JPH07334855A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To provide an objective lens driving device having high sensitivity which an inner yoke has, and capable of being miniaturized while having a constitution in which driving coils are directly wound around a holder. CONSTITUTION:A holder 2 is held between two tracking coils 4a and 4b, the lower side part of a focusing coil 3 is thinned, and the base part of a yoke 10 is thinned in the range where the holder is projected from above except the part from an outer yoke 11 to an inner yoke 12. Thus, one part of tracking coils is made possible to move from the upper plane of the base part of a yoke base downward, so that an optical pickup including an objective lens can be miniaturized while remaining the advantage of high sensitivity which the inner yoke has.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used in an optical disc reproducing device for recording / reproducing a disc by projecting a laser beam onto the disc.

[0002]

2. Description of the Related Art In recent years, in order to reduce the production cost of an objective lens driving device, a drive coil is directly wound around a holder for holding the objective lens, but it is difficult to downsize an optical pickup. There's a problem. On the other hand, for the purpose of downsizing the optical pickup, there is also a structure in which the completed air-core coil is attached to the holder that holds the objective lens to increase the degree of freedom in design, but this increases the production cost. There is a problem that is.

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

FIG. 3 shows the structure of a conventional objective lens driving device. In FIG. 3, reference numeral 21 is an objective lens, and 22 is a rectangular parallelepiped holder that holds the objective lens 21. The holder 22 has a focus coil 23 at a substantially central portion of a side surface about an axis perpendicular to the disc, and two tracking coils 24a, 2a on both sides of the objective lens 21 about an axis parallel to the disc.
4b is wound directly. 4 metal wire springs 25
Both ends of a, 25b, 25c, and 25d are soldered and fixed to two boards 26a and 26b fixed to the holder 22 and a board 27 on the fixed side.
Is cantilevered so as to be movable in two directions, a focus direction 35 and a tracking direction 36. On the substrates 26a and 26b, both ends of the focus coil 23 and tracking coils 24a and 24 which are two but continuous coil windings are provided.
Both ends of b are connected by soldering so that current can be supplied to the respective coils from the four metal wire springs 25a, 25b, 25c and 25d. 28
a, 28b, 28c, 28d are four metal wire springs 25
It is a viscoelastic tube arranged around a, 25b, 25c and 25d, and damps the primary resonance vibration of the movable part including the holder 22.

29 is called a suspension holder,
Four metal wire springs 25a, 25b, 25c, 25d,
It holds the viscoelastic tubes 28a, 28b, 28c, 28d in order to position them. 30 is
It is called a yoke base and has a base portion 30a having a surface parallel to the disc, and plate-like outer yokes 31a and 31b and an inner yoke which are arranged so as to be convex from the base portion 30a toward the disc side and perpendicular to the disc. 32a, 32b
And are integrally formed. The outer yokes 31a and 31b each have one magnet 33a, 3 magnetized in the thickness direction.
3b, the N poles are made to face each other and closely fixed, and further, the inner yoke 3
The magnets 33a and 33b are opposed to 2a and 32b to form a magnetic gap, a part of the focus coil 23 is inserted into the magnetic gap, and a part of the tracking coils 24a and 24b is opposed to the magnet. Thus, the movable part including the objective lens can be driven in two directions, that is, the focus direction 35 perpendicular to the disc and the tracking direction 36 parallel to the disc.
The suspension holder 29 and the fixed-side substrate 27 are fixed to the outer yoke 31 with mounting screws 34.

The conventional objective lens driving device having the above structure is
Since the inner yokes 32a and 32b are provided, the magnets 33a and 33b are opposed to the inner yokes 32a and 32b to form a magnetic gap, so that the magnetic flux is easily concentrated, and the magnetic flux of the focus coil 23 is easily concentrated in the magnetic gap. The tracking coil 24 is inserted in the magnet by inserting a part thereof.
By facing a part of a and 24b, high efficiency,
The movable part including the objective lens can be driven in two directions: a focus direction 35 perpendicular to the disc and a tracking direction 36 parallel to the disc.

[0007]

However, in the conventional objective lens driving device as described above, when the holder 22 is driven downward, the tracking coils 24a and 24b.
Since the movable range is limited by the contact between the lower surface of and the upper surface of the base portion 30a of the yoke base 30, if the necessary movable range in the focus direction 35 is secured, the total height of the optical pickup including the objective lens driving device cannot be reduced, There is a problem in that it is difficult to adopt for downsizing.

In view of the above-mentioned conventional problems, the present invention allows the drive coil to be directly wound around the holder holding the objective lens and the magnetic gap to be formed by facing the magnet to the inner yoke in order to reduce the production cost. It is possible to reduce the total height of the optical pickup including the objective lens driving device while keeping the advantage of the conventional objective lens driving device that the magnetic flux is concentrated and can be driven with high efficiency. It is made for the purpose of providing.

[0009]

In order to solve the above problems, in the objective lens driving device of the present invention, the holder for holding the objective lens is sandwiched between two tracking coils and the lower part of the focus coil is removed. The base portion of the yoke base is meat-removed by providing a recess or an opening in a range in which the holder is projected from the upper side, except between the outer yoke and the inner yoke. As a result, when the holder is driven downward, a part of the tracking coil wound around the holder can be moved downward from the upper surface of the base portion of the yoke base.

[0010]

According to the present invention, when the holder for holding the objective lens is driven downward by the above structure, a part of the tracking coil wound around the holder is moved downward from the upper surface of the base portion of the yoke base. Since it is movable, the drive coil can be wound directly around the holder that holds the objective lens in order to reduce the production cost, and the magnet is opposed to the inner yoke to form a magnetic gap to concentrate the magnetic flux and drive it with high efficiency. While maintaining the advantage of the conventional objective lens driving device, the overall height of the optical pickup including the objective lens driving device can be reduced, and the optical pickup can be downsized.

[0011]

EXAMPLES Examples of the objective lens driving device of the present invention will be described in detail below with reference to FIGS.

FIG. 1 shows the structure of an objective lens driving device according to the first embodiment of the present invention.

In FIG. 1, 1 is an objective lens,
Reference numeral 2 denotes a rectangular parallelepiped holder that holds the objective lens 1. The holder 2 has a focus coil 3 in a substantially central portion of a side surface around an axis perpendicular to the disc, and two tracking coils 4a and 4b around the axis parallel to the disc and on both sides of the objective lens 1. However, it is wound directly. The holder 2 is formed of a heat resistant resin such as liquid crystal polymer, and 6a, 6b, 6c and 6d are bosses formed on the holder 2. This boss 6a, 6
b, 6c and 6d have two ends of the focus coil 3 and 2
After being wound around both ends of the tracking coil 4a, 4b which is a continuous coil winding, it is fixed by soldering with a solder dip. Further, attach both ends of the four metal wire springs 5a, 5b, 5c and 5d to the holder 2
Soldered and fixed to the bosses 6a, 6b, 6c, and 6d formed on the fixed side and the fixed side substrate 7, and as a result, the holder 2 is
It is cantilevered so as to be movable in two directions: the focus direction 15 and the tracking direction 16. Furthermore, this boss 6a, 6
b, 6c and 6d have two ends of the focus coil 3 and 2
However, since both ends of the tracking coils 4a and 4b, which are continuous coil windings, are connected by soldering, current is supplied to each coil from the four metal wire springs 5a, 5b, 5c, and 5d. it can.

Reference numeral 9 is called a suspension holder, and 4
The metal wire springs 5a, 5b, 5c and 5d of the book are held to determine their positions. 8a and 8b are silicon-based gels, which are filled in a container provided in the suspension holder 9 and then gelated by irradiation of ultraviolet rays. The movements of the metal wire springs 5a, 5b, 5c and 5d are damped. By doing so, the primary resonance vibration of the movable portion including the holder 2 is damped. Reference numeral 10 is called a yoke base and has a base portion 10 having a surface parallel to the disc.
a, plate-like outer yokes 11a and 11b, and inner yokes 12a and 12b, which are arranged so as to project from the base portion 10a toward the disk side and are arranged perpendicular to the disk, are integrally formed. Magnets 13a and 13b magnetized in the thickness direction are respectively attached to the outer yokes 11a and 11b so that the N poles face each other and closely adhere to each other, and further the inner yokes 12a and 12b.
The magnets 13a and 13b are opposed to each other to form a magnetic gap, a part of the focus coil 3 is inserted into the magnetic gap, and the tracking coil 4a is inserted into the magnet.
By making a part of 4b face each other, the movable part including the objective lens can be driven in two directions of a focus direction 15 perpendicular to the disc and a tracking direction 16 parallel to the disc. The suspension holder 9 and the fixed-side substrate 7 are attached by the mounting screw 14.
It is fixed to the outer yoke 11.

Here, the holder 2 is sandwiched between the two tracking coils 4a and 4b and has two places 2a and 2b (2b is the opposite side of 2a, not shown) of the lower part of the focus coil 3. The meat is removed, and the yoke base 10
The base portion 10a of each of the bases 10b and 10c extends from the outer yokes 11a and 11b to the inner yokes 12a and 12b, respectively.
Except for, the holder 2 is provided with a recess or an opening in the range where the holder 2 is projected from the upper side to remove the meat.

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

First, the holder 2 is sandwiched between two tracking coils 4a and 4b, and the two lower portions 2a and 2b of the focus coil 3 are removed, and the base portion 10a of the yoke base 10 is Outer yoke 11a, 11
10b between the inner yoke 12a and the inner yoke 12b
Except for b and 10c, since the holder 2 is recessed or opened in a range where the holder 2 is projected from the upper side,
When the holder that holds the objective lens is driven downwards,
Tracking coils 4a and 4b wound around the holder 2
Is movable downward from the upper surface of the base portion 10a of the yoke base 10. Therefore, like the conventional example,
It is not necessary to previously provide a gap for securing the movable range in the focus direction between the base portion 30a of the yoke base 30 and the holder 22, and accordingly, the overall height of the objective lens driving device can be reduced, and the light including the objective lens driving device can be reduced. The pickup can be miniaturized.

Further, the outer yoke 1 which is the magnetic path of the magnetic circuit.
Since 10b and 10c are left without being thinned between the 1a and 11b and the inner yokes 12a and 12b, the magnets 13a and 13b are opposed to the inner yokes 12a and 12b to form a magnetic gap to concentrate the magnetic flux. It is possible to insert a part of the focus coil 3 into this magnetic gap,
By making a part of the tracking coils 4a and 4b face a and 13b, the movable portion including the objective lens 1 can be moved with high efficiency in the focus direction 1 perpendicular to the disc.
5 and tracking direction 1 parallel to the disc
6 can be driven in two directions. Moreover, since the drive coil is wound directly around the holder that holds the objective lens, the production cost can be reduced.

Further, in the present embodiment, the yoke base 1
By removing the portions 10d, 10e, 10f, and 10g of the lower portions of the magnets 13a and 13b of the base portion 10a of 0, both sides of the magnets 13a and 13b magnetized in the thickness direction are magnetically short-circuited. Can be reduced, and the movable part including the objective lens 1 can be driven more efficiently.

Further, in this embodiment, the holder 2 is
Molded with heat-resistant resin such as liquid crystal polymer, bosses 6a, 6
After forming b, 6c, and 6d and winding both ends of the focus coil 3 and both ends of the tracking coils 4a and 4b, which are two but continuous coil windings, they are fixed by soldering with a solder dip. At the same time, one of the four metal wire springs 5a, 5b, 5c, and 5d is fixed by soldering, so that a relay member such as a board, which is conventionally required, is unnecessary.

FIG. 2 is a sectional view showing a state in which the objective lens driving device according to the first embodiment of the present invention is attached to an optical pickup.

In FIG. 2, 17 is a base of an optical pickup, 18 is a mirror, 19 is a hologram laser unit, and a semiconductor laser, a light receiving element and a hologram element are integrally contained in one package. . Two
0 indicates the light emitted from the hologram laser unit. According to this cross-sectional view, the lower surface of the holder 2 exceeds the lower surface of the base portion 10a of the yoke base 10 and the emitted light 2
It can be seen that the optical pickup including the objective lens driving device can be miniaturized while maintaining the movable range in the focus direction, while it can be displaced downward until reaching 0.

[0023]

As described above, according to the present invention, the holder for holding the objective lens is sandwiched between the two tracking coils and the lower portion of the focus coil is removed.
The base portion of the yoke base is provided with a recess or an opening in the range in which the holder is projected from the upper side, except between the outer yoke and the inner yoke. When driven downward, a part of the tracking coil wound around the holder becomes
Since it is movable below the upper surface of the base portion of the yoke base, it is not necessary to previously provide a gap for securing the movable range in the focus direction between the base portion of the yoke base and the holder as in the conventional example. Accordingly, the total height of the objective lens driving device can be reduced, and the optical pickup including the objective lens driving device can be downsized.

Furthermore, since the space between the outer yoke and the inner yoke, which is the magnetic path of the magnetic circuit, is not thinned, the magnet is opposed to the inner yoke to form a magnetic gap so that the magnetic flux can be concentrated. , By inserting a part of the focus coil into this magnetic gap and making a part of the tracking coil face the magnet, the movable part including the objective lens can be moved with high efficiency in the focus direction perpendicular to the disc. 2 in the tracking direction parallel to the disc
Can be driven in any direction. Moreover, since the drive coil is wound directly around the holder that holds the objective lens, the production cost can be reduced.

Furthermore, by removing a part of the lower portion of the magnet of the base portion of the yoke base, magnetic short-circuiting on both sides of the magnet magnetized in the thickness direction can be reduced, and the efficiency can be further improved. It is possible to realize an objective lens driving device having excellent characteristics such as being able to drive a movable part including an objective lens.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of an objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a state in which the objective lens driving device according to the first embodiment of the present invention is attached to an optical pickup.

FIG. 3 is an exploded perspective view showing a configuration of a conventional objective lens driving device.

[Explanation of symbols]

 1 Objective Lens 2 Holder 3 Focus Coil 4 Tracking Coil 5 Metal Wire Spring 6 Boss 7 Substrate on Fixed Side 8 Silicon Gel 9 Suspension Holder 10 Yoke Base 11 Outer Yoke 12 Inner Yoke 13 Magnet 14 Mounting Screw 15 Focus Direction 16 Tracking Direction

Claims (2)

[Claims] 1. An objective lens, a rectangular parallelepiped holder for holding the objective lens, a focus coil wound around a center of a side surface of the holder about an axis perpendicular to the disc, and a focus coil parallel to the disc. A movable part consisting of two tracking coils wound around the holder around the axis and arranged on both sides of the objective lens, is integrally supported by a supporting member, and has a base part having a surface parallel to the disc. A yoke base is formed by integrally forming four plate-shaped yokes, which are arranged so as to project from the base portion toward the disc side and perpendicularly to the disc, and the two outer yokes (outer yoke One magnet is closely attached to each of the four yokes and the two inner magnets of the four yokes are opposed to each other to form a magnetic gap. By forming a part of the focus coil in the magnetic gap and making a part of the tracking coil face the magnet, the movable part including the objective lens is focused in a direction perpendicular to the disc. Direction and a tracking direction parallel to the disc, the objective lens driving device is capable of being driven in two directions. The holder is sandwiched between the two tracking coils, and a portion below the focus coil is provided. The meat is removed and the base of the yoke base is
Except for each space from the outer yoke to the inner yoke, the holder is provided with a recess or an opening in a range projected from the upper side, and as a result, when the holder is driven downward, An objective lens driving device, wherein a part of the tracking coil is movable below an upper surface of a base portion of the yoke base. 2. The objective lens driving device according to claim 1, wherein a part of a lower portion of the magnet of the base portion of the yoke base is removed.