JPH11353678A - Objective lens driving device and optical disk device using the same - Google Patents

Abstract

(57) [Problem] To provide a tilt control method of an objective lens required for a high-density optical disk device, a separate mechanism is required for tilt control, and the increased number of components may disturb the frequency characteristics of the drive device. Has become. Therefore, an object of the present invention is to provide an objective lens driving device capable of controlling the tilt of an objective lens by using the same components as those of the conventional movable part. An object lens is tilted by providing a plurality of auxiliary coils and adjusting a current flowing through the auxiliary coil according to a tilt amount of a sensor for detecting a tilt of the objective lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used for an optical disk, a magneto-optical disk, a CD-ROM device, etc. for optically recording or reading information on an information recording medium, and an optical disk using the same. Related to the device.

[0002]

2. Description of the Related Art An optical disk device used as a compact disk device or a recording device for a computer has been increasing in density. The methods for increasing the density include miniaturizing the light spot by increasing the numerical aperture of the objective lens and shortening the wavelength of the semiconductor laser, improving the density in the radial direction by land and groove recording, multilayer recording, super-resolution technology, and signal processing. Technology is proposed and applied.

[0003] Among them, the enlargement of the numerical aperture of the objective lens and the shortening of the wavelength of the semiconductor laser are the most direct methods for increasing the density. However, as the numerical aperture of the objective lens increases,
There is a problem that the influence of aberration due to the inclination between the recording surface of the optical disc and the optical axis of the objective lens sharply increases, and the signal recording / reproducing characteristics deteriorate. Therefore, when the numerical aperture of the objective lens is increased in order to increase the density, it is necessary to detect and correct the inclination of the recording medium and the optical axis.

In a conventional objective lens driving device, for example, as shown in Japanese Patent Application Laid-Open No. 6-162540, a separate tilt coil is attached to a movable portion, and a current is applied to the tilt coil to generate a force in a tilt direction. And tilted the objective lens.

[0005]

However, in the above-described method of controlling the tilt of the objective lens, since a coil for controlling the tilt is required in the movable section, the number of lead wires for supplying current to the movable section is increased as compared with the prior art. For this reason, the four-suspension objective lens driving device cannot be shared as a current supply lead wire for the suspension, and requires a separate component such as a flexible substrate. This separate component acts as an external force to the movable part of the objective lens driving device and causes frequency characteristics to be disturbed, so that it is not suitable for a high-density optical disk device. Similarly, the shaft-sliding type objective lens driving device has a problem in that the deformation resistance increases due to an increase in the width of the flexible substrate due to an increase in the lead wires, and the objective lens is tilted.

In view of the above problems, an object of the present invention is to provide an objective lens driving device capable of controlling the tilt of an objective lens by using a conventional movable component, and an optical disk device equipped with the same. It is in.

[0007]

According to the present invention, a yoke, a magnet, and a focus for finely moving an objective lens in a focus direction and a tracking direction are provided on an optical head that moves roughly in a radial direction with respect to a recording medium. coil,
An objective lens driving device comprising a movable portion including a tracking coil and an objective lens, and a support member for holding the movable portion has a recording medium or a sensor for detecting a tilt between the recording medium and the objective lens, and a magnetic sensor is provided in accordance with the amount of the sensor. A configuration is provided in which control means is provided for supplying current to a plurality of auxiliary coils provided beside the circuit.

In addition, instead of the sensor signal, the inclination of the recording medium or the recording medium and the objective lens is detected from the reproduction signal output of the return light from the laser light, and a plurality of inclinations are provided beside the magnetic circuit in accordance with the amount. A configuration is provided in which control means for flowing a current to the auxiliary coil is provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present embodiment will be described below with reference to FIGS.

FIG. 1 is an external view of an optical disk (CD-ROM) device using one embodiment of the present invention. The optical disk device performs an operation of placing a disk 1 as a recording medium on a disk tray 3 and sending it into the device (or taking it out of the device) by a disk loading mechanism (not shown). The disk 1 is magnetically attracted and fixed to a turntable 2 of a spindle motor 40 by a clamper 4 attached to a clamper holder 5.

The disk 1 starts rotating at a predetermined number of revolutions by a spindle motor, and information is written on or read from the disk 1 by an optical head 9 provided in a unit mechanical chassis 6 disposed below the disk 1. I do.

An optical head 9 has an objective lens driving device 10
The optical head 9 is mounted on the unit mechanical chassis 6 so as to be able to move roughly in the radial direction of the disk 1. The unit mechanical chassis 6 is mounted via vibration-proof legs 8a to 8d formed of a mechanical base 7 and an elastic member. A bottom cover 11 and a top cover 12 are attached to the entire apparatus.

FIG. 2 is an external view of an objective lens driving device having a plurality of auxiliary coils 22a to 22d according to an embodiment of the present invention. The Z axis in the optical axis direction of the objective lens 13 is defined as a focus direction, and the Y axis in the disk radial direction is defined as a tracking direction.

The objective lens 13 is held by a lens holding member 14 made of a high-rigidity plastic non-magnetic material such as polycarbonate. The air-core coil-shaped focus coil 15 is disposed on the lens holding member 14 in a ZX plane symmetrical manner, and flat coil-shaped tracking coils 16a and 16b are disposed on one surface thereof in a ZX plane symmetrical manner. The focus coil 15 and the tracking coil 1
A magnetic circuit is formed by a yoke 17 made of a magnetic material such as iron and magnets 18a and 18b for forming a magnetic field so that the surface on which 6a and 16b are present is a gap. The facing magnets 18a and 18b are arranged such that their magnetic poles are in series as shown in FIG. 2, and auxiliary coils 22a to 22d are arranged on the left and right of the magnets 18a and 18b.

The coils of the auxiliary coils 22a to 22d are wound so that the magnetic poles of the opposing auxiliary coil 22a and the auxiliary coil 22b or the magnetic poles of the auxiliary coil 22c and the auxiliary coil 22d are connected in series.
The magnetic pole directions of b and the right auxiliary coils 22c and 22d are connected in series in opposite directions. At this time, the winding method and the connection method of the coil may be arbitrarily set, and a magnetic member may be provided at the center of the auxiliary coil, or the magnetic member may be integrated with the yoke 17.

The two sides of the lens holding member 14 are symmetric with respect to the Y axis.
Small boards 19a and 19b are arranged, and suspensions 21a to 21d made of a spring material such as a phosphor bronze wire having a diameter of about 0.1 mm are arranged between the suspension mounting boards 20 symmetrically in the ZX plane and the XY plane and parallel to each other. It is fixed by soldering or the like.

Further, the objective lens 13 and the horizontal lens holding member 1
4 is a sensor 23 for detecting the inclination of the recording medium and the objective lens.
Is provided. This sensor irradiates the light of the light emitting element to the recording medium, detects the amount of light by the light receiving element divided into two in the y-axis direction in which the inclination of the return light is detected, and determines the difference between the two divided light amounts. This is a sensor that detects the amount of tilt. The inclination detecting means of the sensor may be arbitrarily set, such as a contact type, and the sensor mass is arranged in consideration of the installation location such that the position of the center of gravity of the movable portion coincides with the drive center or the support center. Further, a sensor or the like may be used as the balance weight.

Here, as shown in FIG. 3, the sensor 22 may be provided on the optical head 9 near the objective lens 13 on the fixed portion side.

The suspensions 21a to 21d may be used as the current supply lead wires of each coil, and in this case, the ground of each coil may be shared.

In the present invention, by arranging the auxiliary coils 22a to 22d beside the conventional magnetic circuit, an objective lens driving device capable of controlling the inclination of the objective lens 13 without changing the configuration of the movable part can be obtained.

FIG. 4 shows the principle of tilting the objective lens 13 by the auxiliary coils 22a to 22d. A magnetic flux 24 is generated by the illustrated magnets 18 a and 18 b, and when a current 25 is applied to the focus coil 15, a focus driving force 26 according to Fleming's law is generated. The magnetic flux density distribution in the magnetic circuit gap at this time is a symmetric distribution state as shown by the dotted line on the lower side of FIG.

Next, when currents 28a to 28d are applied to the auxiliary coils 22a to 22d so as to generate an auxiliary magnetic field as shown in the figure, the gap magnetic flux is disturbed, and the magnetic flux density is reduced as shown by the solid line on the lower side of FIG. The left front is large, the right back of the paper is small, and the distribution state is asymmetric. Therefore, a difference occurs between the focus driving forces 29a and 29b generated by the left and right magnetic fluxes 27a and 27b, and the difference generates a moment force 30 centered on the center of gravity.
With 0, the objective lens 13 can be tilted. At this time, the magnetic force of the auxiliary coils 22a to 22d may be sufficiently increased, and the directions of the left and right magnetic fluxes 27a and 27b may be reversed.

At this time, current can be separately applied to the left and right auxiliary magnets 22a and 22b and the auxiliary magnets 22c and 22d, and the current is applied so that the magnetic pole direction is the same as that of the magnets 18a and 18b.
When 28a to 28d are applied, the magnetic flux density 24 becomes
2a to 22d are larger than before use, and the focus driving force 26 is large, in other words, a high sensitivity objective lens driving device.

Therefore, by providing a difference between the current 23a and the current 23b according to the detection amount of the above-described recording medium or the sensor 23 for detecting the inclination of the recording medium and the objective lens 13, the recording medium and the objective lens 13 Can be eliminated.

FIGS. 5 and 6 show another embodiment using the auxiliary coil of the present invention.

FIG. 5 is substantially the same as the embodiment of FIG.
The auxiliary coils 32a and 32b are connected to the magnet 3 on the objective lens 13 side.
1a. At this time, the magnet provided with the auxiliary coil may be the rear magnet 31b, and the magnet may be one on each side.

FIG. 6 shows an arrangement in which the objective lens 13 is arranged on the support center of the lens holding member 33. Focus coils 34a and 34b in the form of air-core coils are provided on two opposite sides of the lens holding member 33 with YZ and ZX. The tracking coils 35a, 35b and the tracking coils 35c, 35d in the form of flat coils are arranged on one surface thereof in a plane symmetrical manner, and are arranged in YZ and ZX plane symmetry. A yoke 36 made of a magnetic material and a magnet 37a are formed so that a gap between the surface where the focus coil 34a and the tracking coils 35a and 35b are present and a surface where the focus coil 34b and the tracking coils 35c and 35d are present.
37d form a magnetic circuit. The facing magnets 37a and 37b and the magnets 37c and 37d
Are arranged such that their magnetic poles are in series, and the magnets 37a
Auxiliary coils 41a to 41h are arranged on the left and right of to 37d.

The auxiliary coils 41a to 41h are composed of the auxiliary coil 41a and the auxiliary coil 42b facing each other, or the auxiliary coil 41c and the auxiliary coil 41d and the auxiliary coil 41e.
And the auxiliary coil 41f and the auxiliary coil 41g and the auxiliary coil 41h are wound so that the magnetic poles thereof are connected in series.
The magnetic pole directions of c and 41d are connected in opposite directions, and the magnetic pole directions of the left auxiliary coils 41e and 41f and the right auxiliary coils 41g and 41h are connected in opposite directions. At this time, the winding and connection method of the coil may be arbitrarily set, and a magnetic member may be provided at the center of the auxiliary coil, or the magnetic member may be integrated with the yoke 36.

The two sides of the lens holding member 33 are symmetric with respect to the Y axis.
Small boards 38a and 38b are arranged, and suspensions 40a to 40d made of a spring material having a diameter of about 0.1 mm are arranged between suspension mounting boards 39 symmetrically in the ZX plane and the XY plane and parallel to each other, and fixed by soldering or the like. It was done.

Further, the objective lens 13 and the horizontal lens holding member 3
A sensor 23 for detecting the inclination of the recording medium and the objective lens;
Is provided. The inclination detecting means of the sensor may be arbitrarily set, such as a contact type, and the sensor mass is arranged in consideration of the installation location such that the position of the center of gravity of the movable portion coincides with the drive center or the support center. Further, the sensor may be used as a balance weight. A sensor may be provided on the optical head 9 near the objective lens 13 on the fixed part side. Suspensions 21a to 21d may be used as current supply lead wires for each coil, and in that case, the ground of each coil may be shared.

FIG. 7 is a schematic configuration diagram for controlling the inclination of the objective lens 13. The light emitted from the semiconductor laser 42 becomes parallel light by the collimator lens 43, passes through the beam splitter 44, is reflected by the rising mirror 45, and is condensed on the recording surface of the disk 1 by the objective lens 13. The light reflected by the disk 1 passes through the objective lens 13 and the rising mirror 31 again, and passes through the beam splitter 4.
The light is reflected at 4 and guided to a detection optical system 46, where a focus error signal 47, a track error signal 48, and a reproduction signal 49 are detected. In FIG. 6, the collimator lens 4
Although the present invention is shown as an infinite optical system using No. 3, the present invention is not limited to this, and may be a finite optical system as used in a compact disc.

The focus error signal 47 and the tracking error signal 48 are detected by a known technique, for example, by an astigmatism method and a push-pull method. Playback signal 49
Is detected, for example, in a compact disk or the like from a change in intensity due to the presence or absence of pits on the disk 1. At that time,
The detection method may be any method.

The detected focus error signal 47 is
If necessary, an offset amount is added from the controller 50 to provide a control signal for driving the movable section including the objective lens 13 in the optical axis direction (focus direction), and the movable section including the objective lens 13 is driven by this signal. Then, the focal point of the light spot is made to follow the recording surface of the disk 1.

Similarly, the detected track error signal 4
Reference numeral 8 denotes a control signal for driving the movable section including the objective lens 13 in the disk radial direction to which an offset amount is added from the controller 50 if necessary. , And causes the light spot to follow the track of the disk 1.

Here, the tilt of the objective lens 13 is controlled by a tilt signal 51 detected by a recording medium provided beside the objective lens 13 and a sensor 23 for detecting the tilt of the objective lens and a tilt control signal from the controller 50. , Auxiliary coil 2
A control signal 52 for driving 2a to 22d is provided, and the movable portion including the objective lens 13 is driven, so that the light spot can be made to follow the recording surface of the disk 1 so that the inclination of the objective lens 13 and the disk 1 is eliminated.

Further, instead of the tilt signal 51 of the sensor 23, a change in the coma aberration of the light generated by tilting the movable portion including the objective lens 13 with respect to the disk 1 can be used as the tilt signal. . Hereinafter, a method of detecting the inclination will be described with reference to FIG.

Assuming that the disc 1 is inclined by θ with respect to the objective lens 13 and the inclination of the objective lens 13 is changed by the above-described method, the reproduced signal changes in accordance with the inclination of the disc 1 and the objective lens 13. At this time, when the inclination of the disc 1 and the objective lens 13 is almost zero, the output of the reproduction signal is maximized. Therefore, by observing the fluctuation of the reproduction signal, the inclination of the disc 1 and the objective lens 13 can be detected.

According to the amount of tilt, the auxiliary coils 22a to 22d are driven as described above to cause the focal point of the light spot to follow the recording surface of the disk 1, and the objective lens 13
And the disk 1 can be made to substantially follow the inclination.

Here, the method of detecting the inclination between the disk 1 and the objective lens 13 is arbitrary.

By the means described above, an objective lens driving device for substantially eliminating the inclination between the recording medium and the objective lens 13 and an optical disk device equipped with the same may be provided.

[0041]

By controlling the current flowing through the auxiliary coil of the present invention described above, the objective lens can be arbitrarily tilted, and the tilt between the recording medium and the objective lens can be constantly eliminated. As a result, it is possible to provide an objective lens driving device capable of properly reproducing signals from a recording medium and correctly recording.

In addition, since an auxiliary coil is provided in the fixed portion,
Since the inclination of the objective lens can be controlled without increasing the number of parts of the movable portion, a conventional reproduction procedure of the recording medium with a good assembling procedure and accuracy and an objective lens driving device capable of correctly recording can be obtained.

By mounting the objective lens driving device, an optical disk device capable of reading a high-density disk can be obtained.

[Brief description of the drawings]

FIG. 1 is an external perspective view of an optical disk device using one embodiment of the present invention.

FIG. 2 is an external perspective view of an objective lens driving device using one embodiment of the present invention.

FIG. 3 is an external perspective view of a mechanism in which a sensor is provided on an optical head.

FIG. 4 is an exploded perspective view illustrating the principle of tilting an objective lens by an auxiliary coil.

FIG. 5 is an external perspective view of an objective lens driving device using one embodiment of the present invention.

FIG. 6 is an external perspective view of an objective lens driving device using one embodiment of the present invention.

FIG. 7 is a schematic configuration diagram for controlling the tilt of the objective lens.

FIG. 8 is an explanatory diagram of tilt detection using a signal output.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disc, 2 ... Turntable, 3 ... Disc tray, 4 ... Clamper, 5 ... Clamper holder, 6 ... Unit mechanical chassis, 7 ... Mechanical base, 8a-8d ... Vibration proof legs, 9 ... Optical head, 10 ... Objective lens Drive device, 11 ...
Bottom cover, 12 top cover, 13 objective lens, 14 lens holding member, 15a focus coil, 16a, 16b tracking coil, 17 yoke, 18a, 18b magnet, 19a, 19b small board,
20 ... Suspension mounting board, 21a-21d ...
Suspensions, 22a to 22d ... auxiliary coils, 23 ...
Sensor, 24 magnetic flux, 25 current, 26 focus driving force, 27a, 27b magnetic flux, 28a to 28d current,
29a, 29b: focus driving force, 30: moment force, 31a, 31b: magnet, 32a, 32b: auxiliary coil, 33: lens holding member, 34a, 34b: focus coil, 35a to 35d: tracking coil, 36
... Yoke, 38a, 38b ... Small board, 39 ... Suspension mounting board, 40a-40d ... Suspension,
41a to 41h: auxiliary coil, 42: semiconductor laser, 4
3 ... collimating lens, 44 ... beam splitter, 45
.., Rising mirror, 46, detection optical system, 47, focus error signal, 48, track error signal, 49, reproduction signal, 50, controller, 51, tilt signal, 52, control signal, 53, spindle motor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division of Hitachi, Ltd. (72) Inventor Akio Yabe Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa 292 Hitachi Image Information Systems, Ltd. (72) Inventor Shinya Fujimori 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture, Japan Multimedia Systems Development Division, Hitachi, Ltd. (72) Inventor Nobuyuki Maeda Totsuka, Yokohama-shi, Kanagawa 292 Yoshida-cho, Ward Inside Multimedia System Development Division, Hitachi, Ltd.

Claims (1)

[Claims] 1. A yoke, a magnet, a focus coil, and a yoke for finely moving an objective lens in a focus direction and a tracking direction on an optical head that moves roughly in a radial direction with respect to a recording medium.
A movable portion including a tracking coil and an objective lens, an objective lens driving device including a support member that holds the movable portion, and an optical disc device equipped with the same, a recording medium or a sensor that detects a tilt of the recording medium and the objective lens is provided; An objective lens driving device which corrects the inclination between a recording medium and an objective lens by flowing a current through a plurality of auxiliary coils in accordance with the detected tilt amount of the sensor.