. 2 is a block diagram showing details of the disk drive device shown in FIG.

FIG. 3 is a perspective view schematically showing the structure of the optical disc shown in FIG.

FIG. 4 is a plan view schematically showing an objective lens driving device for switching and driving the objective lens shown in FIG. 2;

FIG. 5 is a perspective view showing an optical pickup of the objective lens driving device shown in FIG.

6 is an exploded perspective view showing an arrangement of a lens driving device of the optical pickup shown in FIG.

FIG. 7 is a perspective view showing an arrangement of permanent magnets of the optical pickup shown in FIG.

8 is a perspective view showing a lens holder of the optical pickup shown in FIG.

9 is a perspective view showing the lens holder of the optical pickup shown in FIG. 5, in which a lens mounting portion of the lens holder is broken.

10 is a perspective view showing the structure of the lid of the lens holder shown in FIG. 9 from the back.

11 is a schematic diagram schematically showing the optical pickup shown in FIG. 5 and an optical system related to the optical pickup.

FIG. 12 is a conceptual diagram for explaining the principle of magnetically levitating a lens holder in the optical pickup shown in FIG.

13 is a perspective view showing an arrangement of a permanent magnet and a magnetic body at a neutral position in a state where the lens holder is magnetically levitated in the optical pickup shown in FIG. 5;

14A and 14B are plan views showing states before and after objective lens switching in the objective lens driving device.

FIG. 15 is a waveform diagram showing signals for causing a magnetic circuit to perform an objective lens switching operation.

FIG. 16 is a perspective view showing an arrangement of coils of the lens driving device of the optical pickup shown in FIG. 5;

FIG. 17 is a perspective view showing a switching operation in the lens driving device of the optical pickup shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Disc 30 ... Disc drive part 32 ... Optical pickup 34,35 ... Objective lens 36 ... Focus drive circuit 37 ... Drive circuit 39 ... Objective lens switching drive time 44 ... Servo processing circuit 46 ... Frame part 47 ... Lid part 50 ... System CPU 54: System processor 56: Data RAM 58: Video decoder 60: Audio decoder 62: Sub-video decoder 64: D / A and reproduction processing circuit 73: Guide rail 72: Carriage 75: Lens holder 74: Support Body 81, 82 ... Permanent magnet 85, 86 ... Coil

Claims (11)

[Claims] A lens holder having a center of rotation and holding a first and a second objective lens, the lens holder having a reinforcing portion for reinforcing a mounting portion of the first and second objective lenses; A supporting means for rotating the lens holder around the center of rotation and allowing the lens holder to move along the center of rotation; and rotating the lens holder to place a second objective lens at a predetermined position in place of the first objective lens. Lens switching means for positioning; and an objective lens driving device. 2. The lens switching means comprises at least a first magnet and a first coil.
A first electromagnetic driving means for rotating the lens holder around a rotation center when the lens is selected, and at least a second magnet and a second coil;
A second electromagnetic driving means for translating the lens holder in a direction along the center of rotation when the lens is selected, wherein the first and second magnets are fixed to the lens holder, and the first and second magnets are fixed to the lens holder. When the first and second coils are provided on the support means in opposition to each other, and the lens holder is rotated and moved beyond the tracking operation range, the objective lens is switched and the second objective lens is enabled,
The first magnet and the second coil constitute third electromagnetic driving means for rotating the lens holder around a rotation axis, and
4. The objective lens driving device according to claim 1, wherein the magnet and the first coil constitute fourth electromagnetic driving means for moving the lens holder in parallel in the axial direction of the rotation axis. 3. The objective lens driving device according to claim 1, wherein the first magnet, the first coil, the second magnet, and the second coil are arranged point-symmetrically with respect to a rotation axis. . 4. The objective lens driving device according to claim 1, further comprising a transporting unit mounted with said lens holder, said supporting unit and said first and second driving units and transporting the lens holder in a predetermined direction. apparatus. 5. The objective lens driving device according to claim 1, wherein a core material is embedded in the reinforcing portion. 6. The objective lens driving device according to claim 1, wherein the reinforcing portion is formed in a thicker portion than other portions of the lens holder. 7. The objective lens driving device according to claim 1, wherein the lens holder is formed of a resin mixed with a reinforcing agent. 8. A lens holder having a center of rotation and a reinforcing portion having holes for attaching the first and second objective lenses, wherein the first and second holes are formed in the holes of the lens holder.
A lens holder to which the objective lens is mounted and fixed; supporting means for allowing the lens holder to rotate around the center of rotation and allowing the lens holder to move along the center of rotation; and rotating the lens holder to a predetermined position. Lens switching means for positioning a second objective lens in place of the first objective lens. 9. The objective lens driving device according to claim 8, wherein a core material is embedded in the reinforcing portion. 10. The objective lens driving device according to claim 8, wherein said reinforcing portion is formed in a thicker portion than other portions of the lens holder. 11. The objective lens driving device according to claim 8, wherein the lens holder is formed of a resin mixed with a reinforcing agent.