JPH05205271A - Optical information recording method - Google Patents

Abstract

PURPOSE:To provide a new recording method in which only reproduction power level and recording power level are required at the time of recording. CONSTITUTION:A pulse beam having width X is radiated with recording power Pw during recording periods P1, P2, P3 for forming recording marks and a pulse beam having width Y (Y<X) is radiated with recording power Pw during erasing periods E1, E2. Consequently, overwrite can be realized while controlling only two power levels of recording power Pw and reproduction power Pr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording system and a recording apparatus for performing excellent recording on an optical recording member for optically recording information.

[0002]

2. Description of the Related Art A technique for recording / reproducing information by using a laser beam is already known, has been applied to a document file and a data file, and a system having a rewriting function is currently under development.

One of these methods is a so-called phase change type optical disk which utilizes reversible state change between amorphous and crystalline. The recording thin film used for this purpose has a high temperature portion (amorphous state) having a melting point of Tm or more and a temperature Tc (Tc <Tc) at which crystallization occurs at Tm or less due to laser light irradiation.
m) and a low temperature portion (crystalline state) are formed, and the above two states are reversibly changed. The amorphous state and the crystalline state have different complex refractive indices consisting of the refractive index n and the extinction coefficient k, and the difference in transmittance or reflectance that results from this is used to reproduce a signal.

In order to realize these, a reproducing power Pr, a recording power Pw and an erasing power Pe (Pw>Pe> Pr)
There is a method of irradiating a recording medium with laser light modulated between the three power levels (Japanese Patent Application Laid-Open No. 56-145536).

This method is shown in FIG. FIG. 7B is an explanatory diagram showing the state of the recording medium after irradiation. Figure 7 (b)
In, the regions 71, 72, 73 surrounded by the solid line are heated to a temperature equal to or higher than the melting point and are in an amorphous state regardless of the previous state. The region surrounded by the dotted line outside the solid line is heated above the temperature at which crystallization occurs and is crystallized regardless of the previous state. As described above, the portions irradiated with the recording power Pw are amorphous recording marks 71, 7
2, 73 are formed, and the portion irradiated with the erasing power Pe becomes a crystalline state. In this way, it is possible to overwrite the old information while rewriting it with new information.

FIG. 8 shows a block diagram of a laser drive circuit for realizing this conventional recording method. In FIG. 8, 81
Is a current source for passing a current I1. Reference numeral 82 is a current source for passing the current I2. Reference numeral 83 is a current source for flowing the current I3. 8
Reference numeral 4 denotes a switch, which is turned on when the input signal ERGT (86) is at H level and is turned off when at L level. A switch 85 is turned on when the input signal WTDT (87) is at the H level.
Then, it turns off at the L level. Reference numeral 88 denotes a semiconductor laser, which emits light with a reproducing power Pr when a current I1 flows and emits light with an erasing power Pe when a current I1 + I2 flows, and a current I
When 1 + I2 + I3 flows, light is emitted with the recording power Pw.

Next, the operation of the drive circuit of FIG. 8 will be described with reference to the timing chart of FIG. ERG until time t91
Since T (86) is at L level, the switch 84 is OFF, and since WTGT (87) is at L level, the switch 85 is also OFF. Therefore, the current I1 flows through the laser 88, and the laser 88 emits light with the reproduction power Pr. From time t91 to t92
Until, ERGT (86) is at H level, so switch 8
4 is ON, and WTGT (87) is at L level, so the switch 85 is OFF. Therefore, the current I1 + I2 flows through the laser 88, and the laser 88 emits light with the erase power Pe. From time t92 to t93, the switch 84 is ON because the ERGT (86) is at the H level, and the switch 85 is also 0N because the WTGT (87) is at the H level. Therefore, the current I1 + I2 + I3 flows through the laser 88 and emits light with the recording power Pw. Thus, as shown in FIG. 9D, the laser emits light and the conventional recording method can be realized.

[0008]

However, in the above-mentioned conventional recording method, the reproducing power Pr, the erasing power Pe,
It is necessary to control the laser power to three laser power levels of the recording power Pw, and as shown in FIG. 8, the laser drive circuit requires 81, 82, and 83 and three current sources. There was a problem that the circuit became complicated.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a recording method and apparatus capable of making the power level at the time of recording only the reproduction power and the recording power.

[0010]

In order to achieve this object, the present invention irradiates a recording power having a constant pulse width in the recording period for forming a recording mark, and the recording period in the signal erasing period. The recording method is characterized by irradiating the same recording power with a pulse width narrower than the pulse width.

[0011]

With this configuration, at the time of recording, it is sufficient to control the laser power to the two laser power levels of the reproducing power and the recording power, and the laser driving circuit becomes simpler.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a waveform diagram of the irradiation laser power of the recording method of the present invention. In the recording periods P1, P2, and P3 for forming the recording mark, the width X with the recording power Pw.
Is emitted. In the erasing periods E1 and E2, the pulsed light having the recording power Pw and the width Y (Y <X) is continuously emitted in the cycle Z. The conditions of X, Y and Z will be described later.

FIG. 1B is an explanatory diagram showing the state of the recording medium after irradiation. In the recording periods P1, P2, and P3, regions 1, 2, and 3 (regions surrounded by a solid line) that are in an amorphous state regardless of the previous state are formed by increasing the temperature above the melting point Tm. Is the recording mark.

Since the pulse width is narrow in the erasing periods E1 and E2, the temperature does not rise above the melting point Tm and there is no amorphous region. However, there are regions 4 and 5 in which the temperature rises above the temperature Tc at which crystallization occurs and becomes a crystalline state regardless of the previous state. As will be described later, the widths of the areas 4 and 5 are set larger than the widths of the recording marks 1, 2, and 3, and overwriting is possible.

Next, how to select the pulse widths X, Y and Z will be described with reference to FIG. As shown in FIG. 2A, it is assumed that the laser power having the pulse width W is irradiated with the recording power Pw. The state of the recording medium at that time is shown in FIG.
A region 21 surrounded by a solid line is heated to a temperature equal to or higher than the melting point by the recording power Pw and becomes an amorphous state, that is, a recording mark regardless of the previous state. A region 22 from the outside of the solid line to the dotted line is heated to some extent and becomes a crystalline state regardless of the previous state. Since the laser beam is moving in the X direction, the regions 21 and 22 have an elliptical shape that is long in the traveling direction (X direction). Here, the length in the X direction of the amorphous region 21 is Wmx, and the length in the Y direction is Wmy.
The length of the crystal region 22 in the X direction is Wex, and the length in the Y direction is Wey.

FIG. 2C shows Wmx, Wmy, Wex, and Wey when the recording pulse width W is changed with the recording power Pw.
The graph of change of is shown. When the pulse width is W1 or less, the medium does not change. Crystallization begins to occur when the pulse width is W1 or more. Since the temperature at which crystallization occurs is lower than the melting point, crystallization thus starts at a lower energy than crystallization, that is, at a smaller pulse width. After that, Wex and Wey increase. Amorphization begins to occur when the pulse width is W2 (W2> W1) or more, and Wmx and Wmy increase from there.

From FIG. 2C, when the pulse width for forming the recording mark is X, Wmy = Wmy1. In order to erase this recording mark by the erase pulse having the pulse width Y, Wey> Wmy1 needs to be satisfied. Therefore,
If the erase pulse width for Wey = Wmy1 is Ymin, Y> Ymin may be selected. Further, since the recording mark (amorphous region) is not formed by the erase pulse, the erase pulse width Y may be selected so that Y <W2. In summary, the erase pulse width Y satisfying Ymin <Y <W2 may be selected.

Next, the condition of the period Z of the erase pulse is shown in FIG.
Described in. FIG. 10A shows an optical waveform when two erase pulses having a width Y and a period Z are irradiated. FIG. 10B is an explanatory diagram showing the state of the recording medium after irradiation. Each crystal region has an ellipse whose major axis is Wex1 and whose minor axis is Wey1. Considering the overlapping, the crystal region width (Y direction) is the smallest at Z / 2 from the erase pulse center.
It has just come off, and its length Wz is

[0020]

[Equation 1]

It can be expressed as follows. Therefore,
Z satisfying the condition shown in (Equation 2) may be selected so that Wz becomes larger than the recording mark width Wmy1.

[0022]

[Equation 2]

Next, FIG. 3 shows a block diagram of a circuit capable of controlling the laser power as shown in FIG.

In FIG. 3, reference numeral 31 is a current source for passing a current I1. Reference numeral 32 is a current source for flowing the current I4. A switch 33 is turned on when the input signal WTDT (34) is at the H level and turned off when it is at the L level. Reference numeral 35 denotes a semiconductor laser, which emits light with reproduction power Pr when a current I1 flows,
When the current I1 + I4 flows, it emits light with the recording power Pw.

Next, the operation of the drive circuit of FIG. 3 will be described with reference to the timing chart of FIG. WTD as shown in Figure 4 (a)
The T signal (34) is given. When the WTDT signal is at the L level, the switch 33 is OFF, the current I1 flows through the laser 35, and the laser 35 emits light with the reproduction power Pr. WTD
When the T signal (34) is at the H level, the switch 33 is O
N, the current I1 + I4 flows through the laser 35, and the laser 35 emits light with the recording power Pr. Thus, as shown in FIG. 4C, the laser emits light and the recording method of the present invention can be realized.

At this time, in the block diagram of FIG. 3, there are only two current sources 31, 32, and the laser drive circuit becomes simple.

Further, FIG. 5 shows a more specific configuration diagram of a laser drive circuit for realizing the recording method of the present invention.

In FIG. 5, reference numeral 51 is a reproduction reference voltage generating circuit for generating a reference voltage Vr. Reference numeral 52 is a recording reference voltage generating circuit, which generates a reference voltage Vw. Reference numeral 53 denotes a transistor, which causes a current I1 corresponding to the reference voltage Vr to flow.
Reference numeral 54 denotes a transistor which allows a current I4 corresponding to the reference voltage Vw to flow. A semiconductor laser 55 emits light with a reproducing power Pr when a current I1 flows, and emits light with a recording power Pw when a current I1 + I4 flows. 56 and 57 are transistors. Reference numeral 58 is an inverting circuit. Reference numeral 59 is an OR circuit. An erase pulse generation circuit 60 outputs a signal having a cycle Z and a pulse width Y when the WTGT signal 62 is at H level, and outputs an L level when the WTGT signal 62 is at L level. Reference numeral 61 is a recording data signal WTDT, and 62 is a recording gate signal WTGT.

The operation of the laser drive circuit configured as described above will be described with reference to the timing chart of FIG. FIG. 6A shows the recording data signal WTDT (6
1) and the pulse width is X. (B) is the recording gate signal WTGT (62), which becomes H level during recording. (C) is the output of the erase pulse generation circuit,
A pulse signal having a cycle Z and a pulse width Y is generated only while the T signal is at the H level. The OR circuit 59 has (a) and (c)
Is output and a waveform as shown in (d) is output. O
When the output (d) of the R circuit 59 is at the L level, the transistor 56 is turned on and the transistor 57 is turned off, so that the current I1 flows through the semiconductor laser 55 and light is emitted at the reproduction power Pr. When the output (d) of the OR circuit 59 is at the H level, the transistor 56 is turned off and the transistor 57 is turned on, so that the semiconductor laser 55 receives the current I1 +.
I4 flows and emits light with the recording power Pw. Therefore, the current flowing through the semiconductor laser 55 is as shown in (e), and the light emission waveform is as shown in (f). In this way, the recording method of the present invention can be realized.

As described above, according to this embodiment, the recording power having a constant pulse width is applied during the recording period for forming the recording mark, and the pulse width during the signal erasing period is more than the pulse width during the recording period. By irradiating the recording power with a narrow pulse width, it has conventionally been necessary to control the power to three power levels of reproducing power, erasing power and recording power, whereas two power levels of reproducing power and recording power are required. I just need to control the power,
The laser drive circuit can be simplified.

Up to this point, the phase change material utilizing the change between the amorphous and the crystal has been described, but it is also effective for the material which is rewritten by the laser light modulation, for example, the magneto-optical material having the multilayer film structure. Needless to say.

[0032]

As described above, according to the present invention, a recording power having a constant pulse width is applied during a recording period for forming a recording mark, and a pulse narrower than the pulse width during the recording period is applied during a signal erasing period. By irradiating the same recording power in the width, it is sufficient to control the power to only two power levels of the reproducing power and the recording power, and the laser driving circuit can be simplified.

[Brief description of drawings]

FIG. 1A is a waveform diagram showing an irradiation laser power of an optical recording method of the present invention, and FIG. 1B is an explanatory diagram showing a state of a recording medium after laser irradiation.

2A is a waveform diagram showing an example of irradiation laser power, FIG. 2B is an explanatory diagram showing a state of a recording medium after laser irradiation, and FIG. 2C is a pulse width of irradiation laser power and an amorphous region to be formed. , Relationship diagram with the size of crystal region

FIG. 3 is a block diagram of a laser drive circuit for realizing the optical recording method of the present invention.

FIG. 4 is a timing chart for realizing the optical recording method of the present invention.

FIG. 5 is a laser drive circuit diagram for realizing the optical recording method of the present invention.

FIG. 6 is a timing chart for realizing the optical recording method of the present invention.

7A is a waveform diagram showing irradiation laser power of a conventional optical recording method, and FIG. 7B is an explanatory diagram showing a state of a recording medium after laser irradiation.

FIG. 8 is a block diagram of a laser drive circuit for realizing a conventional optical recording method.

FIG. 9 is a timing chart for realizing a conventional optical recording method.

FIG. 10A is a waveform diagram showing an example of irradiation laser power, and FIG. 10B is an explanatory diagram showing a state of a recording medium after laser irradiation.

[Explanation of symbols]

 31 current source 32 current source 33 switch 35 semiconductor laser 55 semiconductor laser

Claims (3)

[Claims] 1. A method of recording a signal on an optical information recording member having two or more optically identifiable states, wherein a pulse is emitted to form a recording mark during a signal erasing period. A method of recording optical information, characterized in that pulsed light having a narrower width with the same power as light is emitted. 2. The width of the pulsed light during the signal erasing period is such that when the pulsed light is irradiated with the same power as the pulsed light for forming the recording mark, the recording mark cannot be formed. The method for recording optical information according to claim 1, wherein the optical information is recorded. 3. A first current source for supplying a current sufficient for the semiconductor laser to emit light at a reproducing power, and a current for allowing the semiconductor laser to emit light at a recording power together with the current of the first current source. A second current source and a signal generator that generates a pulse having a constant width in a recording period for forming a recording mark and generates a pulse having a width narrower than the pulse width in the recording period in a signal erasing period. When there is no pulse from the signal generating section, only the current from the first current source flows into the semiconductor laser, and when there is a pulse from the signal generating section, the current from the first current source is A laser drive circuit, characterized in that a current and a current from the second current source are combined to flow into the semiconductor laser.