JPH0772942B2 - Optical disk device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical information recording / reproducing apparatus for recording and reproducing information on an optical recording disk having an optically detectable guide track.

2. Description of the Related Art In an optical recording disk memory, which is regarded as a promising high-density and large-capacity memory, an error control technique for overcoming the low error rate of the optical recording disk is very important.

An optical recording disk is usually provided with an optically detectable guide track such as a guide groove for increasing the track density, and the recording layer formed on this guide track has a thickness of 1 μm.
Irradiate a laser beam that has been narrowed down to make a hole or change the reflectance for recording.

Since the recording dots and the track pitch are about 1 μm, the manufacturing process of the optical recording disk (formation of the guide track,
Various defects, dust, and scratches are generated due to the production of a replica disc, vapor deposition of a recording material, formation of a protective layer, or the use environment of an unrecorded disc, resulting in a dropout of a reproduction signal.

The dropouts are diverse and occur in bursts and random ones. As a result, the raw error rate of the optical recording disk is said to be 10 ⁻⁴ to 10 ^−6, and the raw error rate of the magnetic disk, which is a typical conventional recording medium.
At present, it is extremely worse than the raw error rate of 10 ^-9 to 10 ^-12 .

Therefore, an optical information recording / reproducing apparatus using an optical recording disc usually has strong error control.

FIG. 4 is a diagram showing details of the format of a signal actually recorded on the optical recording disk. Reference numeral 1 is a sync signal for urging a clock synchronization pull-in at the time of data reproduction, 2 is a data mark using a certain code to indicate the beginning of data, and 3 is a redundant bit added based on the error correction code theory. , Interleaved encoded data. The recording signal block B consisting of the synchronization signal 1, the data mark 2, and the encoded data 3 is recorded in the information recording area of the sector divided by the address portion 4 as shown in B of FIG. In the address section 4, track addresses and sector addresses are generally recorded.

As described above, it is very effective to record the data by dividing the optical recording disk into sector structures and dividing the data into certain units, when recording digital information in which the length of the data is variable, and to make the recording area efficient. Well available.

The dropout existing on the optical recording disk generally reduces the envelope of the recording / reproducing signal and causes a demodulation error. When this dropout exceeds the capability of the error correction code, the error cannot be completely corrected during demodulation.

In the case of a non-rewritable disc, when data is recorded in a certain sector and then the data is read and it is determined that the demodulation error cannot be corrected, the sector data is processed so that it is not reproduced, and it is recorded in another sector. You need to record the data again.

In addition, when updating a part of data or erasing a file, it is better not to reproduce unnecessary sector data.

Furthermore, when there is a dropout in the information recording area of an unrecorded sector that is expected to prevent correct reproduction by recording data, the sector should not be recorded as a defective sector. It is desirable that the same applies to a rewritable optical recording disk.

As described above, when the sector in which data is to be recorded / reproduced is a defective sector or is not used for the purpose of updating or the like, it is necessary to perform a process capable of discriminating it during reproduction. is there.

Therefore, in order to identify a defective sector and an unused sector, a plurality of pulse trains of a specific pattern (hereinafter, the operation of writing a plurality of pulse trains is called a delete and a plurality of pulse trains are called a delete pulse) are recorded data in the information recording area of the sector. There is a method of overwriting on (Japanese Patent Application No. 58-222405).
No. 59-43415). This method will be briefly described.

The data portion of the defective or unused sector is shown in FIG. 6 (a), and a delete pulse (shown in FIG. 6 (b)) having a frequency much lower than the frequency of the data is overwritten on this data portion. The data recorded in a layer with a constant optical power is crushed by the delete pulse and the data cannot be reproduced.

The reproduced signal at this time is shown in FIG. 6 (c). At this time, the delete pulse is detected by the delete pulse detection circuit and is recognized as a defective sector or an unused sector.

FIG. 7 shows a conventional example of an optical disk device having such a delete pulse detection circuit.

In FIG. 7, 11 is an optical disk capable of recording an information signal, which rotates at a constant speed. Reference numeral 12 is an optical head for focusing the light beam from the semiconductor laser 13 into a minute light, 14 is a semiconductor laser drive circuit, and terminal A is an input terminal for outputting a data signal or a delete pulse. Reference numeral 15 is a head amplifier for reproducing a signal from the disk 11, 16 is an equalizer circuit for correcting the frequency characteristic of the reproduced signal, and 17 is a low-pass filter for band limiting. Reference numeral 18 is a differentiating circuit for differentially detecting the reproduced signal. In a recording / reproducing apparatus using such an optical disk, differential recording is generally performed in order to improve the reliability of the apparatus due to the characteristics of optical recording. Therefore, it is general to detect a data signal or the like from a reproduction signal through a differentiating circuit.

Next, 19 is an amplifier, and 20 is a data detection circuit for detecting a data signal, which sends out the data signal from a terminal 21.

On the other hand, when detecting a delete pulse, the output signal of the amplifier 19 is input to the delete pulse detection circuit configured by the envelope detection circuit 22 and the comparator 23. The operation of the delete pulse detection circuit will be described with reference to the waveform chart of FIG.

FIG. 8B shows a reproduced signal from the head amplifier 15,
The section (a) shows the reproduced data signal. FIG. 8 (e) shows a record signal of the delete pulse, and when this signal is overwritten on the reproduction signal shown in FIG.
The signal shown in FIG. 6F is reproduced. The section shown in Fig. 8 (b) is the deleted section, and the original data signal (a)
Is destroyed and the data signal in that section is not reproduced. 8th
The reproduction signal sags in FIG. 6F because of the frequency characteristic of the reproduction circuit. Differentiating circuit 18
The waveform shown in FIG. 8 (g) is obtained by differentiating with. In the delete pulse detection circuit, this signal is input to the comparator 23, and the envelope detection circuit 22 detects the envelope signal of this signal (shown in FIG. 8C) and is input to the comparator 23 to binarize the reproduction signal. To do. The output waveform of the comparator 23 is shown in FIG. To detect the delete pulse shown in FIG. 8 (e) from this signal,
This can be easily performed by detecting the width of the delete section (b) (not shown). Therefore, it is important for the delete pulse detection circuit to detect a clean binarized reproduced signal having no signal in the delete section as shown in FIG. 8 (h).

Problems to be Solved by the Invention FIG. 9 shows the characteristics of an optical disc when the conventional optical disc device described above is deleted.

FIG. 9 (i) shows a delete power (recording power for recording a delete pulse) that is not enough to suppress the data signal when the delete is performed, that is, a reproduced signal waveform when the delete is performed with a low power. FIG. 9 (j) shows a reproduced waveform when recorded with the optimum delete power that is sufficiently suppressed, and FIG. 9 (k) shows a reproduced waveform when recorded with a delete power higher than the optimum power. Although changing in level, the already recorded data signal is not suppressed and the original data signal is reproduced. When such a reproduced signal is detected by the delete pulse detecting circuit shown in the conventional example of FIG. 7, the output signals of the differentiating circuit 18 and the amplifier 19 are (i) ′, (j) ′, (k) in FIG. 9, respectively. ) ′. That is, FIG. 9 (i) ′, (k) ′
As described above, if an attempt is made to detect a delete pulse from a reproduction signal in which the original data signal remains, the detection margin of the comparator 23 becomes narrow and the reliability deteriorates. Therefore, in order to improve the reliability, it is necessary to control the delete power to the optimum delete power so that the original data signal in the delete section is completely suppressed. The optimum delete power at this time is closely related to the recording power of the original data signal, and when the absorption power on the optical disk surface becomes equal to that of the data signal and that of the delete pulse, the data signal becomes It is completely crushed and can be said to be the optimum delete power. However, the emission power of the semiconductor laser changes depending on the ambient conditions, particularly the temperature conditions, the deterioration of the semiconductor laser itself, and the variations in the sensitivity of the optical disc. Therefore, the recording power of the original data signal and the delete power are different. Is not exactly required.

Therefore, in some cases, the original data signal cannot be sufficiently suppressed when the delete is performed, and therefore the reliability of the delete pulse detection is insufficient.

It is an object of the present invention to solve such a problem and to provide an optical disk device capable of surely detecting a delete pulse.

Means for Solving the Problems In order to solve the above problems, the present invention is to detect a delete pulse by clamping a reproduction signal from a disc, detecting the envelope signal of the reproduction signal, and comparing the detected signals.

Operation The present invention has the above-described configuration, and the effect is achieved by the operation described below.

The light beam modulated by the data signal is formed as a pit of the data signal on the optical disc surface. The reflectance of this pit is the unrecorded area (where the light beam is not irradiated)
It is about 10% larger than. This change in reflectance is proportional to the recording power, and the greater the recording power, the greater the reflectance. Therefore, the reproduction signal also becomes large. Since the delete pulse has a frequency considerably lower than that of the data signal as described above, the power absorbed by the disk surface becomes considerably large even if the delete power is about the same as the recording power of the data signal. Therefore, the pits of the data signal and the pits of the delete pulse have considerably different reflectivities, and the reproduced signal amplitude of the delete pulse becomes large. Next, when reproduced signals having different reproduced signal amplitudes are reproduced in this way, amplitude fluctuations such as sag occur due to frequency characteristics of the circuit, which complicates signal processing and deteriorates reliability. Therefore, by clamping, the amplitude fluctuation can be suppressed and kept constant, and by detecting the amplitude difference between the delete pulse and the data signal, a reliable delete pulse can be detected.

Embodiment FIG. 1 shows an embodiment of the present invention.

In FIG. 1, the same parts as those in FIG. 7 of the conventional example are designated by the same reference numerals and the detailed description thereof will be omitted. Reference numeral 11 is an optical disk, 12 is an optical head for focusing the light beam from the semiconductor laser 13 into a minute light, 14 is a semiconductor laser drive circuit, terminal A is an input terminal for inputting a data signal or a delete pulse, 15 is a head amplifier, 16 Is an equalizer circuit, 17 is a low-pass filter, 18 is a differentiating circuit, 19 is an amplifier, 20 is a data detection circuit for detecting a data signal, and 21 is a data signal sending terminal.
Amplifier 30, clamp circuit 31, envelope detection circuit 32,
The comparator 33 shows the configuration of the delete pulse detection circuit of the present invention.

Each operation will be described with reference to the waveform chart of FIG. FIG. 2 (l) shows a reproduced signal from the head amplifier 15 and shows a data signal before deletion. FIG. 2 (m) shows a delete pulse. FIG. 2 (m) shows a reproduced waveform when the delete pulse is deleted from the data signal (FIG. 2 (l)). The reproduced waveform at this time shows an example in which the data signal component remains in the delete section, unlike the optimum delete power, and the waveform shown in (e) of FIG. The reproduced waveform is shown below. As can be seen from the waveform diagram, the delete pulse amplitude increases in proportion to the delete power. The above reproduced signal is input to the clamp circuit 31 via the equalizer circuit 16, the low-pass filter 17, and the amplifier 30. The clamp circuit 31 absorbs the amplitude fluctuation of the reproduction signal and the amplitude fluctuation due to the sag and the like due to the amplitude difference between the data signal and the delete pulse and adjusts them at a constant level. As an example, FIG. 2 (o) shows a reproduced waveform when clamped in an unrecorded portion. Next, the envelope signal of the clamped reproduced signal is detected by the envelope detection circuit 32 (shown in (f) of FIG. 2 (o)). The clamped reproduction signal is compared with the envelope signal by the comparator 32 to detect the delete pulse section. This signal is shown in FIG.

FIG. 3 shows a configuration example of the clamp circuit 31, the envelope detection circuit 32, and the comparator 33. The reproduction signal from the amplifier 30 is input to the terminal E. Capacitor C ₁ , diode
The clamp circuit is composed of D ₁ , and the clamp time constant is determined by C ₁ . FIG. 3 shows an example of clamping at the V _V level. The transistor Q ₁ and the resistor R _{1 form} an emitter follower and output a reproduction signal. The envelope detection circuit is generally composed of a diode D ₂ , a capacitor C ₂ and a resistor R ₂ , and the detection time constant is determined by the capacitor C ₂ and the resistor R ₂ . These signals are input to the comparator 33 to binarize the reproduced signal and detect the delete pulse section.

As described above, according to the present invention, since the delete pulse can be detected by the amplitude difference between the delete pulse and the data signal when the delete pulse is recorded, the delete pulse can be reliably obtained without setting the optimum delete power. The delete pulse can be detected. If the delete power is set to be slightly higher than the recording power of the data signal, the delete pulse can be detected more reliably.

Further, although the example in which the clamp circuit clamps the reproduced signal at the unrecorded portion is shown, the same effect can be obtained by clamping at the recording portion. Further, although an embodiment is shown in which the delete pulse is detected after passing through the equalizer circuit 16 and the low-pass filter 17, the same effect can be obtained by providing a delete pulse detecting circuit after the output of the head amplifier 15.

Although an example in which the delete pulse is overwritten on the data signal has been described above, even if the delete pulse is recorded in the sector of the unrecorded portion, it can be detected similarly, and the practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical disk device showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of the delete pulse detecting circuit of the present invention, and FIG. 3 is a structural example of the delete pulse detecting circuit. 4 and 5 are diagrams showing a format of a signal to be recorded on an optical disk, FIG. 5 is a time chart showing an arrangement of an address portion and a data portion of a sector, and FIG. 6 is a waveform chart showing a relation between a data signal and a delete pulse. FIG. 7 is a block diagram of an optical disk device showing a conventional example, FIG. 8 is a reproduction signal waveform diagram showing the operation of a delete pulse detection circuit shown in the conventional example, and FIG. 9 is a reproduction characteristic of an optical disk when deleted. It is a figure. 12 …… Optical head, 13 …… Semiconductor laser, 14 …… Semiconductor laser drive circuit, 15 …… Head amplifier.

Claims (1)

[Claims] 1. A means for modulating an optical power to record an information signal and a delete pulse having a frequency component lower than the information signal on a predetermined track of an optical disk, and waveforms of an equalizer and a low-pass filter as a delete pulse reproducing means. A clamp circuit that clamps the shaped signal, an envelope detection circuit that obtains the envelope of the signal output from the clamp circuit, and a comparator that compares the output signal of the clamp circuit and the output of the envelope detection circuit are provided. Characteristic optical disk device.