JPS6142747A - Actuator - Google Patents

Abstract

PURPOSE:To prevent oscillations of high order and to stabilize control by displacing an objective lens in a focus direction by a parallel leaf spring and in a track direction around the axis of rotation. CONSTITUTION:An actuator generates a vertical driving force with magnetic flux produced by a magnetic circuit 21 when an electric current flows through a focus coil 13. Then, a focus spring 15 consists of the couple of upper and lower parallel leaf springs, so the objective lens 11 oscillates in a direction nearly coincident with an optical axis from an optical system. Thus, the objective lens 11 is displaced around the axis of rotation in the focus direction, so the motion in the track direction becomes stable to prevent resonance of high order and stabilize the control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an actuator for an optical pickup. More specifically, it relates to a method for driving an objective lens and a method for maintaining a neutral point. [Prior art] A method for driving an objective lens in an actuator that is conventionally structured to deflect an objective lens in the focus direction and the track direction is shown in FIG. As shown in FIG. The holder 4 is arranged at an angle of 90 degrees with respect to the focus spring 5 so that the objective lens holder 2 can move in parallel in the track direction, and is held by a track spring 5 in the form of a parallel leaf spring. It was usually fixed at .

[Problem that the invention seeks to solve]

However, in the case of this method, there is no particular problem with driving in the focus direction, but when driving in the track direction, the excitation point is the objective lens holder 2, so the deflection force to the track spring 5 is Since the transmission is transmitted via the focus spring 3, a resonance mode in the width direction of the focus spring 3 occurs, which not only causes high-order resonance but also causes a vibration in the track spring 5.
However, it has the disadvantage that buckling phenomenon tends to occur easily.

Therefore, in order to solve these conventional drawbacks, this invention aims to provide an actuator with a structure that prevents high-order resonance from occurring even when it is vibrated, and that allows the hour wheel to maintain a neutral point. There is.

[Means for solving problems]

In order to solve the above problems, this invention uses a plate spring in the focus direction and a shaft and a bearing in the track direction to create rotational motion, thereby preventing high-order resonance from occurring. By providing a magnetic material in the part located in the gap, the neutral point is maintained.

[Effect]

In the actuator configured as described above, since the track direction is rotational motion, resonance mode in the width direction of the focus spring is extremely unlikely to occur in contrast to parallel interlocking, and since no track spring is used, buckling of the track spring occurs. will not occur, and therefore higher-order resonance will be smaller and less likely to occur.

In addition, simply by providing a magnetic material in the part of the objective lens holder located in the gap of the magnetic circuit, it is possible to generate a neutral point holding force according to the amount of displacement from the center when the objective lens holder moves in the track direction. be.

〔Example〕

The structure of a preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of an actuator according to the present invention, and FIG. 6 is a plan view of the actuator according to the present invention. The objective lens 11 is held by an objective lens holder 12. A focus coil 15 is wound around the objective lens holder 12 in the plan view of FIG. 2, and two track coils 14 are attached to one side of the objective lens holder 12. Further, a focus spring 15 in the form of a parallel plate spring is fixed to upper and lower sides of the side surface of the objective lens holder opposite to the surface to which the track coil 14 is attached, and the other end of the focus spring 15 is attached to the spring holder 16. Fixed.

The spring holder 16 is configured to deflect the objective lens 11.
An axis 17 is provided parallel to the optical axis. 1B is a bearing holder, and bearings 19 made of artificial jewels are mounted on the upper and lower sides of the bearing holder, and the shaft 17 is rotatably supported. Reference numeral 20 indicates a floor plate to which the bearing holder 18 is fixed. Further, a magnetic circuit indicated by the reference numeral 21 is fixed to the floor plate 20, and a coil portion of the objective lens holder 12' is disposed in the gap portion of the magnetic circuit 21. Reference numeral 22 denotes a magnet of the magnetic circuit 21, which is magnetized in the thickness direction.

Reference numeral 25 denotes a small piece of iron, which is located in the gap of the magnetic circuit 21 at the center of the track coil 14 and attached to the objective lens holder 12.

FIG. 4 shows another embodiment of the invention. A ball bearing 24 is used instead of the artificial jewel of the bearing 19. FIG. 5 is a plan view thereof.

6 and 7 show another embodiment of the invention. The present invention has the above structure, and the operation of the present invention will be explained below with reference to the drawings. explain. First, the focus direction will be explained. When a current flows through the focus coil 13, a driving force is generated in the vertical direction due to the magnetic flux generated by the magnetic circuit 21. The driving force is transmitted to the objective lens holder 12, which vibrates up and down while being supported by the focus spring 15. Since the focus spring 15 is composed of a pair of upper and lower parallel plate springs, the objective lens 11 can vibrate in a direction that substantially coincides with the optical axis from the optical system.

Next, the track direction will be explained. When a current flows through the track coils 1, 4, the magnetic flux generated by the magnetic circuit 21 generates a driving force in the track direction. The driving force is transmitted to the objective lens holder 12, which rotates and reciprocates about the shaft 17.

Furthermore, since the bearing 19 is made of artificial jewelry, it can rotate with less friction. Since the bearing 24 is made of a ball bearing, it can rotate with less friction like artificial jewelry.

In particular, artificial jewelry has excellent abrasion resistance and is therefore highly reliable during long-term use.

Then, a force is generated that tends to pull the objective lens holder 12 back to the center due to the attractive force between the small iron piece provided in the gap of the magnetic circuit and the magnet. This force acts as a holding force at the neutral point.

〔Effect of the invention〕

Since this invention has the structure and operation described above, in other words, it has a structure in which the objective lens 11 is deflected in the focus direction by a parallel plate spring, and in the track direction about the rotation axis. As a result, the movement in the track direction is very stable, and the objective lens does not tilt during track deviation, so high-order resonance does not occur and the actuator has very high performance. Become. Furthermore, by arranging artificial jewels and ball bearings in the bearing part, stable control characteristics can be obtained with almost no friction. Moreover, simply attaching the small magnetic piece 23 to the objective lens holder 12 has the effect of generating a force for holding the neutral point.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of the present invention FIG. 2 is a plan view of the conventional example FIG. 3 is a plan view of the present invention FIG. 4 is a side sectional view of another embodiment of the present invention FIG. 5 is a side sectional view of another embodiment of the present invention Plan view FIG. 6 Plan view of another embodiment according to the present invention FIG. 7 Side sectional view of another embodiment according to the present invention 1 Objective lens 2 Objective lens holder 5 ... Focus spring 4 ... Spring holder 5 ... Track spring 11 ... Objective lens 12 ... Objective lens holder 15 ... ... Focus spring 16 ... Spring holder 17 ... Shaft 18 ... Bearing holder 19 ... Bearing 21 ... Magnetic circuit 26 ... ...Small iron piece 24 ... Ball bearing. Figure 1 Figure 3 Figure 4 Figure 5 Figure 6

Claims (4)

[Claims] (1) An objective lens, an objective lens holder that holds the objective lens, and one or more pairs of focus springs that are arranged in parallel and have one end fixed to the objective lens holder to move the objective lens parallel to the optical axis. a spring holder having a shaft for holding the other end of the focus spring and rotationally deflecting the objective lens with respect to the track direction;
a bearing holder having a bearing that supports the shaft of the spring holder;
An actuator comprising: a magnetic circuit for generating a driving force for an objective lens holder in a focus direction and a track direction; and a magnetic body provided on the objective lens holder. (2) The actuator according to claim 1, wherein the bearing is an artificial jewel. (3) The actuator according to claim 1, wherein the bearing is a ball bearing. (4) The actuator according to claim 1, wherein the magnetic material is a ferromagnetic material.