JPH0452812Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention is an optical pick-up for optically reading signals recorded on recording media such as video discs and audio compact discs. The present invention relates to an actuator that movably supports an optical system including a lens.

[Conventional technology]

A conventional actuator for this type of optical system pickup is shown in FIGS. 3 and 4, and will be described below.

1 is an objective lens, 2 is a holder for an optical system including the objective lens 1, 3 is a focus coil for moving the holder 2 in the direction of arrow Z in FIG. 3, and 4 is a holder 2
The focus coil 3 and the tracking coil 4 are fixed to predetermined positions of the holder 2 by adhesive or the like.

5 is a magnet, and 6 is a U-shaped yoke. The magnet 5 is fixed to one of the opposing surfaces of the U-shape, and the focus coil 3 is fitted to the opposite opposing surface. A focus coil 3 and a tracking coil 4 are located within the magnetic gap between the U-shaped opposing surfaces of the magnetic circuit thus formed.

The yoke 6 is fixedly supported by a fixed member (not shown), and the holder 2 is supported movably in the X and Z directions.

Therefore, the magnetic flux generated in the magnetic gap is generated in the direction of the arrow Y in the figure, while a current flows in the long side of the focus coil 3 located within the magnetic gap in the direction of the arrow X.

Therefore, according to Fleming's law, arrow Z
A driving force is generated in the direction of , that is, the focus direction.

Further, in the tracking coil 4, a force according to Fleming's law is generated only in the portion located within the magnetic gap and through which current flows in the Z direction, thereby generating a driving force in the direction of arrow X, that is, in the tracking direction.

[Problem that the invention attempts to solve]

In order to drive the actuator of the optical system pickup as described above, it is desirable that the center of the driving force be located at the center of gravity of the actuator.

This is to avoid imparting a moment in an unnecessary direction to the holder 2 containing the objective lens 1.

However, in the optical system pickup actuator described above, the point of effort F by the focus coil 3 is the point of effort T by the tracking coil 4, and it is not possible to make them coincide.

Therefore, even in the best case, either the force point F or T may be deviated from the center of gravity, resulting in the generation of a moment in an unnecessary direction.

[Purpose of invention]

The present invention is intended to eliminate the above-mentioned drawbacks of the actuator of the conventional optical pickup.The present invention is designed to make the driving force for the actuator coincide with the center of gravity in both the focusing direction and the tracking direction, and to avoid unnecessary moments in the direction. The purpose is to eliminate various obstacles caused by the addition of

[Summary of the idea]

In order to achieve the above-mentioned purpose, the present invention divides the focus coil into two parts, installs a tracking coil between them, aligns the driving force points of the focus coil and the tracking coil, and adjusts this driving force point. The gist of this is to align the centers of gravity of the holder and the optical system.

[Example of idea]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

1 is an objective lens; 2 is a holder for an optical system including the objective lens 1;

13 is a focus coil, divided into two pieces,
The planar shape is wound into a substantially rectangular shape, and a tracking coil 14 is positioned between the two divided focus coils 13.

Reference numeral 16 denotes a yoke bent in a U-shape, and two magnets 15 are glued to the opposing surfaces of the U-shape with their oppositely polarized surfaces facing each other to form magnetic poles, and a magnetic gap is formed between the magnetic poles. .

The focus coil 13, which is divided into two parts and wound into a plane rectangular shape, is attached to the holder 2 so as to fit into each of the magnetic poles.

Therefore, the magnetic flux passing through the magnetic gap is in the Y direction of the arrow in FIG. 1, and the current flowing through the focus coil 13 is in the X direction in the magnetic gap.
As in the conventional case, a force is generated in the focus coil 13 in the Z direction, that is, in the focus direction.

Further, since the current effective for the magnetic gap in the tracking coil 14 is in the Z direction, the force applied to the tracking coil 14 is in the X direction, that is, the tracking direction, as in the conventional case.

However, the focus coil 13 is divided into two parts,
Since the same force is generated in each of them, the combined force point will be in the middle of the two divisions.

In this intermediate position, the tracking coil 14
Since this position is located, the force point of the tracking coil 14 and the force point of the focus coil 13 at this position match.

Therefore, if the center of gravity of the optical system including the objective lens 1 and the holder 2 are made to coincide with the above-mentioned point of force, both the tracking driving force and the focus driving force will act on the center of gravity.

[Effect of idea]

As mentioned above, this invention uses two focus coils.
Since the focus coil is divided into two parts and a tracking coil is installed between them, by aligning the driving force points of the focus coil and the tracking coil, and by aligning this driving force point with the center of gravity of the holder and the optical system, it is possible to avoid unnecessary directions. This can prevent the moment from occurring.

Therefore, tilting of the optical system due to moments in unnecessary directions and various other problems can be prevented.

Furthermore, since the different poles of the two magnets are opposed to each other, a good magnetic circuit with very little leakage magnetic flux is formed, and an efficient actuator can be obtained.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of one embodiment of the present invention;
3 is an exploded perspective view of a conventional optical pickup actuator, and FIG. 4 is a plan view thereof. 1... Objective lens, 2... Holder, 13... Focus coil, 14... Tracking coil,
15...Magnet, 16...Yoke.

Claims (1)

[Scope of utility model registration request] The yoke is formed in a U-shape and has magnets fixed to its two opposing sides so that magnetic flux is generated in the opposing direction. An actuator for an optical pickup, characterized in that it comprises a focus coil that is wound so as to surround it, and a tracking coil that is positioned between the two divided focus coils.