JPH071551B2 - Optical head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for recording / reproducing or erasing information on / from an information track formed on a recording medium.

2. Description of the Related Art In general, an optical disk drive device has an objective lens driving unit for moving an objective lens in a focus direction and a tracking direction, and an optical unit including the objective lens driving unit, for making a light spot follow an information track. It consists of access means to transfer to a truck. The objective lens drive means and the access means generally have a structure in which a movable coil is arranged in the magnetic flux of a magnetic circuit and a driving thrust is generated by passing an electric current through the movable coil.

On the other hand, in recent years, as performance requirements for optical disk drive devices, it has been desired to make them smaller and thinner and to be able to search at high speed.

For this purpose, conventionally, the optical unit is separated, and only a part of the optical components such as the objective lens driving means and the reflection mirror are mounted on the access means to reduce the weight of the transfer section, and the separation optical system for performing high-speed search. A head has been devised. Moreover,
As disclosed in Japanese Patent Application No. Sho 63-220941, there has been proposed an optical head aiming at further miniaturization and thinning and high-speed retrieval by sharing the magnetic circuit of the objective lens driving means and the access means. An example of this prior art will be described with reference to FIGS.

FIG. 3 is an exploded perspective view, FIG. 4 is a top view, and FIG.
It is a -A 'sectional view.

3 to 5, the X direction is a direction orthogonal to the information track of the recording medium (called a tracking direction), and the Y direction is a direction perpendicular to the recording medium (called a focus direction).

Reference numeral 101 denotes a recording medium, which is an optical disc on which spiral or concentric information tracks are formed. A disk motor 102 is a motor for mounting and rotating the recording medium 101. 1
A fixed optical unit 03 is a fixed optical unit in which a semiconductor laser that serves as a light source, a detector that detects reflected light from the recording medium 101, an optical element such as a prism that collimates a light beam from the semiconductor laser into parallel light, and the like are housed in a fixed member. Yes, it is fixed to the side yoke A116 with screws. Reference numeral 104 denotes an objective lens that focuses the light beam on the recording medium 101. A mover bobbin 105 accommodates the objective lens 104, and is wound with two focus coils 105a for driving the objective lens 104 in the Y direction and two tracking coils 105b for driving the objective lens 104 in the X direction. Ten
Reference numeral 6 denotes a focus leaf spring, which is composed of a spiral focus leaf spring and a dipping rubber that damps resonance of the focus leaf spring, and each is fixedly bonded to the outer peripheral portion of the cylindrical portion of the mover bobbin 105. 107 is a carriage,
The peripheral portions of the two focus leaf springs 106 are bonded and fixed on the surface on the recording medium 101 side in the Y direction and the surface on the opposite side. Reference numeral 108 denotes a bearing A, which has two cylindrical plain bearings formed on both ends thereof and is fixed to the carriage 107 by adhesion. Reference numeral 109 denotes a bearing B, which restricts rotation of the carriage 107, and is fixed to the carriage 107 by adhesion. Reference numeral 110 denotes a reflecting mirror, which is a mirror for reflecting the light beam emitted from the fixed optical unit 103 in the X direction in the Y direction. 111 is an access coil bobbin A, to which the reflection mirror 110 is adhered and fixed,
Access coil 111a for driving the carriage 107 in the X direction
Is wound in a rectangular shape and is fixed to the carriage 107 by adhesion. Reference numeral 112 is an access coil bobbin B, and like the access coil bobbin A111, an access coil 112a is wound in a rectangular shape and adhered to the carriage 107. 113 is a magnet, which constitutes a magnetic circuit together with the back yoke 114, the facing yoke 115, the side yoke A116, and the side yoke B117.
Carriage 1 by electromagnetic force with access coils 111a and 112a
07 is driven in the X direction, and the mover bobbin 105 is driven by the electromagnetic force of the focus coil 105a and the tracking coil 105b.
Are driven in the Y and X directions, respectively. Reference numeral 118 is a guide shaft, and together with bearing A108 and bearing B109, carriage 107
Is slidably supported in the X direction. A guide shaft support spring 119 is screwed and fixed to the side yoke B117 to fix the guide shaft 118 to the side yoke B117.

In addition, the focus coil 105a and the tracking coil 105b
The movable unit moved by the driving force generated in the access coils 111a and 112a is mainly composed of two movable units. The first is movable unit A,
The objective lens 104 is supported by the focus leaf spring 106,
It is a unit integrally configured by a mover bobbin 105, a focus coil 105a, and a tracking coil 105b. The second is the movable unit B, which is the carriage 107 and the bearing A.
108, bearing B109, reflection mirror 110, access coil bobbin
A111, the access coil bobbin B112, and the access coils 111a and 112a are integrally formed, and the vibration characteristic in the Y direction, that is, the focus characteristic is the mass of the movable unit A and the Y of the focus leaf spring 106.
It has a one-degree-of-freedom vibration characteristic determined by the directional rigidity. Also,
The vibration characteristic in the X direction, that is, the tracking characteristic or the access characteristic is a vibration characteristic of a two-degree-of-freedom system having resonance and anti-resonance points determined by the mass of the movable unit A, the rigidity of the focus leaf spring 106 in the X direction, and the movable unit B.

Regarding the optical head of the conventional example configured as described above,
The operation will be described below.

First, when drive power is supplied to the focus coil 105a, the focus coil 105a is moved to Y
Driving force is generated in the direction. At this time, since the spiral portion of the focus leaf spring 106 that supports the movable unit A with respect to the movable unit B is sufficiently soft in the Y direction, the spiral portion of the focus leaf spring 106 is deformed, so that the movable unit A moves in the Y direction. Move. As a result, the objective lens 104 moves in the focus direction and focus control is performed.

On the other hand, when a drive current flows through the tracking coil 105b,
A driving force is generated in the X direction by the electromagnetic action of the tracking coil 105b with the magnetic circuit. At this time, the movable unit A and the movable unit B move integrally until near the anti-resonance frequency, and only the movable unit A moves above the resonance frequency band higher than that, and tracking control is performed.

Further, when a drive current flows through the access coils 111a and 112a, a drive force is generated in the X direction by the electromagnetic action with the magnetic circuit in the access coils 111a and 112a. At this time, contrary to the case of the tracking coil 105b, the movable section unit A and the movable section unit B move integrally until near the anti-resonance frequency, and only the movable section unit B moves above the resonance frequency band higher than that. Access is made.

With such a configuration, it is possible to reduce the weight of the transfer unit and the thickness of the optical head in accordance with the sharing of the magnetic circuit.

However, in the conventional embodiment, since the vibration characteristic in the tracking direction is the two-degree-of-freedom system, the tracking control and the access control are instable as compared with the one-degree-of-freedom system. Was. That is, the focus leaf spring 10
When the rigidity of 6 in the X direction is increased, the movable unit A and the movable unit B move integrally during access,
The movement of the objective lens is small and the access operation is stable, but
During tracking, the movable mass increases and tracking sensitivity decreases, and bearing A108 and bearing B109 and the guide shaft
Tracking control was unstable due to sliding friction with 118. On the other hand, when the rigidity of the focus leaf spring 106 in the X direction is reduced, the tracking control is stable, but the movable unit A sways during access and the access operation becomes unstable, resulting in a long search time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and provides an optical head having a stable tracking control and suitable for high-speed search in an optical head sharing a magnetic circuit for focus, tracking, and access. To aim.

Means for Solving the Problems The technical means of the present invention for solving the above problems include a carriage guided so as to be movable in a direction orthogonal to an information track formed on a recording medium, and a light beam of a light beam on the carriage. A support shaft that is erected parallel to the shaft, a mover bobbin that is rotatable around the support shaft and is slidable in the axial direction of the support shaft, and the rotation of the mover bobbin. The objective lens fixed to the mover bobbin at a position separated from the support shaft so that the objective lens crosses the information track substantially orthogonally by means of the objective lens fixed to the mover bobbin on the recording medium. A focus coil that drives in a vertical direction and a mover bobbin that are arranged at symmetrical positions that are substantially equidistant from the support shaft, each generate a driving force in a direction orthogonal to an information track of the recording medium. Few At least a pair of tracking coils and a magnetic circuit that supplies a magnetic flux to both the focus coil and the tracking coil in common to generate a driving force, and the tracking coil applies an axial moment force to the mover bobbin. The moving element bobbin is rotated to perform the tracking drive, and the tracking coil is used to generate the translational force on the movable element bobbin to perform the access drive to transfer the carriage. It is what

Action The present invention has the above-described structure, and generates a moment about the support shaft during tracking to rotate the mover bobbin around the support shaft to perform tracking operation, and thrusts in the same direction symmetrically about the support shaft during access. Is generated to suppress the rotational movement of the mover bobbin, and the mover bobbin and the carriage can be integrally accessed. Therefore, an optical head having excellent tracking control characteristics and a high-speed access is provided as compared with the related art. It becomes possible.

Example An optical head according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view, and FIG. 2 is a top view. First
In FIG. 2 and FIG. 2, the X direction is a direction (called a tracking direction) orthogonal to the information track of the recording medium, and Y
The direction is perpendicular to the recording medium (called the focus direction)
Is.

Reference numeral 1 is a recording medium, which is an optical disk having spiral or concentric information tracks formed thereon. Reference numeral 2 is a disk smoke, which is a motor for mounting the recording medium 1 and rotating the same. A fixed optical unit 3 includes a semiconductor laser as a light source and a recording medium 1.
A detector for detecting the reflected light from the optical fiber, an optical element such as a prism for collimating the light beam from the semiconductor laser into a parallel light, and the like are housed in a fixing member, which is fixed to the side yoke A16 with screws. Reference numeral 4 denotes a mover bobbin, which engages with a support shaft 10 described later, is rotatable around the support shaft 10, and is a support shaft.
It is slidably supported in 10 axial directions. An objective lens 5 focuses the light beam on the information track of the recording medium, and is held on the mover bobbin 4 apart from the support shaft 10. A focus coil 6 that drives the movable element bobbin 4 in the Y direction and two tracking coils 7a and 7b that drive the movable element bobbin 4 in the X direction or rotate around the support axis 10 are fixed symmetrically about the support axis 10. .

The tracking coils 7a and 7b can switch the polarity of the current flowing through each by a switching means (not shown). The mass distribution of the mover bobbin 4 depends on the spindle 10.
It is configured to be axisymmetric with respect to. Reference numeral 8 denotes an elastic member, one end of which is fixed to the mover bobbin 4 and the other end pole of which is fixed to the support shaft 10. The movement of the mover bobbin 4 in the Y direction and the rotation around the support shaft 10 are restricted, and the objective lens 5 is fixed. Hold in neutral position. 9 is a carriage, and the support shaft 10 is planted,
A reflection mirror 11 for reflecting the light beam emitted from the fixed optical unit 3 in the X direction in the Y direction is fixed. 12
Is a cylindrical plain bearing, which is adhesively fixed to the carriage 9.

Reference numeral 13 denotes a magnet, which constitutes a magnetic circuit together with the back yoke 14, the facing yoke 15, the side yoke 16, and the side yoke B17, and includes the focus coil 6 and the tracking coil 7.
The mover bobbin 4 is rotationally driven in the Y direction, the X direction, or around the support shaft 10 by the electromagnetic force of a and 7b.

A guide shaft 18 is engaged with the slide bearing 12 and supports the carriage 9 slidably in the X direction. Reference numeral 19 is a guide shaft support spring, which is screwed and fixed to the side yoke A16 and side yoke B17, and the guide shaft 18 is fixed to the side yoke A16 and side yoke B.
Fix at 17.

The operation of the optical head of the present embodiment having the above structure will be described below.

First, when a drive current flows through the focus coil 6, a drive force is generated in the Y direction by the electromagnetic action with the magnetic circuit in the focus coil 6. The mover bobbin 4 is slidably supported in the axial direction of the support shaft 10 and is neutrally held by the elastic member 8. Therefore, the mover bobbin 4 moves in the Y direction around the neutral position. Therefore, the objective lens is driven in the focus direction and focus control is performed.

Next, the tracking control operation will be described. The polarities of the currents flowing through the tracking coils 7a and 7b are set to be opposite by switching means. For example, the switching means may be operated in conjunction with the tracking ON signal. When a driving current flows, a driving force is generated in the X direction in the tracking coils 7a and 7b due to the electromagnetic action with the magnetic circuit.
Since the driving directions of the tracking coils 7a and 7b are opposite to each other, the moment force is about the support shaft 10. Since the mover bobbin 4 is rotatably supported around the support shaft 10 and neutrally held by the elastic member 8, the mover bobbin 4 rotates about the neutral position. Therefore, the objective lens 5 held apart from the support shaft 10 is driven in the tracking direction and tracking control is performed. At this time, since the translational force in the X direction is not generated in the mover bobbin 4, the carriage 9 engaged with the mover bobbin 4 via the support shaft 10 is in a stationary state. As described above, since the tracking control is performed only by the rotating operation of the mover bobbin 4, the one-degree-of-freedom secondary vibration characteristic is obtained, and stable control performance can be obtained as compared with the conventional one. In addition, since the movable mass is smaller than the conventional one, the driving current can be small.

Next, the access control operation will be described. The polarities of the currents flowing through the tracking coils 7a and 7b are set to be the same by the switching means, for example, the switching means may be operated in conjunction with the access ON signal. When a driving current flows, a driving force is generated in the X direction by the electromagnetic action of the tracking coils 7a and 7b with the magnetic circuit. However, since the driving directions of the tracking coils 7a and 7b are the same, the mover bobbin 4 is moved. Does not generate a moment force, and becomes a translational driving force in the X direction. Since the carriage 9 is engaged with the mover bobbin 4 via the support shaft 10, the mover bobbin 4 and the carriage 9 move integrally in the X direction, and access control is performed. At this time, since the moment force is not generated in the mover bobbin 4, the mover bobbin 4 does not swing, and stable access control performance can be obtained as compared with the conventional case.

In this embodiment, the tracking drive coil and the access drive coil are shared by the pair of tracking coils 7a and 7b.
Tracking control and access control are performed by switching the current polarities of the racking coils 7a and 7b by switching means, but the current polarities that generate moment force on the mover bobbin are reversed on the mover bobbin instead of the switching means. Similar effects can be obtained by providing a pair of tracking drive coils and a pair of tracking drive coils having the same current polarity for generating a translational force on the mover bobbin.

As described above, according to the present invention, a carriage guided so as to be movable in a direction orthogonal to an information track formed on a recording medium, and the carriage is set up parallel to the optical axis of the light beam. A support shaft, a mover bobbin that is rotatable about the support shaft and is slidably supported in the axial direction of the support shaft, and the objective lens causes the information track to move substantially along the information track by the rotation of the mover bobbin. An objective lens fixed to the mover bobbin at a position spaced apart from a support shaft so as to traverse orthogonally, and a focus coil fixed to the mover bobbin for driving the objective lens in a direction perpendicular to the recording medium. And at least a pair of tracking members, which are arranged on the mover bobbin at symmetrical positions spaced apart from the support shaft at substantially equal intervals and each generate a driving force in a direction orthogonal to the information tracks of the recording medium. A coil and a magnetic circuit that supplies a magnetic flux commonly to both the focus coil and the tracking coil to generate a driving force, and the tracking coil generates an axial moment force on the mover bobbin to perform tracking drive. The tracking coil is configured to generate a translational force on the mover bobbin to perform an access drive for moving the carriage, thereby generating a moment around the support shaft to support the mover bobbin during tracking. Rotate around the axis to perform the tracking operation with the vibration characteristic of the 1-DOF system, and at the time of access, generate thrust in the same direction symmetrically with the support axis to suppress the rotating operation of the mover bobbin and move it. Since the child bobbin and the carriage can be accessed integrally, the tracking control characteristic is superior to the conventional access. Can provide high-speed optical head, the effect is large.

In addition, by making the axial moment forces generated from the tracking coils that are symmetric about the support axis approximately equal, the movement of the mover bobbin and the parasitic resonance due to the imbalance of the axial moment forces during tracking and access can be prevented. Since it can be suppressed, better tracking control characteristics and access characteristics can be obtained, and the effect is great.

Further, by providing the switching means for switching the current polarities of the tracking coils that are separated from each other by the symmetry of the support axis, the tracking operation and the access operation can be performed by the pair of tracking coils.
The weight of the mover bobbin can be reduced, and faster access is possible.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an optical head according to an embodiment of the present invention, FIG. 2 is a top view of the optical head of the present invention, FIG. 3 is an exploded perspective view of a conventional optical head, and FIG. FIG. 5 is a top view of the optical head, and FIG. 5 is a conventional optical head.
It is a -A 'sectional view. 1 ... recording medium, 4 ... mover bobbin, 5 ... objective lens, 6 ... focus coil, 7a, b ... tracking coil, 8 ... elastic member, 9 ... carriage, 10 ... spindle, 11 …… Reflecting mirror, 12 …… Slide bearing, 13,14,15,16,
17 …… Magnetic circuit, 18 …… Guide shaft.

Claims (4)

[Claims] 1. An optical head for reading or writing information by converging a light beam on an information track of a recording medium through an objective lens, the direction being orthogonal to the information track formed on the recording medium. A carriage guided to be transferred to a carriage, a support shaft erected parallel to the optical axis of the light beam on the carriage, rotatable about the support shaft, and slidable in the axial direction of the support shaft. A movable element bobbin pivotally supported on the movable element bobbin, and an objective lens fixed to the movable element bobbin at a position separated from the support axis so that the objective lens crosses the information track substantially orthogonally by the rotation of the movable element bobbin. A focus coil fixed to the mover bobbin for driving the objective lens in a direction perpendicular to the recording medium, and a mover bobbin disposed at symmetrical positions spaced apart from the support shaft by substantially equal intervals. Previous At least a pair of tracking coils that generate a driving force in a direction orthogonal to an information track formed on a recording medium, and a magnetic circuit that supplies a magnetic flux commonly to both the focus coil and the tracking coil to generate a driving force. The tracking coil generates an axial moment force on the mover bobbin to rotate the mover bobbin for tracking drive, and the tracking coil generates a translational force on the mover bobbin. An optical head having a structure capable of performing an access drive for moving the carriage. 2. A shaft moment force generated from a tracking coil located symmetrically with respect to a support shaft at substantially equal intervals is
The optical head according to claim 1, wherein the optical heads are substantially equal to each other. 3. Two pairs of tracking coils are arranged at symmetrical positions spaced apart from each other about a spindle by a pair, and a pair of them generate an axial moment force to perform tracking drive, and the other pair of mover bobbins. 3. The optical head according to claim 1, wherein the optical head is provided with translation to perform access drive. 4. The switching device according to claim 1, further comprising switching means for switching the current polarities of the tracking coils located symmetrically with respect to the support shaft at substantially equal intervals. Optical head.