JPH0573938A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To provide a thin objective lens driving device having a stable displacement frequency characteristic. CONSTITUTION:An objective lens 1 is held at almost the center of a U-shaped lens holder 2, and permanent magnets 3a and 3b for driving are provided at the both edge parts of the lens holder 2. The lens holder in the neighborhoods of a part where the objective lens is attached can be made thin, so that the entire device can be made thin. And also, the center of a driving force can be made coincident with the center of the objective lens, the influence of the unbalance of a centroid or the like can be prevented, and the stable displacement frequency characteristic can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical axis adjusting device for an optical disk device, which is a so-called objective lens driving device, for optically writing or reading information on a disk-shaped recording medium.

[0002]

2. Description of the Related Art In an optical disk apparatus, in order to correct a focus deviation due to vertical movement of a warp of a disk-shaped recording medium such as a compact disk or an optical disk and a tracking deviation due to eccentricity, an objective lens is arranged in a direction perpendicular to a surface of the recording medium. Optical axis direction (hereinafter referred to as focus direction F) and a radial direction (hereinafter referred to as tracking direction T) parallel to the recording medium surface to optically record,
Erase or play.

In recent years, data file devices using compact disc players and optical discs have become portable,
As personalization is progressing, optical pickups used for them are required to be further downsized, especially thin.

An example of the above-mentioned conventional objective lens driving device for an optical pickup will be described below with reference to the drawings.

FIG. 6 is a front view of a conventional objective lens driving device, FIG. 7 is a sectional view taken along line BB of FIG. 6, and FIG. 8 is an exploded perspective view showing the structure. In FIGS. 6, 7, and 8, 1 is an objective lens. A lens holder 2 holds the objective lens 1. 3a and 3b are magnets, and 4a to 4d are metal wires for supporting the lens holder 2. 5a and 5b are magnetic yokes and are magnets 3
A magnetic circuit is formed with a and 3b. 6 is a tracking coil, 7 is a focusing coil, and the lens holder 2
It is wound around. 8 is a fixing member, and metal wires 4a-4b
One end of is attached. Reference numeral 9 denotes a base, to which a reflecting mirror 10 for guiding light emitted from a semiconductor laser as a light source to the objective lens 1 is attached.

The operation of the objective lens driving device configured as described above will be described below.

The operation of driving the objective lens in two axes of the focus direction F and the tracking direction T in order to correct the focus shift due to the vertical movement of the warp of the disk and the tracking shift due to eccentricity will be described.

A lens holder 2 to which an objective lens 1 is attached
Is supported by four metal wires 4 a to 4 d, one end of which is fixed to the fixing member 8 and the other end thereof to the lens holder 2 and which are arranged in parallel with each other, and the fixing member 8 is attached to the base 9. The light emitted from the semiconductor laser (not shown) is incident on the objective lens 1 by the mirror 10. In driving in the focus direction F, the lens holder 2 to which the objective lens 1 is attached is moved to the magnet 3a attached to the base 9, 3B and the magnetic yokes 5a and 5b, and is obtained by translational movement through the metal wires 4a to 4d by an electrokinetic converter in which the focusing coil 7 is arranged in the air gap of the magnetic circuit. The driving in the tracking direction T is performed by moving the lens holder 2 having the objective lens 1 with the tracking coil 6 arranged in the air gap of the magnetic circuit including the magnets 3a and 3b and the magnetic yokes 5a and 5b attached to the base 9. It is obtained by translational movement via the metal wires 4a-4d by means of an electrotype converter.

Further, the whole objective lens driving device is driven and driven by a motor in the access direction Ac (the same direction as the tracking direction T) on the recording medium.

The objective lens 1 is attached to the lens holder 2 outside the magnetic field effective region in the tracking direction T of the magnetic circuit composed of the magnets 3a and 3b and the magnetic yokes 5a and 5b, and the objective of the lens holder 2 is attached. The thickness t1 of the lens mounting portion in the focus direction is made thinner than the thickness t2 of the lens holder 2 in the focus direction in the magnetic field effective region of the magnetic circuit. Therefore, the objective lens 1 and the mirror 10
And can be brought close to each other, and the overall thinning of the device can be achieved.

[0011]

However, in the above-mentioned structure, since the objective lens is arranged outside the range of the magnetic field effective area of the magnetic circuit in order to achieve the thinning of the entire optical head, the center of the driving force is reduced. And the center of the objective lens shift,
There is a problem that the displacement frequency characteristic of the objective lens driving device in the focus direction F is adversely affected by the influence of unbalance of the center of gravity.

In view of the above problems, the present invention provides an objective lens driving device which achieves a thin optical head as a whole and has stable displacement frequency characteristics.

[0013]

In order to solve the above-mentioned problems, an objective lens driving device of the present invention holds an objective lens substantially at the center of a U-shaped lens holder, and a plurality of lens holders are provided at both ends of the lens holder. It is equipped with a permanent magnet for driving.

[0014]

According to the present invention, the lens holder near the mounting of the objective lens can be made thin and the optical head as a whole can be made thin, and at the same time, the center of the driving force and the center of the objective lens can be aligned with each other. It is possible to realize an objective lens driving device having stable displacement frequency characteristics without being affected by the imbalance of the center of gravity.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An objective lens driving device according to a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of an objective lens driving device according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is an exploded perspective view showing the structure. In FIGS. 1, 2 and 3, reference numeral 1 is an objective lens. A lens holder 2 holds the objective lens 1. Magnets 3a and 3b are attached to the lens holder 2, and metal wires 4a to 4d support the lens holder 2. 5a and 5b are magnetic yokes and are magnets 3
A magnetic circuit is formed with a and 3b. Tracking coils 6a and 6b and focusing coils 7a and 7b are wound around the magnetic yokes 5a and 5b, respectively. Reference numeral 8 denotes a fixing member, to which one ends of the metal wires 4a-4b are attached. Reference numeral 9 denotes a base, to which a reflecting mirror 10 for guiding light emitted from a semiconductor laser as a light source to the objective lens 1 is attached.

The operation of the objective lens driving device configured as described above will be described below. The operation of driving the objective lens 1 in two axes of the focus direction F and the tracking direction T will be described.

Lens holder 2 with objective lens 1 attached
Is supported by four metal wires 4 a to 4 d, one end of which is fixed to the fixing member 8 and the other end thereof to the lens holder 2 and which are arranged in parallel with each other, and the fixing member 8 is attached to the base 9. Light emitted from a semiconductor laser (not shown) is incident on the objective lens 1 by the mirror 10.

Driving in the focus direction F is performed by the objective lens 1.
The lens holder 2 to which is attached the electromotive force in which the focusing coils 7a and 7b are arranged in the air gap of the magnetic circuit including the magnets 3a and 3b attached to the lens holder 2 and the magnetic yokes 5a and 5b attached to the base 9. Obtained by translational movement through the metal wires 4a-4d by means of a mold converter. In the tracking direction T, the lens holder 2 having the objective lens 1 attached thereto is tracked in the air gap of the magnetic circuit including the magnets 3a and 3b attached to the lens holder 2 and the magnetic yokes 5a and 5b attached to the base 9. It is obtained by translational movement through the metal wires 4a to 4d by the electrokinetic converter in which the working coils 6a and 6b are arranged.

The entire objective lens driving device is driven by a motor in the access direction Ac (the same direction as the tracking direction T) on the recording medium.

Here, in the lens holder 2, the thickness t1 of the objective lens mounting portion in the focus direction F is the thickness t1 of the lens holder 2 in the magnetic field effective region of the magnetic circuit in the focus direction F.
It is thinner than 2. Therefore, the objective lens 1 and the mirror 10 can be brought close to each other, and the overall thickness of the optical head can be reduced. At this time, the objective lens 1 is held substantially at the center of the U-shaped lens holder 2, and two driving magnets 3a and 3b are attached to both ends of the lens holder 2. Therefore, the center of the driving force and the center of the objective lens can be made coincident with each other, and the objective lens driving device having a stable displacement frequency characteristic without the influence of the imbalance of the center of gravity can be realized.

As described above, according to this embodiment, the objective lens is held substantially at the center of the U-shaped lens holder, and a plurality of permanent magnets for driving are provided at both ends of the lens holder. It is possible to make the lens holder near the mounting thinner and achieve a thinner optical head at the same time, and at the same time, the center of the driving force and the center of the objective lens can be aligned, and there is no effect of unbalance of the center of gravity, etc. An objective lens driving device having a displacement frequency characteristic can be realized.

Next, an objective lens driving device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is an exploded perspective view showing the structure of the objective lens driving device of the second embodiment of the present invention. In FIG. 4, reference numeral 1 is an objective lens. A lens holder 2 holds the objective lens 1. Magnets 3a and 3b are attached to the lens holder 2, and metal wires 4a to 4d support the lens holder 2. 5a and 5b are magnetic yokes and are magnets 3
A magnetic circuit is formed with a and 3b. Tracking coils 6a and 6b and focusing coils 7a and 7b are wound around the magnetic yokes 5a and 5b, respectively. Reference numeral 8 denotes a fixing member, to which one ends of the metal wires 4a-4b are attached. Reference numeral 9 denotes a base, to which a reflecting mirror 10 for guiding light emitted from a semiconductor laser as a light source to the objective lens 1 is attached.

The operation of the objective lens driving device configured as described above will be described below.

The operation of driving the objective lens in two axes of the focus direction F and the tracking direction T will be described.

Lens holder 2 to which objective lens 1 is attached
Is supported by four metal wires 4 a to 4 d, one end of which is fixed to the fixing member 8 and the other end thereof to the lens holder 2 and which are arranged in parallel with each other, and the fixing member 8 is attached to the base 9. Light emitted from a semiconductor laser (not shown) is incident on the objective lens 1 by the mirror 10.

Driving in the focus direction F is performed by the objective lens 1
The lens holder 2 to which is attached the electromotive force in which the focusing coils 7a and 7b are arranged in the air gap of the magnetic circuit including the magnets 3a and 3b attached to the lens holder 2 and the magnetic yokes 5a and 5b attached to the base 9. Obtained by translational movement through the metal wires 4a-4d by means of a mold converter. In the tracking direction T, the lens holder 2 having the objective lens 1 attached thereto is tracked in the air gap of the magnetic circuit including the magnets 3a and 3b attached to the lens holder 2 and the magnetic yokes 5a and 5b attached to the base 9. It is obtained by translational movement through the metal wires 4a to 4d by the electrokinetic converter in which the working coils 6a and 6b are arranged.

Further, the entire objective lens driving device is driven and driven by a motor in the access direction Ac (the same direction as the tracking direction T) on the recording medium. The objective lens 1 is held substantially at the center of a U-shaped lens holder 2, and two driving magnets 3a and 3b are provided at both ends of the lens holder 2.
Is attached. Therefore, the lens holder near the mounting of the objective lens can be thinned, and the entire optical head can be thinned. Here, the mounting positions of the metal wires 4a to 4d to the lens holder 2 are set such that the metal wires 4a and 4b are on the side farther from the fixing member 8 with the objective lens 1 sandwiched therebetween, and the metal wires 4c and 4d are with the objective lens 1 sandwiched therebetween. It is attached to the side closer to the fixing member 8. As a result, the regulation force against the rotational movement about the axis parallel to the focus direction F and the tracking direction T is improved, and parasitic resonance is less likely to occur in the displacement frequency characteristic.

Further, the lens holder 2 is moved in the focus direction F.
Even if the metal wires 4a and 4b are displaced to
It does not block the light beam entering 0.

As described above, according to this embodiment, it is possible to reduce the thickness of the entire optical head, and at the same time, to realize an objective lens driving device having stable displacement frequency characteristics without parasitic resonance.

Further, the metal wires 4a, 4b and the metal wires 4c, 4
If the wire diameter of d is changed, the mounting positions on the fixing member 8 can be made uniform as shown in FIG. 5 even when the spring constants are made equal, and the entire apparatus can be made more compact.

[0033]

As described above, according to the present invention, the objective lens can be mounted by holding the objective lens substantially at the center of the U-shaped lens holder and providing a plurality of drive permanent magnets at both ends of the lens holder. The lens holder in the vicinity can be made thinner, and the overall thickness of the optical head can be made thinner. At the same time, the center of the driving force and the center of the objective lens can be made to coincide with each other, so that there is no effect such as imbalance of the center of gravity, and stable displacement. An objective lens driving device having frequency characteristics can be realized.

Further, the mounting positions of the rod-shaped elastic members supporting the respective lens holders on the lens holders are shifted in the longitudinal direction of the rod-shaped elastic members, so that the shafts parallel to the focus direction F and the tracking direction T are rotated. It is possible to realize an objective lens driving device having a stable displacement frequency characteristic without parasitic resonance while improving the restriction force against the rotational movement of the optical head and achieving a thin optical head as a whole.

[Brief description of drawings]

FIG. 1 is a front view of an objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an exploded perspective view showing a configuration of an objective lens driving device according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a configuration of an objective lens driving device according to a second embodiment of the present invention.

FIG. 5 is an exploded perspective view showing another configuration of the objective lens driving device in the second embodiment of the present invention.

FIG. 6 is a front view of a conventional objective lens driving device.

7 is a sectional view taken along line BB of FIG.

FIG. 8 is an exploded perspective view showing a configuration of a conventional objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3a, 3b Magnet 4a-4d Metal wire 5a, 5b Magnetic yoke 6a, 6b Tracking coil 7a, 7b Focusing coil 8 Fixing member 9 Base 10 Reflection mirror

Claims (3)

[Claims] 1. An objective lens of a device for optically writing or reading information on a disk-shaped recording medium, and a radial direction parallel to a recording medium surface of the disk-shaped recording medium,
The objective lens is held substantially at the center of a U-shaped lens holder, and a plurality of mechanisms are provided at both ends of the lens holder. An objective lens driving device comprising a permanent magnet for driving. 2. A lens holder having one end fixed to the lens holder and the other end fixed to a base, which are substantially parallel to each other.
2. The objective lens driving device according to claim 1, wherein the rod-shaped elastic members are supported by two or more rod-shaped elastic members, and the attachment positions of the rod-shaped elastic members to the lens holder are shifted in the longitudinal direction of the rod-shaped elastic members. 3. The wire diameter is changed so that the mounting positions of the respective rod-shaped elastic members on the base in the longitudinal direction are aligned, and the spring constants of the respective rod-shaped elastic members are the same. 2. The objective lens driving device according to 2.