JPH0750234B2 - Optical system drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive device for an optical system, and more particularly to an optical information storage device such as an optical disc device, a magneto-optical disc device, a digital audio device, etc. The present invention relates to a drive device for an optical system that focuses light on a recording medium.

(Prior Art) As an example of the optical information storage device, there is an optical disk device. Generally, in an optical disk device, information pits having a width of 1 to 2 μm and a length of 1 to 3 μm are recorded on a recording medium. Then, in order to read information from this information pit, first, a light beam (normal laser beam) is focused on a minute spot by an optical system such as an objective lens and irradiated on the information pit. At this time, the reflected light or the transmitted light from the recording medium is optically changed depending on the presence or absence of the information pit. By detecting this change with a photodetector, a reproduction signal corresponding to the information pit can be obtained. In an optical disc device having such a structure, it is extremely important that a minute spot always accurately scans an information pit string on a recording medium. Therefore, it is necessary to perform autofocus for correcting a focus shift caused by warp of the recording medium and automatic tracking for correcting an irradiation position shift due to eccentricity of the recording medium.

Conventionally, as an optical system driving device having the autofocus function and the autotracking function, an optical system driving device having a structure shown in FIGS. 5 and 6 is known. That is, the objective lens holding member 1 is composed of a disc-shaped plate portion 1a, an outer cylindrical portion 1b, and an inner cylindrical portion 1c.
The upper part of the support shaft 2 is passed through the bearing hole of 1c and the support shaft 2
The lower part of is fixedly supported by the base 3, and the objective lens holding member 1 is supported rotatably around the support shaft 2 and slidable along the support shaft 2. Further, in the plate portion 1a of the objective lens holding member 1, a pair of yokes 4a and 4b are respectively arranged in a pair of through holes provided at positions symmetrical with respect to the support shaft 2 in the Y-axis direction, and support is provided. The objective lens 5 and the balancer 6 are fitted in a pair of through holes provided at positions symmetrical about the axis 2 in the X-axis direction. 7 is
The focus coil is a focus coil wound around the outer circumference of the objective lens holding member 1. The surface of the focus coil 7 is
The four tracking coils 8a, 8b, 8c, 8d are joined at positions symmetrical with respect to the X-axis direction and at positions facing the yokes 4a, 4b. Further, outside the objective lens holding member 1 so as to face the yokes 4a, 4b, another yoke 9a, 9b is provided on the base 3 so as to face the lower surface of the yokes 4a, 4b and the base 3. A magnetic circuit is configured by the permanent magnets 10a and 10b provided between the two. Further, the objective lens holding member 1
The cylindrical elastic bodies 11a, 11 having both ends fixed to the base 3 so as to contact the objective lens 5 and the balancer 6 provided on the
b is provided oppositely, and when the elastic body 11a, 11b releases the driving force by the magnetic circuit, the objective lens holding member 1 is held at the neutral position and also serves as a damper.

(Problems to be Solved by the Invention) In the optical system driving device configured as described above, the focus coil 7 and the tracking coil 8 are placed in the same magnetic field.
Since both a, 8b, 8c and 8d can be arranged, a compact and lightweight optical system driving device can be provided, but with this structure, the tracking coils 8a, 8b, 8c and 8d are wound independently of each other. Since the individual coils are positioned at a predetermined position on the surface of the focus coil 7 and attached by adhesion, the workability of the attachment is poor, and since the attachment is performed only by adhesion, there is a risk of insufficient attachment strength. Also, the focus coil 7, tracking coils 8a, 8b, and
Since there are 8c and 8d, it is necessary to take out at least two lead wires for each of the focus and tracking from the movable part, a total of four lead wires, which is troublesome to handle, and the lead wires get caught somewhere in the middle. There was a risk that the movement would get worse and the wire would break.

The present invention has been made for the purpose of solving the above-mentioned conventional problems, and aims to provide an optical system drive device that is small in size and light in weight and has improved workability in attaching an optical system drive unit for performing focusing and tracking. To do.

(Means for Solving Problems) As means for solving the above-mentioned conventional problems, the present invention is capable of rotating around a support shaft and sliding in the axial direction of the support shaft. In an optical system driving device having an optical system holding member and an optical system having an optical axis provided at a position separated from the support shaft substantially parallel to the support shaft, the optical system holding device is provided on an outer peripheral surface of the optical system holding member. The optical system driving unit includes a magnetic plate and an optical system driving unit which is arranged outside the optical system holding member so as to face the magnetic plate and cooperates with the magnetic plate to form a magnetic path. Is a yoke, first and second electromagnets, each of which is composed of a coil and a magnetic core, arranged in parallel in a direction substantially parallel to the spindle about the yoke, and the spindle about the yoke. A third parallel to the orthogonal direction, each consisting of a coil and a magnetic core A fourth electromagnet, a yoke plate connected to the yoke and the magnetic cores of the first, second, third, and fourth electromagnets, and a yoke plate disposed on the back surface of the electromagnet, By controlling the magnitude of excitation of the first and second electromagnets, the position of the optical system holding member in the axial direction of the support shaft is controlled to control the magnitude of excitation of the second and third electromagnets. By doing so, the gist is a configuration for controlling the rotational position of the optical system holding member around the support shaft.

(Operation) With the above configuration, it is not necessary to dispose the focus coil and the tracking coil on the optical system holding member, so that the reliability of the autofocus function and the autotracking function can be improved.

(Examples) Hereinafter, the present invention will be described in detail with reference to illustrated examples.
1 and 2 are a plan view and a sectional view of an optical system driving device according to the present invention, in which 101 is an objective lens holding member, which is a disk-shaped plate portion 101a and an outer cylindrical portion 101b. It consists of the inner cylindrical part 101c, and the support shaft 10 is inserted in the bearing hole of the inner cylindrical part 101c.
2 penetrates the upper part, and the lower part of the support shaft 102 is the base 103
Is fixedly supported by the objective lens holding member 101.
Are supported rotatably around the support shaft 102 and slidable along the support shaft 102. Further, in the plate portion 101a of the objective lens holding member 101, the objective lens 104 and the balancer 105 are fitted in a pair of through holes provided at positions symmetrical with respect to the X axis about the support shaft 102. Reference numerals 106a and 106b denote magnetic plates that are provided on the outer peripheral surface of the objective lens holding member 101 so as to face each other in the X-axis direction.
07b are arranged on the base 103 so as to closely face each other. As shown in FIG. 3, the objective lens driving units 107a and 107b include electromagnets 109 and 110 composed of magnetic cores and coils in the Y-axis direction, and electromagnets 111 and 112 composed of magnetic cores and coils in the Z-axis direction around the yoke 108. They are arranged opposite to each other and are arranged on the base 103 via magnetic yoke plates 113 joined to the rear surfaces of the yoke 108 and the electromagnets 109, 110, 111, 112. 114
a and 114b are elastic members of a cylindrical portion whose both ends are fixed to the base 103 so as to come into contact with the objective lens 104 and the balancer 105, and the magnetic plates 106a and 114b are made by the elastic members 114a and 114b.
When the driving force by the magnetic circuit configured by 106b and the objective lens driving units 107a and 107b is released, the objective lens holding member 10
Holds 1 in the neutral position and also acts as a damper.

The optical system driving device according to the present invention is constructed as described above, and in order to perform tracking as shown in FIGS. electromagnet
When no current is applied to 109 and 110, no driving force acts on the objective lens holding member 101 and the objective lens holding member 101 is positioned at the neutral point by the neutral point holding mechanism (not shown) (FIG. 4 (a)). Next, as shown in FIG. 4B, a current is applied to one of the electromagnets 109 to generate a magnetic force and magnetic plates 106a and 106b provided on the outer peripheral surface of the objective lens holding member 101 (FIG. 4B). Is the magnetic plate 106
b) and a magnetic circuit are constituted, a driving force for rotating the objective lens holding member 101 to the left acts, and this driving force and a force for returning to the neutral point by the neutral point holding mechanism (not shown) The objective lens 101 stops at the balanced position. And
As shown in FIG. 4 (c), also when a current is applied to the other electromagnet 110, a driving force for rotating the objective lens holding member 101 to the right acts in the same manner, and this driving force and the neutral point holding mechanism are used. The objective lens 101 stops at a position where the forces for returning to the neutral point are balanced by (not shown). Therefore, tracking control of the objective lens 104 can be performed by controlling the magnitude of excitation of the electromagnets 109 and 110.

Similarly, when focusing is performed, a current is applied to the electromagnets 111 and 112 oppositely arranged in the Z-axis direction.
Focusing control of the objective lens 104 can be performed by controlling the magnitude of excitation of 11,112.

In the above-mentioned embodiment, the case where only the objective lens is driven has been described, but the present invention is not limited to this, and the whole optical system including a light source and the like may be driven.

(Effects of the Invention) The present invention has been described in detail above, and is arranged so as to face the magnetic plate provided on the outer peripheral surface of the optical system holding member and the outside of the optical system holding member. And an optical system driving section that cooperates with the magnetic plate to form a magnetic path, and the optical system driving section is arranged in parallel with the yoke in a direction substantially parallel to the support shaft about the yoke. , A first electromagnet and a second electromagnet, each of which includes a coil and a magnetic core, are arranged in parallel in a direction substantially orthogonal to the spindle about the yoke.
Third and fourth electromagnets each consisting of a coil and a magnetic core, and arranged on the back surface of the yoke and the electromagnet, which are connected to the yoke and the magnetic cores of the first, second, third, and fourth electromagnets, respectively. And a yoke plate, the position of the optical system holding member in the axial direction of the support shaft is controlled by controlling the magnitude of excitation of the first and second electromagnets, and the second and third electromagnets are controlled. By controlling the magnitude of excitation of the electromagnet, the rotational position of the optical system holding member around the support shaft is controlled.

Therefore, this optical system driving device is small and lightweight, and has high workability and reliability. Moreover, by sharing the yoke with a plurality of electromagnets, it is possible to achieve the effect of sufficiently miniaturizing the device. To be

[Brief description of drawings]

FIG. 1 is a plan view of an optical system driving device according to the present invention, and FIG.
FIG. 3 is a sectional view of the same, FIG. 3 is a perspective view of an optical system driving section according to the present invention, and FIGS. 4 (a), (b), and (c) are explanatory diagrams showing a tracking operation, and FIG. FIG. 6 is a plan view of an optical system driving device in a conventional example, and FIG. 6 is a sectional view of the same. 101 ... Objective lens holding member, 102 ... Spindle, 103 ... Base, 104 ... Objective lens, 106a, 106b ... Magnetic plate, 107a, 1
07b …… Objective lens drive, 108 …… Yoke, 109,110,11
1,112 …… Electromagnet.

Claims (1)

[Claims] 1. An optical system holding member that is rotatable around a support shaft and is slidable in the axial direction of the support shaft, and an optical axis is substantially parallel to the support shaft at a position separated from the support shaft. In an optical system driving device having an optical system provided in the optical system holding member, the magnetic plate is provided on the outer peripheral surface of the optical system holding member, and is arranged outside the optical system holding member so as to face the magnetic plate. And an optical system driving unit that cooperates with the magnetic plate to form a magnetic path, and the optical system driving unit is arranged in parallel with the yoke in a direction substantially parallel to the support shaft with the yoke as a center. First and second, each consisting of a coil and a magnetic core
Electromagnets and third and fourth electromagnets each of which is composed of a coil and a magnetic core and which are arranged in parallel in a direction substantially orthogonal to the support shaft with the yoke as a center, the yoke, the first and the second,
A yoke plate connected to the magnetic cores of the third and fourth electromagnets and arranged on the back surface of the electromagnet,
By controlling the magnitude of excitation of the first and second electromagnets, the position of the optical system holding member in the axial direction of the support shaft is controlled, and the magnitude of excitation of the second and third electromagnets is controlled. The optical system driving device is characterized in that the rotational position of the optical system holding member around the support shaft is controlled by controlling the.