JP2839102B2 - Magneto-optical recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an overwritable type in which an applied magnetic field is inverted at a single frequency, and recording is performed by irradiating a pulsed laser beam in synchronization with the inverted magnetic field. The present invention relates to a magneto-optical recording device.

2. Description of the Related Art Conventionally, as one type of magneto-optical recording apparatus capable of rewriting information by overwriting, a magnetic field applied at a single frequency which is a channel clock used for modulating data to be recorded or a multiple of the channel clock is used. A magneto-optical recording apparatus that modulates using a circuit and irradiates a pulsed laser beam in synchronization with the modulation magnetic field to perform recording has been considered.

FIG. 3 is a diagram showing the configuration of an example of such a conventional apparatus.

In FIG. 3, reference numeral 1 denotes a magneto-optical disk, and in this example, the magneto-optical disk 1 is a plastic substrate 2
Is formed by applying a perpendicular magnetization film 3 and further applying a protective film 4 on the substrate, so as to rotate about a central axis 0-0 '.

Reference numeral 8 denotes an optical head that irradiates the perpendicular magnetic film 3 of the magneto-optical disk 1 with laser light. The optical head 8 includes a semiconductor laser 5, a condenser lens 6, and a condenser lens driving actuator 7 as main components, and has a function of always focusing laser light on the perpendicular magnetization film 3. The magnetic disk 1 is configured to be movable in the radial direction. Reference numeral 10 denotes an electromagnet which is disposed so as to face the optical head 8 with respect to the magneto-optical disk 1 and applies a magnetic field to the perpendicular magnetization film 3. The electromagnet 10 is arranged so that a generated magnetic field is maximized at a portion where a recording pit is formed. The electromagnet 10 is configured to move in conjunction with the optical head 8. The electromagnet 10 is supplied with current by a coil 9 connected to the resonance type magnetic head driver 11 at a channel lock of a modulation system of data to be recorded or at a single frequency which is a multiple of the channel lock. When the magnetic field strength required for recording is ± H, a magnetic field of ± H or more is generated as a peak value. The resonance type magnetic head driver 11 is configured with a capacitor 17 as a main element, and is driven at a frequency input from an oscillator 16.
The laser light emitted from the optical head 8 is applied to a modulation magnetic field generated by the electromagnet 10 at a desired position in a pulse shape by an optical modulation circuit 15 that determines a phase and a pulse width. The light modulation circuit 15 includes a phase adjustment circuit 14 that determines the timing of irradiating the modulation magnetic field with laser light, and a pulse width modulation circuit 13 that determines the time of laser light irradiation.

The phase adjustment circuit 14 is driven by a channel clock output from the oscillator 16 that drives the resonance type magnetic head driver 11, or a clock of the same frequency synchronized with a single frequency that is a multiple of the channel clock, and a recording signal, The timing of irradiating the generated magnetic field with laser light is determined.

The pulse width adjustment circuit 13 has a function of determining a desired laser light irradiation time based on the laser light irradiation timing signal determined by the phase adjustment circuit 14.

In the magneto-optical recording apparatus configured as described above, consider a case where an NRZ signal is supplied as a recording signal (b) by a modulation method such as 2.7 modulation or EFM modulation as shown in FIG. At this time, the clock supplied to the phase adjustment circuit 14 is as shown in clock (a). In this example, the frequency is the same as the channel clock. The change in the magnetic field applied on the perpendicular magnetization film 3 is as shown in the modulation magnetic field (c). At the highest point of the modulation magnetic field intensity, a value sufficiently exceeding the magnetic field intensity ± H required for recording is supplied. It has become.

When the input is given at such a timing, when the recording signal is “1”, the laser beam is irradiated at the time when the magnetic field of the magnetic field strength “+ H” is applied, and the recording signal is “0”. In the case of "", the laser light is irradiated at the time when the magnetic field of "-H" is applied. Therefore, the pulsed output of the laser beam is (d) with respect to the modulation magnetic field (c).
become that way. However, here, fine timing such as the time required for the temperature rise of the perpendicular magnetization film 3 after laser beam irradiation is not considered.

When the laser beam is irradiated at such timing,
Since the moving speed of the magneto-optical disk 1 is determined so that the pit shape formed by one laser light irradiation is sufficiently large with respect to the laser light irradiation pulse interval, the recording pit pattern formed is The result is as shown in a recording pattern (e). Here, the white and shaded portions of the recording pattern (e) indicate a state in which the perpendicular magnetization film 3 is magnetized in directions corresponding to “1” and “0” of the recording signal (b), respectively.

Thus, the magneto-optical recording apparatus of the present embodiment selectively irradiates a pulse-modulated laser beam to a magnetic field modulated at a single frequency in accordance with a recording signal, and responds to the recording signal. Since the perpendicular magnetization film 3 is magnetized in the direction, regardless of what information is 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 above conventional example, as shown in FIG. 4, since the laser beam irradiation is selectively performed on the modulation magnetic field (c), the recording signal (b) is set to “0”. There is a difference in the laser irradiation timing with respect to the change of the recording signal (b) between the case where "1" changes to "1" and the case where "1" changes to "0". For example, assuming that the modulation of the magnetic field is the same frequency as the channel clock of the code modulation method, one cycle of the channel clock is 1T.
If the recording signal (b) changes from “1” to “0” with reference to the laser irradiation timing for the change of the recording signal when the recording signal (b) changes from “0” to “1”, Will be delayed by 0.5T.
Therefore, the recording pattern is "1" in the conventional example of FIG.
0.5T longer when "0" is recorded and 0.5T when "0" is recorded
The recording is short, and the reproduction signal (f) obtained from the recording pattern cannot reproduce the recording signal (b) faithfully.

[Means and Actions for Solving the Problems] The present invention provides, as a means for solving the above-mentioned problems, a method of applying a light beam to a recording signal while applying a magnetic field modulated at a constant period to a magneto-optical recording medium. In a magneto-optical recording device that performs recording by irradiating in a pulse shape in accordance with the cycle of an applied magnetic field, after the change of the recording signal, the first timing of irradiating the laser beam for recording the recording signal; as well as/
Or means for irradiating the irradiation time and / or the irradiation intensity differently with respect to the other irradiation times after the change, and when the recording signal changes, the recording pit length generated by the periodicity of the applied magnetic field. It is an object of the present invention to provide a magneto-optical recording device characterized by controlling a change.

Further, at the time of the first laser beam irradiation after the recording signal changes to a recording signal corresponding to the longer recording pit length, the irradiation timing is delayed with respect to the other irradiation after the change. And / or shortening the irradiation time, and / or reducing the irradiation intensity, and the first laser beam irradiation after the recording signal changes to a recording signal corresponding to the shorter recording pit length. Time, the irradiation timing is made earlier and / or the irradiation time is made longer with respect to other operations after the change, and / or
Another object of the present invention is to solve the above-mentioned problem by using a magneto-optical recording device, which comprises means for increasing the irradiation intensity.

According to the present invention, with respect to the first laser light irradiation after the transition of the recording signal, the means for earlier or later the irradiation timing of the laser light with respect to the modulation magnetic field according to the change of the recording signal, and the laser light irradiation time By providing a means for lengthening or shortening, and a means for increasing or decreasing the laser beam intensity, all, selectively, or independently, a recording pattern due to a timing shift between a recording signal and a modulation magnetic field is provided. The deviation can be corrected, and a recording pattern faithful to the recording signal can be created. This also makes it possible to obtain a reproduced signal that faithfully reproduces the recorded signal.

Embodiment FIG. 1 is a diagram showing a configuration of one embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a magneto-optical disk. In this example, the magneto-optical disk 1 is constituted by applying a perpendicular magnetization film 3 to a plastic substrate 2 and further attaching a protective film 4 to the center. It is configured to rotate about the axis 0-0 '.

Reference numeral 8 denotes an optical head for irradiating the perpendicular magnetic film 3 of the magneto-optical disk 1 with a laser beam to raise the temperature of the perpendicular magnetic film 3 at the irradiated portion to a temperature near the Curie point or above the Curie point. . The optical head 8 includes a semiconductor laser 5, a condenser lens 6, and a condenser lens driving actuator 7 as main components. The laser head always focuses on a recording / reproducing position of the perpendicular magnetization film 3. Auto focus and auto tracking functions,
The optical disk 1 is configured to be movable in the radial direction.

Reference numeral 10 denotes an electromagnet which is disposed so as to face the optical head 8 with respect to the magneto-optical disk 1 and applies a recording magnetic field to the perpendicular magnetization film 3. The electromagnet 10 is arranged so that a generated magnetic field is maximized at a portion where a recording pit is formed. The electromagnet 10 is configured to move in conjunction with the optical head 8 for the above-described reason. The electromagnet 10 is supplied with a current at a single frequency of a channel clock of a modulation system of data to be recorded by the coil 9 connected to the resonance type magnetic head driver 11 or a multiple thereof, and as a result, the perpendicular magnetization Magnetic field strength required for recording on film 3 ±
It is configured to generate a magnetic field of H or more as a peak value. The resonance type magnetic head driver 11 includes a capacitor 17
And is driven by a channel clock input from the oscillator 16 or a signal of a single frequency which is a multiple thereof.

The irradiation timing, irradiation time, and laser light intensity of the laser light irradiated from the optical head 8 with respect to the modulation magnetic field generated by the electromagnet 10 are determined by the light modulation circuit 15. The light modulation circuit 15 includes a phase adjustment circuit 14, a pulse width adjustment circuit 13, and a laser (LD) power control circuit 12.

With respect to the first laser light irradiation after the transition of the recording signal, the laser light irradiation timing is advanced or delayed, the laser light irradiation time is lengthened or shortened, or the laser light intensity is increased. An embodiment in which all means for weakening are provided will be described.

The phase adjustment circuit 14 determines the laser beam irradiation timing for the modulated magnetic field generated by the electromagnet 10. In this example, when the recording signal changes from “0” to “1” (when the recording signal changes to a recording signal corresponding to a longer recording pit length), the first laser beam irradiation timing for the modulation magnetic field is set next. When the recording signal changes from "1" to "0" (when the recording signal changes to a recording signal corresponding to a shorter recording pit length), In the case where the laser beam irradiation timing of a half cycle of the conventional modulation magnetic field is delayed due to the periodicity of the modulation magnetic field as compared with the case where “0” changes from “0” to “1”, the first laser beam irradiation timing for the modulation magnetic field Has a function of delaying the following laser beam irradiation timing. In addition, the phase adjustment circuit 14 also has a function of making the laser beam irradiation timing in other cases constant with respect to the modulation magnetic field.

The pulse width adjusting circuit 13 determines a laser light irradiation time. In this example, the first laser light irradiation time when the recording signal changes from “0” to “1” is shorter than the subsequent laser light irradiation time, and conversely, the recording signal changes from “1” to “0”. When the recording signal changes to “0”.
Due to the periodicity of the modulating magnetic field, when the laser beam irradiation timing is delayed by half the period of the conventional modulating magnetic field, the laser beam irradiation time is made longer than the subsequent laser beam irradiation time as compared with the case where the modulation field changes from “1” to “1”. Has functions. The pulse width adjustment circuit 13 also has a function of keeping the laser light irradiation time constant in other cases.

The laser power control circuit 12 determines the laser light output intensity. In this example, the recording signal is “0”
The first laser light output intensity when changing from "1" to "1" is made weaker than the next laser light output intensity, and conversely when the recording signal changes from "1" to "0", that is, Compared with the case where the recording signal changes from “0” to “1”, due to the periodicity of the modulation magnetic field, when the laser light irradiation timing of the half cycle of the conventional modulation magnetic field is delayed, the laser light output intensity continues next. It has the function of making it stronger than the laser light output intensity. Further, the laser power control circuit 12 has a function of keeping the laser light output intensity constant in other cases.

FIG. 2 is a diagram showing a timing chart of each signal and a recording pattern when a recording signal is input as shown in FIG. 2B in the above configuration.

In FIG. 2, the magnetic field applied on the magneto-optical disk 1 is as shown in FIG. In this state, when the recording signal (b) changes from “0” to “1” as shown in FIG.
Is output so as to be later than the next laser irradiation timing (b). Conversely, when the recording signal changes from “1” to “0”, the first laser irradiation timing after the recording signal changes Laser irradiation timing following (c) (d)
Output so that it is faster than

After the laser irradiation timing is determined by the phase adjustment circuit 14, it is input to the pulse width adjustment circuit 13, and the laser irradiation time is determined as in the pulse width adjustment circuit output (e).
Here, the first signal when the recording signal changes from “0” to “1”
The second laser irradiation time is set shorter than the subsequent laser irradiation time. Conversely, when the recording signal changes from “1” to “0”, the first laser light irradiation time is set to the next laser irradiation time. It is set longer than the irradiation time.

After setting the laser beam irradiation time, the laser beam intensity is finally determined. The laser beam intensity also changes the laser beam intensity at the first time after the change of the recording signal, similarly to the laser beam irradiation timing and the laser beam irradiation time. That is, the laser light output intensity at the timing (a) at which the recording signal changes from “0” to “1” is set to be weaker than the laser light output intensity at the following (b), and conversely, the recording signal becomes “ The laser light output intensity at the timing of (c) changing from 1 "to" 0 "is set to be stronger than the laser light output intensity of the following (d).

As a result, the laser beam output becomes as shown in FIG. 7F, and the recording pit pattern recorded in such a state is schematically shown as a recording pattern (g).

Here, the white and shaded portions of the recording pattern (g) indicate a state in which the perpendicular magnetization film 3 is magnetized in directions corresponding to “1” and “0” of the recording signal, respectively.

The reproduced signal obtained from such a recording pattern (g) is as shown in FIG. 2 (h), and is a faithful reproduction of the recording signal (b).

In the above embodiment, all the three means are provided for the first laser light irradiation after the change of the recording signal: means for controlling the laser light irradiation timing, means for controlling the laser light irradiation time, and means for controlling the laser light intensity. However, not limited to this,
Even if two means or one means are selected and operated, a sufficiently similar effect can be obtained depending on the characteristics of the recording medium, that is, the perpendicular magnetic film.

[Effects of the Invention] As described above, in a magnetic field modulation magneto-optical recording apparatus that modulates a magnetic field at a single frequency and irradiates a laser beam in a pulsed manner according to a recording signal, Means for changing the laser light irradiation timing with respect to the subsequent laser light irradiation with respect to the first laser light irradiation,
A means for changing the laser light irradiation time and a means for changing the laser light intensity are provided, and by operating the respective means, it is possible to control a change in the recording pit length by a difference in timing between a recording signal and a modulation magnetic field. In addition, the time change of the recording signal can be faithfully recorded as a change in the length of the recording pit length, that is, there is an effect that a reproduction signal which faithfully reproduces the temporal change of the recording signal can be obtained from the recording pit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a magneto-optical recording device of the present invention. FIG. 2 is a timing chart for explaining the operation of the magneto-optical recording method of the present invention. FIG. 3 is a configuration diagram of a conventional magneto-optical recording device. FIG. 4 is a timing chart for explaining the operation of the conventional magneto-optical recording method. 1: magneto-optical disk, 2: plastic substrate, 3: perpendicular magnetization film, 4: protective film, 5: semiconductor laser, 6: condenser lens, 7: actuator, 8: optical head, 9: coil, 10: electromagnet, 11: resonance type magnetic head driver, 12: laser power control circuit, 13: pulse width adjustment circuit, 14: phase adjustment circuit, 15:
Light modulation circuit, 16: oscillator, 17: condenser

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 11/10

Claims (2)

(57) [Claims] 1. A magneto-optical recording apparatus that performs recording by applying a light beam in a pulse shape in accordance with a recording signal and a period of the applied magnetic field while applying a magnetic field modulated at a constant period to a magneto-optical recording medium. In the above, after the change of the recording signal, the timing at the time of the first laser beam irradiation for recording the recording signal, and / or the irradiation time, and / or the irradiation intensity are changed with respect to other irradiation times after the change. A magneto-optical recording apparatus comprising: means for irradiating the recording signal differently to control a change in a recording pit length caused by the periodicity of the applied magnetic field when the recording signal changes. 2. The method according to claim 1, wherein the recording signal is changed to a recording signal corresponding to a longer recording pit length at the time of the first laser light irradiation, and at the time of another irradiation after the change.
The irradiation timing is delayed, and / or the irradiation time is shortened, and / or the irradiation intensity is reduced, and the recording signal is changed to a recording signal corresponding to a recording pit having a shorter recording pit length. At the time of the first laser light irradiation, the irradiation timing is advanced and / or the irradiation time is lengthened with respect to other irradiation times after the change,
2. The magneto-optical recording apparatus according to claim 1, further comprising means for increasing the irradiation intensity.