JPH06325383A - Objective lens actuator - Google Patents

Abstract

PURPOSE:To suppress the oscillation in a lens holder and the change in moving resistance. CONSTITUTION:A hollow part 2a is formed in a lens holder 2 holding an objective lens 3, and a pair of tracking coils 11 and a pair of focusing coils 12 are attached to the outer side surface of the holder 2. In the hollow part 2a, an intermediate member 4 connected to the lens holder 2 by a first plate spring 5 is arranged. The intermediate member 4 is connected to a base member 1 by a pair of second plate springs 6, and the lens holder 2 is supported in a housing part 1a. By impressing a driving current through the tracking coils 11, the lens holder 2 is turned while deforming the first leaf spring 5, and by impressing the driving current through the focusing coil 12, the lens holder 2 is moved in the direction C of an optical axis while deforming the second plate spring 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an optical information recording / reproducing apparatus such as an optical disk drive device, which supports an objective lens for condensing a light beam and records a light spot formed by the objective lens. The present invention relates to an objective lens actuator that moves along a recording track of a medium.

[0002]

As an optical information recording / reproducing apparatus using a conventional objective lens actuator, for example, Japanese Patent Application No. 4-50
In JP 58, a coil portion for focusing operation and a coil for tracking operation are fixed to the outer peripheral surface, and a cylindrical portion,
The lens holding cylinder includes a lens holding cylinder including a top plate portion that holds the objective lens at a position deviated from the center of rotation of the cylinder portion, and a support shaft that is erected on the base. The lens holding cylinder serves as the support shaft. Optical reading using an objective lens actuator that is held in an externally fitted state, slides on a support shaft, moves vertically (focusing operation) in a minute range, and rotates (tracking operation) in a minute range. The device is shown.

In the above-mentioned objective lens actuator of the optical reading apparatus, since the objective lens is deviated from the center of rotation of the lens holding cylinder, optical components such as a mirror and a prism for changing the optical path are provided directly below the objective lens. The objective lens actuator is thinned by being easily arranged and further by forming a cutout portion for passing light in a part of the peripheral wall of the cylindrical portion of the lens holding cylinder.

[0004]

However, in a shaft-sliding type objective lens actuator in which a lens holder such as a lens holding cylinder slides on a spindle to perform a tracking operation and a focusing operation, the lens holder and the spindle are provided. Since there is a minute gap between the lens holder and the lens holder, the lens holder will move during the access operation to move the entire objective lens actuator in the radial direction of the disc-shaped information recording medium, or when external vibration is applied to the optical information recording / reproducing device. The information recording medium is apt to vibrate, and when minute foreign matter such as dust adheres to the support shaft, the movement resistance of the lens holder increases. Such an increase in the vibration and movement resistance of the lens holder causes a decrease in the accuracy of tracking control and focusing control and causes a servo error.

An object of the present invention is to provide an objective lens actuator in which the vibration of the lens holder and the change of the movement resistance are suppressed.

[0006]

In order to solve the above problems, the first means of the present invention is to provide an objective lens for condensing a light beam, an objective lens for holding the objective lens, and an optical axis direction of the objective lens. A lens holder having a hollow portion formed therethrough,
An intermediate member disposed in the hollow portion, a base member that moves along a recording surface of a disc-shaped information recording medium, a first leaf spring that connects the lens holder and the intermediate member, and the base member A second plate spring connecting the intermediate member and the first plate spring is bent, and a lens holder is formed with a straight line that is separated from the optical axis of the objective lens and is orthogonal to the recording surface of the information recording medium as an axis. It is characterized in that the lens holder is rotated and the second plate spring is bent to move the lens holder in the optical axis direction.

Further, a second means is a tracking means for causing a couple force about the axis to act on the lens holder to bend the first leaf spring, and a force in the optical axis direction for the lens holder. Focusing means for bending the second leaf spring by acting on the.

Further, the third means is characterized in that the movable portion which is constructed integrally with the lens holder and moves with respect to the base member has a center of gravity at an arbitrary position on the axis.

Further, the fourth means is characterized in that the neutral axis of the first leaf spring is parallel to the moving direction of the base member when the first leaf spring is not deformed.

Further, the fifth means is characterized in that the neutral axis of the second leaf spring is made orthogonal to the moving direction of the base member when the second leaf spring is not deformed.

Further, the sixth means is characterized in that a viscous vibration suppressing member is filled in a gap between the inner surface of the hollow portion and the first leaf spring and the intermediate member.

[0012]

According to the first means, the first plate spring is bent to rotate the lens holder about the axis, and the second plate spring is bent to move the lens holder in the optical axis direction. By the objective lens actuator configured to move, the objective lens moves in the radial direction of the information recording medium when the first leaf spring is deformed, and the objective lens moves in the optical axis direction when the second leaf spring is deformed.

Further, according to the second means, a tracking means for applying a couple force centering on the axis to the lens holder and a focusing means for applying a force in the optical axis direction to the lens holder, During operation, the lens holder rotates about the axis, and during operation of the focusing means, the lens holder moves in the optical axis direction.
Further, according to the third means, the movable part having the center of gravity at an arbitrary position on the shaft center balances the inertial weights of the movable part around the shaft center.

Further, according to the fourth means, the first leaf spring having the neutral axis parallel to the moving direction of the base member when not deformed causes the first leaf spring to bend due to inertial force when the base member moves. Is prevented.

Further, according to the fifth means, the second leaf spring having the neutral axis orthogonal to the moving direction of the base member when not deformed causes the inertial force when the base member is moved to the second leaf spring. Do not apply component force in the direction of the neutral axis to.

Further, according to the sixth means, when the first leaf spring vibrates by the vibrating vibration-suppressing member filled in the gap between the inner surface of the hollow portion and the first leaf spring and the intermediate member. , The vibration time of the first leaf spring is reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a plan view showing the schematic construction of an optical disk drive device to which an embodiment of the objective lens actuator of the present invention is applied, and FIGS. 1, 2 and 3 are exploded perspective views of the essential parts of this embodiment, respectively. It is a figure, a top view, and a side sectional view.

1 is a base member having a storage portion 1a formed therein,
Reference numeral 2 denotes a lens holder which is arranged in the storage portion 1a and which has a hollow portion 2a which holds the objective lens 3 and which penetrates the objective lens 3 in the optical axis direction. An intermediate member 5 having an end surface and a lower end surface protruding from the hollow portion 2a is a first leaf spring that connects the intermediate member 4 and the lens holder 2 in the hollow portion 2a, and 6 is a portion near the tip of the intermediate member 4 above the intermediate member 4. A pair of second leaf springs are attached to the end face and the lower end face, respectively, and the vicinity of the rear end is attached to the fixing member 7, and the fixing member 7 is fitted to the fitting portion 1b formed on the base member 1. Will be fixed together.

The optical disk drive device emits a laser beam L to a spindle motor 52 for rotating an optical disk 51, which is an information recording medium shown by a chain double-dashed line in FIG. 4, and a base member 1, and has a recording surface of the optical disk 51. The fixed optical system 53 for detecting the reflected light from the light source 51a. Also,
The pair of guide rails 8 are installed in the radial direction (A direction) so as to face the recording surface provided on the back surface of the optical disc 51, and the base member 1 has a plurality of bearings 9 that sandwich the guide rail 8 from above and below. Are provided on both sides, and the guide rail 8 is driven by the driving force of a linear motor (not shown).
Move along.

The laser beam L emitted from the fixed optical system 53 enters the reflecting prism 10 arranged in the housing 1a through the passage hole 1c of the base member 1. The laser beam L reflected by the reflecting prism 10 enters the objective lens 3 as shown in FIG. 3, and the objective lens 3 condenses the laser beam L to form a light spot on the recording surface 51a of the optical disc 51. To do. Further, the laser beam L reflected by the optical disk 51 has a fixed optical system in the same optical path as when it is incident.
Incident on 53. Here, the objective lens 3 is held so that the optical axis S _L is orthogonal to the recording surface 51 a of the optical disc 51.

The objective lens actuator is an optical disk
An access operation for moving the base member 1 onto a desired recording track at the time of recording / reproducing with respect to 51, a tracking operation for causing a light spot to follow the swing of the recording track due to the eccentricity of the optical disc 51, and an objective for following the vertical swing of the optical disc 51 The focusing operation for stabilizing the light spot by moving the lens 3 in the optical axis direction is performed.

As shown in the perspective view of FIG. 5, the first leaf spring 5 has a section parallel to the recording surface 51a of the optical disk 51 as a load surface, and the neutral axis S ₁ of the base member 1 is not deformed. It is held so as to be parallel to the radial direction A which is the moving direction. In addition, the optical disk 51 orthogonal to the radial direction A
Assuming that the tangential direction of the outer circumference is B direction and the optical axis direction of the objective lens 3 orthogonal to the recording surface 51a is C direction, the second leaf spring 6 is
A cross section parallel to the B-C plane is configured as a load surface, and is fixed so that the neutral axis S ₂ is parallel to the tangential direction B when not deformed.

The lens holder 2 is made of fiber reinforced plastic, which makes it possible to reduce the weight of the lens holder 2 and increase its rigidity.
A pair of tracking coils is provided on the side surface of the lens holder 2.
11 and a pair of focusing coils 12 are fixed. A pair of tracking magnets 13 each having a yoke 13a fixed to the back surface thereof are arranged on the base member 1 so as to face the pair of tracking coils 11, respectively, and a pair of focusing magnets having a yoke 14a fixed to the rear surface thereof. Magnets 14 are arranged so as to face the focusing coil 12, respectively.

The lens holder 2 is provided with a balance weight 15, and by adjusting the fixing position of the balance weight 15 when the assembly is completed, the lens holder 2, the objective lens 3 and the coil 11, which are integrally formed movable parts, The 12 centers of gravity G are positioned at predetermined positions. As shown in the explanatory view of FIG. 6, when the length of the first leaf spring 5 is L, the center of gravity G of the movable portion is positioned at a position separated from the fixed end of the first leaf spring 5 by L / 2. It Further, the pair of tracking coils 11 are arranged at substantially symmetrical positions of the center of gravity G, and the pair of focusing coils 12 are also arranged at substantially symmetrical positions of the center of gravity G.

The control unit of the optical disk drive apparatus (not shown) sets the direction and current value of the drive current based on the tracking signal and the focus signal obtained by detecting the reflected light from the optical disk 51, and drives this drive. A current is applied to the tracking coil 11 and the focusing coil 12. By applying a drive current to the tracking coil 11, the tracking coil 11 and the tracking magnet 13 which are tracking means apply a couple force F _T1 or a couple force F _T2 about the center of gravity G to the lens holder 2 as shown in FIG. To act on. For example, the couple F _T2 is the lens holder 2
Lens holder 2 rotates the first leaf spring 5 in a counterclockwise direction by bending as shown in FIG. If the bending amount of the first leaf spring 5 is slight, the lens holder 2 is orthogonal to the recording surface 51a of the optical disc 51 and is A-
It rotates about a straight line at a position substantially coincident with the center of gravity G on the B plane. In the lens holder 2, the objective lens 3 is held at a position where the optical axis S _L is separated from the center of gravity G. As a result, the lens holder 2 rotates and the optical axis S _L moves in the radial direction of the optical disc 51. Since the rotation direction and the rotation amount of the lens holder 2 are defined by the direction and current value of the drive current applied to the tracking coil 11, by setting the drive current applied to the tracking coil 11 in correspondence with the tracking signal. The light spot can follow the swing of the recording track on the recording surface 51a.

In this embodiment, the inertial weight around the axis of the lens holder 2 can be balanced by making the position of the axis of the lens holder 2 which is the rotation center line substantially coincide with the center of gravity G. Therefore, it is possible to prevent the lens holder 2 from vibrating due to the rotational inertia force when the lens holder 2 is rotated, and the neutral axis S ₁ of the first plate spring 5 may be attached to the base member 1.
By making it parallel to the radial direction A which is the moving direction of
Since it is possible to prevent the first leaf spring 5 from being bent by the inertial force when the base member 1 is moved, it is possible to suppress the vibration of the lens holder 2 during the access operation.

Further, by adding a driving current to the focusing coil 12, the focusing coil 12 and the focusing magnet 14 which are focusing means are provided.
Applies an upward force F _F1 or a downward force F _F2 to the lens holder 2 in the optical axis direction C. Lens holder 2
When a force F _F2 acts on the optical disc 51, the lens holder 2 bends the second leaf spring 6 as shown in the side view of FIG.
When the lens holder 2 is separated from the lens holder 2 and a force F _F1 is applied to the lens holder 2, the lens holder 2 bends the second leaf spring 6 in the direction opposite to that in FIG. As a result, the focus formed by the objective lens 3 moves in the optical axis direction C. Since the moving direction and the moving amount of the lens holder 2 in the optical axis direction C are defined by the direction and the current value of the driving current applied to the focusing coil 12, the driving current applied to the focusing coil 12 corresponding to the focus signal. By setting, the light spot can be stabilized on the recording surface 51a.

Further, when the second plate spring 6 is bent as shown in FIG. 8, the rigidity of the second plate spring 6 in the direction of the neutral axis S ₂ is changed and the resonance frequency is lowered. Therefore, as shown in FIG. 9, when a force P inclined with respect to the neutral axis S ₂ acts on the second leaf spring 6, a component force P _S acts on the second leaf spring 6 in the direction of the neutral axis S _2. As a result, the second leaf spring 6 easily resonates. In the present embodiment, since the neutral axis S ₂ of the second leaf spring 6 is parallel to the tangential direction B orthogonal to the moving direction of the base member 1, the inertial force during the movement of the base member 1 is the second leaf spring 6. Since the component force in the direction of the neutral axis S _{2 is} not applied to, the second leaf spring 6 can be suppressed from resonating during the access operation.

FIG. 10 is a plan view showing the drive restraining member arranged in the lens holder in this embodiment.

The vibration suppressing member 16 is, for example, a substance having a grease-like viscosity, and in the hollow portion 2a of the lens holder 2, the hollow member 4 and the first leaf spring 5 and the hollow portion 2a.
It is filled with the inner surface. Accordingly, when the first plate spring 5 vibrates, the kinetic energy is absorbed by the vibration suppressing member 16, so that the vibration time of the first plate spring 5 can be reduced and the vibration of the lens holder 2 can be suppressed. it can.

As described above, in this embodiment, the vibration of the lens holder 2 can be suppressed and the lens holder 2 is supported by the first leaf spring 5 and the second leaf spring 6. Since the movement resistance of the lens holder 2 in the rotation direction and the optical axis direction C does not change due to the adhesion of dust or the like, the accuracy of tracking control and focusing control can be improved.

[0033]

As described above, according to the first means of the present invention, the objective lens moves in the radial direction of the objective lens when the first leaf spring is deformed, and the objective lens is moved when the second leaf spring is deformed. By moving in the optical axis direction, the lens holder that holds the objective lens does not slide on other members such as a spindle,
Since the objective lens moves in the radial direction and the optical axis direction,
For example, even if dust or the like is attached, the movement resistance of the lens holder does not change during tracking operation and focusing operation, and tracking control and focusing control can be performed with high accuracy.

Further, according to the second means, when the tracking means is operated, the lens holder rotates about the axis, and when the focusing means is operated, the lens holder moves in the optical axis direction, whereby the objective lens is moved. Can be moved to a desired position in the radial direction of the information recording medium and the optical axis direction of the objective lens.

Further, according to the third means, since the inertial weights of the movable parts around the axis are balanced,
It is possible to prevent the lens holder from vibrating due to the rotational inertia force when the lens holder rotates.

Further, according to the fourth means, since the first leaf spring is prevented from being bent by the inertia force when the base member is moved, the vibration of the lens holder is suppressed when the base member is moved. it can.

Further, according to the fifth means, the inertial force during the movement of the base member does not exert a component force in the direction of the neutral axis on the second leaf spring, so that the second leaf spring bends and the neutral axis is bent. When the rigidity in the direction changes, it is possible to suppress the vibration of the second leaf spring due to the inertial force when the base member moves.

Further, according to the sixth means, when the first leaf spring vibrates, the vibration time of the first leaf spring is reduced, so that the vibration of the lens holder can be suppressed.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of essential parts in an embodiment of an objective lens actuator of the present invention.

FIG. 2 is a plan view of a main part of the present invention.

FIG. 3 is a side view of a main part of the present invention.

FIG. 4 is a plan view showing a schematic configuration of an optical disk drive device to which this embodiment is applied.

FIG. 5 is a perspective view of an intermediate member and a first leaf spring in this embodiment.

FIG. 6 is a plan view of a movable portion in this embodiment.

FIG. 7 is an explanatory diagram of a first leaf spring of this embodiment during a tracking operation.

FIG. 8 is an explanatory diagram of a second leaf spring of the present embodiment during focusing operation.

FIG. 9 is an explanatory diagram of a component force that acts on a second leaf spring of this embodiment.

FIG. 10 is a plan view showing a vibration suppressing member arranged in the lens holder in the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base member, 2 ... Lens holder, 3 ... Objective lens, 4 ... Intermediate member, 5 ... 1st leaf spring, 6 ... 2nd leaf spring, 11 ... Tracking coil, 12 ... Focusing coil, 13 ... Tracking magnet, 14 … Focusing magnet, 16… Vibration suppression member, 51… Optical disc.

Claims (6)

[Claims] 1. An objective lens that condenses a light beam, a lens holder that holds this objective lens and has a hollow portion that penetrates in the optical axis direction of the objective lens, and an intermediate member that is disposed in the hollow portion. A member, a base member that moves along a recording surface of a disc-shaped information recording medium, a first leaf spring that connects the lens holder and the intermediate member, and a second plate spring that connects the base member and the intermediate member. And a leaf spring of
The first leaf spring is bent, the lens holder is rotated about a straight line that is separated from the optical axis of the objective lens and is orthogonal to the recording surface of the information recording medium, and the second leaf spring is bent. An objective lens actuator, wherein the lens holder is configured to move in the optical axis direction. 2. A tracking means for causing a couple of forces centered on the axis to act on the lens holder to bend the first leaf spring, and a force for acting on the lens holder to act on the lens holder. 2. The objective lens actuator according to claim 1, further comprising focusing means for deflecting the second leaf spring. 3. The objective lens actuator according to claim 1, wherein a movable portion which is integrally formed with the lens holder and moves with respect to the base member has a center of gravity at an arbitrary position on the axis. . 4. The objective lens according to claim 1, wherein the neutral axis of the first leaf spring is parallel to the moving direction of the base member when the first leaf spring is not deformed. Actuator. 5. The neutral axis of the second leaf spring is orthogonal to the moving direction of the base member when the second leaf spring is not deformed. Objective lens actuator. 6. The vibration suppressing member having viscosity is filled in a gap between the inner surface of the hollow portion and the first leaf spring and the intermediate member. Objective lens actuator.