JP2600568B2 - Optical recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording apparatus for optically recording information on an optical recording medium such as an optical disk.

[0002]

2. Description of the Related Art In recent years, compact discs (hereinafter referred to as CDs) in which digital audio signals are recorded on optical discs have become very popular, and CD-ROMs in which data are recorded instead of audio signals have also become popular. .

At present, when a digital recording signal is recorded on an optical disk in the process of manufacturing such an optical disk, generally, a recording laser is irradiated at a high level of the recording signal and the recording laser is cut off at a low level. The method of forming a pit on the top is adopted.

When a recording signal is recorded by such a method, as shown in FIG. 2, the length L2 of the pit formed on the optical disk is smaller than the pulse width L1 of the recording signal, as shown in FIG. R at both ends, the pulse width L3 of the reproduced signal when reproducing this pit is:
The pulse width becomes longer than the pulse width L1 of the recording signal, and information cannot be recorded and reproduced accurately.

Therefore, in a CD or the like, a pulse width correction circuit is provided in front of the optical modulator so that the pulse width of the recording signal is adjusted to a fixed length corresponding to the extension of the pit formed on the disk from the normal length. After the pulse width is corrected to the shorter pulse width, the corrected pulse width is input to the optical modulator, and the corrected laser is used to control the recording laser to record on the optical disk. As a result, as shown in FIG. 3, the recording signal having the pulse width L1 is corrected to the pulse width L4, a pit having a length of L5 is formed on the disk, and a reproduction signal equal to the length L1 is obtained. Information can be accurately reproduced.

FIG. 4 shows the target pit length to be recorded on the optical disk on the horizontal axis, and the normal pit length actually formed on the optical disk when the recording signal is recorded without performing pulse width correction on the vertical axis. Is the extension from the length. As can be seen from FIG. 4, as the pit length is reduced, the extension of the pits formed on the disk from the normal length is constant up to a certain pit length PL1. However, when the length is shorter, the irradiation section of the recording laser becomes shorter, and as the pit length becomes shorter, the extension from the regular length becomes shorter. Current CD (minimum pit length 0.
In the case of 86 μm), since the shortest pit length is longer than PL1, information can be accurately recorded / reproduced by a correction circuit that shortens all pulse widths by a certain length as in the above-described correction circuit.

[0007]

However, in the case where the shortest pit length is to be further shortened and recording is to be performed, the pit having the short pit length becomes a regular pit as shown in FIG. Since the extension from the length is small, the pits formed on the optical disk are shorter than the regular length, and information cannot be recorded and reproduced correctly. Conversely, if the correction amount of the pulse width correction circuit is adjusted to the short pit length,
The pits formed on the disc are longer than the regular length, and similarly, there is a disadvantage that information cannot be recorded and reproduced correctly.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pulse width correction circuit for accurately recording and reproducing pits whose shortest pit length is shorter than that of a current CD on an optical disk.

[0009]

SUMMARY OF THE INVENTION The present invention relates to an optical recording apparatus for correcting a recording signal with a pulse width, and optically modulating a recording laser with the corrected signal to record on a recording medium. First and second delay circuits for controlling the timing of the edge of a correction signal and one arithmetic circuit in order to accurately record and reproduce information on an optical disc having a pit length even shorter than that of a current CD and having a high recording density. By providing a signal correction section consisting of the following, information can be accurately recorded and reproduced with short pits.

[0010]

As a result, information can be recorded on the optical disk with pits having the shortest pit length even shorter than that of the current CD, and can be accurately reproduced. Therefore, the current C
It is possible to further increase the recording density than D.
Further, even if the pit length is short, the pit can be recorded on the optical disc with a regular length, so that a reproduced signal with little jitter can be obtained, which leads to an improvement in the error rate.

[0011]

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

In the following description, an example will be described in which a signal subjected to NRZI conversion after 2-7 modulation is used as a recording signal.
In this case, the pulse width of the recording signal is from 3T to 8T. T is the period of the clock used for 2-7 modulation.

FIGS. 5, 6, and 7 are circuit diagrams of a pulse width correction circuit of the present embodiment, and FIG. 8 is a circuit diagram of a conventional pulse width correction circuit. FIGS. 9A, 9B, 9C, and 9D show the operation of the method of the present embodiment in comparison with the operation of the conventional method. FIGS. 9A, 9B, 9C, and 9D correspond to FIGS. 5, 6, 7, and 8, respectively.

The conventional pulse width correction circuit includes one delay circuit 14 and one AND gate 5, as shown in FIG. The operation of this circuit is as shown in FIG.
All the pulses of the recording signal 7 are delayed by a predetermined delay amount by the delay circuit 14, and the AND signal of the original signal and the AND signal is used as the correction signal 8. Here, the delay amount of the delay circuit 14 corresponds to the extension of the pits formed on the disk from the regular length, and is constant for all pulse widths.

As shown in FIG. 5, a pulse width correction circuit according to a first embodiment of the present invention includes a pulse width detection circuit 6 for detecting a pulse width of a recording signal 7, a signal correction unit 4, The delay circuit 3 delays the recording signal 7 until the delay amount of the signal correction unit 4 is set according to the detection result of the detection circuit 6. The signal correction unit 4 is a basic part of the pulse width correction circuit according to the present embodiment, and includes a first delay circuit 1 for controlling the rising timing of the correction signal.
And a second delay circuit 2 for controlling the fall timing of the correction signal and one AND gate 5.

When a recording signal 7 as shown in FIG. 9A is inputted, a pulse width 5T is first detected by a pulse width detection circuit 6, and the first delay circuit 1 of the signal correction unit 4 is detected based on the detection result. delay amount DL1 _5T, the delay amount DL2 _5T of the second delay circuit 2 is set. This delay amount corresponds to an extension of a pit formed when a recording signal having a pulse width of 5T is optically modulated as it is and recorded on an optical disk from a regular length. The recording signal having a pulse width of 5T is delayed by the first delay circuit 1 and the second delay circuit 2 in which the delay amount is set, passes through the AND gate 5, and has a pulse width of 5T.
Is obtained.

Next, a pulse width of 3
T is detected, and based on this result, the delay amounts of the first and second delay circuits 1 and 2 are set to DL1 _3T and DL2 _3T , and a correction signal is obtained in the same manner. As described above, the pulse width of the recording signal 7 is detected by the pulse width detection circuit 6, and the delay amounts of the first and second delay circuits 1 and 2 of the signal correction unit 4 are changed according to the detection result. obtain. This delay amount corresponds to the extension of the pits recorded on the disk from the regular length.

As compared with the conventional method, it can be seen that the corrected pulse width corresponding to 3T which is the shortest pulse width is longer. Thereby, the amount of delay along the curve of the graph of FIG. 4 can be set, so that even short pits can be recorded on the disc with pits of regular length and reproduced accurately.

Next, a pulse width correction circuit according to a second embodiment of the present invention will be described. The circuit diagram is as shown in FIG. 6, and a pulse width separation circuit 9 for separating the recording signal 7 for each pulse width, a signal correction unit 4 for each separation signal, and one correction signal for each separation signal are used. OR gate 10 for Here, the signal correction unit 4 has the same configuration as that shown in the first embodiment. However, the first and second delay circuits 1 and 2 of the signal correction unit 4 in the first embodiment have variable delay amounts, whereas the second embodiment has The delay amounts of the first and second delay circuits 1 and 2 are fixed. The delay amount of the first and second delay circuits 1 and 2 is set to an amount corresponding to the extension of the pit formed on the optical disc from the regular length according to the graph of FIG. 4 for each pulse width. .

As shown in FIG. 9B, the operation of this circuit is to separate the recording signal 7 for each pulse width, and to separate the separated signal into first and second delays each having a specific delay amount. The signal is input to a signal correction unit 4 having circuits 1 and 2, and a correction signal is obtained for each separated signal. The OR gate 10 makes one correction signal for each pulse width to obtain a final correction signal 8.

The output of the circuit of the second embodiment is exactly the same as that of the circuit of the first embodiment. Although the number of elements increases as compared with the circuit of the first embodiment, the first and second delay circuits 1 and 2 of the signal correction unit 4 There is no need to control the delay amount of the delay circuit 3 for delaying the recording signal 7 until the setting of the signal correction unit 4 is completed, and the operation is simple and easy to configure.

Further, as shown in FIG. 4, when the pit length exceeds a certain value, the extension of the pit formed on the disc from the normal length is constant. If only the pulse width for forming is separated from the recording signal, and otherwise the same signal correction unit is used,
The number of elements is small and the configuration is easy.

In the first and second embodiments, only the pits formed on the optical disk are considered, and a method is employed in which an extension from a normal length is corrected by a recording signal and recorded. However, as the pit length becomes shorter, the length of the correction signal is determined in consideration of not only the pits formed on the optical disc but also the interval between the pit and the immediately preceding pit and the interval between the immediately following pit. I have to.

That is, when the shortest pit length is short enough to affect not only the pits recorded by the recording laser but also the adjacent pits, the interval between the shortest pit and the adjacent pit is short, and the shortest pit is short. When the distance between adjacent pits is long, comparing the length of the pits formed on the optical disk, the former becomes longer than the latter, and information cannot be reproduced accurately. Therefore, in such a case, not only one pit formed on the optical disk but also the same shortest pulse in consideration of the interval between the pit and the immediately preceding pit and the interval between the immediately following pit. A correction signal must be generated by changing the correction amount.

In the third embodiment of the present invention, as described above, the correction of the recording signal is performed in accordance with the pulse width of the recording signal, the interval between the immediately preceding pulse, and the interval between the immediately succeeding pulse. A circuit for determining the quantity will be described. As shown in FIG. 7, the circuit includes a pulse width detection circuit 6 for detecting the pulse width of the recording signal 7, two delay circuits 11 and 12 for delaying the detection result, and a delay amount of the correction signal based on the detection result. A delay circuit 3 for delaying the recording signal 7 until the control circuit 13 sets the delay amounts of the delay circuits 1 and 2 of the signal correction unit 4, and the signal correction unit 4. Become. Here, the signal correction unit 4 has exactly the same configuration as that described in the first embodiment.

The operation of this circuit will be described with reference to FIG. When the recording signal 7 as shown in FIG. 9C is input, the pulse width is sequentially changed by the pulse width detection circuit 6 to 3T,
Detected as 5T, 4T, 3T, 5T, 4T, 4T. This result is delayed by the two delay circuits 11 and 12 and input to the control circuit 13 together with the output of the pulse width detection circuit 6 as it is. The control circuit 13 first determines the delay amounts of the delay circuits 1 and 2 of the signal correction unit 4 when the pulse width is 5T, the immediately preceding pulse interval is 3T, and the immediately succeeding pulse interval is 4T. Next, the delay amounts of the delay circuits 1 and 2 of the signal correction unit 4 when the pulse width is 3T, the immediately preceding pulse interval is 4T, and the immediately following pulse width is 5T are determined. The operation of the signal correction unit 4 is exactly the same as that described in the first embodiment.

FIG. 12A shows a case where a continuous recording signal having the shortest pulse width is input to the circuit of the third embodiment.
2 (B) shows the operation when the recording signal whose pulse interval immediately before and immediately after the shortest pulse is the longest is input to the circuit of the third embodiment.

In this circuit, the pulse interval immediately before and immediately after the shortest pulse is the shortest 3T, and the pulse interval immediately before and immediately after the shortest pulse is the longest 8T.
Even with the same shortest pulse, the pulse width of the correction signal can be made different.

As a result, even a short pit can be recorded and reproduced on the optical disk more accurately.

However, recording accurately on an optical disk as described herein does not mean that pits corresponding to recording signals having the same pulse width are recorded on the optical disk with the same length. This is because, when the shortest pit length is very short, the entire shortest pit and a part of the pit further adjacent thereto are included in the beam spot of the reproducing laser as shown in FIG. When comparing the reproduced signal at the place where the shortest pit is continuous and the place where the interval between the shortest pit and the adjacent pit is very long, even if the shortest pit of the same length is reproduced on the disc, the amplitude of the reproduced signal A difference occurs in the level of the minimum value. In other words, to accurately record on the optical disk described herein means that pits are formed on the disk so that the above-described difference does not occur when reproduced.

Therefore, even if the pulse width of the recording signal is the same and the shortest, the pit length formed on the optical disk changes depending on the interval between the preceding and succeeding pulses. In the circuit according to the third embodiment, the delay amount of the delay circuit of the signal correction unit is determined in consideration of the above-described difference at the time of reproduction.

Finally, FIG. 1 shows a block diagram of an optical recording apparatus using the above method of the present invention. An optical modulator 16 is provided by a correction signal 8 obtained by correcting the recording signal 7 by the pulse width correction circuit 15 as described in the first, second, and third embodiments.
Modulates the recording laser 17, and is recorded on the optical disk 19 by the recording head 18.

In the above-described embodiment, a description has been given by taking a 2-7 modulated signal as an example of a recording signal. However, the same applies to any recording signal. In the above embodiment, the case of pulse width recording (PWM) using an NRZI-converted signal as a recording signal has been described. However, in the case of pulse position recording (PPM), only one type of pulse width is used. Therefore, the correction can be performed only by the signal correction unit of the present embodiment.

In the above-described embodiment, the recording signal correction method in the case where the length of the pit formed on the optical disk is longer than the irradiation section of the recording laser has been described. However, the present invention is not limited to this. In other words, the length of the pit formed on the optical disc may be shorter than the irradiation section of the recording laser. This depends on the power of the recording laser, the sensitivity of the resist, and the like. Even in this case, by inverting the recording signal or by changing the AND gate to the OR gate, it is obvious that the circuit described in the present invention can easily cope with the situation and does not leave the scope of the present invention.

When optical modulation is performed using the correction signal, a method of directly controlling and modulating the laser diode by the correction signal, an EO (Electro-Optical) modulator, or an AO (Acous)
tic-Optical) There is a method of modulating using a modulator,
Either method can be handled by the pulse width correction circuit of the present invention.

[0036]

As described above, the present invention relates to an optical recording apparatus provided with a pulse width correction device, which can accurately record pits having a shorter pit length on an optical disc than a current CD. It is what was constituted. This allows
The density can be reduced in the pit length direction, and a high-density disk can be manufactured. Further, since pits having a regular length can be formed on the optical disk, a reproduced signal with less jitter can be obtained, which leads to an improvement in the error rate.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a recording signal, a pit on an optical disc, and a reproduction signal.

FIG. 3 is a diagram showing a relationship between a recording signal, a correction signal, a pit corresponding to the correction signal, and a reproduction signal thereof.

FIG. 4 is a diagram showing an extension of a pit actually formed on a disc from a normal length with respect to a target pit length to be recorded;

FIG. 5 is a block diagram of a pulse width correction circuit according to the first embodiment of the present invention.

FIG. 6 is a block diagram of a pulse width correction circuit according to a second embodiment of the present invention.

FIG. 7 is a block diagram of a pulse width correction circuit according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram of a conventional pulse width correction circuit.

FIG. 9 is a diagram illustrating an operation comparison between the pulse width correction circuit of the present invention and a conventional pulse width correction circuit.

FIG. 10 is a diagram showing a relationship between pits on a disk and a beam spot of a reproducing laser.

FIG. 11 is a diagram showing the relationship between pits on a disk and reproduced signals.

FIG. 12 is an operation diagram of a circuit according to a third embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 delay circuit 2 delay circuit 3 delay circuit 4 signal correction unit 5 AND gate 6 pulse width detection circuit 7 recording signal 8 correction signal 9 pulse width separation circuit 10 OR gate 11 delay circuit 12 delay circuit 13 control circuit 14 delay circuit 15 pulse width correction Circuit 16 Optical modulator 17 Recording laser 18 Recording head 19 Optical disk

Continuation of the front page (56) References JP-A-59-22240 (JP, A) JP-A-4-344324 (JP, A) JP-A-2-87328 (JP, A) JP-A-2-29928 (JP) JP-A-5-197958 (JP, A) JP-A-4-12123 (JP, U) JP-A-4-12124 (JP, U)

Claims (3)

(57) [Claims] 1. A chromatic and first and second delay circuits and one arithmetic circuit for controlling the phase of the pulse edge of a recording signal
And a signal correction unit that, the recording pulse width of the recording signal
The interval between the pulse immediately before the signal and the pulse immediately after the recording signal.
The delay circuit of the signal correction unit
An optical recording apparatus characterized in that a recording laser is optically modulated by a correction signal obtained by changing a delay amount to record a signal on an optical recording medium. 2. An interval between a pulse immediately before and after a recording signal and a pulse immediately after the recording signal.
When the pulse width of the correction signal is large, the pulse width of the
When the interval between the previous and next pulse is small, the
2. The optical recording apparatus according to claim 1, wherein the delay amount of the delay circuit of the signal correction unit is changed so as to be larger than the pulse width . 3. The phase of an edge of a pulse of a recording signal is controlled.
First and second delay circuits and one arithmetic circuit for
Signal corrector to separate the recording signal for each pulse width
And a pulse width separation circuit.
The signal having a fixed delay amount for each separated pulse width signal.
The recording laser is controlled by the correction signal obtained by the signal correction unit.
It is characterized by recording a signal on an optical recording medium by optical modulation
Optical recording device that.