JP2571210B2 - Optical head device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device, and more particularly to a support shaft fixed to a base and provided at least slidably and rotatable with respect to the support shaft. The present invention relates to an optical head device including an optical system holder, a sliding coil and a rotating coil fixed to the optical system holder, and a magnetic circuit that forms a magnetic field across these coils.

[Prior Art] Conventionally, an optical head device has a base and an optical system driving device provided thereon. Hereinafter, this optical system driving device will be described by taking an objective lens driving device as an example.

FIG. 5 is a perspective view of a first example of a conventional objective lens driving device.

As shown in FIG. 5, the objective lens holder 28 is inserted through a bearing into a support shaft 26 fixed to the base 21 by press fitting or the like. A weight 29 having substantially the same weight as the objective lens 23 is attached. Further, a neutral point holding member (not shown) is attached below the weight 29. A sliding coil (hereinafter, referred to as a focusing coil) 24 is wound around the outer periphery of the objective lens holder 28, and a rotating coil (hereinafter, referred to as a tracking coil) is provided on the focusing coil 24. 25b) and a tracking coil 2 (not shown)
5a (the support shaft 26 is mounted at a position opposite to the tracking coil 25b).
Permanent focusing magnets 27a and 27b are provided near the inner peripheral portion of the objective lens holder 28 so as to face the focusing coil 24.
Are fixed to the base 21, and yokes 30a, 31b forming opposing magnetic poles of the focusing permanent magnets 27a, 27b are fixed near the outer peripheral portion. Further, tracking permanent magnets 22a and 22b are fixed to the base 21 near the outer peripheral portion of the objective lens holder 28 so as to face the tracking coils 25a and 25b. Due to the electromagnetic force generated by the current flowing through the focusing coil 24 and the tracking coils 25a and 25b and the magnetic field formed for each coil, the objective lens holder 28 slides up and down about the support shaft 26, It is rotated left and right.

FIG. 6 is a sectional view of a main part of a second example of the conventional objective lens driving device. The same members as those in the first example shown in FIG. 5 are denoted by the same reference numerals, and the description thereof will not be repeated.

In FIG. 6, 46 is a laser light source, 47 is a collimator lens, 48 is a beam splitter, 49 is a photodetector, 41 is a support frame, 40 and 42 are yokes, 43 is a slide bearing, 44 is a shaft, and 45 is a support plate. It is.

As shown in FIGS. 7 (a) and 7 (b), the tracking coil 25 has a portion cut off from the shaft 44, and is fixed so that the rectangular tracking coil 25 coincides with the central axis of the shaft 44, and the focusing coil 25 is fixed. The use coil 24 is wound around a relay member so as to be substantially parallel to the shaft 44, and the relay member is fixed to the shaft. The objective lens 23 is attached to the distal end of the shaft 44 via a support plate 45 so that the optical axis thereof is parallel to the central axis of the shaft 44. Part of the shaft 44 is a slide bearing provided on the yoke 42
By 43, it is slidably and rotatably supported. York 42
A focusing permanent magnet 27 is fixed so as to face the focusing coil 24, and a tracking permanent magnet 22 is fixed via a support frame 41 so as to face the tracking coil 25.

In the device configured as described above, when a current is applied to the focusing coil 24, the shaft 44 moves in the direction of the arrow A in the drawing due to the electromagnetic force with the focusing permanent magnet 27,
Focus control is performed. Also, tracking coil
When a current is passed through the shaft 25, the shaft 44 rotates in the direction of arrow B in the figure due to the electromagnetic force with the tracking permanent magnet 22, and tracking control is performed.

[Problems to be Solved by the Invention] However, in the objective lens driving device of the first example, the tracking coil is placed on the focusing coil 24.
The magnetic gap between the permanent magnets for focusing 27a, 27b and the yokes 30a, 30b due to the attachment of the 25a, 25b, the thickness of the outer peripheral portion of the objective lens holder and the thickness of each of the focusing coil and the tracking coil Therefore, there is a limit to the tracking driving force of the objective lens holder because the magnetic gap does not become smaller any more. In addition, there is a problem that the area of the focusing permanent magnets 27a and 27b with respect to the focusing coil is limited by the tracking permanent magnet.

Further, the objective lens driving device of the second example also has a problem that the structure of the shaft 44 or the yokes 40 and 42 becomes complicated and heavy, the strength tends to be insufficient, and the entire optical head device becomes large. I was

An object of the present invention is to provide an optical head device which solves the above-mentioned problems, is lightweight, has excellent response characteristics, and has stable operation.

[Means for Solving the Problems] The above problems are caused by a box-shaped base having an optical component mounted therein, a support shaft fixed to an upper surface of the base, and at least sliding with respect to the support shaft. A cylindrical objective lens holder that supports the objective lens at the bottom, which is provided movably and rotatably, and a sliding coil wound on the bottom side on the outer peripheral surface of the objective lens holder, A rotating coil comprising a plurality of substantially rectangular coils fixed on the outer peripheral surface of the objective lens holder on the side of the substrate and at positions not overlapping with each other in the normal direction of the outer peripheral surface with the sliding coil; And a magnetic circuit formed on the upper surface of the base, forming a magnetic field so as to cross each of the rotating coil and the sliding coil. Minutes from each other A notch is provided between the portions of the objective lens holder to which the plurality of substantially rectangular coils are fixed, and the rotating coil of the objective lens holder is fixed. The optical head device according to the present invention is characterized in that the portion that forms the magnetic field crossing the rotating coil of the magnetic circuit is buried in the base.

[Operation] In the optical head device of the present invention, since the sliding coil and the rotating coil are provided on the same surface of the optical system holder, the permanent magnet is opposed to almost the entire sliding coil. Since it is not necessary to provide a wide gap between the yoke and the permanent magnet facing the rotation coil, the tracking driving force and the focus driving force can be increased, and the response performance can be improved. Since there is no need to add new components, the optical system holder is lightweight. In addition, since the center of gravity is lowered, focus driving is performed in the vicinity of the center of gravity, and the optical axis is hardly tilted.

In the optical system driving device of the present invention, if the rotation coil is provided below the sliding coil with respect to the base, the notch portion can be provided in the optical system holder, and the weight can be reduced. Further, in the present invention, the optical system holder becomes large only in a portion where the rotation coil is fixed, but if this portion and a magnetic circuit that forms a magnetic field across the rotation coil are embedded in the base, The size of the entire optical head device is not increased.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

First, prior to an embodiment of the present invention, a reference example according to the present invention will be described.

FIG. 1 is an exploded perspective view of a reference example of the optical head device of the present invention.

In FIG. 1, a cylindrical objective lens holder 1 supporting an objective lens 2 at the bottom is supported by a support shaft 31 via a bearing 31.
Inserted at 11. In the vicinity of the bearing 31, the objective lens 2 and a weight 12 having substantially the same weight as the objective lens 2 are mounted in order to maintain weight balance. A focusing coil 3 is wound around the outer periphery of the objective lens holder 1, and substantially rectangular tracking coils 4 a and 4 b are attached below the focusing coil 3.

The support shaft 11 is directly fixed to the optical component holding member 9 by press fitting or the like, and the inclination of the optical system provided on the optical component holding member 9 with respect to the optical axis can be easily suppressed to 0.1 ° or less. Further, the optical component holding member 9 has the tracking permanent magnets 7a and 7b, 7c and 7d and the tracking permanent magnets 7a to 7d near the outer peripheral portion of the objective lens holder 1 so as to face the tracking coils 4a and 4b. Non-magnetic material 13a to 13f sandwiching 7d
Are respectively fixed. The tracking coil 4a
Although the tracking permanent magnets 7a and 7b and the non-magnetic material 13b are not shown, the tracking coil 4b, the tracking permanent magnets 7c and 7d, and the non-magnetic material
It is installed in the opposite position.

Tracking permanent magnets 7a to 7d and non-magnetic bodies 13a to 13f
The focusing permanent magnets 6a and 6b are fixed on the upper surface of the lens so as to face the focusing coil 3. The yokes 8a and 8b are fixed as opposed magnetic poles of the tracking permanent magnets 7a to 7d and the focusing permanent magnets 6a and 6b in the vicinity of the inner peripheral portion of the objective lens holder 1 and opposed to the inner peripheral portion.

In the objective lens driving device of this embodiment, the focusing coil 3 and the tracking coils 4a and 4b are separately mounted, so that the focusing permanent magnets 6a and 6b and the tracking permanent magnets 7a to 7d and the yokes 8a and 8b are used. Is the fifth
The magnetic flux density is increased as compared with the conventional example shown in FIG.

The focusing permanent magnets 6a and 6b, the tracking permanent magnets 7a to 7d, the yokes 8a and 8b, and the nonmagnetic members 13a to 13f are directly attached to the optical component holding member 9 with an adhesive or the like.

The neutral point holding of the objective lens holder 1 is performed by a neutral point holding rubber 5 fixed to the optical component holding member 9. The objective lens holder 1 can be rotated left and right and vertically slid within the holding range.

Although there are various driving systems for the optical component holding member 9, the embodiment using a linear motor capable of high-speed access operation has been described here. 10a and 10b are rails, 3
2 is a linear motor coil, 33 is a magnet, and 34 is a yoke.

FIG. 2 is a vertical sectional view in the direction of AA 'of the optical head device when the objective lens holder is incorporated.

As shown in FIG. 2, when the focusing permanent magnets 6a and 6b and the tracking permanent magnets 7a and 7c are placed in parallel with different polarities, no magnetic field is generated perpendicular to each coil, and focus control is performed. Since the tracking control becomes impossible, the same poles are placed in parallel. The focusing permanent magnets 6a and 6b and the tracking permanent magnets 7b and 7d are similarly mounted. Tracking permanent magnet 7
Non-magnetic members 13a to 13f are placed between a, 7b, 7c, and 7d to prevent disturbance of the magnetic field. In this reference example, the tracking coil 4
Although an example in which four tracking permanent magnets 7a to 7d are provided for two a and 4b is shown, the present invention can be applied to a case where two tracking permanent magnets are provided for four tracking coils.

Inside the optical component holding member 9, an optical system including optical components such as a laser light source 14, a collimator lens 15, a beam shaping prism 16, a beam splitter 17, a condensing lens 18, a half mirror 19, and detectors 20a and 20b is installed. Have been.

 Next, examples of the present invention will be described.

FIG. 3 is an exploded perspective view of one embodiment of the optical head device of the present invention. FIG. 4 is a longitudinal sectional view in the AA 'direction of the optical head device when the objective lens holding pair is incorporated. Note that the same members as those of the reference example shown in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description will be omitted. In the present invention, only the tracking drive unit for the tracking coil 4b will be described for simplicity, and description of the tracking coil 4a will be omitted, but the configuration is the same. In this embodiment, the base corresponds to the optical component holding member.

As shown in FIGS. 3 and 4, in this embodiment,
The tracking drive section of the objective lens drive device is provided in the optical component holding member 9. That is, the optical component holding member 9 includes the tracking coil of the objective lens holder 1.
Tracking hole corresponding to the rotation range of the mounting part of 4b
38, permanent magnets 7c and 7d for tracking and a non-magnetic material 13e are embedded near the outer peripheral portion of the mounting portion of the tracking coil 4b so as to face the inserted tracking coil 4b, and the inner peripheral portion is provided. A yoke hole 36 is provided in the vicinity, and the yoke 8b is buried approximately half. One of the tracking permanent magnets 7c, 7d is provided with focusing permanent magnet mounting grooves 37, 39. The optical component holding member 9 is provided with a hole 35 corresponding to the movable range of the objective lens 2.

Since the objective lens device according to the present embodiment can omit the non-magnetic members 13a, 13c, 13d, and 13f according to the reference example, it is possible to reduce the number of components, and it is possible to embed a tracking drive portion. Even if the size of the objective lens holder 1 is increased, the size of the entire optical head device is not increased.

In this embodiment, it is not always necessary to bury the yokes 8a and 8b, but the tracking permanent magnets 7a to 7d
And the magnetic field strength applied to the tracking coils 4a and 4b can be increased.

[Effects of the Invention] As described above in detail, the optical head moving device of the present invention provides the sliding coil and the rotating coil on the same surface of the optical system holder, thereby enabling the sliding of the optical head. A permanent magnet can be provided so as to face almost the entire coil, and it is not necessary to widen a gap between the yoke and the permanent magnet facing the coil for rotation, and it is not necessary to add a new component. It is lightweight and has excellent tracking control and focus control response characteristics. In addition, since the center of gravity is lowered, focus driving is performed in the vicinity of the center of gravity, the optical axis does not easily fall, and the operation is stable.

In the optical system driving device of the present invention, if the rotation coil is provided below the sliding coil with respect to the base, the notch portion can be provided in the optical system holder, and the weight can be reduced. Further, in the present invention, the optical system holder becomes large only in a portion where the rotation coil is fixed, but if this portion and a magnetic circuit that forms a magnetic field across the rotation coil are embedded in the base, The size of the entire optical head device is not increased.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a reference example of the optical head device of the present invention. FIG. 2 is a vertical sectional view in the AA 'direction of the optical head device of the above-described reference example in which an objective lens holder is incorporated. FIG. 3 is an exploded perspective view of one embodiment of the optical head device of the present invention. FIG. 4 is a longitudinal sectional view in the AA 'direction of the optical head device of the above-mentioned embodiment when the objective lens holder is incorporated. FIG. 5 is a perspective view of a first example of a conventional objective lens driving device. FIG. 6 is a sectional view of a main part of a second example of the conventional objective lens driving device. FIG. 7 (a) is a plan view of a mounting portion of a tracking coil of a second example of the objective lens driving device,
(B) is a front view in the bb 'direction of the plan view (a). 3 Focusing coils 4a, 4b Tracking coils 6a, 6b Focusing permanent magnets 7a, 7b, 7c, 7d Tracking permanent magnets 8a, 8b Yoke 9 Optical component holding member 11 …… Support shafts 13a, 13b, 13c, 13d, 13e, 13f …… Non-magnetic material

Continuation of the front page (56) References JP-A-59-185040 (JP, A) JP-A-59-160832 (JP, A) JP-A-59-188847 (JP, A) JP-A-60-98532 (JP , A) Japanese Utility Model Showa 60-106218 (JP, U)

Claims (1)

(57) [Claims] 1. A box-shaped base having an optical component mounted therein, a support shaft fixed to an upper surface of the base, and at least slidably and rotatable with respect to the support shaft.
A cylindrical objective lens holder supporting the objective lens at the bottom, a sliding coil wound on the bottom side on the outer peripheral surface of the objective lens holder, and a sliding coil wound on the outer peripheral surface of the objective lens holder; A rotating coil composed of a plurality of substantially rectangular coils, fixed to positions that do not overlap with each other in the normal direction of the sliding coil and the outer peripheral surface on the base side and the rotating coil; A magnetic circuit formed on the upper surface of the base, forming a magnetic field so as to cross each of the sliding coils, wherein a plurality of substantially rectangular coils are separated from each other and disposed on the outer peripheral surface. A notch is provided between a portion of the objective lens holding member to which the plurality of substantially rectangular coils are fixed, and a portion of the objective lens holding member to which the rotation coil is fixed is connected to the notch. An optical head device, wherein a portion of a magnetic circuit that forms a magnetic field crossing the rotation coil is embedded in the base.