JPH01173333A - Device for driving objective lens - Google Patents

Abstract

PURPOSE:To oscillate a movable part without adding excessive force to a flexible oscillating part by providing a driving coil, which is arranged in a magnetic circuit,in an outer side than the center of gravity from the oscillating supporting point of the movable part to include an objective lens. CONSTITUTION:When a tracking coil 8 is electrified, an objective lens holding member 2 is oscillated in a tracking direction (X-direction) with an oscillating hinge part 15 as the supporting point. Thus, the tracking of an optical beam, which is radiated to an optical disk, can be adjusted through an objective lens 1. When focus coils 5a and 5b are electrified, the member 2 is parallelly moved in a focus direction (Z-direction) by a parallel link mechanism with a link hinge part 16 of a member 3. Thus, the focus of the optical beam, which is radiated to the optical disk, can be adjusted through the objective lens 1. In case of the tracking adjustment, electromagnetic force to be received by the tracking coil 8 is operated in the outer side than the center of gravity in the movable part which is composed of the lens 1 and the member 2, and the movable part is oscillated naturally with an oscillating hinge part 15 as the supporting point.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an objective lens drive device that adjusts the irradiation position of a light beam by displacing an objective lens in an optical pickup used for an optical disk device, a hologram device, etc. It is related to.

[Conventional technology]

An optical disk device is capable of recording and reproducing by selecting an arbitrary track by moving the entire optical pickup in the tracking direction of a rotating optical disk (radial direction of the optical disk). The optical pickup also includes an objective lens drive device that adjusts the irradiation position of the light beam by subtly displacing the objective lens.

This objective lens driving device adjusts the focus of the light beam by displacing the objective lens in the optical axis direction, and also performs tracking by displacing the objective lens in the tracking direction on a plane perpendicular to the optical axis. This is for making adjustments.

A conventional objective lens driving device will be explained based on FIGS. 8 and 9.

The objective lens l has an optical system arranged inside a cylinder. This objective lens 1 is held by an objective lens holding member 2 with its periphery fixed.

One end of the objective lens holding member 2 in a direction (Y direction) perpendicular to the tracking direction (X direction in FIG. 8) is supported by a raised portion 4a of a substrate 4 via a movable support member 3. This substrate 4 is attached to the tip of an optical pickup main body (not shown), and is configured to irradiate a light beam onto an optical disk through an objective lens 1. At both ends of the objective lens holding member 2 in the tracking direction (X direction), driving coils 5, 5 each consisting of a tracking coil 5a and a focus coil 5b are provided. Also, the tracking direction (X
Magnets 6 are arranged with gaps on both sides of the direction (Y direction) perpendicular to the above direction. The magnets 6, 6 are supported by both rising ends 7a, 7b of a yoke 7 fixed to the substrate 4, forming a magnetic circuit. Therefore, when the tracking coils 5a and 5a are energized,
The objective lens holding member 2 receives electromagnetic force in the tracking direction (X direction). This tracking direction is
This corresponds to the radial direction of an optical disk (not shown) on which a light beam is irradiated through the objective lens 1. Furthermore, when the focus coils 5b are energized, the objective lens holding member 2 receives electromagnetic force in the focus direction (X direction in FIG. 9). This focus direction coincides with the optical axis direction of the objective lens 1.

The structure of the movable support member 3 will be explained based on FIGS. 4 and 5.

The movable support member 3 is formed by integrally molding resin, or by molding resin and metal integrally by insert molding or the like, and includes a fixed part 11, an intermediate support part 12, and connecting parts 13 and 13.
and each part of the support section 14. The fixing part 11 is a square bar long in the tracking direction (X direction), and is fixed to the substrate 4 by attaching both ends to the rising part 4a, as shown in FIG. The intermediate support portion 12 is coupled to the fixed portion 11 via a swinging hinge portion 15 formed at the center of the side surface. The swinging hinge portion 15 is arranged in the focus direction (X
It is a constricted part of the resin that is formed long in the direction), and the intermediate support part 12 side is a plane (X-Y plane) orthogonal to the focus direction.
It has the flexibility to be able to swing on the top. Support part 14
is joined to this intermediate support portion 12 via connecting portions 13. The connecting portions 13 are arranged to connect the intermediate support portion 12 and the support portion 14 at the upper and lower sides of the focus direction (two directions), respectively. In addition, each connecting portion 13
The intermediate support portion 12 and the support portion 14 are coupled via link hinge portions 16, respectively. The link hinge portion 16 is a constricted portion of resin that is long (formed) in the tracking direction (X direction), and is configured such that each joint portion can swing on a plane (Y-2 plane) orthogonal to the tracking direction. It has flexibility. Therefore, the intermediate support part 12 and the connection part 13
・13 and the support part 14 are connected to this link hinge part 16...
・Constitutes a parallel link mechanism. Support part 14
As shown in FIG. 8, one end of the objective lens holding member 2 in the direction (Y direction) perpendicular to the tracking direction is fixedly supported.

With the above configuration, the movable support member 3 has the intermediate support portion 12, the connecting portions 13, 13 and the support portion 14 swingable with respect to the fixed portion 11 using the swing hinge portion 15 as a fulcrum, as shown in FIG. Become. Moreover, as shown in FIG. 7, the support part 14 can be moved parallel to the fixed part 11 and intermediate support part 12 side by the parallel link mechanism connected by the link hinge parts 16 . The objective lens holding member 2 supported by the substrate 4 via the movable support member 3 is movable on a plane (X-Y plane) perpendicular to the focus direction (X direction), and is also movable in the focus direction. It becomes possible to move in parallel.

Therefore, the objective lens driving device swings the objective lens holding member 2 in the tracking direction (X direction) by appropriately energizing the tracking coils 5a, 5a, and tracks the light beam irradiated through the objective lens 1. can be adjusted. Also, focus coil 5
By appropriately energizing b and 5b, the objective lens holding member 2 is moved in parallel in the focus direction (X direction),
The focus of the light beam irradiated through the objective lens 1 can be adjusted.

Here, when performing tracking adjustment or focus adjustment, the irradiation angle of the light beam irradiated through the objective lens 1 must not change. Therefore, during focus adjustment, the optical axis of the objective lens 1 is kept parallel by moving the objective lens holding member 2 in parallel using a parallel link mechanism.

However, if the objective lens 1 is displaced along a plane (X-Y plane) perpendicular to the focus direction (two directions) during tracking adjustment, the optical axis will not be tilted.

Therefore, in the tracking adjustment, the objective lens holding member 2 is displaced by simple rocking rather than parallel movement that requires a complicated mechanism.

Further, it is best to perform such rocking for tracking adjustment according to the structure of an ideal bearing. However, just realizing the structure of practical bearings requires high processing precision and strict maintenance management, which has the disadvantage of increasing product costs and complicating maintenance. Conventionally, such drawbacks have been solved by adopting a structure in which the objective lens holding member 2 is supported via the flexible swinging hinge portion 15 of the movable support member 3 integrally molded as described above. is being removed.

Furthermore, when performing parallel movement for focus adjustment,
Applying a force to the center of gravity of the objective lens holding member 2 including the objective lens 1 is an ideal driving method that does not apply unreasonable force to the parallel link mechanism. For this reason, the focus coils 5b and 5b are arranged in a magnetic circuit consisting of the focus coils 5b and the magnets 6... and the yokes 7 and 7.
5b is provided at a position to sandwich the optical axis of the objective lens 1, so that an electromagnetic force in the focus direction (Z direction) acts near the center of gravity of the objective lens holding member 2 including the objective lens 1. .

[Problem that the invention seeks to solve]

However, the conventional objective lens drive device uses a magnet 6.
... and the yokes 7, 7 are also used for tracking adjustment, and the tracking coils 5a, 5a disposed here are also placed in positions that sandwich the objective lens 1, and this objective lens l is An electromagnetic force in the tracking direction (X direction) was made to act near the center of gravity of the objective lens holding member 2. Therefore, the objective lens holding member 2 tends to move in parallel along the tracking direction (X direction) due to the force acting on its center of gravity.

Therefore, when the objective lens holding member 2 is displaced in the swinging direction by the movable support member 3, an unreasonable force is applied to the flexible swinging hinge portion 15. Therefore, when the objective lens 1 is repeatedly driven to swing for tracking adjustment, a sub-resonance as shown by a broken line circle A appears in the frequency characteristics, as shown in FIG. If such sub-resonance occurs, unless the tracking servo band of the objective lens drive device is widened or complicated control is performed,
Tracking adjustment could not be performed reliably.

Therefore, the conventional objective lens driving device has the problem that the frequency band of servo control must be expanded or complicated control must be performed due to the sub-resonance that occurs in the frequency characteristics during tracking adjustment.

[Means for solving problems]

In order to solve the above problems, the objective lens driving device according to the present invention has flexibility so that the movable part including the objective lens can be swung on a plane perpendicular to the optical axis of the objective lens. The optical pink-up L is supported via a swing support part, and is characterized in that the drive coil arranged in the magnetic circuit is provided outside the center of gravity from the swing fulcrum of the movable part including the objective lens. .

[For production]

When the drive coil is energized, it receives an electromagnetic force within the magnetic circuit. Then, the movable part provided with this drive coil swings on a plane perpendicular to the optical axis of the objective lens using the swing support part as a fulcrum. Therefore, in the case of an optical disk device, for example, since the objective lens can be displaced in the tracking direction together with this movable part, tracking adjustment of the optical pickup becomes possible.

At this time, the electromagnetic force that the drive coil receives acts on the outer side of the center of gravity of the movable part, so a moment is generated in a direction in which the movable part attempts to swing around the center of gravity. Therefore, the movable part tries to rotate on the circumference around its own center of gravity due to inertia, and does not try to move linearly in parallel.

Therefore, the swing support section can easily swing the movable section in response to the rotational force about the center of gravity of the movable section.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 to 3.

This embodiment describes an objective lens driving device for optical pink-up of an optical disk device.

The objective lens driving device of this embodiment will be explained based on FIGS. 1 and 2. In addition, the same reference numerals are added to the structural members having the same functions as those of the conventional example shown in FIGS. 8 and 9.

The objective lens 1 has an optical system arranged inside a cylindrical shape. This objective lens 1 is held by an objective lens holding member 2 with its periphery fixed.

The objective lens 1 and the objective lens holding member 2 constitute a movable part in the objective lens driving device. The movable parts must be as lightweight as possible in order to improve responsiveness. Therefore, its center of gravity is located on the optical axis of the objective lens 1, which requires the most weight. Objective lens holding member 2, -tracking direction (X direction in Figure 1)
One end side in a direction perpendicular to (X direction) is supported by a raised portion 4a of a substrate 4 via a movable support member 3.

The movable support member 3 has the same structure as the conventional one, and as shown in FIGS. Consisting of The fixed part 11 and the intermediate support part 12 are connected via a swinging hinge part 15 having flexibility, and the connecting parts 13, 13, the intermediate support part 12, and the support part 14 are connected to each other through a flexible swing hinge part 15. They are connected by a link hinge portion 16 .

Therefore, the intermediate support part 12, the connecting parts 13, 13, and the support part 14 side are connected to the fixed part 11 by the swinging hinge part 15 in a plane (X-Y plane) perpendicular to the focus direction (X direction).
It can be swung at the top. Further, the support part 14 is connected to the fixed part 1 by a parallel link mechanism by link hinge parts 16...
1 and the intermediate support portion 12 side in the focus direction.

The movable support member 3 is made of an integrally molded product made of resin or the like and is made as light as possible, so there is almost no need to consider the influence on the center of gravity of the movable part.

Fixed portion 1 in movable support member 3 configured in this way
1 is fixed to the substrate 4 by attaching both ends to the rising portion 4a. Further, the support portion 14 of the movable support member 3 is arranged in the tracking direction (X
One end side in the direction (X direction) perpendicular to the X direction is fixedly supported. As a result, the objective lens holding member 2
is supported on the board 4 so that it can swing and move in parallel.
You will be able to hold it. Further, the substrate 4 is attached to the tip of an optical pickup main body (not shown), and is configured to irradiate the optical disc with a light beam through the objective lens 1.

At the other end of the objective lens holding member 2 in the direction (X direction) perpendicular to the tracking direction (X direction), a tracking coil 8 in the horse motion coil is provided.

Further, on the other side of the tracking coil 8, magnets 9 are arranged side by side at intervals. The magnets 9 are supported by a yoke 10 that is fixed to the substrate 4 and stands upright, thereby forming a magnetic circuit.

Therefore, when the tracking coil 8 is energized, an electromagnetic force is generated in the tracking direction (X direction). This tracking direction coincides with the radial direction of an optical disk (not shown) on which the light beam is irradiated through the objective lens 1.

Further, focus coils 5b, which are drive coils, are provided at both ends of the objective lens holding member 2 in the tracking direction (X direction). Magnets 6 are placed on both sides of each focus coil 5b in the direction (X direction) perpendicular to the tracking direction (X direction).
・6 is placed with a gap. This magnet 6
・6 indicates both rising end portions 7a of the yoke 7 fixed to the substrate 4
- It is supported by 7b and forms a magnetic circuit.

Therefore, when the focus coils 5b are energized, an electromagnetic force is generated in the focus direction (X direction). This focus direction coincides with the optical axis direction of the objective lens 1.

Explaining the operation of the objective lens drive device configured as described above. When the tracking coil 8 is appropriately energized, the objective lens holding member 2 moves in the tracking direction ( (X direction). For this reason, the tracking of the light beam irradiated onto the optical disk through the objective lens 1 can be adjusted eight times. Also, if the focus coils 5b and 5b are energized appropriately,
The objective lens holding member 2 is moved in parallel in the focus direction (X direction) by the parallel link mechanism formed by the link hinge portions 16 of the movable support member 3. Therefore, the focus of the light beam irradiated onto the optical disc through the objective lens 1 can be adjusted in terms of frequency.

When making this tracking adjustment, the tracking coil 8
The electromagnetic force received by the object lens 1 acts on the outside of the center of gravity of the movable part consisting of the objective lens 1 and the objective lens holding member 2. Then, a moment is generated in this movable part about the center of gravity in the direction in which it is going to swing. Therefore, the movable part loses its own strength due to inertia.

It receives a rotational force around the center of gravity and can swing effortlessly about the swinging hinge part 15 as a fulcrum.

Therefore, even if this movable part is repeatedly driven to swing for tracking adjustment, as shown in FIG. 3, sub-resonance as shown in the conventional example shown in FIG. 10 does not appear in the frequency characteristics.

〔Effect of the invention〕

As described above, the objective lens drive device according to the present invention has a swing support member having flexibility so that the movable part including the objective lens can swing on a plane perpendicular to the optical axis of the objective lens. In the optical pickup supported via the magnetic circuit, the drive coil arranged in the magnetic circuit is provided outside the center of gravity from the swing fulcrum of the movable part including the objective lens.

Thereby, the movable part can swing without applying unreasonable force to the flexible swing support part.

Therefore, the present invention has the advantage that sub-resonance does not occur in the frequency characteristics during tracking adjustment, and there is no need to unnecessarily widen the frequency band of servo control or perform complicated control.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a plan view of the objective lens driving device, FIG. 2 is a side view of the objective lens driving device, and FIG. 3 is a tracking It is a graph showing frequency characteristics during adjustment. Figures 4 to 7
The figures show the movable support member, and FIG. 4 is a plan view of the movable support member, FIG. 5 is a side view of the movable support member, and FIG.
This figure is a plan view when the movable support member swings in the tracking direction, and FIG. 7 is a plan view when the movable support member moves in parallel in the focus direction. 8 to 10 show conventional examples, in which FIG. 8 is a plan view of the objective lens driving device, FIG. 9 is a side view of the objective lens driving device, and FIG.
Figure 0 is a graph showing frequency characteristics during tracking adjustment. 1 is an objective lens, 2 is an objective lens holding member, 3 is a movable support member, 8 is a trunking coil (drive coil), 9 is a magnet (magnetic circuit), 10 is a yoke (magnetic circuit),
15 is a swinging hinge part (swinging support part). Figure 3 10o1 Frequency [H2] Figure 4

Claims (1)

[Claims] 1. In an optical pickup in which a movable part including an objective lens is supported via a flexible swing support part so as to be swingable on a plane perpendicular to the optical axis of the objective lens, the movable part is arranged in a magnetic circuit. An objective lens driving device characterized in that a driving coil is provided outside a center of gravity from a swing fulcrum of a movable part including an objective lens.