JPS60243824A - Signal recording method of optical disk - Google Patents

Abstract

PURPOSE:To correctly read out data bits with an optical disk device, in which the time interval between data bits ''1'' and ''1'' irregularly changes, by specifying the irradiating time of an optical beam. CONSTITUTION:Data bits ''0'' are irregularly inserted between data bits ''1'' and ''1'' and a pulse interval variable circuit 9 makes control so that the recording waveform can always have a duty factor 50% at the time of insertion. That is to say, the light emission of a laser 11 is started at the rise of the data bit ''1'' and a ''0'' continuity discriminating circuit 8 discriminates the cycle up to the rise of the next data ''1'', and then, the light emission is stopped after the time of a half cycle has passed. When using such bits, the ratio of the area of a pit (d) to the area (e) where no pit (d) is formed becomes 1:1. Since the pit (d) is largely formed at the section where the data bit ''0'' is inserted in a plural number, the waveform (3) of a readout signal is saturated. Therefore, a Vp.p level (a) can be detected and decision of a 1/2-Vp.p level (b) also becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a signal recording method for an optical disc in which data is recorded as binary data bits "1" and "0" by irradiating a light beam. The present invention relates to a signal recording method for an optical disc in which the irradiation time of the light beam is set to 1/2 of the time interval between the data bit "1" and the data bit "1".

(b) Background of the technology To record data on the optical disk surface of an optical disk device, which is expected to be used as a large-capacity external storage device, laser light is turned into a light beam and irradiated onto the optical disk surface.
bit). (2) Form a bubble. (3) A recording method such as changing the reflectance is used.

When data formed in this manner is read, the read waveform is the digital data itself whose waveform change point corresponds to data bit "1".

However, the changing points of the waveform read out from the changing points irradiated with the light beam show waveform changes depending on the light intensity, and when the read waveform is encoded, it may be reproduced as unstable data.

In order to use optical discs as large-capacity external storage devices with higher reliability, there has been a strong desire to put into practical use optical disc devices that eliminate the above-mentioned instability.

(C) Prior Art and Problems Next, a conventional signal recording method in an optical disk device will be explained with reference to the drawings.

Figure 1 is a block diagram of the optical disk device stack/write system, Figure 2 is a readout waveform diagram, Figure 3 is an example of recording using a short hole (focus), and Figure 4 is a diagram of the readout situation of data with a predetermined period. (A) shows a case where the signal level is saturated even in the in-focus area, and (B) shows a case in which the signal level has not reached the saturation level in the in-focus area.

In the figure, ■ is write data, ■ is read data, and ■
is a series of signal waveforms, ■ is 80 (AC) ground level,
■ is DC (direct current) ground level, ■.

■' is the saturation level, and a is the level of the read signal waveform ■ (however, it is the level from the peak point to the peak point).

(hereinafter expressed as p, p), b is the level of the 1/2 successive signal waveform ■, and C is the level 5 of the 1/2 readout signal waveform ■.
The width of the point, d is the bit, e is the sensitive material part, f is the substrate, Δt~Δ
t" is the time shift width, and (11, <11.' indicates the bit pattern data, respectively. Also, the solid arrow line and the dotted arrow line between the light emitting section 3 and the optical disk 1 indicate the incident light and the reflected light beam, respectively.

Figure 1 shows an optical disk 1 that stores data at a focus created by irradiating a light beam, and a light receiving section 5 that uses the light emitted by the light emitting section 3 to turn it into a light beam and irradiates it onto the optical disk 1 and focuses the reflected light. 2. A light-emitting section 3. A light-emitting section that emits data recording light according to the electric signal output from the light circuit 4. A light circuit that amplifies the write data to a certain level and outputs it to the light-emitting section 3. 4゜A light receiving section 5゜ inputs the reflected optical signal from the optical head 2 and outputs it as an electric signal.The output signal of the light receiving section 5 is kept constant and amplified to a level and output as read data. ing.

Since the intensity of the light beam irradiated onto the surface of the optical disk has a substantially Gaussian distribution, the change point of the read signal waveform (2) shows a waveform change depending on the light intensity.

Therefore, as a signal encoding method, the data bit “′l
If we do not use an Oc-free code in which the integral of the number of `` and 0゛' is constant, the C ground level ■ becomes the 4nth (A)
Changes as shown in (shown by dotted lines).

Therefore, accurate data change points cannot be detected.

However, the DC free code signal encoding method is
Generally, redundant bits are required, making it difficult to increase the recording density, and the encoding circuit becomes complicated. On the other hand,
Recording methods that increase recording density (for example, 2-7.1-
7 encoding system), a long continuous pattern of 0 bits occurred, and in this case, unless [1C free coat was used, the AC ground level ■ would fluctuate and accurate data could not be detected. .

On the other hand, methods for recording bits on one surface of an optical disc are roughly divided into two methods. That is.

One is a short hole recording method that creates a focus every time data bit “1” rises in the write data (this is focus pattern data created with NRZ1), and the other is a short hole recording method that creates a focus every time the data bit “1” rises. This is a long hole recording method in which focusing starts at the rising edge of "1" and ends at the falling edge of the secondary data bit "1".

In this example, a digital signal recording method using a junior college recording method will be explained.

As a digital signal recording method using the junior college recording method, as shown in FIG. Form and go.

That is, in the area irradiated with the light beam, the sensitive material e evaporates as shown in FIG. 2, resulting in a bit d corresponding to the information. When information is read by irradiating a light beam onto this bit d portion and detecting the amount of reflection, a readout signal waveform (2) shown in FIG. 2 is obtained.

This readout signal waveform (2) has a shape similar to a Gaussian distribution, and this is because the intensity distribution of the light beam irradiated onto one surface of the optical disk has a Gaussian distribution.

Further, the read signal waveform (■) above corresponds to data bit "1", and the width of the information waveform of data bit "1" is approximately the voltage level (Vp, p level a) of the continuous signal waveform (■).
This corresponds to the signal width C at 1/2 of the value.

Also, since the read signal waveform (2) voltage corresponds to the amount of light reflected on one surface of the optical disk, it becomes a waveform containing a DC (direct current) component as shown in FIG. FIG. 3 shows an example of bit pattern data (1)' which includes three data bits "0" between data bits "1" and "1" in the junior college recording method.

In this case, the AC ground level (■) of the signal waveform and the 1/2 Vp, p level b of the successive signal waveform (2) have different values.

Furthermore, in the case of bit pattern data (1) having various data periods as shown in Fig. 4,
is bit pattern data (changes at 11 change points, 1/
2Vp, Δ for the signal pulse obtained from p level b
This results in a time lag between t and ΔL, resulting in a signal detection error.Therefore, there is a problem in using the AC ground level ■ as the information detection point.

On the other hand, as shown in Figure 4 (A), the readout signal waveform ■ is at focus 6.
part (bit pattern data (11 data bits "'1
If the part corresponding to ゛) is also saturated, no information is detected at
If information is detected at , there is no need to worry about the time lag between Δt and Δt IT.

However, as shown in Fig. 4(B), if the saturation level ■-■' is not reached at the pitch d part (for example, when the bit density is increased), 1/2Vp and p level b are determined. Even in this case, if an attempt is made to detect a signal at the AC ground level (2), a time lag between ΔL and Δt will become a problem.

This shows that even with the conventional DC-free code, similar problems will occur if junior college records are used, and it means that there is a need to make the junior college records DC-free.

(d) Purpose of the Invention The object of the present invention is to provide a novel signal recording method for an optical disc that solves the above-mentioned problems.

Particularly when performing short-length recording on the surface of an optical disk, the object of the present invention is to eliminate problems caused by fluctuations in the AC ground level of a read waveform and to realize a signal recording method for an optical disk that can accurately read bit data.

(e) Structure of the Invention The present invention records data on the surface of an optical disk by irradiating a light beam, thereby recording data in the form of binary data,
This is a device that records as "O", and the data bisob 1
In an optical disk device using an encoding method in which the time interval between "1" and "B" changes irregularly, the irradiation time of the light beam is set to 1/1/2 of the time interval between the data bits "1" and "1". 2, this can be achieved by an optical disk signal recording method characterized in that it becomes possible to read out the data bits accurately.

(f) Examples of the invention The gist of the present invention will be specifically explained below with reference to the drawings.

FIG. 5 shows an embodiment of the signal recording section of the optical disk device according to the present invention, FIG. 6 shows an example of signal recording according to the present invention, and FIG.
/7 encoding tables are shown respectively.

The same symbols indicate the same objects or contents throughout the drawings.
(2) shows a recording waveform, (3) shows a bit pattern on the optical disk surface, (4) shows a read waveform, and (5) shows pattern data obtained by encoding bit pattern data (1,) by 2/7.

The present embodiment shown in FIG. 5 includes a laser power amplifier 10 degrees, a light emitting section 3 degrees consisting of a laser 11, an encoder 7. O” continuous discrimination circuit 8. Pulse interval variable circuit 9
A write circuit consisting of 4° NRZ data write data ■ is code-converted (for example.

2/7 code) Data bits of the code data converted by the encoder 7
Determine the number of consecutive O” ゛O″i! ! 8° pulse interval variable circuit that controls the width of the recording pulse converted by the encoder 7 so that the duty factor becomes 50% 9° laser power that controls the light emission of the laser 11 by the output signal of the pulse interval variable circuit 9 It consists of an amplifier 10° and a laser 11° that emits writing/reading laser light.

Next, the operation of this embodiment will be explained. In this example, DC
In the free code, a signal that does not use the DC free code signal encoding method is input as write data (2).

When the write data ■ is not a DC free code, a data bit "P0" is inserted irregularly between the data bits "1" and "1". Therefore, the recording waveform for such digital data is As shown in (2) of FIG. 6, the pulse interval variable circuit 9 is controlled so that the duty factor is always 50%.

The method of realizing a pulse with a duty factor of 50% is to start emitting light from the laser 11 at the rising edge of the data focus "l" and start emitting light from the laser 11 at the rising edge of the secondary data bit "1", that is, the cycle of the data bit "0". This is realized by discriminating the number by a "0" continuation discriminating circuit 8 and stopping the emission of the laser 11 at half the period of the data bits "'1" and "1".

Bit d, which is always formed by a recording waveform with such a duty factor of 50%, has the area of the area of bit d and the area e where bit d is not formed, as shown in (3) in Figure 6. The ratio will be 1:1.

The readout signal waveform (■) when reading out the pits ld at this time is as shown in (4) in Figure 6, where the pits ld are large in the part where multiple data pits 0'' are inserted. Therefore, the read signal waveform (2) is saturated, and therefore the ship p, p level a can be detected, and is 1/2Vp.

It also becomes possible to determine the p level b.

In addition, when this successive signal waveform ■ is subjected to ^C (alternating current) coupling, even if the signal has not reached the saturation level ■-■', the positive and negative areas of the readout waveform will be the same. The ground level ■ and 1/2vp, p level b are the same.

This means that even if a signal is detected at ground level (2), a detection error due to the time lag of Δt to Δt I+ will not occur as shown in FIG. 4 (8).

The signal recording method according to the present embodiment described above is an encoding method in which one or more data bits "0" are inserted between data bits "1" and "'1" in order to increase the recording density. It is valid.

In particular, in the 2/7 encoding system (not DC free code) as shown in Figure 7, between data bits "'1" and "1", 2 or more data bits "0" and less than 7 data bits are inserted. If the minimum bit period of the write data ■ signal is T, then the minimum bit period of the 2/7 code is 1.5T.

As a result, if the recording density on one side of the optical disk is the same as that for data recording in Figure 6, the apparent recording density on the top is 1.
．． It becomes 5 times.

(g) Effects of the Invention According to the present invention as described above, high recording density is possible and data focus can be read out accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a read/write system of an optical disk device. FIG. 2 is a read waveform diagram. Figure 3 shows an example of recording using a short hole (bit). FIG. 4 is a diagram showing the state of reading data having a predetermined data period. FIG. 5 shows an embodiment of the signal recording section of the optical disk device according to the present invention. FIG. 6 is an example of signal recording according to the present invention. FIG. 7 shows a 2/7 encoded table. are shown respectively. In fig. 1 is an optical disk, 2 is an optical head. 3 is the light emitting part, 4 is the light circuit. 5 is a light receiving section, 6 is a lead circuit. 7 is a sign. 8 is a "0゛'' continuous circuit. 9 is a pulse-to-pulse corner variable circuit. 10 is a laser power amplifier, and 11 is a laser. Agent: Patent attorney Hiroshi Matsuoka, Department 1:, Ni ・

Claims (1)

[Claims] This is a device that records data as binary data bits "1" and "0" by irradiating a light beam and recording a short hole on the surface of an optical disk.
In an optical disk device using an encoding method in which the time interval between the data bits "l" and "1" changes irregularly, the irradiation time of the light beam is set to 1 of the time interval between the data bits "l" and "1".
1. A signal recording method for an optical disc, characterized in that: /2.