JPH11259885A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the device small in size and thin in thickness even though the device is constituted so that a disk and objective lenses are not brought into contant with each other in any case by providing a movement range restricting means setting so that movement ranges in a focusing direction of a lens holder are different in accordance with the objective lens to be selectively used. SOLUTION: Projection parts 5, 6 are respectively formed at positions where are axially symmetric with respect to the shaft 7 of a first objective lens 2 and a second objective lens 3 on the side of the upper surface of a lens holder 4. A cover is formed so as to cover the lens holder 4 and the protruding part 5 and the protruding part 6 are made so as to be respectively exposed from the notched part of the cover when the first objective lens 2 is selected and when the second objective lens 3 selected. Thus, even when an abnormality of the missing of servo or the like is generated and the lens holder 4 is moved to the side of the optical disk, the movement of the holder 4 is restricted because the protruding part 5 or 6 is abutted on the cover, it is never caused that first and second objective lenses 2, 3 are brought into contact with the optical disk.

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 apparatus for an optical disk apparatus for recording and / or reproducing signals on an optical disk, and more particularly to an objective lens driving apparatus using a plurality of objective lenses.

[0002]

2. Description of the Related Art In a recording and / or reproducing apparatus using an optical disk, it is required to establish high reliability with an increase in recording density. At the same time, devices that place importance on portability and space saving are required to further reduce the size and thickness of the device. In recent years, compact discs (hereinafter, CDs) have been widely distributed for various uses such as for music, karaoke, and computers. But CD
Since the amount of information that can be handled by a DVD is insufficient to handle high-quality and long-term image information, a new optical disk (for example, a DVD) having many times the information amount of a CD has been proposed and put into practical use. .

In a situation where a plurality of types of optical disks exist, a conventional optical disk (for example, C
An optical disk device that can use both D) and a new optical disk (for example, DVD) is generally desired. In view of such market demands, a number of optical disk devices capable of compatible reproduction of a plurality of types of optical disks have been proposed.
As an example, Japanese Patent Application Laid-Open No. 8-138261 discloses an objective lens driving device for an optical disk device that selects a plurality of objective lenses to record and / or reproduce information on a plurality of types of optical disks having different disk substrate thicknesses. Has been proposed.

[0004]

However, the above-described objective lens driving device has the following problems.

The optical disk apparatus has an optical system for accurately reading a signal recorded on the optical disk. These optical systems include a laser for generating a light beam and an objective for condensing the light beam on the recording surface of the disk. It comprises a lens and an objective lens driving device, a detector for detecting a light beam, and the like. Working distance (hereinafter, WD) specific to the objective lens
The distance between the lower surface of the disk and the upper surface of the objective lens represented by
In any case, a predetermined amount of gap is selected so that the optical disc and the objective lens do not come into contact with each other.

[0006] Here, in the objective lens driving device in the above-mentioned conventional technique, the relationship between the WD values of the objective lenses is not taken into consideration, so that when the WD values are different, the objective lens and the optical disk are not in contact with each other. In order to achieve this, it is necessary to sufficiently separate the objective lens and the optical disk. This makes it possible to avoid contact between the objective lens and the optical disk at the time of an abnormal operation such as a servo failure, but this has been an obstacle to miniaturization / thinning of the device itself. This adverse effect is particularly remarkable when the standard value of the surface runout of the optical disk itself is large.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and an objective lens driving apparatus for recording and / or reproducing information on and from a plurality of types of optical disks by mounting a plurality of objective lenses. It is an object of the present invention to reduce the size and thickness of the apparatus in any case in which the optical disc and the objective lens are not in contact with each other.

[0008]

In order to solve such a problem, the objective lens driving device according to the first aspect of the present invention focuses light beams on a plurality of types of optical disks having different recording densities or transparent substrate thicknesses. A plurality of objective lenses, a lens holder for holding the objective lens, a focus coil provided for the lens holder for driving the objective lens in the focus direction, and a lens coil for driving the objective lens in the tracking direction. A tracking coil, a shaft for guiding the lens holder so as to slide and rotate, and an outer yoke forming a magnetic gap into which the focus coil and the tracking coil are inserted;
An inner yoke, a plurality of magnets, and a cover formed so as to cover the lens holder and having a cutout portion that partially exposes the objective lens, and a focus direction of the lens holder according to an objective lens to be selectively used. A moving range restricting means for setting the moving range to be different is provided.

The objective lens driving device according to the second invention is characterized in that one or a plurality of convex portions provided on the upper portion of the lens holder constitute moving range limiting means.

[0010] In the objective lens driving device according to the third aspect of the present invention, the moving range limiting means is constituted by using a cover.

In the objective lens driving device according to a fourth aspect of the invention, the height of the plurality of convex portions is different.

In the objective lens driving device according to the fifth aspect of the present invention, the range of movement of the lens holder in the focus direction on the objective lens side where the standard value of the surface deflection of the optical disk is large is
The present invention is characterized in that it is configured to be set smaller than the focus direction moving range of the lens holder on the other objective lens side.

[0013]

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, the first embodiment of the present invention will be described with reference to FIGS.
An embodiment will be described. Here, FIG. 1 is a configuration explanatory view showing a first embodiment of an objective lens driving device corresponding to a plurality of types of optical discs, and shows a state where the first objective lens 2 is selected. FIG. 2 shows a state where the second objective lens 3 is selected. FIG. 3 shows a state without the cover 1 in FIG. FIG.
FIG. 4 is a cross-sectional view taken along a line, and shows a state where an optical disk 17 having a small standard value of the amount of runout is being reproduced above the disk position. FIG. 5 shows a state where the optical disk 17 in FIG. 4 is being reproduced below the disk position. FIG. 6 shows that the optical disc 17 and the first
3 shows a state in which the objective lens 2 is closest. FIG. 7 is a cross-sectional view taken along the line BB of FIG. 2, and shows a state in which the optical disk 18 having a large standard value of the surface runout is being reproduced above the disk position. FIG. 8 shows a state where the optical disk 18 in FIG. 7 is being reproduced below the disk position. FIG. 9 shows a state in which the servo deviation has occurred in FIG. 8 and the optical disk 18 and the second objective lens 3 having a large surface runout are closest to each other.

First, an outline of a two-lens actuator that uses two objective lenses by appropriately selecting them will be described.

In FIGS. 1 and 2, the first objective lens 2 and the second objective lens 3 exposed from the notch of the cover 1 are attached to a lens holder 4 around a shaft 7 (not shown). It is located above at an angle of approximately 90 °. At the time of reproducing information from the optical disk, a necessary objective lens is switched on the path of the light beam by using a lens switching mechanism described later, and an objective lens according to the optical disk to be used is selected. The first objective lens 2 can collect light on an optical disk 17 (not shown), and the second objective lens 3 can collect light on an optical disk 18 (not shown). Also, when comparing the standard values of the disk surface deflection amount of the optical disk 17 and the optical disk 18,
Is smaller in the standard value of the disk surface contact amount.

The first objective lens 2 and the second objective lens 3 have different working distances (hereinafter referred to as WD), which are gaps between the optical disk and the objective lens during use, and the WD value of the first objective lens 2 is the second. Is smaller than that of the objective lens 3. Convex portions 5 and 6 are formed on the upper surface side of the lens holder 4 at substantially axially symmetric positions with respect to the shafts 7 of the first objective lens 2 and the second objective lens 3, respectively, and the first objective lens 2 is selected. When the second objective lens 3 is selected, the convex portion 5 is exposed when it is set, and the convex portion 6 is exposed from the cutout portion of the cover 1.

3 and 4, a first objective lens 2, a second objective lens 3, a focus coil 8, four tracking coils 9, and four magnetic pieces 13 are fixed on a lens holder 4 and are movable. Part is formed. here,
The lens holder 4 is slidable and rotatable with respect to the shaft 7 in the axial direction and the circumferential direction. Each wire element of the focus coil 8 is fixedly wound around the outer periphery of the lens holder 4 in a cylindrical shape so as to be located in front of the magnet 12. The four tracking coils 9 are formed by forming four substantially rectangular winding portions on one line element. Also, one of the four sides of the tracking coil 9 is fixed to the front of the magnet 12 so as to be in the same winding direction, and has an arc shape such that the entire shape substantially matches the outer periphery of the lens holder 4. Is formed.

Each of the four magnetic members 13 has a size of about 9
It is fixed to the back side of the lens holder 4 so as to form 0 degree, and the upper side of the inner yoke 11 in the assembled state,
Further, it is configured to be located in front of the magnet 12. Further, the shaft 7, an outer yoke 10 having five rising portions, an inner yoke 11 having two arc-shaped rising portions, and four magnets 12 are fixedly integrated. Here, the shaft 7 is vertically fixed to the bottom surface of the outer yoke 10.

Four of the rising portions of the outer yoke 10 form an angle of about 90 degrees around the shaft 7, and the magnet 12
Are all directed to the shaft 7. The inner yoke 11 is raised from the outer yoke 10 such that the vicinity of the end of the arc shape faces the magnet 12. The outer yoke 10, the inner yoke 11, and the magnet 12 form a magnetic circuit. The objective lens driving device is assembled so that the focus coil 8 and the four tracking coils 9 are located in the gap between the inner yoke 11 and the magnet 12 facing each other.

The shaft 7 around the four magnetic bodies 13
The magnetic flux density distribution in the circumferential direction of
, The magnetic body 13 is magnetically balanced and stable near the center of the magnet 12. The flow of the magnetic flux in the height direction is
→ Magnetic body 13 → Inner yoke 11 → Outer yoke 1
0 → Because it forms a magnetic loop with the magnet 12,
The magnetic body 13 is magnetically balanced above the inner yoke 11 to be stable.

As a result, the entire movable portion including the first objective lens 2 and the second objective lens 3 is stable and highly accurate in the focusing direction and the tracking direction by the magnetic body 13 and the magnetic spring formed by the magnetic circuit. Is positioned at Here, since the angle formed at the time of lens switching is set to approximately 90 degrees, the magnetic balance is maintained even after the lens switching operation.

The cover 1 is formed so as to cover the movable part and the fixed part of the objective lens driving device. The first objective lens 2, the second objective lens 3, the convex part 5, and any one of the convex parts Only one of them is exposed from the notch.

The FPC 15 connects the rising portion of the outer yoke 10 and the movable portion including the lens holder 4 so that the cross-sectional shape is substantially U-shaped. By supplying a predetermined current to the focus coil 8 and the tracking coil 9 via the FPC 15, each coil in the magnetic circuit can obtain a driving force called a framing force, and is integrated with the lens holder 4. The first objective lens 2 and the second objective lens 3 are movable in the axial direction and the circumferential direction of the shaft 7.

At this time, since the FPC 15 has sufficiently low rigidity, the influence on the operation of the movable portion is extremely small. Regarding the movable range in the axial direction of the shaft 7, that is, in the focus direction, the upper side is restricted by the convex portion 5 or the convex portion 6,
The lower side is regulated by the lowermost surface of the bearing portion of the lens holder 4. The mirror 14 is held at a predetermined position on the optical axis and changes the optical axis direction of the light beam 16 by approximately 90 degrees so that the first objective lens 2 can focus the light beam 16 on the optical disk 17. An optical system is formed.

When the first objective lens 2 is loaded with an optical disk 18 of a type that cannot collect light, an instantaneous rectangular wave-shaped current is applied to the tracking coil 9 so that the tracking coil 9 is turned on. 8 and 9, the second objective lens 3 is rotated so as to be disposed directly above the mirror 14, and the light is condensed on the optical disk 18 by using the second objective lens 3. It is possible.

Next, the operation of the objective lens driving device when reproducing information from a plurality of types of optical discs will be described with reference to FIGS.

FIG. 4 shows a state in which a light beam 16 is condensed on an optical disk 17 having a small amount of disk surface deflection to reproduce information. Since the position of the optical disc 17 in the focus direction, that is, the height direction is near the upper limit of the design, the height position of the first objective lens 2 is also near the upper side of the movable range. The space between the upper surface of a certain cover 1 and the lowermost surface of the optical disk 17 is sufficiently ensured, and they do not come into contact with each other.

FIG. 5 shows a state where the height position of the optical disk 17 is the lowest. The entire movable part including the first objective lens 2 moves downward as compared with FIG.
Since the WD value, which is the gap between the objective lens 2 and the optical disc 17, is balanced at a position similar to that in FIG. 4, the optical disc 17 and the cover 1 do not come into contact with each other.

FIG. 6 shows a state in which an abnormality such as a servo error has occurred in the state of FIG. 5 and the movable portion is at the uppermost end position of the movable range. The upward movement of the entire movable part including the lens holder 4 is restricted by the contact between the cover 1 and the convex part 6. At this time, the first objective lens 2 and the cover 1 do not come into contact with the optical disc 17.

Next, FIG. 7 shows a state in which the light beam 16 is condensed on the optical disk 18 having a large standard value of the disk surface deflection and the information is reproduced. Since the position in the focus direction, that is, the height direction of the optical disc 18 is near the upper limit of the design, the height position of the second objective lens 3 is also near the upper limit of the movable range. Here, the space between the upper surface of the cover 1, the second objective lens 3, the upper surface, and the lowermost surface of the optical disk 18 is sufficiently ensured.

FIG. 8 shows a state where the height position of the optical disk 18 is the lowest. Compared to FIG. 7, the entire movable part including the second objective lens 3 has moved downward,
W which is a gap between the second objective lens 3 and the optical disc 18
In a position where the D value becomes a value similar to that in FIG. 7, there is no balance between the optical disk 18 and the objective lens driving device itself.

FIG. 9 shows a state in which an abnormality such as a servo error has occurred in the state of FIG. 8 and the movable part is at the uppermost end position of the movable range. Here, since the height of the convex portion 6 is set to be higher than that of the convex portion 5 by an amount corresponding to the difference in the standard value of the disk surface runout, the height is regulated by the contact between the cover 1 and the convex portion 6. The movable range of the entire movable portion including the lens holder 4 in the upward direction is lower than the state in which the first objective lens 2 is selected.

Therefore, during reproduction of the optical disk 18 having a large standard value of the disk surface shake amount, even if an error such as a servo deviation occurs, the second objective lens 3 and the cover 1 do not come into contact with each other, and The information can be reproduced without damage.

Although the present embodiment has been described with respect to the reproduction of information from an optical disk, it goes without saying that the present invention may be used for recording information on an optical disk.

[0036]

As described above, according to the present invention, in an objective lens driving device for selecting and using two or more objective lenses to cope with a plurality of types of optical discs, the objective lens driving device is movable according to the objective lens used. Since the movable range in the focus direction of the unit is set, the apparatus can be made smaller and thinner without the optical disc and the objective lens coming into contact with each other.

[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.

FIG. 2 is an explanatory diagram showing the configuration of FIG.

FIG. 3 is a view showing a state without a cover 1 in FIG. 1;

FIG. 4 is a cross-sectional view taken along line AA of FIG.

FIG. 5 is a cross-sectional view showing a state where the optical disc 17 is being reproduced below the disc position in FIG.

6 is a diagram showing an optical disk 1 in which a servo error occurs in FIG.
FIG. 7 is a cross-sectional view illustrating a state in which the first objective lens 2 is closest to the first objective lens 7.

7 is a cross-sectional view taken along the line BB of FIG. 2 and is a cross-sectional view showing a state in which an optical disk 18 having a large standard value of a surface runout is being reproduced above the disk position.

FIG. 8 is a cross-sectional view showing a state where the optical disk 18 is being reproduced below the disk position in FIG.

9 is a diagram showing an optical disk 1 in which a servo error occurs in FIG.
FIG. 9 is a cross-sectional view showing a state in which the second objective lens 3 is closest to the second objective lens 8.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cover, 2 ... 1st objective lens, 3 ... 2nd objective lens, 4 ... Lens holder, 5 ... Convex part, 6 ... Convex part, 7 ... Shaft, 8 ... Focus coil, 9 ...
Tracking coil, 10 ... outer yoke, 11
... inner yoke, 12 ... magnet, 13 ...
Magnetic material, 14 ... Mirror, 15 ... FP
C, 16: light beam, 17: optical disk,
18 Optical disk.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division of Hitachi, Ltd. (72) Inventor Naohiko Ochi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Co., Ltd. Inside (72) Inventor Michio Hataki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (72) Inventor Ryuichiro Mizuno 1st Kitano, Majo, Mijosawa City, Iwate Prefecture Inside Hitachi Media Electronics Co., Ltd. (72) Hidenao Saito 1st Kitano, Makino Mizusawa City, Iwate Prefecture Street Co., Ltd. Scan in

Claims (5)

[Claims] 1. 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 lens, and a focusing direction for the objective lens. A focus coil provided on the lens holder that drives the objective lens in a tracking direction; a tracking coil provided on the lens holder that drives the objective lens in a tracking direction; and a shaft that guides the lens holder so as to slide and rotate. An outer yoke, an inner yoke, and a plurality of magnets forming a magnetic gap into which the focus coil and the tracking coil are inserted; and a magnet formed to cover the lens holder and partially exposing the objective lens. An objective lens driving device provided with a cover having a notch, Depending on the lens, the objective lens driving device, wherein the focus movement range of the lens holder is provided with a moving range limiting means for setting differently. 2. The objective lens driving device according to claim 1, wherein said moving range limiting means is constituted by using one or a plurality of convex portions provided on an upper portion of said lens holder. 3. The objective lens driving device according to claim 1, wherein said moving range limiting means is constituted by using said cover. 4. The objective lens driving device according to claim 1, wherein the plurality of projections have different heights. 5. The moving range of the focus direction of the lens holder on the side of the objective lens used for the optical disc having a large standard value of the amount of deflection of the disc surface is defined as the moving range of the focus direction of the lens holder on the side of the other objective lens. 5. The objective lens driving device according to claim 1, wherein the objective lens driving device is configured to be set to be relatively small.