JP2848576B2 - Magneto-optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus of a magnetic field modulation type, and more particularly to a magneto-optical recording / reproducing apparatus for simultaneously recording on a plurality of information tracks using a plurality of light spots.

[0002]

2. Description of the Related Art In recent years, a magneto-optical disk device using a magneto-optical disk as a recording medium has a large storage capacity,
Expectations are high because erasure and rewriting are possible. In order to further improve the performance, research on overwriting to increase the data transfer rate and research on increasing the storage capacity are active.

[0003] As the overwriting method, a magnetic field modulation method and an optical modulation method are known roughly. The magnetic field modulation method is a method of applying a bias magnetic field modulated according to recording information while irradiating a recording medium with a laser beam having a constant intensity. On the other hand, the light modulation method is a method of irradiating a laser beam modulated according to recording information while applying a constant magnetic field to a recording medium.

Recently, there has been proposed a method of performing overwriting by irradiating a laser beam in a pulse shape while applying an AC magnetic field of a constant frequency to a recording medium. 6A and 6B are time charts for explaining a recording operation of the recording method. FIG. 6A shows a reference clock, FIG. 6B shows an AC magnetic field, and FIG. 6C shows a pulsed laser beam. In this recording method, an AC magnetic field synchronized with a reference clock is applied to a recording medium, and a laser beam is irradiated in synchronization with positive and negative peak positions of the AC magnetic field. In this case, the laser beam is emitted at the positive peak point or the negative peak point of the AC magnetic field based on a signal obtained by modulating the recording signal shown in FIG. As described above, the magnetization direction of the temperature rising portion of the recording medium is oriented in the direction corresponding to the recording signal, and a magnetic domain is formed as shown in FIG. The shape of the magnetic domain formed at this time is shown in FIG.
As shown in FIG.

[0005]

However, in the conventional magnetic field modulation method performed while irradiating a laser beam of a constant intensity as described in the prior art, Japanese Patent Laid-Open No. 2-179948 discloses that simultaneous recording is performed on a plurality of tracks by a plurality of spots. Can be performed only in a time-sharing manner, as described in. Further, in the light modulation system, although simultaneous recording by a plurality of spots can be basically performed, the control of the semiconductor laser by the light modulation system itself is complicated. Therefore, when the number of light spots is plural, control becomes further complicated, and in addition, a disk for light modulation is expensive, which is not practical.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a magneto-optical recording / reproducing apparatus capable of simultaneously recording a plurality of tracks by a plurality of spots while using a magnetic field modulation method. Is to do.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magneto-optical device.
Information is simultaneously recorded on multiple information tracks on a recording medium, or
Magneto-optical recording / reproducing device that reproduces multiple information tracks simultaneously
In the arrangement, a plurality of light sources, emitted from the plurality of light sources
Light beam on a plurality of information tracks of the recording medium
Means for irradiating each as a light spot, and
Applying an AC magnetic field of a predetermined frequency to multiple information tracks
Means, and means for pulse driving the plurality of light sources.
A set for simultaneously recording or reproducing the recording medium
Information in one of the information tracks
A timing pit indicating the head position of the information recordable area is recorded.
If the timing pit is detected,
An AC magnetic field is applied to the recording medium from the AC magnetic field applying means.
The driving means controls each of the plurality of light sources with an AC magnetic field.
Synchronous to the peak of either the positive or negative polarity of the field.
The pair of information tracks by pulse driving
And , following the erasure, the recording medium
While applying an AC magnetic field from the AC magnetic field applying means,
A signal to be recorded by each of the plurality of light sources by the driving means.
In synchronization with the peak of the positive or negative polarity of the AC magnetic field, depending on
By pulse driving, the one set of information tracks
This is achieved by a magneto-optical recording / reproducing apparatus characterized in that recording is performed simultaneously .

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the magneto-optical recording / reproducing apparatus of the present invention.

In FIG. 1, reference numeral 1 denotes three semiconductor lasers 1.
a, 1b, and 1c are laser light sources manufactured by hybrid or monolithic. The three laser beams emitted from the laser light source 1 are collimated by a collimator lens 2 and then corrected by a beam shaping prism 3 into a light beam having a circular cross section. Then, the light passes through the polarization beam splitter 4 and is condensed by the objective lens 5 to form three light spots on the magnetic layer of the magneto-optical disk 6 which is an information recording medium. As the magneto-optical disk 6, a recording medium for modulating a magnetic field such as one having a single magnetic layer or a two-layer structure utilizing exchange coupling force is used. The magneto-optical disk 6 is rotated at a predetermined speed by driving a spindle motor (not shown). Reference numeral 7 denotes a magnetic head provided opposite to the objective lens 5 with the magneto-optical disk 6 interposed therebetween. The magnetic head 7 generates an AC magnetic field having a constant frequency in synchronization with the reference clock generated by the reference clock generating circuit 8 by driving the magnetic head driving circuit 9, and applies the AC magnetic field to the magneto-optical disk 6.

FIG. 2 is a view showing a light beam condensed on the magneto-optical disk 6.
FIG. 3 is a diagram showing two light spots and a magnetic field applied to a magnetic head 7. The three light spots from the laser light source 1 irradiate adjacent information tracks as indicated by OS1, OS2 and OS3 in FIG. In this case, the width of the information track and the diameter of each light spot are about 1 μm, and the interval x between each light spot is about several tens μm to about 100 μm. A circle 27 indicated by a broken line is a range of the effective magnetic field strength of the magnetic head 7. This range should basically include three light spots, but in consideration of the control performance of the magnetic head 7,
The diameter of the range of the effective magnetic field strength is desirably about several hundred μm.

Reference numeral 10 denotes a polarizing beam splitter for dividing the reflected light from the magneto-optical disk 6 into a control optical system and a reproduction optical system. The laser beam emitted from the laser light source 1 is reflected by the magneto-optical disk 6, passes through the objective lens 5 again, enters the polarization beam splitter 4, where it is reflected by the polarization beam splitter 10. The polarization beam splitter 10 transmits or reflects the incident light, and the transmitted light flux 11 is guided to a control optical system (not shown). The control optical system uses the transmitted light beam 11 to generate an error signal for auto-tracking and auto-focusing of the optical head and outputs it to an auto-tracking and auto-focusing control circuit (not shown). This error signal is detected by, for example, a well-known push-pull method or knife-edge method. In this case, tracking and focusing error signals are separately detected for the three light spots,
The tracking and focusing control of the optical head may be performed using the respective average values. Also, typically, each error signal may be detected only for one light spot, and tracking and focusing control of the optical head may be performed using the error signal.

On the other hand, the laser beam reflected by the polarization beam splitter 10 is guided to a reproduction optical system. First, the incident light is rotated by 45 degrees in the polarization direction by the half-wave plate 12, then condensed by the condenser lens 13, and is incident on the polarization beam splitter 14. The polarization beam splitter 14 transmits or reflects the incident light, and the reflected light is detected by the photodetectors 15a, 15b, and 15c respectively corresponding to the three light spots. Further, the transmitted light of the polarization beam splitter 14 is detected by the photodetectors 16a, 16b, and 16c respectively corresponding to the three light spots as described above. The detection signals of the photodetectors 15a and 16a are output from a difference signal processor 17a.
a to generate a magneto-optical signal by taking the difference between the two. The photodetectors 15a and 16a correspond to the above-described light spot OS1, and respectively detect the reflected light. The outputs of the photodetectors 15b and 16b are sent to a difference signal processor 17b.
Outputs of the photodetectors 15c and 16c are output to a difference signal processor 17c, and each difference signal processor generates a magneto-optical signal. The light detectors 15b and 16b are connected to the light spot OS.
2 and the photodetectors 15c and 16c
Corresponds to 3. The magneto-optical signals of the difference signal processors 17a to 17c are output to a reproduction signal detection circuit 18, where they are demodulated,
The reproduction signal 19 is generated by performing the synthesizing process.

The outputs of the photodetectors 15a and 16a are output to a sum signal processor 20a to generate a light amount change signal of the light spot. The outputs of the photodetectors 15b and 16b and the outputs of 15c and 16c are also output to the sum signal processors 20b and 20c, respectively, to generate light amount change signals of the corresponding light spots. The light amount change signal of each sum signal processor is sent to a pre-pit detection circuit 21, where the pre-pit information recorded on each information track is detected, and a signal 2 indicating a track number is detected.
2 and a timing pit detection signal 23 are output.

A recording signal modulation circuit 25 separates and modulates the recording signal 24 into three signals. In the present embodiment, image information is recorded as recording information, and the image information here is ternary color R (red), G (green),
B (blue), each of which has a gradation of 8 bits. That is, it is assumed that the R, G, and B signals of the recording signal 24 are repeatedly transmitted in time series for each pixel.
The recording signal modulation circuit 25 divides the recording signal 24 into three groups. For example, a group of a, a group of b, and a group of c may be divided in order of 1 bit, but here, R, G, and B are divided into 8 bits, R is a group of a, and G is a group of b. , B as a group of c. The recording signal modulation circuit 25 modulates each group into a signal corresponding to a recording pattern on the magneto-optical disk 6. The modulation signal of the group a is output to the laser driving circuit 26a, the modulation signal of the group b is output to the laser driving circuit 26b, and the modulation signal of the group c is output to the laser driving circuit 26c. In each laser drive circuit, the corresponding semiconductor laser is pulse-lit according to the transmitted modulation signal, and information is recorded on the information track in combination with the application of the AC magnetic field.

Next, a specific operation of this embodiment will be described in detail with reference to a time chart shown in FIG. First, a recording operation will be described. FIG. 3A shows a reference clock generated by the reference clock generating circuit 8, and FIG. 3B shows an AC magnetic field generated by the magnetic head 7. The reference clock is output to the magnetic head drive circuit 7, which generates an AC magnetic field having a constant frequency synchronized with the reference clock and applies the AC magnetic field to the magneto-optical disk 6. The reference clock is a pre-pit detection circuit 21, a reproduction signal detection circuit 18, a recording signal modulation circuit 25.
Is also output to

On the other hand, the optical head is accessed by a moving mechanism (not shown) so that three light spots are located on the designated information track. In this case, the target information track is moved while the track number is detected by the pre-pit detection circuit 21. However, since recording and reproduction are performed simultaneously with three light spots, the information track 3 is used in this embodiment.
The same track number is assigned to each book. As a result, the number of track numbers to be detected can be reduced, and the circuit configuration can be simplified accordingly. Also, the track number is not always detected for the three light spots. For example, in the case of coarse movement, the track number is detected only for the center light spot, and the center light spot is used for the target three information tracks. After arriving at any one of the information tracks, the track numbers of the three light spots may be respectively detected, and the control may be switched to the precision control so that each light spot is drawn onto the target information track. By performing such control, the light spot can be moved onto the target information track at a higher speed.

When each of the three light spots is located on the target information track, the timing pit detection signal 23 in the prepits detected by the prepit detection circuit 21 is output.
Thus, it is recognized that the light spot has reached the recording area on the information track. FIG. 3C shows the timing pit detection signal. The timing pits may be recorded on all information tracks, and the timing pits of each information track may be detected by three light spots. In this case, information recording may be started for each information track. Alternatively, a timing pit may be recorded only in the center information track, and the detection signal of the pit may be used to detect that three light spots have reached the recording area. In this case, recording of information is started simultaneously for all three information tracks.

FIG. 4 shows a state in which timing pits are recorded on each information track.
1, TP2 and TP3 are recorded at the same distance as the interval x between the light spots. In this case, if the timing pits are recorded in a state where they are arranged in the radial direction of the disk, the recording and reproduction timings are shifted for each light spot. Therefore, in order to correct this shift, the capacity of the buffer memory in the recording signal modulation circuit 25 and the reproduction signal detection circuit 18 increases. Therefore, by arranging the timing pits in parallel with the arrangement of the light spots OS1, OS2, and OS3 as shown in FIG. 4, the start timing of recording and reproduction of the three light spots does not shift. . FIG. 5 shows an example in which timing pits are detected only by the central light spot, and shows an example of a sample servo format in which all prepits are recorded only on the central information track. In the figure, 29 and 30 are pairs of tracking pits, and 31 is a timing pit.

Returning now to FIG. FIG. 5C shows the timing pit detection signal as described above. In this embodiment, the timing pit is detected by the central light spot as shown in FIG. At the time of detecting a pre-pit, a laser beam having a constant power is emitted from the laser light source 1. When a timing pit is detected, each light spot is erased for the first few pulses in order to eliminate unerased portions, and thereafter, a start pit (domain) is recorded, and then recording is performed according to the modulated signal. Specifically, first, an information track
When recording information pits in the
Pits are not always recorded by
The timing of the information pit is shifted due to time axis fluctuation
I will. In particular, the pits are recorded at the earliest timing.
After that, record the pit at the latest timing
In the writing part after detecting the timing pit
Erasures occur. The cause of jitter is
Laser noise, circuit noise, noise due to media defects, etc.
There are various causes. The time axis fluctuation due to such jitter
When it occurs, write after detecting the timing pit
When the pits are left unerased at the point where they are played back
May not play correctly. Therefore, in this embodiment,
Erases several pulses after detecting a timing pit
This is done to prevent the writing part from being erased. The book
After the starting part, the remaining part disappears due to overwriting
do not do.

FIG. 3D-1 shows a laser pulse of the semiconductor laser 1a driven by the laser drive circuit 26a. The semiconductor laser 1a forms an image of the light spot OS1 on the information track, and is driven according to the modulation of the recording signal modulation circuit 25. FIG. 2D shows a laser pulse of the semiconductor laser 1b corresponding to the light spot OS2, and FIG. 2D shows a laser pulse of the semiconductor laser 1c corresponding to the light spot OS3. These laser pulses are similarly driven according to the modulation of the recording signal modulation circuit 25.

In each laser pulse, the first two pulses are erasing pulses, and the AC magnetic field is applied at a negative polarity peak position. As a result, the direction of magnetization of the laser pulse irradiated portion of each information track becomes downward, and if there is any unerased previous recorded information, they are completely erased and the magnetization direction is returned to the initial state. In this embodiment, a downward magnetization direction is set as an initial state. FIG. 3E-1 shows a recording pattern on an information track corresponding to a laser pulse of the semiconductor laser 1a. FIG. 2E shows a recording pattern corresponding to the semiconductor laser 1b, and FIG. 3E shows a recording pattern corresponding to the semiconductor laser 1c. In this recording pattern,
The white area indicates the downward magnetic domain in the magnetization direction, and the shaded area indicates the upward magnetic domain in the magnetization direction. In the area where the two laser pulses for erasing have been irradiated, the magnetization direction is downward as described above, and it can be seen that the area is initialized.

In each laser pulse, the third pulse records a start pit indicating a start position of information recording. Since the start pit is recorded by the modulation signal “1” as shown in each laser pulse, the start pit laser pulse is emitted in synchronization with the positive polarity peak position of the AC magnetic field. As a result, upward magnetic domains are respectively formed on the three information tracks, and the upward magnetic domains are recorded only after the timing pit is detected. Thereafter, following the laser pulse for the start pit, the information tracks shown in FIGS.
2) and laser pulses shown in (d-3) are applied. These laser pulses convert the image information into R,
The signals separated for each of the G and B pixels are modulated, and are radiated in parallel on three information tracks. For example, in the laser pulse shown in FIG. 3 (d-1), after the third start pit laser pulse is irradiated, the timing is adjusted to the positive peak point of the AC magnetic field until just before the next modulation signal "1". Are irradiated with two laser pulses. Next, the modulation signal becomes “1”, and four laser pulses are emitted at the timing of the negative peak point of the AC magnetic field until just before the next modulation signal “1”. That is, the laser pulse is irradiated with the timing adjusted to the positive or negative polarity of the AC magnetic field in accordance with the magnetic domain to be recorded, and the magnetization direction is reversed when the modulation signal is "1". As a result, as shown in FIG. 3 (e-1), initially, upward magnetic domains indicated by oblique lines are recorded, and then magnetic domains are sequentially recorded in accordance with the modulation signal, such as downward magnetic domains and upward magnetic domains. Also, with the laser pulses shown in FIGS. 3 (d-2) and (d-3), magnetic domain recording is performed in exactly the same manner as described above, and FIG.
2), magnetic domains as shown in (e-3) are recorded.

As described above, in this embodiment, since the data of each pixel of the image information can be recorded in parallel on each information track, the data transfer speed can be greatly increased. In addition, since simultaneous recording on a plurality of tracks is effectively performed while using the magnetic field modulation method, an inexpensive magnetic field modulation disk can be used, and control of the semiconductor laser is not complicated as in the light modulation method. It can be done relatively easily.

On the other hand, when reproducing the information recorded on the magneto-optical disk 6, first, the optical power of each semiconductor laser of the laser light source 1 is set to a constant intensity reproduction power. Then, as in the case of recording, the three light spots are moved on the target information track, and each information spot is scanned on each information track at the same time. In this case, the head position of the recorded magnetic domain sequence is recognized based on the above-described timing pit detection signal, and thereafter, the reproduction signal detection circuit 18 reproduces the recording information based on the outputs of the difference signal processors 17a to 17c. That is, in the reproduction signal detection circuit 18, the difference signal processor 1
The magneto-optical signal for each information track generated in each of 7a to 17c is taken in and sequentially demodulated and synthesized. As a result, the information recorded separately for each of the R, G, and B pixels on the three information tracks is restored to the original image information again.
It is output as a reproduction signal 19.

In the above embodiment, image information is taken as an example of recording information, and separated data for each of R, G, and B pixels is recorded on three information tracks using three semiconductor lasers. However, the present invention is not limited to this. For example, recording information other than image information can be recorded. In this case, the number of information tracks to be recorded simultaneously is not limited to three, and can be arbitrarily set to less or more.

[0026]

According to the present invention as described above, according to the present invention, magnetic
Simultaneous recording on multiple tracks by field modulation
With a simple configuration and the use of inexpensive recording media.
Transfer data while enjoying the benefits of magnetic field modulation
Speed can be greatly increased. At the same time,
Is one of a set of information tracks to be played
Because the timing pit is recorded in the
The amount can be reduced and signal processing can be performed easily.
Wear. Furthermore, when a timing pit is detected, the first few
Since Lus erased and started recording afterwards,
In the writing part after detecting the timing pit
It is possible to completely prevent the occurrence of unerased parts .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a magneto-optical recording / reproducing apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a light spot on an information track and an effective magnetic field strength range of an AC magnetic field.

FIG. 3 is a time chart showing an information recording operation of the embodiment of FIG.

FIG. 4 is an explanatory diagram showing a positional relationship between a light spot and a timing pit when a timing pit is recorded on all information tracks.

FIG. 5 is an explanatory diagram showing timing pits, tracking pits, and light spots when a timing pit is typically recorded on one information track of a set of information tracks.

FIG. 6 is a time chart showing an information recording operation of a conventional magneto-optical recording / reproducing apparatus.

[Explanation of symbols]

 Reference Signs List 1 laser light source 1a, 1b, 1c semiconductor laser 5 objective lens 6 magneto-optical disk 7 magnetic head 8 reference clock generation circuit 9 magnetic head drive circuit 15a, 15b, 15c photodetector 16a, 16b, 16c photodetector 17a, 17b, 17c Difference signal processor 18 Reproduction signal detection circuit 20a, 20b, 20c Sum signal processor 21 Prepit detection circuit 25 Recording signal modulation circuit 26a, 26b, 26c Laser drive circuit

Claims (4)

(57) [Claims] 1. A plurality of information tracks on a magneto-optical recording medium.
Record information simultaneously or play multiple information tracks simultaneously
A plurality of light sources and light beams emitted from the plurality of light sources.
Optical spots are respectively placed on a plurality of information tracks on a recording medium.
Means for irradiating a plurality of information
Means for applying an alternating magnetic field of a predetermined frequency to the rack;
Means for pulse-driving a plurality of light sources, for simultaneously recording or reproducing the recording medium.
Information on one of the information tracks
A timing pit indicating the start position of the recordable area is recorded.
If the timing pit is detected, the
While applying an AC magnetic field to the medium from the AC magnetic field applying means,
The plurality of light sources are respectively driven by an AC magnetic field by the driving means.
Synchronize with the peak of one of the positive or negative polarities
Drive to erase the set of information tracks.
Following the erasure, the recording medium is exposed to the AC magnetic field.
While applying an AC magnetic field from the applying means, the driving means
The plurality of light sources according to the signals to be recorded.
Pulse synchronously with the positive or negative polarity peak of the field
A magneto-optical recording / reproducing apparatus for simultaneously performing recording on the pair of information tracks . 2. A set of information tracks in which the plurality of light sources simultaneously connect light spots is assigned the same track number, and recording or reproduction of information is managed in units of the set of information tracks. The magneto-optical recording / reproducing apparatus according to claim 1. 3. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is formatted as a sample servo, and at the same time, a pre-pit is recorded on one of a set of information tracks connecting light spots. Magneto-optical recording and reproducing apparatus. 4. The recording information is image information, comprising: recording signal generating means for separating the image information into signals for each of red, green, and blue pixels and converting the signal into a recording signal. 3. The magneto-optical recording / reproducing apparatus according to claim 1, wherein three light sources are driven by the recording signals for each pixel generated in the step (a), and image information is recorded in parallel on three information tracks.