JPH05774B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a lens actuator for an optical head that uses optical means to record information on the surface of a recording medium, or to reproduce or erase information that has already been recorded. The present invention relates to a lens actuator, and particularly to a lens actuator that moves a condenser lens in a focusing direction perpendicular to the surface of a recording medium and in a tracking direction parallel to the surface of a recording medium.

[Conventional technology]

Conventionally, optical technology uses laser light as a light source and modulates this laser light with pulsed signals from an external information source to record binary information on the surface of a recording medium, or to reproduce or erase information that has already been recorded. In order to accurately record, reproduce, or erase information, the head uses a lens actuator to control the focusing direction so that the surface of the recording medium is always at the focal point of the condensing lens. In other words, the direction of the optical axis of the condensing lens is controlled, and the optical spot of the focused laser beam on the surface of the recording medium is accurately positioned with respect to the guide groove formed in advance on the surface of the recording medium. As if
Tracking position control is performed by driving the condenser lens in a tracking direction perpendicular to the guide groove.

Various configurations of this lens actuator have been proposed, one of which is one in which movable support in the focusing direction is supported by parallel leaf springs, and movable support in the tracking direction is supported by a swing support mechanism. . For example, the lens actuator shown in Japanese Utility Model Application No. 195934/1980 corresponds to this. In this lens actuator, the movable part on which the condenser lens is mounted is supported in the focusing direction by four leaf springs whose ends are connected to the top and bottom of the movable part on both sides in the tracking direction. The arm to which the other end is connected is supported from the housing by a swing support mechanism that is swingable about one axis parallel to the focusing direction. In addition, the generation of driving force in the focusing and tracking directions of the movable part is achieved by two magnetic circuits installed on both sides of the condensing lens in the tracking direction on the housing, and a focusing lens mounted on the movable part. The center of gravity of the movable part is driven by an electromagnetic drive mechanism composed of a coil and a tracking coil made up of a plurality of small coils provided on the movable part corresponding to each magnetic circuit.

[Problem that the invention seeks to solve]

However, in this lens actuator, the driving force is set to act on the center of gravity of the movable part, so when the movable part receives the driving force, it causes translational movement. For this reason, as the lens actuator becomes smaller, the radius of rotation of the movement in the tracking direction performed by the rocking motion becomes smaller, and the rotational movement of the movable part itself due to the rocking motion cannot be ignored. There is a discrepancy between the driving force that causes the translational movement of the movable part and the direction of movement of the movable part determined by the swing support mechanism, and an unbalanced force that is essentially unnecessary for movement is generated, causing the lens actuator in the tracking direction to This is a cause of disturbances in the eta characteristics.

The purpose of the present invention is to eliminate such drawbacks and
To provide a lens actuator in which the operating direction of a movable part in the tracking direction and the operating direction of a driving force, including the posture of the movable part, are made to match, and disturbances in characteristics in the tracking direction are suppressed.

[Means for solving problems]

The present invention is a lens actuator that moves a focusing lens that focuses light from a light source onto a recording medium surface in a focusing direction perpendicular to the recording medium surface and in a tracking direction parallel to the recording medium surface. , a movable part on which the condensing lens is mounted; a plurality of parallel leaf springs having one end connected to the movable part and movable in the focusing direction; an arm to which the other ends of these leaf springs are connected; a swing support mechanism that supports the movable part from the housing so as to be swingable about one axis substantially parallel to the focusing direction; a focus coil that is provided in the movable part and moves the movable part in the focusing direction; a tracking coil, which is provided on the movable part and is configured to move the movable part in the tracking direction, and is composed of a plurality of small coils having a number of turns approximately proportional to the distance from the one axis parallel to the focusing direction; The present invention is characterized in that it includes two magnetic circuits that are provided and magnetically coupled to the focus coil and the tracking coil on both sides of the condenser lens in a direction perpendicular to the tracking direction.

[Effect]

According to the configuration of the present invention, each small coil of the tracking coil generates a driving force proportional to the distance from the rotation center axis of the swing support mechanism by the same applied current, and therefore the movable part It is accelerated to move and rotate while maintaining the relative positional relationship with respect to the rotation center axis. As a result, the operating direction of the movable portion and the operating direction of the driving force match, and it is possible to suppress the generation of unbalanced forces that would cause disturbances in the actuator characteristics in the tracking direction.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an exploded perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view. For convenience of explanation, three-dimensional coordinates (x, y, z coordinates) are shown in FIG. 1, and the x-coordinate direction corresponds to the tracking direction, and the z-coordinate direction corresponds to the focusing direction.

In this embodiment, the lower surfaces of one end of leaf springs 3a and 3b are attached to the upper surface of the upper protrusion at both ends in the tracking direction (x coordinate direction) of the movable part 2 on which the condenser lens 1 is mounted, and the movable part 2 is movable. A leaf spring 3 is attached to the lower surface of the lower protruding portion at both ends in the tracking direction of the portion 2.
The upper surfaces of one end of a' and 3b' are attached respectively. These four leaf springs 3a, 3b, 3a', 3
b' extends in the y-coordinate direction.

The lower surface of the other end of the leaf spring 3a and the lower surface of the other end of the leaf spring 3b are attached to the upper surface of the arm 4, and the upper surface of the other end of the leaf spring 3a' and the upper surface of the other end of the leaf spring 3b' are A leaf spring 3a is attached to the lower surface of the arm 4.
is attached to the plate spring 3a', and the plate spring 3b is attached so as to be parallel to the plate spring 3b'. These four leaf springs 3a, 3b, 3a', 3b' allow the movable part 2 to
It is movably supported in the focusing direction (z-coordinate direction).

The arm 4 is connected to a swing support mechanism 5 and supported so as to be swingable about an axis 7 parallel to the focusing direction (z coordinate direction). Specifically, the swing support mechanism 5 is configured using a rolling bearing, a sliding bearing, a combination leaf spring, and the like. Thereby, the movable part 2 is movably supported also in the tracking direction (x-coordinate direction).

The movable part 2 moves in the tracking direction (x coordinate direction)
Two holes 13a and 13b are opened in the focusing direction (z-coordinate direction) at positions on both sides of the condensing lens 1 in a direction perpendicular to the focusing direction. A focus coil 8 is placed in a direction parallel to the xy coordinate plane so as to surround these two holes 13a and 13b and the condenser lens 1.
is wound on the focus coil 8, and 4
Two tracking coils 9 are attached. The tracking coil 9 is a small coil wound into a substantially rectangular thin donut shape, and has holes 13a, 1
In a portion corresponding to the y-coordinate direction of 3b, the coil is arranged so that current mainly flows in the focusing direction (z-coordinate direction) on one side of the coil. Further, each of the four tracking coils 9 has a number of turns approximately proportional to the distance from the shaft 7 of the swing support mechanism 5 to each coil.

On the housing 6 are center yokes 10a, 10b,
Magnets 11a, 11b, side yokes 12a, 12
Two magnetic circuits are installed, each consisting of a hole 13
a, 13b, and one side of the tracking coil 9 and a part of the focus coil 8 are located in the gap of the magnetic circuit.

A magnetic flux is generated in the gap of the magnetic circuit in the y-coordinate direction, and as a result, the movable part 2 is driven in the focusing direction (z-coordinate direction) by applying a current to the focusing coil 8, and the tracking coil 9 is driven in the focusing direction (z-coordinate direction). is driven in the tracking direction (x-coordinate direction) by applying a current to the condenser lens 1.
movement in the focusing direction (z coordinate direction) and tracking direction (x coordinate direction).

According to the configuration described above, the driving force of the movable part 2 in the tracking direction (x coordinate direction) is proportional to the number of turns of the tracking coil, that is, the driving force is proportional to the distance from the shaft 7 to the tracking coil. Therefore, in addition to translational acceleration, the movable portion also generates rotational acceleration such that the movable portion 2 and the shaft 7 always maintain the same relative positional relationship. Therefore, the movable part 2 defined by the swing support mechanism 5
The operating direction of the movable part 2 and the operating direction of the driving force are almost the same, including the posture of the movable part 2, so that an unbalanced driving force unnecessary for the operation is not generated, and the characteristics in the tracking direction are not disturbed. .

Furthermore, by changing the wire diameter of the coil wire according to the number of turns of each tracking coil 9 and making the weight of each tracking coil almost the same, it is possible to easily align the center of gravity of the movable part 2 with the focusing direction (z coordinate direction). The operating axis of the driving force can be made to coincide with the operating axis of the driving force.

With this configuration, it is possible to realize a lens actuator that does not cause any disturbance in the characteristics in the focusing direction regardless of the difference in the number of turns of each tracking coil.

〔Effect of the invention〕

As explained above, the lens actuator according to the present invention matches the operating direction of the movable part in the tracking direction with the operating direction of the driving force, suppresses the generation of unbalanced driving force unnecessary for the operation, and This has the effect of suppressing disturbances in the characteristics of.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view. 1... Condenser lens, 2... Movable part, 3a, 3
a', 3b, 3b'...plate spring, 4...arm, 5...
...Rocking support mechanism, 6... Housing, 7... Axis, 8...
Focus coil, 9...Tracking coil,
10a, 10b...center yoke, 11a, 1
1b... Magnet, 12a, 12b... Side yoke, 13a, 13b... Hole.

Claims (1)

[Scope of Claims] 1. A lens actuator that moves a condensing lens that focuses light from a light source onto a recording medium surface in a focusing direction perpendicular to the recording medium surface and in a tracking direction parallel to the recording medium surface. a movable part on which the condensing lens is mounted; a plurality of parallel leaf springs having one end connected to the movable part and movable in the focusing direction; and an arm to which the other ends of these leaf springs are connected. , a swing support mechanism that supports this arm from a housing so as to be able to swing around one axis substantially parallel to the focusing direction; and a focus that is provided on the movable part and moves the movable part in the focusing direction. a tracking coil, which is provided on the movable part and is configured to move the movable part in the tracking direction, and includes a plurality of small coils having a number of turns approximately proportional to the distance from the one axis parallel to the focusing direction; A lens actuator comprising two magnetic circuits provided in the housing and magnetically coupled to the focus coil and the tracking coil on both sides of the condenser lens in a direction perpendicular to the tracking direction. Yueta. 2. The lens actuator according to claim 1, wherein the tracking coil is composed of a plurality of small coils, all of which have approximately the same weight and have different wire diameters depending on the number of turns. lens actuator.