JPH0656662B2 - Optical system drive - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical system driving device, and more particularly to a device capable of driving an optical system two-dimensionally. Such an optical system driving device is suitably used, for example, for driving an objective lens of an optical head in an optical information recording / reproducing device.

[Conventional technology and its problems]

Conventionally, an optical information recording / reproducing apparatus is practically used for recording information on the recording medium and / or reproducing the information recorded on the recording medium while irradiating the surface of the information recording medium with laser light in a spot form. Has been converted.

An optical disk device is an example of such a device. On an optical disc, which is a recording medium on which information is reproduced by an optical disc device, information tracks consisting of rows of information pits having a width of about 1 to 2 μm and a length of about 1 to 3 μm are formed in a spiral or concentric shape. When reproducing the information recorded as the information pit train, the optical head irradiates the information track of the optical disc with a laser light beam in the form of a minute spot while rotating the optical disc, and the information pit train is scanned by the beam spot. . When the reflected light or transmitted light of the light irradiated on the optical disk surface is detected by the photodetector in this way, the optical properties of the light incident on the photodetector depend on whether or not an information pit exists at the beam spot position. Changes. Thus, the reproduction signal corresponding to the information pit string can be obtained.

One of the features of the optical disc is that high density recording is possible, so the information pits are quite small as described above,
For this reason, in the optical disk device, it is necessary that the light beam spot always accurately follows the information track (tracking) and the light beam spot is always focused on the information track (focusing) for accurate information reproduction. is there. Therefore, generally, in an optical disc apparatus, auto-tracking control for correcting a light beam spot position shift caused by eccentricity of the optical disc and auto-focusing control for correcting a focus shift caused by a warp of the optical disc are performed.

As a method of realizing such auto-tracking control and auto-focusing control, an objective lens, which is a light beam focusing means of an optical head, can be moved by a spring-like structure in the optical axis direction of the lens and a direction orthogonal thereto. In general, a method of supporting and driving an objective lens so as to eliminate the shift based on the detection signals of the positional shift of the light beam spot and the focus shift is generally used.

FIG. 3 is a perspective view showing a conventional objective lens driving device of an optical head having such means for auto-tracking control and auto-focusing control.

In FIG. 3, reference numeral 2 denotes a base, on which a yoke 6 having a permanent magnet 4 is fixed. One end of a pair of leaf springs 8a and 8b in a vertical plane is fixed to the yoke, and opposite vertical end faces of a square relay plate 10 are fixed to the other end of the leaf spring. One end of a pair of leaf springs 12a and 12b, which are respectively in the horizontal plane, is fixed to the opposing horizontal end faces of the relay plate 10, and an objective lens holder 14 is fixedly attached to the other end of the leaf springs. ing. Reference numeral 16 is an objective lens held by the holder. On the other hand, a yoke 20 provided with a permanent magnet 18 is fixed to the base 2.

A coil 22 wound around the horizontal direction is attached to the permanent magnet 4 side of the objective lens holder 14, and the coil 22 is arranged so as to surround a part of the yoke 6.
On the permanent magnet 18 side of the objective lens holder 14, a coil 24 wound around the vertical direction is attached.
The coil is arranged so as to surround a part of the yoke 20.

A through hole 26 is provided in the base 2 below the objective lens 16 to secure an optical path for a light beam passing through the objective lens 16.

In the objective lens driving device as described above, the relay plate 1
0, the leaf springs 12a and 12b, the objective lens holder 14, the objective lens 16, and the coils 22 and 24 can swing horizontally with respect to the yoke 6 via the leaf springs 8a and 8b. As a result, horizontal movement of the objective lens 16 (that is, movement for automatic tracking control) is realized. This movement is driven by the interaction with the magnetic field by the permanent magnet 4 by passing a current through the coil 22.

Further, a portion including the objective lens holder 14, the objective lens 16, and the coils 22 and 24 is movable in the vertical direction with respect to the relay plate 10 via the leaf springs 12a and 12b. Vertical movement (that is, movement for autofocusing control) is realized.
This movement is driven by the interaction with the magnetic field by the permanent magnet 18 by passing a current through the coil 24.

In the conventional objective lens driving device as described above, since the movable portion is supported by the leaf spring in two steps, the optical axis of the objective lens may be tilted due to the twist of the leaf spring. There is a problem that resonance occurs with respect to a high-frequency drive signal and the operation becomes unstable.

[Background of the Invention]

An objective lens driving device as shown in FIG. 4 can be considered as a solution to the above-mentioned problems of the conventional objective lens driving device.

In FIG. 4, reference numeral 30 denotes a base, which is a horizontal part 3
It has an angled shape having 0a and a vertical portion 30b. A pillar 34 to which a permanent magnet 32 is attached is fixed on the base horizontal portion 30a, and a ring-shaped permanent magnet 36 is provided.
Is fixed. On the other hand, the base vertical portion 30b has four wires 38a, 38b, 38 having the same bending elasticity.
One end of c, 38d is fixedly supported, and the wire 38
Both ends of a shaft 40a are fixed to the other ends of a and 38c, and both ends of a shaft 40b are fixed to both ends of the wires 38b and 38d. Wires 38a, 38b, 38c, 3
8d both extend in the horizontal direction, the wires 38a and 38c are arranged at the same height, and the wire 38b
And 38d are arranged at the same height, and the wire 38b is located below the wire 38a and the wire 38d is located below the wire 38c. Therefore, the axes 40a and 40
b is arranged horizontally and in parallel, and the axis 40b is the axis 4
It is located below 0a. A bearing 42a is slidably and rotatably coupled to the shaft 40a, and a bearing 4 is attached to the shaft 40b.
2b is slidably and rotatably connected. Reference numeral 44 denotes an objective lens holder, and the bearings 42a and 42b are fixed to the holder 44. 46 is an objective lens holder 44
Is an objective lens held by.

A flat coil 48 wound around a horizontal direction is attached to the surface of the objective lens holder 44 facing the permanent magnet 32, and one of two vertical winding portions of the coil is attached. The winding portion is arranged so as to face the permanent magnet 32. Below the objective lens holder 44, a coil 50 arranged coaxially inside the ring-shaped permanent magnet 36 is attached.

In addition, a through hole (not shown) is provided below the objective lens 46 in the base horizontal portion 30a, whereby an optical path for a light beam passing through the objective lens 46 is secured.

FIG. 5 is a perspective view showing details of the shafts 40a and 40b. A Teflon-based resin coating layer 41 is formed on the surface of the central portion of the shaft to reduce sliding friction with the bearings 42a and 42b.

In the objective lens driving device as described above, the coil 48
When a current is applied to the shaft, the portion including the objective lens holder 44, the objective lens 46, and the coils 48, 50 slides on the shafts 40a, 40b via the bearings 42a, 42b due to the interaction with the magnetic field of the permanent magnet 32. Then, it moves in the horizontal direction, whereby auto-tracking is performed. Since this auto-tracking drive is not performed via a spring member, resonance does not occur even by high-frequency drive.

In addition, by passing a current through the coil 50, the permanent magnet 36
By the interaction with the magnetic field by the shafts 40a, 40b, the bearing 42
a, 42b, objective lens holder 44, objective lens 46,
And the portion consisting of the coils 48, 50 is the wires 38a, 3
By bending through 8b, 38c, and 38d, it swings in the vertical direction, thereby performing autofocusing. During this autofocusing drive, the wire 38
Since a, 38b, 38c and 38d are similarly deformed, the parallel relationship and the vertical positional relationship of the axes 40a and 40b are unchanged, so that autofocusing is performed without causing the optical axis tilt of the objective lens 46.

According to such an objective lens driving device, the above problems of the conventional device as shown in FIG. 3 can be solved.

However, in the objective lens driving device as shown in FIG. 4, in order to obtain desired characteristics, the wires 38a,
38b, 38c, and 38d have a certain length, and the objective lens 46 has the base vertical portion 3 more than the axes 40a and 40b.
It is held by the objective lens holding body 44 at a position far from 0b, and the permanent magnet 36 is arranged at a position corresponding to this, so that the length l ₁ of the base horizontal portion 30a is relatively long, and the apparatus is small. There is a limit to conversion.

Therefore, the present invention solves both the above problems of the conventional driving device as shown in FIG. 3 and the above problems of the driving device as shown in FIG. It is also an object of the present invention to provide an optical system driving device that can be downsized.

[Outline of Invention]

According to the present invention, the optical system holding means for holding the optical system is relatively slidable in the direction perpendicular to the optical axis of the optical system and is relatively centered in the direction. Respectively mounted to the first part of the rigid support means via a plurality of first pivotably rotatable shaft-bearing pairs, each second part of said support means of said first shaft-bearing set. Each of the second shaft-bearing sets is attached to the base via a plurality of second shaft-bearing sets that are relatively rotatable about a direction parallel to the set direction, and the optical system is attached to the first shaft-bearing set. An optical system driving device is provided, which is held by the optical system holding means at a position closer to the base than the set.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of an optical system driving device of the present invention. This embodiment is applied to driving an objective lens of an optical information recording / reproducing apparatus.

In FIG. 1, members having the same functions as those in FIG. 4 are designated by the same reference numerals.

In FIG. 1, 30 is a base, which is a horizontal part 3
It has an angled shape having 0a and a vertical portion 30b. A pillar 34 to which a permanent magnet 32 is attached is fixed on the base horizontal portion 30a, and a ring-shaped permanent magnet 36 is provided.
Is fixed. On the other hand, the base vertical portion 30b has bearings 37a, 37b, 3 on both left and right end surfaces thereof so as to be respectively rotatable with respect to a shaft (not shown) provided in the horizontal direction.
7c and 37d are combined. The bearings 37a and 37c are arranged so as to be coaxial with each other, and the bearings 37b and 37d are arranged.
And are arranged so as to be coaxial. The bearings 37a, 3
7b, 37c and 37d have fixed wires 38a, 38b, 38c and 38d, each of which is made of a rigid body, fixedly supported at one end thereof, and the other end of each wire 38a and 38c is provided with a shaft 40.
Both ends of a are fixed, and both ends of a shaft 40b are fixed to both ends of the wires 38b and 38d. Wire 38
a, 38b, 38c and 38d all extend in the horizontal direction, the wires 38a and 38c are arranged at the same height, the wires 38b and 38d are arranged at the same height, and The wire 38b is located below the wire 38a and the wire 38d is located below the wire 38c.
Therefore, the shafts 40a and 40b are arranged horizontally and in parallel, and the shaft 40b is located below the shaft 40a. The axis 4
A bearing 42a is slidably and rotatably coupled to the shaft 0a, and a bearing 42b is slidably and rotatably coupled to the shaft 40b. Reference numeral 44 denotes an objective lens holder, and the bearings 42a and 42b are fixed to the holder 44. 46
Is an objective lens held by the objective lens holder 44.

A flat coil 48 wound around a horizontal direction is attached to the surface of the objective lens holder 44 facing the permanent magnet 32, and one of two vertical winding portions of the coil is attached. The winding portion is arranged so as to face the permanent magnet 32. Below the objective lens holder 44, a coil 50 arranged coaxially inside the ring-shaped permanent magnet 36 is attached.

In addition, a through hole (not shown) is provided below the objective lens 46 in the base horizontal portion 30a, whereby an optical path for a light beam passing through the objective lens 46 is secured.

As shown, the apparatus of this embodiment differs from the apparatus shown in FIG. 4 in the arrangement of the objective lens 46. That is, the objective lens holding body 44 has a main body portion from the portion where the bearings 42a and 42b are provided to the base vertical portion 30b, and the objective lens 46 is located there. That is, the objective lens is located closer to the base vertical portion 30b than the shafts 40a, 40b and the bearings 42a, 42b. The coil 48 is attached to the surface of the objective lens holder 44 on the side opposite to the side opposite to the base vertical portion 30b, and the permanent magnets 32 and the columns 34 are arranged at the positions corresponding thereto. Also,
The coil 50 is attached to the objective lens holder 44 below the objective lens 46, and the permanent magnet 36 is arranged at a position corresponding to this.

Further, in the device of the present embodiment, as can be seen from the above description, the base vertical portion 30b and the bearings 37a, 37b, 37.
c, 37d and shafts (not shown) connected thereto, wires 38a, 38b, 38c, 38d, and shafts 40a, 4
0b, bearings 42a and 42b, and objective lens holder 44
And constitute a parallel link mechanism.

In the apparatus of the present embodiment as described above, the objective lens is driven by the same operation as that of the apparatus shown in FIG.

That is, by passing an electric current through the coil 48, the permanent magnet 32
By the interaction with the magnetic field due to, the portion composed of the objective lens holder 44, the objective lens 46, and the coils 48, 50 slides horizontally with respect to the shafts 40a, 40b via the bearings 42a, 42b. Auto-tracking is performed by. Since this auto-tracking drive is not performed via a spring member, resonance does not occur even by high-frequency drive.

In addition, by passing an electric current through the coil 50, the permanent magnet 32
By the interaction with the magnetic field by the shafts 40a, 40b, the bearing 42
a, 42b, objective lens holder 44, objective lens 46,
And the portion consisting of the coils 48, 50 is the wires 38a, 3
8b, 38c, 38d through their bearings 37a,
Rotation around a shaft (not shown) to which 37b, 37c, and 37d are coupled causes them to swing in the vertical direction, thereby performing autofocusing. 2 (a) and 2 (b) are partial side views for explaining the operation during the autofocusing. FIG. 2 (a) shows a state in which the objective lens 46 is in the neutral position with respect to the focusing movement direction.
8c and 38d (38a and 38b also) are horizontal. Second
FIG. 6B shows a state in which the objective lens holder 44 has moved upward by a distance A from the state shown in FIG. 2A in response to the electric current applied to the coil 50, and each wire is inclined from the horizontal by an angle θ. There is. Thus, by the parallel link mechanism, the objective lens 46
Auto-focusing is performed without causing the optical axis to tilt. At this time, the objective lens 46 also moves in the horizontal direction, but since the angle θ is actually not so large, the horizontal movement can be ignored.

In the apparatus of this embodiment, the objective lens 46 has axes 40a, 4a.
Since it is located closer to the base vertical portion 30b than 0b, the permanent magnet 36 may be mounted on the base vertical portion 30b side. Therefore, the permanent magnets 32 and the support 34 may be mounted on the shafts 40a, 40a.
Even on the side opposite to the base vertical portion 30b side of b, the length l ₂ of the base horizontal portion 30a may be relatively short. That is, l ₂ <l ₁ compared to the length l ₁ in the device of FIG. 3 above.

In the above embodiment, the bearings 42a and 42b fixed to the objective lens holder 44 as the first supporting means and the shafts 40a and 40b fixed to the wires 38a, 38b, 38c and 38d serving as the second supporting means. However, the first supporting means in the present invention is not limited to this, and conversely, the shaft fixed to the optical system holding means and the bearing fixed to the second supporting means. And other suitable means are possible.

Further, in the above embodiment, the parallel link mechanism is used as the related link mechanism of the second supporting means,
In the present invention, a link mechanism other than the parallel link mechanism can be used as the link mechanism.

Further, although the above-described embodiment is applied to drive the objective lens of the optical information recording / reproducing apparatus, the present invention can be applied to other appropriate optical system drive. The driven optical system is not limited to a lens or a lens system, but may be a mirror, a prism, or a composite optical system including these.

〔The invention's effect〕

According to the present invention as described above, since the leaf spring is not used as the supporting means, the operation is favorably performed without causing resonance when the optical system is driven, and the device can be downsized.

[Brief description of drawings]

FIG. 1, FIG. 3 and FIG. 4 are perspective views of the optical system driving device. 2 (a) and 2 (b) are partial side views for explaining the operation of the optical system driving device. FIG. 5 is a perspective view of the shaft. 30: base, 30a: horizontal part of base, 30b: vertical part of base, 32, 36: permanent magnets, 37a, 37b, 37c,
37d: bearing, 38a, 38b, 38c, 38d: wire, 40a, 40b: shaft, 42a, 42b: bearing, 4
4: objective lens holder, 46: objective lens, 48, 5
0: coil.

Claims (1)

[Claims] 1. A first shaft, wherein an optical system holding means for holding an optical system is relatively slidable in a direction perpendicular to an optical axis of the optical system and is rotatable about the direction. Each of the plurality of bearing sets is attached to a first portion of the rigid support means, and each second portion of the support means is relatively centered about a direction parallel to the direction of the first shaft-bearing set. Are attached to the base through a plurality of second shaft-bearing pairs that are rotatable in a dynamic manner, and the optical system is located at a position closer to the base than the first shaft-bearing pair. An optical system driving device characterized by being held by an optical system holding means.