JP3271205B2 - Optical head device - Google Patents

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 capable of recording and / or reproducing information on an optical recording medium such as a magneto-optical recording medium which can be rewritten by magnetic field modulation.

[0002]

2. Description of the Related Art Recently, information has been recorded and / or reproduced on a disk (optical recording medium) as an information recording medium using a light beam. This is achieved by using an optical head device which is relatively movable with respect to a so-called writable optical disk and which records and / or reproduces information signals on the writable optical disk by light passing through an optical system. It becomes possible.

[0003] Among the writable optical discs, there is a so-called magneto-optical disc which can repeatedly write and erase information. This magneto-optical disk has a structure in which a perpendicular magnetic film for forming a recording layer is provided on a surface of a substrate, and the perpendicular magnetic film is further covered with a protective layer, and the whole is formed on a disk. Has become.

For writing information on such a magneto-optical disk, for example, a perpendicular magnetization film at each position of a large number of concentric recording tracks surrounding a central portion thereof is formed by applying a predetermined external magnetic field. Scanning is performed by a light beam modulated in accordance with information, thereby forming a magnetization direction inversion region with a predetermined pattern.

On the other hand, when reading information written on a magneto-optical disk, the perpendicular magnetization film on a recording track is scanned by a light beam having a lower output than when writing information.
The return light beam from the perpendicular magnetization film is detected by the light detection unit, and a read signal corresponding to the information written on the magneto-optical disk, and a tracking error signal and a focusing error signal are obtained from the light detection unit. .

[0006]

In the above-described conventional optical head device, recording light for recording the information signal on the magneto-optical disk and information signal recorded on the magneto-optical disk are provided. Is reproduced by one semiconductor laser such as a laser diode (LD), for example.

FIG. 6 shows a light level at the time of recording and a light level at the time of reproduction. As shown in FIG. 6, light at the time of recording must generate heat at a temperature near the Curie point in order to weaken the coercive force of the perpendicular magnetization film, and is required to have a high level. Conversely, light at the time of reproduction is required to have low energy so as not to affect the coercive force of the perpendicular magnetization film.

Normally, the level of the semiconductor laser is set to a low output level at which light for reproduction is emitted, and the light spot is scanned on the track of the magneto-optical disk. To the level of.

FIG. 7 is an enlarged view of a broken line portion shown in FIG. When the semiconductor laser having originally high output capability outputs low-energy light, noise is generated.
For this reason, conventionally, as shown in FIG. 7, the laser drive current is swung with a high-frequency current of several hundred MHz to reduce noise. The laser driving current generated by the high-frequency current in this way is called a high-frequency superimposed current. In order to generate this high frequency superimposed current, a high frequency superposition circuit was required.

[0010] However, the high-frequency superimposed current from the high-frequency superimposing circuit has generated unnecessary radiation from the semiconductor laser, and has affected the reproduction of information.

In order to suppress the unnecessary side emission, the area around the semiconductor laser and the high-frequency superimposing circuit must be strictly shielded, and the trouble after the test and commercialization has not been stopped.

Further, the reproducing laser light source is always driven, and at the time of recording information, the reproducing light irradiated onto the magneto-optical disk may interfere with the recording light.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and eliminates the need for a high frequency superimposing circuit which has been conventionally required, and enables recording light and reproducing light to be emitted without causing interference. It is intended to provide a head device.

The present invention relates to an optical head device which is movable relative to an optical recording medium and which records and / or reproduces information signals on the optical recording medium by light passing through an optical system. A recording laser light source for emitting recording light for recording the information signal on the optical recording medium, and a reproducing light for reproducing the information signal recorded on the optical recording medium. A reproducing laser light source, and a first element for reproducing a focusing error signal, a tracking error signal and a recorded information signal from return light of the reproducing light emitted from the reproducing laser light source and reflected by the optical recording medium. A light receiving unit and a write signal for recording an information signal from a return light of the recording light emitted from the recording laser light source and reflected by the optical recording medium are monitored. To solve the above problem by having a second light receiving portions of the fit.

Here, a recording laser spot obtained on the optical recording medium by the recording light of the recording laser light source and a reproduction laser spot obtained on the optical recording medium by the reproduction light of the reproduction laser light source. The laser spot is preferably applied to different positions on the optical recording medium.

The first light receiving section and the second light receiving section may be arranged on the same light receiving surface of one photodetector.

Here, the first light receiving section includes a focusing sensor section for obtaining a focusing error signal, a tracking error detection sensor element for obtaining a tracking error signal, and a reproducing section for obtaining a reproducing signal. And a sensor element for signal detection.

Further, the optical system reflects a recording light emitted from the recording laser light source, and transmits the recording light reflected from the first mirror. A second mirror for reflecting the reproduction light emitted from the reproduction laser light source;
The recording light transmitted by the mirror and the reproduction light reflected by the second mirror are both reflected to irradiate the optical recording medium and return light from the optical recording medium is reflected. And a beam splitter for transmitting light.

It is preferable that the optical axes of the recording light reflected by the first mirror and the reproduction light reflected by the second mirror are shifted from each other.

[0020]

The recording light for recording the information signal on the optical recording medium and the reproduction light for reproducing the information signal recorded on the optical recording medium are respectively separated from the laser light source, that is, the recording light. Since the light is emitted from the laser light source and the laser light source for reproduction and is applied to different positions on the optical recording medium, the high frequency superimposing circuit, which has been conventionally required, is not required, and further, light interference does not occur.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical head device according to the present invention will be described below with reference to FIG.

The embodiment shown in FIG. 1 is an optical head device for recording and / or reproducing information signals on and from a magneto-optical disk 1, and a semiconductor laser as a recording laser light source for emitting light for writing. A semiconductor laser (hereinafter, referred to as a reproduction semiconductor laser) 16 as a reproduction laser light source that emits light for reproduction is hereinafter provided. here,
The reproducing semiconductor laser 16 always outputs a reproducing laser beam. The recording semiconductor laser 10 outputs recording laser light only during recording.

First, a recording system using the recording semiconductor laser 10 will be described. The recording semiconductor laser 10 locally heats the perpendicular magnetization film formed on the recording layer on the magneto-optical disk 1 to, for example, a temperature near the Curie point,
This is a high-power laser that emits a laser beam at a level that eliminates the coercive force of this portion.

The laser light emitted from the recording semiconductor laser 10 (hereinafter referred to as recording laser light) is converted into a parallel beam by a collimator lens 11 and reflected by a first half mirror 12. The recording laser light is
In FIG. 1, it is shown by a solid line.

The first half mirror 12 is arranged at an angle θ with respect to a position L at which the recording laser light is reflected at an angle of 90 ° with respect to the incident direction.

The recording laser beam reflected by the first half mirror 12 enters the second half mirror 13. The second half mirror 13 transmits the recording laser light and makes it incident on the beam splitter 14.
The laser beam emitted from the semiconductor laser 16 for reproduction (hereinafter, referred to as laser beam for reproduction) is 90 ° to the incident direction
Is arranged at a position where light is reflected at an angle.

Then, the beam splitter 14 reflects the recording laser light and makes it incident on the objective lens 15. The objective lens 15 irradiates the recording laser light onto the magneto-optical disk 1.

A magnetic head 30 for applying a recording magnetic field is disposed on the back surface of the magneto-optical disk 1 at the position where the recording laser beam is irradiated.

Next, a reproducing system using the reproducing semiconductor laser 16 will be described. The semiconductor laser 16 for reproduction has a magneto-optical effect (so-called magnetic Kerr effect, Faraday effect) in which the linear polarization plane of the laser light is rotated by the direction of magnetization in the perpendicular magnetization film forming the recording layer on the magneto-optical disk 1 for signal reproduction. ), It is not necessary to use a high-power laser, but rather a low-power laser is desired.

The reproducing laser beam emitted from the reproducing semiconductor laser 16 is converted into a parallel beam by the collimator lens 17, separated into three light flux components by the diffraction grating 18, and reaches the second half mirror 13. . Note that the reproduction laser light is indicated by a broken line in FIG.

As described above, the second half mirror 13 converts the reproduction laser beam to an angle of 90 degrees with respect to the incident direction.
The optical axes of the transmitted recording laser light and the reflected reproduction laser light are shifted by an angle θ from each other since they are arranged at positions where the reflection laser light is reflected at an angle of °.

The reproduction laser light reflected by the second half mirror 13 is reflected by the beam splitter 14 and is irradiated on the magneto-optical disk 1 via the objective lens 15.

In the present embodiment, as described above, the optical axes of the recording laser light transmitted by the second half mirror 13 and the reflected reproduction laser light are shifted from each other by the angle θ. as shown in 2, the recording laser spot S _H obtained on the magneto-optical disc 1 by the recording laser beam,
The reproducing laser spot S _M obtained on the magneto-optical disk 1 by the reproducing laser light is applied to different positions on the magneto-optical disk 1. FIG. 2 shows the diffraction grating 1
Also shown are spots S _E and S _F due to the light beam components separated at 8.

This is because the recording laser light reflected by the first half mirror 12 and the reproducing laser light reflected by the second half mirror 12 are shifted from each other by a beam splitter 14 with their optical axes shifted by an angle θ. This is because it is incident on Then, it is reflected by the beam splitter 14, albeit in the recording laser spot S _H and reproducing laser spot S _M is irradiated onto the magneto-optical disc 1 on the same track through the objective lens 15, the spot S _H is the form that preceded spot S _M.

The spots S _E and S _F are light flux component spots used for obtaining a tracking error signal.

The reproducing laser beam irradiated on the magneto-optical disk 1 is reflected by the magneto-optical disk 1 and becomes return light. The return light has its linear polarization plane rotated in accordance with the direction of magnetization in the perpendicular magnetization film formed on the recording layer of the magneto-optical disk 1. This return light is incident on the beam splitter 14 via the objective lens 15, passes through the beam splitter 14, and reaches the Wollaston prism 19.

The return light divided into three by the Wollaston prism 19 is condensed by a condenser lens 20,
Further, the light enters the photodetector 22 via the multi-lens 21.

At the time of recording, the return light via the recording laser spot _SH is transmitted through the objective lens 15
The light passes through the beam splitter 14 and enters the Wollaston prism 19.

The returned light through the recording spot S _H incident on the Wollaston prism 19, condenser lens 20
To form an image on the photodetector 22 via the multi-lens 21.

The photodetector 22 has the configuration shown in FIG. That is, the photodetector 22, a focusing error signal from the return light through the reproducing laser spot S _H, the first light receiving portion 40 for reproducing the tracking error signal and the recorded information signal, the recording laser A second light receiving section 41 for monitoring a write signal when an information signal is recorded from the return light via the spot _SH is provided on the same light receiving surface.

The first light receiving section 40 is provided with a focusing sensor 40a composed of sensor elements A, B, C, and D divided vertically and horizontally, and spaced apart on both sides of the focusing sensor 40a. It is composed of tracking error detection sensor elements E and F, and reproduction signal detection sensor elements I and J arranged above and below the focusing sensor 40a with a space therebetween.

In each of the sensor elements A to J of the first light receiving section 40 having such a configuration, the reproduction laser light divided into three by the diffraction grating 18 is supplied to the center focusing sensor 40a. The light is incident on the sensor elements E and F. The reproduction laser light divided into three by the Wollaston prism 19 is
The light is incident on the sensor elements I and J.

That is, the focusing sensor 4
0a, the detection signals of the sensor elements A to D are represented by I _{A to} I _{D, respectively.}
When focusing error signal I _{F is, I F = (I A +} I C) - a (I _B + I _D).

Further, the tracking error detection sensor is used.
The detection signals of the elements E and F are_E, I _FThen
King error signal I_TIs I_T= I_E-I_F Becomes

The reproduced signal detecting sensor elements I and J
Are detected signals I _I and I _J , the reproduced signal I _MO is I _MO = I _I -I _J.

Further, the second light receiving section 41 detects a write signal I _H when recording an information signal.

As described above, this embodiment has the recording semiconductor laser 10 for emitting light for recording and the semiconductor laser 16 for reproduction for emitting light for reproduction, respectively.
Since the laser beam for reproduction is always output and the laser beam for recording is output only at the time of recording, the high-frequency superimposing circuit conventionally required is unnecessary.

In this embodiment, since the optical axes of the recording laser beam transmitted through the second half mirror 13 and the reflected reproduction laser beam are shifted from each other by the angle θ, the recording laser beam is shifted. and the spot S _H, reproducing laser spot S _M
Is applied to different positions on the magneto-optical disk 1. Therefore, even at the time of recording, the first light receiving unit 40 and the second light receiving unit 41 disposed on the same light receiving surface of the photodetector 22 are provided with a recording laser beam and a reproducing laser beam that do not interfere with each other. Laser light is incident.

The optical laser device according to the present invention is not limited to the above-described embodiment. To shift the optical axes of the recording laser beam and the reproducing laser beam from each other, FIG. As described above, the optical axis of the writing laser light incident on the first half mirror 52 from the writing semiconductor laser 50 via the collimator lens 51 may be inclined by the angle θ with respect to the base line L. The other embodiment shown in FIG. 4 differs from the above embodiment shown in FIG. 1 in that a first half mirror 52 and a second half mirror 1 are provided.
It is arranged at an angle parallel to 3 and is adjusted
This is an arrangement position (angle) of the writing semiconductor laser 50.
The other parts of the configuration shown in FIG. 4 are the same as those in the embodiment shown in FIG.

In order to shift the optical axes of the recording laser beam and the reproducing laser beam from each other, the reproducing semiconductor laser 56 is moved in the directions of arrows X and Y as shown in FIG. Is also good. Since the other parts of the configuration shown in FIG. 5 are the same as those shown in FIG. 1 or FIG. 4, the same reference numerals are given and the description is omitted.

Further, in the embodiment shown in FIG. 1, the inclination of the first half mirror 12 is adjusted, but the angle is adjusted to the second angle.
And the inclination of the second half mirror 13 may be adjusted.

Further, in the other embodiment shown in FIG. 4, the position of the semiconductor laser 50 for writing is adjusted, but the position of the semiconductor laser 16 for reproduction may be adjusted.

[0053]

The optical head device according to the present invention has a recording laser light source and a reproduction laser light source separately, and further obtains a focusing error signal from a return light of the reproduction light reflected by the optical recording medium. Since it has a first light receiving portion for reproducing a tracking error signal and a recorded information signal and a second light receiving portion for monitoring a write signal when recording an information signal from the return light of the recording light, a conventional light receiving portion is provided. The required high frequency superposition circuit is not required.

Also, in the optical head device according to the present invention, since the optical axes of the recording laser beam and the reflected reproduction laser beam are shifted from each other, the recording laser spot and the reproduction laser spot are Light is applied to different positions on the optical recording medium. Therefore, even at the time of recording, the first and second light receiving portions disposed on the same light receiving surface of the photodetector have recording laser light and reproducing laser light that do not interfere with each other. Is incident.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining the operation of the embodiment shown in FIG. 1;

FIG. 3 is a diagram showing a sensor arrangement on a light receiving surface of a photodetector.

FIG. 4 is a schematic diagram showing a schematic configuration of another embodiment.

FIG. 5 is a schematic diagram showing a schematic configuration of another embodiment.

FIG. 6 is a diagram for explaining a high frequency superimposed current of the optical head device.

FIG. 7 is an enlarged view for explaining a high frequency superimposed current.

[Explanation of symbols]

 1 ... Magneto-optical disk 10 ... Semiconductor laser for recording 11, 17 ... Collimator lens 12 ... First half mirror 13 ... Second half mirror 14 ... Beam splitter 15 Object lens 16 Reproduction semiconductor laser 18 Diffraction grating 19 Wollaston prism 22 Photodetection vessel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI G11B 7/135 G11B 7/135 Z 7/14 7/14 (58) Investigated field (Int.Cl. ⁷ , DB name) G11B 11/105 551 G11B 7/12-7/22 G11B 7/00-7/013

Claims (5)

(57) [Claims] 1. An optical head device which is relatively movable with respect to an optical recording medium and records and / or reproduces an information signal with respect to the optical recording medium by light passing through an optical system. A recording laser light source for emitting recording light for recording an information signal on the optical recording medium; and a reproducing laser light for emitting reproduction light for reproducing the information signal recorded on the optical recording medium. A laser light source, and a focusing error signal, a tracking error signal, and a recorded information signal from return light of reproduction light emitted from the reproduction laser light source and reflected by the optical recording medium. A first light receiving portion for reproduction; and a write operation for recording an information signal from return light of recording light emitted from the recording laser light source and reflected by the optical recording medium. An optical head apparatus characterized by a second light-receiving section for monitoring signals only. 2. A recording laser spot obtained on the optical recording medium by recording light of the recording laser light source;
2. The optical head device according to claim 1, wherein a reproduction laser spot obtained on the optical recording medium by the reproduction light of the reproduction laser light source is applied to different positions of the optical recording medium. 3. The optical head device according to claim 1, wherein the first light receiving unit and the second light receiving unit are disposed on the same light receiving surface of one photodetector. . 4. The optical system according to claim 1, wherein the first mirror reflects a recording light emitted from the recording laser light source, and transmits the recording light reflected from the first mirror. A second mirror for reflecting reproduction light emitted from the reproduction laser light source; a recording light transmitted by the second mirror; and a second mirror.
A beam splitter that reflects the reproduction light reflected by the mirror together and irradiates the optical recording medium with the reflected light, and transmits return light from the optical recording medium. The optical head device according to claim 1. 5. The optical system according to claim 1, wherein the optical axes of the recording light reflected by the first mirror and the reproducing light reflected by the second mirror are shifted from each other. The optical head device according to claim 4.