JPH0773488A - Device for driving lens - Google Patents

Abstract

PURPOSE:To provide an optical head easy for constituting and assembling and capable of precise focusing driving. CONSTITUTION:A window is formed in a prescribed part of a holder 2, and a movable body and a base are constituted of an integrally forming member capable of displacing only in the direction nearly perpendicular to the direction Y. Then, this device is constituted so that a centroid position of a connection body of a lens 1, a focusing coil 3 and a tracking coil 4 coincides nearly with the center of driving force generated in the focusing coil 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device used for reproducing information recorded on, for example, an optical recording disc or for recording information on such a disc.

[0002]

2. Description of the Related Art Conventionally, a means for supporting an objective lens for irradiating a light spot on a recording medium so as to be displaceable in a focusing direction parallel to an optical axis of the recording medium and a tracking direction orthogonal to the focusing direction, and the objective lens have been described above. An objective lens driving device having means for driving in the focusing direction and the tracking direction is known, and is described in, for example, Japanese Patent Application Laid-Open No. 59-221839. In this known objective lens driving device, a holder that holds the objective lens is supported by a base so as to be displaceable in the focusing direction and the tracking direction via four mutually parallel metal wires. Further, in order to drive the objective lens in the focusing direction and the tracking direction, a focusing coil is wound around the holder to surround the objective lens, and a pair of tracking coils are provided symmetrically with respect to the optical axis of the objective lens. A magnetic circuit cooperating with is provided on the base on both sides with respect to the optical axis of the objective lens.

However, the above-mentioned JP-A-59-221839.
In the device of the publication, a lens (reference numeral 1) is fixed to the center of a holder (reference numeral 2) that is a movable body, so that a holder (reference numeral 2), a focusing coil (reference numeral 3), and a tracking coil (reference numeral) that do not pass light. Since there is a mixture of members such as 4) and members having completely different properties such as lenses that allow light to pass therethrough, there is a drawback that the structure of the device and the assembly work of the device become complicated.

As a device for solving such a drawback, there is an apparatus disclosed in JP-A-59-2012238. FIG. 7 of the publication describes the construction of a so-called sliding type optical head. Such an optical head has a configuration in which a lens that allows light to pass along the information track direction and a focusing coil and a tracking coil that do not pass light are separately arranged. However, in the sliding type apparatus, the weight of the movable body (consisting of the bobbin 51 and the arm 30) becomes large, and therefore, there is a drawback in that good responsiveness of focusing drive and tracking drive cannot be obtained. Moreover, in the sliding type device, the movable body is supported by the base so as to be movable in two directions in relation to the shaft and the bearing, and the movable body and the base are provided in order to give a restoring force to the movable body. 3 between the board (reference numeral 46)
An elastic member (reference numeral 52) that is displaceable in the dimension is connected. Therefore, the device shown in FIG. 7 of JP-A-59-2012238 has a drawback that the structure is complicated and the device is expensive.

Furthermore, the device disclosed in Japanese Patent Laid-Open No. 59-2012238 does not consider the relationship between the center of gravity of the movable body and the center of the driving force generated in the focusing coil. In such a configuration, a rotational moment may be generated around the center of gravity of the movable body during focusing driving, and as a result, the focusing driving force is not accurately transmitted to the lens, and highly accurate focusing driving cannot be expected.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lens driving device which solves the above drawbacks. The lens driving device of the present invention comprises a base and a lens having an optical axis parallel to the first direction perpendicular to the medium surface of the recording medium in order to read the information on the recording medium in which information is recorded in a track shape. The fixed movable body is connected by a connecting member having elasticity capable of displacing in two directions, and the first coil for moving the lens in the first direction and the lens are parallel to the medium surface. A second coil for moving in a second direction across the information track is fixed to the movable body, and the movable body in a third direction perpendicular to both the first direction and the second direction. The lens is arranged at one end of the movable body, and the movable body is divided into a first portion and a second portion by a virtual plane that is perpendicular to the third direction and includes the optical axis of the lens. , The first including the other end of the movable body Both the first coil and the second coil are arranged in the portion of 1., and the magnetic flux generated from the magnetic field generating means fixed to the base is directed to the both coils, In a lens driving device configured to move the lens in the first direction and the second direction by using a force generated in a coil, in the second direction of the movable body, the lens is moved in the first direction. An integrally formed member that forms a penetrating opening and arranges the lens and the opening along the third direction so that the connecting member can be displaced only in a direction substantially perpendicular to the third direction (midway) A continuous member having no coupling portion), and the center of gravity of the coupling body including at least the lens, the movable body, and the both coils, and the drive generated in the first coil. It is characterized in that a center is constructed as substantially matching.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described in detail below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. FIG. 1 is an external perspective view and FIG. 2 is an exploded perspective view. The objective lens 1 for irradiating a light spot on a recording medium such as an optical disc is attached to one end of a holder 2. The holder 2 has a thin plate-shaped end on which the objective lens 1 is mounted, and a frame-shaped end on the other end that extends in the optical axis direction of the objective lens 1 and has a focusing coil at the other end. 3 is wound and a pair of tracking coils 4 is attached to one side surface thereof.

The holder 2 is displaced in the focusing direction (Z direction) parallel to the optical axis of the objective lens 1 to focus the light spot on the recording medium, and at the same time, in the direction of the information track on the recording medium (Y direction) and In order to make the light spot follow the information track by displacing in the tracking direction (X direction) orthogonal to the optical axis, two opposite sides are opposed in the Z direction with the Y direction passing through the optical axis of the objective lens 1 as a boundary. Then, it is supported by posts 6a and 6b which are erected on the base 6 through a total of four wires 5 extending in the Y direction in parallel with each other.

The base 6 is made of a magnetic material, and forms a magnetic circuit having a permanent magnet 7 generating a magnetic flux that intersects with the focusing coil 3 and the tracking coil 4. In such a configuration, when a current having an amplitude and a polarity according to the magnitude and direction of the focusing error and the tracking error is passed through the focusing coil 3 and the tracking coil 4, the holder 2 is caused by the electromagnetic action with the magnetic circuit having the permanent magnet 7.
Therefore, the objective lens 1 is displaced in each of the Z direction and the X direction in accordance with the currents, whereby focusing control and tracking control of the light spot on the recording medium can be performed. In the above configuration, when focusing control is performed, the action point of the driving force and the objective lens 1 are deviated in the Y direction, so that there is a risk of causing torsional resonance around the axis in the X direction. Therefore, in this embodiment, the holder 2 is provided with the balancer 8 so that the center of gravity of the movable portion having the objective lens 1, the holder 2, the focusing coil 3 and the tracking coil 4 in the Y direction coincides with the point of application of the driving force. Further, the balancer 8 balances in the Y direction and at the same time, balances in the Z direction for matching the position of the center of gravity of the movable portion in the Z direction with the point of application of the driving force for the tracking control. It prevents the occurrence of torsional resonance around the Y-direction axis.

According to this embodiment, the objective lens 1 is mounted on one end of the holder 2, the focusing coil 3 and the tracking coil 4 are provided on the other end, and one magnetic circuit cooperating with these coils is held by the holder. Since the base 6 is provided so as to correspond to the other end of the base 2, it is possible to secure a sufficient space between the objective lens 1 and the base 6. Therefore, if necessary, as shown in FIG. 3, an optical element 9 such as a reflecting prism, a mirror, a collimator lens or the like can be arranged in this portion, whereby the apparatus can be made thin and the objective lens 1 The optical path to can be taken in any of the X, Y, and Z directions. Further, since there is only one driving means including the magnetic circuit and the coil, there is an advantage that the cost is lower than that of the conventional example.

FIG. 4 is a plan view showing the main part of the second embodiment of the present invention. In this embodiment, the wires 5 on both sides of the Y direction passing through the optical axis of the objective lens 1 that holds the holder 2 on the base so as to be displaceable in the Z direction and the X direction are arranged so as to intersect in the Y direction. Other configurations are the same as those of the first embodiment. According to this embodiment, the first
In addition to the effects of the embodiment, the resonance frequency in the X direction and the resonance frequency in the Z direction can be independently selected, and torsional resonance around the axis in the Z direction of the movable portion can be effectively prevented, and tracking can be performed. The control and focusing control can be performed more accurately.

It should be noted that the present invention is not limited to the above-described embodiments, but many variations and modifications are possible. For example, the number of wires 5 for holding the holder 2 is not limited to four, and it is also possible to use three wires on each side and a total of six wires or more, and by covering these wires 5 with a viscoelastic body, a damping action is provided. Alternatively, the wire 5 can be shared as a lead wire to the coil. The wire 5 may be arranged on the other end side of the holder 2. Further in FIG.
Although the wires 5 on both sides of the objective lens 1 which pass through the optical axis of the objective lens 1 and which are bordered by the Y direction are arranged so that the distance between the wires 5 is narrow on the objective lens 1 side, they may be arranged so as to widen.

[0013]

According to the lens driving device of the present invention, in order to read information on a recording medium on which information is recorded in a track form,
A movable body (for example, the base and a lens having an optical axis parallel to the first direction (Z direction in the above embodiment) perpendicular to the medium surface of the recording medium (for example, the objective lens 1 in the above embodiment) is fixed. The holder 2 and the balancer 8 of the embodiment are connected to each other by a connecting member (for example, the wire 5 of the embodiment) having elasticity capable of displacing in two directions, and the lens is moved in the first direction. A first coil for moving the lens and a second coil for moving the lens in a second direction (for example, the X direction in the embodiment) parallel to the medium surface and crossing the information track are provided on the movable body. It is fixed and one end of the movable body with respect to a third direction perpendicular to both the first direction and the second direction (see, for example, FIG.
The lens is arranged at the right end of the holder 2 as shown in FIG.
Direction) and an imaginary plane that includes the optical axis of the lens and defines the movable body in the first portion (for example, in the case of the holder 2 of FIG. 3 in the above embodiment, the optical axis of the lens 1 indicated by a chain line). With respect to the right side) and a second part (for example, in the case of the above-mentioned embodiment, regarding the combined body of the holder 2 and the balancer 8 in FIG. 3, the left side with respect to the optical axis of the lens 1 indicated by the alternate long and short dash line). Then, the second portion including the other end portion of the movable body (for example, the left end portion of the combined body of the holder 2 and the balancer 8 in the embodiment where the balancer 8 is arranged) is Both of the first coil and the second coil are arranged, and the magnetic flux generated from the magnetic field generating means fixed to the base is directed to the both coils to generate them in the both coils. Use the force to In a lens driving device configured to move a lens in the first direction and the second direction, an opening penetrating in the first direction in the second portion of the movable body (see the above-mentioned Japanese Patent Laid-Open No. 59-59). (Compared to the hole area of the bearing formed in the bobbin 51 for inserting the shaft 34 described in FIG. 7), the lens and the opening are formed along the third direction. And the connecting member is formed as an integrally formed member that can be displaced only in a direction substantially perpendicular to the third direction, and at least the combination of the lens, the movable body, and the coils is included. Since the center-of-gravity value and the center of the driving force are made to substantially coincide with each other, not only the structure of the device and the assembling work of the device are simplified, but also the rotating body is rotated on the movable body during focusing driving. There not occur, there is an advantage that highly accurate focusing drive becomes possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a form of use of the first embodiment of the present invention.

FIG. 4 is a plan view showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Lens 2 Holder 3 Focusing Coil 4 Tracking Coil 5 Wire 6 Base 7 Permanent Magnet 8 Balancer 9 Optical Element

Claims (1)

[Claims] 1. A base and a lens having an optical axis parallel to a first direction perpendicular to a medium surface of the recording medium are fixed in order to read information on a recording medium in which information is recorded in a track shape. A movable member is connected by a connecting member having elasticity capable of displacing in two directions, and a first coil for moving the lens in the first direction and the lens are parallel to the medium surface to form an information track. A second coil for moving in a second direction traversing is fixed to the movable body;
The lens is arranged at one end of the movable body in a third direction which is perpendicular to both the direction and the second direction,
Further, when the movable body is divided into a first portion and a second portion by an imaginary plane that is perpendicular to the third direction and includes the optical axis of the lens, the other end portion of the movable body is included. The both coils of the first coil and the second coil are arranged in the second portion, and by directing the magnetic flux generated from the magnetic field generating means fixed to the base to the both coils, In the lens driving device configured to move the lens in the first direction and the second direction by using the driving force generated in the both coils, the first portion is provided on the second portion of the movable body. Is formed integrally with the lens and the opening along the third direction so that the connecting member can be displaced only in a direction substantially perpendicular to the third direction. Composed of members At the same time, the position of the center of gravity of the combined body including the lens, the movable body, and the both coils, at least, and the center of the driving force generated in the first coil are substantially aligned with each other. Lens drive device.