KR100570962B1 - Actuator for Optical Pickup - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup actuator in which two objective lenses are linearly driven in a vertical direction and a horizontal direction in an optical pickup apparatus having different optical conditions for accessing a heterogeneous optical disk.

The optical pickup actuator according to the present invention has two objective lenses, a bobbin member in which two objective lenses are installed, and a driving force installed in the bobbin member to be positioned between the two objective lenses to drive the bobbin member. It has a magnetic circuit for generating a.

With this arrangement, the optical pickup actuator according to the present invention is an optical pickup apparatus having different optical conditions for accessing heterogeneous optical disks, wherein each of the two objective lenses is linearly driven in the vertical and horizontal directions without lens switching. You can do it.

Description

Actuator for Optical Pickup {Actuator For Optical Pickup}             

1 is a view for explaining a conventional optical pickup actuator.

2A and 2B are diagrams illustrating an actuator of a axial sliding drive type provided with two objective lenses;

3A and 3B are views showing another form of the axial sliding drive actuator provided with two objective lenses;

4 is a sectional view of an optical pickup actuator according to a first embodiment of the present invention;

FIG. 5 is a perspective view of the actuator shown in FIG. 4. FIG.

6 is a plan view from above of the actuator shown in FIG. 4;

7 is a cross-sectional view showing a magnetic circuit of the actuator shown in FIG.

8 is a perspective view illustrating a magnetic circuit of the actuator shown in FIG. 4.

9 is a sectional view of an optical pickup actuator according to a second embodiment of the present invention;

FIG. 10 is a perspective view of the actuator shown in FIG. 9. FIG.

FIG. 11 is a perspective view illustrating the magnetic circuit of the actuator in FIG. 9; FIG.

FIG. 12 is a plan view showing the magnetic circuit of the actuator in FIG. 9; FIG.

FIG. 13 is a sectional view of the magnetic circuit of the actuator in FIG. 9; FIG.

<Description of Symbols for Major Parts of Drawings>

2,22a, 22b, 42a, 42b, 62a, 62b, 82a, 82b: objective lens

4,24,44,64,84: Bobbin 6,26,46,66,86: Permanent magnet

8,28,48,68,88: Yoke 10,30,50,70,90: Focusing coil

12,32,52,72,92: tracking coil 14,74,94: wire spring

16,76,96: frame 20,40: axis of rotation

34,54: Bobbin support damper 36,56: Base

78a, 78b, 98a, 98b: mirror 80a, 80b, 100a, 100b: light source

102: half mirror 104: collimating lens

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator for optical pickup, and more particularly, to an optical pickup apparatus having different optical conditions for accessing heterogeneous optical discs, wherein each of the two objective lenses is linearly driven in a vertical direction and a horizontal direction. It's about the actuator.

Due to the rapid development of optical discs, various optical pickups for recording / reproducing information of optical discs have been developed. The optical pickup moves the objective lens in the radial direction of the optical disc so that the optical spot focused by the objective lens follows the center of the signal track of the optical disc, and the objective lens is placed on the optical disc so that the optical spot falls within the depth of focus with respect to the signal track plane. An actuator is installed to move in the vertical direction. That is, the actuator moves the objective lens in two axis directions to perform tracking control and focusing control. These actuators form a coil in the magnetic space formed by the magnet and the magnetic body and are driven by Lorentz force generated by Fleming's left hand law.

Conventional actuators are movable parts including an objective lens 2, a bobbin 4, a focusing coil 10, a tracking coil 12, and a wire spring 14, as shown in FIG. 1, a permanent magnet 6, and a yoke And a fixing part including the frame 8 and the frame 16. In such an actuator, the driving force in the focusing direction depends on the direction of the current i applied to the focusing coil 10 that is connected to the magnetic flux lines in the magnetic space provided by the permanent magnet 6 and the yoke 8. Occurs in the direction of the optical axis in a direction perpendicular to the optical disk. Further, the driving force in the tracking direction of the actuator is generated in the radial direction of the disc in accordance with the direction of the current i applied to the tracking coil 12 facing the permanent magnet 6. The light focused from the objective lens 2 by the two-axis drive of the movable portion falls within the depth of focus with respect to the optical disk, and can follow the center of the track.

Recently, optical discs have been increased in capacity, and following a CD (Compact Disc), a DVD (Digital Video Disc) or a HD DVD (High Density Digital Video Disc) has been developed. As the optical disc becomes denser, the distance from the surface of the disc to the information recording surface becomes shorter. In practice, DVD-based optical discs have a distance of 0.6 mm from the surface of the disc to the information recording surface, while CD-based optical discs have a distance of 1.2 mm. Further, the wavelength? Of the light beam, the beam size BS, and the numerical aperture NA of the objective lens for accessing the DVD optical disc and the CD optical disc are different. For example, the wavelength (λ _C ) and the beam size (BS _C ) of the light beam used in the optical pickup apparatus for accessing the CD-based optical disk should have 780 nm and 1.4 μm, respectively, and the numerical aperture of the objective lens ( NA _C ) should be maintained between 0.35 and 0.45. On the other hand, the wavelength (λ _D ) and the beam size (BS _D ) of the light beam used in the optical pickup apparatus for accessing the DVD-based optical disc should have 635 to 650 nm and 0.9 μm, respectively, and the numerical aperture of the objective lens ( NA _D ) should be maintained at 0.6. In order to access such heterogeneous optical discs, the optical pickup apparatus needs to cope with the heterogeneous optical discs. Accordingly, as shown in FIG. 1, in the optical pickup apparatus in which an actuator for driving one objective lens is installed, two light sources generating light beams having different wavelengths and a beam diameter of the light beam incident on the same objective lens 2 are adjusted. Wavelength selection means or aperture means must be provided. In this case, a part of the light is blocked or selectively transmitted by the wavelength selecting means or the aperture means, so that the light efficiency becomes worse and the jitter increases.

In order to solve this problem, an optical pickup device for selectively driving two objective lenses corresponding to different optical disks according to the type of optical disk has been developed. 2 and 3, the optical pickup device is provided with an actuator for biaxially driving two objective lenses.

2A and 2B, an actuator for driving two objective lenses includes a bobbin 24 having two objective lenses 22a and 22b mounted thereon, a focusing coil 30 wound around the bobbin 24, and focusing. Movable part including tracking coil 32 and bobbin support damper 34 bonded on coil 30, rotary shaft 20, four permanent magnets 26, four yokes 28 and base 36 Consists of a fixed part including a. The bobbin 32 is rotatably fitted to the rotating shaft, and is rotated by the rotational force generated by the four permanent magnets 26 and the tracking coil 32 magnetized to select the objective lens 22a or 22b. In addition, the bobbin 32 is rotated by the rotational force generated by the permanent magnets 26 and the tracking coil 32 so that the light spot condensed from the objective lens 22a or 22b follows the center of the track, and the objective lens 22a is rotated. Alternatively, the light spot condensed from 22b) is vertically driven along the rotation shaft 20 by a vertical driving force generated by the permanent magnet 26 and the focusing coil 30 so as to fall within the depth of focus.

The actuator shown in FIGS. 3A and 3B has two objective lenses 42a and 42b mounted on the bobbin 44 similarly to those shown in FIG. 2, and the bobbin 44 is driven to track and objective lens ( In order to select 42a and 42b, a rotational movement about the rotational axis 40 is performed, and a linear movement along the rotational axis 40 is performed vertically for focusing.

However, since the actuators of FIGS. 2 and 3 use the axial sliding drive method, the movable part is commonly constrained to the rotation shafts 20 and 40 to rotate and linearly drive by the focusing / tracking servo. In other words, in the axial sliding drive type actuator, the objective lenses 22a, 22b, 42a, and 42b must be configured on the circumference of the movable portion, that is, on the circumference of the bobbins 22,42. , 22b, 42a, 42b are switched to coincide with one optical axis. In this case, an auxiliary driving device such as permanent magnets additionally installed to select one of the two objective lenses 22a, 22b, 42a, and 42b is required, and a rotating shaft It has a structure hard to be thinned by the height of (20,40). In addition, the actuators of FIGS. 2 and 3 have a disadvantage in that it is difficult to obtain dynamic driving characteristics due to friction caused by sliding of the rotation shafts 20 and 40. Furthermore, the actuator of the axial sliding drive type has a problem that tracking control is difficult because the tracking operation is performed in the form of a rotational movement about the rotation shafts 20 and 40.

Accordingly, an object of the present invention is to provide an optical pickup actuator for linearly driving two objective lenses in a vertical direction and a horizontal direction in an optical pickup apparatus having different optical conditions for accessing heterogeneous optical disks. .

Another object of the present invention is to provide an optical pickup actuator suitable for thinning in an optical pickup apparatus having different optical conditions for accessing heterogeneous optical disks.

In order to achieve the above objects, the optical pickup actuator according to the present invention is installed in the bobbin member so as to be located between the two objective lenses, the bobbin member is installed two objective lenses, and the two objective lenses And a magnetic circuit for generating a driving force for driving the bobbin member.

The optical pickup actuator according to the present invention includes two objective lenses, a bobbin member on which two objective lenses are installed, and a magnetic circuit installed on both sides of the bobbin to generate a driving force for driving the bobbin member.

Hereinafter, an optical pickup actuator according to the present invention will be described in detail with reference to FIGS. 4 to 13.

4 to 6, the optical pickup actuator according to the present invention includes a bobbin 64 mounted with two objective lenses 62a and 62b, a focusing coil 70 wound in the bobbin 64, and a focusing coil. A movable part including a tracking coil 72 and a wire spring 74 bonded to the 72, and a fixing part including a permanent magnet 66 and a yoke 68 inserted into the bobbin 64.

The bobbin 64 is mounted with the objective lenses 62a and 62b facing each other with a magnetic circuit generating a driving force therebetween, and a rectangular hole formed with the magnetic circuit is formed therein. The objective lenses 62a and 62b protrude symmetrically to the left and right of the bobbin 62 and the magnetic circuit does not overlap the optical path of the light beam incident on the objective lenses 62a and 62b. Light beams incident on the objective lenses 62a and 62b are generated from the light sources 80a and 80b. The light sources 80a and 80b generate light beams having different wavelengths, and the respective light beams are reflected toward the objective lenses 62a and 62b by the mirrors 78a and 78b.

As such, the two objective lenses 62a and 62b protrude on the bobbins 62a and 62b and the magnetic circuit does not overlap the optical path, thereby reducing the thickness of the actuator.

As shown in FIGS. 7 and 8, the magnetic circuit includes a permanent magnet 66 bonded to the yoke 68, a focusing coil 70 and a tracking coil 72 facing the permanent magnet 66. The permanent magnet 66 is bonded to the front and back of the yoke 68 bent in the form of "L". The wire spring 74 transmits a current signal supplied from a printed circuit board mounted on the frame 76 to the focusing coil 70 and the tracking coil 72 and elastically supports the movable part.

In this magnetic circuit, the driving force in the focusing direction is generated as a Lorentz force for linearly moving the movable part in a direction perpendicular to the optical disk by the Fleming's left-hand law in accordance with the direction of the current applied to the focusing coil 70. Here, the magnetic flux lines generated from the permanent magnet 66 linearly move the movable part in the vertical direction (focusing direction) while intersecting the focusing coil 70.

The driving force in the tracking direction is generated by the Lorentz force which linearly moves the movable part in the radial direction of the optical disc by the Fleming's left hand law in accordance with the direction of the current applied to the tracking coil 72. Here, the magnetic flux lines generated from the permanent magnets 66 linearly move the movable part in the horizontal direction (tracking direction) while linking the tracking coils 72.

In this way, the actuator according to the present invention is stable because there is no need to switch the objective lens and friction by the rotation axis unlike the conventional axial sliding drive type actuator by the light beam is incident on each of the two objective lenses (62a, 62b) Can be operated.

9 to 13 illustrate an optical pickup actuator according to another embodiment of the present invention.

9 and 10, the optical pickup actuator according to the present invention includes a bobbin 84 having two objective lenses 82a and 82b mounted thereon, and a focusing / tracking coil 90 bonded to a side surface of the bobbin 84. And a movable part including a wire spring 94 and a fixed part including a permanent magnet 86 and a yoke 88 installed to face the focusing / tracking coils 90 and 92.

The bobbin 84 is bent in a "c" shape, and two mirrors 98a and 98b are installed side by side. Objective lenses 82a and 82b are seated on bobbin 84 such that they are positioned over mirrors 98a and 98b. Light beams incident on the objective lenses 82a and 82b are generated from the light sources 100a and 100b. The light sources 100a and 100b generate light beams having different wavelengths. The light beam generated from the first light source 100a passes through the half mirror 102 and is converted into a parallel beam by the collimating lens 104, and then reflected by the first mirror 98a to be reflected by the first objective lens 82a. Is incident on. The light beam generated from the second light source 100b is reflected toward the collimating lens 104 by the half mirror 102 and converted into a parallel beam by the collimating lens 104, and then passes through the first mirror 98a and is first The light is reflected by the second mirror 98b and is incident on the second objective lens 82b. To this end, the half mirror 102 and the first mirror 98a are coated with a wavelength selective material to selectively transmit and reflect the light beam in accordance with the wavelength of the light beam. As a result, light beams generated from the different light sources 100a and 100b travel along the same light path and are incident on the first and second objective lenses 82a and 82b according to the wavelength.

As such, since the light beams propagate into the bobbin 84 and are incident on the objective lenses 82a and 82b and the magnetic circuit is positioned on the path of the light beam, the thickness of the actuator is reduced.

As can be seen from FIGS. 12 to 13, the magnetic circuit includes a permanent magnet 86 bonded to the yoke 68, a focusing coil 90 facing the permanent magnet 86, and a tracking coil 92. do. The yoke 88 is bent in a "c" shape, and the permanent magnets 88 are bonded to face each other on the opposite surface. The bobbin 84 is fitted inside the yoke 82 so that the focusing / tracking coils 90 and 92 face the permanent magnets 86. At this time, the coupling structure of the bobbin 84 and the yoke 2 is assembled in an inverted form, and the bobbin 84 is twisted by 90 ° with respect to the yoke 88. Permanent magnets 86 are bonded side by side three per one side of the yoke (88). In these permanent magnets 86, the magnetic flux lines 86a generated from the central permanent magnet 86 as shown in FIG. 13 vertically pass through the focusing coil 90 and horizontally through the tracking coil 92. The polarity of the permanent magnet 86 located at the center and the permanent magnet 86 located at the edge is magnetized to be reversed. The focusing coil 90 is wound long in the horizontal direction and is bonded to the side of the bobbin 84 so that the two are vertically adjacent to each other. Alternatively, the tracking coils 92 are long wound in the longitudinal direction, and two are bonded to the side of the bobbin 84 with the focusing coil 90 interposed therebetween. These focusing / tracking coils 90 and 92 are supplied with a current signal via a wire spring 94.

In this magnetic circuit, the driving force in the focusing direction is generated by the Lorentz force which linearly moves the movable part in a direction perpendicular to the optical disk by the Fleming's left-hand law in accordance with the direction of the current applied to the focusing coil 90. Here, the magnetic flux lines 86a generated from the single-pole permanent magnet 86 located at the center are the lower coil side of the upper focusing coil 90 and the upper coil side of the lower focusing coil 90 in two adjacent focusing coils 70. The linear motion of the movable part in the vertical direction (focusing direction) is performed while intersecting.

The driving force in the tracking direction is generated by a Lorentz force that linearly moves the movable part in the radial direction of the optical disc by the Fleming's left hand law in accordance with the direction of the current applied to the tracking coil 92. Here, the magnetic flux lines generated from the permanent magnet 86 located at the center are broken into the tracking coil 92 while turning to the permanent magnet 86 at the edge opposite to the polarity of the permanent magnet 86 located at the center. The movable portion is linearly moved in the horizontal direction (tracking direction) by the driving force generated in this way.

As described above, the optical pickup actuator according to the present invention is mounted to an optical pickup apparatus having different optical conditions to access two different optical disks by mounting two objective lenses on a bobbin and irradiating a light beam to each of the objective lenses. Therefore, each of the two objective lenses can be linearly driven in the vertical direction and the horizontal direction without lens switching. Accordingly, in the conventional axial sliding drive type actuator, tracking control is difficult and unstable because the tracking operation pivots about the rotation axis, whereas the actuator according to the present invention has tracking control because the tracking operation is performed in a linear direction in the horizontal direction. It can be performed stably. In addition, the optical pickup actuator according to the present invention can be thinned as much as the magnetic circuit for generating the driving force on the same line as the traveling path of the light beam without interfering the light beam. Therefore, the actuator according to the present invention is suitable for a slimming information device such as a notebook.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (12)

Two objective lenses, A bobbin member in which the two objective lenses are installed; The yoke is bent in the form of "L", permanent magnets bonded to the front and back on the vertical portion of the yoke, a focusing coil wound to surround the yoke and the permanent magnet, and is longitudinally wound And a tracking coil attached to the focusing coil, the magnetic circuit being installed inside the bobbin member so as to be positioned between the two objective lenses and generating a driving force for driving the bobbin member. Actuator for optical pickup. delete The method of claim 1, And a lens seating portion of the bobbin member on which the two objective lenses are seated, protruding toward a light source. The method of claim 1, The magnetic circuit is an optical pickup actuator, characterized in that installed on the extension line of the path of the light beam. The method of claim 1, Two reflecting mirrors installed under the two objective lenses to reflect light beams from different light sources to the two objective lenses; And a spring member for supplying a current signal to the magnetic circuit and elastically supporting the bobbin member. Two objective lenses, A bobbin member in which the two objective lenses are installed; The yoke bent in a "c" shape, the permanent magnet magnetized on the opposite side of the bent yoke and multipolar magnetized, and wound in the transverse direction to face the permanent magnet on the bobbin member. A focusing coil bonded to the focusing coil, the tracking coil being longitudinally wound and adjacent to the focusing coil and bonded to the bobbin member to face the permanent magnet, and installed on both sides of the bobbin to provide the bobbin member. An optical pickup actuator, characterized in that it comprises a magnetic circuit for generating a driving force for driving. The method of claim 6, The bobbin member is an optical pickup actuator, characterized in that bent in a "c" shape so that the traveling path of light is provided therein. delete The method of claim 6, The permanent magnet is the first permanent magnet located in the center, And second permanent magnets adjacent to both sides of the first permanent magnet and magnetized in a polarity opposite to that of the first permanent magnet. The method of claim 6, The magnetic flux lines generated from the permanent magnets vertically pass through the focusing coil and pass through the tracking coil by turning. The method of claim 6, The magnetic circuit is an optical pickup actuator, characterized in that installed on the same line as the traveling path of the light beam. The method of claim 6, Two reflecting mirrors installed under the two objective lenses to reflect light beams from different light sources to the two objective lenses; And a spring member for supplying a current signal to the magnetic circuit and elastically supporting the bobbin member.

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