JP2528632B2 - Signal recorder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a signal recording device in an optical disc recording / reproducing device or the like for irradiating a recording medium such as an optical disc with a laser beam to record / reproduce a digital signal. is there.

(Prior Art) A signal recording device in a conventional optical disc recording / reproducing device is, for example, Nikkei Electronics, January 4, 1982, p88.
~ 112 "Optical Disk Memory Used for Image Files".

FIG. 5 is a block diagram of a signal recording device in this conventional optical disk recording / reproducing device, and FIG. 6 is an operation waveform diagram thereof. Reference numeral 1 is a laser drive circuit, 2 is a semiconductor laser, and 3 is a recording medium disk. Reference numeral 4 is a signal to be recorded, and 5 is a pit showing the state of the signal recorded on the recording medium.

In the signal recording apparatus of the conventional optical disk recording / reproducing apparatus configured as described above, the digital signal 4 to be recorded is input to the laser drive circuit 1 and the digital signal 4 is input.
The laser drive circuit 1 controls to increase the output power of the laser when the signal is at the H level and decrease the output power of the laser when the signal is at the L level. Since the laser light from the semiconductor laser 2 that has been subjected to this power control is focused and irradiated on the recording medium, the state of the recording medium changes as the temperature of the irradiation portion on the recording medium changes due to the power control. Then, recording is performed as signal pits as shown in FIG. 5 (FIG. 6).

(Problems to be Solved by the Invention) However, in the above-mentioned configuration, the recording pits spread in the track width direction as shown in FIG. 6 in the portion where the H level section of the digital signal 4 is long. There was a problem that mutual interference between them became large. Further, in recent years, there has been a demand for higher density in optical disc recording / reproducing apparatus, and a method for realizing this is disclosed in, for example, Japanese Patent Laid-Open No. 59-36338. There is a recording / reproducing method in which a groove having a V-shaped cross section in the radial direction is provided on an optical disk, and both slopes of the V-shaped groove are used as recording tracks, and the track pitch can be halved. In this case, the above problem is particularly likely to occur.

On the contrary, in the portion where the H level section of the digital signal 4 is short, the recording pit becomes thin, or when the material sensitivity is lower than the thermal energy of recording, a pit of a sufficient size cannot be formed and reproduction is performed. There was also a problem that sometimes caused an extreme drop in level.

In view of the above point, the present invention has an object to provide a signal recording apparatus capable of suppressing the spread of long recording pits and controlling the size of short recording pits in order to suppress mutual interference between tracks.

(Means for Solving Problems) The present invention generates means for generating a number of gate signals corresponding to the level inversion intervals appearing in a recording signal, and pulse trains whose crest value gradually decreases according to the gate signals. And a means for modulating the emission power of the laser according to the pulse train.

(Operation) The present invention forms a recording pit on a recording medium when a long recording pit is formed by recording a signal by laser-driving using a pulse train in which the crest value generated by the above-described configuration gradually decreases. The spread of heat due to the temperature rise in the area to be recorded is suppressed, and the recording pit is suppressed from expanding in the track width direction. When forming a short pit, the width of the recording pit is widened.

(Embodiment) FIG. 1 shows the configuration of a signal recording apparatus according to an embodiment of the present invention. In FIG. 1, 10 is a pulse width detection circuit that counts and detects the pulse width of a recording signal, 11 is a gate signal generation circuit that generates a gate signal from pulse width information, and 12 is a peak value using the gate signal. A recording pulse circuit that generates different pulse trains, 13 is a laser drive circuit that controls laser power by pulse trains, 14 is a semiconductor laser, and 15 is a disk of a recording medium.

The operation of the signal recording apparatus of this embodiment will be described below with reference to FIG.

As shown by the waveform 51 in FIG. 2, the recording signal is
Consider data modulated by a digital recording modulation method having a level inversion interval given in steps of 0.5T (T: bit period) from 1.5T to 4T. The pulse width detection circuit 10 inputs the data modulated as described above, counts the pulse width between H levels at intervals of 0.5T, and generates a gate signal as a result of which is 1.5T to 4T. Output to circuit 1. In the gate signal generation circuit 11, from the pulse width value,
A gate signal is output according to preset conditions. In the case of the present embodiment, from C ₁ shown in the waveform of 52 in FIG.
Outputs 8 kinds of gate signals C _8. Which gate signal is output from each pulse width value depends on the characteristics of the recording medium and the recording rate, etc.
It may be programmed in a memory element such as M (Reed Only Memory). Next, the recording pulse generation circuit 12 outputs a pulse train having different peak values from each gate signal as shown by the waveform 53, and the laser drive circuit 13 modulates the emission power of the laser 14 according to this pulse train, Irradiate laser light on. The temperature of the portion of the recording medium irradiated with the laser light rises, and the state of the recording medium in the portion where the temperature exceeds a certain threshold changes, whereby a signal recording pit is formed. At this time, since the power change of the laser beam changes according to the waveform 53, the width of the recording pit does not widen as shown by 54 even in the portion where the H level section of the recording signal is long. Further, in the short portion of the H level section, when the crest value is effectively increased, the width of the short pit becomes wide and the width of the long pit becomes almost equal to the width of the short pit.

This will be described below with reference to FIG. Now, when the power of the laser light changes like 55, the temperature change of the part where the center of the laser light beam on the recording medium passes is 56.
It is thought that it will be as shown in. If the alternate long and short dash line is the threshold value for changing the state of the recording medium, the state of the portion above this will change. Since the heat spread also exists two-dimensionally, when the two-dimensional temperature distribution on the recording medium is considered, the portion having a temperature equal to or higher than the threshold value is the region indicated by the diagonal line 57. It can be seen that the recording dots spread in the width direction. On the other hand, if the laser light has a short power change such as 58, from the same considerations as above, the temperature change of the part where the central part of the beam passes becomes like 59, and the recording pit looks like 60. Become. In this case, the widthwise extension of the recording pit is smaller than that of 57.

Next, when the power of the laser light changes as indicated by the pulse train indicated by 61, the temperature change at the center of the beam is
After the temperature rise by the leading pulse, the temperature drops,
Since the next pulse is applied, the falling is suppressed and the temperature rises, and then it starts to decrease again, and the next pulse causes the temperature to be suppressed and the temperature rises and decreases. Since this is not the temperature rise like the temperature change 56 when the applied pulse is 55, the two-dimensional temperature distribution on the recording medium is as shown by 62. As a result, the spread W in the recording pit width direction is smaller than 57. W can be changed by controlling the pulse width w and the peak value l. Therefore, as shown at 54 in FIG. 2 for explaining the embodiment of the present invention, the width of the recording pit is expanded in the width direction, but it is not widened even in the long H level period of the recording signal, and the H level period is not increased. The width of the pit can be widened and the width of the pit can be controlled to be substantially constant.

FIG. 4 shows an embodiment of the recording pulse generating circuit.
In FIG. 4, 20 is a constant voltage source, 21 to 28 are resistors having values of R _{1 to} R ₈ for controlling the pulse peak value, and 29 to 36.
Is a switch circuit which is turned on and off by the gate signals C _{1 to} C ₆ , 37 to 44 are input terminals of the gate signals C _{1 to} C ₈ , and 45 is an output terminal of the recording pulse train. The constant voltage source 20 supplies constant voltages to the resistors 21 to 28, respectively. By setting the resistance values R ₁ to R ₈ of the resistors 21 to 28, the switch 29
Attenuating the voltage input from 36 to 36. For example, when the gate signal C ₁ is input to the switch 29 from the gate signal input terminal 37, the output terminal 45 is output only during the pulse width w of the gate signal.
A pulse with a peak value attenuated by the value R ₁ of the resistor 21 is output at. Similarly, the switches 30, 31, ..., 36 are also gate signals C ₂ ,
The pulses controlled by C ₃ , ..., C ₈ are output. The pulse peak value can be changed by changing the resistors R ₁ , R ₂ , ..., R ₈ . As a result, the pulse train shown by the waveform 53 in FIG. 2 can be produced.

(Effects of the Invention) As described above, according to the present invention, when a long recording pit is formed, the spread of heat due to the temperature rise of the portion where the recording pit is formed on the recording medium is reduced, and the recording pit is tracked. It is possible to suppress the spread in the width direction and reduce mutual interference between tracks. In addition, it is possible to prevent the width of the recording pit from becoming narrow when forming a short recording pit, suppress the fluctuation of the pit width due to the pit length, and detect a signal with a stable amplitude during reproduction. In particular, in the case of the recording track having a narrow track pitch shown in the prior art, the effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal recording device according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the same embodiment, FIG. 3 is a diagram for explaining effects of the present invention, and FIG. 5 is a configuration diagram of an embodiment of a recording pulse generating circuit that is a constituent element of the invention, FIG.
FIG. 6 is a block diagram of a conventional optical disk recording device, and FIG. 6 is an operation waveform diagram thereof. 10 …… Pulse width detection circuit, 11 …… Gate signal generation circuit,
12 …… Record pulse generation circuit, 13 …… Laser drive circuit, 14
...... Laser, 15 …… Recording medium.

Claims (1)

(57) [Claims] 1. A means for generating a number of gate signals according to a level inversion interval appearing in a recording signal, a means for generating a pulse train whose peak value gradually decreases according to the gate signal, and a laser for a laser according to the pulse train. A signal recording device, comprising: means for modulating light emission power.