JPH026139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording/reproducing device using a magnetic tape or the like, and improves the recording density by scanning a laser beam in a direction perpendicular to the tape running direction. The purpose is to make it readable with a simple structure.

Conventional methods for high-density recording on magnetic tape include a method using a rotating head, a method using a multihead, and a method using magneto-optical recording.

The method using a rotating head has the advantage of increasing recording density and simplifying the electrical circuit compared to a multi-head method, but since the head rotates at high speed, it causes severe wear on the head and tape, generates noise, and There were problems such as dew condensation, severe precision in the rotating head and running system, susceptibility to tape deformation, and difficulty in tape editing.

In the method of using multi-heads, it is difficult to make the space between the heads extremely small, so the recording density is low, it is difficult to create small and highly sensitive heads, and the number of signal processing circuits required for each head increases, which increases costs. , there were problems such as the need to run the tape at high speed in order to increase the relative speed with the tape.

In addition to the above methods, there is a magneto-optical recording method as a method for increasing recording density.

Figure 1 shows an example of a magneto-optical recording system that has already been proposed (NHK Technical Monthly Report, May 1974, "Study of magneto-optical recording system" Nomura et al.).

In FIG. 1, 1 is a magnetic tape, 2 is a recording magnetic head, 3 is a laser light source, 4 is a cylindrical lens, 5 is a converging lens, and 6 is a reproducing magnetic head.

The operation of the magneto-optical recording and reproducing apparatus shown in FIG. 1 will be briefly explained.

During recording, the magnetic head 2 applies a weak magnetic field corresponding to the recording signal to the magnetic tape 1, and the optical systems 3, 4, and 5 irradiate a laser beam to raise the temperature of that area to around the Curie temperature. ,
magnetically saturated. Next, when the beam passes through and the temperature drops, residual magnetization remains and a signal is recorded in the form shown in FIG.

In FIG. 2, reference numeral 1 indicates the magnetic tape, and arrows 7 indicate the direction of magnetization in each minute section on the recording track.

In this type of magneto-optical recording, as the temperature increases and approaches the Curie temperature, as shown in Figure 3b,
Magnetic saturation is easy to occur even in a weak magnetic field, and if the temperature is lowered in that state, the residual magnetization will increase as shown in Figure 3, for example B.
This takes advantage of the property of magnetic materials that the intensity increases from point to point A.

In Figure 3, a is the B-H curve at low temperature, b
is the BH curve at high temperature.

Further, FIG. 4 shows the relationship between residual magnetization and temperature. In FIG. 4, T _C is the Curie temperature of the magnetic material, and C and D indicate the residual magnetization at low and high temperatures, respectively.

In this way, in the magneto-optical recording method, the magnetic head 2 applies a weak magnetic field and the laser beam heats only a minute area, so the signal is recorded only in the area irradiated with the laser beam and not in other areas. Not recorded.

From this, the recording density is determined by the spot diameter of the laser beam, regardless of the gap of the magnetic head, so that the recording density can be extremely high.

Next, a method for reproducing what has been recorded in this manner will be described.

In the method shown in FIG. 1, a reproducing head 6 is used to perform reproduction. However, in order to read recorded signals with such short recording wavelengths, the gap of the reproducing head 6 must be very narrow and must be as close to the magnetic material as possible, but due to the thickness of the magnetic material and the protective film, it is necessary to make it close enough. That was difficult.
Furthermore, since the track width is determined by the gap length of the magnetic head, it cannot be made very narrow, making it unsuitable for high-density recording.

Therefore, as a method of reading such a recording signal having a short recording wavelength, there is a method of using a magnetic force effect.

This uses the property that when polarized light is applied to a magnetized substance, the polarization angle of the reflected or transmitted light rotates depending on the strength of magnetization. For example, as shown in Figure 5. As shown, a laser beam is applied to a magnetic material through a polarizing plate 8, and the reflected light with a rotated polarization angle is passed through another polarizing plate 9.
The light is received by the light receiver 10. At this time, the polarizing plate 8 is
The magnetic vector of the incident light is set to be perpendicular to the magnetization vector of the magnetic material, and the polarizing plate 9 is
If you set the polarization angle of the reflected light slightly off from the right angle when the magnetic material is not magnetized,
Depending on the rotation of the polarization angle of the reflected light, the amount of light entering the receiver changes and can be read.

However, since the amount of rotation of the polarization angle due to this magnetic force effect is very small, during readout, the signal-to-noise ratio is poor due to the influence of disturbances such as unevenness on the magnetic surface and scratches, dust, etc. Have difficulty. Further, in order to perform such reading, it is necessary to use a magnetic material with a high reflectance, but the reflectance of commonly used magnetic tapes is low. Therefore, in order to read out signals from magnetic tape using the magnetic force effect, a method is used in which the signal is first transferred to a magnetic material with a high reflectance and a large magnetic force effect, and then read out using the magnetic force effect. ing.

However, methods that require such a transfer procedure are complicated, and there are also problems in that it is difficult to read out immediately after recording.

In addition, in the method shown in Fig. 1, the recording track is in the tape running direction as shown in Fig. 2, and is very narrow, so during playback, the tape may shake or
There is a problem in that tracking becomes extremely difficult due to undulations and the like. Therefore, there was a problem in that the track pitch could not be made very narrow and the recording density could not be increased very much.

Furthermore, even when using the magnetic force effect, if the track pitch is made too narrow, a closed loop of magnetic lines of force will be created between the tracks, and almost no lines of magnetic force will come out of the magnetic material, making transfer impossible. There was a problem that the recording density could not be increased much.

The present invention solves the above problems and has a simple configuration.
An object of the present invention is to provide a magneto-optical recording and reproducing device that performs high-density magneto-optical recording and reads the recorded information.

In the present invention, when a magnetic material is irradiated with a laser beam during reproduction as well as during recording, the magnetic head detects the change in residual magnetization, for example, from point C to point D, as shown in FIG. The invention is based on a method of reading out data by reading the information (a method filed by the same applicant on November 27, 1982), and one embodiment of the present invention is shown in FIG.

In FIG. 6, 1 is a magnetic tape, 2 is a magnetic head, 3 is a laser light source, 11 is a laser beam, 12 is a rotating mirror for laser beam scanning, 13
are the capstan and idler for tape running.

The embodiment shown in FIG. 6 is basically used for both recording and reproduction.

First, during recording, the laser beam 11 is scanned along the gap of the magnetic head 2 by the rotating mirror 12 while the tape 1 is running, and when a recording signal is injected into the magnetic head 2, the magnetic tape 1 is as shown in FIG. It is magnetized as shown by arrow 7 and magneto-optically recorded.

Next, when reproducing this, the laser beam 11 is similarly scanned along the gap of the magnetic head 2 while the tape 1 is running, and the recording track is traced. Since the residual magnetization decreases rapidly,
By detecting the change with the magnetic head 2, the recorded information can be read.

In the case of readout according to the above embodiment, the change in residual magnetization of the micro region irradiated with the laser beam is:
Since it is not canceled out by the magnetization of other minute regions, it can be read even when the recording density is increased to the limit determined by the laser beam spot diameter.

As shown in Figure 7, if there are places where the magnetizations of adjacent minute regions are opposite and parallel to each other, the lines of magnetic force cancel each other out, making transfer impossible. Although reading is not possible, reading is possible in the above embodiment as described above.

In the case of readout according to the above embodiment, the magnetization of the minute region of the magnetic material that is not hit by the laser beam also crosses the gap of the magnetic head 2, so it is detected and becomes a noise component. Since the frequency component is extremely low compared to the frequency component of the signal detected by scanning, it can be easily removed using a high-pass filter or the like. Since the ratio of the two frequency components is about twice the number of signals recorded per scan, it can be said that they are sufficiently far apart.

In the embodiment shown in FIG. 6, a rotating mirror 12 is used as the laser beam scanning means, but instead of the rotating mirror, a mirror attached to a piezoelectric plate, a magnetostrictive plate, etc. may also be used.

Furthermore, in the embodiment shown in Fig. 6, the magnetic head is applied to one side of the magnetic body and the laser beam is irradiated from the other side, but it is also possible to apply the laser beam from the same side. .

An example specifically showing the above configuration is shown in FIG. In FIG. 8, 1 to 3 correspond to the same numbers in FIG. 6, 14 is a mirror, and 15 is a mirror 14.
A piezoelectric plate or a magnetostrictive plate 16 is used to drive the laser beam to scan the laser beam, and 16 is a prism that reflects the laser beam inside the magnetic head and irradiates the magnetic material 1 through the gap.

Note that this prism 16 may be replaced with a mirror. Further, in this case, a converging lens for focusing the laser beam may also be incorporated inside the magnetic head.

Next, tracking during playback will be explained.

During recording, the laser beam is scanned perpendicularly to the tape running direction, but during playback it is necessary to scan exactly the same location (recording track) as during recording. If this scanning location deviates from the recording track, problems such as a drop in the level of the detection signal and the mixing of signals from adjacent tracks, resulting in crosstalk, are extremely difficult to perform accurately. It becomes important.

As one method for accurately tracking, during recording, a low frequency synchronization signal synchronized with scanning is recorded by the magnetic head 2, separately from the recording signal. The recording position of this synchronization signal on the tape maintains a certain relationship with the position of the recording track. (It is preferable to record and reproduce this synchronizing signal during the scanning pause period that occurs between each scan.) When reproducing, the magnetic head first detects the synchronizing signal and controls the scanning to be performed in synchronization with it. This enables accurate tracking.

The object to be controlled may be the tape running speed or the scanning speed of the laser beam.

The scanning speed of the laser beam is kept constant,
If the tape running speed is controlled, it has the effect of canceling out wow and flutter caused by the running system, and it is also possible to keep the tape running speed constant and control the scanning speed of the laser beam. In this case, there is an advantage that the control response is quick and stable tracking control can be performed.

For the above-mentioned tracking control, it is necessary to extract a signal corresponding to scanning and compare the phase with the synchronization signal. For example, when scanning is performed using a rotating mirror, the rotation angle of the mirror can be directly detected. It's difficult to do. Therefore, it is effective to use the recording signal itself detected by the magnetic head as the signal corresponding to scanning.

Further, recording and reproducing of the synchronization signal for tracking control may be performed using the magnetic head 2 for recording and reproducing the recording signal as described above, but a magnetic head 2 for recording and reproducing the synchronization signal may be used separately. An auxiliary magnetic head may also be provided. In that case, the relative positional relationship between the auxiliary magnetic head and the main magnetic head 2 must be fixed.

Also, other methods of tracking will be described.

First, during recording, recording is performed so that areas with wide track intervals and areas with narrow track intervals are alternately lined up for each scan.
If it is scanned at equal intervals during playback, if the tracking is correct, the readout signal level for each scan will be the same, but if the tracking is off, the readout signal level for the odd and even scans will be the same. One of them is large and the other is small. Even if the control is performed based on the magnitude relationship, tracking control can be performed.

Next, during reproduction, the present invention heats the recorded magnetic material with a laser beam and reads the change in residual magnetization as the temperature rises. If it exceeds the Curie temperature, the recording will be erased, so if you want to reproduce it repeatedly, it is necessary to control the temperature of the magnetic material by laser beam irradiation so that it does not exceed the Curie temperature. One of the methods will be described below.

As can be seen from FIG. 4, the closer the temperature rise due to heating during reproduction approaches the Curie temperature T _C , the larger the change in residual magnetization becomes, and therefore the signal level detected by the magnetic head also becomes larger.

Using this property, the detected signal level is
For example, the output of the laser light source may be controlled so as not to exceed a predetermined level. The predetermined level may be set by changing it depending on the ambient temperature, tape speed, scanning speed, etc.

By the way, in the present invention, if there is lateral wobbling of the tape during tape running, fluctuations occur in the timing of reading in each scan. Further, there is no connection between each scan, and there is a pause period. Therefore, when recording, first, the information to be recorded is divided into sections of a certain amount of time, and the information is processed and recorded into one scan. Then, during playback, if each scan is detected, processed, temporarily stored, and sequentially output at a constant speed, the tape as described above can be reproduced. The effects of sideways movement can be removed.

Note that the magnetic material used in the present invention is not only effective for the above-mentioned magnetic tape, but also for magnetic materials such as magnetic disks and magnetic cards.

As described above, according to the present invention, a magnetic head, a traveling means for relatively traveling a magnetic material along the magnetic head, a laser light source, and a laser beam generated from the laser light source are directed to the magnetic head. It consists of a beam scanning means for scanning along the slit of the gap, and the recording signal is injected into the magnetic head during recording, and the recording signal is read from the magnetic head during reproduction. ) Enables extremely high-density recording and playback.

(2) When reading data, there is no need for transfer unlike methods that use magnetic force effects, and the data can be reproduced immediately after recording.

(3) Ordinary magnetic tapes and magnetic disks can be used.

(4) Less wear and noise compared to rotating head systems.

(5) Easier to edit compared to the rotating head method.

(6) Compared to the multihead system, the tape speed can be lower.

(7) Level drop in detection signals and crosstalk between tracks can be extremely reduced.

This excellent effect can be obtained.

[Brief explanation of drawings]

Figure 1 shows a conventional magneto-optical recording device, Figure 2 shows a conventional magneto-optical recording device.
The figure shows the recording pattern recorded by the device in Figure 1, Figures 3 and 4 show the temperature characteristics of the magnetic material, and Figure 5 explains the conventional reading method using magnetic force-effect. FIG. 6 is a perspective view showing one embodiment of the present invention, FIG. 7 is a diagram showing a recording pattern recorded by the present invention, and FIG. 8 is a perspective view of another embodiment of the present invention. be. DESCRIPTION OF SYMBOLS 1... Magnetic material, 2... Magnetic head, 3... Laser light source, 11... Laser beam, 12... Rotating mirror, 13... Traveling means, 14... Mirror, 15... Mirror angle or position Means of regulation, 16...prism.

Claims (1)

[Scope of Claims] 1. A magnetic head, a traveling means for relatively traveling a magnetic material along the magnetic head, a laser light source, and a laser beam generated from the laser light source in the gap of the magnetic head. It consists of a beam scanning means for scanning along the slit, and when recording, the recording signal is injected into the magnetic head, and when reproducing, the recording signal is read from the magnetic head. 1. A magneto-optical recording and reproducing apparatus characterized in that a traveling means or a beam scanning means is tracking-controlled so as to match the track. 2. In claim 1, even-numbered beam scans are slightly advanced or delayed relative to odd-numbered beam scans during at least one of recording and reproduction, and during reproduction, 1. A magneto-optical recording/reproducing device characterized in that a reproduction signal level during odd-numbered scanning and a reproduction signal level during even-numbered scanning are compared, and tracking control is performed based on the comparison output signal. 3 In claim 1, at the time of recording,
1. A magneto-optical recording and reproducing apparatus characterized in that a synchronizing signal for tracking control synchronized with beam scanning is injected into a magnetic head together with a recording signal. 4. A magneto-optical recording and reproducing apparatus according to claim 3, characterized in that the synchronization signal is recorded during a pause period of beam scanning. 5. A magneto-optical recording and reproducing device according to claim 1, comprising an auxiliary magnetic head having a fixed relative positional relationship with the magnetic head and for recording and reproducing a synchronization signal for tracking control. . 6. Claim 3 or 5 is characterized in that, during reproduction, tracking control is performed based on the phase difference between the synchronization signal and the recorded signal read by the magnetic head. Magneto-optical recording and reproducing device. 7 In claim 1, by controlling the output of the laser light source according to the reproduction signal level during reproduction, the local temperature rise of the magnetic material due to laser beam irradiation is prevented from exceeding the Curie temperature. A magneto-optical recording/reproducing device characterized by: 8. The magneto-optical device according to claim 7, characterized in that the output of the laser oscillator is controlled so that the reproduced signal level does not exceed a predetermined level set based on ambient temperature and running speed. Recording and playback device. 9 In claim 1, upon reproduction,
1. A magneto-optical recording/reproducing device characterized in that a recording signal is extracted from a magnetic head via a high-pass or band-pass filter. 10 In claim 1, by temporarily storing the recorded signal taken out for each scan during reproduction and sending it out at a constant speed, the vibration in the direction perpendicular to the running direction of the magnetic material and the running speed are reduced. A magneto-optical recording and reproducing device characterized in that it corrects fluctuations on the time axis due to unevenness.