JPS6254839A - Three-dimension optical pickup - Google Patents

Abstract

PURPOSE:To make a holder thin and to attain thin profile of a pickup by providing an air gap between the holder and its surrounding coil and inserting a part of the yoke to the air gap. CONSTITUTION:The coil 5 is wound around 4 projections 2a, 2b, 2c, 2d of the holder 2 to obtain a force driving the holder 2 in the optical axis direction and coils 7a, 7c and 7b, 7d two coils one set, wound flat and overlapped in two layers are sticked to symmetrical positions in the optical axis direction 3 of the upper face of the coil 5 to generate a force orthogonal in a plane vertical in the optical axis direction 3. Further, the holder 2 has the air gaps 8a, 8b, 8c, 8d penetrated in the optical axis direction 3. Moreover poles 9a'-9d' of yokes 9a-9d of a magnetic circuit 13 are inserted respectively to the air gaps 8a-9d of the holder 2 and the air gaps 8a-8d of the holder 2 have the size and arrangement without being in contact with the poles 9a'-9d' while being moved in 2 or 3 dimensions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical information reading device, and more particularly to a three-dimensional optical pickup used in an information reading device for an optical video disc.

[Technical background of the invention and its problems] In optical video discs, which have been put into practical use in recent years, laser light is applied to information stored in the form of bits on the disc to extract it as a signal. Focusing controls the laser beam to focus on the bit surface by moving the lens to follow the surface runout, tracking moves the beam in the radial direction of the disk so that it follows the track runout and always traces a single track, and A servo system in three orthogonal axes directions is required for tangential correction (jar correction) to absorb speed errors caused by eccentricity of the disk.

Therefore, an objective lens driving device for a three-axis optical pickup as shown in FIG. 4 has been proposed.

In FIG. 4, a voice coil motor 21 generates a force that drives the entire pickup in the optical axis direction, and a voice coil motor 22 generates a force that drives the objective lens blades in mutually orthogonal directions in a plane perpendicular to the optical axis direction. , and four combinations of coil power and magnetic circuit 25 are used. In this configuration, the voice coil motor 2 for driving the 7 orcasing
Since the voice coil motor 1 and the voice coil motor 22 for tracking drive and tangential drive are separate, the structure is complicated and the whole is heavy and large. Moreover,
The procedure for assembling the drive unit including the four sets of voice coil motors 22 that generate forces orthogonal to each other in a plane perpendicular to the optical axis direction is to insert the magnetic circuit 25 into the coil U from all sides one by one. There were many steps and positioning was difficult.

For this purpose, for example, a multidimensional directional drive device has been proposed in Japanese Patent Laid-Open No. 60-61926.

As shown in FIGS. 5 and 6, a plate 31 and a pole piece 21 are fixed to the magnetized surfaces of a permanent magnet 300 magnetized in two directions, forming two magnetic gaps. . A cylindrical coil wound around the outer circumference of the bobbin 36 (a semi-cylindrical oblate rectangular coil fixed to the outer circumference in a cylindrical shape) is further fixed to the outer circumference in a cylindrical shape in this magnetic gap. Semi-cylindrical flat rectangular coil 35
is located.

Here, when current is passed through the cylindrical coil 33, the objective lens 37 is driven in two directions, that is, in the focusing direction, due to interaction with the air gap magnetic flux, and when current is passed through the rectangular coils 34 and 35, the interaction with the air gap magnetic flux is driven. By this action, it is possible to drive in the tracking direction and the tangential direction, which are perpendicular to the two directions, respectively.

However, if the yoke or magnet that generates magnetic flux is smaller than the drive coil, the range in which the magnetic flux density distribution is constant is narrow, and when the objective lens is displaced, the drive coil may protrude from the constant range of magnetic flux density distribution. Alternatively, there is a drawback that the center of gravity of the movable part including the objective lens and the holder that holds it is shifted from the center position where the force of the drive coil is applied, and the optical axis is tilted. Furthermore, if the holder holding the objective lens is long in the optical axis direction, it will be unstable and prone to tilting, and even if it is slightly tilted, incident light to the objective lens will be blocked.

When the optical axis is tilted in this manner, the optical paths of incident light and reflected light from the disk change, making it impossible to accurately extract control signals for focusing, tracking, etc.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a three-dimensional optical pickup that is thin, has a simple structure, is easy to assemble, and does not cause the optical axis of the objective lens to tilt.

[Summary of the invention]

In order to achieve the above object, the present invention includes an objective lens, a holder that holds the objective lens, an elastic body that supports the holder on a fixed part consisting of a base, and an elastic body that is wound around the holder and that is attached to the holder. a first coil for driving the holder in the optical axis direction of the objective lens; and a first coil wound flatly and fixed to the first coil for driving the holder in a direction perpendicular to the optical axis direction of the objective lens. 2 coil, holder and 1st coil.
A yoke is provided between the coils and has a gap extending in the optical axis direction of the objective lens, and a yoke having opposing surfaces and having one surface inserted into the gap. Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a partially cutaway perspective view of the entire three-dimensional optical pickup of the present invention, FIG. 2 is a perspective view showing the positional relationship of the holder, coil, and magnetic circuit according to the present invention, and FIG. ,
FIG. 1 is a perspective view showing a magnetic circuit according to the present invention.

The objective lens 1 is held by a holder 2, and this holder 2 has four protrusions 2a arranged at approximately 45 degrees with respect to two axial directions 4a and 4b orthogonal to each other in a plane perpendicular to the optical axis direction 3.
12b, 2C, 2d, and these projections 2a
, 2b, 2c, and 2d are point symmetrical with respect to the optical axis direction.

Further, a coil 5 for obtaining a force for driving the holder 2 in the optical axis direction 3 is formed by four protrusions 2a and 2b of the holder 2.

2C92d, and further in the optical axis direction 3
A set of two coils 7a that are wound flat and stacked in two layers to generate forces orthogonal to each other in a plane perpendicular to
, 7c, 7b, and 7d are the optical axis direction 3 on the upper surface of the coil 5.
It is glued in a symmetrical position.

Further, the holder 2 has a cavity 8 a penetrating in the optical axis direction 3.
+ 8 b, 8 c, 8 d.

The magnet 10 is fixed to the yoke 9 and is magnetized in a direction perpendicular to the opposing surface of the yoke 9 (in the direction of an arrow 11), thereby forming a closed magnetic field with a magnetic gap 12 between the yoke 9 and the magnet 10. A circuit 13 is formed.

Four magnetic circuits 13 are arranged around the holder 2 at symmetrical positions with respect to the optical axis direction 3, and constitute a negative set of magnetic circuit sections.

The magnetic circuit 1 is installed in the gaps 8a, 8b, 8C, and 8d of the holder 2.
3 yoke 9a, 9b, 9c, 9d bow/L/9
a', 9b', 9c', and 9d' are inserted into the gaps 8a and 8b of the holder 2, respectively.

8c, 8d are balls 9a', 9b', 9c',
The dimensions and arrangement are such that the holder 2 can be moved in two or three dimensions without touching 9d'. Such dimensions,
A coil 5 for obtaining force in the optical axis direction 3 by arrangement;
Coils 7L/7a, 7bH7Cr7d for generating forces orthogonal to each other in a plane perpendicular to the optical axis direction 3 are connected to the magnetic gaps 12a, 12b, 12c of the magnetic circuit 1-3.
12d, respectively.

And magnetic gaps 12a, 12b, 12c, 12d
A force for moving the holder 2 in the optical axis direction 3 can be obtained by applying a predetermined current to the coil 5 disposed therein.

4a that are perpendicular to each other in a plane perpendicular to the optical axis direction 3;

Coils 7a and 7b for generating force in the direction 4b.

7c and 7d are each composed of two flatly wound coils stacked in two layers.
For one of the coils 7a, the objective lens 1
The movable range is such that only one of the two pairs of opposing coil parts having coil parts parallel to the optical axis direction 3 of the holder 2 is always inside the magnetic gap 12 no matter where the holder 2 is located within the movable range. has been decided. This is all coils 7a and 7b.

This is common to 7c and 7d.

In addition, a coil 7a arranged in one magnetic gap 12a and a coil 7a arranged in a set of two and a coil 7a located in a symmetrical position with respect to the optical axis direction 3 and in a plane perpendicular to the optical axis direction 4a.
The first four coils, including the two coils 7C on the
A set of four coils 7b and 7d, one set of two coils located on the direction 4b orthogonal to the first set and symmetrical with respect to the optical axis direction 3, are added to the second set. Set. Servo signals in one axis direction (for example, in the 4b direction) are simultaneously applied to 7a and 7C (first cellar), and the second
For example, 4a perpendicular to the 4b direction to 7b and 7d
Simultaneously energize the servo signals in each direction, and the optical axis direction 3
It is possible to independently generate forces that drive the holder 2 in directions 4a and 4b that are orthogonal to each other in a plane perpendicular to .

These actions provide a force that drives the holder 2 three-dimensionally.

Next, the damper 14 is made of an elastic body such as rubber, and has a substantially rectangular cross-sectional shape with the long side in the optical axis direction 3, and an L-shape in which the center axes of the cross-section are substantially equal lengths and orthogonal to each other. The sides are protrusions 2a and 2b of the holder 2, respectively.

2c and 2cl, and have a shape that is line symmetrical with respect to two axial directions 4a and 4b that are orthogonal to each other in a plane perpendicular to the optical axis direction 3.

Two dampers 14 are vertically symmetrically bonded to the holder 2, and their ends are fixed to a frame 15 to support the holder 2 so as to be movable in three dimensions.

In the three-dimensional optical pickup configured as described above, the coil 5 is wound around the holder 2, the coils 7a, 7b, 7c, and 'yd are attached around it, and a gap is formed between these coils and the holder 20. By providing 8a, 8b, 8C, and 8d, coils can be placed all around the holder 2, and the holder 2 can be made thinner. Also, voids sa and sb penetrate in the optical axis direction 3.

baud A/9a' that constitutes the magnetic circuit 13 on gc, 8d
, 9b', 9c'.

By inserting 9d', coil 5 and coil 7a
, 7b, 7c, and 7d can form a larger magnetic gap. In this case, the size of the magnet 10 is the size of the intersection of the coil 5 and the coils 7a, 7b, 7c, and 7d, plus the distance of the movable range in the focusing direction, tracking direction, and tangential direction. If the holder 2 is displaced to any position within its movable range, the coils 5 and 7a, 7b,
In the case of 7c and 7d, the magnetic flux density is within a constant magnetic gap, and the optical axis is not tilted.

Furthermore, the center of gravity of the holder 2 in the optical axis direction 3 and the center of the force generated by the coils 5 and 7a, 7b, 7c, and 7d are approximately in the same plane, which means that the holder 2 can be positioned at any position within its movable range. This enables stable control at all times, even when the object is displaced.

In addition, the holder 2 is formed into a diagonal shape, but this is by cutting the four corners of the square holder 2, and in addition to providing voids sa+sb, sc, and sci, it is possible to reduce the weight of the holder. This is to prevent the two dampers 14, which are vertically symmetrically bonded to the holder 2, from coming into contact with the holder 2 when the objective lens 1 is displaced in the focus direction.

The three-dimensional optical pickup of the present invention has yokes 9a, 9b, 9C, and 9d of the magnetic circuit 13, which are positioned on the base 16 in advance in accordance with the positions of the gaps 8a, 8b, 8c, and 8d of the holder 2. The damper 14 made of an elastic material such as rubber and the holder 2 are attached to the frame 1.
It can be more easily assembled by inserting it into a predetermined position together with 5.

Although one embodiment of the present invention has been described above, the present invention can be modified in various ways without changing the gist thereof.

For example, the coil 5 is wound around the holder 2, and the coil 7 is wound flatly on top of the holder 2.
Although the coils 7a, 7b, 7c, and 7d are bonded together, the coils 7a, 7b, 7C, and 7d may be placed inside the coil 5. Further, the coil 5 is wound flatly, and the protrusion 2a of the holder 2 is closed.

2b, 2c, and 2d can also be bonded together to obtain the same effect as when wrapped around the holder 2. Note that although the coils 7a, 7b, 7C, and 7d are shown as being wound flat and stacked in two layers, the
It may be laminated in layers or three or more layers.

Further, the shape and cross-sectional shape of the damper 14 can be variously modified, for example, the cross-sectional shape may be approximately square or approximately circular. Note that by using silicone rubber as a main component of the damper 14, changes in characteristics with respect to temperature changes are small and stable recording and reproduction can be performed. Further, a metal plate (not shown) may be bonded in advance to the joint part of the damper 14 and the holder 2. By doing so, the damper 14 and the holder 2 are bonded to each other with metal, and the bonding becomes easy. I can do it. Further, a frame 1 for fixing the damper 14 and the metal plate or the damper 14 and the damper 14 is provided.
5 may be integrated and hidden using outsert technology.

〔Effect of the invention〕

As described in detail above, according to the present invention, a gap is provided between the holder and the surrounding coil, and a part of the yoke is inserted into this gap, so the holder can be made thinner and the pickup It is possible to obtain a three-dimensional optical pickup that is thinner, easier to assemble, and does not tilt the optical axis of the objective lens.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of the three-dimensional optical pickup of the present invention, and FIG. 2 is a holder according to the present invention.
FIG. 3 is a perspective view showing the positional relationship between the coil and the magnetic circuit. FIG. 4 is a perspective view showing the magnetic circuit according to the present invention.
FIG. 5 is a perspective view showing a second conventional example, and FIG. 6 is an explanatory diagram illustrating the configuration of a coil in the second conventional example. 1... Objective lens 2... Holder 5 - Coil (first coil) 7a, 7b, 7c, 7d - Coil (second coil) 8a, 8b, 8C, 8d... Gap 9a, 9b,
9c, 9d-: I-ri 9a', 9b', 9c', 9d'
...-Balls (part of yoke) 10a, 10b, 10c
, 10d---Magnet 13 Magnetic circuit 14
・Danno < (Elastic Body) Agent Patent Attorney Nori Chika
Yudo Takehana Kikuo Figure 1 Figure 5 (Figure 6)

Claims (2)

[Claims] (1) An objective lens, a holder that holds this objective lens, an elastic body that supports this holder on a fixed part consisting of a base, and an elastic body that is wound around the holder and that holds the holder along the optical axis of the objective lens. a first coil for driving in the direction;
a second coil wound in a flat layer and fixed to the first coil for driving the holder in a direction perpendicular to the optical axis direction of the objective lens; and between the holder and the first coil. a yoke having opposing surfaces, one surface of which is inserted into the void, and a magnet fixed to the other surface of the yoke; A three-dimensional optical pickup characterized by comprising: (2) No matter where the holder is in its movable range, the intersecting portion of the first coil and the second coil will fit within the magnetic gap of the magnetic circuit consisting of the yoke and the magnet. The magnetic gap is formed to be larger than the sum of the movable distance of the holder and the intersection of the first coil and the second coil. Dimensional optical pickup.