JPS59215046A - Method for recording and reproducing optomagnetism - Google Patents

Abstract

PURPOSE:To attain ease of reproduction of information by scanning a laser light while vibrating the light in the direction orthogonal to the scanning direction. CONSTITUTION:The laser light from a laser light source 1 and a photomagnetic recording medium 5 are moved relatively and linearly to record the data and the recording width is expanded by vibrating mechanically a fixed mirror 3 or the like. In reproducing the laser light while vibrating the light, the laser light scans on a pit 13 and at the outside of the pit of the photomagnetic medium 5 along a scanning line 14. In eliminating a signal twice the mirror vibrating number from an output signal by means of a filter, a signal shown in the figure is obtained. Even if the pit has a minute defect, when the width of defect is narrower than the pit width, the reproduction is made possible. The detection of a recording track and the tracking of the reproducing head to the recording track are attained easily and sure reproduction is attained even with variation in the manufacture of recording media.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magneto-optical recording and reproducing method that compensates for variations in recording position accuracy of magneto-optical recording materials using a laser beam scanning method.

(Prior art) Recording is performed by irradiating a magneto-optical recording layer of a magneto-optical recording material with a focused laser beam while applying a constant magnetic field, and reversing the magnetic moment of the magneto-optical recording layer in the irradiated area. , a magneto-optical recording and reproducing method for reproducing recorded information by irradiating the magneto-optical recording layer of the magneto-optical recording material recorded in this way with a laser beam and detecting the rotation of the polarization plane of the resulting reflected light. itself is already known. The magneto-optical recording and reproducing method itself allows information to be reproduced without contact, and has the advantage of higher recording density than other recording and reproducing methods.

However, in the optical recording and reproducing method, information is stored in a track with a width of about 1 μm at most, so it is necessary to accurately detect the recording position of the information and scan and reproduce the information so as not to deviate from the track.

When the track is spiral or concentric as in a general magneto-optical recording/reproducing system, if the positional accuracy of the center is maintained to a certain degree, the track will be approximately straight from the periphery to the center of the magneto-optical disk. If scanning is performed, it is relatively easy to detect and follow the track, and deviations in the driving of the magneto-optical disk are periodic and can be dealt with. Such external optical magnetic disks have a large recording capacity and can be randomly accessed, so they are used in the fields of image, audio, and computer storage media. On the other hand, the magneto-optical recording and reproducing method has a high recording density and can also be used as a small, portable recording medium.For example, the magnetic method is currently used for magnetic cards, information cards, product tags, English conversation cards, etc. When used in the field of technology, it is possible to record and reproduce more information on a recording medium of the same size. However, when these recording media are used commercially, there are variations in the dimensional accuracy of the recording media, the accuracy of the recording position, and the running accuracy of the recording media, and the recording on these recording media is not linear. Because of this, a precise drive device is required to detect and track the recorded portion, and the drive bias is random, making playback particularly difficult compared to magneto-optical disks. ing. For example, if a magnetic card is replaced with a magneto-optical recording and reproducing card, its dimensional accuracy is approximately ±50μ to ±100μ, and considering that the diameter of the laser beam is approximately 1μ, the recording area during playback is Measures must be taken to detect this and prevent it from being followed. For detection and tracking of recording section,
Lines created by optical recording or grooves created by mechanical processing are prepared in advance for guidance purposes, and while these guidance lines and grooves are detected and followed optically and mechanically, original information recording is based on these lines. Do this at a position parallel to the groove and at a certain distance.
Attempts have been made to facilitate regeneration. However, provision of such guide grooves and lines and means for detecting these are necessary in addition to recording and reproducing means, and complexity is unavoidable.

(Objective of the Invention) As a result of various studies to eliminate the drawbacks of the above-mentioned prior art, the present inventor has found that a recording medium that records information in a straight line, such as the one shown in the figure, has a high recording density in the straight direction. However, on the other hand, the recording density in the middle direction is often not a critical issue, so if you enlarge the recording in the middle direction, the recording density in the straight direction, and by extension the recording medium itself, will be reduced. We found a way to absorb variations in running accuracy during playback without reducing the recording density, and to vibrate the laser beam perpendicular to the scanning direction when playing back a recording medium recorded in this way. The present invention was also achieved by discovering that information can be easily reproduced.

That is, the present invention provides a magneto-optical recording and reproducing method in which recording and reproducing is performed by focusing and scanning a laser beam while applying a magnetic field to a magneto-optical recording layer of a magneto-optical recording material. The gist of this method is a magneto-optical recording and reproducing method characterized by scanning while vibrating in the perpendicular direction.

(Structure of the Invention) Magneto-optical recording materials that can be used in the present invention include Gd-Co and Gd-Tb-C formed on a smooth and heat-resistant base material by a method such as sputtering.

Examples include those having an amorphous magnetic film such as, but materials other than these may also be used.

To record on these magneto-optical recording materials, conventional methods are used, with some modifications made. For example, as shown in FIG. 1, a laser beam emitted from a laser light source 1 is reflected by a fixed mirror 3 via a polarizer 2, and is focused using a condensing lens 4 to record magneto-optical information on a magneto-optical recording material 5. Layer 6 is irradiated. The magneto-optical recording layer 6 used is one whose magnetization is previously oriented in the perpendicular direction, that is, in the thickness direction of the layer 6. Laser light is irradiated via a magnetic coil 7 between the condenser lens 4 and the magneto-optical recording material 5. Furthermore, in order to reproduce the information recorded on the magneto-optical recording material, the reflected light obtained by irradiating the magneto-optical recording layer with a laser beam is passed through the coil 7 and the condensing lens 4 in the same manner as described above. - One of the split lights is introduced into the fumirror 8, and the other split light is converted into an electrical signal using the analyzer 9 and the photodetector 10, and the other light is converted into an electrical signal and read using the analyzer 11 and the photodetector 12. This is what we do. Analyzers 9 and 1 allow only light in a predetermined direction to pass through, so the magneto-optical recording material 5
Of the reflected lights having different polarization angles depending on the magnetic moment of the magnet, only the reflected lights having a predetermined polarization angle are allowed to pass through.

In addition, in the above-mentioned recording and reproduction, recording is performed if the output of the laser light incident on the magneto-optical recording material 5 is above a certain limit.

In the above method, in the present invention, recording is performed in a straight line while moving the laser beam and the optical recording/reproducing device relatively linearly, and the recording is performed in a direction perpendicular to the length direction of the straight line. Expand the layers. Enlargement can be done in various ways, but if it is done in the same way as the reproduction described later, it is best to vibrate the laser beam in the l] direction. T”c 02 instead of vibrating or using a fixed mirror.
, LIN+) 05 (referred to as an "acousto-optic polarizer"), and generates ultrasonic waves in the crystal to diffract laser light.

The frequency of vibration, vibration l] etc. vary depending on conditions such as the manufacturing precision of the optical recording material and the diameter of the laser beam, so it cannot be stated unconditionally, but if it is for the above-mentioned recording medium, the dimensions of the magneto-optical recording material. The accuracy is ±50μ to ±100μ, and if the diameter of the laser beam in the condensed state is 1μ and the scanning speed of the magneto-optical recording material is 100 ytrm/see,
The frequency of the vibration is, for example, 10 Q kHz, on II, the vibration [11 is at least 100 μ on optical recording 4'A
It is 200μ. Regarding the above conditions and vibrations, the above numerical values are just examples and are not restricted to these, but the laser beam diameter is usually about 0.5μ to 1.5μ,
If the diameter of the laser beam is increased, the accuracy of the shape of each pit will deteriorate, so a smaller diameter is preferable. The length of each pit in the linear scanning direction is usually about 5 to 50 microns. Furthermore, the scanning speed of magneto-optical recording materials is faster than the scanning speed of current magnetic cards (8.
0vm/5ee) may be used as the basic value, but it is not limited to this. The frequency of the laser beam during scanning is determined by dividing the scanning speed of the magneto-optical recording material by the diameter of the laser beam, and the amplitude should be sufficient to cover the range of variations in the dimensions of the optical recording material.

When reproducing the magneto-optical recording material that has been subjected to magneto-optical recording in this way, a known method as shown in FIG. It is sufficient to add vibration in a direction perpendicular to the scanning direction using a method such as this, and the frequency and amplitude of vibration should be the same as in recording, but if possible, vibration 1] should be slightly larger. good.

In the present invention, when reproduction is performed while the laser beam is vibrated, an external signal is output as shown in FIG. 2 fa). This is because, as shown in FIG. 3, the laser beam scans over the pits (indentations in recorded areas) 13 of the magneto-optical recording material 5 as well as over the areas outside the pits along the meandering scanning line 14. This is because the output signal changes during the time the pit is scanned. When a signal having twice the mirror frequency is removed from the output signal as shown in FIG. 2(a) by a filter, a signal as shown in FIG. 2(b) is obtained. By performing this kind of operation on the output signal, for example, even if there is a minute defect in one pit, if the width of the defective part is narrower than the width of the pit (in the pit in the direction perpendicular to the scanning direction), playback can be performed. It can be made possible.

Since the present invention has the above configuration, it is easy to detect a recording track during optical recording and reproduction, and the reproduction head can easily follow the recording track, and there are no manufacturing variations in optical recording and reproduction type recording media. Furthermore, the method of the present invention ensures reliability when using a recording medium with a high recording density. can.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the method of the present invention;
b) is a diagram showing the output signal obtained by the method of the invention, and FIG. 3 is a diagram showing the scanning line of the laser beam. 1... Racer light source 2... Polarizer 3... Fixed mirror 4... Condensing lens 5. ......Magneto-optical recording material 6...Magneto-optical recording layer 7...Magnetic coil 8...Half mirror 9, 11... Analyzer 10, 1.2... Photodetector 13... Pit 14...
・・・・・・・・・・・・Scanning line 1st figure 2nd figure to+ 2nd figure [bl 8th figure-29:

Claims (1)

[Claims] (1) In a magneto-optical recording and reproducing method in which recording and reproduction is performed by focusing and scanning a laser beam while applying a magnetic field to the magneto-optical recording layer of a magneto-optical recording material, the laser beam is directed in a direction perpendicular to the scanning direction. A magneto-optical recording and reproducing method characterized by scanning while vibrating.