JPH08138265A - Optical head device - Google Patents

Abstract

PURPOSE: To perform at least good reproducing of plural information recording media having their different specifications respectively even in a small-sized and inexpensive structure of the device. CONSTITUTION: A detecting system for detecting reflected light from an optical disk 10 is provided in a fixed position against the optical disk so as to constitute a stationary optical system 22, while a rotary blade rotatably provided in a plane parallel to a recording surface of the optical disk is arranged with plural objective lenses 14a and 14b for convergently irradiating the optical disk with a light beam emitted from a light source. Then, the rotary blade is rotated by controlling a current waveform to flow into a tracking coil, so that one objective lens suitable for this optical disk is selected, and is fixed on an optical axis of the light beam irradiating the optical disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording / reproducing information on / from an optical information recording medium such as an optical disk, and more particularly to an optical head apparatus used for the same.

[0002]

2. Description of the Related Art A technique for irradiating an optical disc with a light beam and detecting the reflected light to reproduce the information recorded on the optical disc is widely put to practical use as a CD (compact disc), an LD (laser disc) device or the like. Has been done. In such an optical disk reproducing apparatus, a light beam emitted from a light source such as a semiconductor laser is focused on a recording surface of the optical disk by an objective lens, and reflected light from the optical disk is detected by a photodetector to be recorded on the optical disk. Play the information that you have.

In such an optical disc, the recording density has been increased, and an optical disc having a standard different from that of the conventional optical disc has come to exist. For example, the size of a pit, which is the unit for recording information, is
Currently it is about 1 micron, but there is a high possibility that it will be reduced to submicron.

The recording density of an optical disk depends on the size of a recording / reproducing light spot irradiated onto the optical disk by a pickup (optical head) for reading minute pits for recording information formed on the optical disk. Decided.

The diameter of this spot depends on the wavelength of the laser used and the numerical aperture (NA: Numerical Apertur) of the objective lens.
It is determined by e) and is expressed by spot diameter = k × laser wavelength / NA. k is a constant.

Therefore, in order to read a higher density optical disc by using a small spot, it is necessary to use one having a short laser wavelength or a lens having a large NA.

Since the conventional information recording / reproducing apparatus has a structure having only one objective lens, it is impossible to read a high-density optical disc with a pickup equipped with an objective lens corresponding to the conventional optical disc.

That is, the pickup for high density is
When an objective lens with a large A is used, if the optical disc is tilted with respect to the objective lens, the disturbance of the spot becomes large, and therefore it cannot be commonly used in many cases. According to the conventional standard, the warp of the optical disc and the like are allowed up to a large value, but the new optical disc allows only the warp with a small value, so that the optical disc with the large warp cannot be read. Because of that.

The spot disturbance is affected by the thickness of the optical disc, and the thin optical disc has a small spot disturbance even if the optical disc is tilted. There is also an example in which it is used as a substrate.

In addition, even if the same optical disc is used, the optimum specifications of the objective lens may differ between the time of recording and the time of reproduction, but since it has a configuration having only one objective lens, this cannot be dealt with. There was a problem.

Further, discs having different substrate thicknesses are also emerging as a new standard, and there is a risk that the new device will not be able to record or reproduce information on discs of conventional standards.

The standard is the thickness of the disk substrate.
This type of optical disc generally has a structure in which a reflective film is formed on a transparent substrate (hereinafter referred to as a disc substrate) on which information is recorded in the form of pits, and a protective layer is formed thereon. The light beam is applied to the reflective film, which is the recording surface, from the transparent substrate side. In this case, the reproduction characteristic changes depending on the thickness of the disc substrate. 1A and 1B show changes in transmitted wavefront aberration when the optical disc is tilted with respect to the objective lens. 1A shows the disk substrate having a thickness of 1.2 mm, and FIG. 1B shows the disk substrate having a thickness of 0.6 mm. from now on,
Even if the objective lens has the same numerical aperture, the thinner the disc substrate, the smaller the transmitted wavefront aberration due to the disc tilt and the better the focusing property of the focused spot on the recording surface, so that the quality of the reproduced information signal may be high. You can see that you can get it. Therefore, an optical disk device using an optical disk having a thin disk substrate has appeared. In this way, when there are optical disks with different disk substrate thicknesses,
Naturally, there is a demand that these can be reproduced by the same device.

In order to satisfactorily reproduce information recorded on a plurality of types of optical discs having different disc substrate thicknesses, it is proposed to insert a flat plate in parallel between the optical disc and the objective lens. ((1) JP-A-4-372734, (2) JP-A-5-266492, (3)
JP-A-62-66433). This is because the optical thickness of the parallel plate and the optical thickness of the optical disk are equal to the designed lens load of the objective lens. By inserting the optical disc between the objective lens and the objective lens, information can be stably reproduced from the optical disc with a small transmitted wavefront aberration.

In an apparatus using such a parallel plate, it is important to insert the flat plate in the optical path in parallel so as not to cause an inclination with respect to the optical disk and the objective lens, and the parallel plate moving mechanism has high accuracy. There is a problem of being requested.
Further, when the parallel plate is tilted with respect to the optical disc and the objective lens, coma aberration occurs, so that the shape of the focused spot is not improved even if the spherical aberration is reduced by inserting the parallel plate. Moreover, the distance (working distance) between the objective lens and the optical disk is small, and it is very difficult to insert a parallel plate into this space.

For the same purpose, a parallel plate may be inserted between the objective lens and the light source ((4) JP-A-5-24109).
5) Alternatively, by inserting a compensating lens, it is proposed that information can be excellently reproduced from optical disks having different disk substrate thicknesses ((5) JP-A-5-54406, (6)). JP-A-5-205282,
(7) JP-A-5-266511). This is because when the optical disc thickness differs depending on the lens load in the design of the objective lens, spherical aberration occurs and the shape of the light spot to be focused on the recording surface of the optical disc becomes large, which results in accurate information recording. Since reproduction cannot be performed, the wavefront of the light beam incident on the objective lens is manipulated to prevent the occurrence of spherical aberration, and a minute light spot is formed to achieve stable reproduction of information from the optical disc.

As means for preventing the occurrence of spherical aberration, (5) a wavefront correction lens (for example, a concave lens) such as a concave lens in JP-A-5-54406, (6) a compensation lens made of a liquid crystal material in JP-A-5-205282, (7) Japanese Patent Laid-Open No. 5-
In 266511, a correction lens composed of a plurality of lens elements each having a variable air gap is used.

However, in the optical disk device, the objective lens moves in the optical axis direction following the warp of the optical disk. Therefore, in the method of processing the wavefront of the light beam incident on the objective lens to cancel the spherical aberration. If the warp of the optical disk is large, the change in the curvature of the light beam incident on the objective lens cannot be ignored, and the spherical aberration cannot be sufficiently canceled out.

Further, in order to satisfactorily reproduce information recorded on a plurality of types of optical discs having different substrate thicknesses, a plurality of optical heads corresponding to the optical discs having different substrate thicknesses are selectively used. A device adapted to be used has also been proposed ((8) JP-A-4-95224). Specifically, each optical head includes a semiconductor laser that is a light source, an objective lens, and a photodetector. Also,
In order to selectively use these optical heads, a head moving mechanism for moving the selected optical head along the radial direction of the optical disk is provided corresponding to each optical head.

However, in such a structure having a plurality of optical heads and a head moving mechanism corresponding to the thickness of the disk substrate, there is a problem that the structure of the entire optical disk device becomes very complicated and large. is there. In other words, the original merit of performing information reproduction from optical discs having a plurality of specifications with different substrate thicknesses with the same optical disc device is lost.

On the other hand, as a means for stably reproducing information from a plurality of types of optical discs having different recording densities, one having a variable focal length has been proposed ((9) JP-A-5-54414). This uses a liquid crystal lens that is configured to change the focal length by electrically controlling the curvature of the lens in which the liquid crystal is enclosed, and shortens the focal length when the density of the information recorded on the optical disc is high. As a result, information is always stably reproduced on optical disks having different recording densities. Since the aperture of the lens does not change,
When the focal length becomes short, the numerical aperture becomes large, and a minute light spot can be formed on the recording surface of the optical disc.

This method uses the numerical aperture (NA) of the objective lens.
May be realized under conditions where is relatively small,
In an optical disc, an objective lens having a large numerical aperture (for example, NA = 0.4 for a CD) is used for focusing on a small light spot.
5 and LD uses NA = 0.55), it is very difficult to change the surface shape of the liquid crystal lens so that the transmitted wavefront aberration is small.

As described above, since the conventional information recording / reproducing apparatus has a configuration having only one objective lens, a plurality of information recordings having different standards such as a difference in recording density, a warp allowable amount, a substrate thickness and the like are recorded. There is a problem in that it is not possible to cope with the case where the medium is used, or even when the same information recording medium is used, when the optimum lens specifications differ between recording and reproducing.

It is possible to prepare a plurality of dedicated pickups using a dedicated objective lens adapted to each standard or specification, and switch and use them, but in such a case, the mechanism is Not only is the device complicated and the size of the device increased, but the cost also rises, so there is a problem that it cannot be put to practical use.

In addition, any of the methods conventionally known as a technique for favorably reproducing information recorded on a plurality of types of optical discs having different disc substrate thicknesses in the same optical disc device has practical problems.

That is, in the case where the parallel plate is inserted between the optical disk and the objective lens, the parallel plate is inserted in the optical path so that the parallel plate is not tilted with respect to the optical disk and the objective lens. High accuracy is required for the moving mechanism, and when the parallel plate tilts with respect to the optical disc and the objective lens, coma aberration occurs and the shape of the focused spot deteriorates. There is a problem that it is extremely difficult to insert a flat plate.

Further, in the method of inserting a parallel plate or a compensating lens for preventing the occurrence of spherical aberration by manipulating the wavefront of the light beam incident on the objective lens between the objective lens and the light source, the method follows the warp of the optical disc. Since the objective lens moves in the optical axis direction, there is a problem that if the optical disc has a large warp, the change in the curvature of the light beam incident on the objective lens cannot be ignored and spherical aberration cannot be canceled out sufficiently. It was

Further, a plurality of optical heads equipped with a semiconductor laser, an objective lens, and a photodetector are provided corresponding to the respective optical disks having different substrate thicknesses, and these optical heads are respectively driven by dedicated head moving mechanisms. The one that is moved selectively along the radial direction and used selectively requires a plurality of optical heads and the same number of head moving mechanisms, which greatly complicates the overall configuration of the device.
There was a problem of increasing the size.

On the other hand, in order to stably reproduce information from a plurality of types of optical discs having different recording densities, a variable focus lens such as a liquid crystal lens constructed so that the focal length can be varied by electrical control is used in a very small amount. When an objective lens having a large numerical aperture (NA) is used for focusing on a light spot, it is very difficult to change the surface shape of the liquid crystal lens so that the transmitted wavefront aberration is small.

[0029]

As described above, the conventional optical head device has a drawback that a single device cannot handle recording media having different characteristics.

The present invention has been made in view of the above circumstances. A first object of the present invention is to provide a plurality of information recording media having different specifications of objective lenses while having a compact and inexpensive structure. An optical head capable of performing at least good reproduction is provided.

The second purpose is to reduce the size,
Further, it is an object of the present invention to provide an optical head which has a low-cost structure and is capable of performing excellent recording and reproduction even when the specifications of the objective lens are different during recording and reproduction.

[0032]

A first optical head device according to the present invention comprises a plurality of objective lenses for irradiating a recording medium with light, and a desired one of the plurality of objective lenses. And a means for selecting.

A second optical head device according to the present invention comprises:
A movable body that is movable in the thickness direction of the recording medium and in a direction orthogonal to the thickness direction, a plurality of objective lenses that irradiate the recording medium with light from a light source mounted on the movable body, and depending on the type of the recording medium. And an objective lens switching means for selecting a predetermined objective lens from the plurality of objective lenses and interposing the objective lens in the optical path of the light.

A third optical head device according to the present invention comprises:
A movable body having a magnet and movable in the thickness direction of the recording medium and in a direction orthogonal to the thickness direction; a plurality of objective lenses for irradiating the recording medium with light from a light source mounted on the movable body; Coil means arranged around the periphery for driving the movable body at least in a direction orthogonal to the thickness direction, and a predetermined objective lens is selected from the plurality of objective lenses according to the type of the recording medium, And an objective lens switching means interposed in the optical path of the light.

A fourth optical head device according to the present invention comprises:
A fixed optical system that includes a light source and a detection system that detects reflected light from the recording medium, and is provided at a fixed position with respect to the recording medium; By controlling the movement of the objective lens, the movable support means that supports the plurality of objective lenses and is movable in a plane parallel to the recording medium, and the movement of the movable support means,
And a control means for selectively fixing a desired one of the plurality of objective lenses on an optical axis of light irradiated on the recording medium.

More specifically, the first optical head device has the following features.

(1) The plurality of objective lenses include a plurality of objective lenses corresponding to a plurality of types of recording media, and the selecting means includes a means for selecting an objective lens according to a type of recording medium to be used. .

(2) Each of the plurality of objective lenses comprises a first objective lens suitable for recording on a recording medium and a second objective lens suitable for reproducing from the recording medium, and the selecting means records / records. A means for selecting an objective lens suitable for reproduction is provided.

(3) The plurality of objective lenses include a plurality of objective lenses suitable for signal processing with respect to the recording medium, and the selecting means includes means for selecting an objective lens suitable for signal processing.

(4) The selecting means holds the plurality of objective lenses, is rotatable about an axis perpendicular to the recording medium, and is movable in a direction of approaching and separating from the recording medium. It is provided with a holding means configured and means for positioning any one of the plurality of objective lenses in the optical path to the recording medium by rotating the holding means by a predetermined angle.

(5) In the holding means, a plurality of objective lenses are evenly arranged around the rotation center axis.

(6) In the holding means, a plurality of objective lenses are unevenly arranged around the rotation center axis.

(7) The holding means holds a plurality of objective lenses having a focal length such that the distance between the objective lenses and the recording medium is constant.

The second optical head device has the following features.

(1) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the center of gravity of a plurality of objective lenses mounted on the movable body is It is provided so as to coincide with the axis of the plain bearing mechanism.

(2) The movable body is supported by a slide bearing mechanism that allows sliding along the axis and rotation around the axis, and the plurality of objective lenses mounted on the movable body are the slide bearing mechanism. Are provided at equal intervals around the axis of.

(3) The movable body is supported by a slide bearing mechanism that allows sliding along the axis and rotation around the axis, and the plurality of objective lenses mounted on the movable body are the slide bearing mechanism. Are equidistant from the axis of.

(4) The plurality of objective lenses have different optical characteristics.

(5) The movable body is supported by a slide bearing mechanism that allows sliding along the axis and rotation around the axis, and the plurality of objective lenses mounted on the movable body are the slide bearing mechanism. Are provided at unequal intervals around the axis of.

(6) The objective lens switching means comprises tracking coil means for driving the movable body in a direction orthogonal to the thickness direction.

(7) The objective lens switching means includes coil means fixed to the movable body for driving the movable body in the direction orthogonal to the thickness direction.

(8) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the movable body is at least (360/360) around the axis.
It is configured to be rotatable by n) ° (where n is the number of objective lenses mounted on the movable body).

(9) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the plurality of objective lenses mounted on the movable body are the sliding bearing mechanism. Are provided at equal intervals around the axis of, and the objective lens switching means is arranged at equal intervals around the movable body and coil means for driving the movable body at least in the direction around the axis, A plurality of magnetic circuits for applying a magnetic field to the coil means.

(10) The number of the magnetic circuits is equal to the number of the objective lenses.

(11) The movable body is supported by a sliding bearing mechanism which allows sliding along the axis and rotation around the axis, and the objective lens switching means is arranged around the axis of the movable body. And a magnetic circuit which is arranged at equal intervals around the movable body and applies a magnetic field to the magnetic body.

(12) The magnetic bodies are arranged at equal intervals around the axis of the movable body. (13) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the movable body is used to balance the mass of the plurality of objective lenses around the axis. It has at least one counter weight.

(14) The objective lens and the counter weight are arranged at equal intervals around the axis.

(15) The number of magnetic circuits is the number of objective lenses and counterweights.

(16) The movable body is supported by a sliding bearing mechanism which allows sliding along the axis and rotation around the axis, and the movable body has a portion protruding in the radial direction.

(17) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the movable body has a cylindrical portion on one side in the axial direction. The other side is provided with a portion that projects more radially than this cylindrical portion.

(18) The lens switching means is fixed to the cylindrical portion of the movable body and faces the cylindrical portion of the movable body and the coil means for driving the movable body at least in the axial direction. However, the magnetic circuit is provided at a position lower than the protrusion and applies a magnetic field to the coil means.

(19) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the objective lenses are arranged at equal intervals around the axis of the movable body. The lens switching means includes coil means for driving the movable body in the axial direction, and a magnetic circuit for applying a magnetic field to the coil means, and the movable body is provided with a plurality of holes. A part of the magnetic circuit can be inserted into the hole.

(20) The number of the holes is equal to the number of the magnetic circuits, and a part of the magnetic circuits can be inserted into the holes.

(21) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the objective lenses are arranged at equal intervals around the axis of the movable body. The lens switching means includes first coil means for driving the movable body in the axial direction, and second coil means for driving the movable body in the axial direction.
A magnetic circuit for applying a magnetic field to the first and second coil means, wherein the movable body is provided with a plurality of holes, and a part of the magnetic circuit can be inserted into the holes. The driving around the axis is controlled so as to be performed after driving the movable body in the axial direction.

(22) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the objective lenses are arranged at equal intervals around the axis of the movable body. The lens switching means connects the movable body with the guide plate, the coil means for driving the movable body in the axial direction, the guide plate standing upright in an arc shape around the movable body, And a flexible printed circuit board capable of supplying an electric current to the coil means.

(23) The movable body is supported by a sliding bearing mechanism that allows sliding along the axis and rotation around the axis, and the objective lenses are arranged at equal intervals around the axis of the movable body. The lens switching means is a coil means for driving the movable body in the axial direction, a magnetic circuit for applying a magnetic field to the coil means, and a circular arc-shaped standing around the movable body, and at least (( 360 / n) /
2) a guide plate having a length (where n is the number of magnetic circuits), and a flexible printed circuit board that connects the movable body and the guide plate and can supply a current to the coil means. To do.

The third optical head device has the following features.

(1) The movable body has a plurality of projecting portions that project in the radial direction.

(2) The coil means comprises a yoke surrounding the movable body in an annular shape, and a coil fixed to the yoke.

(3) The yoke has a non-circular shape.

(4) The movable body is elastically supported in the thickness direction of the recording medium by a plurality of leaf springs.

(5) The movable body is supported by a sliding bearing mechanism which allows sliding along the shaft and rotation around the shaft, and the sliding bearing mechanism is elastically supported by a plurality of leaf springs so as to be axially movable. Is allowed, and the plurality of objective lenses are mounted on the movable body so that at least one of the plurality of objective lenses can move between a plurality of leaf springs.

(6) The lens switching means is fixed to a non-circular magnet fixed to the movable body, a yoke arranged around the movable body, and a position of the yoke close to the magnet. , Coil means for driving the movable body at least in a direction orthogonal to the thickness direction.

(7) The movable body is elastically supported by a hinge mechanism so as to be movable in at least a direction orthogonal to the thickness direction of the recording medium, and the plurality of objective lenses are at elastic angles of the hinge. It is mounted so that it is within the range.

(8) The hinge mechanism has at least two hinges.

(9) The lens switching means has a magnetic circuit capable of magnetically holding the movable body at two positions in a direction orthogonal to the thickness direction of the recording medium, and the objective lens is
It is arranged between the magnetic circuit and the hinge mechanism.

Further, the fourth optical head device has the following features.

(1) The movable supporting means is provided so as to be movable in a direction parallel to the recording surface of the recording medium, and the control means controls the moving length of the movable supporting member.

(2) The movable supporting means is rotatably provided in a plane parallel to the recording surface of the recording medium, and the control means controls the rotation angle of the movable supporting means.

(3) The movable supporting means comprises a ferromagnetic piece, the control means is a magnetic circuit for rotating the movable supporting means, and the ferromagnetic piece is located in the magnetic circuit. Positioning the movable support means in the rotation direction, and means for rotating the movable support means by supplying an electric current to the magnetic circuit.

(4) The magnetic circuit includes tracking coil means mounted on the peripheral surface of the movable support means and for performing tracking control of the light focused and irradiated onto the recording medium, and the control means comprises the tracking coil. By applying a predetermined current to the means, a larger rotational force is applied to the movable support means than in the tracking control, and the movable support means is pulled into a rotational position determined by the magnetic positioning action of the ferromagnetic piece to cause the plurality of the plurality of means to move. Means for selectively fixing one of the desired objective lenses on the optical axis of the light is provided.

(5) The plurality of objective lenses are evenly supported around the rotation axis of the movable supporting means.

(6) The fixed optical system is individually provided corresponding to each objective lens.

[0084]

According to the optical head device of the present invention, since a plurality of objective lenses can be selectively used,
For example, it is possible to prevent an increase in spherical aberration by using optimally manufactured objective lenses for optical disks having different thicknesses of a substrate and a protective layer. Moreover, since the plurality of objective lenses are supported on the same movable support member and one objective lens is selected by controlling the movable support member,
Only one lens actuator is required, and the overall configuration is significantly smaller and simpler than the configuration in which optical heads with different objective lens specifications and head moving mechanisms for moving them are provided for optical discs with different specifications. To be done.

If the objective lens is selected by using the lens actuator including the rotation supporting member and controlling the current flowing through the tracking coil, it is not necessary to provide a dedicated drive system for selecting the objective lens, Will be even easier. In this case, by properly setting the arrangement of the plurality of objective lenses, the arrangement of the magnetic circuit, and the shape of the tracking coil, one set of coils can be used in common even if the objective lens is selected, and the driving force It is possible to increase the number of coils and reduce the number of coils.

A ferromagnetic piece for magnetically positioning the rotary support member in the rotational direction in the rotary support member in the magnetic circuit is provided on the rotary support member to control the current supplied to the magnetic circuit. Thus, if the objective lens is selected while the rotational support member is positioned in the rotational direction, the selected objective lens can be accurately fixed on the optical axis of the light beam with which the optical disc is irradiated. When positioning a plurality of objective lenses on the optical axis of the light beam, it is necessary to set a plurality of neutral positions on the rotation support member.
By using the magnetic balance force in this way, it is possible to easily set a plurality of neutral positions.

By setting optical characteristics such as lens loads (thicknesses of optical disks), focal lengths and numerical apertures of a plurality of objective lenses to conditions suitable for the density of information recorded on each optical disk, Even when information is reproduced from the optical disc, it can be stably reproduced.

Even if the optical discs have different specifications, when they are mounted in the optical disc device, they are set with the surface on which the light beam is incident as a reference. It is possible to minimize the moving distance of the lens actuator in the optical axis direction.

When one of the optical disks is mounted in a cartridge or the like, the objective lens which is not used for reproduction can be constructed so as not to get in the way when the window width of the cartridge is restricted.

The factor of lowering the focused spot on the optical disc due to the relative inclination of the objective lens and the optical disc has a greater effect on the objective lens having a larger numerical aperture, so that the objective lens having a larger numerical aperture is preferentially positioned. As a result, the deterioration of the reproduced signal can be suppressed to a minimum.

If the outer diameter of the objective lens is the same, any combination of objective lenses can be set without any restrictions when mounting the objective lens on the actuator, and if the weight is the same, the vibration of the lens actuator will occur. The characteristics are not deteriorated.

Further, since the optical head device of the present invention is constructed so that a plurality of objective lenses can be selectively used,
For example, it is possible to prevent an increase in spherical aberration by using optimally manufactured objective lenses for optical disks having different thicknesses of a substrate and a protective layer. Moreover, since the plurality of objective lenses are supported on the same movable support member and one objective lens is selected by controlling the movable support member,
Only one lens actuator is required, and the overall configuration is significantly smaller and simpler than the configuration in which optical heads with different objective lens specifications and head moving mechanisms for moving them are provided for optical discs with different specifications. To be done.

When the objective lens is selected by using the lens actuator including the rotation supporting member and controlling the current flowing through the tracking coil, it is not necessary to provide a dedicated drive system for selecting the objective lens, Will be even easier. In this case, by properly setting the arrangement of the plurality of objective lenses, the arrangement of the magnetic circuit, and the shape of the tracking coil, one set of coils can be used in common even if the objective lens is selected, and the driving force It is possible to increase the number of coils and reduce the number of coils.

A ferromagnetic piece for magnetically positioning the rotary support member in the rotation direction while being positioned in the magnetic circuit on the rotary support member is provided on the rotary support member, and the current supplied to the magnetic circuit is controlled. Thus, if the objective lens is selected while the rotational support member is positioned in the rotational direction, the selected objective lens can be accurately fixed on the optical axis of the light beam with which the optical disc is irradiated. When positioning a plurality of objective lenses on the optical axis of the light beam, it is necessary to set a plurality of neutral positions on the rotation support member.
By using the magnetic balance force in this way, it is possible to easily set a plurality of neutral positions.

By setting the optical characteristics such as the lens load (thickness of the optical disk), the focal length, and the numerical aperture of the plurality of objective lenses to the conditions suitable for the density of the information recorded on each optical disk, Even when information is reproduced from the optical disc, it can be stably reproduced.

Even if the optical discs have different specifications, they are set with reference to the surface on which the light beam enters when they are mounted in the optical disc device. Therefore, by keeping the working distances of a plurality of objective lenses the same. It is possible to minimize the moving distance of the lens actuator in the optical axis direction.

When one of the optical disks is mounted in a cartridge or the like, the objective lens which is not used for reproduction can be constructed so as not to get in the way when the window width of the cartridge is restricted.

The factor of lowering the focused spot on the optical disc due to the relative inclination of the objective lens and the optical disc has a greater effect on the objective lens having a larger numerical aperture. Therefore, the objective lens having a large numerical aperture is preferentially positioned. As a result, the deterioration of the reproduced signal can be suppressed to a minimum.

If the outer diameter of the objective lens is the same, any combination of objective lenses can be set without any restrictions when mounting the objective lens on the actuator, and if the weight is the same, the vibration of the lens actuator will occur. The characteristics are not deteriorated.

[0100]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an optical head device according to the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 2 shows the first embodiment.
It will be described with reference to FIGS.

First, with reference to FIGS. 2 to 4, the structure of the main part of the optical disc apparatus 1 according to the present invention as an information recording / reproducing apparatus will be described.

The optical disk device 1 has a spindle motor 12 (see FIG. 3) as a disk driving means for holding and rotating an optical disk 10 (only a part of which is indicated by a chain double-dashed line) which is an information recording medium.

On the lower surface side of the optical disk 10 which is rotated by the spindle motor 12, a plurality of (two in this case, first and second) objective lenses 14a and 14b of different types to be described later and laser light guide means are provided. A moving optical system 18 including a rising mirror 16 (see FIG. 4) and the like is mounted, and a pickup 20 is provided as an optical head that is linearly movable in the radial direction (direction of arrow A) of the optical disc 10. .

Optical disc 1 on the moving path of pickup 20
As shown in FIG. 2, a fixed optical unit 22 is provided on the radial extension line of 0, and the laser beam LB is provided between the fixed optical unit 22 and the moving optical system 18 mounted on the pickup 20.
It is designed to irradiate and receive.

Pickup 2 from fixed optical unit 22
The laser beam LB emitted toward the pickup 20 along the moving direction of 0 is raised at a right angle by the raising mirror 16 which constitutes the moving optical system 18, and passes through the objective lens 14a or 14b to the information recording surface of the optical disc 10. 10
It is focused on a. Further, the laser beam LB reflected by the information recording surface 10a passes through the objective lens 14a or 14b, is then bent horizontally by the rising mirror 16 and is sent to the fixed optical unit 22, where information reading processing is performed. .

As shown in FIG. 3, the fixed optical unit 22 includes a semiconductor laser 24 which is a laser light generating means for generating the laser light LB, a collimator lens 26 for collimating the laser light LB generated by the semiconductor laser 24, and a laser light. The first beam splitter 28 for separating the laser light LB that travels the LB toward the optical disk 10 and the reflected laser light reflected by the optical disk 10, and the first laser beam LB reflected by the optical disk 10 for focus control and information reproduction. A second beam splitter 30 for splitting one beam and a second beam used for tracking control, and first and second focusing lenses 32 for focusing the first and second beams, respectively.
And 34, and first and second photodetectors 36 and 38 for converting the respective beams into electrical signals.

The fixed optical unit 22 configured as described above
Is connected to a control unit 42 which is a control means via a signal cable 40 (see FIG. 2). The control unit 42 includes a data recording circuit 44 that generates a recording signal according to information input from an external host system (not shown), such as a host computer, and an objective lens switching unit 46 described later.
And an objective lens switching circuit 48 for generating a switching signal, an information reproducing circuit 50 for reproducing information recorded on the optical disc 10 from a detection signal detected through the fixed optical unit 22, and tracking of the objective lens 14a or 14b. It includes a tracking control circuit 52 for generating a tracking control signal for controlling the focus and a focus control circuit 54 for generating a focus control signal for controlling the focus of the objective lens 14a or 14b.

The laser beam LB emitted from the semiconductor laser 24 is converted into a parallel beam through the collimator lens 26, bent by 90 ° by the first beam splitter 28, and incident on the moving optical system 18 of the pickup 20. . That is, it is incident on the objective lens 14a or 14b selected through the rising mirror 16 as described later. The laser beam LB incident on the objective lens 14a or 14b is provided with a focusing property via the objective lens 14a or 14b, and is focused on the information recording surface 10a of the optical disc 10 to form a light spot.

When the optical disk device 1 is in the reproducing state, the laser beam LB guided to the optical disk 10 is the information recorded on the information recording surface 10a, that is, the minute pits 5.
6 is intensity-modulated according to the presence or absence of 6 and again the objective lens 14
a or 14b. Objective lens 14a or 1
The reflected laser beam LB returned to 4 b is guided to the fixed optical unit 22 via the rising mirror 16, passes through the first beam splitter 28, and is reflected by the second beam splitter 30 to be 2
It is divided into two and focused on the first and second photodetectors 36 and 38 via the focusing lenses 32 and 34, respectively.

The reflected laser light LB guided to the photodetectors 36 and 38 is converted into an electric signal and supplied to the tracking control circuit 52 and the focus control circuit 54 to focus control and tracking control of the objective lens 14a or 14b. Used for. The reflected laser beam LB guided to the photodetector 38 is also supplied to the information reproducing circuit 50 to reproduce the information recorded on the optical disc 10 and output the reproduction result to a host computer or the like (not shown).

In this case, the pickup 20 is controlled to move (tracking control) in the radial direction (direction of arrow A) of the optical disc 10 according to the position of the track on which the light spot on the information recording surface 10a of the optical disc 10 should be irradiated. It will be.

Next, the structure of the pickup 20 as an optical head will be described with reference to FIGS.

The pickup 20 has a carriage 60 as a moving means that is movable in the radial direction of the optical disk 10 (direction of arrow A), which is the tracking control direction, using a linear motor 74 described later as a drive source.

On both sides of the carriage 60, a plurality of (in this case, two pairs) support rollers 62, which are supported by leaf springs, are provided.
2, by rolling contact with two guide shafts 64, 64 arranged horizontally and in parallel along the radial direction of the optical disc 10, the radial direction of the optical disc 10 (arrow A Direction) is movably supported.

Further, radial coils 66, 66 are attached to both sides of the carriage 60, and the radial coils 66, 66 are fitted to the inner yokes 68, 68 which are members for forming a magnetic circuit. Has become. The inner yokes 68, 68 are in a state of being connected to outer yokes 70, 70 provided on the outer side.
Magnets 72 are attached inside the 0 and 70, respectively, and form a linear motor 74.

By supplying electric power to the radial coils 66, 66, a propulsive force (Lorentz force) is generated and the carriage 60 can be reciprocated in the tracking control direction.

FIG. 4 is a sectional view of the main part of the carriage 60. As shown in this figure, on the upper surface of the carriage 60,
A support shaft 80 as a rotation center shaft is provided in a protruding manner. Support shaft 8
0 is parallel to the rotation center axis of the optical disk 10, that is, the drive shaft 12a of the spindle motor 12 (see FIG. 3).

With the rotation center hole 82a fitted in the support shaft 80, the lens actuator 82 as a lens holding member is attached so as to be rotatable in the direction of arrow B and movable in the vertical direction (direction of arrow C). There is.

The lens actuator 82 is in the shape of a cylinder having a lens mounting flange portion 84 on the upper end side, and a rotation center hole 82a is provided in the center of the lens actuator 82 so as to vertically penetrate therethrough.

The lens mounting flange portion 84 has the first and second objective lenses 14a, 14a,
14b is in a state of being symmetrically arranged with respect to the support shaft 80 which is the rotation center axis of the lens actuator 82. By rotating the lens actuator 82 in the direction of arrow B, the first and second objective lenses 14a , 14b can be selectively interposed in the optical path of the laser light LB.

On the lower surface of the lens actuator 82 and the upper surface of the carriage 60, ring-shaped magnets 86 and 88 having polarities that magnetically repel each other, and in the embodiment, N-poles on the mutually opposing surface side are provided. The self-weight of the lens actuator 82 is offset so that the lens actuator 82 can rotate and move up and down with a small force.

A focus coil 90 is wound around an intermediate portion in the vertical direction of the lens actuator 82, and a focusing magnet 92 arranged corresponding to the focus coil 90 is mounted on a carriage 6 via a holding member (not shown).
It is fixed at 0. Then, by passing a current through the focus coil 90, the focus coil 90 can be moved in the focus control direction (direction of arrow C) to follow the vertical vibration due to the warp of the optical disc 10 or the like.

At the lower end of the lens actuator 82,
A rack 94 is formed, and the pinion 9 is attached to the rack 94.
6 is in a meshed state. The pinion 96 is attached to a drive shaft of a motor 98 attached to the carriage 60 and capable of rotating in the forward and reverse directions. When the motor 98 is driven, the lens actuator 82 is moved in the arrow B direction and in the direction opposite to the arrow B direction. It can be rotated selectively in the direction of. These constitute the lens actuator moving means 100 as the lens holding member moving means.

The lens actuator moving means 100 not only allows the first and second objective lenses 14a and 14b to be selectively interposed in the optical path of the laser beam LB, but also follows the row of pits 56 on the rotating optical disk 10. In order to do so, the objective lens 14a or 14b is moved in the direction of arrow D (see FIG. 5) orthogonal to the row of recording pits 56 on the optical disc 10 (see FIG. 5) to perform a radial movement that follows a large tracking error.

The objective lenses 14a and 14b are attached to the lens attaching flange portion 84 via the tracking control mechanism 110 having the tracking coil 112 (see FIG. 3), and follow a minute tracking error. You can do it.

The lens actuator 82 as a lens holding member and the lens actuator moving means 100 configured as described above are used to form the first and second objective lenses 14.
The objective lens switching means 46 for selectively interposing a and 14b in the optical path of the laser light LB is configured. Focus coil 90, tracking coil (not shown), motor 9 of lens actuator moving means 100
A cable (not shown) for supplying electric power to 8 is connected.

FIG. 5 schematically shows the basic structure of the optical disc device 1 which is the above-mentioned information recording / reproducing device of the present invention. The arrow E indicates the rotation direction of the optical disc 10.

The first and second objective lenses 14a and 14b are
A plurality of optical discs 10 (two in this embodiment) having different standards such as recording density, warp allowance, and substrate thickness.
It is suitable for recording and reproducing a and 10b.

For example, when the optical disc 10 is the optical disc 10a having the thick substrate 102, the first objective lens 14a suitable for the optical disc 10a is selected by the signal from the control unit 42 as shown in FIG. It is controlled so as to be interposed in the optical path of the LB. If the optical disc 10b has a thin substrate 102, as shown in FIG.
The first objective lens 14b suitable for this is selected and controlled so as to be interposed in the optical path of the laser beam LB.

Incidentally, the first and second objective lenses 14a, 14
Although b has been described as being suitable for processing a plurality of optical discs 10a and 10b (two in this embodiment) having different standards such as differences in recording density, allowable warp amount, substrate thickness, and the like. However, if the specifications of the objective lens are different during recording and reproduction on the same optical disc 10, the first objective lens 14a is used for recording and the second objective lens 14a is used for recording.
The objective lens 14b may be switched and used for reproduction.

Further, although the case where two objective lenses are provided has been described, the present invention is not limited to this, and three or more objective lenses may be provided for switching, and the point is effective when a plurality of objective lenses are provided for switching.

As described above, according to this embodiment, the type of the information storage medium storing the signal to be read is selected from the plurality of objective lenses, or the predetermined objective lens suitable for the recording / reproducing process is selected. Since it can be used as a compact and inexpensive structure, it can be used for multiple information storage media with different objective lens specifications.
Good information processing can be performed.

That is, in the first embodiment, a plurality of dedicated pickups using a dedicated objective lens adapted to each standard or specification are prepared, and the pickups are switched according to the characteristics of the optical disk. not,
By changing the rotation angle of the lens actuator 84, an objective lens suitable for recording / reproducing of the optical disk can be selected and used from the plurality of objective lenses 14a and 14b, which is small and inexpensive. Despite the configuration, excellent recording / reproducing can be performed on a plurality of optical discs 10a, 10b having different specifications of the objective lenses 14a, 14b.

Since the plurality of objective lenses 14a and 14b are arranged symmetrically with respect to the support shaft 80 which is the rotation center axis of the lens actuator 82, both objective lenses 14a and 14b are arranged.
The mass of 4b is balanced and the lens actuator 82
There is an advantage that it is easy to balance. Since the objective lenses 14a and 14b are switched using the lens actuator 82, there is also an advantage that it can be easily implemented.

Next, another embodiment of the present invention will be described. In the following embodiments, parts corresponding to those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[Second Embodiment] Referring to FIGS. 8 to 10,
A second embodiment of the present invention will be described. The same parts as those of the first embodiment described above are designated by the same reference numerals, and the duplicated description will be omitted.

FIG. 8 schematically shows the basic construction of the second embodiment, and FIGS. 9 and 10 respectively show objective lenses 14a and 14 according to the types of optical disks 10a and 10b.
The state which switched b is shown.

As is apparent from these figures, unlike the first embodiment, the second embodiment has a plurality of objective lenses 14
The a and 14b are not symmetrically provided about the rotation axis, but are arranged at positions close to each other.
Therefore, the tracking coil 4 attached to the lens actuator 82 does not use a rack or pinion.
The objective lens switching means 460 for switching the objective lenses 14a and 14b by using the tracking mechanism 115 which is composed of the magnet 5 and the magnet 47 and moves in the direction of the arrow D orthogonal to the row of recording pits 56 on the optical disk 10 to follow the tracking error. It is equipped with.

As described above, in the second embodiment, the first
Similar to the embodiment, it is possible to perform good recording / reproduction on a plurality of optical discs 10a and 10b having different specifications of the objective lenses 14a and 14b, respectively, while having a compact and inexpensive structure. .

Furthermore, a plurality of objective lenses 14a, 14b
Are arranged close to each other, the objective lens 1
Switching between 4a and 14b can be performed easily and in a short time.

Further, since the objective lenses 14a and 14b are switched by using the lens actuator 82, and the tracking mechanism 115 can be used as a switching means for the objective lenses 14a and 14b, the mechanism can be simplified. is there.

In the second embodiment as well, similar to the first embodiment, the first and second objective lenses 14a and 14b have different standards such as recording density, warp allowance, and substrate thickness. The first objective lens 14a is not limited to the one adapted to the processing of the plurality of optical discs 10a and 10b, and the first objective lens 14a is used for recording when the specifications of the objective lens are different between recording and reproducing on the same optical disc 10. As a matter of course, the two objective lenses 14b may be switched and used for reproduction, or the number of objective lenses may be three or more.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. 11 to 13. The same parts as those of the first embodiment described above are designated by the same reference numerals, and the duplicated description will be omitted.

In the third embodiment, the pickup 20 as an optical head provided with an arm type lens actuator 820 in place of the above-mentioned rotary type lens actuator 82.
It is equipped with 0.

The lens actuator 820 includes a support member 120 which is rotatable only in a direction of an arrow G (see FIGS. 12 and 13) about a support shaft 800 projecting from the carriage 60 as a rotation center axis, and objective lenses 14a and 14b. The lens holder 121 serving as a lens holding member that holds the lens holder 121 and the lens holder 121 and the support member 120 are connected to each other.
The parallel plate spring 122 movably supports 21 in the focus control direction.

By rotating the lens actuator 820 with the support shaft 800 as the center axis of rotation by the objective lens switching means 460, for example, the optical disk 10 becomes the substrate 10.
When the optical disc 10a has two thick optical discs 10a, as shown in FIG. 12, the first objective lens 14a suitable for this is selected and controlled so as to be interposed in the optical path of the laser beam LB. If the optical disc 10b has a thin substrate 102, as shown in FIG. 13, the first objective lens 14b suitable for the optical disc 10b is selected and controlled so as to be interposed in the optical path of the laser beam LB. It has become.

The objective lens switching means 460 is the support member 1
It comprises a magnet 124 attached to the magnet 20, an electromagnet 126 arranged near the magnet 124, and a polarity switching means 128 for switching the polarities of both poles of the electromagnet 126 by changing the direction of current flow.

According to the third embodiment, the objective lens is rotatable about the rotation center axis parallel to the rotation center axis of the storage medium, and the objective lens is movable in the direction of moving toward and away from the information storage medium. By changing the rotation angle of the lens actuator, it is possible to select and use a predetermined objective lens suitable for information processing from a plurality of objective lenses. For multiple information storage media with different lens specifications,
Alternatively, even when the specifications of the objective lens are different at the time of recording and at the time of reproducing, it is possible to perform good information processing, and it is possible to easily perform it because a lens actuator is used.

In the third embodiment as well, similar to the first embodiment, the first and second objective lenses 14a and 14b have different specifications such as recording density, warp allowance, and substrate thickness. The first objective lens 14a is not limited to the one adapted to the processing of the plurality of optical discs 10a and 10b, and the first objective lens 14a is used for recording when the specifications of the objective lens are different between recording and reproducing on the same optical disc 10. As a matter of course, the two objective lenses 14b may be switched and used for reproduction, or the number of objective lenses may be three or more.

FIG. 14 is a diagram schematically showing the mounting state of the first and second objective lenses 14a and 14b in the first to third examples. The first and second objective lenses 14a,
The focal lengths of the objective lenses 14a and 14b are set so that the distance between 14b and the optical disks 10a and 10b, that is, the working distance H is constant.

That is, for example, the objective lens 14a having a numerical aperture (NA) of 0.45 and the substrate 10 for the optical disc 10a having a thickness T1 of the substrate 102 for CD of 1.2 mm.
When the objective lens 14b having an objective lens numerical aperture NA of 0.6 is used for the optical disc 10b having a thickness T2 of 0.6 mm, the focal length of the objective lens 14a is f =
Set to 2.8 mm and set the focal length of the objective lens 14b to f
= 2.4 mm will be set.

As described above, if the working distance H is made constant, the servo is simplified and the optical discs 10a and 10b and the objective lenses 14a and 1 are simultaneously formed.
It also helps prevent accidents such as collisions with the 4b, and is actually extremely important in designing.

Reference numeral 103 in FIG. 14 denotes an information recording layer with a tracking guide forming the information recording surface 104.

[Fourth Embodiment] A fourth embodiment of the objective lens driving of the present invention will be described with reference to FIGS. FIG.
5 is a plan view of the objective lens driving device, FIG. 16 is a view showing a cross section of the objective lens driving device along the line AA ′ in FIG. 15 and an optical processing system, and FIG. 17 is BB ′ in FIG. FIG. 18 is a cross-sectional view of the objective lens driving device taken along the line, and FIG. 18 is a diagram showing an optical system and a signal processing system.

Disc 101 used for recording and reproducing information
(Optical disk, magneto-optical disk, etc.) is the base 102
It is held by a chucking means such as a magnet chuck with respect to the spindle motor 103 fixed to, and is stably driven by the spindle motor 103 during recording and reproduction.

The movable body 104 is arranged at a position close to the bottom of the disk 101. The movable body 104 is the first
It is composed of a movable body 105 and a second movable body 106, and is supported so as to be movable in the radial direction and the thickness direction of the disk 101, as will be described later.

The first movable body 105 includes a substantially elliptical plate blade 105a facing the surface of the disk 101,
It consists of a cylindrical coil bobbin 105b fixed to the lower part of the blade 105a. A sliding bearing 105c is provided at the center of the blade 105a and the coil bobbin 105b.
Is provided.

In the plain bearing 105c, the rotary shaft 107, which is fixed to the second movable body 106 at one end and is erected, has a minute gap (1
The sliding bearing mechanism (shaft sliding mechanism) is configured by being inserted and fitted through (0 micron or less). Then, the first movable body 1
Reference numeral 05 is capable of rotational movement about the rotation axis 107 and translational movement in the axial direction.

On the blade 105a, a plurality of, here, two objective lenses 108a and 108b are fixed separately. These objective lenses 108a and 108b are selected to have different optical characteristics (for example, the numerical aperture (NA) of the objective lens 108a is 0.45 and the numerical aperture of the objective lens 108b is 0.6). The mounting positions of these two objective lenses 108a and 108b are set so that the center of gravity of the entire mass of the first movable body 105 substantially coincides with the rotation axis 107 and the diameter passing through the rotation axis 107 from the central axis. They are equidistant. That is, the first movable body 105 has a structure in which the weight is balanced with respect to the rotation shaft 107 by the two objective lenses 108a and 108b.

A focus coil 109 is wound around the coil bobbin 105b. Focus coil 1
On the periphery of 09, two rectangular tracking coils 200a and 200b wound in a plane are attached at predetermined intervals. A magnetic circuit 112a composed of permanent magnets 110a and 110b and yokes 111a and 111b is provided on the second movable body 106 around the focus coil 109 and the tracking coils 200a and 200b in a positional relationship just symmetrical with respect to the rotation axis 107. ，
112b is provided, and the focus coil 109 and the tracking coil 20 are provided via a magnetic gap of a predetermined length.
0a and 200b are arranged to face the focus coil 109 and the tracking coils 200a and 200b.
A magnetic field is applied to. The two magnetic circuits 112a and 112b have the same structure, and the magnetizing directions of the permanent magnets 110a and 110b coincide with the thickness direction of the magnetic gap.

When the focus coil 109 is energized and a magnetic flux is received from the magnetic circuits 112a and 112b, a Lorentz force is generated, and the first movable body 105 moves in the thickness direction of the disk 101 (axial direction of the rotary shaft 107). It is slightly translated. Further, the tracking coils 200a and 200b are energized and the magnetic circuit 11 is
The Lorentz force is generated by receiving the magnetic flux from 2a and 112b, and the first movable body 105 is slightly rotated in the radial direction of the disk 101 (around the rotation axis 107).

On the tracking coils 200a and 200b at positions separated by 180 ° around the coil bobbin 105b, two magnetic bodies 201a and 201 made of iron pieces or the like are provided.
b is provided. The magnetic bodies 201a and 201b are 2
The objective lenses 108a and 108b are attached at a position separated by 90 ° from each other in a symmetrical relationship with respect to the rotation axis 107. One objective lens 108 has an optical path 124 (described later).
When inside, these magnetic bodies 201a and 201b are arranged just opposite to the magnetic gaps of the magnetic circuits 112a and 112b.

On the other hand, the second movable body 106 is connected to the first movable body 105 via the rotating shaft 107, as described above. A pair of radial coils 113a and 113b are attached to both ends of the second movable body 106 at exactly the same distance from the position of the center of gravity of the second movable body 106. A magnetic field is applied to the radial coils 113a and 113b from the radial magnetic circuits 114a and 114b fixed to the base 102.

The radial magnetic circuits 114a and 114b are
Back yokes 115a and 115b and center yoke 11
6a, 116b and permanent magnets 117a, 117b. The radial coils 113a, 113b are composed of center yokes 116a, 116b and permanent magnets 117a, 117b.
It is movably inserted in the magnetic gap defined by and. The two radial magnetic circuits 114a and 114
b has the same structure and permanent magnets 117a and 117a
The direction of magnetization of b coincides with the thickness direction of the magnetic gap.

Two to four slide bearings 119a and 119b are provided on the left and right of the second movable body 106, and two guide rails 118a and 11 are inserted in the slide bearings.
8b are arranged in parallel. The guide rail 118
Both ends of a and 118b are fixed to the base 102.
The second movable body 106 has these guide rails 118a, 11a.
It is movably supported along 8b.

The Lorentz force is generated when the radial coils 113a and 113b are energized and the magnetic flux is received from the radial magnetic circuits 114a and 114b.
The movable body 106 is translationally driven in the radial direction of the disk 101.

The magnetic gap width of the radial magnetic circuits 114a and 114b is such that the second movable body 106 has the guide rail 11a.
8a and 118b are formed to be long enough in the same direction so that they can be moved by a required distance in the longitudinal direction, in other words, the objective lenses 108a and 108b can be moved in the radial direction from the outermost circumference to the innermost circumference of the disk 101. Has been done.

Regarding the optical system and signal processing system of the apparatus,
This will be described with reference to FIGS. 16 and 18.

The laser light for irradiating the disc 101 is generated by the optical unit 120 which is fixed to the lower part of the movable body 104 and is movable integrally with the movable body 104. The laser beam LB emitted from the semiconductor laser 121 in the optical unit 120 is converted into a parallel beam via the collimator lens 122, and is converted into a parallel beam by the first beam splitter 123a.
It is bent by 0 ° and guided into the second movable body 106 from the radial direction of the disc 101. At the bottom of the second movable body 106, an optical path (specifically, space) 1 for introducing the laser light LB 1
41 is provided, and the laser beam LB passes through this optical path 141.
Objective lens 108 (108a or 108b) passing through the inside
Is incident on. The laser beam LB incident on the objective lens 108 is given a predetermined focusing property and is focused on the information storage surface of the disc 101.

Here, when the system is in the information reproducing state, the laser beam LB guided to the disc 101 is intensity-modulated according to the information recorded on the information storage surface, that is, the presence or absence of the minute pits. It is returned to the objective lens 108 again. Reflected laser light LB returned to the objective lens 108
Are guided to the fixed optical unit 120 again through the optical path 141. Then, it passes through the first beam splitter 123a, is divided into two paths by the second beam splitter 123b, and is focused on the first photodetector 125a and the second photodetector 125b via focusing lenses 124a and 124b, respectively. It

The reflected laser light LB guided to the photodetectors 125a and 125b is converted into an electric signal and supplied to the tracking control circuit 127 and the focus control circuit 128 provided in the control unit 126. The signals generated by the tracking control circuit 127 and the focus control circuit 128 are the objective lenses 108 (108a, 108a).
The focus offset signal and tracking offset signal of b) are used for focus direction control and tracking direction control.

By using the focus offset signal and the tracking offset signal, the positional deviation (focus deviation) of the objective lens 108 in the focusing direction is detected, and the current value given to the focus coil 109 is controlled so as to correct this positional deviation. . Further, the tracking offset signal is used to detect the positional deviation of the objective lens 108 in the tracking direction, and the current value given to the tracking coils 100a and 100b is controlled so as to correct the positional deviation.

The reflected laser light LB guided to the photodetector 125b is also supplied to the information reproducing circuit 129. This information is various information recorded on the disc 101, is sent to a host system (for example, a personal computer, etc.) not shown, and is output from the display as characters, still images, and moving images, and from the speaker as music and voice. In this case, the second movable body 106 follows the track of the information storage surface of the disc 101 and is controlled to move in the radial direction of the disc 101 by large drive or minute drive.

In the control unit 126, the recording signal generating circuit 130 for generating a recording signal according to the information input from an external host system (not shown) (for example, a personal computer) and one of the objective lenses 108a and 108b are described above. The objective lens switching circuit 131 that generates a signal for controlling the rotation of the first movable body 105 so as to be arranged in the optical path 124 of the laser light LB is included.

Next, the two objective lenses 108a and 108
The switching of b will be described.

The disc 101 that can be used in the apparatus of the present invention is not limited to one type of disc as in the conventional case, and the disc recording density, the warp allowable amount, the difference in the disc substrate thickness, etc. It is possible to use a plurality of different disks. For example, it is possible to use not only a CD-ROM disc but also an MO disc or a PC disc. Then, the two objective lenses 10
As for 8a and 108b, those adapted to the processing of usable disks are prepared. Further, the objective lens 108
A and 108b may be switched for each recording / reproducing process.

For example, in the case of using a disk which requires a small spot diameter of the laser light LB, an objective lens having a large numerical aperture (NA) is selected and it is necessary to increase the spot diameter of the laser light LB. When using a disc, an objective lens with a small numerical aperture (NA) is selected.

The user of the apparatus mounts the target disk 101 on the spindle motor 103, and the disk 1 is transferred from the host system (eg personal computer).
Type 01 (for example, information as a disc having a different standard such as a CD-ROM disc and a PC disc) is input. This input signal is sent to the objective lens switching circuit 131, and control is performed so as to move the corresponding objective lens 108 on the optical path 141 of the laser light LB.

When the objective lens 108 corresponding to the mounted disc 101 is already on the optical path 141, it is not necessary to move the first movable body 105 largely.
However, when the necessary objective lens 108 is located 180 ° apart from the rotation axis 107, a large current is momentarily applied to the tracking coils 200a and 200b.

The current applied at this time is the first movable body 1.
Unlike that for minutely driving and controlling 05, a current value necessary for guiding the first movable body 105 to the optical path 141 in a short time with a large acceleration is supplied.

When the first movable body 105 is rotationally accelerated and the predetermined objective lens 108 reaches the optical path 141, the magnetic bodies 201a and 201b reach the positions just opposite to the magnetic gaps of the magnetic circuits 112a and 112b. Here, the magnetic bodies 201a and 201b are the magnetic circuits 112a and 1a.
In the state where the magnetic bodies 201a and 2b face each other,
01b receives the largest magnetic attraction force from the magnetic circuits 112a and 112b. Therefore, if a large current is momentarily applied to the tracking coils 200a and 200b, the first movable body 105 can be moved to the objective lens 108 without applying a special current for deceleration stop.
When it reaches the optical path 124, it is surely decelerated and stopped and positioned.

According to the objective lens driving device of the present invention which operates as described above, since two objective lenses can be switched and used according to the standard or specification of the disc, it conforms to the standard or specification of the disc. It is not necessary to prepare a plurality of dedicated (separate) objective lens driving devices. Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since a plurality of magnetic circuits and magnetic bodies are used, the magnetic attraction force acting on the first movable body can be easily balanced. Therefore, the rotating shaft 107
Since the plain bearings 119a and 119b are not pressed against (?), The first movable body 105 and the rotary shaft 10
The frictional force between the first movable body 7 and the so-called “twist” can be reduced as much as possible, and the rotational movement and translational movement of the first movable body can be smoothly performed.

Further, since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, so-called "twisting" can be reduced as much as possible, as described above.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Fifth Embodiment] A fifth embodiment of the objective lens driving of the present invention will be described with reference to FIG. In addition,
In each of the following embodiments, the same components as those in the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted.

The feature of this embodiment is that the number of objective lenses mounted on the first movable body is increased to three. That is, the blade 105a of the first movable body 105 has a shape having protrusions at three positions separated by 120 ° with respect to the rotating shaft 107, and the objective lens 1 is provided on each of these protrusions.
08a, 108b, 108c are fixedly arranged. The second movable body 106 is also provided with three magnetic circuits 112a, 112b, 112c in a symmetrical relationship with the rotating shaft 107.
Has been fixed. Objective lenses 108a, 108b, 1
08c and magnetic circuits 112a, 112b, 112c
Are arranged at equal intervals on the same circumference centered on the rotation shaft 107. Further, the coil bobbin 105b has three tracking coils 200a, 200b, 200c.
And three magnetic bodies 201a, 201 composed of iron pieces and the like.
b and 201c are attached at equal intervals.
(Note that the magnetic bodies 201a, 201b, and 201c are the same as those in FIG.
It is affixed in a state like. The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs the same slide bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description will be given here.

According to this embodiment having such a structure, the focus coil 109 and the tracking coil 200a,
The magnetic gap that gives a magnetic field to 200b and 200c is
There are the same number of objective lenses 108a, 108b, and 108c, and the magnetic gaps are also located at equal intervals on the same circumference with the rotation axis 107 as the center. First movable body 10
5. Magnetic bodies 201a, 201b, 20 that determine the neutral position of 5
Since the same number of the objective lenses 108a, 108b, 108c as 1c are attached, the predetermined objective lenses 108a, 108b, 1 are controlled by the same control method as in the fourth embodiment.
08c can be reliably positioned on the optical path 141.

Therefore, even in the objective lens driving device of the present embodiment, three objective lenses can be switched and used according to the disc standard and specifications, and therefore, it can be used exclusively for the disc standard and specifications. It is not necessary to prepare a plurality of (separate) objective lens driving devices. Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since a plurality of magnetic circuits and magnetic bodies are used, the magnetic attraction force acting on the first movable body can be easily balanced. Therefore, the slide bearing is not pressed against the rotary shaft, and the frictional force between the first movable body and the rotary shaft, so-called "twisting" can be reduced as much as possible, and the rotational movement and translational movement of the first movable body can be reduced. Is done smoothly.

Since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, so-called "twisting" can be reduced as much as possible in the same manner as described above.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Sixth Embodiment] The sixth embodiment of the objective lens driving of the present invention will be described with reference to FIG.

The feature of this embodiment is that the number of objective lenses mounted on the first movable body is four. That is, the blade 105 a of the first movable body 105 has a shape having protrusions at four positions separated by 90 ° with respect to the rotating shaft 107, and the objective lens 10 is provided at each of these protrusions.
8a, 108b, 108c and 108d are fixedly arranged. In addition, the second movable body 106 also includes the rotary shaft 10
The four magnetic circuits 112a, 11 are symmetrical with respect to
2b, 112c and 112d are fixed. The objective lenses 108a, 108b, 108c, 108d and the magnetic circuits 112a, 112b, 112c, 112d are arranged at equal intervals on the same circumference with the rotation axis 107 as the center. Further, the coil bobbin 105b includes four tracking coils 200a, 200b, 200c, 200d.
And four magnetic bodies 201a, 201 made of iron pieces or the like.
b, 201c and 201d are attached at equal intervals. (Note that the magnetic materials 201a, 201b, 201
c and 201d are attached in a state as shown in FIG. The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs the same slide bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description thereof will be omitted here.

According to this embodiment having such a configuration, the focus coil 109 and the tracking coil 200a,
The magnetic gaps 200b, 200c, and 200d that apply a magnetic field to the objective lenses 104a, 104b, 104c,
There are the same number as 104d, and these magnetic gaps are also located at equal intervals on the same circumference centered on the rotation axis 7. Magnetic body 2 that determines the neutral position of the first movable body 105
01a, 201b, 201c and 201d are the objective lens 1
Since the same number as 08a, 108b, 108c, 108d is attached, a predetermined objective lens 108a, 108b, 108c,
108d can be reliably positioned on the optical path 141.

Therefore, even in the objective lens driving device of the present embodiment, four objective lenses can be switched and used in accordance with the disc standards and specifications, and thus the disc standards and specifications are adapted. It is not necessary to prepare a plurality of dedicated (separate) objective lens driving devices. Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since a plurality of magnetic circuits and magnetic bodies are used, the magnetic attraction force acting on the first movable body can be easily balanced. Therefore, the slide bearing is not pressed against the rotary shaft, and the frictional force between the first movable body and the rotary shaft, so-called "twisting" can be reduced as much as possible, and the rotational movement and translational movement of the first movable body can be reduced. Is done smoothly.

Since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, so-called "twisting" can be reduced as much as possible.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

Further, in the above-mentioned three embodiments, the number of objective lenses is 2, 3, and 4, respectively, but the present invention is not limited to these numbers, and a plurality of objective lenses may be used. If the same control is performed by using the objective lens (1), the required effect can be obtained.

Regarding the relationship among the numbers of objective lenses, magnetic bodies, and magnetic gaps, for example, “6 objective lenses, 2 magnetic gaps, 6 magnetic bodies”, “6 objective lenses, 3 magnetic gaps, magnetic “6 bodies”, “6 objective lenses, 6 magnetic gaps, 6 magnetic bodies”, “6 objective lenses, 2 magnetic gaps, 3 magnetic bodies”, etc. It is preferable that the number of the magnetic gaps and the number of the magnetic gaps have a divisor relationship. It should be noted that a plurality of magnetic bodies may be attached at substantially the same position so as to face one magnetic circuit.

By adopting such a combination, it becomes possible to provide as many neutral positions as the number of objective lenses, which are determined by the magnetic attraction between the magnetic body and the magnetic gap.
Moreover, the magnetic attraction forces of the magnetic body and the magnetic gap cancel each other out, and the frictional force between the first movable body and the rotating shaft, so-called “twisting” can be further reduced.

[Seventh Embodiment] Next, referring to FIG.
A seventh embodiment of the objective lens driving device of the present invention will be described with reference to FIG. 21A is a plan view of the seventh embodiment, and FIG. 21B is a perspective view showing the arrangement of the tracking coil and the focus coil.

The feature of this embodiment is that the shape of the first movable body is different from those of the above-mentioned embodiments. That is, the shape of the blade 105a forming a part of the first movable body 105 is circular, and the diameter of the coil bobbin 105b is slightly larger. The diameter of the blade 105a and the diameter of the coil bobbin 105b are substantially equal, and the first movable body 105 has a tubular shape as a whole.

Therefore, the magnetic circuits 112a, 1 facing the focus coil 109 and the tracking coils 200a, 200b attached to the coil bobbin 105b.
The shape of 12b is also formed with a larger curvature than that of each of the above-described embodiments.

Further, a cutout is provided in a part of the first movable body 105, and the magnetic bodies 201a, 201 are formed in this cutout.
b are buried respectively.

The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs a sliding bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description thereof will be omitted here.

Also in this embodiment having such a structure, the same operation as that in each of the above-described embodiments can be performed and the same effect can be obtained.

Since the two objective lenses can be switched and used according to the disc standard or specification, a dedicated (separate) device adapted to the disc standard or specification can be used.
It is not necessary to prepare a plurality of objective lens driving devices.
Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since a plurality of magnetic circuits and magnetic bodies are used, it is easy to balance the magnetic attraction force acting on the first movable body. Therefore, the sliding bearing is not pressed against the rotating shaft, and the frictional force between the first movable body and the rotating shaft, so-called “twisting” can be reduced as much as possible, and the rotational movement and translational movement of the first movable body can be reduced. Is done smoothly.

Since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, so-called "twisting" can be reduced as much as possible.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Eighth Embodiment] Next, an eighth embodiment of the objective lens driving device of the present invention will be explained with reference to FIG. The feature of this embodiment is that, like the fifth embodiment, the number of objective lenses mounted on the first movable body is three.
That is, the first movable body 105 is provided with the objective lens 108 at each of three positions separated by 120 ° with respect to the rotation shaft 107.
a, 108b, 108c are fixedly arranged. Also,
The second movable body 106 has three magnetic circuits 112a, 112b, 112 which are also symmetrical with respect to the rotation axis 107.
c is fixed. These objective lenses 108a, 10
8b, 108c and magnetic circuits 112a, 112b, 1
12c are arranged at equal intervals on the same circumference with the rotation shaft 107 as the center. Further, three magnetic bodies 200a, 200b, 200c are attached to the first movable body 5, and three magnetic bodies 201a, 201b, 201c made of iron pieces or the like are embedded at equal intervals.

The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs a sliding bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description thereof will be omitted here.

Also in this embodiment having such a structure, the same operation as that in each of the above-described embodiments can be performed and the same effect can be obtained.

Since the three objective lenses can be switched and used according to the disc standards and specifications, a dedicated (separate) device adapted to the disc standards and specifications can be used.
It is not necessary to prepare a plurality of objective lens driving devices.
Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since a plurality of magnetic circuits and magnetic bodies are used, the magnetic attraction force acting on the first movable body can be easily balanced. Therefore, the sliding bearing is not pressed against the rotating shaft, and the frictional force between the first movable body and the rotating shaft, so-called “twisting” can be reduced as much as possible, and the rotational movement and translational movement of the first movable body can be reduced. Is done smoothly.

Further, since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, so-called "twisting" can be reduced as much as possible in the same manner as described above.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Ninth Embodiment] Next, a twenty-third embodiment of the objective lens driving device of the present invention will be explained with reference to FIG.

The feature of this embodiment is that, as in the sixth embodiment, the number of objective lenses mounted on the first movable body is four. That is, the blade 105a of the first movable body 105 has the objective lenses 108a, 108b, 10 at four positions separated by 90 ° with respect to the rotating shaft 107, respectively.
8c and 108d are fixedly arranged. The second movable body 106 has four magnetic circuits 112a, 112b, 112c, 11 which are also symmetrical with respect to the rotating shaft 107.
2d is fixed. These objective lenses 108a, 1
08b, 108c, 108d and the magnetic circuit 112a,
112b, 112c, 112d are arranged at equal intervals on the same circumference with the rotation shaft 107 as the center. Further, the coil bobbin 105b has four tracking coils 2
00a, 200b, 200c, 200d are attached, and four magnetic bodies 201a, 201b, 20 made of iron pieces or the like
1c and 201d are embedded at equal intervals.

The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs a sliding bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description thereof will be omitted here.

Also in this embodiment having such a structure, the same operation as that in each of the above-described embodiments can be performed and the same effect can be obtained.

Since the four objective lenses can be switched and used according to the disc standard and specifications, a dedicated (separate) device adapted to the disc standard and specifications can be used.
It is not necessary to prepare a plurality of objective lens driving devices.
Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since a plurality of magnetic circuits and magnetic bodies are used, it is easy to balance the magnetic attraction force acting on the first movable body. Therefore, the sliding bearing is not pressed against the rotating shaft, and the frictional force between the first movable body and the rotating shaft, so-called “twisting” can be reduced as much as possible, and the rotational movement and translational movement of the first movable body can be reduced. Is done smoothly.

Further, since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, so-called "twisting" can be reduced as much as possible, as described above.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Tenth Embodiment] Next, a tenth embodiment of the objective lens driving device of the present invention will be described with reference to the plan view of FIG. 24 and the sectional view of FIG.

The feature of this embodiment is that the shape of the first movable body is different from those of the above-mentioned embodiments. That is, elliptical holes 220a and 220b are provided at two locations near the outer periphery of the first movable body 105. Where the hole 22
The positions where 0a and 220b are formed are symmetrical with respect to the rotation axis 107, and the objective lenses 108a and 108b
It is formed at a position exactly 90 ° apart from b.

The holes 220a, 220 are provided in the second movable body.
The center yokes 221a and 221b inserted in b are fixed, and the permanent magnets 110a and 110b and the yoke 111 are fixed.
Magnetic circuits 112a and 112b are formed by a and 111b and center yokes 221a and 221b. As shown in FIG. 25, the axial height of the center yokes 221a and 221b is equal to that of the blade 105a of the first movable body 105.
It is formed so as to slightly project from the lower surface (for example, about 0.5 mm). Also, the holes 220a, 220
The rotation direction length of b is the same as that of the center yokes 221a and 221.
It is formed to be slightly longer than the length of b in the rotation direction.

The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs a sliding bearing mechanism as in the fourth embodiment.

In this embodiment having such a structure, the structure and operation of the second movable body 106 are almost the same as those in the fourth embodiment, but when the first movable body 105 is largely moved in the tracking direction. The operation of the first movable body 105 is different. That is, in the state of FIG. 25, the first movable body 105
If you try to move the
The center yokes 221a and 221 are connected to the center yokes 221a and 2
21b come into contact with each other, and the required amount of rotation cannot be obtained.
Therefore, when moving greatly in the tracking direction, first, the focus coil 109 is urged to first move the first movable body 10.
5 is slightly moved in the focus direction to a position slightly higher than 0.5 mm described above. Then, the tracking coils 200a and 200b are energized to perform tracking drive. After the rotation drive to the required position,
The first movable body 1 is released by releasing the bias of the focus coil 109.
05 is lowered and the center yokes 221a and 221b are inserted into the holes 220a and 220b. Such a series of operations is performed by the control unit 126 in the signal processing system of FIG.
It is realized by giving a part of the output of the objective lens switching circuit 131 in the inside to the focus control circuit 128 as well as the tracking control circuit 127.

By adopting such a structure and operation, the axial height of the first movable body 105 (in particular, the portion of the blade 105a) can be sufficiently reduced, and the entire apparatus can be made thin. It becomes possible.

When the objective lens 104 cannot be positioned on the optical path 141 because the first movable body 105 is rotated more than necessary, the holes 220a and 220b come into contact with the center yokes 221a and 221b. Further rotation of the first movable body 105 can be prevented. That is, the function of the stopper is realized by the holes 220a and 220b and the center yokes 221a and 221b. Therefore, even if the first movable body 105 rotates more than necessary, the objective lens 104 can be quickly positioned in the optical path 124.

A cushioning material such as rubber is arranged on the contact surface between the holes 220a and 220b and the center yokes 221a and 221b, or the contact surfaces are in contact with each other (for example, both contact surfaces are flat). May be formed,
Thereby, the objective lenses 104a and 104b, the focus coil 109, and the tracking coils 200a and 200
It is possible to minimize the influence of vibrations that act on b and the like during a collision.

Also in this embodiment having such a structure, the two objective lenses can be switched and used according to the standard or specification of the disc, and therefore, a dedicated ( It is not necessary to separately prepare a plurality of objective lens driving devices. Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, the first movable body is balanced around the rotation axis. Therefore, so-called "twisting" between the first movable body and the rotation shaft can be reduced as much as possible, and thus the minute rotational movement and the minute translational movement of the first movable body can be smoothly performed.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Eleventh Embodiment] Next, an eleventh embodiment of the objective lens driving device of the present invention will be explained with reference to FIG.

The characteristic point of this embodiment is that, like the fifth embodiment, the number of objective lenses mounted on the first movable body is three. That is, in the first movable body 105, the objective lenses 108a, 108b, and 108c are arranged at three positions separated by 120 ° with respect to the rotation shaft 107, respectively.
Further, holes 220a, 220b, 220c are provided. In addition, the second movable body 106 also has a rotary shaft 107.
The three magnetic circuits 112a, 112 are symmetrical to each other.
b, 112c are fixed, and center yokes 221a, 221
21b and 221c are inserted into the holes 220a, 220b and 220c. These objective lenses 108a, 108
b, 108c and magnetic circuits 112a, 112b, 11
2c are arranged at equal intervals on the same circumference with the rotation shaft 107 as the center. Further, the first movable body 105 has three tracking coils 200a, 200b, 200c.
And three magnetic bodies 201a, 201 composed of iron pieces and the like.
b and 201c are attached at equal intervals.

The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs a sliding bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description thereof will be omitted here.

Also in this embodiment having such a structure, the same operation as that in the above-mentioned tenth embodiment can be performed and the same effect can be obtained.

Since the three objective lenses can be switched and used according to the disc standards and specifications, a dedicated (separate) device adapted to the disc standards and specifications can be used.
It is not necessary to prepare a plurality of objective lens driving devices.
Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, the first movable body is balanced around the rotation axis.
Therefore, so-called "twisting" between the first movable body and the rotation shaft can be reduced as much as possible, and thus the minute rotational movement and the minute translational movement of the first movable body can be smoothly performed.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

[Twelfth Embodiment] Next, the twelfth embodiment of the objective lens driving device of the present invention will be explained with reference to FIG.

The characteristic point of this embodiment is that the sixth embodiment (see FIG.
As in 0), the number of objective lenses mounted on the first movable body is four. That is, the first movable body 1
The blade 105a of No. 05 is 90
The objective lenses 108a and 10 are respectively provided at four positions separated from each other.
8b, 108c, 108d are fixedly arranged, and the hole 2
20a, 220b, 220c, 220d are provided. In addition, the second movable body 106 also has a rotary shaft 107.
The four magnetic circuits 112a and 112 are symmetrical to each other.
b, 112c, 112d are fixed, and the center yoke 2
21a, 221b, 221c, 221d are holes 220a,
It is inserted in 220b, 220c, 220d. These objective lenses 108a, 108b, 108c, 108d
And magnetic circuits 112a, 112b, 112c, 112
d are arranged at equal intervals on the same circumference centered on the rotation shaft 107. Further, the coil bobbin 105b has 4
Number of tracking coils 200a, 200b, 200
c, 200d, and four magnetic bodies 201 composed of iron pieces
a, 201b, 201c, 201d are embedded at equal intervals.

The basic structure for movably supporting the first movable body 105 in the focus direction and the radial direction employs the sliding bearing mechanism as in the fourth embodiment. Further, since the structure and operation of the second movable body 106 are the same as those of the fourth embodiment, illustration and description thereof will be omitted here.

Also in this embodiment having such a structure, the same operation as that of the above-mentioned tenth embodiment can be performed and the same effect can be obtained.

Since four objective lenses can be switched and used in accordance with the disc standard or specification, a dedicated (separate) device adapted to the disc standard or specification can be used.
It is not necessary to prepare a plurality of objective lens driving devices.
Therefore, an objective lens driving device that can handle various kinds of information satisfactorily with only one device is provided.

Since the objective lenses are positioned so that the center of gravity of the first movable body substantially coincides with the rotation axis, the first movable body is balanced around the rotation axis. Therefore, the frictional force between the first movable body and the rotary shaft, so-called “twisting” can be reduced as much as possible, and therefore the minute rotational movement and the minute translational movement of the first movable body are smoothly performed.

Even if these objective lenses are arranged symmetrically with respect to the rotation axis or arranged at equal intervals around the rotation axis, the same effect as above can be expected.

Furthermore, the above-mentioned fifth, sixth, eighth, ninth, eleventh,
Regarding the twelfth embodiment, a counterweight may be arranged instead of the objective lens on the first movable body. This is apparent from the plan views of the apparatus shown in FIGS. 28A, 28B, and 28C, in which the two objective lenses 108a and 108b are included.
And one counter weight 222 is arranged so that the center of gravity of the first movable body 105 substantially coincides with the rotation shaft 107. Specifically, the two objective lenses 108
The mass is adjusted by providing a counterweight 222 having a mass equivalent to the average value of the masses of a and 108b. Note that the other structures are the same as the above fifth, eighth, and first.
This is the same as in the first embodiment.

Similarly, in FIGS. 28D, 28E and 28F, three objective lenses 108a, 108b, 108c and 1 are used.
The first movable body 10 is provided by arranging the counter weights 222.
The center of gravity of No. 5 is configured to substantially coincide with the rotation axis 107. In addition, other structures are the same as those in the above sixth, ninth, and first.
This is the same as the second embodiment.

29 (a), (b), and (c), two objective lenses 108a and 108b and one counter weight 222a and 222b are arranged, and the first movable body 10 is arranged.
It is disclosed that the position of the center of gravity of 5 substantially coincides with the rotation axis 107. Also in this case, the other structures are the same as those of the sixth, ninth and twelfth embodiments.

According to these modified examples, the same number of objective lenses can be attached as compared with the fourth to twelfth examples, but the same effect can be expected.

Further, regarding FIGS. 28 (b) and 28 (d),
A modified example of the tracking drive of the first movable body 105 as described below can also be adopted.

In the apparatus shown in FIGS. 30 (a) and 30 (b), the flexible printed circuit board 2 is viewed from the side surface of the first movable body 105.
23 has been extended. One end of the flexible printed board 223 is fixed to the first movable body 105, and the other end thereof is erected on the second movable body 106.
It is fixed to 4. Flexible printed circuit board 223
Is sufficiently long in consideration of the displacement caused by the rotation of the first movable body 105. The flexible printed circuit board 223 has a role of supplying current to the focus coil 109 and the tracking coil 200, for example, and is guided to the control system via the guide plate 224 and the second movable body 106. In addition, the first movable body 10
The side surface 5 and the inner surface of the guide plate 224 both form a concentric circle about the rotation shaft 107, and the gap length between them is constant.

Further, the flexible printed board 223 is deformed into a U shape, and the first movable body 105 and the guide plate 2 are
A predetermined pressure (pressing force) is always applied to 24 and. Even if the rotation angle of the first movable body 105 changes, the direction of this pressing force keeps the first movable body 105 constantly rotating the rotary shaft 10
It will urge in the direction of 7. Therefore, no pressure is applied in the rotation direction of the first movable body 105, and therefore,
No unnecessary restoring force is generated when the first movable body 105 rotates, and there is no risk of adversely affecting tracking control.

With the above-mentioned structure, the wiring required for supplying the current to the focus coil 109 and the tracking coil 200 can be laid easily and effectively.

Further, as in the apparatus shown in FIGS. 31 (a) and 31 (b), the movable body 1 provided with two objective lenses 108a and 108b and two counterweights 222a and 222b.
The same effect can be expected for 05 as well. In this example, the rotation angle of the first movable body 105 required to switch the objective lenses 108a and 108b is 9
The angle is 0 °, and the amount (angle) of movement of the flexible printed circuit board 223 is 45 °, but the flexible printed circuit board 223 is also moved to the magnetic circuits 112a, 112b, 112.
c, 112d (provided at intervals of about 90 °), it becomes possible to install the magnetic circuit 112a, 1d.
12b, 112c and 112d do not become obstacles.

Also in the case of this example, FIG.
The same effect as the modification shown in (b) can be expected.

[Thirteenth Embodiment] Next, a thirteenth embodiment of the objective lens driving device of the present invention will be described with reference to FIGS. 32 to 35. Here, FIG. 32 is a plan view of the objective lens driving device, FIG. 33 is a cross-sectional view of the first movable body along the line AA ′ in FIG. 32, and FIG. 34 is a line BB ′ in FIG. 32 is a cross-sectional view of the objective lens driving device, and FIG. 35 shows CC ′ in FIG.
It is sectional drawing along the line.

The objective lens driving device of the present embodiment is slightly different from the above-mentioned embodiments in the shape of each constituent element. Hereinafter, these will be described in detail.

The first movable body 105 is provided with blades 105a having convex portions at two locations around the rotary shaft 107. The two objective lenses 108a and 108b are arranged so as to project from the blade 105a at two positions that are exactly 90 ° apart from these two convex portions.

Here, as shown in FIG. 33, the objective lens 108a and the objective lens 108b are the same as those of the rotary shaft 107.
The mounting position is different in the axial direction. here,
The objective lens 108a located closer to the disc 101 has a larger numerical aperture (NA), and the objective lens 108b located farther from the disc 101 has a smaller numerical aperture (NA).

A rotary bearing 105d is fixed to the center of the blade 105a, and a rotary shaft 107 is engaged with the rotary bearing 105d. As a result, the rotating shaft 107
The rotational movement of the blade 105a around the center is allowed. A circumferential groove is formed in the vicinity of the center of the rotating shaft 107 in the axial direction, so that the blade 105a is prevented from translational movement in the axial direction of the rotating shaft 107.

The rotating shaft 107 is rotatably fitted to one end of each of the leaf springs 231a and 231b at its upper and lower ends. The two leaf springs 231a and 231b form a parallel leaf spring mechanism arranged in parallel, and the other end has a fixing member 2
It is fixed to the second movable body 106 via 32. Therefore, the first movable body 105 is capable of translational movement in the axial direction of the rotating shaft 107 while being suspended from the second movable body 106 by the parallel leaf springs 231a and 231b. The fixing member 232 is formed by the parallel plate springs 231a and 231.
It is interposed as a member for maintaining the parallelism of 31b.

The manufacturing method of the rotary bearing 105d is as follows. A resin such as plastic is outsert-molded on the rotary shaft 107, and a rotary bearing 105d is formed by using a clearance formed by a difference between a shrinkage ratio of the resin at the time of molding and a shrinkage ratio of the rotary shaft 107 as a minute gap. There is. By such a manufacturing method, the rotary bearing 105d is provided with a small amount of backlash and a good signal in which the aberration due to the inclination of the objective lens is hardly generated.

The second movable body 106 has the same structure as that of the first embodiment, and the operation thereof is also the same, so that the description thereof will be omitted here.

Here, the blade 105a is made of a rare earth or neodymium magnet (or a plastic magnet thereof) and is magnetized in the direction from the rotating shaft 107 toward the convex portion. And this blade 105
An annular yoke 2 formed in a substantially square ring shape around a.
33 are provided, and the cylindrical tracking coils 200 a and 200 b and the booster coil 23 are wound around the annular yoke 233 at the center of each side thereof.
4a and 234b are arranged alternately. In the neutral state shown in FIG. 32, the convex portion of the blade 105a has tracking coils 200a and 200b and a booster coil 23.
4a and 234b. Further, on the surfaces of the tracking coils 200a and 200b, rectangular focus coils 109a and 1b wound in a plane are provided.
09b is attached. Tracking coil 200
The relationship between a, 200b and the focus coils 109a, 109b is as shown in FIG. 35 (a sectional view taken along the line CC 'in FIG. 32). The annular yoke 233 is fixed to the second movable body 106 via the fixing member 232.

According to this embodiment having such a structure, the blade 105a itself is a magnetic body and forms a part of a magnetic circuit. Therefore, the focus coils 109a and 109
By energizing b, the tracking coil 200a,
By energizing 200b, Lorentz force is generated, and the first movable body 105 is finely driven in the thickness direction and the radial direction of the disc 101.

Here, in this embodiment, the parallel leaf spring 231 is used.
a and 231b are used, and therefore, when the first movable body 105 moves in the focus direction, the parallel leaf spring 2
31a and 231b are modified so that the objective lenses 108a and 1
08b moves without impairing the parallelism of the optical axis.

The movement of the first movable body 105 in the tracking direction is performed by rotating the first movable body 105 around the rotating shaft 107, as in the fourth embodiment. Since the minute gap between the rotary bearing 105d and the rotary shaft 107 is set to 10 μm or less, the objective lens 108
The mounting position deviation between a and 108b is set to a level that can be ignored.

Further, since the blade 105a is provided with two convex portions, the objective lens 108 is set to the optical path 14a.
When projecting onto 1, the two protruding parts are exactly the annular yoke 2.
It comes closest to 33 and coincides with the magnetic center position. In addition to when the magnetic field is at the position of the tracking coils 200a, 200b, the booster coils 234a,
Even at the position of 234b, since it is a magnetic stable point, accurate synchronization can be achieved without using a means for measuring the position of the magnetic pole, such as a Hall element as in a normal motor. Like

By applying to the booster coils 234a and 234b a method similar to that in which a large current is momentarily passed through the tracking coil in the fourth embodiment (that is, the control signal from the objective lens switching circuit 131 in FIG. A kick pulse can be generated to rotate the first movable body 105 at 90 ° intervals after a certain period of time (as applied to the booster coils 234a and 234b).

Further, since the permanent magnet of the movable part of the device and the coil are arranged in the fixed part, it becomes easy to route the wiring for supplying the current to the coil. for that reason,
Not only is it easy to rotate the first movable body 105 by 180 ° or more, but since the permanent magnet is used as the blade 105a, the rigidity can be increased, and good vibration characteristics can be obtained, which is a great practical effect. .

Next, a method of attaching the objective lens will be described.

The central axes in the longitudinal direction of the parallel leaf springs 231a and 231b connect the centers of the two objective lenses 108a and 108b in the state shown in FIG. 32 (just one objective lens 108 is on the optical path 141). It coincides with the direction orthogonal to the line segment, and as described above, the objective lens 108a
Is attached above the objective lens 108b. Further, as shown in FIG. 33, in the neutral state of the parallel leaf springs, the upper surface of the objective lens 108a has an upper leaf spring 23.
1a is above the bottom surface and the objective lens 108b is exactly in the middle of both leaf springs 213a, 231b.

At the same time with such an arrangement, the objective lens 108a is rotationally moved on the side which does not interfere with the leaf springs 231a and 231b, and the objective lens 108b is the leaf spring 23.
Control is performed so that the gap between 1a and 231b is rotationally moved.

If the operating range (working distance) of the objective lens 108a is L1 and the working range (working distance) of the objective lens 108b is L2, L2 is more than L1 in consideration of interference with the leaf springs 231a and 231b. Is bigger. The difference L in mounting height between the two objective lenses 108a and 108b has a relationship of L≤L2-L1.

When using the objective lens 108a,
The distance between the surface of the disc 101 and the objective lens 108a is L1.
And the objective lens 108b and the disc 101 at that time
The distance between and is L1 + L. The distance between the surface of the disc 1 and the objective lens 108a when the objective lens 108b is used is L2-L, and the objective lens 108b and the disc 101 at that time are
The distance between and is L2. Here, L is the objective lens 108a
Is a difference in mounting height between the objective lens 108b and the objective lens 108b.
It means that it is close to 1.

The shortest distance D of the first movable body 105 at this time
Is D = MINIMUM (L1, L1 + L, L2-L, L
2) and now, if L2> L1, then D = MINIMUM (L1, L1 + L, L2-L).

When L <0, D = L1 + L <L1 When 0 <L ≦ (L2-L1) D = L1 When L2-L1 <L, D = L2-L <L1

That is, it is understood that the shortest distance D becomes the largest when L is L≤L2-L1 and coincides with L1.

Therefore, by setting the difference L in mounting height between the objective lenses 108a and 108b so as to satisfy the above equation, the objective lenses 108a and 108b are
It is possible to minimize the probability that the other lens collides with the disc 101 when the focus of one is adjusted.

When the actual mounting state of the objective lenses 108a and 108b is different from the neutral position of the operating range, the objective lens 108 is corrected in order to correct this deviation.
In order to position a and 108b in the focus direction, it is necessary to constantly keep the DC current flowing. However, in this embodiment, as described above, the objective lenses 108a, 1a
Since the mounting height is set in correspondence with the operating range of 08b, the power consumption of the device can be reduced.

Further, it is possible to prevent the objective lenses 108a and 108b from colliding with the disc 101, and the disc 101 side is not damaged.

The method of giving deviations to the positions of the objective lenses 108a and 108b in the optical axis direction is limited to the case where the first movable body 105 is elastically supported by the parallel leaf springs 231a and 231b as in this embodiment. Needless to say, the present invention can also be applied to other methods such as a shaft sliding method.

[Fourteenth Embodiment] Next, a fourteenth embodiment of the objective lens driving device of the present invention will be explained with reference to FIGS. 36 to 39. Here, FIG. 36 is a plan view of the objective lens driving device, FIG. 37 is a sectional view of the objective lens driving device taken along the line AA ′ in FIG. 36, and FIG. 38 is taken from the line BB ′ in FIG. FIG. 39 is a partial cross-sectional view of the objective lens driving device as seen.
It is sectional drawing which followed CC 'line inside.

The present embodiment differs from the thirteenth embodiment described above in the structure of the first movable body 105. First movable body 105
The blade 105 at a position facing the surface of the disk 101.
a and a permanent magnet 240 fixed to the lower part of the blade 105a. The blade 105a of this embodiment is
It is formed of a material in which carbon is compounded with a resin having excellent slidability and excellent rigidity, for example, a liquid crystal polymer, epoxy, or polyphenylene sulphite resin. Permanent magnet 2
As is clear from the cross-sectional view shown in FIG. 37, 40 is formed in a substantially oval shape having a hole 240a at its center, and both longitudinal ends thereof are magnetized into an N pole and an S pole, respectively. The overall finish is axisymmetric. Then, the blade 105a and the permanent magnet 240 are integrated by injection molding to be manufactured as the first movable body 105.

The rotating shaft 107 has the magnetic core 10 at the center thereof.
7a and the surrounding covering portion 107b. Here, since the diameter of the middle portion of the magnetic core 107a, that is, the fitting portion with the permanent magnet 240 is large,
The flow of the magnetic flux becomes larger than that of the other parts of the permanent magnet 240, so that the neutral position of the first movable body 105 in the axial direction is magnetically determined.

As the material of the covering portion 107b, for example, a composite resin in which an epoxy resin is mixed with carbon, mica, etc. is used. By selecting such a material, it becomes possible to obtain high hardness and excellent sliding characteristics.

The tracking coils 200a, 20
0b and the focus coils 109a and 109b are shown in FIG. 39 (a sectional view taken along the line CC 'in FIG. 36). In this embodiment, no booster coil is used, and a large instantaneous current is applied to the tracking coils 200a and 200b as described in the fourth embodiment.

Further, the optical unit 120 (not shown here) is not fixed to the movable body 104 but is fixed to the base 102 (a so-called separation optical system is adopted. Therefore, the laser beam LB is just right. It is guided from the radial direction of the disc 101, bent 90 ° by the raising mirror 142 fixed to the second movable body 106, and guided to the objective lens 108. As shown in Fig. 36, the focus coil 109a is partially bent. The reason is that the optical path of the laser beam LB from the fixed optical system is secured.

The magnetic flux entering the focus coil 109a (tracking coil 200a) from the permanent magnet 240 passes through the U-shaped yoke 241 and returns to the permanent magnet 240 from the facing focus coil 109b (tracking coil 200b). Make a road. By using this magnetic path, the neutral position of the objective lenses 108a and 108b at the time of recording / reproducing is determined.

Tracking coils 200a, 2 of a magnetic circuit formed by a U-shaped yoke 241 and a permanent magnet 240.
Lorentz force is generated by the current flowing through 00b,
The movable body 105 is finely driven in the thickness direction and the radial direction of the disc 101. According to the present embodiment configured as described above, the following effects can be obtained. That is, in the present embodiment, not only can the first movable body 105 be driven in the focus direction and the tracking direction with only one permanent magnet, but also the objective lens 10 can be used.
A driving force for switching 8a and 108b can also be generated. Therefore, the number of relatively expensive permanent magnets used is reduced, and the manufacturing cost of the device is kept low.

Further, for example, the N pole surface of the opposite polarity becomes far from the coil facing the S pole, and as a result, the magnetic field of the S pole effectively acts on the coil. That is, the effect of strengthening the magnetic field at the site where electromagnetic interaction with the coil occurs is also obtained, as compared with the case where two permanent magnets are attached facing each other.

Further, as in the tenth embodiment described above, since the permanent magnet is arranged in the movable part of the device and the coil is arranged in the fixed part, the wiring for supplying the current to the coil can be easily routed. . Further, in the present embodiment, as in the fourth embodiment, a shaft sliding method is adopted for driving in the focus direction, and therefore, when switching the objective lenses 108a and 108b, the first movable body 105 is rotated clockwise. Alternatively, it may be rotated counterclockwise, and in principle, 360 ° rotation is possible. It is possible to realize "switching of the objective lens only by one-way rotation" which cannot be realized by any of the above-described embodiments. Therefore, the risk of the device becoming inoperable due to malfunction is greatly reduced.

[Fifteenth Embodiment] Next, FIGS.
A fifteenth embodiment of the objective lens driving device of the present invention will be described with reference to FIG. Here, FIG. 40 is a cross-sectional view of the objective lens driving device, and FIGS. 41 and 42 are plan views showing operating states of the objective lens driving device.

The present embodiment is different from the above-mentioned fourteenth embodiment in the support mechanism of the first movable body 105. That is, the hinge mechanism is adopted for the axial displacement and the axial displacement of the first movable body 105. 2 on the first movable body 105
The mounting positions of the individual objective lenses 108a and 108b are
Very close compared to other embodiments.

As shown in FIGS. 41 and 42, in the present embodiment, the first movable body 105 has one end of the first hinge member 250 fixed to the central portion thereof. First hinge member 2
The hinge 50 has a thin hinge 250a.
The position of 50a is configured to substantially coincide with the position of the center of gravity of the first movable body 105. First hinge member 2
Reference numeral 50 has a structure that allows the first movable body 105 to rotate within a range of a finite angle.

The other end of the first hinge member 250 is fixed to one end of the second hinge member 251. As shown in FIG. 40, the second hinge member 251 has hinges 25 at two locations.
It has a 4-node hinge mechanism with 1a and 251b,
The other end is fixed to the second movable body 106 via a fixing member 232. The second hinge member 251 has a structure that allows the first movable body 105 to translate in the optical axis direction.

Notches are formed in the vicinity of the sides of the first movable body 105, and focus coils 109a and 109 wound in an annular shape so as to fit in the notches.
b is fixed, and an annular focus coil 109
Rectangular tracking coils 200a and 200b wound in a plane are fixed to the surfaces of a and 109b. Center yokes 221a and 221b are provided in the annular space formed by the focus coils 109a and 109b.
Is inserted. Then, whichever of the two objective lenses 108a and 108b is selected, the tracking coils 200a and 2b are in the neutral position.
It is set so that two opposite sides of 00b (portions extending in the vertical direction of the paper surface in FIG. 40) are located in the magnetic gap.

A magnetic body 252 made of an iron piece or the like is attached to the tip end portion of the first movable body 105. Then, the yoke 253 and the permanent magnet 254 are arranged in a relationship facing the magnetic body 252, and are fixed on the second movable body 106. Here, the yoke 253 has two protrusions 2
It has a substantially U shape having 53a and 253b.

There are two objective lenses 1 on the first movable body 105.
08a and 108b are fixed at positions close to each other. The magnetic body 252 is one protrusion 253b of the yoke 253.
When the magnetic lens 252 faces the other protrusion 253a of the yoke 253, the objective lens 108a is positioned on the central axis (FIG. 41).
b is positioned on the central axis (FIG. 42). Note that FIG.
1, the objective lens 108a and the objective lens 108b are arranged on the optical path 141, respectively.

Subsequently, the operation of this embodiment will be described.

The basic operating principle of the first movable body 105 is as follows.
This is almost the same as each of the above-mentioned embodiments. In this embodiment, the first
When the movable body 105 moves in the focus direction, the second
Two hinges 251a and 251b of the hinge member 251
Is performed by deforming. When the first movable body 105 moves in the tracking direction, the first hinge member 25
This is performed by deforming the hinge 250a of 0.

Here, the hinge 2 of the first hinge member 250
50a is about 10 degrees each with the central axis as a boundary, and about 20 as a whole.
The rotation of about ° is possible. This change in angle makes it possible to switch between the two objective lenses 108a and 108b.

The magnetic body 252 faces one protrusion 253b when the objective lens 108a is in use, and the other protrusion 25 when the objective lens 108b is in use.
It faces 3a. Therefore, both objective lenses 108
The positions where a and 108b are used are just magnetically stable points. Here, the magnetic body 252 is located on the objective lens side with respect to the hinge member 250, and is located on the opposite side to the 4-node hinge member 251. Therefore, the magnetic attraction acts in the direction in which the hinges 251a and 251b are extended by the magnetic attraction. This is the direction in which the hinges 251a and 251b are pushed in, in other words, the direction opposite to the direction in which the hinges 251a and 251b are buckled, so the first movable body 105
The whole is easily restored to the neutral position in the axial direction, and the driving characteristics in the focus direction are extremely stable.

[Sixteenth Embodiment] FIG. 43 and FIG.
A sixteenth embodiment of the objective lens driving device of the present invention will be described with reference to FIG.

This embodiment is different from the thirteenth embodiment described above in the positioning mechanism of the objective lenses 108a and 108b. That is, in the fifteenth embodiment described above, the first movable body 10
5, a magnetic body 252 is attached to the permanent magnet 25.
4 was attached to the second movable body 106 via the yoke 253. In this embodiment, the permanent magnet 254 is attached to the first movable body 105, and the yoke 253 is attached to the second movable body 1.
It is attached to 06. The cross section of the device in this embodiment is almost the same as that of the fifteenth embodiment described above (see FIG.
(See 0), so the description is omitted.

Magnetic sensors 255a and 255b such as Hall elements are fixed to the places where the protrusions 253a and 253b were formed. Magnetic sensor 25
It is possible to know which objective lens is used (located in the optical path 124) from 5a and 255b. With such a configuration, the objective lens to be used can be discriminated even when a strong shock is applied from the outside, so that a great effect in practical use such that a malfunction can be prevented is obtained. [Seventeenth Embodiment] FIG. 45 shows the structure of an optical head according to a seventeenth embodiment of the present invention, which is roughly classified into a fixed optical section 401, a rotary blade 402 as a movable supporting member, and a magnetic circuit. It is composed of a lens actuator constituted by 411. The rotating blade 402 is rotatable about an axis perpendicular to the recording surface of a recording medium (hereinafter referred to as an optical disc) (not shown) loaded in the optical disc device,
Further, it is provided so as to be movable in the optical axis direction of the light beam with which the optical disc is irradiated. The fixed optical unit 401 includes a light source 403 such as a semiconductor laser and a collimating lens 40.
4 and a beam splitter 405;
A condenser lens 408 and a diffractive optical element (HOE: Holographi) for detecting the light beam reflected by the optical disc.
c Opti cal Element) 409 and photodetector 410
It is composed of a detection system including.

The rotary blade 402 has a bottomed cylindrical shape with at least its upper end closed in the figure, and a plurality (two in this example) of objective lenses 407a and 407b are disposed on this upper end. The magnetic circuit 411 includes the rotating blade 40.
2 and a pair of semi-arc-shaped yokes 412a and 412b arranged at positions opposite to each other by 180 ° and the yoke 412.
magnets 413a, 41 attached to the inner peripheral side of a, 412b
3b and magnets 413a and 413b of the rotating blade 402
The tracking coil 41 disposed at a position that can face the
4a to 414f. The configuration and operation of the magnetic circuit 411 will be described later in detail.

A beam splitter 405 and an objective lens 407 are provided between the fixed optical section 401 and the rotary blade 402.
Reflector 40 for forming an optical path between a and 407b
6 are arranged.

Next, the operation of the optical head of this embodiment will be described. The light emitted from the light source 403 is collimated by the collimating lens 404 and becomes a parallel light beam.
05 and the reflecting mirror 406, the light is condensed by the objective lens 407a or 407b, and the surface on which the information of the rotating optical disc which is arranged on the rotating blade 402 is recorded (hereinafter,
A minute beam spot is formed on the recording surface).

The light reflected on the recording surface of the optical disk is transmitted from the light source 403 in the outward path, to the collimating lens 404,
Beam splitter 405, reflecting mirror 406, objective lens 4
Contrary to the path of the incident light passing through 07a or 407b toward the recording surface of the optical disc 420a or 420b, it is reflected by the beam splitter 405 through the objective lens 407a or 407b and the reflecting mirror 406 and is guided to the detection system.
The detection system uses the objective lens 407a or 40 for the pit row on the recording surface of the optical disc 420a or 420b.
An error signal for controlling the position of the minute spot focused by 7b in the optical axis direction (focus direction) and the radial direction (tracking direction) of the optical disc 420a or 420b, and an information signal recorded on the optical disc 420a or 420b. Is for playing.

A detection system for obtaining these three signals (focus error signal, tracking error signal, reproduction information signal) is described in detail in, for example, Japanese Patent Laid-Open No. 3-257, "Optical memory device". It can consist of things. Although this detection system itself is not related to the gist of the present invention, its operation will be briefly described. The detection system of this embodiment is composed of the condenser lens 408, the HOE 409, and the photodetector 10 as described above. The reflected light from the optical disc is condensed on the photodetector 10 by the condenser lens 408.

On the HOE 409 arranged between the condenser lens 408 and the photodetector 410, holograms of different lattice shapes are formed in the region divided into two by the dividing line of the same direction as the track on the optical disc 420a or 420b. Has been done. Specifically, when one of the lattice shapes has a shape that is curved inward in a spool shape, the other one is a hologram that has a shape that is curved outward in a barrel shape. Also,
The grating pitch is different so that the diffracted light of each hologram is diffracted to different positions on the detection surface of the photodetector 410. When the hologram on the HOE 409 is set in such a lattice shape, the light beam on the photodetector 410 can be caused to change its characteristic shape in accordance with the focus shift. It is possible to detect a focus error by forming a set of two-split light receiving elements and differentially detecting each diffracted light by the two-split light receiving elements. The tracking error can be detected from the difference between the diffracted lights of the holograms. Further, for the reproduction information signal, the photodetector 410
It can be easily detected from the sum of the outputs of. In this embodiment, HO
Although the detection system using E is used, the detection system is not limited to this, and any known detection optical system such as a focus error detection system called an astigmatism method in which a condenser lens and a cylindrical lens are combined can be similarly used. .

The four output signals output from the two sets of the two-divided light receiving elements constituting the photodetector 410 are input to the detection signal calculation section 501, where amplification and calculation are performed, thereby performing the above-mentioned operation. As a result, a reproduction information signal, a focus error signal and a tracking error signal are generated. Of these, the reproduction information signal is output to a signal processing unit (not shown) that performs decoding and the like. On the other hand, the focus error signal and the tracking error signal are input to a control signal generation circuit 502 connected to a host system (not shown), and a special operation signal is superimposed on the tracking control signal at the time of focus control sequence control and track search. After signal processing such as the above is performed, it becomes a focus drive signal and a tracking drive signal via the actuator drive circuit 503.

In accordance with these focus drive signal and tracking drive signal, the focus coil 416 and tracking coils 414a to 414a-4 in the magnetic circuit 411.
The current flowing through 14c is controlled. As a result, the rotary blade 402 is controlled in the optical axis direction (focus direction) of the light beam with which the optical disc is irradiated and the radial direction (tracking direction) of the optical disc, as will be described later, according to the driving force generated by the electromagnetic action. Controls are made to position the light spot on top.

The series of constructions and operations are basically the same as those of the conventional optical head. Next, the characteristic configuration of this embodiment will be described.

In general, the optical disc apparatus optically reads the information recorded on the optical disc and reproduces it as a signal. Therefore, if dust or scratches are generated on the recording surface, the light is scattered and reproduction becomes impossible. I will end up. Therefore, by thickening the layer on the side of the optical beam on which the light beam is incident (generally the disc substrate) to increase the light beam spot on the surface of the disc substrate, it is possible to reduce the influence of dust and scratches that occur after manufacturing. The optical disk was constructed in. The thickness of the disk substrate of the conventional optical disk is often 1.2 mm. However, when the numerical aperture of the objective lens is increased or the wavelength of the light source is shortened in order to improve the recording density of the optical disc, the adverse effect of the thick disc substrate becomes remarkable.

That is, in FIGS. 1A and 1B, the change in transmitted wavefront aberration when the optical disc is tilted with respect to the objective lens is 0.6 m when the thickness of the disc substrate is 1.2 mm.
As shown in the case of m, even if the objective lens has the same numerical aperture, the thinner the disc substrate is, the smaller the transmitted wavefront aberration due to the disc tilt and the better the focusing property of the focused spot on the recording surface is. A high quality information signal can be obtained. For this reason, optical discs with thinner disc substrates have emerged. As a result, if optical discs with different substrate thicknesses are mixed, there will inevitably be a demand to reproduce them on the same device. become. In response to such a demand, the present invention is capable of stably reproducing information recorded on optical disks having different specifications such as a substrate thickness, without the problems of the related art, with the same simple, small-sized and inexpensive device. It was done like this. Hereinafter, a specific description will be given.

FIGS. 46 (a) and 46 (b) schematically show how the specifications of the optical disc relate to the optical head. In this example, two optical discs 420a, 420a having different substrate thicknesses are provided. 420b is shown. The objective lenses 407 having different numerical apertures NAa and NAb are provided for the optical disks 420a and 420b having different substrate thicknesses.
a, 407b is used. Objective lenses 407a, 40
The degree of freedom of specification of 7b includes focal length (Fa, Fb), working distance (WDa, WDb), aperture (Da, Db) and the like. Using this degree of freedom, some characteristic optical heads can be constructed. Details of this will be described later.

In this embodiment, as shown in FIG. 45, a plurality of objective lenses 407a and 407b having optimum optical characteristics according to the specifications of the optical disk are provided on the rotary blade 402, and these are selectively selected. By using it, it is possible to reproduce information from optical disks of different specifications. For example, when the optical disc is a CD, the disc substrate has a thickness of 1.2 mm and the objective lens has a numerical aperture of 0.45. For a recording medium having a higher density, the disc substrate has a thickness of 0.6 mm. An objective lens satisfying specifications such as a numerical aperture of 0.6 will be mounted. And
Rotating blade 40 according to the optical disc inserted in the device
By rotating 2, the objective lens suitable for the optical disk is selected and information is reproduced. A control method when selecting one of the objective lenses 407a and 407b will be described later.

47 (a) and 47 (b) show examples of the shape of the objective lens. FIG. 47 (a) shows a glass mold lens, and FIG. 47 (b) shows a plastic injection lens. This is merely an example, but there are characteristic differences in shape due to the difference in each manufacturing method and material. Even if the specifications of the lens are different, it is easy to realize the same outer shape and weight of the lens. By arranging the objective lens having such a relationship, an imbalance in weight that deteriorates the vibration characteristics of the actuator does not occur, so that a good optical head can be configured.

FIG. 48 shows the rotary blade 4 shown in FIG.
2 and a magnetic circuit 411 (411a, 411b). On the outer peripheral surface of the rotating blade 402, six tracking coils 414a to 414f each having a shape as shown in FIG. 49 are provided. These tracking coils 414a to 414f are composed of magnets 413a and 4e.
13b and the yokes 412a and 412b constitute the magnetic circuits 411a and 411b, and the objective lenses 407a and 407b are selectively placed on the optical axis of the light beam according to the specifications of the optical disk loaded in the optical disk device (for example, the substrate thickness of the optical disk). Drive force for setting the rotation speed and the drive force for controlling the rotation of the rotary blade 402 about the rotation axis 415 in order to follow the track shift caused by the eccentricity of the optical disc when reproducing the information recorded on the optical disc. To occur. The optical axis of the light beam is assumed to be located on the alternate long and short dash line in FIG. Therefore, FIG. 48 shows a state in which the objective lens 407b is located on the optical axis of the light beam, and the light beam is applied to the optical disc through the objective lens 407b to reproduce information from the optical disc. . Here, the tracking control when the information reproduction is performed by irradiating the optical disc with the light beam through the objective lens 407a is performed by the magnetic circuit 4.
Tracking coils 414d and 414e in 11a,
Tracking coils 414a, 414a in the magnetic circuit 411b
14b. On the other hand, tracking control when information reproduction is performed by irradiating an optical disk with a light beam through the objective lens 407b is performed by the tracking coils 414e and 414f in the magnetic circuit 411a.
And the tracking coil 414 in the magnetic circuit 411b.
b, 414c.

In this embodiment, the objective lens 407 is used.
a and 407b are provided at intervals of 60 °, and the tracking coils 414a to 414f are provided at intervals of 60 ° over the entire circumference of the rotary blade 402. The relative positional relationship between them is that the hollow portion of the tracking coil 414 shown in FIG. It is set to match the objective lenses 407a and 407b. By arranging the objective lenses 407a and 407b and the tracking coils 414a to 414f in this way, the magnetic circuits 411a and 411 can be used when any of the objective lenses 407a and 407b is used for information reproduction.
Two tracking coils can each be located in b. In this way, the six tracking coils 41
If the number of tracking coils used for tracking control is 4 out of 4a to 414f, the utilization factor becomes high, and a large driving force can be efficiently generated.

FIG. 50 shows a more detailed structure of the lens actuator. A tracking coil 414 is provided in the rotary blade 402 of the lens actuator.
between a and 414b, between 414b and 414c, 414d
And 414e, 414e and 414f, respectively, and ferromagnetic pieces 419a to 419d are embedded. These ferromagnetic pieces 419a to 419d rotate with respect to the optical axis direction of the light beam about the rotation axis 415 of the rotary blade 402 by the magnetic attraction force acting between the magnets 413a and 413b in the magnetic circuits 411a and 411b. The objective lens 407a is for determining the neutral position of the rotating blade 402 with respect to the rotating direction of the blade 402.
It is provided so as to be located at the center of the magnetic circuits 411a and 411b when 407b is located on the optical axis of the light beam. That is, when the objective lens 407a is located on the optical axis, the ferromagnetic pieces 419a and 419c are located in the magnetic circuits 411a and 411b, and when the objective lens 407b is located on the optical axis as shown in FIG. Are ferromagnetic materials 419b and 419d and magnetic circuits 411a and 411.
It will be located in b.

Thus, the magnetic circuits 411a and 411b are
By providing the ferromagnetic bodies 419a to 419d located inside to determine the neutral position of the rotary blade 402, the neutral positioning can be performed at the optimum position for each of the two objective lenses 407a and 407b. .
In addition, since the neutral position is configured by using an elastic member such as rubber, the neutral position exists at only one point, and thus the neutral position is set at two different positions as in the present embodiment. I can't. A neutral positioning method using magnetic balance force as in this embodiment is disclosed in Japanese Patent Laid-Open No. 60-140549 "Objective lens driving device".
Is disclosed in. However, in this known example, only one set of neutral positioning is disclosed, and nothing is disclosed about a plurality of sets of neutral positioning.

When the lens actuator having the above-mentioned structure is used, the tracking coils 414a to 414f are
The objective lens 407a, 407a,
Either one of 407b can be arbitrarily positioned on the optical axis of the light beam. FIG. 51 shows the objective lens 407a, 407 in the lens actuator shown in FIG.
It is a figure for demonstrating the control method at the time of selecting b, and has shown the current waveform sent to the tracking coils 414a-414f at the time of exchanging an objective lens from 407b to 407a, and when exchanging from 407a to 407b. . Each of these tracking coils 414a to 414f
The direction of the current flowing through each tracking coil 414a
The directions of the forces generated by ˜414f (indicated by 7b → 7a or 7a → 7b) are as shown in FIG. 49.
When the current flows clockwise in the tracking coils 414a to 414f as shown in FIG. 49, the direction of the current is "+", and in that state, a force for rotating the rotary blade 402 to the right acts.

For example, when replacing the objective lens 407b with the objective lens 407a, a set of tracking coils located at 180 ° opposite positions, that is, 414a, 414.
d set and 414b and 414e set and 414c and 41
In the same direction for each combination of the 4f set,
And a pair of 414b and 414e and 414c and 414f
As shown in the figure, a stepwise current whose direction reverses halfway is applied to the group of "+" → "-" or "-" → "+". This operation is similar to the control operation of the lens actuator called "track jump" performed when the same track on the optical disk is repeatedly reproduced. However, this embodiment is characterized in that the rotation angle of the rotary blade 402 is large. The objective lens is 40
It is also characteristic that the current waveforms flowing through the tracking coils 414b and 414e are the same when the 7a is replaced with the 407b. This is the objective lens 407a,
Each time 407b is replaced, magnetic circuits 411a and 411b
This is because the positions of the tracking coils 414b and 414e located inside are changing.

The tracking drive signal for passing such a current through the tracking coils 414a to 414f is
As shown in FIG. 45, it is generated by the control signal generation circuit 502 based on the request from the host system, and is supplied to the respective tracking coils 414a to 414f via the actuator drive circuit 503.

As described above, according to this embodiment, a plurality of objective lenses 407a and 407b are mounted on the same lens actuator, and the tracking coils 414a-41 are provided.
By controlling the waveform of the current flowing through 4f, the objective lenses 407a and 407b suitable for optical discs having different specifications are selectively positioned on the optical axis of the light beam and used for information reproduction from those optical discs. Only one lens actuator is required, and the problem with the conventional technology of mounting multiple objective lenses on their own lens actuators and optical heads is that the actuators and optical heads occupy a large space, and the optical system can be shared. In addition, it is possible to solve the problem that the merit of reproducing optical discs having a plurality of specifications with the same optical disc device is lost.

[Eighteenth Embodiment] FIG. 52 schematically shows the structure of a lens actuator in the present embodiment. In this embodiment, the objective lenses 407a and 407b
Are respectively provided at point-symmetrical positions on the rotary blade 402 about the rotary shaft 415. The fixed optical unit 1 having the same configuration as that shown in FIG. 45 is provided corresponding to each of the objective lenses 407a and 407b.

Further, the optical head of this embodiment is mounted so as to be movable in the radial direction of the optical disc 420 indicated by arrow A when the optical disc 420 is mounted by being fitted to the guide shaft 418 of the spindle motor 417. There is.
Further, when the rotary blade 402 moves the optical head in the direction of arrow A, the locus of the rotary shaft 415 indicates the optical disc 4.
They are arranged in a relationship that coincides with a straight line passing through the center of 20 (shown by a chain line). The information pit array 510 on the optical disc 420 is read by irradiating the light beam emitted from the objective lens 407a or 407b.

In this case, in order to selectively use the objective lens suitable for the optical disc 420 mounted in the optical disc device, signals for driving the lens actuator (focus drive signal and tracking drive signal) are used.
Since it suffices to select whether to use the signal detected from the optical disc 420 via the objective lens 407a or the signal detected via the objective lens 407b according to the instruction of the host system, the 17th embodiment It is not necessary to select the objective lens by rotating the rotary blade 402 largely, for example, by 60 °. Therefore, in this embodiment, the lens actuator may have almost the same configuration as that in which one objective lens is mounted, and a lens actuator having two objective lenses 407a and 407b can be easily manufactured by extending the conventional technique. The advantage is that you can

[19th Embodiment] FIG. 53 shows the first embodiment of the present invention.
9 shows a configuration of an optical head according to a ninth embodiment.
The two fixed optical units 401 in the eighth embodiment (FIG. 52) are separated from the carriage for moving the optical head in the radial direction of the optical disc 420 and fixedly arranged.

The configuration of this embodiment will be described below. On the lower surface side of the optical disc 420, the objective lenses 407a, 407
The pickup 421 is provided with a moving optical system including b and a reflecting mirror (not shown). The two fixed optical systems 1 are provided on an extension line of the movement path of the pickup 421 in the outer peripheral direction of the optical disc 420. The light beam emitted from the fixed optical system 401 toward the pickup 421 is raised at a right angle by the reflecting mirror of the moving optical system, and focused onto the optical disc 420 through the objective lens 407a or 407b. Also, the optical disc 4
The light beam reflected by 20 passes through the objective lens 407a or 407b, is then horizontally bent by the reflecting mirror, and is sent to the fixed optical system 401. When information is reproduced from the optical disc 420, the light beam focused on the optical disc 420 through the objective lens 407a or 407b is intensity-modulated according to the presence or absence of the pit 456, and the reflected light is reflected through the objective lens 407a or 407b. It is guided to the fixed optical system 401 by a mirror.

The pickup 421 is a linear motor 47.
4 has a carriage 460 that is movable in the radial direction (direction of arrow A) of the optical disc 420, which is the tracking control direction. A plurality of paired support rollers 462 supported by leaf springs are provided on both sides of the carriage 460.
The 62 is rotatably supported in the radial direction of the optical disc 420 by rolling contact with two guide shafts 464 arranged horizontally and in parallel along the radial direction of the optical disc 420.

Further, radial coils 466 are attached to both sides of the carriage 460, and these radial coils 466 are the inner yokes 468 of the magnetic circuit.
It is in a state of being fitted. The inner yoke 468 is connected to an outer yoke 470 provided on the outer side, and magnets 472 are attached to the inner side of the outer yoke 470 to form a linear motor 474. In this case, by energizing the radial coil 466, a propulsive force is generated, and the carriage 460 can be reciprocated in the radial direction of the optical disc 420.

According to the configuration of this embodiment, the carriage 46
0 is only a lens actuator and a reflecting mirror (a rising mirror), and the weight of the components mounted on the carriage 460 can be significantly reduced. can do.

[Twentieth Embodiment] FIG. 54 shows the second embodiment of the present invention.
1 shows a configuration of an optical head according to Example 0,
The same parts as those in the nineteenth embodiment (FIG. 53) are designated by the same reference numerals, and the description thereof will be omitted. In the nineteenth embodiment (FIG. 53), the two objective lenses 407a and 407b, which are to be applied to the optical discs having different specifications, are arranged, so that they cannot be used at the same time. Therefore, it is not necessary to provide the fixed optical system 401 corresponding to each of the objective lenses 407a and 407b, and many of them can be configured to be commonly used.

This embodiment focuses on such a point, and the light beam from the fixed optical system 401 is changed according to the specifications of the optical disk 420 mounted, for example, the polarization plane rotation element 43.
1 and a polarization beam splitter 432 are combined to selectively transmit light to the objective lenses 407a and 407b. As the polarization plane rotation element 431, a capsule in which a cholesteric liquid crystal is encapsulated and a configuration in which the rotation amount of the polarization plane of the light beam incident through the transparent electrodes provided on both surfaces thereof can be controlled by a voltage applied, It is possible to use a device configured to electrically control the rotation amount of the polarization plane of the incident light beam by using the electro-optic effect of the optical crystal.

As described above, since the optical head of this embodiment needs only one fixed optical system, the overall structure of the fixed optical system can be further simplified, and one objective lens and one fixed optical system can be used. It has almost the same configuration as the conventional optical head configured, and can be selectively used for reproducing information from optical discs having different specifications.

[Twenty-first Embodiment] FIG. 55 shows the second embodiment of the present invention.
1 shows a configuration of an optical head according to an example,
Carriage 46 of the optical head of the nineteenth embodiment (FIG. 53)
By further simplifying the configuration of the moving optical system located on 0,
It is configured to enhance high-speed accessibility.

That is, in the seventeenth to twentieth embodiments, the two objective lenses 407a and 407b are arranged on the rotary blade 402 whose positions can be two-dimensionally controlled, but in the present embodiment, they are arranged only in the optical axis direction. By fixing the two objective lenses 407a and 407b to the movable end of the carriage 434, which is composed of a suspension in which two leaf springs that are arranged to be controllable (movable) are arranged in parallel, the configuration of the lens actuator is simplified. ing. By doing so, the weight of the moving object at the time of access can be reduced, and further high-speed access can be realized.

In this embodiment, the objective lens 407a,
Magnetic circuit 435 for moving 407b in the optical axis direction
Is attached to the magnetic circuit 437 for moving the carriage 434 in the radial direction of the optical disc 420, so that the weight of components on the carriage 434 is further reduced.

In this embodiment, since the controllable degree of freedom of the lens actuator is one axis, a mechanism capable of controlling the remaining one axis (control of tracking direction) is required. The oscillating mirror 430 is provided at the light beam emitting portion from the fixed optical system 1 to the moving optical system, and the optical disc 4
The position of the light spot on 20 may be configured to be controllable in the radial direction. Further, similarly to the twentieth embodiment shown in FIG. 54, the polarization plane rotating element 431 and the polarization beam splitter 43 are arranged.
It is also possible to provide an optical switch composed of 2 and 2 so as to share the configuration of the fixed optical unit 401.

Next, regarding the seventeenth to twenty-first embodiments, how to set the specifications of the objective lens for the optical disks having different specifications will be described with reference to FIGS. 56 and 57. The optical disk 420 is mounted on the spindle motor with the surface on which the light beam is incident as a reference surface. Therefore, as shown in FIG. 56, the optical discs 420a and 420b are
When the thickness of the board is different as the difference of the specifications of 2
By arranging the two objective lenses 407a and 407b so that the focal lengths are different but the working distances are almost equal, the moving range of the rotary blade 402 in the optical axis direction of the light beam can be minimized. By doing so, even when the optical disc 420a and the optical disc 420b are exchanged, it is possible to easily perform the focus control so that the light beam is focused on the recording surface of the optical disc.

For example, as the optical discs 420a and 420b, the substrate material is polycarbonate and the thickness is 1.2 mm.
And an optical disc having a size of 0.6 mm, the optical disc 420b
When the focal length of the objective lens 407b used when reproducing the signal from the optical disc is set to 2.6 mm, the optical disc 420
Objective lens 407a used when reproducing a signal from a
If the focal length of each is 3 mm, then each objective lens 4
The working distances WDa and WDb of 07a and 407b can be made substantially equal.

FIG. 57 shows optical disks 420a and 420b.
Not only the substrate thickness of the optical disc 420 is different,
It shows a coping method when the densities of the information recorded in a and 420b are different. For example, the optical disc 420a is a C recorded with digitized music information.
D, and when the optical disc 420b is of a next-generation specification with higher recording density, the numerical aperture of the objective lens 407a for reproducing a signal from the optical disc 420a is 0.4 to 0.45, and the optical disc 420b is The numerical aperture of the objective lens 407b for reproducing the signal from
And so on.

Here, if the apertures Da and Db of the objective lenses 407a and 407b are made the same, the utilization rates of the incident light beams become the same, and therefore the reproduction obtained by detecting the light beams reflected by the optical discs 420a and 420b. The detection levels of the information signals can be made substantially equal, and the configuration of the detection signal calculation unit 501 in FIG. 45 can be simplified. When the level of the detection signal of the photodetector 410 changes depending on the optical disk used for reproduction, it is necessary to control the amplification degree so that the reproduction output level becomes almost the same value. This is because if the detection level changes, the control gains of the focus control system and the tracking control system change, which causes a problem that stable control cannot be performed.

The focal length of the objective lens 407b is 2.6 m.
m, the focal length of the objective lens 407a is 3.
By setting the distance to 9 mm, the objective lenses 407a, 40
The openings Da and Db of 7b can be made the same. That is, as shown in FIG. 57, a step is provided on the support portion of the objective lenses 407a and 407b of the rotary blade 402, and the objective lenses 407a and 407b are installed at different distances from the optical disc according to their focal lengths. There is.
Under such conditions, the two objective lenses 407a and 407b
If the specifications are set, although the numerical apertures are different, the outer shape and weight of the lens can be made substantially equal, so that the weight balance of the lens actuator that drives and controls the objective lens in two dimensions is improved, and a lens actuator with good controllability can be easily achieved. There is a new effect that can be realized.

FIG. 58 shows two objective lenses 407a and 407a.
7b shows adjusting means when both of them are not properly attached to the rotary blade 402. here,
Numerical aperture NAa of the two objective lenses 407a and 407b,
It is assumed that the relationship of NAb is NAa <NAb. Before explaining the adjusting means, the background will be described with reference to FIG.

FIG. 59 shows a change in transmitted wavefront aberration when a relative tilt occurs between the optical disc and the objective lens. A characteristic of the objective lens 407a having a small numerical aperture is shown by a curve D, and a characteristic of the objective lens 407b having a large numerical aperture is shown by a curve C. It can be seen that the effect of the tilt is smaller in the objective lens 407a having a smaller numerical aperture. This characteristic was used to determine the optimum adjustment method.

Returning to FIG. 58 and explaining the adjustment method,
Since FIG. 59 is presented, it seems that much explanation is not necessary, but relative tilt adjustment of the objective lens with respect to the optical disc is performed by the objective lens 407b having a large numerical aperture. In this case, although the optical disc 420a is arranged to be tilted with respect to the objective lens 407a having a small numerical aperture, its influence can be made smaller than that when the objective lens 7b is arranged to be tilted. The information signal can be reproduced if possible.

Although various embodiments have been described above, the present invention can be implemented by arbitrarily combining the above-mentioned embodiments, and in that case, more effects can be expected.
In short, the gist of the present invention is to provide at least two objective lenses adapted to various specifications and selectively use those objective lenses when recording / reproducing signals using optical disks having different specifications. An object of the present invention is to provide an optical head configured to obtain a sufficiently high quality reproduction signal without significantly changing the optical head when the objective lens is one.

Particularly, by mounting a plurality of objective lenses on one movable supporting member such as a rotary blade and controlling the movable supporting members to select the objective lens, only one lens actuator is required. It is possible to significantly reduce the size and simplify the configuration of the entire apparatus, as compared with the configuration in which optical heads having different specifications of the objective lens and head moving mechanisms for moving the same are provided for different optical disks. Here, if a plurality of objective lenses are arranged symmetrically with respect to the center of rotation of the movable body, in other words, so that the center of gravity of the movable body substantially coincides with the rotation axis, the movable body moves at the maximum speed. Therefore, the access time of the optical disk can be greatly shortened.

Further, the recording density is not limited to a plurality of objective lenses suitable for processing a plurality of discs having different standards such as a disc recording density, a warp allowable amount, a substrate thickness, etc. If the specifications of the objective lens differ during reproduction, the objective lens may be switched during recording and reproduction.

Further, the recording medium is not limited to the read-only optical disc, but may be a write-once optical disc, a rewritable magneto-optical disc, or the like.

[0364]

As described above, according to the present invention, it is possible to perform at least good reproduction on a plurality of information recording media having different specifications of the objective lens while having a compact and inexpensive structure. An optical head device is provided.

Further, according to the present invention, it is possible to perform good recording and reproduction even if the specifications of the objective lens are different at the time of recording and at the time of reproduction even though the structure is small and inexpensive. A head device is provided.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between wavefront aberration and tilt when substrates of optical disks are different.

FIG. 2 is a perspective view showing a schematic configuration of the entire optical disc recording / reproducing apparatus including the first embodiment of the optical head according to the present invention.

FIG. 3 is a diagram showing a control system and an optical system of the recording / reproducing apparatus shown in FIG.

FIG. 4 is a partial cross-sectional side view schematically showing the configuration of the optical head according to the first embodiment of the present invention.

5 is a diagram schematically showing the basic configuration of the optical disc recording / reproducing apparatus shown in FIG.

FIG. 6 is an explanatory diagram showing a state where the first objective lens is selected in the first example.

FIG. 7 is an explanatory diagram showing a state in which a second objective lens is selected in the first example.

FIG. 8 is a diagram schematically showing the basic configuration of the entire optical disc recording / reproducing apparatus including a second embodiment of the optical head according to the present invention.

FIG. 9 is an explanatory diagram showing a state where the first objective lens is selected in the second example.

FIG. 10 is an explanatory diagram showing a state where the second objective lens is selected in the second example.

FIG. 11 is a schematic perspective view showing the configuration of the main part of the entire optical disc recording / reproducing apparatus including the third embodiment of the optical head according to the present invention.

FIG. 12 is an explanatory diagram showing a state where the first objective lens is selected in the third example.

FIG. 13 is an explanatory diagram showing a state where the second objective lens is selected in the third example.

FIG. 14 is an explanatory diagram schematically showing a state of mounting a plurality of objective lenses in the first to third examples.

FIG. 15 is a plan view showing the outline of the entire optical disc recording / reproducing apparatus including a fourth embodiment of the optical head according to the present invention.

16 is a diagram showing a cross section taken along line AA ′ in FIG. 15 together with an optical system.

17 is a sectional view taken along the line B-B ′ in FIG.

FIG. 18 is a diagram showing an optical system and a signal processing system according to Example 4.

FIG. 19 is a plan view of the movable portion of the optical head according to the fifth embodiment of the present invention.

FIG. 20 is a plan view of the movable portion of the optical head according to the sixth embodiment of the present invention.

FIG. 21 is a plan view and a perspective view of a movable part of an optical head according to a seventh embodiment of the present invention.

FIG. 22 is a plan view of the movable portion of the eighth embodiment of the optical head according to the present invention.

FIG. 23 is a plan view of a movable portion of a ninth embodiment of the optical head according to the present invention.

FIG. 24 is a plan view of the movable portion of the optical head according to the tenth embodiment of the present invention.

FIG. 25 is a sectional view of the tenth embodiment.

FIG. 26 is a plan view of the movable portion of the eleventh embodiment of the optical head according to the present invention.

FIG. 27 is a plan view of the movable portion of the twelfth embodiment of the optical head according to the present invention.

FIG. 28 is a plan view showing an example in which one counterweight is arranged instead of the objective lens in the fourth to twelfth examples.

FIG. 29 is a plan view showing an example in which two counterweights are arranged instead of the objective lens in the fourth to twelfth examples.

30 is a plan view showing an example using a flexible printed circuit board in the modification of FIG.

FIG. 31 is a plan view showing an example in which a flexible printed board is used in the modification of FIG. 29.

32 is a plan view of the movable portion of the thirteenth embodiment of the optical head according to the present invention. FIG.

FIG. 33 is a cross-sectional view taken along the line A-A ′ in FIG. 32.

34 is a cross-sectional view taken along the line B-B ′ in FIG. 32.

FIG. 35 is a cross-sectional view taken along the line C-C ′ in FIG. 32.

FIG. 36 is a plan view of the movable portion of the fourteenth embodiment of the optical head according to the present invention.

37 is a cross-sectional view taken along the line A-A ′ in FIG. 36.

38 is a partial cross-sectional view taken along the line B-B ′ in FIG. 37.

FIG. 39 is a cross-sectional view taken along the line C-C ′ in FIG. 36.

FIG. 40 is a sectional view of a movable part of a fifteenth embodiment of the optical head according to the present invention.

FIG. 41 is a plan view showing the operating state of the fifteenth embodiment.

FIG. 42 is a plan view showing the operating state of the fifteenth embodiment.

FIG. 43 is a plan view showing the operating state of the sixteenth embodiment of the optical head according to the present invention.

FIG. 44 is a plan view showing an operating state of the sixteenth embodiment.

FIG. 45 is a diagram showing the main configuration of a seventeenth embodiment of the optical head according to the present invention.

FIG. 46 is a schematic diagram showing comparison between cases where specifications of an objective lens and an optical disc are different.

FIG. 47 is a view showing a typical cross-sectional shape of objective lenses made of different glass materials.

FIG. 48 is a diagram showing a detailed structure of a lens actuator in a seventeenth embodiment.

FIG. 49 is a view showing the shape of the tracking coil provided on the rotary blade in the seventeenth embodiment.

FIG. 50 is a diagram showing a more detailed structure of the lens actuator in the seventeenth embodiment.

FIG. 51 is a diagram showing a waveform of a current passed through a tracking coil for selecting a plurality of objective lenses provided on the rotary blade in the seventeenth example.

FIG. 52 is a diagram showing the main configuration of an eighteenth embodiment of the optical head according to the present invention.

FIG. 53 is a diagram showing the main configuration of a nineteenth embodiment of the optical head according to the present invention.

FIG. 54 is a diagram showing a main configuration of a twentieth embodiment of the optical head according to the present invention.

FIG. 55 is a diagram showing a main configuration of a twenty-first embodiment of the optical head according to the present invention.

FIG. 56 is a diagram showing the mutual relation of the first specifications of the two objective lenses in the seventeenth to twenty-first examples.

FIG. 57 is a diagram showing the mutual relationship of the second specifications of the two objective lenses in the seventeenth to twenty-first examples.

FIG. 58 is a schematic diagram for explaining an adjusting method of the optical head device in the seventeenth to twenty-first embodiments.

FIG. 59 is a diagram showing the relationship between wavefront aberration and inclination when the substrates of the optical discs are different in the 17th to 21st examples.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk device, 10 ... Optical disk, 12 ... Spindle motor, 14a, 14b ... Objective lens, 16 ... Standup mirror, 18 ... Moving optical system, 20 ... Pickup, 2
2 ... Fixed optical unit, 42 ... Control part.

Claims (4)

[Claims] 1. An optical head comprising: a plurality of objective lenses for irradiating a recording medium with light; and means for selecting one desired objective lens from the plurality of objective lenses. apparatus. 2. A movable body that is movable in the thickness direction of the recording medium and in a direction orthogonal to the thickness direction, a plurality of objective lenses that irradiate the recording medium with light from a light source mounted on the movable body, and the recording medium. And an objective lens switching means for selecting a predetermined objective lens from among the plurality of objective lenses according to the type and interposing the objective lens in the optical path of the light. 3. A movable body having a magnet and movable in a thickness direction of the recording medium and a direction orthogonal to the thickness direction, and a plurality of objective lenses for irradiating the recording medium with light from a light source mounted on the movable body. A coil means arranged around the movable body for driving the movable body at least in a direction orthogonal to the thickness direction, and a predetermined objective lens among the plurality of objective lenses according to the type of the recording medium. And an objective-lens switching means for selecting and intervening in the optical path of the light. 4. A fixed optical system including a light source and a detection system for detecting reflected light from the recording medium, the fixed optical system being provided at a fixed position with respect to the recording medium, and the irradiation of the light from the light source onto the recording medium by focusing. A plurality of objective lenses for supporting the plurality of objective lenses, and a movable supporting means that supports the plurality of objective lenses and is movably provided in a plane parallel to the recording medium; and by controlling the movement of the movable supporting means, And a control means for selectively fixing a desired one of the objective lenses on the recording medium onto the optical axis of the light.