JPS6369028A - Objective lens driving device for optical head - Google Patents

Abstract

PURPOSE:To simplify a structure and to contrive the miniaturization of a device by arranging a focus driving coil, a tracking drive coil and a speed feedback coil so that they can cross a magnetic field that they share in common. CONSTITUTION:A coil fitting member 19 with a U-shaped section is fitted to a part which is the side part of an objective lens barrel and confronted with a yoke 9 with an E-shaped section. Flat coils 13a, 13c, 14a and 14c stuck to the two tooth-like parts of the coil fitting member 19, and flat coils 13b, 13d, 14b and 14d are positioned in gaps 20a and 20b, respectively, in a magnetic circuit formed with the yoke with the E-shaped section 9 and magnets 10a and 10b. By controlling the sizes and directions of currents that are allowed to flow in a group of the flat coils 13a and 14a, and a group of the flat coils 13b and 14b, two types of driving forces in directions alpha and beta apply to the former and latter groups, respectively. Consequently an objective lens integrally formed with them is driven in the focusing and tracking directions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device for an optical head, and more specifically, for driving an objective lens of an optical head in a focusing direction and a tracking direction by following the displacement of a disk. Regarding equipment.

A conventional objective lens driving device for an optical head is used, for example, in a magneto-optical disk device as shown in FIG.

That is, the information recorded on the magneto-optical disk D is read by the optical hand H, but the disk D is displaced in the α direction in FIG. Since it is displaced in the β direction in Figure 6,
In order to follow the resulting displacement of the information track, the objective lens L is driven by an objective lens driving device A.

Here, driving the objective lens L to follow the displacement in the α direction is called driving in the focus direction. Also, β
Driving the objective lens L following the displacement in the direction is called driving in the tracking direction.

An example of a conventionally known objective lens drive device is shown in FIGS. 7 to 9.

In this objective lens driving device 51, the objective lens L
is held by the objective lens barrel 52, and the objective lens barrel 52 is bent in the β direction by a leaf spring 53m,
53y, it is supported by the intermediate support body 54. The intermediate support 54 includes slit disk-shaped springs 55m and 55I that can be bent in the α direction.

is supported by a fixed support body 56.

A cylindrical yoke 57, a yoke plate 57', and a ring-shaped magnet 58 are attached to the bottom of the fixed support 56, and a frame-shaped yoke 59a, which faces in the direction of the β arrow, is attached to the body. 59b are respectively attached, and the frame-shaped yokes 59, . In the center of 59& there is a block magnet 601 and a cork plate 59. ', Diblock Magnet 601. and yoke plate 59+,
' are attached to each.

On the other hand, a cylindrical coil 61 is attached to the bottom of the intermediate support 54, and the cylindrical coil 61 is connected to the air gap of the magnetic circuit formed by the cylindrical yoke 57, the yoke plate 57', and the ring-shaped magnet 58. 62.

Further, on the side of the objective lens barrel 52 facing the frame-shaped yokes 59m and 59I, a frame-shaped coil 631.
63i, are attached respectively, and those frame-shaped coils 6
3. ．． 63& is a gap 64. of the magnetic circuit formed by the frame-shaped yoke 59°, the yoke plate 59□', and the block-shaped magnet soa. .

The frame type yoke 591. and a block-shaped magnet 60, respectively, are inserted into the holes R64b of the magnetic circuit.

The 8th vIJ shows the cylindrical yoke 57, yoke plate 57', ring magnet 58, and cylindrical coil 61 taken out.

In addition, the frame type yoke 59b and the yoke plate 59i,
' and frame-shaped coil 631. FIG. 9 shows an extracted version of this.

In such an objective lens driving device 51, when a current is passed in one direction through the cylindrical coil 61, the ring-shaped magnet 58
An electromagnetic force acts between the cylindrical coil 61 and the magnetic field, and the cylindrical coil 61 receives a force in the direction of being drawn into the air gap 62, and when the current is reversed, it receives a force in the direction of pushing it out of the air gap 62. In other words, it receives a force in the α direction. The magnitude of that force is
Proportional to the magnitude of the current.

Since the cylindrical coil 61 is attached to the intermediate support 54, the intermediate support 54 receives a force in the α direction.

Therefore, by adjusting the current flowing through the cylindrical coil 61, the objective lens L can be driven in the α direction, that is, the focus direction.

The same applies to the frame coils 63m and 63h, and by adjusting the current flowing through these frame coils 63m and 634, the objective lens barrel 52 receives a force in the β direction, so that the objective lens L is moved in the β direction, that is, tracking. It can be driven in the direction.

By the way, when performing position control as described above, the displacement speed is fed back. If so-called speed feedback is performed, the rigidity of the servo system against disturbance vibrations can be increased, so it has been proposed to provide a speed sensor in the objective lens driving device in order to perform this speed feedback.

Such a speed sensor may be one in which coils are placed in a magnetic field and an electromotive force induced therein is detected in proportion to their relative speed.

Problems with the Prior Art In conventional objective lens drive devices, the coil and magnetic circuit for driving in the focusing direction and the coil and magnetic circuit for driving in the tracking direction are provided independently, so the structure There is a problem that it is complicated and large.

Further, if a coil is provided to detect and return the speed, there is a problem that the structure becomes even more complicated and large.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an objective lens driving device that has a simple and compact structure by sharing a magnetic circuit.

Structure of the Invention An objective lens driving device for an optical head according to the present invention is an objective lens driving device for driving an objective lens of an optical head in a focusing direction and a tracking direction in order to follow the displacement of a disk. The configuration is characterized in that the driving coil and the velocity feedback coil are both arranged so as to cross a common magnetic field.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on examples shown in the drawings. Here, Figure 1 is a schematic cross-sectional view of an objective lens driving device of an optical head according to an embodiment of the present invention, Figure 2 is a cross-sectional view taken along line xx' in Figure 1, and Figure 3 is a flat plate coil and magnetic circuit. FIG. 4 is a diagram illustrating the principle of driving by electromagnetic force, and FIG. 5 is a diagram illustrating the principle of speed detection by induced electromotive force. Note that the present invention is not limited to the embodiments shown in the figures.

In the objective lens drive device 1 for the optical head shown in FIG. 1, the objective lens L is supported by an objective lens mirror W12.

The objective lens &11 cylinder 2 is supported by an intermediate support 4 by plate springs 3a, 3& that can swing in the β direction. Inside the leaf springs 3□, 35, there is a rubber-like elastic body 23. for absorbing vibrations of the springs. ．． 23I, are attached to each. An annular counterbalance weight 24 is attached to the bottom of the barrel 2 of the objective lens 11.

The intermediate support 4 is supported on the fixed support 6 by a slit disk spring 51.5i which can swing in the α direction. On one side of the springs sa and sh, there is a rubber-like elastic body 25 for absorbing the vibration of the spring. .

25I is attached.

Yokes 7 and 9 each having an E-shaped cross section are attached to portions of the body of the fixed support 6 that face each other in the β direction. As shown in FIGS. 2 and 3, the toothed portion of the E-shaped yoke 7 has a magnet 8. and 8I, are attached to the cross-section E-shaped yoke 9
A 10□5 lO magnet is attached to the tooth-like part.

On the other hand, coil attachment members 17 and 19 each having a U-shaped cross section are attached to a side portion of the objective lens barrel 2, which faces the E-shaped cross-section yoke 7.9.

One of the two toothed portions of the coil mounting member 17 has a flat plate coil 11. , Ile are attached respectively. Also,
A flat coil 12c is placed on top of the flat coil 111.11c.
are pasted in layers, and then a flat coil 12 is layered on top of that.
．． is pasted.

Similarly, the other toothed portion has a flat plate coil 115.11.
J is pasted, a flat plate coil 12J is laminated and pasted thereon, and a flat plate coil 125 is laminated on top of that.

Then, the flat plate coil 11. ．． 11c, 12. .

12c is a gap 18. of the magnetic circuit formed by the E-shaped cross-sectional yoke 7 and the magnet 8□. located within. In addition, flat coils 11+, lla, 12h, 12
a is located within a gap 18s of a magnetic circuit formed by the yoke 7 and the magnet 8.

Similarly, the flat plate coils 13. ．． 13c, 14&, 14c and 13b, 13a, 14I, 14a are attached, and the E-shaped cross section yoke 9 and magnet 10□
, 101. and 20I, respectively, of the magnetic circuit formed by the magnetic circuits 20 and 20I.

FIG. 3 shows the coil mounting member 19 and the flat coil 131 attached thereto, and the other coil mounting member 17 is also similar although not shown.

Flat coil 13. and 14. and air gap 20. The relationship between the magnetic field B and the magnetic field B is shown in FIG.

That is, the conductors of the flat plate coils 138 and 14□ are formed in a rectangular spiral shape, and only the portion corresponding to the sewage slow part of the square spiral of the flat plate coil 13° is included in the magnetic field B, and the flat plate coil 14. The position is determined so that only the conductor of one of the two vertical side portions of the rectangular spiral is included in the magnetic field B.

Here, the direction of the magnetic field B is perpendicular to the paper surface of FIG. 4 and penetrates from the back to the front, and the current
, when the direction is from right to left in the figure, an electromagnetic force is generated upward in the figure as indicated by arrow F1. Further, if the current 16 flowing through the flat plate coil 141 is directed from the top to the bottom of the figure, an electromagnetic force is generated in the left direction of the figure as indicated by arrow F8.

The magnitude of the electromagnetic forces F, , Fβ can be adjusted by the magnitude of the current IH+Is, and when the current direction is reversed, the direction of the force is reversed.

The directions of these electromagnetic forces F, Fβ are α direction,
Since they match in the β direction, flat coils 13m and 141
1 receives driving forces in the α and β directions, and therefore, the objective lens L, which is integrated with these flat plate coils 13□ and 141, also receives driving forces in the α and β directions.

Similarly, the driving force in the α direction can be obtained by the flat plate coils 11m, 1 lb, 13I, and the flat plate coils 12. , 121. , 14 & can obtain the driving force in the β direction.

Therefore, as a result, the objective lens L can be driven in the α direction, that is, the focus direction, and can also be driven in the β direction, that is, the tracking direction.

Next, as shown in FIG. 5, the flat coil 13°
Flat coil 13 in the figure. There is a conductor in the magnetic field B that is located symmetrically to the bottom and corresponds to the water supply area of the rectangular spiral. Therefore, electromotive force E proportional to the displacement speed in the α direction is generated in the flat plate coil 13c by electromagnetic induction, so that the speed in the α direction can be detected.

Further, in the flat plate coil 14C, the conductor of one vertical side of the rectangular spiral is in the magnetic field B, similar to the flat plate coil 14°. Therefore, the electromotive force E8 according to the displacement speed in the β direction
can be used to detect velocity in the β direction.

Similarly, the flat plate coils 11c, 11a, and 13a can be used for speed detection in the α direction, and the flat plate coils 12
e, 12a, and 14- can be used for velocity detection in the β direction.

The speed detected in this manner is fed back to the currents Im and Ig, which is speed feedback to the driving force, and thereby the rigidity of the servo system against external vibrations can be increased.

The flat plate coil 111 and the like can be easily manufactured by using a printed circuit. Furthermore, if a flexible printed circuit is used, the thickness can be reduced, so the air gap can be small, and therefore the magnetic circuit can be made smaller, and the overall size can be made smaller.

Although the flat plate coil 11c and the like have been described as being used for speed detection, they can also be used as drive coils. It is used for speed detection only during access, and can be used for driving at other times by switching.

As another embodiment, flat coils 11c, 11 for detecting speed in the focus direction as in the above-mentioned embodiment 1 may be used.
J, 13c, 13a, and flat plate coils 12C, 12a + 1 for detecting speed in the tracking direction.
4c, 14.1, it may include only either the former or the latter.

Effects of the Invention According to the present invention, in an objective lens drive device that drives an objective lens of an optical head in a focusing direction and a trunking direction in order to follow the displacement of a disk, a focus drive coil, a tracking drive coil, An objective lens driving device for an optical head is provided, characterized in that a velocity feedback coil and a velocity feedback coil are arranged so that both of them intersect with a common magnetic field, and thereby the driving force in the focusing direction and the driving force in the tracking direction are Since one magnetic circuit can coexist and generate speed, and the same magnetic circuit can be shared for speed detection, the device configuration is simplified compared to the conventional case where separate magnetic circuits are used. I can,
Further, it can be configured to be small and lightweight.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an objective lens driving device of an optical head according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line xx' in FIG.
A sectional view, FIG. 3 is a perspective view showing the flat plate coil and magnetic circuit, and FIG. 4 is a diagram explaining the principle of driving by electromagnetic force.
Figure 5 is a diagram explaining the principle of speed detection using induced electromotive force, Figure 6
The figure is a conceptual diagram showing the general configuration of a magneto-optical disk device, FIG. 7 is a sectional view of an example of a conventional objective lens drive device for an optical head, and FIG. 8 is a conventional cylindrical coil and magnetism for driving in the focus direction. FIG. 9 is a perspective view showing a conventional frame-shaped coil and magnetic circuit for driving in the tracking direction. (Explanation of symbols) 1... Objective lens driving device of optical head 2... Objective lens barrel, 3 &... Leaf spring 4... Intermediate supports sa, sb... Slit disk shape Spring 6...Fixed support 7.9...E-shaped cross section yoke 8m, al, 10m, 10h...Magnet 1
1a, 111. , 13□, 13b...Flat coil 12 for driving in the focus direction, 12b,
14m, 14+. ...Flat coil 11c, I for driving in the tracking direction
L+, 13c, 13a...Flat coil 12c for speed detection in the focus direction
, 12a, 14c, 14a...Flat coils 18a, 118I, , 20 for detecting speed in the tracking direction
m, 20b...Gap B...Magnetic field F, ,F,...Electromagnetic force ra, 16...Current flowing through the coil α...Focus direction β...Tracking direction D...Optical magnetism Disk L...Objective lens A...Objective lens drive device H...Optical head.

Claims (1)

[Claims] 1. An objective lens drive device that drives an objective lens of an optical head in a focusing direction and a tracking direction in order to follow the displacement of a disk, which includes a focus drive coil, a tracking drive coil, and a velocity feedback coil. 1. An objective lens driving device for an optical head, characterized in that a magnetic field is arranged so that both coils intersect with a common magnetic field.