JPS6232530B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical system drive device in a recorded information reading device.

In an optical recording information reading device, a video disk, which is an information recording medium, records a video signal by forming minute pits (indentations) corresponding to the video signal as a spiral track on its surface. It is. When playing back such a video disc, the disc is rotated at a predetermined number of revolutions while a spot light is irradiated onto the video track, and changes in the intensity of the reflected light or transmitted light are converted into electrical signals, and the changes in the intensity of the reflected light or transmitted light are converted into electrical signals. It is something to be regenerated.

When playing back video discs, the irradiated light must be accurately focused on the recording surface of the disc, so it is necessary to control the position of the optical system in the direction perpendicular to the recording surface, that is, in the focus direction (focus servo). In addition, since the irradiation light must always accurately track the recording track, it is necessary to control the irradiation light in the radial direction of the disk, that is, in the tracking direction (tracking servo). In order to eliminate axis fluctuations, it is necessary to control the track connection direction of the irradiation light, that is, the tangential direction (tangential servo). For this purpose, an optical system driving device is used that drives an optical system that irradiates the recording surface of the disk with spot light for reading information in accordance with a focus error signal, a tracking error signal, and a tangential error signal. A conventional example of such an optical system driving device is shown in FIGS. 1 and 2.

In FIG. 1, for example, there are 4
Four magnetic circuit sections 2a to 2d are provided at an angle of approximately 90 degrees to each other in a plane orthogonal to the optical axis Z of the optical system 1, and four coils are arranged in the magnetic gaps of these magnetic circuit sections. The parts 3 a to 3 d are attached to the optical system 1 via a support 4 . The optical system 1 can be driven in the optical axis Z direction, that is, in the focus direction, by supplying equal currents in the same direction to each of the coil parts 3a to 3d. On the other hand, the coil parts 2a and 2b, 2c, and 2d are each paired,
In addition, the coil parts 2a and 2d, and 2b and 2c are arranged as pairs, and by supplying currents in opposite directions to each pair, the optical system 1 can be driven in the tracking direction or the tangential direction (X and Y directions in the figure). ing. Note that FIG. 1a is a plan view with the support body 4 removed, and FIG. 1b is a sectional view thereof.

On the other hand, in FIG. 2, the coil portion 5 is located around the optical axis Z of the optical system 1, and the axes X and Y, which include the optical axis Z and are orthogonal to each other, are located in a plane orthogonal to the optical axis Z. Around the coil parts 6a, 6b and 7
These coil parts are attached to the optical system 1 so that the coil parts a and 7b are located respectively, and the magnetic circuit parts 8, 9a, 9b and 1 supply magnetic flux to each coil part.
0a and 10b are provided. By supplying current to the coil portion 5, the optical system 1 can be driven in the focus direction Z, and the coil portions 6a and 6b can be driven.
Alternatively, the optical system 1 can be independently driven in the tracking direction X or the tangential direction Y by supplying current to 7a and 7b. Note that FIG. 2a is a plan view, and FIG. 2b is a sectional view thereof.

The conventional example described above has the following drawbacks. That is, in the former case, the optical system 1 moves in parallel in the focus direction, but in the tracking and tangential directions, it is not a parallel movement but a swinging movement, which is optically disadvantageous, such as lens aberration.
In the latter case, the optical system 1 can be moved in parallel in each direction, but the mechanism becomes larger. Furthermore, both require a plurality of drive units for multidimensional drive, which is disadvantageous in terms of space factor and cost.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an optical system drive device in a recorded information reading device that can be made smaller and lighter.

In the optical system drive device according to the present invention, the bobbin is attached to the optical system so as to be located within the gap of the magnetic circuit section having an annular magnetic gap, and the coil surface (winding a coil section including first and second coils that are wound around the outer periphery of a bobbin so that a plane passing through the center of the distribution of is provided, and is configured to drive the optical system in a direction parallel to the bobbin center axis and in a direction perpendicular to the center axis by controlling the current supplied to the coil portion.

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

FIG. 3 is a sectional view showing one embodiment of the present invention. In the figure, a rectangular bobbin 12 is attached to the optical system 11 so that its central axis coincides with the optical axis Z of the optical system 11. As shown in FIG. 4, the first coil 21 is wound around the outer circumference of the bobbin 12 so that the coil surface is inclined with respect to the optical axis Z.
A second coil 22 is wound around the first coil at an angle of approximately 180° with respect to the optical axis Z. As a result, the line of intersection between the coil surfaces of the first and second coils is approximately perpendicular to the optical axis Z, and the first coil 21 is attached to the bottom surface of the bobbin 12 at one opposing surface A, A'. and the other facing surface B,
At B′, it becomes parallel to the bottom surface. Further, the second coil 22 intersects the first coil 21 at opposing surfaces A and A', and is parallel to the bottom surface at other opposing surfaces B and B'.

The movable part including the optical system 11 and the bobbin 12 is attached to the magnetic circuit section 2 by an elastic support (not shown) so that the coil section is located within the magnetic gap of the magnetic circuit section 25.
Supported against 5. The magnetic circuit section 25 is arranged between the pole piece 250, a rectangular annular magnet 251 that is magnetized in the thickness direction and placed on the pole piece 250, and the tip of the pole piece 250 that is placed on this magnet. magnetic gap 25
The magnetic gap 25a is configured such that a magnetic field is generated in the optical axis Z direction (inward direction) or in the opposite direction (outward direction).

In such a configuration, the first and second coils 2
1 and 22 in the same direction when viewed from the optical axis Z, the coil parts in the B and B' planes will have the same direction (Z direction) due to the interaction with the magnetic flux that interlinks with these coils. A force acts on the planes A and A′, and forces F ₁ and F ₂ as shown in Figure 5 act on the A and A′ planes, and this force
The component forces _1x and _2x of F ₁ and F ₂ cancel each other out, and B,
Only component forces _1z and _2z in the same direction as the B' plane act. That is, the first and second coils 21,
The optical system 11 can be driven in the focus direction (optical axis Z direction) by flowing currents in the same direction through the optical system 22 .

Next, when currents of the same magnitude are passed through the first and second coils 21 and 22 in opposite directions, the forces acting on each coil in planes B, B' cancel each other out, and
Forces F ₁ and F ₂ as shown in Fig. 6 act on plane A', and components _1z and _2z of these forces F ₁ and F ₂ in the focus direction cancel each other out, and the forces F 1 and F 2 act in the direction perpendicular to the optical axis Z. Only the forces _1x and _2x of X will work. That is,
The X direction corresponds to the tracking direction and the first and second
By passing current in opposite directions through the coils 21 and 22, the optical system 11 can be driven in the tracking direction.

In this way, the first and second coils 21, 22
By appropriately controlling the current supplied to the first and second coils 2, it is possible to drive the optical system 11 in two axes (Z,
Three axes (Z,
It is also possible to drive the

7 is a front view a and a back view b showing a modification of FIG. 4. FIG. In this embodiment, a cup-shaped bobbin 12 is used, and a first coil 21 is wound around the outer periphery of the bobbin so that the coil surface is inclined with respect to the optical axis Z. A second coil 22 is wound around the coil 21 at an angle of approximately 180 degrees with respect to the optical axis Z, and a second coil 22 is wound around the first and second coils 21 and 22 at an angle of approximately 90 degrees with respect to the optical axis Z. The third and fourth coils 23 and 24 are wound. As a result, the line of intersection between the coil surfaces of the first and second coils and the line of intersection between the coil surfaces of the third and fourth coils are substantially perpendicular.

When current is applied to the first and second coils 21 and 22 in directions opposite to each other (clockwise and counterclockwise) when viewed from the optical axis Z, a force acts in the X direction shown in FIG. When current is passed through the first and second coils 21 and 22 in the same direction (clockwise or counterclockwise), a force is applied in a direction parallel to the optical axis Z, as shown in FIG. 8b. Similarly, the third and fourth coils 23,
By controlling the current supplied to the optical axis 24, force is generated in a direction parallel to the optical axis Z and in a Y direction perpendicular to the axes X and Z.

FIG. 9 is a perspective view of another embodiment of the present invention before assembly, and FIG. 10 shows a sectional view a and a plan view b after assembly. 9 and 10, a cup-shaped bobbin 12 is attached to the optical system 11 so that the optical axis Z of the optical system 11 coincides with its central axis. On the outer periphery of this bobbin 12,
First, a coil 13 for driving in the focus direction Z is wound in the circumferential direction. Furthermore, as shown in the figure, for example, four coils 14a~ are wound flat in a rectangular shape.
14d is mounted on the coil 13. These coils 14a to 14d are arranged in a plane orthogonal to the optical axis Z, including axes X in the tracking direction and in the tangential direction, which are orthogonal to each other and include the optical axis Z.
The coils are provided so that the center of the coil is at an angular position of approximately 45° with respect to Y, and the components parallel to the optical axis Z of each coil are close to each other.

The movable part including the optical system 11 and the bobbin 12 is connected to the magnetic circuit section 15 by elastic supports 16a and 16b so that the components parallel to the optical axis Z of the coils 14a to 14d are located within the magnetic gap of the magnetic circuit section 15. It is supported by The magnetic circuit section 15 is magnetized in the thickness direction with the pole piece 150.
An annular magnet 151 placed on 50
and a plate 152 placed on this magnet to form a magnetic gap 15a between it and the tip of the pole piece 150.
5a so that a magnetic field is generated in the radial direction.

In such a configuration, when a current in a predetermined direction is supplied to the focus drive coil 13, the coil 1
3 is acted upon by a force in the optical axis Z direction, that is, in the focus direction, so that the optical system 11 moves in the focus direction in accordance with the direction and magnitude of the coil current. On the other hand, for driving in the tracking direction
d as a pair and the coils 14a,
14b and supplies a current in the opposite direction. Assuming that the current direction of these coils 14a to 14d is as shown in FIG. 11, and the magnetic flux is directed outward, the component parallel to the optical axis Z of each coil is connected to the bobbin 12 as shown by the solid arrow in the figure. A force acts in the tangential direction. Of this force, the components _y in the tangential direction Y cancel each other out, and the resultant force becomes zero. Therefore, the resultant force acting on each coil is the component in the tracking direction
_x only, and the optical system 11 is in the tracking direction
will be moved to. It is easy to understand that by reversing the direction of the current in each coil, the direction of movement of the optical system 11 is reversed. In addition, for driving in the tangential direction Y, the coil 14a
and 14d, 14b and 14c as a pair, and by supplying current in opposite directions between the pairs, the optical system 11 moves in the tangential direction Y based on the same principle as described above.

The method of winding the coils for tracking and driving in the tangential direction is limited to the method of the above embodiment in which the four coils 14a to 14d are each positioned within a range of 90 degrees with respect to the center of the bobbin 12. There is also a method shown below. That is, as shown in FIG. 12a, a pair of coils 17a and 17b are each wound within a range of approximately 180 degrees about the center of the bobbin 12, and another pair of coils 17c and 17d are each wound around the center of the bobbin 12. coil 17
Shift approximately 90 degrees from a and 17b and similarly approximately 180
Wind within the range of ゜. Each pair of coils corresponds to the tracking direction and the tangential direction, and for example, by supplying current in the direction shown in FIG. 12b to the pair of coils 17a and 17b, the optical system 11 can be moved in the tangential direction X. In addition,
Instead of using two coils for driving in one direction, one coil is connected to the bobbin 1 as shown in Figure 13.
12a can also be achieved by directly winding the wire around 2.

Further, as shown in Fig. 14, the coils are shifted in the circumferential direction of the bobbin 12 for each turn, and each coil is wound over 1/4 of the circumference, and each of the four coils is shifted by 90 degrees. Deploy. The relationship between the direction of the coil current and the moving direction of the optical system 11 is based on the operating principle described above. In a similar manner, as shown in FIG. 15, a pair of coils 18a and 18b are
The coils are wound around the shaft over 1/2 of the circumference of the bobbin 12, and another pair of coils 18c and 18c are wound outside of the bobbin 12.
8d can also be wound over 1/2 of the circumference around the Y axis, which is perpendicular to the X axis. In such a configuration,
The optical system 11 can be driven in the X-axis direction by supplying currents in opposite directions to one pair of coils 18a and 18b, and can be driven in the Y-axis direction by supplying currents in opposite directions to another pair of coils 18c and 18d. Can be driven in the axial direction.

Although not shown in FIGS. 12 to 15, a coil for driving the optical system 11 in the focus direction (optical axis direction) may be wound outside or inside the four coils. will be done.

As detailed above, according to the optical system drive device according to the present invention, the movable parts including the optical system are made smaller and lighter because the plurality of coils corresponding to each direction of the drive device are wound around a single bobbin. I can do it. Furthermore, since a magnetic field can be applied to all the coils by a single magnetic circuit section, the thickness of the entire device can be reduced, and the number of parts can be reduced, making it possible to reduce costs and improve reliability. Furthermore, since the movable parts can be driven substantially parallel in each drive direction, the design of the optical system becomes easier. Therefore, such a drive device is most suitable as a compact drive system required when optical pickups become extremely compact.

[Brief explanation of the drawing]

FIG. 1a and FIG. 2a are plan views showing a conventional example;
Each figure b is a sectional view thereof, FIG. 3 is a sectional view showing one embodiment of the present invention, FIG. 4 is a perspective view showing the coil part of FIG. 3, and FIGS. Figures 7a and 7b are front and back views showing a modification of Figure 4, Figure 8 is a diagram to explain the operation of Figure 7, Figure 9 is a diagram of the book. 10A is a sectional view after assembly, FIG. 11 is a plan view thereof, FIG. 11 is a diagram for explaining the operation of FIG. 10, FIG. 15 to 15 are diagrams showing examples of coil winding methods. Explanation of symbols of main parts, 11...Optical system, 12
...Bobbin, 13, 14a-14d, 17a-1
7d, 18a-18d, 21-24...Coil,
15, 25...Magnetic circuit section, 16a, 16b...
Elastic support.

Claims (1)

[Scope of Claims] 1. An optical system driving device for driving an optical system for irradiating a spot light for reading information onto a recording surface of a recording medium, which comprises: a magnetic circuit section having an annular magnetic gap; and the magnetic circuit section. A bobbin is attached to the optical system so as to be located within a gap of a coil section including first and second coils wound vertically around the outer periphery of the bobbin, and the optical system is arranged parallel to the central axis by controlling the current supplied to the coil section. 1. An optical system driving device in a recorded information reading device, characterized in that the optical system driving device is configured to drive in a direction perpendicular to the central axis and a direction perpendicular to the central axis. 2. In the coil portion, both coil surfaces are inclined with respect to the central axis of the bobbin, and the intersection line between the coil surfaces is substantially parallel to the intersection line between the coil surfaces of the first and second coils and the central axis. 2. The optical system drive device in a recorded information reading device according to claim 1, further comprising third and fourth coils wound vertically around the outer periphery of the bobbin.