JPH0253231A - Optical driving device - Google Patents

Abstract

PURPOSE:To improve driving efficiency by providing a yoke even for the side of a magnet, arranging a side, which is not positioned in the magnetic gap of a tracking coil, at a position opposite to the yoke, and operating opposite directional magnetic flux. CONSTITUTION:A magnet 7a is fixed to outer yokes 8a, 8e, and 8f so that its magnetizing direction can be vertical for its adhered surface, and an inner yoke 8b is provided on a position opposite to the magnet 7a. The respective focusing directional ((z) directional) one sides of tracking coils 4a and 4b formed into approximately flat quadrangles are positioned in the clearance between the magnet 7a and the inner yoke 8b, and the outside sides of the coils 4a and 4b corresponding to the above-mentioned sides are positioned under an opposite state to the outer yokes 8e and 8f. Consequently, when a current is applied to the tracking coils 4a and 4b, the direction of electromagnetic force to generate in the two sides parallel to a (z) direction becomes the same direction as a tracking direction. Thus, the utilization factor of a driving coil can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording and reproducing method that optically records and reproduces information by projecting a light spot onto a recording medium such as a disk through an objective lens. The present invention relates to an optical system driving device of an apparatus.

[Conventional technology]

Generally, in order to accurately record and reproduce information using an optical information recording/reproducing device, it is necessary to control a driving device so that a light spot properly follows an information track. For this purpose, the objective lens is provided via a holding member so as to be movable in a focusing direction parallel to its tip axis and in a tracking direction perpendicular thereto, and is displaced by electromagnetic driving means.

An optical system drive device equipped with such a focusing control mechanism and a tracking control mechanism includes, for example, Japanese Patent Laid-Open No. 59
There is a device shown in FIG. 5, which is disclosed in Japanese Patent No. 221839. This is because the objective lens l is fixed to a movable member 2, and a focusing coil 3 is attached to the movable member 2.
is wound, and tracking coils 4a to 4d are further provided.

The movable member 2 is connected to a fixed member 6 by four elastic support members 5.
By being supported against, it is movable in the focuser direction and the tracking direction.

On the other hand, Magnen) 7a and 7b are bases 8 made of high magnetic permeability material.
They are fixed with the same polarity facing each other to form a magnetic circuit. This magnetic circuit and tracking coils 4a, 4d
FIG. 6 shows the relationship between (or 4b, 4c) and the direction of magnetic flux. According to this, about half of the tracking coils 4a+4d are located in the magnetic gap,
The other half is positioned outside the magnetic gap. a tracking coil 4a located within the magnetic gap;
Sides 4a-1 and 4 extending in the focusing direction of 4d
When a current in the same direction is passed through d-1, a force is generated by the T4N action, and the movable member moves in the tracking direction.

However, in the above configuration, only one of the four sides of the tracking coil is involved in tracking drive.
Coil utilization is extremely low.

In order to increase the coil utilization rate, Japanese Patent Application Laid-Open No. 62-140252
There is a device shown in FIG. 7, as disclosed in the above publication.

This is done by fixing magnets 7a magnetized with multiple poles in opposite directions, or two magnets 7a with opposite magnetization directions, to the yoke 8a, and focusing the tracking coil 4a at a position where the different poles of the magnets 7a face each other. This is an arrangement of sides extending in the direction.

[Problem to be solved by the invention]

However, the former of the conventional techniques has a problem in that the coil utilization rate is low because the driving force is generated only on one side of the tracking coil as described above. In addition, in this case, a component of magnetic flux in the same direction as inside the magnetic gap also exists in the portion of the tracking coil located outside the magnetic gap, and a force in the opposite direction to the desired driving direction is generated, driving the entire driving member. The problem is that the power decreases.

On the other hand, the latter of the above-mentioned conventional techniques has problems in that the magnet is magnetized with multiple poles, which increases the cost and deteriorates the magnet performance. Additionally, there is a problem in that the number of steps required for bonding increases because the two magnets are bonded together. Furthermore, there is a problem in that a magnetic circuit for driving in the focusing direction must be provided separately, resulting in an increase in cost.

The present invention is proposed to solve the above problems,
The object of the present invention is to provide an optical system drive device that has a simple configuration, allows the magnetic flux of a magnet to effectively act on a drive coil, and improves drive efficiency.

[Means and effects for solving the problem] In order to achieve the above-mentioned object, the present invention provides a holding member for holding an optical system by electromagnetic action between a coil provided on the holding member and a magnet placed opposite to the coil. In the optical system driving device configured to drive in a desired direction, the magnet is magnetized in a direction perpendicular to the driving direction of the holding member, a yoke is provided at least on the back and sides of the magnet, and the coil is magnetized in a direction perpendicular to the driving direction of the holding member. The coil has a substantially annular shape that is flat in the driving direction, with a part of the coil located within the magnetic gap, and the other part facing the side yoke of the magnet.

In this way, a yoke is also provided on the side of the magnet, and the side that is not located within the magnetic gap of the tracking coil is placed opposite the yoke to apply magnetic flux in the opposite direction to generate a driving force in the tracking direction. This allows the driving member to efficiently generate a driving force in the same direction.

〔Example〕

Fig. 1 shows a first embodiment of the present invention, in which Fig. 1A is a perspective view showing the positional relationship of the magnet, yoke, and trunking coil, and Fig. 1B is a plan view. be. The magnet 7a is fixed to outer yokes 8a, 8e, and 8f formed in a U-shape using a high magnetic permeability material so that the direction of magnetization is perpendicular to the adhesive surface. and magnet 7
An inner yoke 8b is provided at a position facing a, forming a magnetic circuit.

One side extending in the focusing direction (Z direction) of the tracking coils 4a and 4d, which are formed in a substantially flat rectangular ring shape, is located in the gap between the magnet 7a and the inner yoke 8b, that is, within the magnetic gap, and the outer side corresponding to this side is positioned. It is positioned so as to face the outer yokes 8e and 8f.

The magnetic flux in the magnetic circuit formed in this way flows between the magnet 7a and the inner yoke 8b near the center of the magnet 7a, as shown by the arrow in FIG. , 8
flows between f. The y-direction components of the magnetic flux acting on each of the two sides of the tracking coils 4a, 4d extending parallel to the Z-direction are in opposite directions. Therefore, when current is passed through the tracking coils 4a and 4d, the force generated by electromagnetic action on the two sides of each coil extending parallel to the two directions is because the y-direction component of the magnetic flux is opposite, and the direction of the current flowing is opposite. The tracking direction is the same, and the driving force is 2
The size is the sum of the forces generated on the sides, and high drive sensitivity can be obtained.

FIG. 2 shows a modification of the first embodiment, in which the outer yoke 8e,
A portion corresponding to 8f is formed into an arm shape extending from the outer yoke 8a. Other configurations and effects are the same as in the first embodiment.

FIG. 3 shows a third embodiment of the invention. Magnen) 7a
The back surface of the yoke 8a is fixed to an outer yoke 8a made of a material with high magnetic permeability so that the direction of the yoke is perpendicular to the adhesive surface. outer yoke 8
Unlike the first embodiment, the outer yokes 8e and 8f are not U-shaped, but are provided on the sides of the magnet 7a in the tracking direction (X direction). magnet 7a
As in the first embodiment, an inner yoke 8b is provided at a position facing the inner yoke 8b to form a magnetic circuit. A tracking coil 4a formed in a substantially flat rectangular ring shape within the gap between the magnet 7a and the inner yoke 8b, that is, the magnetic gap;
4d extending in the focusing direction (two directions), and the outer side corresponding to this side is the outer yoke 8e.
It is positioned opposite to t8f. The flow of magnetic flux is as shown by the arrow in FIG. 3B, and is the same as in the first embodiment, and the effect on the driving force is also the same.

In the above embodiments, since the tracking coil is not bent, the number of bending steps is not required, and there is no disconnection or short circuit of the coil, and costs can be reduced.

FIG. 4 shows a fourth embodiment of the present invention, in which outer yokes 8e and 8f, which are continuous with the outer yoke 8a to which the magnet 7a is fixed, are different from those in the first embodiment. The difference is that it is set back inward from the surface on the magnetic gap side, thereby concentrating the magnetic flux flowing to the side of the magnet 7a on the outer yokes 8e and 8f.

The L-racking coils 4a and 4d are bent into an L-shape, and one side of the two sides extending parallel to the focusing direction is located within the magnetic gap between the magnet 7a and the inner yoke 8b, and the corresponding The other outer sides are positioned opposite to the outer yokes 8e and 8f, respectively.

The flow of magnetic flux in the magnetic circuit formed in this way is as shown by the arrows in Figure 4B, and magnetic flux in opposite directions acts on each of the two sides of the tracking coil, and when a current is passed through the coil, it is caused by electromagnetic action. The forces generated are in the same direction in the tracking direction. Therefore, as in the first embodiment, the driving force is the sum of the forces generated on the two sides, and high driving sensitivity can be obtained. In the case of this embodiment, the tracking coil is purposely bent, but as a result, compared to the first to third embodiments, the magnetic flux acting on the sides of the tracking coil extending parallel to two directions is The Y-direction component of is increased, and higher drive sensitivity can be obtained.

Note that in the present invention, the objective lens is supported by an elastic support member, and two
In addition to the 4-wire method that allows for directional driving, other methods such as a rotation method can also be applied.

Instead of the objective lens, other optical members such as a collimator lens or a mirror may be driven.

Furthermore, it may be applied to driving in the focusing direction or tangential direction. The magnetic circuit may be an open magnetic circuit without an inner yoke, the shapes of the magnet and the tracking coil are not limited, and the number of tracking coils is not limited to four, but may be two.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve the utilization efficiency of the drive coil without using a specially configured magnet, and to obtain the same drive sensitivity as the conventional one, a low grade magnet with a low magnetic flux density is used. However, it is sufficient, and the volume of the magnet is also small, so costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view and a plan view showing a first embodiment of the present invention, Fig. 2 is a perspective view and a plan view showing a second embodiment, and Fig. 3 is a perspective view showing a third embodiment. 4 is a perspective view and a plan view showing the fourth embodiment, FIG. 5 is a perspective view showing a conventional example, and FIGS. 6 and 7 are explanatory diagrams of a magnetic circuit according to a conventional example. It is. 4a...Tracking coil 7a...Magnet 8a...Outer cork 8
b... Inner yoke prayer Figure 2 Figure 6 Figure 7 Continuation of the dispute in the official book November 26, 1988 1, page 6 line 15 of the specification, page 8 lines 6 to 7 "
2. Correct “Fig. 1 (b)” on page 6, line 20 of the same page to “Fig. 1 B”.
” is corrected. 1. Indication of the case 1986 Patent I No. 202728 2. Name of the invention Optical system drive device 3. Relationship with the case Patent applicant Olympus Optical Industry Co., Ltd. 4. 6. Subject of the amendment

Claims (1)

[Claims] 1. An optical system drive device that drives a holding member that holds an optical system in a desired direction by electromagnetic action between a coil provided on the holding member and a magnet placed opposite the coil. The magnet is magnetized in a direction perpendicular to the desired driving direction of the holding member, a yoke is provided on the back and side surfaces of the magnet opposite to the coil side, and the coil is arranged in a substantially annular shape that is flat in the driving direction. An optical system driving device characterized in that a part of the coil is located within a magnetic gap and the other part is opposed to a side yoke of a magnet.