JPH0739058Y2 - Pickup device in optical information recording / reproducing apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pickup device in an optical information recording / reproducing apparatus.

BACKGROUND ART A disc such as a video disc or a digital audio disc, which is an information recording medium, records the information signal by forming fine pits (dents) corresponding to the information signal as spiral tracks on the surface thereof. is there. When reading the information signal thus recorded, spot light is irradiated onto the track to convert the change in reflected light depending on the presence or absence of a pit into an electric signal and reproduce it as the original information signal.

In this reproduction, the irradiation light must be accurately focused on the recording surface of the disc. Therefore, an objective lens for focusing the irradiation light on the recording surface is provided in the optical axis direction (focusing direction) of the objective lens. It is necessary to control the position (focus servo) in. Further, since the irradiation light must accurately follow the recording track, it is also necessary to perform position control (tracking servo) of the irradiation light in the direction (tracking direction) perpendicular to the optical axis direction.

FIG. 5 and FIG. 6 show the essential parts of the already developed pickup device.

As shown in FIGS. 5 and 6, the objective lens 1 is fitted in a cylindrical portion 2 a protruding from the holder 2.
The objective lens 1 is movable in two directions of an optical axis direction of the objective lens, that is, a focus direction Z and a tracking direction X perpendicular to the optical axis direction by a support mechanism including the holder (not shown except the holder 2), and The optical axis of the objective lens is supported so as to be perpendicular to the recording surface of the information recording disk 3. The objective lens 1 is for focusing the irradiation light emitted from the laser diode as spot light on the recording surface of the information recording disk 3 which is a recording medium.

A coil 5 is wound around the outer periphery of the bobbin portion 2b formed at the lower end of the holder 2 so that the coil center axis is parallel to the focus direction Z. Four coils 6 are fixed to the outer surface of the coil 5 so that the central axis of the coil is perpendicular to the focus direction Z. Further, a pair of magnetic circuits 9 including a magnet 7 and a yoke 8 is provided, and the coils 5 and 6 are inserted into the magnetic gaps of the both magnetic circuits. As is clear from FIG.
Magnetic fluxes interlinking the coils 5 and 6 are emitted from both magnetic circuits 9.

The coils 5 and 7 and each magnetic circuit 9 constitute a driving means for driving the objective lens 1. Coil 5
The objective lens 1 is driven by supplying the currents to 6 and 6, and the focus servo and the tracking servo are performed.

In the pickup device having the above-described structure, the magnetic circuit 9 must be relatively large in order to obtain the magnetic flux density required for driving the objective lens 1, and the size of the entire pickup device cannot be reduced. It wasn't always easy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to provide a pickup device that can be easily downsized.

The pickup device according to the present invention includes an objective lens for irradiating the information recording surface of the recording medium with information reading light, and a holder for carrying the objective lens, and movably supports the objective lens in the focus direction and the tracking direction. A support mechanism, a yoke having a portion formed by protruding a pair of side wall pieces into a substantially concave shape, a magnet inscribed in one of the pair of side wall pieces of the yoke, and a pair of side wall pieces of the yoke. A pickup device in an optical information recording / reproducing apparatus including a side wall piece opposite to one side, a driving coil positioned in a gap formed by the magnet, and a cover member surrounding the objective lens and the support mechanism. And at least a part of the cover member is made of a magnetic material, and the magnetic property of the cover member is It is characterized in that the portion formed by the body abuts the upper end of the opening of the yoke to close the opening.

Embodiment Hereinafter, a pickup device as an embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the objective lens 21 is fitted in a holder 22 formed in a rectangular parallelepiped shape. As shown in FIG. 2, the holder 22 includes two and four leaf springs 24 and 25, respectively, and a pair of relay members 26 interposed between the leaf springs. Attached to the base member 28. The objective lens 21 is for focusing the irradiation light emitted from the laser diode (not shown) on the recording surface of the information recording disk (not shown) as a recording medium as fine spot light. Further, the pair of relay members 26 are connected by a vibration isolator 27 made of rubber or the like.

Of the leaf springs described above, two leaf springs 24 are objective lenses.
The optical axis direction of 21, that is, the focus direction Z and a plane including the two directions of the tracking direction X which is perpendicular to the focus direction Z, extend substantially at right angles, and are arranged apart from each other in the tracking direction X, and are arranged on the base member 28. Projecting support protrusion
It is attached in a cantilever shape to 28a and is flexible in the tracking direction X. Further, the other four leaf springs 25 also extend substantially parallel to the leaf springs 24 and are arranged so as to be separated by two in the focus direction Z, and one end of the relay member 26 is provided at the free end of the leaf spring 24. Are connected through. This 4
The leaf spring 25 is flexible in the focus direction Z and supports the holder 22 at the other end. As is particularly clear from FIG. 2, the holder 22 is formed with two protrusions 22a that relatively project in the tracking direction X,
The other ends of the four leaf springs 25 are joined to the protrusions 22a.

The holder 22, the leaf springs 24 and 25, the relay member 26, and the vibration isolator 27 described above.
The base member 28 supports the objective lens 21 so that it can move in the focus direction Z and the tracking direction X, and the optical axis of the objective lens is perpendicular to the recording surface of the information recording disk (described above). A support mechanism is configured.

As shown in FIGS. 1 and 3, of the six faces of the holder 22 formed in a rectangular parallelepiped shape, two side faces parallel to the faces including the focus direction Z and the tracking direction X are wound in a rectangular tube shape. A pair of coils 30 are attached such that the central axes of the coils are parallel to the focus direction Z.
Further, a total of four coils 31 are fixed to each outer surface of both coils 30, one pair each so that the coil center axis is perpendicular to the focus direction Z. The coil 31
Are accommodated within the range of the outer diameter of the coil 30 in the focus direction Z.

A magnetic circuit including two magnets 33, two yokes 34, and two yoke plates 35 is provided on the base member 28, and magnetic fluxes interlinking with the coils 30 and 31 are generated from the magnetic circuits. ing. As is particularly clear from FIG. 3, the yoke 34 and the yoke plate 35 are formed integrally with the base member 28.

Further, the yoke plate 35 is inserted into the coil 30 wound in a rectangular tube shape.

As shown in FIGS. 3 and 4, a cover member 37 is provided which surrounds the objective lens 21 and the above-mentioned support mechanism (comprising leaf springs 24, 25, etc.). The cover member 37 is made of a magnetic material, and the inner surface of the cover member has a magnet 33, a yoke 34, and a yoke plate, as is apparent from FIG.
By contacting the upper end of 35, the cover member becomes a part of the magnetic circuit including the magnet and the like. As a result, the magnetic circuit is formed in a cylindrical shape with the central axis parallel to the tracking direction X and surrounding the coils 30 and 31.

The coils 30 and 31 and the magnetic circuit described above constitute a driving unit that drives the objective lens 21.

As shown in FIG. 1, a total of 6 leaf springs 24 are provided.
The numbers 25 and 25 are arranged in the tracking direction X by half, that is, by three, and are separated by the distance L. The coils 30 and 31 and the magnetic circuit described above are arranged so as to be sandwiched by the leaf springs separated by half as described above.

In the pickup device described above, a driving force is generated by supplying a current to the coils 30 and 31, and accordingly, the leaf springs 24 and 25 are appropriately bent to move the objective lens 21 in the tracking direction X and the focus direction Z. It can be moved.

In the pickup device described above, the cover member
Although the entire 37 is formed of a magnetic material, the present invention is not limited to this configuration, and only the portion of the cover member that constitutes the magnetic circuit together with the magnet 33 and the like is formed of a magnetic material.
The other portion may be formed of resin or the like. In addition, since at least a part of the cover member 37 is also used as a part of the magnetic circuit as described above, the number of parts is reduced, and it is easy to reduce the size and cost of the pickup.

Effects of the Invention As described in detail above, in the pickup device of the optical information recording / reproducing apparatus according to the present invention, the pair of side wall pieces are projected to close the opening of the yoke which is formed in a substantially concave shape, and the magnet is provided therein. Further, since the drive coil is arranged, the magnetic flux density in the yoke, that is, the magnetic flux density interlinking with the drive coil is increased, and the device can be downsized when the magnetic flux density required for driving the objective lens is constant. .

Further, in the present invention, at least a part of the cover member is formed of a magnetic material, and that part is configured to close the opening of the yoke. Therefore, the opening of the yoke is closed at the same time by attaching the cover member. Therefore, in addition to the effects described above, it is possible to simplify the assembly of the pickup and reduce the thickness of the device.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a pickup device according to the present invention,
FIG. 2 is a partial detailed view of the pickup device, FIG. 3 is a side sectional view of the main portion, FIG. 4 is a perspective view showing the main portion and a cover member surrounding the main portion, FIGS. 5 and 6. FIG. 4 is a diagram for explaining a pickup device that has already been developed. 21 …… Objective lens 22 …… Holder 24,25 …… Flat spring 30,31 …… Coil 33 …… Magnet 34 …… Yoke 35 …… Yoke plate 37 …… Cover member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-91540 (JP, A) JP-A-59-221840 (JP, A) JP-A-59-68841 (JP, A) Actual development Sho-58- 118541 (JP, U) Actual development Sho 58-155638 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A support mechanism including an objective lens for irradiating information reading light on an information recording surface of a recording medium, and a holder for supporting the objective lens so as to movably support the objective lens in a focus direction and a tracking direction. A yoke having a pair of side wall pieces protruding into a substantially concave shape; a magnet inscribed in one of the pair of side wall pieces of the yoke; and one of the pair of side wall pieces of the yoke. A pickup device in an optical information recording / reproducing apparatus including a driving coil positioned in a gap formed by the other side wall piece and a magnet facing each other, and a cover member surrounding the objective lens and the support mechanism. And at least a part of the cover member is made of a magnetic material, and the cover member is made of a magnetic material. There pickup device in an optical information recording and reproducing apparatus characterized by closing the opening in contact with the opening upper end of the yoke.