JPH04291045A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To enable simultaneous recording on plural tracks by means of magnetic field modulation system by performing a pulse lighting while synchronizing plural light source with the approximate peak position of a positive or negative polarity of an AC magnetic field according to respective recording signals. CONSTITUTION:A recording signal modulation circuit 25 divides a recording signal 24 into three groups, modulates the respective group into a signal corresponding to a recording pattern on an optical disk 6 and outputs them to laser driving circuits 26a to 26c. The laser pulses of the circuits 26a to 26c driven corresponding to the modulation by the circuit 25 is timed with the positive or negative polarity of the AC magnetic field corresponding to a magnetic section to record, and radiated so that its magnetizing direction can be inversed at a position where a modulation signal is '1'. Thus, the data of image information for each picture element can be recorded on the respective information tracks simultaneously, and so the simultaneous recording to the plural track by means of the magnetic field modulation system can be enabled.

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 and reproducing apparatus using a magnetic field modulation method, and more particularly to a magneto-optical recording and reproducing apparatus that uses a plurality of optical spots to simultaneously record on a plurality of information tracks.

0002

BACKGROUND OF THE INVENTION In recent years, magneto-optical disk devices using magneto-optical disks as recording media have a large storage capacity.
There are great expectations for this technology as it can be erased and rewritten. In order to further improve performance, there is active research into overwriting to increase data transfer speed and research to increase storage capacity.

[0003] Overwriting methods are broadly classified into a magnetic field modulation method and an optical modulation method. The magnetic field modulation method is a method of applying a bias magnetic field modulated according to recorded information while irradiating a recording medium with a laser beam of constant intensity. On the other hand, the optical modulation method is a method of applying a constant magnetic field to a recording medium and irradiating the recording medium with a laser beam modulated according to recorded information.

[0004] Recently, a method has also been proposed in which overwriting is performed by irradiating a recording medium with a pulsed laser beam while applying an alternating current magnetic field of a constant frequency to the recording medium. FIG. 6 is a time chart for explaining the recording operation of this recording method.
) is an alternating magnetic field, and (c) is a pulsed laser beam. In this recording method, an alternating current magnetic field synchronized with a reference clock is applied to the recording medium, and a laser beam is irradiated in synchronization with the positive and negative peak positions of this alternating magnetic field. In this case, the laser beam is irradiated at the positive peak point or negative peak point of the alternating current magnetic field based on a signal obtained by modulating the recording signal shown in FIG. 4(d). As a result of the above, the magnetization direction of the temperature-increased portion of the recording medium is oriented in the direction corresponding to the recording signal, and a magnetic domain as shown in FIG. 4(e) is formed. The shape of the magnetic domain formed at this time becomes a feather-like shape, as shown in FIG.

[0005]

[Problems to be Solved by the Invention] However, in the conventional magnetic field modulation method, which is performed while irradiating a laser beam with a constant intensity, if simultaneous recording is performed on multiple tracks using multiple spots, the method disclosed in Japanese Unexamined Patent Publication No. 2-179948 This could only be done on a time-sharing basis as described in . Furthermore, although the optical modulation method basically allows simultaneous recording using a plurality of spots, the optical modulation method itself requires complicated control of the semiconductor laser. Therefore, when there are a plurality of light spots, the control becomes even more complicated, and in addition, the optical modulation disk is expensive, so it is not practical.

The present invention has been made to solve these problems, and its purpose is to provide a magneto-optical recording/reproducing device that uses a magnetic field modulation method but is capable of simultaneously recording multiple tracks using multiple spots. It's about doing.

[0007]

[Means for Solving the Problems] Such an object of the present invention is to provide a plurality of light sources and a spot that connects the light beams emitted from each of the light sources as light spots on a plurality of information tracks of a magneto-optical recording medium. a forming means, an alternating current magnetic field generating means for applying an alternating current magnetic field of a predetermined frequency to a plurality of light spot irradiation parts of the magneto-optical recording medium, and a light source driving means for driving each of the light sources and lighting each light source in a pulsed manner. and recording information in parallel on the plurality of information tracks by lighting each of the light sources in pulses in synchronization with approximately the peak position of the positive or negative polarity of the alternating current magnetic field according to each signal to be recorded. This is achieved by a magneto-optical recording/reproducing device characterized by performing the following.

[0008]

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

In FIG. 1, 1 indicates three semiconductor lasers 1.
A, 1b, and 1c are laser light sources manufactured by hybrid or monolithic. Three laser beams emitted from a laser light source 1 are each collimated by a collimator lens 2, and then modified by a beam shaping prism 3 into a beam having a circular cross section. The light passes through the polarizing beam splitter 4, is focused by the objective lens 5, and is imaged into 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 magnetic field modulation, such as one having a single magnetic layer or one having a two-layer structure utilizing exchange coupling force, is used. Further, the magneto-optical disk 6 is rotated at a predetermined speed by a spindle motor (not shown). A magnetic head 7 is provided facing the objective lens 5 with the magneto-optical disk 6 in between. The magnetic head 7 generates an alternating current magnetic field of a constant frequency in synchronization with the reference clock generated by the reference clock generation circuit 8 by driving the magnetic head drive circuit 9, and applies it to the magneto-optical disk 6.

FIG. 2 shows a light beam 3 focused on a magneto-optical disk 6.
3 is a diagram showing two optical spots and an applied magnetic field of a magnetic head 7. FIG. Three light spots from the laser light source 1 are irradiated onto adjacent information tracks as shown as OS1, OS2, and OS3 in the figure. In this case, the width of the information track and the diameter of each light spot are approximately 1 μm, and the interval x between each light spot is approximately several tens of μm to 100 μm. Further, a circle 27 indicated by a broken line is the range of the effective magnetic field strength of the magnetic head 7. Basically, it is sufficient that three light spots are included in this range, but in consideration of the control performance of the magnetic head 7, it is desirable that the diameter of the range of effective magnetic field strength is on the order of several hundred μm.

Reference numeral 10 denotes a polarizing beam splitter that splits 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 polarizing beam splitter 4, and is reflected to the polarizing beam splitter 10 here. The polarizing beam splitter 10 transmits or reflects the incident light, and the transmitted light beam 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 conventionally well-known push-pull method or knife-edge method. In this case, tracking and focusing error signals are detected separately for the three optical spots,
Tracking and focusing control of the optical head may be performed using each of the average values. Alternatively, each error signal may be typically detected for only one optical spot and used to perform tracking and focusing control of the optical head.

On the other hand, the laser beam reflected by the polarizing beam splitter 10 is guided to a reproduction optical system. First, the polarization direction of the incident light is rotated by 45 degrees by the 1/2 wavelength plate 12 , and then condensed by the condenser lens 13 and incident on the polarizing beam splitter 14 . The polarizing beam splitter 14 transmits or reflects the incident light, and the reflected light is detected by photodetectors 15a, 15b, and 15c corresponding to the three light spots, respectively. Further, the transmitted light of the polarizing beam splitter 14 is detected by the photodetectors 16a, 16b, and 16c corresponding to the three light spots, respectively, as described above. The detection signals of the photodetectors 15a and 16a are processed by a difference signal processor 17.
a, and a magneto-optical signal is generated by taking the difference between the two. The photodetectors 15a and 16a correspond to the above-mentioned optical spot OS1, and each detects its reflected light. Further, the outputs of the photodetectors 15b and 16b are sent to the difference signal processor 17b,
The outputs of the photodetectors 15c and 16c are output to a difference signal processor 17c, and a magneto-optical signal is generated in each difference signal processor. Note that the photodetectors 15b and 16b are optical spot OS
2, the photodetectors 15c and 16c are optical spot OS
Corresponds to 3. The magneto-optical signals from the difference signal processors 17a to 17c are output to the reproduced signal detection circuit 18, where they are demodulated and
A reproduction signal 19 is generated by performing the synthesis process.

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

Reference numeral 25 denotes a recording signal modulation circuit for separating and modulating the recording signal 24 into three parts. In this embodiment, image information is recorded as recording information, and the image information here includes three primary colors R (red), G (green),
It is divided into B (blue), each having 8 bits of gradation. In other words, it is assumed that the recording signal 24 is such that R, G, and B signals are repeatedly sent in time series for each pixel. The recording signal modulation circuit 25 divides the recording signal 24 into three groups. For example, each bit may be divided into a group of a, a group of b, and a group of c, but
Here, it is divided into 8 bits each of R, G, and B, with R being a group, G being a group b, and B being a group c. Further, the recording signal modulation circuit 25 modulates each group into a signal corresponding to the recording pattern on the magneto-optical disk 6. The modulation signals of group a are output to the laser drive circuit 26a, the modulation signals of group b are output to the laser drive circuit 26b, and the modulation signals of group c are output to the laser drive circuit 26c. Each laser drive circuit pulses the corresponding semiconductor laser in accordance with the sent modulation signal, and in combination with the application of an alternating magnetic field, records information on the information track.

Next, the specific operation of this embodiment will be explained in detail with reference to the time chart shown in FIG. First is the recording operation. 3A shows the reference clock generated by the reference clock generation circuit 8, and FIG. 1B shows the alternating current magnetic field generated by the magnetic head 7. The reference clock is output to the magnetic head drive circuit 7, which generates an alternating current magnetic field of a constant frequency synchronized with the reference clock and applies it to the magneto-optical disk 6. Note that the reference clock is the pre-pit detection circuit 21, the reproduction signal detection circuit 18, and the recording signal modulation circuit 25.
is also output.

On the other hand, the optical head is accessed by a moving mechanism (not shown) so that the three optical spots are located on the designated information track. In this case, the pre-pit detection circuit 21 detects the track number while moving to the target information track.In this embodiment, the information track 3 is recorded and reproduced simultaneously using three optical spots.
I will give each book the same track number. As a result, the number of track numbers to be detected can be reduced, and the circuit configuration can be simplified accordingly. Also, instead of always detecting the track number for three light spots,
For example, in the case of rough movement, the track number is detected only with the central light spot, and the track number of the three light spots is detected after the central light spot reaches one of the three target information tracks. may be detected, respectively, and the precision control may be switched to so as to draw each light spot onto a respective target information track. By performing such control, the light spot can be moved onto the target information track at higher speed.

When the three light spots are located on the respective target information tracks, the timing pit detection signal 23 in the pre-pits is detected by the pre-pit detection circuit 21.
This recognizes that the light spot has reached the recording area on the information track. FIG. 3(c) shows the timing pit detection signal. The timing pits may be recorded on all the information tracks and the timing pits of each information track may be detected using three light spots. In this case, recording of information may be started for each information track. Alternatively, timing pits may be recorded only on the central information track, and the arrival of the three light spots to the recording area may be detected based on the detection signal of the pit. At this time, information recording starts at the same time on all three information tracks.

FIG. 4 is a diagram showing a state in which timing pits are recorded on each information track.
, TP2, and TP3 are recorded at the same distance as the interval x between the respective optical spots. In this case, if the timing pits are recorded in a line in the radial direction of the disc, then
The timing of recording and playback is different for each light spot. Therefore, in order to correct this deviation, the capacity of the buffer memory in the recording signal modulation circuit 25 and the reproduction signal detection circuit 18 will increase. Therefore, by arranging the timing pits so that they are parallel to the arrangement of the optical spots OS1, OS2, and OS3, as shown in FIG. 4, the start timings of recording and playback of the three optical spots will not deviate. . Further, FIG. 5 shows an example in which timing pits are detected using only the central light spot, and shows an example of a sample servo format in which all pre-pits are recorded only in the central information track. In the figure, 29 and 30 are a pair of tracking pits, and 31 is a timing pit.

Returning now to FIG. 3. FIG. 5C shows the timing pit detection signal as described above, and in this embodiment, as shown in FIG. 5, the central light spot represents the timing pit detection signal. Note that when detecting prepits, a laser beam of constant power is irradiated from the laser light source 1. When a timing pit is detected, each light spot erases the first few pulses to eliminate any unerased spots, then records the start pit (domain), and then records information according to each modulated signal. .

FIG. 3(d-1) shows a laser pulse of the semiconductor laser 1a driven by the laser drive circuit 26a. The semiconductor laser 1a forms the above-mentioned optical spot OS1 on the information track, and is driven according to the modulation of the recording signal modulation circuit 25. Further, (d-2) in the same figure shows a laser pulse of the semiconductor laser 1b corresponding to the optical spot OS2, and (d-3) in the same figure shows a laser pulse of the semiconductor laser 1c corresponding to the optical 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 alternating current magnetic field is irradiated at the peak position of negative polarity. As a result, the magnetization direction of the laser pulse irradiated portion of each information track is directed downward, and if there is any remaining unerased previously recorded information, it is completely erased and the magnetization direction is returned to the initial state. In this embodiment, the downward magnetization direction is the initial state. FIG. 3(e-1) shows a recording pattern on the information track corresponding to the laser pulse of the semiconductor laser 1a. Further, (e-2) in the same figure shows a recording pattern corresponding to the semiconductor laser 1b, and (e-3) in the same figure shows a recording pattern corresponding to the semiconductor laser 1c. In this recording pattern,
The regions shown in white are magnetic domains with a downward magnetization direction, and the regions shown with diagonal lines are magnetic domains with an upward magnetization direction. It can be seen that in the region irradiated with the two erasing laser pulses, the magnetization direction is downward as described above, and the region is initialized.

[0022] In each laser pulse, the third pulse records a start pit indicating the start position of information recording. Since the start pit is recorded with a modulation signal of "1" as shown in each laser pulse, the start pit laser pulse is irradiated in time with the peak position of the positive polarity of the alternating current magnetic field. As a result, upward magnetic domains are formed on each of the three information tracks, and the upward magnetic domains are recorded only after the timing pit is detected. After this, following the laser pulse for the start pit, the information shown in FIGS. 3(d-1) and (d-2) is displayed on each information track.
, (d-3) are applied. These laser pulses convert image information into R, G,
The light is obtained by modulating the signals separated for each pixel of B, and is irradiated onto three information tracks in parallel. For example, in the laser pulse shown in Fig. 3(d-1), after the third start pit laser pulse is irradiated, the timing is at the positive peak point of the AC magnetic field until just before the next modulation signal "1". In total, two laser pulses are irradiated. Then, the modulation signal becomes “1”, and the next modulation signal “1”
Four laser pulses are irradiated with the timing aligned with the negative peak point of the alternating magnetic field until just before ``.'' In other words, the laser pulses are timed with the positive or negative polarity of the alternating magnetic field depending on the magnetic domain to be recorded. Also, the modulation signal is “1”
As a result, as shown in Figure 3 (e-1), an upward magnetic domain is recorded at first as shown by diagonal lines, then a downward magnetic domain, an upward magnetic domain, and so on. , magnetic domains are recorded according to the sequential modulation signals.Furthermore, 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 the magnetic domains are recorded on each information track. Figure 3 (e-2), (e-3
) are recorded.

As described above, in this embodiment, since the data for each pixel of image information can be recorded in parallel on each information track, the data transfer speed can be greatly increased. In addition, since it is a magnetic field modulation method, it can effectively record on multiple tracks simultaneously, so inexpensive magnetic field modulation disks can be used, and semiconductor laser control is not as complicated as in the optical modulation method. This can be done relatively easily.

On the other hand, when reproducing information recorded on the magneto-optical disk 6, the optical power of each semiconductor laser of the laser light source 1 is first set to a constant reproduction power. Then, as in the case of recording, the three light spots are moved onto the target information track, and each light spot scans each information track at the same time. In this case, the head position of the recorded magnetic domain array is recognized by the timing pit detection signal described above, and the recorded information is thereafter reproduced in the reproduction signal detection circuit 18 based on the outputs of the difference signal processors 17a to 17c. That is, in the reproduced signal detection circuit 18, the difference signal processor 17a
In steps 17c to 17c, the magneto-optical signals generated for each information track are taken in and sequentially demodulated and synthesized. As a result, 3
The information recorded separately for each R, G, and B pixel on the information track of the book is restored to the original image information and 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 R, G, and B pixel is recorded on three information tracks using three semiconductor lasers. Although an example has been shown, the present invention is not limited to this example. For example, it is possible to record information other than image information as recording information, and in that case, the number of information tracks to be recorded simultaneously is not limited to three, but can be arbitrarily set to less than or more than that.

[0026]

As described above, according to the present invention, it is possible to effectively perform simultaneous recording on a plurality of tracks using the magnetic field modulation method, which has been difficult in the past. Therefore, while enjoying the advantages of the magnetic field modulation method such as a simple configuration and the use of an inexpensive recording medium, there is an effect that the data transfer rate can be significantly increased.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an 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 alternating magnetic field.

FIG. 3 is a time chart showing the information recording operation of the embodiment of FIG. 1;

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

FIG. 5 is an explanatory diagram showing timing pits, tracking pits, and light spots when timing pits are 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 device.

[Explanation of symbols]

1 Laser light sources 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, 16
b, 16c Photodetector 17a, 17b, 17c
Difference signal processor 18 Reproduction signal detection circuit 20a, 20b, 20c Sum signal processor 21
Pre-pit detection circuit 25 Recording signal modulation circuit

Claims (7)

[Claims] 1. A plurality of light sources, a spot forming means for forming light beams emitted from each of the light sources onto a plurality of information tracks of a magneto-optical recording medium, and a plurality of light beams of the magneto-optical recording medium. comprising an alternating current magnetic field generating means for applying an alternating magnetic field of a predetermined frequency to a spot irradiation site, and a light source driving means for driving each of the light sources and lighting each light source in a pulsed manner, and recording each of the light sources. A magneto-optical recording and reproducing apparatus characterized in that information is recorded in parallel on the plurality of information tracks by lighting pulses in synchronization with approximately the peak position of the positive or negative polarity of the alternating current magnetic field according to a signal. 2. A timing pit indicating the leading position of an information recordable area is recorded on one of a set of information tracks connecting light spots of the plurality of light sources at the same time, and when the timing pit is detected, a plurality of 2. The magneto-optical recording and reproducing apparatus according to claim 1, wherein recording of information on the information tracks is started at the same time. 3. A timing pit indicating the beginning position of the information recordable area is recorded on each information track, and by detecting the timing pit of each information track,
2. The magneto-optical recording and reproducing apparatus according to claim 1, wherein recording of information is started for each information track. 4. The magneto-optical recording and reproducing apparatus according to claim 1, wherein a light beam for erasing information is irradiated from each of the light sources onto each information track before recording information. 5. A set of information tracks connecting light spots of the plurality of light sources at the same time is given the same track number, and recording or reproduction of information is managed in units of the set of information tracks. 2. The magneto-optical recording and reproducing apparatus according to claim 1. 6. The optical recording medium according to claim 1, wherein the magneto-optical recording medium is formatted as a sample servo, and a pre-pit is recorded on one of a set of information tracks connecting optical spots at the same time. Magnetic recording and reproducing device. 7. The recorded information is image information, and comprises recording signal generation means for separating the image information into signals for each red, green, and blue pixel and converting them into recording signals, the generation means 2. The magneto-optical recording and reproducing apparatus according to claim 1, wherein three light sources are driven by recording signals generated for each pixel, and image information is recorded in parallel on three information tracks.