JPS6214336A - Optical driving device - Google Patents

Abstract

PURPOSE:To miniaturize a device by forming a supporting axis consisting of a ferromagnetic body and constituting a part of a magnetic circuit with it. CONSTITUTION:In a magnetic circuit consisting of a permanent magnet 6b, a supporting axis 1, a fixed yoke 11 and yokes 5a and 5b, by electromagnetic force generated by magnetic flux between permanent magnets 6a and 6b and the supporting axis 1 and current on a coil 10, and the electromagnetic force generated by magnetic flux H1 and magnetic flux H2 and the current on the coil 10, an objective lens supporting body 3 is slid in upper and lower directions, a focus control is performed. So that an objective lens driving device is constituted, the supporting axis 1 which is formed with the ferromagnetic body and the base plate of which is formed with the fixed yoke 11, magnetic flux density in the magnetic circuit is strengthened, and the supporting axis 1 functions as the inside yoke of the objective lens supporting body 3, eliminate the need for the inside yoke. Thereby, the structure of the device is simplified, with the number of parts reduced, and the device of inexpensive and miniaturized can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical system driving device, and in particular, an optical system holder is provided so as to be at least slidable or rotatable with respect to a support shaft, The present invention relates to an optical system drive device that drives this optical system holder.

[Conventional technology]

Generally, in optical disk devices, magneto-optical disk devices, digital audio devices, etc., tracking control is performed by moving the objective lens in the radial direction of the information recording medium, and focus control is performed by moving the objective lens in the direction perpendicular to the information recording medium. Depending on the situation, a method of reading information from an information recording medium is used.

A conventional objective lens driving device will be described below with reference to the drawings.

FIG. 5 is a perspective view of a conventional objective lens driving device.

FIG. 6(-) is an assembled view of the objective lens driving device, and FIG. 6(b) is a plan view of the plywood portion M in the assembled view of (&).

As shown in FIG. 6(1), the first yoke 1 is placed on the plywood 16.
2, and the support shaft 1 are fixed. An objective lens holder 3 is attached to the support shaft 1 through a bearing member 2. An objective lens 4 is attached to the top of the objective lens holder 3, a first coil 10 is wound around the side surface, and four rectangular second coils 9m are mounted on the first coil.
+9b+9e and 9d are provided. Also, the base plate 16
A permanent magnet 14 is fixed on the top, and a second yoke 15 having two notches is fixed on the permanent magnet 14. As shown in FIG. 5, this second yoke 15 includes the four second coils 9m and 9b.

It is arranged so as to cover part of 9o and 9d. Figure 6 (b
), the base plate 16 has an optical window 13 opened in accordance with the movable range of the objective lens 4.

A first yoke 1 provided inside the objective lens holder 3
The objective lens holder 3 is slid up and down by the electromagnetic force (F+) generated by the magnetic field created between the objective lens holder 2 and the second yoke 15 and the current flowing through the first coil 10, and focus control is performed.

Also, the magnetic field and the second coils 9m+9b, 9c.

The objective lens holder 3 is rotated left and right by the electromagnetic force (F!) generated by the current flowing through the lens 9d, and tracking control is performed.

The tracking performance of the objective lens holder 3 is determined by the electromagnetic force Fl described above.
,F,. This electromagnetic force F1*F1 is expressed by the following equation.

Fl, F, = BINl [N] B: Magnetic flux density [T] I: Current [A] N: Number of turns of the coil [times] l: Strength of the coil in the magnetic field [m] Therefore, in the conventional device, The first yoke 12 and the second yoke 15 were used to configure a magnetic circuit capable of obtaining a high magnetic flux distribution of 1 iB.

[Problem that the invention seeks to solve]

However, the conventional optical system drive device has a complicated structure in which the first yoke 12 is disposed within the objective lens holder 3, resulting in an increase in the number of parts and the manufacturing process. Furthermore, a large hollow objective lens holder is required, which has the disadvantage that the apparatus tends to be large-sized.

[Means for solving problems]

The above problem consists of a support shaft, an optical system holder that is provided to be at least slidable or rotatable with respect to the support shaft, a coil fixed to the optical system holder, and a magnetic field that forms a magnetic field for the coil. The problem is solved by the optical system driving device of the present invention, characterized in that the support shaft is made of a ferromagnetic material and constitutes a part of the magnetic circuit.

〔Example〕

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

In the following description, an objective lens driving device will be discussed as an example of the optical system driving device of the present invention.

FIG. 1 is a perspective view of an objective lens driving device that is an embodiment of the present invention.

FIG. 2 is an assembly diagram of the objective lens driving device.

FIG. 3 is a plan view of the objective lens driving device.

In FIG. 2, a support shaft 1 is fixed to a fixed yoke 11 made of plywood. A yoke 5a, a permanent magnet 6a1, a yoke 5b and a permanent magnet 6b are fixed to both sides of the support shaft 10.

The objective lens holder 3 has an objective lens 4 and a bearing member 2, and has a coil 9m, a coil 9b, and a coil 1 on its side.
0 is set. As shown in FIG. 1, an objective lens holder 3 is installed on the support shaft 1 through a bearing member 2. As shown in FIG.

A permanent magnet 8a and a yoke 7b, and a permanent magnet 8b and a yoke 7b are fixed to a fixed yoke 11 so as to partially cover the coils 9a*9b provided on the objective lens holder 3 thus installed. As shown in FIG. 2, the coils 9m and 9b
are rectangular in shape, and the direction perpendicular to the winding direction of these coils 10 is called A section.

It is called part B.

Next, the operation of the drive device for the optical system will be explained.

FIG. 4 is an explanatory diagram of a magnetic circuit created by the objective lens driving device.

Permanent magnet gm, support shaft 1. Fixed yoke 11. Yoke 7a
The support shaft 1 is moved by the electromagnetic force generated by the magnetic field (Hl) between the permanent magnets 8 in the magnetic circuit and the support shaft 1, and the current flowing through the coil 910B in this magnetic field (Hr). Obtain a centered rotational force. Since the coil 9b is wound in the opposite direction to the coil 9&, the magnetic field (Hm
) and the current flowing through the section A of the coil 9b in this magnetic field (H3).The electromagnetic force generated by this magnetic field (H3) also acts in the same direction as the rotational force.

Therefore, by switching the direction of the current flowing through the coils 9m and 9b, the objective lens holder 3 is rotated left and right, and the objective lens 4 is rotated in the tracking direction (perpendicular to the optical axis), which allows tracking control. It will be done.

On the other hand, the permanent magnet 6b, the support shaft 1° fixed yoke 11. In a magnetic circuit composed of yokes 5a and 5b, the electromagnetic force generated by the magnetic field between the permanent magnets 6m and 6b and the support shaft l and the current flowing through the coil 10, and the magnetic field (Ht) + magnetic field (horse) Due to the electromagnetic force generated by the current flowing through the coil 10, the objective lens holder 3 slides in the vertical direction, and the objective lens 4 moves in the focus direction (optical axis direction) to perform focus control. In order to slide the objective lens holder 3 in the vertical direction, a larger electromagnetic force is required than in the case of rotating it in the horizontal direction.

As mentioned above, the electromagnetic force (F) is expressed by the formula F=BINl(N), and it can be seen from the above formula that the electromagnetic force (F) increases as the magnetic flux density (B) increases.

In the objective lens driving device according to the present invention, the support shaft 1 is made of a ferromagnetic material and the fixed yoke 11 is made of plywood, thereby increasing the magnetic flux density in the magnetic circuit shown in FIG. 3, and the inner yoke is not needed, so the objective lens driving device can be made smaller and lighter.

In the above embodiment, three coils are attached to the objective lens holder, but the number of coils is determined by tracking performance, overlapping of the objective lens holder, etc., and is not limited to three.

〔Effect of the invention〕

As explained above in detail, according to the optical system driving device of the present invention, since the support shaft is made of ferromagnetic material, the magnetic flux density can be increased and the electromagnetic force can be strengthened, thereby improving the tracking performance of the optical system. In addition, since the inner yoke of the optical system holder can be removed, the structure is simple, the number of parts is reduced, and it is possible to provide an inexpensive and compact device. The optical system holder can be driven by electromagnetic force.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an objective lens driving device that is an embodiment of the present invention. FIG. 2 is an assembly diagram of the objective lens driving device. FIG. 3 is a plan view of the objective lens driving device. FIG. 4 is an explanatory diagram of a magnetic circuit created by the objective lens driving device. FIG. 5 is a perspective view of a conventional objective lens driving device. FIG. 6(a) is an assembled view of the objective lens driving device, and FIG. 6(b) is a plan view of the plywood portion in the assembled view of FIG. 6(a). DESCRIPTION OF SYMBOLS 1... Support shaft, 2... Bearing member, 3... Objective lens holder, 4... Objective lens, 5a r 5b r
7m + 7b...Yaw,"#6 b * 8
a r 8 b...Permanent magnet, 9m. 9b, 10... Coil, 11... Fixed yoke.

Claims (1)

[Claims] A support shaft, an optical system holder provided at least slidably or rotatably with respect to the support shaft, a coil fixed to the optical system holder, and a magnetic circuit that forms a magnetic field with respect to the coil. What is claimed is: 1. An optical system drive device comprising: an optical system drive device, wherein the support shaft is made of a ferromagnetic material and constitutes a part of the magnetic circuit.