JPH09106557A - Objective driving mechanism of optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the vibration of a lens holder during the execution of focus control and on-track control, to make a machine system for optical scanning lightweight, and to speed up recording and reproducing operation. SOLUTION: The lens holder 1 provided with a focus coil and track coils 30 and 30 side by side on one side of a holding part 10 holding an objective 2 is coupled with an intermediate member 5 by focus springs 4, 4..., and the intermediate member 5 is coupled with a base 7 by track springs 6, 6... and supported movably in a focus direction and a track direction, thereby forming a magnetic circuit including the focus coil and track coils 30 and 30. Then the lens holder 2 is moved in the focus direction and track direction as both the coils are fed with electricity. In this constitution, the center of gravity of a focus system movable part supported by the focus springs 4 and 4... is nearly aligned with the operation point of a focus-directional moving force and the center of gravity of a track system movable part supported by the track springs 6 and 6... is nearly aligned with the operation point of a track- directional moving force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for irradiating a recording surface of an optical recording medium such as an optical disc with a light beam to record and / or reproduce information. The present invention relates to an objective lens drive mechanism that drives an objective lens facing the recording surface to adjust a spot position.

[0002]

2. Description of the Related Art An optical recording / reproducing apparatus such as an optical disk apparatus for irradiating a light beam on one surface (recording surface) of an optical disk rotating around a single axis to record and / or reproduce information is a magnetic disk apparatus or a magnetic tape. Since it is possible to perform recording with a large capacity as compared with other recording devices such as a device, the use of the computer as an external recording device is expanding. In this type of optical recording / reproducing apparatus, a recording or reproducing light beam irradiated on the recording surface is irradiated onto a track formed on the recording surface in a small size light beam corresponding to the width of the track. It is necessary to focus and irradiate on a spot.

However, since the recording surface is not a flat surface in a strict sense, it is displaced along with the rotation of the optical disc during the recording or reproducing operation, and this displacement is caused by the mechanical system during the recording or reproducing operation. It is also caused by vibration. Therefore, conventionally, in order to keep the size (spot diameter) of the light spot on the recording surface appropriately, focus control that changes the focus position of the light beam, and to keep the spot position of the light beam on the desired track, The on-track control is performed to finely move the irradiation position in the direction crossing each track, and the fine movement of the irradiation position for the on-track control and the change of the focus position for the focus control are generally performed. It is realized by moving the objective lens facing the recording surface.

An objective lens driving mechanism for moving an objective lens is elastically movable so that a lens holder holding the objective lens can be displaced in a focus direction for approaching and separating from a recording surface and a track direction crossing a track on the recording surface. On the other hand, a focus coil and a track coil having a predetermined winding form are mounted on the lens holder, and a magnetic circuit is formed including required parts of both coils. By energizing the coil or the track coil, a force in the focus direction or the track direction is applied to the lens holder, and the objective lens is moved together with the lens holder.

In this type of objective lens drive mechanism,
Conventionally, various proposals have been made for the structure and support structure of a lens holder, and the structure of the lens holder is disclosed in Japanese Patent Application Laid-Open No. 4-205927 and Japanese Patent Publication No. 6-64752. As described above, a configuration in which a holding unit that holds an objective lens and a mounting unit for a focus coil and a track coil are arranged in parallel in a direction orthogonal to the focus direction and the track direction to achieve a thin profile in the focus direction is widely adopted. ing.

Regarding the supporting structure of the lens holder,
A supporting structure as disclosed in Japanese Patent Publication No. 6-64752 and Japanese Patent Application Laid-Open No. 59-104733 is often used. This uses two types of leaf springs having flexibility only in the focus direction or the track direction. For example, the former leaf spring (focus spring) connects the lens holder to the intermediate member, and the intermediate member is used for the latter leaf plate. By connecting to the base by a spring (track spring), the movement in the focus direction is the movement of the lens holder that occurs with respect to the intermediate member due to the deflection of the focus spring, and the movement in the track direction.
The intermediate member and the lens holder are caused to move with respect to the base along with the bending of the track spring, and when moving in the focus direction or the track direction, the influence of the movement in the other direction is eliminated and stable. It is possible to operate.

[0007]

However, even in the objective lens drive mechanism adopting the lens holder structure and the lens holder support structure as described above, the focus is frequently repeated during the focus control and the on-track control. When the lens holder moves due to energization of the coil and the track coil, self-excited vibration occurs in the lens holder, which causes a problem of deteriorating control accuracy.

Further, in recent years, optical recording / reproducing apparatuses are required to have high-speed recording and reproducing operations, and in order to meet these requirements, the weight of a mechanical system for scanning a light beam should be reduced. In particular, it is an important issue to reduce the weight of an objective lens driving mechanism that is a movable part and a carriage that mounts the objective lens driving mechanism and moves along a recording surface of an optical recording medium. However, the weight-reduced carriage is highly likely to be excited by the vibration associated with the operation of the objective lens drive mechanism, and the excitation of the carriage overlaps the vibration of the lens holder, resulting in an accurate light beam emitted through the objective lens. There is an inconvenience that the scanning is hindered and the quality of the recording or reproduction signal is deteriorated. In order to realize the downsizing and weight reduction of the optical recording / reproducing apparatus and the high operation speed, the operation of the objective lens drive mechanism is required. It is an important issue to suppress the vibration of the lens holder that is generated.

The present invention has been made in view of such circumstances, and it is possible to effectively suppress the vibration of the lens holder during execution of the focus control and the on-track control, and to reduce the weight of the mechanical system for optical scanning. It is an object of the present invention to provide an objective lens driving mechanism of an optical recording / reproducing device that can contribute to speeding up of recording and reproducing operations.

[0010]

According to the objective lens driving mechanism of the present invention, a lens holder in which a focus coil and a track coil are arranged side by side on one side of a holding portion for holding an objective lens is provided by a first leaf spring. A second plate spring for connecting the intermediate member to a base member, and movably supporting the member in a focus direction approaching and leaving a recording surface of the optical recording medium and a track direction traversing a track on the recording surface. At the same time, a magnetic circuit including the focus coil and the track coil is formed, and the lens holder is configured to move the lens holder in the focus direction and the track direction according to energization of both coils. In the mechanism, the center of gravity of the focus system movable portion supported by the first leaf spring or the second leaf spring is the action of the moving force in the focus direction. And the center of gravity of the track system movable portion supported by the second leaf spring or the first leaf spring is substantially aligned with the point of action of the moving force in the track direction. And

The point of action of the moving force in the focus direction or the track direction generated by energizing the focus coil or the track coil in the magnetic circuit is defined as the center of gravity of the focus system moving part or the track system moving part which is moved by each force. The substantially matched arrangement suppresses generation of unnecessary vibration of the lens holder.

The first or second leaf springs supporting the movable focus system are at least a pair of leaf springs arranged substantially symmetrically with respect to the center of gravity of the movable focus system in the focusing direction. That is, the second or first leaf spring supporting the track system movable portion is at least a pair of leaf springs arranged substantially symmetrically with respect to the center of gravity of the track system movable portion in the track direction. Furthermore, the center of gravity of the focus system movable portion and the center of gravity of the track system movable portion are arranged in the same plane orthogonal to the focus direction.

With these arrangements, when a moving force in the focus direction or the track direction is applied, generation of a bending moment that causes torsional vibrations in the first and second leaf springs supporting the lens holder is suppressed, and this bending is suppressed. The generation of unnecessary vibration of the lens holder due to the action of moment is suppressed.

Further, the magnetic circuit includes a yoke and a magnet that sandwich the track coil and the focus coil to face each other, or a pair of magnets, and the magnet except a surface facing the yoke or the other magnet. It is characterized in that it is covered with a magnetic material.

With this structure, the leakage of the magnetic flux from both sides of the magnet is reduced, the magnetic flux is concentrated on the necessary portion of the track coil, and the track movement is stably generated.

Further, the first leaf spring is a spring having flexibility in the focus direction, and the second leaf spring is a spring having flexibility in the track direction, The track coil is mounted on one surface, and the focus coil is wound and held around the outer periphery including the mounting portion, and a coil bobbin is attached to the lens holder with the mounting surface of the track coil facing the holding portion. Each is characterized by.

That is, the leaf spring connecting the lens holder and the intermediate member is a focus spring having flexibility in the focus direction, and the leaf spring connecting the intermediate member and the base is flexible in the track direction. As a spring, the track system movable part supported by the track spring includes an intermediate member, and the center of gravity of the movable part is located on the side farther from the objective lens than the center of gravity of the focus system movable part, and the track coil is mounted on one surface. By attaching a coil bobbin, which is a focus coil by winding a winding around the outer circumference of the coil bobbin, to the lens holder with the mounting surface of the track coil facing the holding part side of the objective lens, the center of gravity of both movable parts and the focus direction and The above-mentioned positional relationship with the action point of the moving force in the track direction is easily realized.

The track coil mounted on one surface of the coil bobbin is pressed by the winding of the focus coil on the outer side thereof, and the focus coil is positioned by winding around the coil bobbin, which is necessary for realizing the above-mentioned arrangement. A track coil and a focus coil with high positional accuracy can be easily obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a perspective view showing an example of an objective lens driving mechanism of the present invention, and FIG. 2 is an exploded perspective view of the objective lens driving mechanism shown in FIG.

In the objective lens driving mechanism of the present invention, the lens holder 1 for holding the objective lens 2 facing the recording surface of the optical recording medium (not shown) is brought into contact with or separated from the recording surface (focusing direction). It is moved in the direction (track direction) that traverses the track formed on the recording surface. The focus direction and the track direction are indicated by arrows in FIG.

In the lens holder 1, a rectangular frame-shaped coil mounting portion 11 is arranged in parallel on one side of a plate-shaped holding portion 10 for holding the objective lens 2 in the substantially center thereof. A coil bobbin 3 for holding the track coils 30, 30 and the focus coil 31 is attached as will be described later.

FIG. 3 is an explanatory view of the procedure for assembling the coil bobbin 3. The coil bobbin 3 is, for example, a short cylindrical body having a rectangular cross section obtained by integrally molding a high-rigidity resin material, and as shown in FIG. The portions 3a, 3a are provided, and the flange edges 3b reaching the tip of the projecting portion along the respective end edges are provided at both ends in the axial direction of the other three surfaces.

On the one side surface of the coil bobbin 3, a pair of holding projections are separated from each other by a predetermined length in the width direction at the center in the axial direction.
3c and 3c are projected. The track coils 30 and 30 are coils that are wound around the insertion holes into the holding protrusions 3c and 3c and have a rectangular winding shape in plan view and are multiply wound, as shown in FIG. 3 (a). Yes, holding each insertion hole Protrusions 3c, 3c
As shown in FIG. 3 (b), the coil bobbin 3 is attached with a parallel portion along the axis of the coil bobbin 3 at a substantially central portion of the one side surface.

On the other hand, the focus coil 31 has multiple windings on the outside of the coil bobbin 3 to which the track coils 30 and 30 are attached in this way, over the entire length of the coil bobbin 3, to the extent that it does not project to the outside of the brim edge 3b. Wound around,
It is configured as shown in (c). Focus coil 31
The winding holds the track coils 30 and 30 positioned by being inserted into the holding protrusions 3c and 3c from the outside, and acts to prevent the track coils 30 and 30 from coming off.

The coil bobbin 3 thus constructed is
The track coils 30 and 30 and the focus coil 31 can be stably held, and in particular, the track coils 30 and 30 are fixed by inserting them into the holding protrusions 3c and 3c and then winding the focus coil 31. It can be easily assembled because it is realized by winding.

As described above, the coil bobbin 3 for holding the track coils 30, 30 and the focus coil 31 has the mounting surface for the track coils 30, 30 inside the coil mounting portion 11 formed as a rectangular frame. As shown in FIG. 1, the track coils 30 and 30 and the focus coil 31 are arranged side by side on one side of the holding portion 10 in the direction orthogonal to the focus direction and the track direction. The lens holder 1 is configured.

As shown in FIG. 3, the collar edges 3b, 3b on both sides of the coil bobbin 3 extend beyond the thickness of the focus coil 31 wound around the track coils 30, 30.
When the coil bobbin 3 is fitted, the extension portion is fitted inside the corresponding portion of the coil mounting portion 11.

FIG. 4 shows the rear surface of the coil bobbin 3 (holding portion 10).
It is a perspective view from the side (the surface away from). The brim edges 3b, 3b that border both sides in the axial direction of the coil bobbin 3 project beyond the winding thickness of the focus coil 31 on the back side in the drawing, and one brim edge 3b has a wide engagement groove. 3d and a narrow engagement groove 3e is formed in the other brim edge 3b at the center in the width direction.

On the other hand, in the assembled state, the coil bobbin 3
As shown in FIG. 2, on the inner surface of the coil mounting portion 11 which faces the back surface of the coil mounting portion 11, there is provided a wide engaging protrusion 11a corresponding to the engaging groove 3d over the entire length in the axial direction at the center in the width direction. On the upper surface of the coil mounting portion 11 which is projected and is continuous with the inner surface, an engaging projection 11b having a narrow width corresponding to the engaging groove 3e is projected.

As shown in FIG. 2, the coil bobbin 3 is attached to the coil mounting portion 11 by using the coil bobbin 3 with the side on which the narrow engaging groove 3e is formed facing upward, and on the holding portion 10 side, the brim 3
While holding the corresponding part of the coil mounting part 11 between the extension parts of b and 3b on the same side, and on the side away from the holding part 10, the wide engagement groove 3d at the lower position is formed in the engagement protrusion 11a. It is fitted into the coil mounting portion 11 while being engaged, and as shown in FIG. 1, the engaging groove 3e is engaged with the engaging protrusion 11b to complete the process. The coil bobbin 3 mounted in this way is engaged with the engaging grooves 3d, 3e and the engaging protrusions 11a, 11b on the side away from the holding portion 10, and on the holding portion 10 side, the brim edge 3b. , 3b are sandwiched between the corresponding portions of the coil mounting portion 11 to position the coil bobbin 3 in the axial direction and the width direction, so that the coil bobbin 3 can be easily attached with high positional accuracy.

The lens holder 1 constructed as described above is
As shown in FIG. 1, it is connected to the intermediate member 5 by the focus springs 4, 4, ...
The intermediate member 5 is connected to the base 7 by the track springs 6, 6 ... Having flexibility in the track direction, and the elasticity of the focus springs 4, 4 ,. It is movably supported, and is also supported by the intermediate member 5 so as to be movable in the track direction with respect to the base 7 by the elasticity of the track springs 6, 6.

Focus springs 4, 4, ... As shown in FIG.
Is a holding portion 10 and a coil mounting portion 11 of the lens holder 1.
Two leaf springs each having one end fixed at positions separated by a predetermined length in the width direction (track direction) on both surfaces in the up-down direction (focus direction) in the vicinity of the continuous portion. The other ends of the focus springs 4, 4, ... Are parallel to each other and extend toward the other side of the coil mounting portion 11, and the corresponding portion of the intermediate member 5 is separated from the tip of the coil mounting portion 11 by an appropriate length. The lens holder 1 and the intermediate member 5 are connected to each other in this manner.

Both end surfaces in the width direction of the intermediate member 5 are inclined surfaces with the support side of the lens holder 1 widened. The track springs 6, 6, ... Are two leaf springs each having one end fixed to a fixed position set apart from each other in the focus direction on each of the inclined surfaces, and the other ends of the leaf springs It is extended to the side of the lens holder 1 while being widened along the inclination of the surface, and is separated by an appropriate length on both sides of the lens holder 1 at appropriate portions of a pair of support columns 70, 70 which are erected on the base 7. It is fixed, and thus the connection between the intermediate member 5 and the base 7 is realized.

On the surface of the base 7, a pair of yokes 71, 72 located between the supporting columns 70, 70 are erected at a predetermined distance in the directions orthogonal to the focus direction and the track direction, respectively. A magnet 73 is fixed to the surface of one yoke 72 facing the other. As shown in FIG. 1, the yoke 72 and the magnet 73 are
The yoke 71 is located inside the coil bobbin 3 attached to the lens holder 1 supported as described above, and the other yoke 71 faces the magnet 73 across the fixed surface of the track coils 30 and 30. A magnetic circuit extending from one side to the other side across the entire width direction of the disk traverses the track coils 30, 30 and the focus coil 31.

When a drive current is applied to the focus coil 31, a force in the direction orthogonal to the winding in the magnetic circuit, that is, the focus direction, acts on the focus coil 31 to cause the focus coil 31 to move. The coil bobbin 3 and the lens holder 1 holding 31 are displaced with respect to the intermediate member 5 by the bending deformation of the focus springs 4, 4, ... Having flexibility in the same direction, and the objective lens held by the lens holder 1 2 moves the focus in the focus direction, that is, in the direction of approaching and leaving the recording surface of the optical recording medium (not shown) facing the upper part.

Track springs 6, 6 for supporting the intermediate member 5
Has a sufficient rigidity in the focus direction, so that the focus movement of the objective lens 2 according to the energization of the focus coil 31 is stably generated without the movement in the track direction.

On the other hand, when a drive current is applied to the track coils 30, 30, a force is applied to the track coils 30, 30 in the direction orthogonal to the windings in the magnetic circuit, that is, in the track direction. The coil bobbin 3 and the lens holder 1 for holding the track coils 30, 30 are displaced with respect to the base 7 together with the intermediate member 5 with the flexural deformation of the track springs 6, 6, ... Having flexibility in the same direction. The objective lens 2 held by the lens holder 1 moves in the track direction, that is, in the direction traversing the track formed on the recording surface.

Since the focus springs 4, 4, ... Connecting the intermediate member 5 and the lens holder 1 have sufficient rigidity in the track direction, the track movement of the objective lens 2 according to the energization of the track coils 30, 30 is prevented. As a result, the intermediate member 5 and the lens holder 1 are integrated and stably generated without any movement in the focus direction. Further, the track movement is performed by extending the track springs 6, 6 ... In the plane orthogonal to the focus direction by erection of the track springs 6, 6 between the intermediate member 5 and the base 7 in the above-described manner. Stable as a circular motion centered on the intersection of.

As shown in FIG. 1, the holding portion of the lens holder 1
The objective lens 2 held by 10 is at a position separated from the fixed surface of the base 7 by an appropriate length. Immediately below the objective lens 2, a rising mirror 8 fixed to the fixed surface is arranged,
The recording surface of the optical recording medium is irradiated with the light beam B reflected by the raising mirror 8 after being condensed by the objective lens 2.

Accordingly, when the focus of the objective lens 2 is moved by energizing the focus coil 31, the change of the focal position causes the change of the light spot diameter of the light beam B appearing on the recording surface. It is possible to perform focus control to keep the light spot diameter appropriate. On the other hand, when the objective lens 2 is moved in the track by energizing the track coils 30 and 30, the light beam B on the recording surface is
The optical spot of moves in the direction traversing the track formed on the recording surface, and on-track control for stopping the optical spot on a desired track becomes possible.

In the objective lens drive mechanism that operates as described above, the point of application of the drive force at the time of focus movement is the center of the portion of the focus coil 31 existing in the magnetic circuit, that is, between the yokes 71 and 72. The center of one surface of the coil bobbin 3 sandwiched between the two is substantially coincident with the center of the winding along the one surface in the thickness direction. The center of a portion existing in the magnetic circuit, that is, between the parallel portions of both track coils 30, 30 on one surface of the coil bobbin 3 sandwiched between the yokes 71, 72, the track coils 30, 30
It substantially coincides with the center of the winding in the thickness direction.

The feature of the objective lens driving mechanism of the present invention is that the point of application of the driving force as described above moves focus by energization of the focus coil 31 (focus system movable part).
Is set in association with the center of gravity of the track coil and the center of gravity of the portion (track system movable portion) that moves in the track by energizing the track coils 30, 30.

FIG. 5 is a plan view in the plane orthogonal to the focus direction of the objective lens driving mechanism shown in FIG.
[Fig. 6] is a vertical sectional view in a plane that also includes the focus direction. In these figures, G _F represents the center of gravity of the focus system movable part, and G _T represents the center of gravity of the track system movable part.

As described above, the focus movement is caused by the displacement of the lens holder 1 with respect to the intermediate member 5 with the deflection of the focus springs 4, 4, .... Therefore, the center of gravity G _{F of the} movable part of the focus system coincides with the center of gravity of the lens holder 1 that holds the objective lens 2 and the coil bobbin 3, and this center of gravity G _F in the focus direction is as shown in FIGS. Point of action of moving force, that is, focus coil 31
It is aligned with the center of the portion sandwiched between the yokes 71 and 72 in the thickness direction.

This matching is related to the shape and weight of the lens holder 1, the size and weight of the coil bobbin 3 including the track coils 30 and 30, the focus coil 31, and the position of the focus coil 31 such as the mounting position of the coil bobbin 3. It can be realized by adjusting various dimensions and weights. Due to this coincidence, the moving force associated with the energization of the focus coil 31 acts correctly on the center of gravity G _{F of the} movable part of the focus system that moves due to this force, and unnecessary vibration of the lens holder 1 during focus movement occurs. Occurrence can be suppressed.

On the other hand, when the track is moved, track springs 6 and 6 are used.
It is caused by the displacement of the intermediate member 5 with respect to the base 7 accompanied by the bending of. Therefore, the track system movable part is a part in which the intermediate member 5 and the focus springs 4, 4, ... Are added to the focus system movable part described above, and the center of gravity G _T of the track system movable part is the center of gravity G _{F of the} focus system movable part. It is located farther from the holding portion 10 than. This center of gravity G _T is, as shown in FIGS. 5 and 6, the point of action of the moving force in the track direction, that is,
A pair of track coils 30, 30 sandwiched between the yokes 71, 72
Between the parallel portions of the track coils 30 and 30 and the centers of the windings of the track coils 30 in the thickness direction.

This coincidence means that the track coils 30, 30 are located farther from the holding portion 10 than the focus coil 31, so that the weight of the intermediate member 5, the intermediate member 5 and the lens holder 1
It can be realized by adjusting various amounts related to the positional shift amount of the center of gravity G _T of the track system movable part with respect to the center of gravity G _F of the focus system movable part, such as the lengths of the focus springs 4, 4 ,. And by this match, the track coil
The moving force due to the energization of 31 correctly acts on the center of gravity G _T of the track system moving part moved by this force, and it is possible to suppress the generation of unnecessary vibration of the lens holder 1 during the track movement. .

Further, as shown in FIG. 6, the focus springs 4, 4, ... Supporting the movable part of the focus system are arranged substantially symmetrically with respect to the center of gravity G _{F of the} movable part of the focus system in the focusing direction. Further, as shown in FIG. 5, the track springs 6, 6, ... That support the track system drive section are arranged substantially symmetrically with respect to the center of gravity G _T of the track system movable section in the track direction. With such an arrangement, the focus springs 4, 4, ...
Alternatively, it is possible to suppress the generation of a bending moment that causes torsional vibration in the track springs 6, 6, ..., And it is possible to suppress the generation of unnecessary vibration of the lens holder 1 due to the action of the bending moment.

As described above, in the objective lens driving mechanism shown in FIG. 1, unnecessary vibrations of the lens holder 1 occur when the moving force acts during the focus movement and the track movement, that is, during the focus control and the on-track control. The generation can be effectively suppressed. Therefore, it is possible to reduce the weight of the mechanical system for optical scanning without fear of occurrence of excitation due to the operation of the objective lens drive mechanism, and to provide an optical recording / reproducing apparatus capable of contributing to speeding up of recording and reproducing operations. Will be able to provide.

FIG. 7 is a perspective view showing another embodiment of the objective lens driving mechanism of the present invention. In this figure, the lens holder 1 and the intermediate member 5 are connected by track springs 6, 6 ... Having flexibility in the track direction, and the intermediate member 5 has a focus spring 4 having flexibility in the focus direction. , 4, ... Support pillars 70, 70 erected on the base 7
The lens holder 1 is movably supported in the focus direction and the track direction.

In this structure, the lens holder 1 including the objective lens 2 and the coil bobbin 3 serves as a track system movable part, and the track springs 6, 6 ... And the intermediate member 5 are provided therewith.
Since the part to which is added becomes the focus system movable part, the center of gravity G _F of the focus system movable part is located farther from the holding part 10 than the track system movable part G _T. Therefore, in order to realize the above-described arrangement between the centers of gravity G _F and G _T and the action points of the moving force in the focus direction and the track direction,
The coil bobbin 3 has a structure in which a pair of track coils 30 and 30 are fixed to the outside of a focus coil 31 wound and held on the outer periphery, and the action point of the focus moving force is farther from the holding unit 10 than the action point of the track moving force. I am trying to locate it.

FIG. 8 is a perspective view of a base showing another embodiment of the objective lens driving mechanism of the present invention. Illustrated base 7
A pair of yokes 7 are located on the surface of the
1 and 72 are erected at a predetermined distance in a direction orthogonal to the focus direction and the track direction, respectively.
The magnet 73 is fixed to the surface facing the other yoke 71 of FIG.
As in FIG. 7 and FIG. 7, a magnetic circuit including the track coils 30, 30 and a part of the focus coil 31 is constructed. In FIG. It is provided so as to cover the entire surface except the surface facing the other yoke 71.

The yoke 72 as described above is not limited to the one integrally formed with a U-shaped cross section, but only the portion that covers the back surface of the magnet 73 is erected on the base 7 and the magnets are provided on both sides of this portion. It is also possible to form a body-made plate material by fixing, and it is sufficient if the entire surface except the surface facing the other yoke 71 is covered with a magnetic material.

FIG. 9 is an explanatory view of effects of the embodiment shown in FIG. FIG. 9A shows a formation mode of the magnetic circuit in FIG. 1. In this configuration, as shown by a broken line in the drawing, a leakage magnetic flux is generated between both side surfaces of the magnet 73 and the yoke 71. , The magnetic flux crosses the non-acting portion of the track coils 30, 30 arranged as described above, that is, the portion located outside the magnetic gap, and a moving force in a direction different from the desired direction is applied to this portion. Occur.

On the other hand, in FIG. 9B showing the formation mode of the magnetic circuit in FIG. 8, most of the magnetic flux on both sides of the magnet 73 is folded back to the yoke 72 side, and the magnetic flux in the track coils 30, 30 is reduced. Since the leakage flux across the outer portion of the gap is greatly reduced, stable operation in the track direction is possible.

In the above embodiment, the magnetic circuit including the track coils 30, 30 and the focus coil 31 is formed by the magnet 73 and the yoke 71 which face each other across the track coils 30, 30 and the focus coil 31. However, as shown in FIG. 10, a magnet 74 is fixedly installed also on the side of the yoke 71, and a magnetic circuit is formed by a pair of magnets 73 and 74 that face each other with the track coils 30 and 30 and the focus coil 31 interposed therebetween. You can also do it.

Also in this case, as in FIG. 8, the yokes 72, 71 supporting the back surfaces of the magnets 73, 74 are provided in such a manner as to cover the entire surface except the surface facing the other magnets 74, 73. With this configuration, the track coil 30,
The leakage flux across the outer portion of the magnetic gap at 30 is greatly reduced, allowing stable operation in the track direction.

[0058]

As described above in detail, the optical recording / recording according to the present invention
In the objective lens drive mechanism of the reproducing device, the action point of the moving force in the focus direction or the track direction is arranged to be substantially coincident with the center of gravity of the focus system moving part or the track system moving part moved by each force, Excitation of the mechanical system for optical scanning is effectively suppressed.

Further, at least one pair of focus springs for supporting the movable part of the focus system are arranged substantially symmetrically with respect to the center of gravity of the movable part of the focus system, and a track spring for supporting the movable part of the track system is arranged as a track system. At least one pair is arranged substantially symmetrically with respect to the center of gravity of the movable part in the track direction, and further, the center of gravity of the focus system movable part and the center of gravity of the track system movable part are arranged in the same plane orthogonal to the focus direction. It is possible to suppress the generation of a bending moment that causes torsional vibration in the focus spring and the track spring when the moving force in the focus direction or the track direction is applied.

As a result, the excitation of the mechanical system for optical scanning can be effectively suppressed, and the weight reduction of the mechanical system can contribute to the speeding up of recording and reproducing operations.

Further, since the magnet constituting the magnetic circuit is covered with the magnetic material except for the surface facing the yoke or the other magnet, leakage of the magnetic flux from both sides of the magnet can be prevented, and the magnetic flux can be prevented from flowing in the track coil. Concentrating on the action part of, the track movement will occur stably.

Further, the first leaf spring connecting the lens holder to the intermediate member is used as a focus spring having flexibility in the focus direction, and the second leaf spring connecting the intermediate member to the base is moved in the track direction. As a flexible track spring, the track system movable part supported by the track spring includes an intermediate member, and the center of gravity of the movable part is located on the side farther from the objective lens than the center of gravity of the focus system movable part,
Since the focus coil is attached to the coil bobbin lens holder wound from the outside of the mounting portion of the track coil, a desired arrangement between the action point of the moving force and the center of gravity of each of them can be easily realized, and this arrangement The present invention has excellent effects such that a track coil and a focus coil with high positional accuracy required for realization can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an objective lens driving mechanism of the present invention.

FIG. 2 is an exploded perspective view of the objective lens driving mechanism shown in FIG.

FIG. 3 is an explanatory diagram of a procedure for assembling a coil bobbin.

FIG. 4 is a perspective view from the back side of the coil bobbin.

5 is a plan view of the objective lens driving mechanism shown in FIG. 1 in a plane orthogonal to the focus direction.

6 is a vertical cross-sectional view in a plane including a focus direction of the objective lens driving mechanism shown in FIG.

FIG. 7 is a perspective view showing another embodiment of the objective lens driving mechanism of the present invention.

FIG. 8 is a perspective view of a base showing another embodiment of the objective lens driving mechanism of the present invention.

FIG. 9 is an effect explanatory diagram of the embodiment shown in FIG.

FIG. 10 is a perspective view of a base showing another embodiment of the objective lens driving mechanism of the present invention.

[Explanation of symbols]

 1 lens holder 2 objective lens 3 coil bobbin 4 focus spring 5 intermediate member 6 track spring 7 base 10 holding part 11 coil mounting part 30 track coil 31 focus coil 71 yoke 72 yoke 73 magnet 74 magnet

Claims (6)

[Claims] 1. A lens holder having a focus coil and a track coil arranged in parallel on one side of a holding portion for holding an objective lens is connected to an intermediate member by a first leaf spring, and the intermediate member is attached to a second plate. A magnetic circuit including a focus coil and a track coil, which is connected to a base by a spring and is movably supported in a focus direction toward and away from a recording surface of an optical recording medium and a track direction across a track on the recording surface. In the objective lens driving mechanism of the optical recording / reproducing apparatus, wherein the lens holder is moved in the focus direction and the track direction according to the energization of both coils. The center of gravity of the focus system movable portion supported by the leaf spring is substantially aligned with the point of action of the moving force in the focus direction. The objective lens drive mechanism of the optical recording / reproducing apparatus, wherein the center of gravity of the track system movable portion supported by the first leaf spring is substantially coincident with the point of action of the moving force in the track direction. 2. The first or second leaf spring supporting the movable focus system is at least a pair of leaf springs arranged substantially symmetrically with respect to the center of gravity of the movable focus system in the focus direction. The objective lens driving mechanism of the optical recording / reproducing apparatus according to claim 1. 3. The second or first leaf spring for supporting the track system movable part is provided with respect to the center of gravity of the track system movable part.
The objective lens driving mechanism of the optical recording / reproducing apparatus according to claim 1 or 2, comprising at least a pair of leaf springs arranged substantially symmetrically in the track direction. 4. The center of gravity of the focus system movable portion and the center of gravity of the track system movable portion are arranged in the same plane orthogonal to the focus direction. Objective lens drive mechanism for optical recording / reproducing device. 5. The magnetic circuit includes a yoke and a magnet that sandwich the track coil and the focus coil to face each other, or a pair of magnets, and the magnet excludes a surface facing the yoke or the other magnet. The objective lens drive mechanism of the optical recording / reproducing apparatus according to any one of claims 1 to 4, which is covered with a magnetic material. 6. The first leaf spring is a spring having flexibility in the focus direction, and the second leaf spring is a spring having flexibility in the track direction, The track coil is mounted on one surface, and the focus coil is wound and held around the outer periphery including the mounting portion, and a coil bobbin is attached to the lens holder with the mounting surface of the track coil facing the holding portion. An objective lens drive mechanism of the optical recording / reproducing apparatus according to any one of claims 1 to 5.