JPH06180847A - Device for detecting objective lens displacement - Google Patents

Abstract

PURPOSE:To detect the displacement amount of an objective lens with high precision by preventing a useless beam from being made incident on a light receiving element. CONSTITUTION:A supporting member 13 supporting a bobbin 1 placing an objective lens 3 in a central part and provided with a focusing coil 4 and a tracking coil 5 on a side surface with a leaf spring 11 and a detection unit 20 provided with a light emitting element 22 and the light receiving element 23 are placed on an actuator base 24. At this time, a light shielding plate 16 having a slit 16b provided on the bobbin 1 is placed between the light emitting element 22 and the light receiving element 23, and further, a light shielding wall 10 erected on the bobbin 1 is placed between the objective lens 3 and the light emitting element 22. By the light shielding wall 10, scattered beams due to an optical disk are shielded, and the incidence of the beam on the light receiving element 23 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens actuator applied to an optical pickup for recording / reproducing on / from an optical information recording medium such as an optical disk or a magneto-optical disk, and more particularly to this objective lens actuator. The present invention relates to an objective lens displacement detection device that detects the amount of movement of an objective lens by an actuator.

[0002]

2. Description of the Related Art As an example of this type of technology, Japanese Patent Laid-Open No.
There is a technology described in Japanese Patent No. 42635. This technique holds the objective lens and detects the light emitted from the light irradiator attached to the lens barrel around which the coil is wound, by the photodetector, and The displacement is detected.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
A technique for detecting the displacement of an objective lens by using an optical means, such as the technique described in Japanese Patent Laid-Open Publication, has been conventionally known.

However, since the light receiving element for detecting the displacement of the objective lens is installed in the vicinity of the objective lens, the reflected light of the convergent light applied to the optical disc which is the optical information recording medium is one. There is a possibility that the light is partially scattered and the scattered light enters the light receiving element. Furthermore, there is a possibility that the light incident from the outside may enter the light receiving element, so that the signal from the light receiving element may be inaccurate.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an objective lens displacement detection device which prevents unnecessary light from entering a light receiving element.

[0006]

In order to achieve the above object, the present invention moves an objective lens that forms a light spot on an information recording surface of an optical information recording medium and a bobbin that holds the objective lens. In an objective lens displacement detection device provided in an objective lens actuator having an actuator for performing a focusing operation or a tracking operation, for detecting a displacement of the objective lens due to the operation, a slit is formed on a surface and the objective lens displacement detection apparatus is provided on the bobbin. A light-shielding plate, a light source that irradiates the light-shielding plate surface with light, a light-receiving element that receives the light from the light source that has passed through the slit, and to prevent unnecessary light from entering the light-receiving element. And a light blocking wall provided on the bobbin.

The light shielding wall is provided between the objective lens and the light receiving element.

Further, the light receiving element is installed in a region formed by two straight lines connecting both ends of the light shielding plate with the optical axis of the objective lens as a center.

Further, the light shielding wall is made of a flexible material.

In addition, a notch is formed in a portion of the cover that protects the objective lens actuator, the portion corresponding to the light shielding wall.

Further, the light shielding surface of the light shielding wall is inclined to the outside of the bobbin.

[0012]

By adopting the above-mentioned structure, unnecessary light which is about to enter the light receiving element is blocked by the light shielding wall.

Further, since the light shielding wall is provided between the objective lens and the light receiving element, the light shielding wall shields the light partially scattered by the reflected light from the optical information recording medium.

Further, since the light receiving element is provided in the region formed by the two straight lines passing through both ends of the light shielding plate with the optical axis of the objective lens as the center, the light receiving element is a portion shaded by the light shielding wall. Located in.

Further, since the light shielding wall is made of a flexible material, it does not damage the surface thereof even if it comes into contact with the optical information recording medium.

Further, since the light shielding wall is arranged in the cutout portion of the cover of the objective lens actuator, unnecessary light from the outside is blocked by this cover, and the light shielding wall is used during the focusing operation or tracking operation of the objective lens. Does not touch the cover because it moves in the notch.

Further, since the light shielding wall has the inclined surface, when the optical information recording medium is rotated, the air inside the light shielding wall escapes to the outside through the slope of the light shielding wall.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is an exploded perspective view showing the configuration of an embodiment of the present invention, and FIG. 2 shows the bobbin of FIG. 1 and its supporting structure.

In FIG. 2, 1 indicates a bobbin. The bobbin 1 is attached to the bobbin case 2, the objective lens 3 placed in the center of the bobbin case 2, the focusing coil 4 wound around the side surface of the bobbin case 2, and the surface of the focusing coil 4. And a tracking coil 5.

Reference numeral 6 denotes an objective lens mounting table formed at the edge of a through hole formed in the center of the bobbin case 2, and the objective lens 3 is mounted on this objective lens mounting table 6. Reference numeral 7 is a yoke hole formed on both sides of the objective lens mounting table 6, 8 is an extended portion provided at each of four outer edges of the upper and lower collar portions A and B of the bobbin case 2, and a total of four extended portions.
Reference numeral 9 denotes a through hole provided on the surface of the extending portion 8, and 10 denotes a light shielding wall protruding from a part of the outer edge of the collar portion A.

Reference numeral 11 indicates a leaf spring. The leaf spring 11 includes a fixed portion 11a having a relatively wide width, deformed portions 11b provided at both ends of the fixed portion 11a, and a U-shaped connecting portion 11c provided at the center.
It is formed in a substantially U shape in a plan view. Further, the deforming portion 11b
11d has a hole 11d formed at its free end, and holes 11e are formed at both ends of the fixed portion 11a serving as a fixed end. Further, one of the two holes 11e, 11e is formed as a long hole. The thickness of the leaf spring 11 is about several tens of microns, and the width of the deformed portion 11b is about several times the thickness. The free end of the deformable portion 11b can move in the focusing direction and the tracking direction. Denoted at 12 is a damping member made of butyl rubber attached to the deformed portion 11b. This damping member 12
Serves to suppress the amplitude of resonance caused by the leaf spring 11.

Reference numeral 13 indicates a support member for the bobbin 1. Support member
Reference numeral 13 is composed of a base portion C and arm portions D and E at both ends thereof, and has a substantially U-shape in plan view. Reference numeral 14 denotes a screw hole formed at the tip of the arm portion D and a corner portion of the base portion C for screwing and fixing the support member 13 to an actuator base described later. Reference numeral 15 denotes holes corresponding to the holes 11e, 11e of the leaf spring 11 formed on the upper surface of the base portion C. Also,
Similarly, holes 15 and 15 are formed on the lower surface of the base portion C.

Reference numeral 16 denotes a light shielding plate, and 17 denotes a light shielding plate balancer.
The light-shielding plate 16 and the light-shielding plate balancer 17 are formed with a convex portion 16a and a convex portion 17a whose width is substantially equal to the width between the extending portions 8 in the same direction as the optical axis of the objective lens 3. further,
A slit 16b extending in the same direction as the optical axis of the objective lens 3 is formed on the surface of the light shielding plate 16.

Further, the through holes 9, 9 of the extending portions 8, 8 provided in the collar portion A of the bobbin 1 have holes formed at the free ends of the leaf springs 11.
The pin 18 is fitted through 11d and 11d, and the free end of the leaf spring 11 is fixed to the extending portions 8 and 8 with an adhesive. On the other hand, the leaf springs 1 are also similarly provided for the extending portions 8 and 8 provided on the collar portion B.
The free end of 1 is fixed.

The fixed portion 11 which is the fixed end of the leaf spring 11
The a is fixed to the support member 13 by a leaf spring fixing bar 19. That is, the two pieces provided at both ends of the leaf spring fixing bar 19
The two pins 19a and 19a are fitted into the holes 15 and 15 of the support member 13 through the holes 11e and 11e of the leaf spring 11, and the leaf spring fixing bar 19
Finely move and position. Further, an adhesive agent is used to fix the fixing portion 11 of the leaf spring 11 between the leaf spring fixing bar 19 and the supporting member 13.
a is glued and fixed. The fixing portion 11a of the leaf spring 11 is attached to the support member 13.
After being bonded and fixed, the connecting portion 11c is cut off.

Further, the light-shielding plate 16 is installed by fixing the convex portion 16a of the light-shielding plate 16 between the one extending portions 8, 8 located in the same direction as the optical axis of the objective lens 3. . At this time, the slit 16b is positioned such that the direction of the hole of the slit 16b is perpendicular to the optical axis of the objective lens 3. Further, in order to maintain the balance with the light shielding plate 16, the convex portion 17a of the light shielding plate balance 17 is fixed between the other extending portions 8 and 8 so that the light shielding plate balancer 17 is installed.

In FIG. 1, reference numeral 20 denotes a detection unit for detecting displacement of the position of the objective lens 3. This detection unit
The light emitting element 22 and the light receiving element 23 are fixed in the housing 21 so as to face each other.

Reference numeral 24 represents an actuator base. This actuator base 24 has an objective lens 3 provided at the center.
A circular hole 25 through which the laser light incident on the inner hole 26, an inner yoke 26 erected on the edge of the circular hole 25, outer yokes 27, 27 erected to face the inner yokes 26, 26, and an inner yoke. Permanent magnet 28 installed on the surface of outer yoke 27, 27 facing 26, 26
It is composed of and. 29 is the actuator base
24 is a mounting hole formed on the surface corresponding to the hole 15 of the support member 13, and 30 is a long hole for mounting the detection unit 20. Further, 31 indicates an upper yoke.

The bobbin unit having the bobbin 1 fixed to the support member 13 via the leaf spring 11 is placed on the actuator base 24. At this time, the support member 13
The objective lens 3 is fixed to a carriage base (not shown) for seeking movement of the objective lens 3 by a screw 32 which is inserted through the hole 15 and the mounting hole 29 of the actuator base 24. Also,
The detection unit 20 is also fixed on the actuator base 24 from below the elongated hole 30 with screws 33.

When the bobbin unit and the detection unit 20 are fixed to the actuator base 24, the inner yoke 26 is loosely fitted in the yoke hole 7 of the bobbin 1, and the upper yoke 31 is attached to the uppermost portion of the inner yoke 26. . In addition, the permanent magnet 28 faces the tracking coil 5, and
The slit 16b is located between the light emitting element 22 and the light receiving element 23.

FIG. 3 is an exploded perspective view showing the structure of the detection unit 20, 21a is a gap for slidably installing the light emitting element 22 in the housing 21, and 21b is a light receiving element 23 formed in the housing 21. The recessed part to mount is shown. Reference numeral 34 denotes a guide plate that abuts below the guide surface of the housing 21 to position the light emitting element 22. The guide plate 34 allows the light emitting element 22 to slide so that the light receiving element
It is kept parallel to the light receiving surfaces 23a and 23b of 23. Light receiving element
23 is provided with two light receiving surfaces 23a and 23b, and the dividing line 23c
At the boundary, the amount of light emitted from the light emitting element 22 which is independently narrowed down by the slit 16b is detected. Then, the position of the objective lens 3 in the tracking direction is detected by the output difference between the two light receiving surfaces 23a and 23b.

When the detection unit 20 is fixed to the actuator base 24, the slit light is adjusted in position so that the slit light irradiates the light receiving surfaces 23a and 23b symmetrically and uniformly with the dividing line 23c as an axis.

FIG. 4 is a schematic plan view of FIG. As shown in FIG. 4, the light-receiving surfaces 23a and 23b are installed within a region of an angle θ ₁ formed from both ends of the light shielding wall 10 with the optical axis of the objective lens 3 as the center. The angle θ ₂ formed from the light receiving surfaces 23a and 23b about the optical axis of the objective lens 3 has a relationship of θ ₁ > θ ₂ compared with the angle θ ₁ .

FIG. 5 is a perspective view showing a state in which a cover for blocking the external light incident on the objective lens actuator shown in FIG. 1 is attached, 35 is a cover, and 35a is the convergent light of the objective lens 3. A hole portion, 35b is a hole portion in which the upper yoke 31 is loosely fitted, and a reference numeral 35c is a notch in which the light shielding wall 10 is located, which is formed by notching a part of the hole portion 35a.

The hole 35b and the notch 35c formed in the cover 35 are formed in such a size that the upper yoke 31 and the light shielding wall 10 do not come into contact with the cover 35 during the focusing operation or the tracking operation of the objective lens 3. There is.

In the present embodiment configured as described above, the optical disc M directed to the light receiving element 23 as shown in FIG.
The laser light L scattered by is blocked by the light shielding wall 10. Further, the light from the outside is blocked by the cover 35. Therefore, since the unnecessary light does not enter the light receiving element 23, the displacement of the objective lens 3 is accurately detected.

Further, as shown in FIG. 4, since the light receiving element 23 is arranged in the area shaded by the light shielding wall 10, the scattered light by the optical disk M is surely blocked.

7 to 9 are perspective views showing another structure of the light shielding wall 10 according to the present embodiment. The light shielding wall 10 shown in FIG. 7 is composed of a brush 36 whose member is soft hair. It is a thing. Further, the light shielding wall 10 shown in FIG. 8 is made of a sponge 37.

As described above, since the light shielding wall 10 is made of a flexible material, it is possible to prevent the surface of the optical disc M from being damaged when the optical disc M comes into contact with the light shielding wall 10.

Further, as shown in FIG. 9, by tilting the light shielding wall 10 toward the outer peripheral side of the optical disc M, the air on the inner peripheral side of the optical disc M during rotation can easily escape to the outside. Therefore, the generation of air flow near the objective lens 3 is prevented, and dust is unlikely to adhere to the air. Further, even if the light shielding wall 10 is not inclined, the same effect can be obtained by inclining the light shielding surface of the light shielding wall 10.

[0041]

The present invention constructed as described above has the following effects.

According to the structure of claim 1, since the light shielded from the light reflected from the objective lens by the optical information recording medium and directed toward a part of the light receiving element, the light unnecessary for the light receiving element is generated. It will not be incident,
It is possible to detect the displacement of the objective lens with high accuracy.

According to the second aspect of the present invention, since the light shielding wall is provided in the range that blocks the scattered light of the optical information recording medium which is about to enter the light receiving element, the weight increase of the bobbin due to the light shielding wall is minimized. Is possible.

According to the third aspect of the invention, since the light receiving element is located in the shadowed portion of the light shielding wall, the scattered light from the optical information recording medium is surely blocked, and the scattered light is incident on the light receiving element. It can be prevented more reliably.

According to the structure of claim 4, even if the light-shielding wall comes into contact with the optical information recording medium, the surface of the medium is not damaged, so that the height of the light-shielding wall can be increased. It is possible to effectively prevent scattered light from entering the light receiving element.

According to the structure of claim 5, it is possible to prevent external light from entering through the gap between the cover and the light shielding wall and entering the light receiving element.

According to the structure of claim 6, since the light shielding wall is provided with the inclined surface, it is possible to prevent an air flow from being generated in the vicinity of the objective lens when the optical information recording medium is rotated, and dust in the air is generated on the surface of the objective lens. Can be prevented from adhering to.
Further, since the area where the light receiving element can be shielded is also increased, it is possible to effectively shield the light.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of an objective lens actuator according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing the configuration of the bobbin of FIG. 1 and its surroundings.

FIG. 3 is an exploded perspective view showing a configuration of a detection unit.

FIG. 4 is a plan view of FIG.

5 is a perspective view showing a state in which a cover is provided in the configuration of FIG.

FIG. 6 is an explanatory diagram for explaining the operation of the present embodiment.

FIG. 7 is a perspective view showing another configuration of the light shielding wall according to the present embodiment.

FIG. 8 is a perspective view showing another configuration of the light shielding wall according to the present embodiment.

FIG. 9 is a plan view showing the outline of another configuration of the light shielding wall according to the present embodiment.

[Explanation of symbols]

1 ... Bobbin, 3 ... Objective lens, 4 ... Focusing coil, 5 ... Tracking coil, 10 ... Light shielding wall, 11 ... Leaf spring, 13 ... Support member, 16 ... Light shielding plate,
16b ... slit, 20 ... detection unit, 22 ... light emitting element, 23 ... light receiving element, 24 ... actuator base, 35
… Cover, 35c… Notch, 36… Brush, 37… Sponge.

Claims (6)

[Claims] 1. An objective lens actuator having an objective lens for forming a light spot on an information recording surface of an optical information recording medium and an actuator for moving a bobbin holding the objective lens to perform a focusing operation or a tracking operation. An objective lens displacement detection device provided for detecting displacement of the objective lens by the operation, wherein a slit is formed on a surface of the objective lens, and a light shielding plate provided on the bobbin, and a light source for irradiating light on the surface of the light shielding plate. And a light-receiving element that receives light from the light source that has passed through the slit, and a light-shielding wall provided on the bobbin to prevent unnecessary light from entering the light-receiving element. Objective lens displacement detection device. 2. The objective lens displacement detection device according to claim 1, wherein the light shielding wall is provided between the objective lens and the light receiving element. 3. The light receiving element is installed in a region formed by two straight lines connecting both ends of the light shielding plate with the optical axis of the objective lens as a center. The objective lens displacement detection device described. 4. The objective lens displacement detection device according to claim 1, wherein the light shielding wall is made of a flexible material. 5. The objective lens displacement detection device according to claim 1, wherein a notch is formed in a portion of the cover that protects the objective lens actuator, the portion corresponding to the light shielding wall. 6. The objective lens displacement detecting device according to claim 1, wherein the light shielding surface of the light shielding wall is inclined to the outside of the bobbin.