JPH064888A - Optical pickup actuator - Google Patents

Abstract

PURPOSE:To attain high efficiency by expanding the area of a magnetic circuit and to provide the thin optical pickup actuator of a sliding shaft type. CONSTITUTION:In this optical pickup, a coil bobbin 12 is supported by a yoke base 11 so as to rotate and slide in the shaft direction and by using the coil bobbin 12, a magnetic circuit is composed of a focusing coil 18, a tracking coil 17, a magnet 16 supplying magnetic flux to these coils, an inner yoke 15 and an outer yoke 14 and an objective lens 20 is held by the coil bobbin 12. The objective lens 20 is fixed on a first projecting part 19a protruding laterally from the upper part of the coil bobbin 12, arranged on the outside of the focusing coil 18 and a second projecting part 19b is provided as a counter weight on the opposite side of the first projecting part 19a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup actuator used in an optical disk recording / reproducing apparatus, and more particularly to a shaft sliding type optical pickup actuator which effectively utilizes a magnetic circuit.

[0002]

2. Description of the Related Art An optical pickup actuator is supported by a yoke base, a coil bobbin rotatably supported by the yoke base, and a focusing coil and a tracking coil provided on the coil bobbin, and a coil bobbin. It is composed of an objective lens and the like. Since the optical pickup needs to move between tracks at high speed for access and the like, it is required to prevent vibration of the objective lens and the like and have excellent track following property. It is also desired to make the entire device as thin as possible.

2 (a) and 2 (b) are plan views showing the structure of a conventional shaft sliding type optical pickup actuator, and FIG.
It is an A'cross section figure. Reference numeral 11 is a yoke base, 12 is a coil bobbin, and 20 is an objective lens fixed to the coil bobbin. A shaft 13 of the coil bobbin 12 is rotatably and slidably attached to the yoke base 11. A magnetic circuit is configured by the inner yoke 15, the magnet 16, the focusing coil 18, the tracking coil 17, and the outer yoke 14 that are continuous with the yoke base 11 provided on the coil bobbin 11. As shown in the figure, the magnetic circuit is
The two fan-shaped regions A are symmetrically formed with the region A in between.
In order to improve the balance of driving of the objective lens 20,
A balance weight 31 is attached to the opposite side of the objective lens 20 with the shaft 13 of the coil bobbin 12 interposed therebetween. Below the yoke base 11, a mirror 25 for transmitting a light beam to the objective lens 20 and extracting a return light beam from the objective lens is arranged.

[0004]

In such a conventional optical pickup actuator, since the objective lens 20 is fixed inside the focusing coil 18 of the coil bobbin 12, the effective magnetic field formed in the two fan-shaped regions A is formed. The circuit area is limited, and it is difficult to secure a sufficiently large efficiency in the focus direction. In order to increase the efficiency, it is necessary to increase the cost of parts, for example, to improve the performance of the magnet. Further, in order to secure a driving stroke (about ± 1 mm) in the focus direction and obtain a necessary driving force, the height of the driving portion becomes high, and it is difficult to reduce the thickness. For an optical pickup that is not a shaft-sliding type, a structure has already been proposed in which the objective lens is held outside the focusing coil (Japanese Patent Laid-Open No. 4-28025). However, this can be realized because the weight balance is not so problematic because it is not a shaft sliding type, and it cannot be applied to the shaft sliding type as it is. The present invention has been made in view of such circumstances, and an object thereof is to provide a shaft sliding type optical pickup actuator capable of achieving high performance and thinning at the same time.

[0005]

An optical pickup actuator according to the present invention includes a yoke base, a coil bobbin rotatably supported by the yoke base and slidable in an axial direction, and a focus provided on the coil bobbin. And a tracking coil, and a magnetic circuit composed of a magnet and a yoke for giving a magnetic flux to these coils, and an objective lens supported by the coil bobbin, wherein the objective lens is laterally arranged from an upper portion of the coil bobbin. It is characterized in that it is fixed to the protruding portion and is arranged outside the focusing coil.
In the present invention, preferably, in addition to the projection for supporting the objective lens, a projection as a balance weight projects laterally from the upper portion of the coil bobbin at a symmetrical position with respect to the axis.

[0006]

According to the present invention, in the axial sliding type pickup, the objective lens is arranged outside the position around which the focusing coil of the coil bobbin is wound, so that the fan-shaped area as the magnetic circuit effective area is provided. Without being limited by the objective lens, the angle of the fan-shaped region can be set larger than in the conventional case. As a result, the driving efficiency in the focus direction can be increased. Further, according to the present invention, since a space is formed immediately below the objective lens, an optical component such as a mirror can be arranged there, and the optical pickup can be made thin. Further, by providing a protrusion serving as a balance weight symmetrically with the protrusion for supporting the objective lens, sufficient weight balance can be secured.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are a plan view of an optical pickup actuator according to an embodiment of the present invention and its A--
It is an A'cross section figure. The basic structure is the same as that of the conventional example shown in FIG. 2, and therefore, the parts corresponding to those in FIG. 2 are designated by the same reference numerals. The shaft 13 of the coil bobbin 12 is attached to the yoke base 11 so as to be rotatable and axially slidable. An outer yoke 14 that draws an arc so as to sandwich the coil bobbin 12 is formed integrally with the yoke base 11, and the outer yoke 1 is provided on the outer peripheral portion of the coil bobbin 12.
4, an inner yoke 15 and a magnet 16 are attached so as to face each other, and a focusing coil 18 is wound around this. Furthermore, the tracking coil 1 is provided on the four outer sides.
7 is attached to form a magnetic circuit. The magnetic circuit is formed in two fan-shaped regions B which are symmetrical with respect to the axis 13.

The coil bobbin 12 has a shaft 13 on its upper portion.
Two first and second protrusions 19a and 19b protruding laterally are formed at symmetrical positions with respect to each other. First protrusion 1
Reference numeral 9a is for supporting an objective lens, and a hole through which a light beam passes is formed in this projection 19a, and the objective lens 20 is fixed thereto. That is, the objective lens 20 is arranged outside the focusing coil 18 that constitutes the magnetic circuit. A space is formed on the yoke base 11 directly below the objective lens 20, and a mirror 25 is arranged therein.
The second protrusion 19b is the first protrusion 19a on the objective lens side.
It is for balance weight against.

In the structure of this embodiment, as is apparent from comparison with the conventional example shown in FIG. 2, since the objective lens 20 is provided outside the diameter of the outer yoke 14, it is determined by the outer yoke 14 and the magnet 16. The angle of the fan-shaped magnetic circuit effective area B is
It can be made larger than that of the effective area A in the conventional example. The area efficiency of the magnetic circuit effective area is 66 to 7 with respect to the area determined by the diameter of the focusing coil 18 of the coil bobbin 12.
It is 0%, which is almost twice as efficient as the conventional one. Further, by arranging the mirror 25 directly below the objective lens in parallel with the magnetic circuit, it is possible to reduce the thickness of the entire pickup. Further, the first protrusion 19a for supporting the objective lens 20 and the second protrusion 19b for weight balance are arranged symmetrically with respect to the axis 13, so that good weight balance can be achieved. The present invention is not limited to the above-described embodiment, and various modifications can be made, for example, by providing a weight in the coil bobbin instead of providing the second protrusion 19b for weight balancing.

[0010]

As described above, according to the present invention,
It is possible to obtain a shaft-sliding type optical pickup actuator which is capable of increasing the efficiency by increasing the effective use area of the magnetic circuit and at the same time making it thin.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical pickup actuator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a conventional optical pickup actuator.

[Explanation of symbols]

11 ... Yoke base, 12 ... Coil bobbin, 13 ... Shaft,
14 ... Outer yoke, 15 ... Inner yoke, 16 ... Magnet, 17 ...
Tracking coil, 18 ... Focusing coil, 1
9a ... 1st protrusion, 19b ... 2nd protrusion, 20 ... Objective lens, 25 ... Mirror.

Claims (1)

[Claims] 1. A yoke base, a coil bobbin rotatably and axially slidably supported by the yoke base, a focusing coil and a tracking coil provided on the coil bobbin, and magnetic fluxes on these coils. A magnetic circuit configured by a magnet and a yoke for providing a magnetic field, and an objective lens fixed to a protrusion protruding laterally from an upper portion of the coil bobbin and arranged outside the focusing coil. Optical pickup actuator.