JPH1116176A - Optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate the actuator of an objective lens for tracking and to make a simple uniaxial actuator for focusing by controlling a voltage to be applied upon and electro-optical deflector with a tracking error signal generated by a detecting system. SOLUTION: A voltage is applied upon an electro-optical deflector 3 based on a tracking error signal generated by a detecting system. When the voltage is not applied at all, the electro-optical deflector 3 advances incident light straight as it is. Moreover, when an arbitrary voltage ±V is applied, the incident light is inclined in the tracking direction by an angle ±θcorresponding to this voltage and is emitted. Consequently, by controlling the voltage to be applied upon the electro-optical deflector 3 in accordance with the tracking error signal, the operation of a mechanical tracking actuator can be substituted, and moreover, the useless vibration of an objective lens to be generated at the time of high speed access can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device of an optical disk device for optically recording and reproducing information on a recording medium, and more particularly to a tracking control device for causing an objective lens of the optical head device to follow a target track. About.

[0002]

2. Description of the Related Art FIG. 6 shows the simplest structure of an optical pickup of a conventional general optical disk device.

FIG. 6 shows a semiconductor laser as a light source.
The light emitted from 201 passes through a diffraction grating 202, is reflected by a parallel plate 203, is condensed by an objective lens 205, and has a main beam for recording and reproducing information on a disk 206 and a tracking error signal. And a sub-beam for obtaining Here, the diffraction grating 202 is provided for forming a sub-beam on the disk 206 for obtaining a tracking error signal. Also, the objective lens 205
The actuator 204 is movable in two directions, a focus direction and a radial direction, in order to focus on the disk 206 and to enable the beam to follow the target track with respect to the eccentricity of the disk, turntable, or the like. It is installed in.

As described above, the conventional optical pickup uses an actuator for performing tracking, and thus requires a two-axis actuator for focus and track.

[0005] There is disclosed a proposal in which another method is employed to cause the objective lens to follow the eccentricity of a spindle motor, a disk, or the like without using such a two-axis actuator.

One example is disclosed in Japanese Patent Application Laid-Open No. 63-29372.
An optical disk device disclosed in Japanese Patent Publication No. 7 will be described with reference to FIG.

[0007] Linearly polarized light (tentatively referred to as X direction) emitted from a semiconductor laser 102 as a light source is collimated by a collimating lens 10.
3. After passing through the polarizing beam splitter 104, the light passes through an electro-optical deflector 113 provided between the polarizing beam splitter 104 and the λ / 4 plate 105. The electro-optical deflector 113 is connected to parallel transparent electrodes 117 and 118 connected to a power supply 116 of variable applied voltage. The light that has passed through the electro-optical deflector 113 becomes circularly polarized when passing through the λ / 4 plate 105, and
It is focused and irradiated on seven surfaces. Then, the light reflected from the surface of the optical disk 107 returns to the objective lens 106 and the λ / 4 plate 10 again.
5 passes in the opposite direction and becomes linearly polarized light inclined at 90 degrees from the first light. The linearly polarized light further passes through the electro-optical deflector 113, and is reflected by the polarization beam splitter 104 in a direction in which the light is separated from the incident light by the polarization plane 104a.
Then, the light is condensed by the detection lens 108, polarized by the knife edge 109 having a prism structure, and irradiated on the light receiving element 110 for a track. A focusing light receiving element 111 is provided in the direction in which the knife edge 109 moves straight.

When the linearly polarized laser light emitted from the light source passes through the electro-optical deflector 113, it is deflected by a voltage applied between the electrodes 117 and 118 in accordance with an external control signal. As a result, the electro-optical deflector 11
3 can be swept between tracks on the optical disc 107. At this time, the incident light on the optical disk 107 is circularly deflected by the λ / 4 plate 105 and then condensed by the objective lens 106. On the other hand, the reflected light from the optical disk 107 passes through the λ / 4 plate 105 again, becomes linearly polarized light different from the incident light by 90 degrees, and is incident again on the electro-optical deflector 113. Thereafter, the light is reflected by the deflection film 104a toward the detection system.

That is, in this apparatus, an electro-optical deflector is provided between a deflection beam splitter and a λ / 4 plate,
It is characterized in that tracking control is performed. The electro-optical light deflector and the deflection beam splitter are adhered by an adhesive.

Japanese Patent Application Laid-Open No. 64-1042 discloses an optical deflector provided in a light source section for controlling tracking.
Japanese Patent Application Publication No. JP-A-2005-17753 discloses an external resonator type laser that oscillates at a light source section at an arbitrary frequency within a laser gain band, a frequency filter provided in the resonator and having a variable transmission frequency, and a grating that passes oscillation output light. An optical disc device provided with an optical deflector comprising:

An optical head device using an acousto-optical deflector for controlling the tracking direction is disclosed in Japanese Utility Model Laid-Open Publication No. 61-140.
No. 434. This optical head device
The acousto-optic light deflector is located on the optical axis of the collimating lens between the half prism and the collimating lens, and is inclined with respect to the optical axis of the objective lens by an angle θ in the tracking control direction. Thus, the control of the tracking direction is performed by the first-order diffracted light of the acousto-optic light deflector.

[0012]

In the case of using a two-axis actuator that operates electrically and mechanically to drive the above-mentioned objective lens, there is a limit to miniaturization of the actuator and simplification of the configuration.

In order to improve the access speed,
When the feed speed of the optical pickup is increased, if a mechanically configured two-axis actuator is used, when the target position is accessed and stopped, the radial direction of the recording medium is reduced due to the inertia of the objective lens. The objective lens causes unnecessary shake, causing a malfunction in the access operation, and the access time becomes longer.

On the other hand, without using a biaxial actuator, λ
In the above-described conventional apparatus using the / 4 plate and the electro-optical deflector, the electro-optical deflector must be bonded to the polarizing beam splitter and disposed between the λ / 4 plate, There are restrictions on its location. Further, since the λ / 4 plate cannot be removed, there is a problem that the number of parts increases and the device becomes large.

An object of the present invention is to eliminate a tracking operation by an actuator of an objective lens and to perform a tracking operation in which unnecessary vibration of the objective lens generated at the time of high-speed access is eliminated, and further, a λ / 4 plate is not required. An object of the present invention is to provide an optical head device.

[0016]

SUMMARY OF THE INVENTION An optical head device according to the present invention comprises: an optical path splitting means for guiding light emitted from a light source to an objective lens and guiding light reflected from an information recording medium to a detection system; Provided in the optical path between the and the objective lens,
An electro-optical deflector for deflecting a beam direction in a tracking direction according to an applied voltage; detecting means for detecting a tracking signal, a focusing signal and a recorded information signal from light reflected from an information recording medium; Tracking control means for applying a voltage to the electro-optical deflector according to the tracking signal thus detected; and a focusing actuator for moving the objective lens in the focusing direction according to the detected focusing signal.

The optical path splitting means may be a beam splitter or a parallel plate.

Preferably, the detecting means is a photodetector.

[0019]

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

FIG. 1 is a configuration diagram of an optical head device according to one embodiment of the present invention.

In FIG. 1, this optical head device is equipped with a light source 1 for a semiconductor laser and other optical disks, a beam splitter 2, an electro-optical deflector 3, an objective lens 4, and an objective lens 4. A one-axis actuator 5 for focusing, a detection system 7 for detecting a tracking signal or the like from reflected light, an applied voltage control unit 8 for applying a voltage to the electro-optical deflector 3 according to the detected tracking signal, Having.

The beam splitter 2 is used in an ordinary optical disk device, and is designed, for example, to transmit and reflect 50% of each of a P deflection component and an S deflection component. A parallel flat plate may be used as an alternative to the beam splitter 2.

The electro-optical type optical deflector 3 may be a general type such as described in “Illustration Dictionary of Optical Devices” (Optronics). By applying an arbitrary voltage, the beam is deflected in the tracking direction. Is configured to be able to deflect the direction of

The actuator 5 causes the light spot converged by the objective lens 4 to follow the surface deviation of the optical disk 6 as a recording medium on the disk surface.

The detection system 7 includes a photodetector for receiving the reflected light from the disk, optical components for generating an error signal, and the like. The detection system 7 can obtain a focus error signal, a track error signal, and a reproduction signal. This is the same as a general optical disk detection system.

Next, the operation of this embodiment will be described with reference to the drawings.

In FIG. 1, linearly polarized light emitted from a light source 1 (here, supposed to be P-polarized) passes through a beam splitter 2 and an electro-optical deflector 3 and is passed through an objective lens 4 to an optical disk 6. Form a spot on top. The light reflected by the optical disk 6 is returned to the objective lens 4,
After passing through the electro-optical deflector 3 in the reverse direction, it is guided to the detection system 7 by the beam splitter 2. The detection system 7 generates a focus error signal, a track error signal, and an information reproduction signal from the reflected light.

A voltage is applied to the electro-optical deflector 3 based on the track error signal generated by the detection system 7. Then, the electro-optical deflector 3 changes the direction of light passing therethrough according to the applied voltage, so that the light spot moves in a direction to cancel the track error, and a light spot is generated at a target position on the optical disk. You.

FIG. 2 shows the traveling direction of the light emitted from the electro-optical deflector 3.

When no voltage is applied, the electro-optic light deflector 3 causes the incident light to travel straight as it is, as shown by the solid line. However, when an arbitrary voltage ± V is applied,
As indicated by the dotted line, the incident light is emitted in the tracking direction by an angle ± θ in accordance with the voltage. Therefore,
If the voltage applied to the electro-optical deflector 3 is controlled according to the tracking error signal, the operation of the conventional mechanical tracking actuator can be substituted, and unnecessary vibration of the objective lens generated at the time of high-speed access can be performed. Can be removed.

FIG. 3 shows a state where the light spot follows the target track.

As shown in the upper part of FIG.
If the target track 5 deviates from the target track 30 on the right side of the drawing, an appropriate voltage is applied to the electro-optical deflector 3, for example, (-
V), the light spot 35 moves to the left and irradiates the target track 30 as shown in the lower part of FIG.

(B) As shown above and below, when the light spot 35 is on the target track 30, the applied voltage is set to 0.
Then, the light spot does not move, and is directly irradiated on the target track.

When the light spot 35 deviates from the target track 30 on the left side of the drawing as shown in the upper part of FIG.
Appropriate voltage for the electro-optic light deflector 3, for example (+ V),
Is applied, the light spot 35 moves to the right,
The target track 30 is irradiated as shown in the lower part of (c).

FIG. 4 shows another embodiment of the present invention, in which a parallel plate 20 is used instead of the beam splitter 2 of the embodiment of FIG. Further, a photodetector 21 is used as a specific example of the detection system 7. In the operation of this embodiment, the voltage applied to the electro-optical deflector 3 is controlled based on the tracking error signal generated by the photodetector 21 so that the light spot follows the target track. The operation is the same as that described above.

[0036]

As described above, according to the present invention, the electro-optical deflector is provided in the optical path of the light beam, and the voltage applied to the electro-optical deflector is controlled by the tracking error signal generated by the detection system. This eliminates the need for an actuator for the tracking objective lens, simplifies the actuator with a single axis for focusing, eliminates the tracking operation of the objective lens actuator, and eliminates the need for an objective lens generated during high-speed access. Vibration can be eliminated, and the size of the entire apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical head device according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the electro-optical deflector according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a tracking operation by the electro-optical deflector of the present invention.

FIG. 4 is a configuration diagram of a second embodiment of the present invention.

FIG. 5 is an example of a conventional optical head device.

FIG. 6 is another example of a conventional optical head device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 102, 201 Light source, semiconductor laser 2 Beam splitter 3, 113 Electro-optical deflector 4, 106, 205 Objective lens 5, 204 Actuator 6, 107, 206 Optical disk 7 Detection system 8 Applied voltage control unit 20, 203 Parallel Flat plate 21, 207 Photodetector 30 Target track, target pit 35 Light spot 103 Collimating lens 104 Polarizing beam splitter 104a Polarizing film 105 λ / 4 plate 116 Power supply 108 Detection lens 109 Knife edge 110 Light receiving element for track 111 Light receiving element for focusing 117, 118 Transparent electrode 202 Diffraction grating 207 Photodetector

Claims (4)

[Claims] An information recording medium is irradiated with light emitted from a light source through an objective lens, and a tracking signal, a focusing signal and a recording information signal are detected from the light reflected from the information recording medium to record information. In an optical head device of an optical information recording / reproducing apparatus for performing reproduction, an optical path splitting means for guiding light emitted from a light source to an objective lens and guiding light reflected from an information recording medium to a detection system; Provided in the optical path between the lenses,
An electro-optical deflector for deflecting the beam direction in the tracking direction according to the applied voltage; a tracking signal from light reflected from the information recording medium;
Detecting means for detecting a focusing signal and a recorded information signal; applying voltage control means for applying a voltage to the electro-optical deflector in accordance with the tracking signal detected by the detecting means; and detecting by the detecting means An optical head device comprising: a focusing actuator that moves the objective lens in a focusing direction in accordance with a focusing signal. 2. The optical head device according to claim 1, wherein said optical path dividing means is a beam splitter. 3. The optical head device according to claim 1, wherein said optical path dividing means is a parallel flat plate. 4. The optical head device according to claim 1, wherein said detecting means is a photodetector.