JPH11312327A - Objective lens drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always eliminate the inclination between a recording medium and an objective lens by detecting the inclination of the recording medium or between the recording medium and the objective lens and adjusting respective currents flowing through two pieces of focus coils based on the detected inclination. SOLUTION: Focus drive force 24a is generated in the focus coil 15a for a flow of magnetic flux 38a by the current 23a, and moment of force 26a is generated around a support center 25. Similarly, the focus drive force 24b is generated by the magnetic flux 38b and the current 23b, and the moment of force 26b is generated. Thus, the moment of force 27 applied to a movable part containing the objective lens becomes the sum of the currents 23a and 23b, and the moment of force 27 is changed in the direction and the amount according to a difference between the currents 23a and 23b. At this time, since the sum of the whole currents becomes the focus drive force of the movable part, the moment of force 27 is changed while following the focus 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, the above-described method of controlling the tilt of the objective lens requires a separate mechanism for controlling the tilt of the objective lens, and is not always sufficient in terms of cost reduction such as an increase in the number of parts.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an objective lens driving device capable of controlling the inclination of an objective lens with conventional components and an optical disk device equipped with the same. .

[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 part including a tracking coil and an objective lens, and a support member for holding the movable part has a recording medium or a sensor for detecting the inclination of the recording medium and the objective lens. It is configured to have control means for adjusting each current flowing through the focus coils.

In addition, instead of the signal from the sensor, 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.
It is configured to have control means for adjusting each current flowing through the focus coils.

[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 to rotate at a predetermined number of revolutions by the spindle motor 40, and the optical head 9 provided in the unit mechanical chassis 6 disposed below the disk 1.
Thus, information is written on or read from the disk 1.

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 two focus coils 15a and 15b 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 coils 15a and 15b
The tracking coil 16 having a flat coil shape is disposed symmetrically in the XX plane on one surface thereof. A magnetic circuit is formed by a yoke 17 made of a magnetic material such as iron and magnets 18a to 18d for forming a magnetic field so that a surface where the focus coils 15a and 15b and the tracking coil 16 are present is a gap.

The facing magnets 18a and 18b or the magnets 18c and 18d are arranged such that the magnetic poles are arranged in series as shown in FIG.
a and the magnet 18c or the magnets 18b and 18d have their magnetic poles arranged in opposite directions. Therefore, the magnetic circuit requires two focus coils 15a and 15b, but one tracking coil 16 can ensure the same driving force as the conventional one.

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.

The lens holding member 14 beside the objective lens 13 is provided with a sensor 22 for detecting a tilt between the recording medium and the objective lens. This sensor irradiates a recording medium with light from a light emitting element, and detects a tilt y of the return light.
This sensor detects the amount of light with a light receiving element divided into two in the axial direction, and detects the amount of tilt based on the difference between the two divided light amounts. 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.

Suspensions 21a to 21d may be used as current supply lead wires for each coil. In this case, the ground of each coil is shared, and three leads are used for the four lead wires.
By controlling one coil, an objective lens driving device capable of controlling the tilt of the objective lens 13 with the conventional number of suspensions may be used.

The magnets 18a and 18c are two-pole magnetized
Magnets and the yoke 1 on the back of the magnets 18a, 18c
7 may be divided, and the magnet may be formed on only one side of the magnetic circuit, for example, a magnetic circuit excluding the magnets 18a and 18c.

According to the present invention, although there is a difference between a conventional focus coil and two tracking coils and two focus coils and one tracking coil, the objective lens driving device can be constructed with substantially the same number of parts. That is,
An objective lens driving device capable of controlling the tilt of the objective lens 13 can be provided without increasing the cost.

FIG. 4 shows focus coils 15a and 15b.
Shows the principle that the objective lens 13 is tilted. With respect to the flow of the magnetic flux 38a shown in FIG.
As a result, a focus coil driving force 24a based on Fleming's law is generated in the focus coil 15a, and a moment force 126a about the support center 25 is generated.
Similarly, the focus driving force 24b is generated by the magnetic flux 38b and the current 23b, and the moment force 26b is generated.

Therefore, the moment force 27 applied to the movable portion including the objective lens 13 is the sum of the moment force 26a and the moment force 26b. This moment force 27
Can change the direction and amount by the difference between the current 23a and the current 23b. At that time, since the sum of the entire currents becomes the focus driving force of the movable portion, it is possible to change the moment force 27 while following the focal point of the objective lens 13.

Therefore, by providing a difference between the current 23a and the current 23b in accordance with the detection amount of the recording medium or the sensor for detecting the inclination of the recording medium and the objective lens, the inclination of the recording medium and the objective lens 13 is determined. Can be eliminated.

FIG. 5 shows a schematic configuration diagram for controlling the inclination of the objective lens 13. The light emitted from the semiconductor laser 28 becomes parallel light by the collimator lens 29, passes through the beam splitter 30, is reflected by the rising mirror 31, 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 3.
The light is reflected at 0 and guided to the detection optical system 32, where a focus error signal 33, a track error signal 34, and a reproduction signal 35 are detected. In FIG. 4, the collimator lens 2
Although shown as an infinite optical system using No. 9, the present invention is not limited to this, and may be a finite optical system as used in compact discs.

The focus error signal 33 and the tracking error signal 34 are detected by a known technique, for example, by an astigmatism method and a push-pull method. Playback signal 35
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 33 is
If necessary, an offset amount is added from the controller 36 to provide a control signal for driving the movable portion including the objective lens 13 in the optical axis direction (focus direction), and this signal drives the movable portion including the objective lens 13. 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 3
Reference numeral 4 denotes a control signal for driving the movable portion including the objective lens 13 in the disk radial direction, to which an offset amount is added from the controller 36 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 based on a tilt signal 37 detected by the recording medium provided beside the objective lens 13 and the sensor 22 for detecting the tilt of the objective lens and a focus control signal from the controller 36. It becomes a control signal 39 for driving the two focus coils 15a and 15b, the movable part including the objective lens 13 is driven, and the focus of the light spot follows the recording surface of the disk 1 and
It is possible to follow the objective lens 13 and the disk 1 so as to eliminate the inclination.

Further, instead of the tilt signal 37 of the sensor 22, a change in coma of light generated by tilting the movable portion including the objective lens 13 with respect to the disk 1 can be used as a 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 reproduction 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.

The two focus coils 15a and 15b are driven by the amount of inclination to drive the disc 1 as described above.
The focus of the light spot can be made to follow the recording surface, and the objective lens 13 and the disk 1 can be made to follow so that the inclination of the disc is not reduced.

Here, the method of detecting the tilt between the disk 1 and the objective lens 13 is arbitrary, and the current 23a and the current 2 flowing through the two focus coils 15a and 15b are determined according to the amount of tilt.
By providing a difference in 3b, an objective lens driving device that substantially eliminates the inclination between the recording medium and the objective lens 13 and an optical disk device equipped with the objective lens driving device may be used.

[0034]

By controlling the current flowing through the two focus coils 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.

Further, by using a common ground for the suspension that also serves as the current supply lead wire for the coil, the inclination of the objective lens can be suppressed with the conventional objective lens actuator components, so that the cost can be reduced without increasing the number of components. The objective lens driving device can perform a good reproduction signal of the recording medium and record correctly with the apparatus kept as it is.

Further, 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 a view for explaining the principle of tilting an objective lens by a focus coil.

FIG. 5 is a schematic configuration diagram for controlling the tilt of the objective lens.

FIG. 6 is a diagram illustrating inclination 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, 15b focus coil, 16 tracking coil, 17 yoke,
18a to 18d: magnet, 19a, 19b: small substrate, 20
... Suspension mounting board, 21a-21d ... Suspension, 22 ... Sensor, 23a, 23b ... Current, 2
4a, 24b: Focus driving force, 25: Support center, 2
6a, 26b: moment force, 27: moment force, 2
Reference Signs List 8: semiconductor laser, 29: collimating lens, 30: beam splitter, 31: rising mirror, 32: detection optical system, 33: focus error signal, 34: track error signal, 35: reproduction signal, 36: controller, 37
... tilt signal, 38a, 38b ... magnetic flux, 39 ... control signal,
40 ... Spindle motor.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Video Information Media Division (72) Inventor Nobuyuki Maeda Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa 292 Hitachi Multimedia Systems Development Division

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.
In an objective lens driving device including a movable portion including a tracking coil and an objective lens, and a support member holding the movable portion, and an optical disk device equipped with the same, the focus coil includes two coils, and a recording medium or a recording medium And a sensor for detecting the tilt of the objective lens, and correcting the tilt between the recording medium and the objective lens by adjusting each current flowing through the two focus coils according to the tilt detection amount of the sensor. Objective lens driving device.