JPH05189781A - Objective lens actuator - Google Patents

Abstract

PURPOSE:To miniaturize the objective lens actuator and to improve its follow-up performance by integrating a lens holder part and a coil holder par on in a moving part, disposing a coil on the outer periphery of the moving part and moving the moving part so as to slide with the oil-less bearings of a stationary part as sliding surfaces. CONSTITUTION:The lens holder 3 which is the moving part is constituted of the lens holder part 3a and the coil holder part 3b. The holder part 3a fixes and supports the objective lens 1 at its inside end and the holder part 3 fixes and supports the coil 6. A yoke 8 in the stationary part is concentrically constituted of an inside yoke 8a, an outside yoke 8b and the connecting part thereof. The inside yoke 8a consists of a magnetic path material and the outer peripheral part thereof is disposed with the oil-less bearing 4 consisting of 'Teflon(R)', etc. A permanent magnet 7 is fixed to the outer yoke 8b and a magnetic circuit is constituted of the entire part of the yoke 8. The holder 3 is disposed freely slidably in the optical axis direction with the oil-less bearings on the inner periphery of the holder part 3b and the outer periphery of the inside yoke 8a as the sliding surfaces.

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 which is applied to an optical disk drive device and focuses a light beam on a recording surface of an information recording carrier.

[0002]

2. Description of the Related Art Generally, an optical disk drive device is provided with an objective lens actuator for focusing in response to vertical movement of a rotating disk surface for non-contact reproduction.

FIG. 3 is a sectional view showing an example of an objective lens actuator. 1 is an objective lens, 2 is a light beam,
3 is a lens holder, 4 is a non-lubricated bearing having a small friction coefficient such as Teflon, 5 is a coil holder, 6 is a coil, 7
Is a permanent magnet and 8 is a yoke.

The light beam 2 incident on the objective lens 1 is condensed to form a light spot. In order to always track this light spot according to the change of the disc, the objective lens 1
Need to be operated in the optical axis direction (direction of arrow A). The objective lens 1 is coaxially attached to the lens holder 3, and the lens holder 3 and the unlubricated bearing 4 made of Teflon or the like are slidably supported in the optical axis direction with a small friction coefficient. A coil 6 is arranged in a magnetic gap 9 formed by a permanent magnet 7 and a yoke 8 via a coil holder 5 fixed to the coil holder 5, and a tracking current is applied to the objective lens 1 by applying a predetermined current to the coil 6. Is.

[0005]

In the above-mentioned objective lens actuator, X which is orthogonal to the optical axis of the objective lens 1 is used.
What is arranged on the axis (direction of arrow X) is the lens holder 3, the unlubricated bearing 4, the inner yoke 8a, the coil 6,
The order is the outer yoke 8b, where the inner yoke 8a and the coil 6 are
There is a certain space between and. Therefore, the objective lens 1
And the distance x between the coil 6 and the coil 6 becomes long, and the rigidity of the coil holder 5 decreases. Further, the coil 6 has a structure in which a wire is wound alone, and is fixed on the circumference of the coil holder 5. Therefore, the rigidity of the coil 6 and the connecting portion of the coil 6 and the coil holder 5 is also low.

If the rigidity of the joint between the coil 6, the coil holder 5, and the coil 6 and the coil holder 5 that constitute the movable portion of these objective lens actuators is low, the tracking operation of the objective lens 1 according to the change of the optical disk can be performed. However, there is a problem in that even if a predetermined current is applied to the coil, the current is not smoothly applied. Further, since there is a fixed space between the inner yoke 8a and the coil 6, there is a problem that the objective lens actuator cannot be downsized.

In order to solve the above problems, an object of the present invention is to improve the followability of the condenser lens by increasing the rigidity of the movable portion of the objective lens actuator, and to eliminate the need for a space between the inner yoke and the coil. To provide a smaller objective lens actuator.

[0008]

In order to achieve the above object, the present invention provides an objective lens for focusing a light beam on a recording surface of an information record carrier and a position of a light spot focused by the objective lens. In an actuator that moves in the recording direction, a lens holder portion that fixedly supports an objective lens, and a coil holder portion that fixedly supports a coil formed by winding a wire around an outer peripheral portion as a core material and has a sliding surface inside. A fixed part that forms a magnetic circuit with an inner yoke that is made of a magnetic path material, and has an outer peripheral part that is a sliding surface, and an outer yoke that is arranged to face the inner yoke and fixedly supports a permanent magnet. It is characterized in that it is slidably fitted to the section.

Furthermore, at least one of the sliding surface of the movable portion and the sliding surface of the fixed portion is coated with a low friction substance.

[0010]

According to the above means, the coil has a structure in which the outer circumference of the lens holder, which is the movable part of the objective lens actuator, is used as the core material and the wire is wound around the coil. By eliminating the connecting portion between the coil and the coil holder, the rigidity of the connecting portion does not decrease. In addition, the coil holder part corresponding to the coil holder in the conventional example and the lens holder are integrated,
Since the movable part and the fixed part perform a sliding motion along the sliding surface, the rigidity of the entire movable part is increased and the size can be reduced.

Further, by coating a sliding surface of at least one of the movable portion and the fixed portion with a low friction substance,
Since an unlubricated bearing which is an elastic body and has a certain thickness is unnecessary, the vertical sliding motion of the movable portion can be accurately performed, and the objective lens actuator can be further miniaturized.

[0012]

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

FIG. 1 is a sectional view showing a first embodiment of the present invention. A lens holder 3 which is a movable portion of an objective lens actuator corresponds to a lens holder portion 3a having a small diameter and a conventional coil holder. The coil holder 3b has a large diameter. The lens holder portion 3a fixedly supports the objective lens 1 at an inner end portion thereof, and the coil holder portion 3b fixedly supports a coil 6 having a wire rod wound around an outer peripheral portion as a core material.

The yoke 8 of the fixed portion of the objective lens actuator is composed of an inner yoke 8a concentrically, an outer yoke 8b facing the inner yoke 8a, and a connecting portion thereof. The inner yoke 8a is made of a magnetic path material, and a non-lubricated bearing 4 having a small friction coefficient, such as Teflon on the outer peripheral portion thereof, having an elastic force and a constant thickness, is arranged.

A permanent magnet 7 is fixedly supported on the outer yoke 8b, and the entire yoke 8 constitutes a magnetic circuit. A space between the inner yoke 8a and the outer yoke 8b forms a magnetic gap 9. ing.

The lens holder 3 is disposed so as to be slidable in the optical axis direction, with the inner peripheral portion of the coil holder portion 3b and the non-lubricated bearing on the outer peripheral portion of the inner yoke 8a of the fixed portion serving as sliding surfaces.
Then, by applying a predetermined current to the coil 6 of the lens holder 3, the objective lens 1 performs a tracking operation in the optical axis direction.

FIG. 2 is a sectional view showing a second embodiment of the present invention, in which at least one sliding surface of the coil holder 3 and the yoke 8 which is a fixed portion has a low friction material such as Teflon or a fluororesin. By coating, it is possible to eliminate the need for the unlubricated bearing 4 having a constant thickness.

[0018]

As described above, according to the present invention,
In the movable part, the lens holder part and the coil holder part are integrated, the coil is arranged on the outer peripheral part of the movable part, and the movable part performs sliding motion with the non-lubricated bearing of the fixed part as the sliding surface. As a result, it is possible to provide a compact objective lens actuator having high tracking performance.

Further, when at least one of the sliding surfaces of the movable portion and the fixed portion is coated with a low-friction substance, a non-lubricated bearing is not required, and it is possible to provide a compact objective lens actuator having high tracking performance.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of a first embodiment of an objective lens actuator of the present invention.

FIG. 2 is a sectional view showing the configuration of a second embodiment of the objective lens actuator of the present invention.

FIG. 3 is a sectional view showing a configuration of a conventional objective lens actuator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Objective lens, 2 ... Light beam, 3 ... Lens holder, 3a ... Lens holder part, 3b ... Coil holder part,
4 ... Unlubricated bearing, 6 ... Coil, 7 ... Permanent magnet, 8 ... Yoke, 8a ... Inner yoke, 8b ... Outer yoke, 9 ... Magnetic air gap.

Claims (2)

[Claims] 1. An objective lens for focusing an optical beam on a recording surface of an information recording carrier, and an actuator for moving a position of a light spot focused by the objective lens with respect to a recording direction, the objective lens is fixedly supported. A movable part, which is made of a magnetic path material and has a movable part, which integrally supports a lens holder part, a coil in which a wire is wound around the outer peripheral part as a core material, and a coil holder part whose inside is a sliding surface The objective lens is slidably fitted to a fixed portion forming a magnetic circuit by an inner yoke whose portion is a sliding surface and an outer yoke which is arranged to face the inner yoke and fixedly supports a permanent magnet. Actuator. 2. An objective lens actuator, wherein at least one of a sliding surface of a movable portion and a sliding surface of a fixed portion is coated with a low friction substance.