JPS628371A - Signal recording device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a signal recording device in an optical disk recording and reproducing device, etc., which records and reproduces digital signals by irradiating a recording medium such as an optical disk with a laser beam. It is.

(Prior Art) A signal recording device in a conventional optical disk recording/reproducing device is described, for example, in the Nikkei Electronics January 4, 1982 issue, p.
88-112 "Optical disk memory started to be used for image files".

FIG. 5 is a block diagram of a signal recording device in this conventional optical disk recording and reproducing apparatus, and FIG. 6 is an operational waveform diagram thereof.

1 is a laser drive circuit, 2 is a semiconductor laser, and 3 is a recording medium disk. 4 is a signal to be recorded, and 5 is a pit indicating the state of the signal recorded on the recording medium.

In the signal recording device of the conventional optical disk recording and reproducing device configured as described above, the digital signal 4 to be recorded is input to the laser drive circuit 1, and when the digital signal 4 is at H level, the output power of the laser is controlled. The laser drive circuit 1 performs control to lower the output power of the laser when it is at the L level.

The laser light from the semiconductor laser 2 that has undergone this power control is focused and irradiated onto the recording medium, so the state of the recording medium changes as the temperature of the irradiated area on the recording medium changes due to the power control. Then, recording is performed as signal pits as shown in 5 (FIG. 6).

(Problem to be Solved by the Invention) However, in the above configuration, the recording pits spread in the track width direction in the long H level section of the digital signal 4 as shown in FIG. There was a problem of increased mutual interference between the two. Also,
In recent years, there has been a desire for higher density in optical disk recording and reproducing apparatuses, and a method for achieving this is shown in, for example, Japanese Patent Laid-Open No. 59-36338. There is a recording and reproducing method in which a groove whose radial cross section is V-shaped is provided on an optical disk, and both slopes of the V-shaped groove are used as recording tracks, thereby halving the track pitch.

In this case, the above problem is particularly likely to occur.

On the other hand, if the recorded pits are narrow in the part where the H level section of digital signal 4 is short, or if the material sensitivity is low compared to the thermal energy of recording, it may not be possible to form pits of sufficient size and the reproduction There was also the problem that it sometimes caused an extreme drop in the level.

In view of this, an object of the present invention is to provide a signal recording device that can suppress the spread of long recording pits and control the size of short recording pits in order to suppress mutual interference between tracks.

(Means for Solving the Problems) The present invention provides an optical system comprising means for generating a gate signal according to a level inversion interval appearing in a recording signal, and means for generating a pulse train having different peak values according to the gate signal. It is a disk recording device.

(Function) The present invention uses pulse trains of different peak values generated by the above-described configuration to drive a laser and record a signal to form a long recording pit on a recording medium. This reduces the spread of heat due to temperature rise, and suppresses the spread of recording pits in the track width direction. Furthermore, when forming short pits, the width of the recording pits is made wider.

(Embodiment) FIG. 1 shows the configuration of a signal recording device in 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 gate signal that uses gate signals to generate different peak values. A recording pulse circuit that generates a pulse train, 13 a laser drive circuit that controls the power of the laser by the pulse train, 14 a semiconductor laser, and 15 a disk as a recording medium.

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

As shown in the waveform 51 in FIG. 2, the recording signal is as follows:
Consider data modulated by a digital recording modulation method having a level inversion interval given in steps of 0.5T (T: pit period) from 1.5T to 4T. The pulse width detection circuit 10 inputs the data modulated as described above,
The pulse width between H levels is counted in 0.5T increments, and the result indicating which one is between 1.5T and 4T is output to the gate signal generation circuit 11. Gate signal generation circuit 1
1, a gate signal is output based on the pulse width value and according to preset conditions. In the case of this embodiment, eight types of gate signals C1 to C1 shown in waveforms 52 in FIG. 2 are output. The gate signal to be output from each pulse width value varies depending on the characteristics of the recording medium, the recording rate, etc., so it must be determined experimentally in advance and stored in the ROM (Reed 0
The program may be programmed into any memory element, such as nly memory). Next, in the recording pulse generation circuit 12, 5
As shown in the waveform of 3, a pulse train with different peak values is output from each gate signal, and the laser drive circuit 13 modulates the emission power of the laser 14 according to this pulse train, and the recording medium 1
A laser beam is irradiated onto 5. The temperature of the portion of the recording medium irradiated with the laser beam increases, and the state of the recording medium changes in the portion where the temperature exceeds a certain threshold value, thereby forming signal recording pits. At this time, the power of the laser beam changes according to the waveform 53, so
Even in a portion where the H level section of the recording signal is long, the width of the recording pit does not widen as shown at 54. Also, H
In the short part of the level, when the wave height value is effectively increased, the width of the short pit becomes wider, and the width of the long pit and the short pit become almost equal.

This will be explained below using FIG. Now, if the power of the laser beam changes as shown in 55, the temperature change of the part of the recording medium through which the center of the laser beam passes is 55.
It is thought that the situation will be as shown in 6. If the one-dot chain line is a threshold value at which the state of the recording medium changes, the state above this threshold changes. Since the spread of heat also exists two-dimensionally, when considering the two-dimensional temperature distribution on the recording medium, the portion where the temperature is higher than the threshold value is the area indicated by diagonal lines 57. It can be seen that the recording pits are expanding in the width direction. On the other hand, if the power of the laser beam changes over a short period of time as shown in 58, from the same consideration as above, the temperature change in the area where the center of the beam passes will be as shown in 59, and the recording pit will be as shown in 60. Become.

In this case, the spread of the recording pit in the width direction is smaller than that in 57.

Next, when the power of the laser beam changes as shown in the pulse train shown at 61, the temperature change at the center of the beam is
After the temperature rise due to the first pulse, the temperature decreases, but
As the next pulse is applied, the temperature changes such that the drop is suppressed and the temperature rises, the temperature changes again to fall, and the next pulse suppresses the fall and the temperature changes to rise and fall. Since this is not a temperature rise like the temperature change 56 when the applied pulse is 55, the two-dimensional temperature distribution on the recording medium becomes as shown at 62. As a result, the width W of the recording pit in the width direction is 5
It is smaller than 7. W can be changed by controlling the pulse width W and peak value Q. Therefore, as shown at 54 in FIG. 2, which explains the present invention in detail, the spread of the recording pit in the width direction does not widen even in the long part of the H level period of the recording signal, and The short portions can be made wider, making it possible to control the width of the pit to be approximately constant.

Further, FIG. 4 shows an embodiment of the recording pulse generation circuit. In FIG. 4, 20 is a constant voltage source, 21 to 28 are resistors having values of R□ to R, for controlling the peak value of the pulse;
29 to 36 are 0N-OF by gate signals C~C6
F switch circuit, 37 to 44 are gate signals C□
-C, and 45 are output terminals for the recording pulse train. Constant voltages are supplied from a constant voltage source 20 to resistors 21 to 28, respectively. By setting the resistance values R to R of resistors 21 to 28, switches 29 to 3
6 is attenuated. For example, when the gate signal C is input to the switch 29 from the gate signal input terminal 37, a pulse having a peak value attenuated by the value R1 of the resistor 21 is output to the output terminal 45 only during the pulse width W of the gate signal. Similarly, switch 30゜3],...
, 36 also have pulse peak values controlled by gate signals C21C31..., C1l. Pulse wave height value is resistance L+R
21... Can be varied by changing lR11. As a result, a pulse train shown in the waveform 53 in FIG. 2 can be created.

(Effects of the Invention) As explained above, according to the present invention, when forming long recording pits, the spread of heat due to the temperature rise in the portion of the recording medium where the recording pits are formed is reduced, and the recording pits are aligned with the track. It is possible to suppress the spread in the width direction, and it is possible to reduce mutual interference between tracks. Further, when forming short recording pits, it is possible to suppress the width of the recording pits from becoming narrower, and it is possible to suppress fluctuations in the width of the pits due to the pit length, so that a signal with a stable amplitude can be detected during reproduction. This effect is particularly great for recording tracks with a narrow track pitch as shown in the prior art.

[Brief explanation 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 the present invention in detail, and FIG. 4 is a diagram of this embodiment. A configuration diagram of an embodiment of a recording pulse generation circuit which is a component of the invention, No. 5
The figure is a block diagram of a conventional optical disc recording device, and FIG. 6 is its operating waveform diagram. 10... Pulse width detection circuit, 11... Gate signal generation circuit, 12... Recording pulse generation circuit, 13...
Laser drive circuit, 14... Laser, 15... Recording medium. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 54
Figure 3

Claims (1)

[Claims] A signal recording device comprising: means for generating a gate signal according to a level inversion interval appearing in a recording signal; and means for generating a pulse train having a different peak value according to the gate signal.