JPH03171452A - Magnetooptic recording medium driving device and rewriting system for magnetooptic recording medium - Google Patents

Abstract

PURPOSE:To rewrite information fast by using one laser light source and one laser beam by scanning with an irradiation laser beam while deflecting the laser beam by a fine angle along a recording track of the magnetooptic recording medium. CONSTITUTION:Optical deflectors 3 and 13 which deflect the laser beam to irradiate the magnetooptic recording medium 1 from an objective 3 by a fine angle along the recording track 31 of the magnetooptic recording medium 1 are interposed in the optical path 4 extending from a laser light source 8 to the objective 3. Consequently, a laser beam 32 for erasure is deflected in the travel direction of the recording track after a position where a new signal is to be rewritten is detected to erase information which is already recorded in a fine area, and a laser spot 33 is returned to the head of the area where the information is erased to irradiate the erased area with a laser beam 32 for recording which is modulated with a necessary information signal, thereby rewriting the information. Thus, an information signal is overwritten artificially with one light source and one light beam and the information rewriting time is shortened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording medium drive device that records and reproduces information using a magneto-optical recording medium as a recording medium, and a magneto-optical recording medium instantaneous device. This paper relates to a rewriting method for the magneto-optical recording medium used.

[Prior art]

The so-called magnetic field modulation method and the optical modulation method have been proposed as recording methods for magneto-optical recording media, which are attracting attention as recording media that allow information to be erased and rewritten (
Japan Ogawa Magnetics Society Journal, V o ]. ．． 8, No. 5,
1984. Shutake Imamura “Current status of magneto-optical disk memory”)
.

In the magnetic field modulation method, as shown in FIG.
are arranged opposite to each other, and a laser beam 34 of a constant intensity is continuously irradiated from an optical head 32 along the recording track of the recording layer 31a to sequentially heat the irradiated portion of the laser beam 34 to the vicinity of the Curie point.

By applying a magnetic signal 35 modulated by a predetermined information signal from the electromagnetic coil 33 to the irradiated portion of the laser beam 34, the magnetization direction of the recording layer 31a is appropriately reversed.
Information signals are recorded in correspondence with the direction of magnetization.

On the other hand, in the optical modulation method, as shown in FIG.
A laser beam 3 modulated by a predetermined information signal from
4 and reverse the magnetization of the portion of the recording layer 31a irradiated with the laser beam 34, thereby recording an information signal in correspondence with the direction of magnetization.

[Problem to be solved by the invention]

The above-described magnetic field modulation method is similar in principle to the recording method for magnetic recording media, and can overwrite new information in an area where information has already been recorded. However, if the magnetic field is generated using a simple electromagnetic coil 33, a considerable amount of driving power is required to generate the magnetic field required for recording, so when considering the allowable size and power consumption of the driving device, It is difficult to increase the recording frequency, and the current limit is about 100 KHz.

On the other hand, when using an optical modulation method, high-speed modulation on the order of IMHz is possible, but on the other hand, there is a problem in that information cannot be overwritten. For this reason, conventionally, when writing a new signal to an already recorded area, when an area where the new signal should be rewritten is detected, an erasing laser beam is irradiated to erase the previously recorded information in the area. Furthermore, a rewriting method is adopted in which the reproducing laser beam detects the writing area again and then irradiates the recording laser beam onto the area. According to such a rewriting method, for example, when a magneto-optical recording medium is used, the disk must be rotated at least twice from when a new signal is detected to be rewritten to when writing is completed. However, there is a problem that rewriting information is slow.

In addition, as a means to enable pseudo overwriting in the light modulation method, a method of preparing two or more light sources has also been proposed (J. Braat: private
communication (1984)
), however, there is a problem that the driving device becomes expensive and large due to the increase in the number of light sources and the complexity of the optical path, and is not practical.

The present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional technology, and is a magneto-optical recording medium in which information can be rewritten at high speed using one laser light source and one laser beam. The object of the present invention is to provide a drive device and a rewriting method for a magneto-optical recording medium.

[Means to solve the problem]

In order to achieve the above object, the present invention has a laser beam irradiated onto a magneto-optical recording medium from the objective lens, on an optical path from a laser light source to an objective lens, in a minute direction along the recording track of the magneto-optical recording medium. It is characterized by the provision of an optical deflector that scans by swinging the angle, for example, a sound-pull optical deflector.

In addition, when accessing the unoccupied area where new information is rewritten by irradiating the reproduction laser beam along the recording trunk, a /l'1 demagnetizing field is generated in the electromagnetic coil and erased from the laser light source. irradiate the laser beam for
Deleting the previously recorded information written in the irradiation area of the erasing laser beam by deflecting the erasing laser beam at a minute angle along the traveling direction of the recording track,
Next, the output of the laser light source is reduced to zero, and the laser spot is returned to the beginning of the area where the information has been erased as described above.
Next, the desired rewriting is performed by repeating the operation of generating a recording magnetic field in the electromagnetic coil and irradiating a recording laser beam corresponding to the desired information signal from the laser light source to record information in the previously erased area. This is characterized in that a new information signal is rewritten in the area.

[Effect]

The magneto-optical recording medium drive device and rewriting method of the present invention rank a laser beam irradiated from the objective lens to the magneto-optical recording medium to recording 1 on the optical path from the laser light source to the objective lens. An optical deflector that deflects at a minute angle along the track is installed, so after detecting the position where a new signal should be rewritten, the erasing laser beam is deflected in the direction of travel of the recording track to erase the previously recorded information in the minute area. The information can be rewritten by erasing the area, then returning the laser spot I to the beginning of the erased area and irradiating the erased area with a recording laser beam modulated by the required information signal. . In this way, by repeating erasing and writing for each micro area, 1
It is possible to perform pseudo overwriting using two laser light sources and two laser beams.

〔Example〕

An embodiment of the magneto-optical recording medium driving apparatus according to the present invention will be described below. FIG. magnetic recording medium, 2
3 is an electromagnetic coil, 3 is an objective lens disposed opposite to the electromagnetic coil 2 via the magneto-optical recording medium 1, and 4 is an l-th lens.
5 is the second optical path, 6 is the third optical path, and 7 is the fourth optical path.

The first optical path 4 includes a laser light source 8, a collimator lens 9, a beam 1=I anti-shape prism 10, a first polarizing prism II, an anti-filter 2, and an optical deflector, such as an acousto-optic deflector 13. and the objective lens 3.

The second optical path 5 includes the objective lens 3, the acousto-optic deflector 13, the reflecting mirror 12, the first polarizing prism 11, the second polarizing prism l114, and one-half
A wavelength plate l5, a polarizing beam l1 splitter 16, a second reflecting mirror 17, a first lens 18 placed behind the polarizing beam splitter 16, and a second reflecting mirror J7 placed behind the polarizing beam splitter 16. a second lens 19; -" two photodetectors 1w2Or2 disposed behind the first lens 18 and second lens 19; and the two photodetectors 20, 21. It consists of a differential amplifier 22 that detects an output difference.

The third optical path 6 includes the objective lens 3, the acousto-optic deflector 13, the first reflecting mirror 12, the first polarizing prism 11, and the second Tsukuda! an optical prism 14, a beam splitter 23, a third lens 2/l, and a
- a racking photodetector 25;

The fourth optical path 7 includes the objective lens 3, the acousto-optic deflector 13, the first reflecting mirror 12, the first polarizing prism 11, and the second polarizing prism l4,
It is composed of the beam splitter 23, a fourth lens 26, a cylindrical lens 27, and a focusing photodetector 28.

Although detailed illustrations are omitted, the magneto-optical recording medium 1 is pre-formed with guide grooves for tracking and pre-pits for addressing. A recording layer is formed.

The electromagnetic coil 2 can appropriately apply a magnetic field in the recording direction and a magnetic field in the erasing direction to the recording layer of the magneto-optical recording medium 1 by controlling the direction of the supplied current.

By controlling the output, the laser light source 8 can appropriately irradiate a low-power reproduction laser beam, a high-power erasing laser beam, and a pulsed recording laser beam corresponding to a required information signal. ing. The laser beam t1 illuminated from this laser light source 8 is made into a parallel beam by a collimator lens 9, further shaped by a beam shaping prism 10, and then passed through a first polarizing prism l1, a first reflecting mirror 12, an acousto-optic The recording layer of the magneto-optical recording medium 1 is irradiated with the light through the deflector 13 and the objective lens 3.

The acousto-optic deflector 13 is set to be able to deflect the laser beam from the laser light source 8 by an appropriate minute angle along the recording track of the magneto-optical recording medium 1 by controlling an input signal. be done.

The entire laser beam reflected from the recording layer of the magneto-optical recording medium 1 returns to the objective lens 3 and reaches the polarizing beam splitter 16 via the second optical path 5.

The reflected light from the magneto-optical recording medium 1 is split into two parts by this polarizing beam splitter 16, and is incident on a first photodetector 20 and a second photodetector 21.

Then, by detecting the difference in the amount of light received (output) by these two photodetectors 20 and 21 with the differential amplifier 22,
Information recorded in the pre-formed blipits or recording layer of the magneto-optical recording medium 1 is read out.

Further, the reflected light returning from the recording layer of the magneto-optical recording medium 1 to the objective lens 3 is incident on the tracking photodetector 25 via the third optical path 6, and the tracking photodetector 25
A track servo (not shown) is operated based on the output. As a result, the guide groove of the magneto-optical recording medium 1 is constantly irradiated with a laser spot.

Further, the reflected light returning from the recording layer of the magneto-optical recording medium 1 to the objective lens 3 is incident on the focusing photodetector 28 via the fourth optical path 7.
Based on the output of 8, a focus servo (not shown) -11- is activated. As a result, the laser beam is always focused on the recording layer of the magneto-optical recording medium 1. Note that the cylindrical lens 27 is set to detect the direction of focus shift.

Hereinafter, the recording, reproducing, and rewriting methods of the magneto-optical recording medium drive device will be explained based on FIGS. 2 and 3.

When writing a new information message 41j in an area where information has already been recorded, first, without exciting the electromagnetic coil 2, a low-power reproduction light beam is sent from the objective lens 3 to the magneto-optical message. Irradiate along the recording track of the medium l. The difference in the outputs of the photodetectors 20 and 21 that received the reflected light from the recording layer of the magneto-optical recording medium 1 is detected by the differential amplifier 22.
By detecting this, the address information of the blip-pits formed in the magneto-optical recording medium l is read out, and a control device (not shown) determines whether or not the playback area is a recording area for new information that is required. Ru.

When a recording area in which new information is to be recorded is read out, current is immediately supplied to the electromagnetic coil 2 based on a command from a control device (not shown), and the existing information is stored in the magneto-optical recording medium 1. A magnetic field of the magnitude and direction necessary to erase information is applied, and the output of the laser light source 8 is powered up to a level that can heat the laser beam irradiated part of the recording layer to near the Curie point (see Fig. 2). T1~T
2). At the same time, a signal is applied to the acousto-optic polarizer 13, and as shown in FIG. The recorded information in the area to which the ablation laser spot 33 has been moved is erased.

Next, based on a command from a control device (not shown), the 3M electric current to the electromagnetic coil 2 is cut off, and the output of the laser light source 8 is made zero (T z '' T ,a in FIG. 2).

At the same time, a signal in the opposite direction is applied to the acousto-optic polarizer l3, and as shown in FIG. Adjust the incident angle of the laser beam.

Next, a current in the opposite direction is supplied to the electromagnetic coil 2 based on a command from a control device (not shown), and a magnetic field of a magnitude and direction necessary for recording new information on the magneto-optical recording medium l is applied. At the same time, the laser light source 8 emits a laser beam having a waveform corresponding to a desired information signal (T3 to T4 in FIG. 2). At the same time, a signal is applied to the upper acousto-optic polarizer 13, and as shown in FIG.
5 is deflected by a minute angle of 0, and the recording laser spot l-3/l is moved from the beginning of the user information recording area! A new 117th report will be AXed 11 times.
In FIG. 3, the magneto-optical recording medium 1 is not rotationally driven. However, by matching the rotational speed of the magneto-optical recording medium 1 and the deflection angle θ of the laser beam, magneto-optical recording can be performed. Even when the medium l is rotationally driven, recording can be continued in the same area in the same manner as described above. In this case, the angular velocity is constant (CAV
), the deflection angle 0 of the laser beam deflected along the record 9 track 15 31 is gradually increased from the inner circumference to the outer circumference of the recording area. It is preferable to adjust the acousto-optic deflector 13 so that the deflection angle O of the laser beam is 0.6 degrees at a position at a radius of 25 nm from the rotation center of the magneto-optical recording medium 1. At a position 60 mrn in radius from the center of rotation, the deflection angle θ of the laser beam is 1.2 degrees. Of course, magneto-optical δ where information is recorded at constant linear velocity (CLV)
Regarding the self-recording medium 1, the acousto-optic deflector 13 is set so that the deflection angle 0 of the laser beam l1 deflected along the racks 1 to 31 is -. is adjusted.

Thereafter, by repeating erasing and recording for each small area as described above, a new information signal is rewritten in the entire required area.

When reading information from the magneto-optical recording medium 1 on which information has already been recorded, it is exactly the same as the conventional method, and the reproducing light beam is sent from the objective lens 3 to the magneto-optical recording medium 1 without exciting the electromagnetic coil 2. Recording-16: irradiate along the track, guide the reflected light from the magneto-optical recording medium 1 through the objective lens 3 to the second optical path, and use the differential amplifier 22 to detect the two photodetectors 20, 2]
This is done by detecting the output difference between the two. Of course, in this case as well, the tracking of the reproduction light beam is maintained by the 1-racking photodetector 25, and the tracking of the reproduction light beam is maintained by the focusing photodetector 28.
Focusing is performed.

Furthermore, when erasing information from the magneto-optical recording medium 1 in qt, it is exactly the same as the conventional method, in which an erasing magnetic field is generated in the electromagnetic coil 2, and an erasing laser beam irradiated from the laser light source is applied to the magneto-optical recording medium 1. This is done by scanning along the recording trunk of the .

In this case as well, the 1-racking photodetector 25 maintains tracking of the reproduction light beam, and the focusing photodetector 28 focuses the reproduction light beam spot.

The magneto-optical recording medium drive device of the present invention includes a first optical system that irradiates a laser beam from a laser light source 8 to the magneto-optical recording medium J through the objective lens 3, and a laser beam from the objective lens 3 to the magneto-optical recording medium J. Since an acousto-optic deflector 13 is provided to deflect the laser beam irradiated onto the magneto-optic recording medium 1 by a minute angle along the recording track of the magneto-optical recording medium 1, erasing and rewriting b can be performed by the acousto-optic deflector 13 and By appropriately controlling the electromagnetic coil 2 and the laser light source 8, it is possible to repeat the process by small angles. Therefore, pseudo overwriting can be performed using one laser light source and one laser beam.

According to experiments, when information is rewritten under the above conditions for the magneto-optical recording medium 1 on which information is recorded at a constant angular velocity (CA.V), the racking shift toward 1 is approximately 2.
It was found that the thickness was about 0 nm, and there was no problem in practical use. In addition, when the information rewritten as described in -1= was reproduced, the C/N ratio was 45 dB (bandwidth 30 KHz) at a carrier frequency of 2 MHz, and the characteristics were sufficient for practical use. I found out something.

Incidentally, the gist of the present invention is a magneto-optical recording medium drive! In an FII device, on the optical path that guides the laser beam from the laser light source to the objective lens, there is a light beam that deflects the laser beam irradiated from the objective lens onto the magneto-optical recording medium by a minute angle along the recording track of the magneto-optical recording medium. The point is that a deflector is provided, and the specific optical circuit is not limited to that shown in the above embodiment.

〔Effect of the invention〕

As explained above, according to the magneto-optical recording medium storage device of the present invention, it is possible to pseudo-overwrite information signals with one light source and one light beam. It is possible to shorten the time required to rewrite information without causing data to change.

[Brief explanation of the drawing]

Fig. 1 is an optical circuit diagram showing an example of the optical system of the magneto-optical recording medium drive device according to the present invention, and Fig. 2 shows an electromagnetic coil for overwriting new information in an area where information has already been recorded. A timing chart showing the operation of the light source, Figure 3 is an explanatory diagram explaining the operation of the optical slot when new information is overwritten on an area where information has already been recorded, and Figure 4 shows the principle of the magnetic modulation method. FIG. 5 is a front view showing the principle of the optical modulation method. 1: magneto-optical recording medium, 2: electromagnetic coil, 3: objective lens, 4: first optical path, 5: second optical path, 6: third optical path,
7: Fourth optical path, 8: Light source, 9: Collimator lens, l
O: Beam-shaped prism l1, 11: Polarizing prism, 12
: reflecting mirror, 13: acousto-optic deflector, l4: second polarizing prism, 15: half-wave plate, 16: polarizing beam splitter, 17: second reflecting mirror, 18: l-th lens, I
9: Second lens, 20, 21: Photodetector, 22: Differential amplifier, 23: Beam splitter, 24: Third lens, 25: Tracking photodetector, 26: Fourth lens, 27 : Cylindrical lens, 28: Photodetector for focusing

Claims (4)

[Claims] (1) A first optical system comprising an objective lens and an electromagnetic coil arranged opposite to each other via a magneto-optical recording medium, and guiding a laser beam from a laser light source to at least the objective lens, and the magneto-optical recording medium. and a second optical system that reads information signals by detecting reflected light from the objective lens, the magneto-optical recording medium is irradiated from the objective lens onto the magneto-optical recording medium by the first optical system. laser beam,
A magneto-optical recording medium driving device characterized in that an optical deflector is provided for scanning along a recording track of the magneto-optical recording medium by swinging it at a minute angle. (2) In the magneto-optical recording medium drive device according to claim 1, the deflection angle of the laser beam deflected along the recording track of the magneto-optical recording medium ranges from the inner circumference to the outer circumference of the recording area. What is claimed is: 1. A magneto-optical recording medium drive device comprising: an optical deflector that is adjusted to increase in size in accordance with the following. (3) In the magneto-optical recording medium drive device according to claim 1, the deflection angle of the laser beam deflected along the recording track of the magneto-optical recording medium is different from the inner circumference and the outer circumference of the recording area. 1. A magneto-optical recording medium drive device comprising an optical deflector that is adjusted to be constant regardless of the angle of the beam. (4) The area where new information is to be rewritten is accessed by irradiating a reproduction laser beam along the recording track, and when address information in the desired area is detected, an erasing magnetic field is applied to the electromagnetic coil. At the same time, an erasing laser beam is emitted from a laser light source, and the erasing laser beam is deflected by a small angle along the traveling direction of the recording track. The recorded information is erased, and then the output of the laser light source is reduced to zero, and the laser spot is returned to the beginning of the area where the information was erased as described above. Next, a recording magnetic field is generated in the electromagnetic coil, and the required amount is emitted from the laser light source. By repeating the operation of irradiating a recording laser beam corresponding to the information signal and recording information in the previously erased area, a new information signal is rewritten in the required rewriting area. A rewriting method for magneto-optical recording media characterized by the following.