JPH01192024A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To improve driving efficiency by providing coils for controlling an objective lens at both sides of a permanent magnet, and performing the magnetization of the permanent magnet so that it can function on each coil for controlling the objective lens effectively. CONSTITUTION:The permanent magnet 14 which generates a magnetic field is magnetized in such a way that the outer peripheral part is magnetized in four poles and the inside in two poles of only N-pole. The coils 12a and 12b for controlling a track are provided oppositely to the multi-polar plane of the magnet 14, and the coil 11 for controlling focus oppositely to the plane of the two poles. And when a current corresponding to a magnitude of out of focusing is permitted to flow on the coil 11, it intersects with the magnetic flux of the N-pole of the magnet 14, and the objective lens 1 formed integrally with a movable holder 2 by a generated driving force is moved in a direction of arrow head A, then, focus control is performed. Also, when the current corresponding to off-track is permitted to flow on the coils 12a and 12b, the lens 1 is moved in a direction of arrow head B by the driving force generated between the magnetic field of the magnet 14, then, tracking control is performed. By moving the lens 1 in the above stated way, a focusing position is controlled on the optical information medium of a light spot and the lens 1 can be driven efficiently.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to controlling the track deviation and defocus of a light spot focused on the information recording surface of an optical information recording medium for recording and reproducing information. The present invention relates to an objective lens drive device suitable for use in optical playback devices and recording/playback devices.

[Prior Art] Fig. 7 is an exploded perspective view of a conventional objective lens driving device, Fig. 8 is a plan view of the configuration shown in Figs. FIG. In each figure, (1)
is an objective lens facing an information recording medium (not shown);
) is a movable holder that has a cylindrical bearing part (3) near its center and fixedly holds the objective lens (1) at a position eccentric from the bearing part (3) by a predetermined distance. ,(
5) is a ring part (
4) ring-shaped permanent magnets, (5a), (5b
), (5c), (5d) are the magnetic poles of the permanent magnet (5), and the magnetic poles (5a), (5b) and the magnetic poles (5c), (5d
) have the same circumferential surface and the same polarity. (6) is a base yoke which is a fixed part, and this base yoke (6) has an outer protruding part (7) and an inner protruding part (8) so as to have a predetermined gap between it and the permanent magnet (5). have. The outer protrusion (7) has magnetic poles (5a) of the permanent magnet (5), (
A notch (9a) is provided so as to face the boundary between the magnetic poles (5b) and (5d).
A notch (9b) is provided at a position symmetrical to 9a). (10) is a support shaft (10) that is fixedly erected approximately at the center of the base yoke (6), and the bearing portion (3) of the movable holder (2) is attached to this support shaft (10) by the arrow. It is fitted so as to be slidable in six directions and rotatable in the direction of arrow B. (
11) is a focus control coil fixedly disposed on the outer periphery of the inner protrusion (8) of the base yoke (6), facing the permanent magnet (5).

(12a), (12b) are back yoke (13a), (
13b) is a rectangular back yoke fixedly attached to the support shaft (10) so as to have sides substantially parallel to the axis of the support shaft (10).

The back yokes (13a) and (13b) face the circumferential surface of the permanent magnet (5) almost parallel to each other as shown in FIG. 9, and the track control coils (12a) and (1
2b) is fixedly arranged on the outer periphery of the outer protrusion (7) so that it is housed in the notches (9a) and (9b) with sides substantially parallel to the axis of the support shaft (10). .

The operation of this configuration will now be described with reference to the explanatory diagram of FIG. 1θ. By the way, Fig. 10(a) shows the magnetic poles (5a), (5b), (5c), (5d) of the permanent magnet (5).
), and (b) shows the state of each magnetic pole (5a), (5b), (
5C) and (5d), the magnetic flux density at each position on the outer periphery is shown, respectively.

Since the permanent magnet (5) is magnetized as shown in FIG. 10(b), the magnetic flux density interlinking with the focus control coil (11) arranged on the inner circumferential side of the permanent magnet (5) The polarity of is S
The north pole side has a wider angle than the pole side. For this reason,
The movable holder (2) slides in the direction of arrow A by passing a control current in accordance with the amount of defocus through the focus control coil (11), and the objective lens (2) integrated with the movable holder (2)
1) Focus control can be performed.

In addition, the track control coils (12a) and (12b) are arranged on the outer circumferential side of the permanent magnet (5), and the support shaft (10
) are arranged so that sides substantially parallel to the axis of the magnetic poles (5a) and (5c) and magnetic poles (5b) and (5d) oppose each other. In other words, as can be seen from FIG. 10(b), each support shaft (1) of the track control coils (12a) and (12b)
The track control coil (12a)
, (12b) in accordance with the amount of track deviation, the movable holder (2) rotates, and the objective lens (1) integrated therewith can be track-controlled.

[Problems to be Solved by the Invention] A conventional objective lens drive device is configured as described above, and includes a focus control coil (11) on the inner and outer circumference sides of a multipolar magnetized permanent magnet (5). Track control coil (
12a) and (12b), and control is performed using the magnetic flux density generated on the inner and outer circumferential sides of the permanent magnet (5). In this case, there was a problem in that when the magnetic fluxes of the north and south poles interlinked, the forces generated canceled each other out, resulting in a reduction in the driving force as a whole.

This invention has been made to solve the above-mentioned problems, and provides an objective lens drive device that prevents reduction in driving force due to cancellation of the polarity of magnetic fluxes interlinking each control coil and that is easy to control. With the goal.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an objective lens held by a movable means so as to be able to control the focal position of a light spot with respect to an optical information medium and the track position with respect to an information track; a permanent magnet whose surface is multipolar magnetized and the other surface magnetized unipolar; and a first drive which faces the multipolar surface of the permanent magnet and drives a movable means in a direction to control the track position of the objective lens. The present invention provides an objective lens driving device comprising a coil means and a second drive coil means that faces a unipolar magnetized surface of a permanent magnet and drives the movable means in a focus control direction of the objective lens.

[Function] With the above means, the objective lens driving device of the present invention has the first
, the magnetic flux of the permanent magnet is efficiently applied to each of the second drive coils.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an exploded perspective view of an objective lens driving device according to an embodiment of the present invention. In the figure, (14) indicates the magnetic pole (14a) of the magnetization pattern as shown in the explanatory diagram of FIG. 2(a), (
14b), (14c), and (14d), and has a surface magnetic flux density distribution as shown in FIG. 2(b). That is, this permanent magnet (14) is magnetized so that the outer circumferential side has four poles, and the inner circumferential side has a single pole with only an N pole. Note that the other parts are the same as the configuration shown in FIG. 7.

In the above configuration, the operation thereof will be explained next.

The focus control coil (11) is arranged on the inner circumferential side of the permanent magnet (14), and as can be seen from Fig. 2(b), the focus control coil (11) is mainly N
The magnetic fluxes of the poles are interlinked. For this reason, the focus control coil (1
1), the generated electromagnetic force acts on the movable holder (2) without being canceled out, driving it in the direction indicated by the arrow in FIG. Therefore, the focus control coil (1
The objective lens (1) is integrated with the movable holder (2) by passing a control current in accordance with the amount of defocus through the objective lens (1).
) can be moved in the direction of arrow A to control its focus.

In addition, the track control coils (12a) and (12b) are arranged on the outer circumferential side of the permanent magnet (14), and the support shaft (10)
) are the magnetic poles (14a) and (14c).
and the magnetic poles (14b) and (14d), so as can be seen from FIG. 2(b), each of the spindles (10 ) The polarity of interlinking magnetic flux is different between one side parallel to the axis and the other side. Therefore, by passing current through the track control coils (12a) and (12b), the directions of the forces generated on the sides substantially parallel to the axis of the support shaft (10) become the same direction of rotation, so that the movable holder ( 2) as the first
A force acts on the movable holder (2) so that it rotates in the direction of arrow B in the figure, and a control current is passed through the track control coils (12a) and (12b) in accordance with the amount of track deviation.
Track control of the objective lens (1), which has become a body, can be performed.

3 is a plan view of an objective lens driving device according to another embodiment of the present invention, FIG. 4 is a sectional view taken along line I-1 in FIG. 3, and FIG. 6 is a plan view showing the configuration of the fixed portion of the configuration shown in FIG. 3. FIG.

In each figure, (15) is a ring-shaped focus control coil holding part provided at the lower part of the movable holder (2) to fixedly hold the ring-shaped focus control coil (11);
16a) and (16b) are track control coils (12a)
), (12b) in a movable holder (2
) Track control coil holding part provided on the side of (
17) are magnetized and have magnetic poles (14a), (14b), (14
c), (14d) is a mounting made of non-magnetic material fixing a permanent magnet (14) on its upper surface. (18) is an objective lens (
This is a counterweight installed at a position symmetrical to 1). The notch (9a) provided in the outer protrusion (7) of the base yoke (6) is located at the magnetic pole (1) of the permanent magnet (14).
The notch (9b) is provided so as to face the boundary between magnetic poles 4a) and (14b), and the notch (9b) is provided so that the boundary between magnetic poles (14b) and (14c) faces. These notches (9a), (9b)
There are track control coils (12a) and (12b) inside.
the support shaft (10) so as to face the permanent magnet (14);
It is arranged so that it has sides almost parallel to the axis of
The notches (9a) and (9b) are provided so that the movable holder (2) can rotate by a desired angle in the direction of arrow B in FIG. Permanent magnet (14) and track control coil (12a)
), (12b) are track control coils (12a), (
12b) are arranged in such a positional relationship that the polarities of interlinking magnetic fluxes are different between one side substantially parallel to the axis of the support shaft (10) and the other side.

The operation of this configuration will now be described. The focus control coil (11) is arranged on the inner circumferential surface of the permanent magnet (14), and the magnetic flux of the north pole mainly interlinks with each other, so this occurs when current is passed through the focus control coil (11). The focus control coil (11) acts to drive the movable holder (2) in the direction of arrow A in FIG.
The objective lens (1) is integrated into the movable holder (2) by applying a control current according to the amount of defocus to
Focus control can be performed. Further, the track control coils (12a) and (12b) are arranged on the outer circumferential side of the permanent magnet (14), and are interlinked at the - side and the other side, which are approximately parallel to the axis of each support shaft (10). Since the polarity of the magnetic flux is different, by passing current through the track control coils (12a) and (12b), the direction of the force generated on the side almost parallel to the support shaft (10) becomes the same direction of rotation, so that the movable Holder (2
) in the direction of arrow B in Fig. 3 acts on the movable holder (2
) can perform track control of the objective lens (1) integrated with the lens (1).

[Effects of the Invention] As described above, according to the present invention, the coils for controlling the objective lens are disposed on both sides of the permanent magnet, and the magnetic flux generated on both sides of the permanent magnet is used to drive the objective lens. Since the permanent magnets are magnetized and arranged so that the magnetic force of the magnets effectively acts on the drive of each control coil, an objective lens drive device with high drive efficiency can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of magnetization of a permanent magnet configured as shown in FIG. 1, and FIG. 3 is another embodiment of the present invention. A plan view of the objective lens driving device according to the example, FIG. 4 is a sectional view taken along line 1-I in FIG. 3, FIG. 5 is a sectional view taken along line
The figure is a plan view showing the structure of the fixed part of the structure shown in Fig. 7.
The figure is an exploded perspective view of a conventional objective lens drive device, FIG. 8 is a plan view of the configuration shown in FIG. 7, FIG. 9 is a sectional view taken from the line ■-■ in FIG. It is an explanatory view of magnetization of the permanent magnet of the structure of a figure. In the figure, (1) is an objective lens, (2) is a movable holder, (11) is a focus control coil, (12a), (12b)
) is a track control coil, (14) is a permanent magnet, (1
4a), (14b), (14c), and (14d) are magnetic poles. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Patent attorney Masuo Oiwa (and 2 others) @Figure 1 Figure 2 (b) Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 (b) Procedural amendment < m*) '5th - Showa 6+ September 28th

Claims (1)

[Claims] (1) An objective lens held by a movable means capable of controlling the focal position of the light spot with respect to the optical information medium and the track position with respect to the information track, and one surface of which is magnetized with multipole and the other surface with unipolar magnetization. a magnetized permanent magnet; a first drive coil means that faces the multipolar surface of the permanent magnet and drives the movable means in a direction for controlling the track position of the objective lens; An objective lens driving device comprising a second drive coil means for driving the movable means in a focus control direction of the objective lens.