JPH076441A - Magneto-optical recording method - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide a mark modulation type magneto-optical recording method capable of accurately marking regardless of the difference in linear velocity between the inner and outer circumferences of the medium. [Structure] The recording laser power is initially set in a trial writing area. The preheat power 4 and the main pulse power 1 in the recording area are proportional to the square root of the ratio of the linear velocity in the trial writing area to the linear velocity in the area where data is actually recorded, with respect to their respective initial values. Set. The values of the second pulse powers 2 and 2'are set in the trial writing area and the initial value of the second pulse power set in the trial writing area with respect to the value of the main pulse power in the area where the data is actually recorded. The value is proportional to the ratio of the main pulse power to the initial value and is also proportional to the square root of the ratio of the linear velocity in the trial writing area to the linear velocity in the area where data is actually recorded. Recording is performed with the three-valued power and the bottom power 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark length modulation type magneto-optical recording method.

[0002]

2. Description of the Related Art As a recording method using a magneto-optical recording medium, an inter-mark modulation method and a mark length modulation method are known. Among them, the mark length modulation method is a recording method suitable for large capacity since it can improve the linear density as compared with the inter-mark modulation method because it reproduces by detecting edges of recorded marks and spaces. .

However, since the recording material used for the magneto-optical recording medium has a higher thermal conductivity than the recording material such as the dye or TeOx used as the recording material for the write-once type optical recording medium, it has a desired length. If you do not strictly control the recording laser power and pulse width so that the mark is formed,
There is a problem that the length of the actually formed mark becomes longer or shorter than the length of the mark to be originally recorded, and accurate mark length modulation recording cannot be performed.

As a second-generation magneto-optical recording method,
In addition to the mark length modulation method, the CAV method and the light modulation method are attracting attention from another viewpoint. In the magneto-optical recording method adopting such a method, a recording control technology for recording a mark shape preferable for the mark length modulation method and a test writing recording control technology for recording an accurate mark shape despite the fluctuation of the environmental temperature are electronic. IEICE Technical Report, M
R92-62, p13-18, proposed in November 1992.

The above recording control technique is a technique of dividing the recording laser pulse into a plurality of pulses and introducing preheat power / bottom power (heat cutoff period). When using a square wave pulse, when a long mark is recorded, the recording bit shape becomes a tear shape due to heat accumulation, the mark width becomes large at the rear edge, the position of the front edge easily changes, and the edge position varies depending on the pattern. There are problems such as changes. The above technique is intended to solve these problems by dividing a square wave pulse into a plurality of pulses of high power and short pulse, and by temperature balance by preheat power and bottom power.

On the other hand, the above-mentioned trial writing recording control technique, prior to the start of recording, in a particular trial writing area on the magneto-optical recording medium, a specific pattern consisting of, for example, a repeating pattern of the shortest mark length and a repeating pattern of the longest mark length. This is a technique of recording a signal with, detecting the amplitude of each repetitive pattern, and setting the recording power based on the detection result.
According to this technique, it is possible to control the mark shape corresponding to each environmental temperature.

[0007]

In the above prior art, once the power setting is performed, the set power is fixed over the entire surface of the magneto-optical recording medium. However, in the case of, for example, the CAV method, the linear velocity differs between the inner circumference and the outer circumference, and even if the power is set to an appropriate power in the test writing area on the inner circumference side, the linear speed is changed when recording on the outer circumference side. Since the speed becomes faster, heating is insufficient on the inner circumference side, and even if a signal having the same mark length is recorded, the actually formed marks have different shapes on the inner circumference side and the outer circumference side. Therefore, there is room for further improvement in order to perform highly reliable mark length modulation recording.

In view of the above problems of the prior art, the present invention provides a highly reliable mark length modulation type magneto-optical recording capable of forming an accurate mark regardless of the difference in linear velocity between the inner circumference and the outer circumference of the medium. The purpose is to provide a method.

[0009]

To achieve the above object, according to the present invention, in a magneto-optical recording method for irradiating a magneto-optical recording medium with laser light to perform mark length modulation recording, recording laser power is used. As at least the preheat power, the main pulse power, the second pulse power and the bottom power are used, and the recording laser power is initialized in the trial writing area, and further in the area where the data is actually recorded. Provides a magneto-optical recording method characterized by performing recording with power set so as to satisfy the following (A) to (C). (A) The value of the preheat power is the square root of the ratio of the linear velocity in the trial writing area to the initial value of the preheat power set in the trial writing area and the linear velocity in the area where data is actually recorded. (B) Set the value of the main pulse power to the linear velocity in the trial writing area and the line in the area for actually recording data with respect to the initial value of the main pulse power set in the trial writing area. (C) The value of the second pulse power is set to a value proportional to the square root of the ratio to the speed, with respect to the value of the main pulse power in the area where the data is actually recorded.
It is proportional to the ratio between the initial value of the second pulse power set in the trial writing area and the initial value of the main pulse power set in the trial writing area, and the linear velocity in the trial writing area and the actual data are recorded. The value is set to a value proportional to the square root of the ratio to the linear velocity in the region.According to the present invention, in the above, the bottom power is set to a value equal to or lower than the power of the laser beam at the time of reproduction, and is constant over the entire medium. A magneto-optical recording method is provided.

The method of the present invention will be described in detail below with reference to specific examples. 1A is a diagram showing an example of a recording laser waveform according to the present invention, FIG. 1B is a diagram showing another example,
(C) is a diagram showing recording marks formed by laser pulses having these waveforms. In these figures, 1 is the main pulse power, 2 and 2'is the second pulse power, 3
Is a bottom power, 4 is a preheat power, and 5 is a recording mark. Irradiation with the main pulse power 1 rapidly raises the recording temperature of the medium to form a mark of the shortest length, and irradiation with the second pulse power 2 forms a mark having a length corresponding to the mark length. The irradiation with the bottom power 3 is for removing the previous mark thermal interference, and the irradiation with the preheat power 4 balances the temperature decrease due to the bottom power 3 and keeps the medium temperature constant. It is for keeping. The second pulse power of 2 is composed of a number of high power and short pulses corresponding to the mark length, and the second pulse power of 2'is composed of one rectangular pulse having a length corresponding to the mark length. The shortest mark in the case of (1,7) RLL is formed by omitting the second pulse power.

In the present invention, for example, a signal of a specific pattern is recorded in a trial writing area at a predetermined position on the inner circumference side, the amplitude of the recording signal is detected, and the main pulse power, second pulse power, Set the initial values of bottom power and preheat power. As a method of setting the initial value in this case, the above-mentioned IEICE technical report,
The method described in MR92-62, p13-18, November 1992 may be used, or other methods may be used. Then, in the area where data is actually recorded, recording is performed so as to satisfy the following (A) to (C). (A) The value of the preheat power is the square root of the ratio of the linear velocity in the trial writing area to the initial value of the preheat power set in the trial writing area and the linear velocity in the area where data is actually recorded. (B) Set the value of the main pulse power to the linear velocity in the trial writing area and the line in the area for actually recording data with respect to the initial value of the main pulse power set in the trial writing area. (C) The value of the second pulse power is set to a value proportional to the square root of the ratio to the speed, with respect to the value of the main pulse power in the area where the data is actually recorded.
It is proportional to the ratio between the initial value of the second pulse power set in the trial writing area and the initial value of the main pulse power set in the trial writing area, and the linear velocity in the trial writing area and the actual data are recorded. Set to a value proportional to the square root of the ratio with the linear velocity in the area

Here, the reason why the above power setting is performed in the present invention will be described. Figure 2 shows a diameter of 130m
m polycarbonate substrate (track pitch 1.35μ
m) / SiNx (1000Å) / Tb ₇ Dy ₁₆ Fe ₆₉ Co
₈ (200Å) / SiNx (300Å) / Al (400
Å) / Using a magneto-optical recording medium having an ultraviolet curable resin (10 μm) structure, recording was performed under the conditions of a recording magnetic field of 250 Oe and DC light, and the width of the recorded mark was measured by a polarization microscope. is there. From the results of FIG. 2, FIG. 3 is a plot of the power recorded at a mark width of 1.2 μm against the linear velocity. As is clear from FIG. 3, the recording power is proportional to the square root of the linear velocity under the same thermal interference condition. Therefore, when the four-valued LD power is set so that accurate mark length recording can be performed, the thermal interference between marks is the same, and therefore the excess or deficiency of the LD power due to the difference in the linear velocities is the linear velocity of the recording power. It may be controlled so as to be proportional to the square root of.

Further, a repetitive pattern of 8T marks and spaces is recorded on the recording medium by the recording pulse waveform shown in FIG. 4, and the main pulse power and the second pulse power when the 8T marks and spaces are recorded with the correct length are shown. FIG. 5 shows a plot of the ratio of γ to linear velocity.
As is clear from FIG. 5, the ratio between the main pulse power and the second pulse power is found to be proportional to the square root of the linear velocity. Therefore, with respect to the initial value of the second pulse power set in the trial writing area, by setting a value proportional to the ratio of the linear velocity in the trial writing area and the linear velocity in the area for actually recording data, Despite the difference in linear velocity, the same thermal interference condition will be created for the second pulse power.

In the present invention, the heat interference condition is improved as compared with the prior art by adopting the above-mentioned setting conditions (A) to (C).

In the present invention, it is preferable that the bottom power is equal to or lower than the reproduction laser power and is constant over the entire surface of the medium. This has the advantage of simplifying control.

[0016]

EXAMPLES Examples of the present invention will be described below. Example SiNx (1000Å) / Tb ₇ was formed on a polycarbonate substrate (track pitch: 1.35 μm) having a diameter of 130 mm.
Dy ₁₆ Fe ₆₉ Co ₈ (200Å) / SiNx (300Å)
A magneto-optical recording medium having a structure in which each layer of / Al (400Å) / ultraviolet curable resin (10 μm) was provided was prepared. This magneto-optical recording medium was set in a magneto-optical recording / reproducing apparatus (laser wavelength used: 780 nm, NA 0.53), and the rotation speed was 30.
Optimum recording is performed by recording a random pattern under the conditions of (1,7) RLL and linear density of 0.57 μm (shortest mark length 0.76 μm) at a position of 00 rpm and R = 30 mm (trial writing area). Got power. Here, the optimum recording power is the power that can be recorded when the eyes of the reproduced waveform (eye pattern) are sufficiently opened and there is almost no waveform distortion (FIG. 6). The recording power (initial value) at that time was 2.5 mW of preheat power and 4.
The power was 4 mW, the second pulse power was 4.7 mW, and the bottom power was 1.5 mW. Next, when recording at the position of R = 45 mm, preheat power 2.5 mW × √ (45
/30)=3.0 mW, main pulse power 4.4 mW
× √ (45/30) = 5.3 mW, second pulse power 5.3 × (4.7 / 4.4) × √ (45/30) =
When recording was performed at 6.9 mW and a bottom power of 1.5 mW, similarly, the reproduced waveform was free from waveform distortion and correct recording could be performed. Similarly, when recording at the position of R = 60 mm, preheat power 2.5 mW × √60 / 30 =
3.5mW, main pulse power 4.4mW × √60 /
30 = 6.2 mW, second pulse power 6.2 ×
(4.7 / 4.4) × √ (60/30) = 9.3 mW,
When recording was performed with a bottom power of 1.5 mW, the reproduced waveform was similarly free from waveform distortion and correct recording could be performed. The pulse waveform shown in FIG. 1A was used as the recording laser pulse. Further, when a similar experiment was conducted with the recording laser pulse waveform shown in FIG. 1B, the same result as above was obtained.

[0017]

As described above in detail, according to the present invention, the above-mentioned configuration allows accurate mark length recording regardless of the difference in linear velocity between the inner and outer circumferences.

[Brief description of drawings]

1A is a diagram showing an example of a recording laser power according to the present invention, FIG. 1B is a diagram showing another example, and FIG. 1C is a diagram showing recording marks formed by laser pulses having these waveforms. Is.

FIG. 2 is a diagram showing a relationship between recording power and mark width.

FIG. 3 is a diagram showing a relationship between a linear velocity and a power required to record a mark having a width of 1.2 μm.

FIG. 4 is a diagram showing a recording pattern waveform.

FIG. 5 is a diagram showing a relationship between a ratio of a main pulse power and a second pulse power and a linear velocity.

FIG. 6 is a diagram showing a reproduced waveform when recording is performed with an optimum power.

[Explanation of symbols]

 1 Main pulse power 2, 2'Second pulse power 3 Bottom power 4 Preheat power 5 Recording mark

Claims (2)

[Claims] 1. A magneto-optical recording method for irradiating a magneto-optical recording medium with laser light to perform mark length modulation recording, wherein at least four levels of pre-heat power, main pulse power, second pulse power and bottom power are used as recording laser power. Power is used, and the recording laser power is initially set in the trial writing area. Further, in the area for actually recording data, the power is set so as to satisfy the following (A) to (C). A magneto-optical recording method characterized by recording. (A) The value of the preheat power is the square root of the ratio of the linear velocity in the trial writing area to the initial value of the preheat power set in the trial writing area and the linear velocity in the area where data is actually recorded. (B) Set the value of the main pulse power to the linear velocity in the trial writing area and the line in the area for actually recording data with respect to the initial value of the main pulse power set in the trial writing area. (C) The value of the second pulse power is set to a value proportional to the square root of the ratio to the speed, with respect to the value of the main pulse power in the area where the data is actually recorded.
It is proportional to the ratio between the initial value of the second pulse power set in the trial writing area and the initial value of the main pulse power set in the trial writing area, and the linear velocity in the trial writing area and the actual data are recorded. Set to a value proportional to the square root of the ratio with the linear velocity in the area 2. The magneto-optical recording method according to claim 1, wherein the bottom power is set to a value equal to or lower than the power of the laser light at the time of reproduction and is made constant over the entire surface of the medium.