JPH04245077A - Optical head device - Google Patents

Abstract

PURPOSE:To obtain an optical head device which is small in size and light in weight by providing a center yoke having a relatively small cross-sectional area and by-pass yokes which make magnetic fluxes saturated by the center yoke to make by-pass. CONSTITUTION:A chassis driving device 32 is provided with a center yoke 32a which holds a coil 34a in a slidable state, by-pass yokes arranged on both side faces of the yoke 32a, and external yokes 32b which are arranged so that they can face the yoke 32a and form a magnetic circuit with a magnet 32c. Most of increased magnetic fluxes are utilized for energizing the coil 34a through the center yoke 32a. On the other hand, excessive magnetic fluxes can be supplied to the magnetic circuit without increasing the size of the center yoke 32a, since the fluxes are led to the by-pass yokes 32d. Therefore, the density of the magnetic fluxes acting on the coil 34a can be increased.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to an information storage/reproduction device,
For example, it applies to an optical filing device used as an external storage device for a computer, etc., and is particularly used for irradiating a light beam toward an information recording medium or extracting a light beam from an information recording medium. The present invention relates to an optical head device.

0002

2. Description of the Related Art As shown in FIG. 4, an optical head device 90 that has been used in the past includes a chassis 92 and an optical pickup 80 disposed on the chassis. The optical pickup 80 irradiates a laser beam generated from a light source (not shown), ie, a semiconductor laser, toward an information recording medium, ie, the optical disc 70, or emits the laser beam reflected by the optical disc 70. an objective lens 82 that guides the light to a photodetector (not shown);
in the direction perpendicular to the recording surface of the optical disc 70, that is, in the direction
a direction parallel to the recording surface of the optical disc 70 and orthogonal to the tracks previously formed on the recording surface, that is, a track control direction (X-axis direction);
(This amount of movement corresponds to 1/2 of the amount of surface runout that occurs on the rotating optical disk and to several tracks, approximately 0.5 mm and approximately 0.5 mm, respectively.
It has a lens actuating mechanism 84 and the like that supports the lens (approximately 3 mm).

On the other hand, the chassis 92 includes a chassis drive device 94 for moving the optical pickup 80 in the track control direction, and a moving force generated from the drive device 94 to drive the chassis 92 to move the optical pickup 80 in the track control direction. A drive arm 96 and the like for transmitting information to the shaft 92 are connected. The above chassis 92
is moved in the track control direction, that is, in the X-axis direction, by the drive device 94 and drive arm 96. That is, the chassis driving device 94 includes a yoke 94a and a permanent magnet 9.
4b, and the drive arm 96 has a coil 96a at one end thereof.
The chassis 92 is moved in the X-axis direction depending on the direction of the current supplied to the permanent magnet 64b and the direction of the magnetic field generated from the permanent magnet 64b. The chassis 92 is supported by a guide member (not shown).

[0004] In the optical filing device incorporating the above-mentioned optical head device 90, the optical disc 70 is rotated in the direction of arrow A so that the tracks included in the recording surface of the optical disc 70 have a constant linear velocity. optical disc 70
When information is to be recorded on the optical pickup 80, a laser beam generated from a semiconductor laser (not shown) is intensity-modulated via an electric circuit (not shown) according to the information to be recorded. the optical disc 7 through the objective lens 82;
0 recording surface is irradiated. The recording surface of the optical disk 70 is heated by a laser beam, and information is recorded by changing the reflectance of the surface. When information is reproduced from the optical disc 70, a laser beam having a constant intensity is irradiated onto the recording surface of the optical disc 70 through the objective lens 82 of the optical pickup 80. The laser beam irradiated onto the optical disc 70 is reflected by the optical disc 70, and is intensity-modulated according to the information recorded on the optical disc 70, that is, the change in the reflectance of the recording surface of the optical disc 70, and is returned to the optical pickup. Returned to 80. The reflected laser beam from the optical disc 70 is converted into an electrical signal via a photodetector (not shown), and is reproduced as information recorded on the optical disc 70 by a signal reproducing circuit (not shown).

[0005] In the above-mentioned optical disc device, the moving time, ie, seek time, of the optical head device 90, that is, the optical pickup 80 for recording or reading information on the optical disc 70, is determined by the movement of the optical pickup 80. Regardless of the length of the seek distance, it is determined by the time the optical pickup itself is moved. Nowadays, for example, the chassis is used for reasons such as reducing the seek time and increasing the seek distance as the diameter of the optical disk 70 increases due to an increase in recording capacity. It is desired that the chassis drive speed of the drive device 94 be increased. For this reason, techniques such as increasing the magnetic flux density of the permanent magnet 94b included in the chassis drive device 94 and increasing the output of the coil 96a included in the drive arm 96 are used. has been done.

[0006]

However, unnecessarily increasing the magnetic flux density of the permanent magnet 94b leads to saturation magnetic flux in the magnetic circuit constituted by the permanent magnet 94b and the yoke 94a.
There is a possibility that the size of the magnetic circuit described above may be increased. In this case, since the coil 90a in the drive arm 90 becomes larger and weighs more, there is a problem in that the motion characteristics of the drive device 94, such as acceleration force or braking force, deteriorate. Furthermore, the increase in the saturation magnetic flux has the problem of negating the effects of the various methods used to increase the chassis driving speed.

[0007] An object of the present invention is to provide a chassis drive device incorporated in the above-mentioned optical disk device, which is capable of reducing seek time and is also small and lightweight. be.

[0008]

[Means for Solving the Problems] The present invention has been made based on the above problems, and is a means for optically recording or reproducing information by irradiating a recording medium with a light beam. , means for movably supporting the optical means in a desired direction, and means for moving the supporting means,
an element that generates a driving force for moving the supporting means; a member that is arranged opposite to the driving force generating element and forms a closed circuit on which the driving force acts; and an element that acts on the closed circuit member. When the driving force exceeds a desired magnitude, a member is provided for detouring a part of the driving force and pulling it back to the driving force generating element, and the supporting means is slid in a desired direction. The present invention provides an optical head device including means.

[0009]

[Operation] According to the present invention, the chassis drive device includes a center yoke having a relatively small cross-sectional area, and is arranged in the vicinity of the center yoke, and is saturated with the center yoke. It has a bypass yoke that bypasses the magnetic flux. Therefore, the magnetic flux from the magnet in the chassis drive device is used to energize the coil via the center yoke, while the surplus magnetic flux energizes the bypass yoke. pulled back through. As a result, a chassis drive device is provided that can efficiently utilize the magnetic flux supplied from the magnet without increasing the cross-sectional area of the center yoke.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

According to FIG. 1, the optical head device 2 includes a chassis 4 and an optical pickup 6 disposed on the chassis 4. As shown in FIG. The optical pickup 6 is
Objective lens 10 for focusing a laser beam from a light source (not shown), ie, a semiconductor laser, toward a recording medium, ie, an optical disk 50, which will be described later, and for extracting the laser beam reflected from the optical disk 50. , has a lens holder or lens housing 12 that holds this objective lens 10.

The lens housing 12 is supported movably in the focus control direction of the optical disc 50, that is, the Z-axis direction, and in the track control direction of the optical disc 50, that is, the X-axis direction, through an elastic body, that is, a plurality of wire springs 14. , is connected to the lens support frame 16 (the state of connection is omitted in FIG. 1), and is supported by the lens support frame 16. Further, around the lens housing 12, a pair of focus control coils 18a for moving the objective lens 10 (housing 12) in the Z-axis direction,
A pair of track control coils 20a are arranged to move the objective lens 10 (housing 12) in the X-axis direction. Note that the focus control coil 18a is
It is a hollow coil and is tightly attached to the lens housing 12. Further, the track control coil 20a is
It is a flat coil and is located outside the focus control coil 18a. Further, the wire spring 14 is made of a material that is not affected by magnetic force, such as carbon fiber.

On the other hand, in the lens support frame 16, the focus control coil 18a and the track control coil 20a are mounted at a position where the focus control coil 18a is mounted and a position opposite to the track control coil 20a. Magnet 1 for providing a magnetic field in a desired direction toward
6b, and a yoke 16a which is a part of the lens support frame 16 for holding the magnet 16b.

The semiconductor laser (not shown), objective lens 10, lens housing 12, wire spring 14, lens support frame 16 (yoke 16a, magnet 16b), and focus control and track control coils 18a, 20a are also included.
Each element, ie, the optical pickup 6, is fixed on a chassis 4 having a group of optical elements that guide the laser beam reflected by the optical disk 50 to a photodetector (not shown).

On the other hand, the chassis 4 includes a chassis to be described later.
It has a drive arm 34 and the like to which the drive force generated from the drive device 32 is transmitted. Further, the chassis drive device 32 includes a center yoke 32a, an outer yoke 32b (see FIG. 2), and a magnet 32c, and the chassis drive device 32 includes a center yoke 32a, an outer yoke 32b (see FIG.
A driving force is generated to move the track in the track control direction. Incidentally, a coil 3 is attached to one end of the drive arm 34.
4a, the arm 34 moves the chassis drive device 32 according to the direction of the current supplied to the coil 34a and the direction of the magnetic field generated from the magnet 32c.
along the center yoke 32a. Therefore, the chassis 4 (optical pickup 6) moves in the direction across the tracks of the optical disc 50 (of the optical disc 50).
Moved across the entire track. In addition, the chassis 4
The tracks are slidably arranged via guide rails (not shown) arranged along the direction orthogonal to the recording tracks defined in advance on the recording surface of the optical disc 50, that is, along the X-axis direction. It is moved in the same direction as the control direction, that is, in the X-axis direction.

According to FIG. 2, the chassis drive device 32
These include a center yoke 32a that slidably holds the coil 34a, bypass yokes 32d disposed on both sides of this yoke 32a, and the center yoke 32a.
It has an outer yoke 32b which is disposed opposite to the magnet 32c and forms a magnetic circuit together with the magnet 32c. Conventionally, when this type of drive device, ie, a magnetic circuit, is used, the driving force for energizing the coil 32a is obtained by increasing the cross-sectional area of the center yoke 32a. However, simply increasing the cross-sectional area of the center yoke 32a only increases the saturation magnetic flux in the magnetic circuit as described above, and does not necessarily increase the driving force in the chassis drive device 24. It is known that it is not possible to achieve the purpose of increasing

In contrast, according to the embodiment of the present invention, much of the increased magnetic flux is distributed to the center yoke 32a.
It is used to energize the coil 34a through the coil 34a. On the other hand, as shown in FIG. 3, the surplus magnetic flux is routed through the bypass yoke 32d, without increasing the size of the center yoke 32a. is supplied to the magnetic circuit, and is supplied to the coil 34a.
It becomes possible to improve the magnetic flux density acting on the magnetic flux. In detail, the magnetic flux generated from the north pole of the magnet 32c is guided through the magnetic gap to the center yoke 32a and the bypass yoke 32d, and then returned to the south pole of the magnet 32c via the outer yoke 32b. will be returned to. That is, for example,
By increasing the magnetic flux density generated from the magnet 32c, even if the magnetic flux flowing through the center yoke 32a is saturated, the saturated magnetic flux is reduced to the bypass yoke 32.
Since the magnetic flux is drawn back to the magnet 32c via the magnet 32c, a sufficient amount of magnetic flux necessary to energize the coil 34a is secured. Further, even if, for example, the distance over which the drive coil 34a has to be moved (the stroke to be sought on the optical disk 50) is increased by arranging the bypass yoke 32d, , it has been confirmed that similar effects can be obtained. Therefore, the magnetic flux acting on the coil 34a can be increased while maintaining the cross-sectional area of the center yoke 32a to a minimum. At the same time, although a relatively small chassis drive device 32 is used, the chassis drive speed is increased, that is, high-speed seek (
access) becomes possible. Next, recording of information on the optical disc 50 and reproduction of information from the optical disc 50 will be briefly described using FIG.

In the optical filing device incorporating the above-mentioned optical pickup 6, the optical disc 50 is rotated in the direction of arrow A at a constant linear velocity, for example, so that the tracks included in the recording surface of the optical disc 50 are rotated. When information is recorded on the optical disk 50, a laser beam generated from a light source (not shown), ie, a laser, is intensity-modulated according to the information to be recorded via an electric circuit (not shown), and the light is The optical disc 50 is passed through the objective lens 10 of the pickup 6.
is irradiated onto the recording surface. The recording surface of the optical disc 50 is
Information is recorded by being heated by the beam and changing the reflectance of the surface. When information is reproduced from the optical disc 50, a laser beam having a constant intensity is irradiated onto the recording surface of the optical disc 50 through the objective lens 10. The laser beam irradiated onto the optical disc 50 is reflected by the optical disc 50, and is intensity-modulated according to the information recorded on the optical disc 50, that is, the change in the reflectance of the recording surface of the optical disc 50, and is then regenerated into light. It is returned to the pickup 50. The reflected laser beam from the optical disc 50 is converted into an electrical signal via a photodetector (not shown), and is converted into an electrical signal by a signal reproducing circuit (not shown) to the optical disc 50.
It is played back as the information recorded in the .

Further, when information is recorded on or reproduced from the optical disc 50, the laser beam irradiated onto the recording surface of the optical disc 50 is transmitted through the objective lens 1.
The image must be accurately focused (focused) on the recording surface via zero (focusing operation). On the other hand,
The center of the track on the recording surface, which is rotated at a constant linear velocity and extends radially from the inner circumference to the outer circumference of the optical disk 50, must always be aligned with the position where the laser beam is focused. (tracking operation). Therefore,
The previously described focus control coil 18a and track control coil 20a are used to match the distance between the laser beam and the recording surface of the optical disc 50 and the center of the track. In this case, during tracking, the chassis driving device 32 is energized, and the optical pickup 6 (objective lens 10) is moved to the vicinity of a desired track instructed by a control circuit (not shown) (rough tracking). Ru. After that, the track control coil 2
The above tracking is performed by supplying current to 0a. As a result, the lens housing 12 is moved in the focus control direction and the track control direction, the objective lens 10 and the optical disk 50 are always maintained in the best positional relationship, and information is recorded on the optical disk 50. is,
Alternatively, information is reproduced from the optical disc 50.

[0020]

[Effects of the Invention] As explained above, according to the present invention,
It becomes possible to provide a chassis drive device that can efficiently utilize the magnetic flux supplied from the magnet without increasing the cross-sectional area of the center yoke. This improves the motion characteristics of the drive device, such as acceleration force or braking force, and improves the optical pickup (chassis).
The chassis driving device used for moving the vehicle can be made smaller and lighter in weight. Therefore, the optical pickup used in the optical head device can be moved at high speed,
Access (seek) time in the optical filing device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an optical head device that is an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a structure for moving an optical pickup in the optical head device shown in FIG. 1.

3 is a schematic diagram showing magnetic flux characteristics in the optical pickup moving structure shown in FIG. 2. FIG.

FIG. 4 is a schematic diagram showing a conventionally used optical head device.

[Explanation of symbols]

2... Optical head device, 4... Chassis (support means), 6...
Optical pickup (optical means), 10...Objective lens, 12
... Lens housing, 14... Lens support frame, 16... Wire spring, 18a... Focus control coil, 20a... Track control coil, 20b... Magnet, 32... Chassis drive device (biasing means), 32a... Center York, 32b...
Outer yoke (closed circuit member), 32c...Magnet (driving force generating element), 32d...Bypass yoke (detour member), 3
4... Chassis drive arm, 34a... Chassis drive coil, 50... Optical disk (recording medium).

Claims (1)

[Claims] Claim 1: A means for optically recording or reproducing information by irradiating a recording medium with a light beam; a means for supporting the optical means so as to be movable in a desired direction; A means for moving the supporting means, an element that generates a driving force for moving the supporting means, a member that is arranged opposite to the driving force generating element and forms a closed circuit on which the driving force acts; and a member for detouring a part of the driving force and pulling it back to the driving force generating element when the driving force acting on the closed circuit member exceeds a desired magnitude; and means for sliding the support means in a desired direction.