JPH10106001A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the accuracy of positioning an objective lens caused by the recovering force of a power supplying means by setting an objective lens disposing angle to be different from a magnetic circuit disposing angle in an objective lens driving device having a plurality of mounted objective lens. SOLUTION: First and second objective lenses 2 and 3 are disposed to have an objective lens disposing angle 12 to the axial center of a shaft 1 being shifted by a specified amount from a magnetic circuit disposing angle 13 made of a magnetic material 4 and a magnet 6 to the axial center of the same. Thus, a shifted objective lens position is properly corrected by the resisting force of a flexible printed circuit(FPC) 10 and the objective lenses are accurately positioned at the time of lens switching.

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 mechanism for an optical disk device, and more particularly to an objective lens driving device using a plurality of objective lenses.

[0002]

2. Description of the Related Art In a recording / reproducing method using an optical disk, there are several different recording / reproducing methods. Generally, there is no compatibility between these methods, and users have responded by preparing necessary optical disks and optical disk devices as appropriate. In recent years, an optical disk recording / reproducing apparatus equipped with a plurality of optical systems has been proposed in order to support two or more types of recording / reproducing methods. As such a material, for example, Nikkei Mechanical (1995.8.7 No. 46)
0) describes that a plurality of optical systems are realized by mounting two objective lenses on a movable portion.

In such a system, a mechanism for creating a desired stable point for each objective lens is provided by using a magnetic spring composed of a magnet and a magnetic piece. A current can be supplied to a coil for driving in the focus direction and the tracking direction provided on the movable portion by a power supply unit such as a flexible printed circuit (hereinafter, FPC). At the time of the switching operation of the objective lenses, the switching operation of a plurality of objective lenses is realized by instantaneously applying a pulsed current to the coil for driving in the tracking direction.

[0004]

As described above, the conventional plural-lens mounting type objective lens driving device has a power supply means for supplying a current to the movable portion side. This power supply means is greatly deformed in conjunction with the objective lens switching operation. The restoring force from the deformed state to the initial state of the power supply means acts on the movable portion in proportion to the objective lens switching operation amount. Therefore, as the objective lens switching angle increases, the influence of the restoring force by the power supply means on the restoring force to the neutral position of the magnetic spring cannot be ignored, and the positioning accuracy of the objective lens deteriorates. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to solve the problem of deterioration of the positioning accuracy of an objective lens due to the restoring force of a power supply means in an objective lens driving device having a plurality of objective lenses. It is an object.

[0006]

SUMMARY OF THE INVENTION In order to solve such a problem, according to the present invention, a plurality of objective lenses for condensing a light beam, a lens holder for holding the objective lens, and an objective lens in a focus direction. A focus coil provided on the lens holder for driving, a tracking coil provided on the lens holder for driving the objective lens in the tracking direction, and a shaft for guiding the lens holder so as to slide and rotate. An objective lens driving device including a yoke and a plurality of magnets forming a magnetic circuit having a magnetic gap into which a focus coil and a tracking coil are inserted, wherein the yoke and the plurality of magnets are arranged or formed radially around a shaft on a lens holder. The magnetic material, and adjust the angle of the objective lens with respect to the angle of arrangement of the magnetic material around the axis of the shaft. To set the placement angle about the axis of the shaft to be different.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an objective lens driving device according to the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.
An embodiment will be described. FIG. 1 is a configuration explanatory view showing a first embodiment of an objective lens driving mechanism corresponding to a plurality of types of optical discs, and shows a state in which a first objective lens 2 is selected. 2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB of FIG. FIG. 4 is a configuration explanatory view showing a state in which a second objective lens 3 different from FIG. 1 is selected. FIG.
FIG. 3 is a cross-sectional view taken along a line, and shows a state where the optical disk is used by being built in a cartridge. FIG. 6 is an exploded perspective view of the configuration of the present embodiment. FIG. 7 is a state explanatory view of the present embodiment, and shows a state in which the first objective lens 2 is selected. FIG. 8 is a state explanatory view showing a state in which the second objective lens 3 is selected.

1 to 6, a first objective lens 2, a second objective lens 3, a magnetic body 4, a focus coil 8 and a tracking coil 9 are slidable and rotatable around a shaft 1. The movable portion is formed on the holder 7. The maximum length 15 of the movable portion is configured to be smaller than the corresponding cartridge opening 17 as shown in FIG. 5, and as shown in FIG. 1, the first objective lens 2 and the second objective lens 3 is provided so as to form a lens arrangement angle 12 around the axis of the shaft 1.
In this case, the objective lens arrangement angle 12 is set to be shifted to an angle smaller than substantially 90 °. 4 magnetic bodies 4
Are radially arranged at approximately 90 ° intervals about the axis of the shaft 1. The yoke 5 and the magnet 6 form a magnetic circuit, and the four magnets 6 facing the focus coil 8 and the four tracking coils 9 are magnetized in the radial direction, and are substantially equal to the arrangement angle of the magnetic body 4. The magnetic circuit arrangement angles 13 are the same. Since the magnetic flux density distribution in the circumferential direction around the magnetic body 4 becomes maximum near the center of the magnet 6 facing the magnetic body 4, the magnetic body 4 is magnetically balanced and stable near the center position of the magnet 6. The flow of magnetic flux in the height direction is
→ Magnetic body 4 → Inner part 5a of yoke 5 (inner yoke) → Outer part 5b of outer yoke 5 (outer yoke) → Magnetic body 4 is magnetically located above inner yoke 5a so as to form a magnetic loop with magnet 6. Produces balance and stabilizes. As a result, the entire movable section, the first objective lens 2 and the second objective lens 3 are stably and accurately positioned by the magnetic body 4 and the magnetic spring formed by the magnetic circuit. The FPC 10 connects the outside and the movable part so that the cross-sectional shape becomes substantially U-shaped. By supplying a predetermined current to the focus coil 8 and the tracking coil 9 via the FPC 10, each coil in the magnetic circuit can obtain a driving force called a framing force, and is integrated with the lens holder 7. The first objective lens 2 and the second objective lens 3 are movable in the height direction and the circumferential direction of the shaft 1. As a result, it is possible to condense the light beam incident on the first objective lens 2 from the rising mirror 11 on an optical disk (not shown). In the first objective lens 2, when an optical disk that cannot collect light is loaded, a rectangular wave-shaped current is instantaneously applied to the tracking coil 9, as shown in FIG. The third objective lens 3 is rotated so as to be disposed directly above the rising mirror 11, and the use of the second objective lens 3 enables light to be focused on the optical disk.

Next, the behavior at the time of the lens switching operation will be described with reference to FIGS.

In FIG. 7, the first objective lens 2 is located just above the rising mirror 11. From this state, the second type is used to support other types of optical discs.
When the objective lens 3 is selected, the lens holder 7 on which the first objective lens 2 and the second objective lens 3 are mounted is driven to rotate about the shaft 1 by the driving means (not shown). Since the movable portion is physically connected to the outside by the FPC 10, the amount of twist of the FPC 10 increases as the switching angle of the objective lens, that is, the objective lens arrangement angle 12 on the lens holder 7 increases. Since the torsion of the FPC 10 acts as a resistance to the movable part, the rotation angle of the movable part accompanying the objective lens switching operation is substantially 90 ° by the angle represented by the shift angle 19.
Will be less than. In the present invention, the shift angle 1
Since the objective lens arrangement angle 12 is set to be smaller than the magnetic circuit arrangement angle 13 by an angle corresponding to 9, the second objective lens 3 can be positioned directly above the rising mirror 11 as shown in FIG. it can.

As described above, according to the first embodiment of the present invention, the shift angle 19 caused by the resistance of the FPC 10 is obtained.
Only the objective lens arrangement angle 12 is set to be smaller than the magnetic circuit arrangement angle 13, so that it is possible to stably and highly accurately position a plurality of objective lenses directly above the rising mirror 11. It should be noted that higher precision positioning is possible by integrally molding the magnetic body with the lens holder.

Next, a description will be given of a second embodiment of the objective lens driving device according to the present invention. FIG. 9 is an explanatory diagram of the configuration of the second embodiment. The present embodiment is different from the above-described first embodiment in that two magnetic members 4 are formed, and the other configuration is the same, so detailed description is omitted. The two magnetic bodies 4 are arranged symmetrically with respect to the axis of the shaft 1. Magnetic circuit arrangement angle 13 in this case
Indicates the angle formed by the two magnets 6 facing the same magnetic body 4 with the axis of the shaft 1 when the first objective lens 2 and the second objective lens 3 are respectively selected. As in the first embodiment, by setting the objective lens arrangement angle 12 to be slightly smaller than the magnetic circuit arrangement angle 13, the first embodiment of the present invention described above is achieved.
The same effect as that of the embodiment can be obtained, and at the same time, the number of parts can be reduced and the efficiency at the time of assembly can be improved.

Next, a description will be given of a third embodiment of the objective lens driving device according to the present invention. FIG. 10 is an explanatory diagram of the configuration of the third embodiment. The present embodiment is different from the above-described first and second embodiments in that a substantially cross-shaped magnetic body 4 is provided instead of the magnetic body 4, and the other configuration is the same, so that the description is omitted. I do. Also in the present embodiment, the first
Similarly to the embodiment of FIG.
The objective lens arrangement angle 12 is set to be slightly shifted. Thus, the same effects as those of the first embodiment of the present invention described above can be obtained, and at the same time, the number of parts can be reduced and the efficiency at the time of assembly can be improved.

Next, a description will be given of a fourth embodiment of the objective lens driving device according to the present invention. FIG. 11 is an explanatory diagram of the configuration of the fourth embodiment. This embodiment is different from the above-described third embodiment in that a cutout portion is provided in a part of the magnetic body 18 in FIG. With this notch shape, it is possible to mount the objective lens 19 having a somewhat larger diameter. According to the present embodiment, the third
Similarly to the embodiment of FIG.
Since the objective lens arrangement angle 12 is set to be shifted slightly, the same effect as that of the first embodiment of the present invention described above can be obtained, and at the same time, the number of parts is reduced and the efficiency at the time of assembly is reduced. Can be achieved.

In the first to fourth embodiments, the method of supplying the current to the focus coil and the tracking coil by using the FPC has been described. However, the present invention does not limit the method of supplying current. For example, a method of supplying current using lead wires independently drawn from each terminal of the focus coil 8 and the tracking coil 9 may be used. In each of the descriptions, the magnetic circuit arrangement angle 13 corresponds to the objective lens arrangement angle 1
Although the case where 2 is shifted slightly is shown, when the direction of the resistance force of the feeding means is different from the above description, it is sufficient to cope with by shifting the objective lens arrangement angle 12 largely with respect to the magnetic circuit arrangement angle 13. Needless to say. Further, the number of objective lenses is not limited to two, and may be, for example, three or more. The description has been made using the case where the magnetic circuit arrangement angle 13 is set to approximately 90 °, but the magnetic circuit arrangement angle 13 is not limited to this.

[0017]

As described above, according to the present invention, in an objective lens driving device provided with a mechanism for switching and selecting two or more objective lenses to cope with a plurality of types of optical disks, a magnetic material and a magnetic circuit are provided. By displacing the lens arrangement angles of the two objective lenses on the lens holder with respect to the objective lens switching angle determined by the combination of
The position of the objective lens shifted by the resistance of the FPC can be appropriately corrected, and the objective lens can be positioned with high accuracy during the lens switching operation.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing a first embodiment of an objective lens driving device according to the present invention, showing a state in which a first objective lens 2 is selected.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a structural explanatory view showing a first embodiment of the objective lens driving device according to the present invention, and shows a state in which a second objective lens 3 is selected.

FIG. 5 is a cross-sectional view taken along line AA of FIG. 1, showing a state in which an optical disk mounted on a cartridge is used.

FIG. 6 is an exploded perspective view showing a first embodiment of the objective lens driving device according to the present invention.

FIG. 7 is a state explanatory view showing the first embodiment of the objective lens driving device according to the present invention, and shows a state in which the first objective lens 2 is selected.

FIG. 8 is a state explanatory view showing the first embodiment of the objective lens driving device according to the present invention, and shows a state where the second objective lens 3 is selected.

FIG. 9 is an explanatory diagram illustrating a configuration of a second embodiment of the objective lens driving device according to the present invention.

FIG. 10 is a configuration explanatory view showing a third embodiment of the objective lens driving device according to the present invention.

FIG. 11 is a structural explanatory view showing a fourth embodiment of the objective lens driving device according to the present invention.

[Explanation of symbols]

1 ... shaft, 2 ... first objective lens, 3 ...
2nd objective lens, 4 ... magnetic body, 5a ... inner yoke, 5b ... outer yoke, 6 ... magnet, 7 ... lens holder, 8 ... focus coil, 9 ... ..Tracking coil, 10 ... FP
C, 11: Start-up mirror, 12: Object lens arrangement angle, 13: Magnetic circuit arrangement angle, 14: Optical disk, 15: Maximum length of movable part, 16: Cartridge, 17 ... cartridge frontage, 18 ... magnetic material, 19 ... deviation angle

Continued on the front page (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Video Information Media Division (72) Inventor Shinro Inui 1410 Inada, Hitachinaka City, Ibaraki Prefecture Media Division (72) Inventor Naohiko Ochi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Video and Information Media Division (72) Inventor Ryuichiro Mizuno 1-chome Kitano, Majo, Mizusawa-shi, Iwate Prefecture Hitachi, Ltd. In media electronics

Claims (6)

[Claims] A plurality of objective lenses for converging a light beam on a plurality of types of optical discs having different recording densities or transparent substrate thicknesses; a lens holder for holding the objective lenses; A focus coil provided on the lens holder for driving in a focus direction, a tracking coil provided on the lens holder for driving the objective lens in a tracking direction, and the lens holder can slide and rotate. An objective lens driving device comprising: a shaft for guiding as described above; a yoke forming a magnetic circuit having a magnetic gap into which the focus coil and the tracking coil are inserted; and a plurality of magnets. A magnetic material radially arranged or formed around the shaft is provided, and the magnetic material is provided in front of the magnetic material. With respect to the arrangement angle around the axis of the shaft, the objective lens driving device, characterized in that the arrangement angle around the axis of the shaft of the plurality of objective lenses are set differently. 2. The object according to claim 1, wherein an arrangement angle of the magnetic body around the axis of the shaft is set to be larger than an arrangement angle of the plurality of objective lenses around the axis of the shaft. Lens drive. 3. The objective according to claim 1, wherein an arrangement angle of the magnetic body around the shaft axis is set smaller than an arrangement angle of the plurality of objective lenses around the shaft axis. Lens drive. 4. A plurality of objective lenses for condensing a light beam for a plurality of types of optical discs having different recording densities or transparent substrate thicknesses, a lens holder for holding the objective lenses, and the objective lens. A focus coil provided on the lens holder for driving in a focus direction, a tracking coil provided on the lens holder for driving the objective lens in a tracking direction, and the lens holder can slide and rotate. An objective lens driving device comprising: a shaft for guiding as described above; a yoke forming a magnetic circuit having a magnetic gap into which the focus coil and the tracking coil are inserted; and a plurality of magnets. A magnetic body radially arranged or formed around the shaft is provided, and the magnet is provided. With respect to the arrangement angle around the shaft axis, an objective lens driving device, characterized in that the arrangement angle around the axis of the shaft of the plurality of objective lenses are set differently. 5. The objective lens according to claim 4, wherein an arrangement angle of the magnet around the axis of the shaft is set to be larger than an arrangement angle of the plurality of objective lenses around the axis of the shaft. Drive. 6. The objective lens according to claim 4, wherein an arrangement angle of the magnet around the shaft axis is set smaller than an arrangement angle of the plurality of objective lenses around the shaft axis. Drive.