JPH0346143A - Magneto-optical recording and reproducing device and magneto-optical recording method - Google Patents

Abstract

PURPOSE:To obtain a reproducing signal with small noise, peak shift and jitter by enlarging the intensity of a bias magnetic field to be impressed rather than that of another area in a recorded bit in the front part of the recorded bit to be formed. CONSTITUTION:When a recording signal is applied, a laser beam from an optical head 5 is turned into a recording state and simultaneously, the laser beam is continuously emitted so that the intensity of the laser beam can be fixed. Then, a perpendicular magnetizing film 3 of a magneto-optical disk 1 is locally irradiated with the laser beam and the temperature of this irradiated part in the perpendicular magnetizing film 3 is increased near a Curie point or higher than the Curie point. When the bias magnetic field is impressed, magnetization is determined for the perpendicular magnetizing film 3 of the magneto-optical disk 1 corresponding to the direction and intensity of the magnetic field to be impressed. Then, the bias magnetic field with the intensity further higher than the intensity, which is enough for determining the magnetization of the perpendicular magnetizing film 3, is impressed in the front part of the recorded bit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording/reproducing apparatus and a recording method that are capable of rewriting information by overwriting on a magneto-optical recording medium.

[Prior Art] Conventionally, a method as shown in FIG. 3 has been proposed as a magneto-optical recording device to enable rewriting of information by overwriting.

In FIG. 3, reference numeral 1 indicates a magneto-optical disk, and in this conventional example, this magneto-optical disk is constructed by depositing a perpendicularly magnetized film 3 on a glass substrate 2. This magneto-optical disk 1 is rotated around the central axis 0-0°.

Reference numeral 4 designates an optical head portion that irradiates the perpendicular magnetization film 3 of the magneto-optical disk 1 with laser light. This optical head 4 is composed of a semiconductor laser 5 and a condensing lens 6 as main components, and has a function of always focusing the laser beam on the perpendicularly magnetized film 3, and has the function of always focusing the laser beam on the perpendicularly magnetized film 3, and also has the function of focusing the laser beam on the perpendicularly magnetized film 3 in the radial direction of the magneto-optical disk 1. It is configured to be mobile. Reference numeral 7 denotes an electromagnet that applies a bias magnetic field to the perpendicular magnetization film 3 disposed on the magneto-optical disk 1 so as to face the optical head 4 . This electromagnet 7 is configured to move in the radial direction in conjunction with the optical head 4. Further, the coil 8 connected to the magnetic field modulation circuit 9 is configured to supply a current whose phase is inverted according to the recording signal.

The magnetic field modulation circuit 9 operates according to the recording signal. For example, when the recording signal changes as shown in FIG. It is constructed so that a bias magnetic field strength (C) sufficient to make the direction of magnetization of the film 3 upward is generated at a constant rate, and when the recording signal is "0", it is exactly opposite to when the recording signal is '1'. The optical head is configured to operate with an equal and constant bias magnetic field strength (c) in the direction of The perpendicularly magnetized film 3 of the magneto-optical disk 1 is locally irradiated so that the humidity of the perpendicularly magnetized film in the irradiated area is increased to a level above the cue point.

In the magneto-optical recording device configured in this way, when a recording signal (a) as shown in FIG. 4 is supplied, for example,
The laser beam intensity (b) is continuously driven at an intensity PW sufficient to raise the perpendicularly magnetized film 3 above the cue point. Further, the bias magnetic field strength (c) is generated at a strength of ±H in synchronization with the recording signal (a). Therefore, the perpendicular magnetization film 3 of the optical disk 1 is formed with a recording pattern as schematically shown in FIG. 4(d). Note that in this case, the blank and diagonal recording patterns indicate the states of being magnetized upward and magnetized downward, respectively.

In this conventional magneto-optical recording device, the perpendicular magnetization film 3 of the magneto-optical disk 1 is continuously heated above the cue point by a laser beam, and is magnetized in the direction of the magnetic field modulated according to the recording signal. Regardless of what information is previously recorded on the perpendicular magnetization film 3 of the magneto-optical disk 1, new information can be recorded by overwriting.

[Problems to be Solved by the Invention] However, in the conventional example described above, there is a problem in that the portion (bit edge 40) where the bits of the recording pattern are adjacent to each other becomes uneven as shown in FIG. 4(d).

This is a phenomenon that occurs because the direction of magnetization of the perpendicularly magnetized film 3 becomes unstable when the direction of the applied magnetic field is reversed, that is, in the transition region of the applied magnetic field.

Such an uneven state causes an increase in noise in the reproduced signal, and furthermore, the unclearness of the bit edge portion causes a problem of inducing a peak shift and an increase in jitter.

[Means for Solving the Problems] In view of the above problems, an object of the present invention is to eliminate the unevenness of the edge portion of the recording bit in the transition region of magnetic field modulation, and to provide a good reproduced signal with less noise, peak shift, and jitter. An object of the present invention is to provide a magneto-optical recording/reproducing apparatus and a magneto-optical recording method that can obtain the following.

The magneto-optical recording and reproducing apparatus of the present invention includes means for condensing light onto a magneto-optical recording medium, and bias application means for applying a predetermined bias magnetic field to the recording signal to the condensing portion, and magnetically records bits. A magneto-optical recording/reproducing device that records information by forming a bias magnetic field waveform adjusting means for applying a bias magnetic field stronger in front of a recording bit to be formed than in other areas within the recording bit. It is characterized by

In addition, the magneto-optical recording method of the present invention not only changes the bias magnetic field strength in a square waveform for each recording bit, but also changes it in a temporal range less than one recording bit. The direction of magnetization of the magneto-optical recording medium can be made stable, and by making the edges of the recording bits formed on the magneto-optical recording medium clearer and without unevenness, there is less noise and less peak shift and jitter. You can get a good reproduction signal with less.

[Example] Hereinafter, the magneto-optical recording/reproducing apparatus and magneto-optical recording method of the present invention will be described in detail based on specific examples.

FIG. 1 shows one embodiment of the present invention, in which 1 is a perpendicularly magnetized film 3 on a glass substrate or a plastic substrate 2.
4 is a magneto-optical disk on which a protective film 11 for protecting a perpendicularly magnetized film 3 is coated, 4 is an optical head consisting of a semiconductor laser 5 and a lens 6, and 7 is a coil 8 for supplying current. This shows an electromagnet. Reference numeral 10 denotes a bias magnetic field waveform adjustment circuit which is a means for making the bias magnetic field strength applied to the front part of the recording bit to be formed stronger than that in other areas within the recording bit. This bias magnetic field waveform adjustment circuit 1O is composed of a front detection circuit 10a for a bit to be formed and a current control circuit 10b. Moreover, the magneto-optical disk l has a central axis o-o by a spindle motor (not shown).
It rotates around ”.

Further, the optical head 4 has an AF function in which the laser beam irradiated from the semiconductor laser 5 is always focused on the perpendicularly magnetized film 3, and an AT type function for following the track to be recorded or reproduced. The electromagnet 7 is arranged opposite to the position where the laser beam is focused by the optical head 4, and can move in the radial direction of the optical disc 1 in conjunction with the optical head 4.

In the above configuration, the operation will be described below with reference to the recording operation shown in FIG.

For example, when a recording signal is given as shown in (a), the laser beam from the optical head 5 enters the recording state and is emitted continuously so that the laser beam intensity (b) remains constant at Pw. , the perpendicularly magnetized film 3 of the magneto-optical disk 1 is locally irradiated, and the humidity of the perpendicularly magnetized film 3 in this irradiated portion is increased to near or above the cue point. When a bias magnetic field is applied here, the magnetization of the perpendicularly magnetized film of the magneto-optical disk drive is determined according to the direction and intensity of the applied magnetic field.

Here, in the present invention, as shown in (C), a magnetic field "±Ha" which is stronger than the magnetic field strength "±H" which is sufficient to determine the magnetization of the perpendicular magnetization film 3 at the front part of the recording bit is used.
Apply a bias magnetic field strength with ″′′.

When the direction of application of the bias magnetic field changes from "-H" to "10H", the magnetic field strength applied to the perpendicularly magnetized film 3 momentarily becomes zero, and then a magnetic field in the "10" direction is applied.
The magnetic field strength changes to "+H" until the direction of magnetization of the perpendicularly magnetized film 3 is determined. However, as mentioned above, when the direction of the applied magnetic field is reversed, that is, in the transition region of the applied magnetic field, the direction of magnetization of the perpendicularly magnetized film 3 becomes unstable, as shown in FIG. 4(d) of the conventional example. As described above, unevenness occurs at the edge portion of the recording bit, and therefore, a stronger magnetic field strength, that is, a magnetic field of "±H"' or more, is applied.
)la'' is applied, the direction of magnetization of the perpendicularly magnetized film 3 is determined by the humidity distribution pattern of the perpendicularly magnetized film 3 caused by laser beam irradiation and the strength of the applied magnetic field, so '±H''
The direction of magnetization is determined even in a lower humidity distribution region, that is, in a wider region than the direction of magnetization determined in .

Therefore, a strong magnetic field strength "±Ha" greater than "±H" is applied to the region where the direction of magnetization of the perpendicularly magnetized film 3 generated in the transition region where the magnetic field is reversed is unstable. This determines the magnetization direction of the perpendicularly magnetized film 3. As a result, good recorded bits with no irregularities at the edges of the recorded bits are formed.

Therefore, when a bias magnetic field is applied with an intensity as shown in (C), a recording pattern as shown in (d) is formed, and a recording pattern with good recording bit edges is formed. Here, the white portion and the hatched portion represent that the perpendicularly magnetized film 3 is magnetized upward and downward, respectively. Therefore, the reproduced signal in a state in which such a recording pattern (d) is formed has less noise, less peak shift, and less jitter.

Note that it is clear that the perpendicular magnetization film in the present invention is applicable not only to a single-layer recording medium but also to any multilayer film.

[Effects of the Invention] As explained above, according to the magneto-optical recording device and the magneto-optical recording method of the present invention, it is possible to eliminate the unevenness of the edge portion of the recording bit in the transition region of magnetic field modulation, so that noise can be reduced and This has the effect of making it possible to obtain a good reproduced signal with less peak shift and jitter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the magneto-optical recording/reproducing apparatus of the present invention, and FIG. 2 is an operational diagram illustrating the operation of the magneto-optical recording method of the present invention. FIG. 3 is a block diagram of a conventional magneto-optical recording/reproducing device. FIG. 4 is an operation diagram illustrating the operation of a conventional magneto-optical recording and reproducing apparatus. 1: Magneto-optical disk 2 Glass substrate or plastic substrate 3: Perpendicular magnetization film 4: Optical head 5: Semiconductor laser 6: Condensing lens: Electromagnet 8: Coil: Magnetic field modulation circuit 10: Bias magnetic field waveform adjustment circuit: Protective film

Claims (2)

[Claims] (1) It has a means for focusing light on a magneto-optical recording medium, and a bias applying means for applying a predetermined bias magnetic field to a recording signal at the focused region, and information is recorded by magnetically forming recording bits. A magneto-optical recording and reproducing device for recording, characterized in that it has a bias magnetic field waveform adjustment means that makes the strength of the applied bias magnetic field stronger in the front part of the recording bit to be formed than in other areas within the recording bit. Recording and playback device. (2) Magnetically forming recording bits and recording information by irradiating the magneto-optical recording medium with light, increasing humidity locally, and applying a bias magnetic field corresponding to the recording signal to the high-temperature area. 1. A magneto-optical recording method, characterized in that the bias magnetic field strength is changed in a temporal range less than one recording bit.