JPH02130730A - Lens actuator - Google Patents

Abstract

PURPOSE:To reduce the rolling phenomena of a condenser lens and condenser lens holding body without causing any unnecessary resonance by using H-type wire springs as the wire spring for holding the condenser lens holding body. CONSTITUTION:A pair of H-type wire springs 5 are respectively fitted between a fixed section 10 and condenser lens holding body 2 and hold the holding body 2 in a state where the holding body 2 can be free along two axes in the focusing direction parallel to the optical axis and tracking direction perpendicular to the optical axis. Accordingly, inclination of a condenser lens and its holding body in their rolling directions can be suppressed easily and occurrence of unnecessary resonance is eliminated. Therefore, stable tracking servo and track access are performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lens actuator, and particularly to a lens actuator that records information on the surface of an information recording medium using optical means, such as an optical information device or a data file device, or The present invention relates to a lens actuator that causes a lens to follow the surface runout and eccentricity of a disk in an optical head that reproduces or erases already recorded information.

[Conventional technology]

Optical disk memories are capable of high-density recording by recording and reproducing information using laser light focused to about 1 μm. In order to achieve this high recording density, the focused light from the condensing lens of the lens actuator must be correctly focused on all the replaced disks and traced without deviating from a single trunk. . In other words, the lens actuator is a very important key component that allows the focusing lens to follow the surface runout of the disk and the eccentricity of the recording track with submicron accuracy in order to maintain this good beam focusing state at all times. It is.

The lens of the lens actuator is usually designed as a combination lens that also includes the substrate of the disk or a cover glass, and when the condensing lens is tilted with respect to the disk, this combination shifts, causing aberrations in the focused beam. Currently, the tilt of the condensing lens of the lens actuator that is permissible on the device side is about several minutes. Further, in order to make the condenser lens follow a surface runout of about 100 μm and eccentricity with submicron precision, a servo band of about 1 to 2 kllz is required.

Therefore, a lens actuator for an optical disk memory is required to have wide-band dynamic characteristics and maintain accurate posture of the lens.

The mainstream of lens actuators is a two-dimensional drive method in which they are driven in a focus direction and a tracking direction, and are roughly classified into a sliding type and a spring support type depending on the method of supporting the movable part. However, the sliding type suffers from vibration of the shaft due to the mechanical gap between the shaft and the sleeve.
Although it is generally used for optical disc memory devices, it is difficult to employ it in devices that require highly accurate and reliable lens position control, such as optical disk memory devices.

Therefore, in order to make it possible to control the lens position with high accuracy and confidence, a lens actuator has been developed that supports a holder that holds a condensing lens using four wire springs.

An example of such a lens actuator is shown in FIG. For convenience of explanation, an orthogonal coordinate system is set in FIG. 4, with the X-axis direction being the tracking direction and the Z-axis direction being the focus direction. This lens actuator includes a condensing lens 31 that condenses laser light onto the information recording medium surface;
A holder 32 that holds this condensing lens 31, four wire springs 33 that support this holder 32 and are parallel to each other in the y-axis direction, and four wire springs that have one end attached to the holder 32. Fixed part 34 to which the other end of 33 is attached
and a focus direction drive coil 35 which is fixed to the holder 32 and drives the condenser lens 31 in the focus direction (Z-axis direction) and four tracking direction drive coils 36 which drive the condenser lens 31 in the tracking direction (X-axis direction). Magnets 37A, 37B are arranged to face each drive coil and form a magnetic circuit, and yokes 38A, 38B, 39A, 39 are attached to the housing 40.
It consists of B. And magnets 37A and 37B are
A yoke 38 facing the focus direction drive coil 35
It is attached to the opposing surfaces of A and 38B.

The magnetic circuit of this lens actuator is a yoke 38A,
39A and magnet 37A, and yoke 38B,
39B and magnet) 37B, and when a current is passed through the focus direction drive coil 35, the holder 32
is driven in the focus direction (z-axis direction). Furthermore, when a current is applied to the tracking direction drive coil 36, the holder 32 is driven in the tracking direction (X-axis direction).

In this way, this lens actuator supports the condenser lens with four wire springs of equal length arranged in the direction from the housing, so that the condenser lens is parallel to both the focus and tracking drive directions. It is configured to be movable.

This wire spring-supported lens actuator has a simple structure of the supporting part, so its characteristics are straightforward and unnecessary resonance does not occur (a wide band can be expected).

Furthermore, it has advantages such as being suitable for miniaturization, thinning 2 and weight reduction, and being easy to manufacture.

[Problem to be solved by the invention]

However, in the conventional lens actuator described above, the restraining force in the rotational direction of the holder that holds the condensing lens is comparable to the restraining force in the focusing and tracking directions, and the rigidity is extremely weak, so it cannot be used in the rolling direction. Easy to vibrate. This movement in the rolling direction causes the condensing lens to tilt, which causes the tracking error signal to wave due to the tilt of the condenser lens at the acceleration/deceleration point during high-speed seek, and is an unstable factor in track jump operation. It has the disadvantage of becoming.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lens actuator that can eliminate such drawbacks and suppress vibrations of a condensing lens in the rolling direction.

[Means to solve the problem]

The lens actuator of the present invention includes: a condensing lens that condenses laser light onto the surface of an information recording medium; a holder that holds the condensing lens; a plurality of spring parts; and a beam provided in a predetermined direction so as to reduce the rolling phenomenon of the holder, and these spring parts allow two directions: a focusing direction parallel to the optical axis of the condensing lens, and a tracking direction perpendicular to the optical axis. a support means for supporting the holder so as to be movable about a shaft; a focusing coil fixed to the holder for driving the condensing lens in the focusing direction; and a tracking coil for driving the condensing lens in the tracking direction. , a pair of permanent magnets that are arranged to face each other with the focus coil and tracking coil in between to form a magnetic circuit, and a yoke.

[Effect]

The present invention uses an H-shaped wire spring in which a beam is inserted parallel to the tracking direction or the focusing direction, respectively, as the wire spring that supports the holder that holds the condenser lens. By doing so, it is possible to easily reduce the rolling phenomenon of the condenser lens and its holder without generating unnecessary resonance.

〔Example〕

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

FIG. 1 is a perspective view showing an embodiment of the present invention. In addition, for convenience of explanation, an orthogonal coordinate system is set in Fig. 1, and
The axial direction is the tracking direction, and the z-axis direction is the focusing direction. This lens actuator includes a condenser lens 1, a holder 2, a focus coil 3, a tracking coil 4, an H-shaped wire spring 5, and yokes 7A and 7B.
, 9A.

9B, permanent magnets 8A and 8B, a fixed part 10, and a housing 11.

In the lens actuator having such a configuration, the condenser lens 1 condenses laser light onto the surface of the information recording medium.

The holder 2 holds the condensing lens 1. Holes 2A and 2B are formed in the holder 2 at positions on both sides of the condenser lens 1 and in the y-axis direction.

A focusing coil 3 that drives the focusing lens 1 and its holder 2 in the focusing direction, and a tracking coil 4 that drives the holder 2 in the tracking direction surround the two holes 2A and 2B and the focusing lens 1. is fixed to.

The fixing part 10 is attached to the end of the housing 11 in the y-axis direction so that the elongated direction of one surface 10A is parallel to the X-axis direction.
It is attached to the housing 11.

The H-shaped wire springs 5 are respectively attached between the fixing part 10 and the holder 2, and move the holder 2 in the focusing direction (z-axis direction) parallel to the optical axis and in the tracking direction (X-axis direction) perpendicular to the optical axis. It is supported so that it can move freely in two axes (in the axial direction). When supporting the holder 2 so that it can move freely in two axes, as shown in FIG. 4, if the holder 2 holding the condensing lens is supported by four wire springs, The rigidity of the roller is extremely stiff, and it is easy to vibrate in the rolling direction.

Therefore, by attaching a beam parallel to the focus direction between the four wire springs supporting the holder 2 to increase the rigidity in the rolling direction, the inclination of the condenser lens will be reduced compared to before attaching the beam. It is theoretically required by vibration analysis that this decrease to 1/10 or less. It has also been experimentally confirmed that the vibration of the condenser lens in the rolling direction is reduced by attaching the beam. However, it is extremely time-consuming to install these beams one by one by hand. In addition, it is difficult to achieve mechanical precision, and even a slight deviation in balance can cause unnecessary resonance. Therefore, the third
As shown in the figure, from the beginning there is a beam 5B and two wire spring parts 5.
By using the H-shaped wire spring 5 in which A is integrated, it can be easily and accurately attached.

Furthermore, when this H-shaped wire spring 5 is used, unnecessary resonance is less likely to occur due to imbalance. The H-shaped wire spring 5 integrated with the beam 5B can be easily obtained by etching a thin plate into an H-shaped wire spring. This embodiment uses such an H-shaped wire spring 5.
The holding body 2 is supported using two. That is, H
One end of the wire spring part 5A of the type wire spring 5 is connected to the fixed part 1
0 is attached to the other surface of the fixing portion 10 that is opposite to one surface 10A of the fixing portion 10 . At this time, each H-shaped wire spring 5 is attached so that the longitudinal direction of the beam 5B of the H-shaped wire spring 5 is parallel to the focus direction (z-axis direction). On the other hand, the other ends of the wire spring portions 5A of the type 1 wire springs 5 are respectively attached to the surface 2C of the holder 2. The two H-shaped wire springs 5 attached in this way allow the holding body 2 to be
Supported for free axis movement.

Permanent magnets 8A and 8B are connected to the focus coil 3 of the holder 2.
are arranged so as to sandwich them from the y-axis direction, and are attached to the yokes 7A and 7B, respectively.

Further, the yokes 7A and 7B are attached to the body 11. Further, yokes 9A and 9B are arranged in holes 2A and 2B of holding body 2, respectively.

In this way, a pair of permanent magnets 8A and 8B are placed opposite each other with the focus coil 3 and tracking coil 4 in between.
, and yokes 7A, 7B, 9A, and 9B are arranged to form a magnetic circuit.

With such a lens actuator, it is possible to easily reduce the rolling phenomenon of the condenser lens and its holder without generating unnecessary resonance.

FIG. 2 is a perspective view showing another embodiment of the invention. In this lens actuator, the mounting position of the H-shaped wire spring is changed from the lens actuator shown in FIG. 1.

That is, in this embodiment, one end of the wire spring part 6A of the H-shaped wire spring 6 is connected to the fixed part so that the beam 6B of the two H-shaped wire springs 6 is parallel to the tracking direction (X-axis direction). 10, and the other ends of the wire spring portions 6A are respectively attached to the surface 2C of the holder 2. By supporting the holder 2 with the two H-shaped wire springs 6 in this way, in the direction in which the holder 2 is twisted, as in the embodiment shown in FIG.
The rigidity is increased and the tilting of the condenser lens can be suppressed.

〔Effect of the invention〕

As described above, the present invention enables stable tracking servo and track access operations because the inclination of the condensing lens and its holder in the rolling direction is easily suppressed without generating unnecessary resonance. This has the effect of making it possible.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing an embodiment of the present invention.
FIG. 3 is a perspective view showing another embodiment of the present invention; FIG. 3 is a perspective view showing an example of an H-shaped wire spring integrated with a beam; FIG. 4 is an example of a conventional wire-supported lens actuator. FIG. 1... Condenser lens 2... Holder 2A, 2B... Hole 2C, IOA... Surface 3... Focusing coil 4... Tracking coil 5. 6...H-shaped wire springs 5A, 6A...Wire spring parts 5B, 6B...Beams 7A, 7B, 9A, 9B...Yoke 8A, 8B...Permanent magnet 10...Fixed Part 11...Kyōtai

Claims (1)

[Claims] (1) A condensing lens that condenses a laser beam onto the surface of an information recording medium, a holder that holds the condensing lens, a plurality of spring parts, and a rolling part of the holder at the part of these spring parts. The beam is provided in a predetermined direction to reduce the phenomenon, and these spring parts allow movement in two axes: a focusing direction parallel to the optical axis of the condensing lens and a tracking direction perpendicular to the optical axis. a support means for supporting the holding body so that the holding body is fixed to the holding body, a focusing coil for driving the condensing lens in the focusing direction, and a tracking coil for driving the condensing lens in the tracking direction; and the focusing coil and the tracking coil. A lens actuator that includes a pair of permanent magnets that are arranged opposite to each other to form a magnetic circuit, and a yoke.