JPH05159297A - Data recording area changing method for optical disk storage device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a read/write error even when a defect is grown due to repetition of overwrite by detecting a. defect of abnormally high reflectance by a read signal and changing a sector comprising the defect over to a sound sector at the time of detecting the defect which is larger than a prescribed size. CONSTITUTION:A defect of abnormally high reflectance in a read area of an optical disk 1 is detected by a defect detecting circuit 20 based on a code pattern read signal read out by a head 3 from the disk 1, and a defect signal S in size corresponding to the reflectance is outputted to a processor 10. Then, the size of a defect is counted by a defect detecting means 30 with a counter, and a place of the defect is stored together with the size of the defect. When the defect becomes more than a prescribed value based on the above storage contents, the sector comprising the defect is changed over to the sound sector by a storage area changeover means 40 with reference to a storage area management table 41, and even when the defect is grown due to repetition of overwrite, no read/write error is substantially generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording area in an optical disc before a read / write error occurs when a defect is found in the optical disc in which data is overwritten or overwritten on a phase change recording medium. The present invention relates to a data recording area switching method of an optical disk storage device that is switched.

[0002]

2. Description of the Related Art Although a disk storage device used for external storage of a computer is required to have a larger storage capacity and a smaller size, the optical disk system has a recording density higher by about 1 to 2 digits than the magnetic system. In addition, it is regarded as the mainstream of future external storage devices because of the advantages of being able to access data with a completely contactless head. This optical disk storage device is roughly classified into three types, that is, a read-only type, a write-once type, and a rewritable type in terms of functions. In principle, there are roughly two types, magneto-optical type and phase change type. When rewriting data, the former requires erasing old data and then recording new data, while the latter requires old data. Since it is possible to overwrite so that new data is overwritten on top of it, there is an advantage that access time can be shortened easily. The present invention relates to such a rewritable and phase change type optical disk storage device, and as is well known, the principle of recording and reproduction by overwriting of data will be briefly described below with reference to FIG. ..

In an optical disk storage device, laser light is generated from a laser diode of a recording / reproducing head and focused on a small diameter spot of about 1 μm on a track of an optical disk by a lens. When data is overwritten in FIG. 4 (a). This laser light power W is shown. The power W is switched according to the code pattern of the data to be recorded to the low power W0 and the power W1 which is 50% or more higher than that as shown in the figure, and the track shown in FIG. At T, regardless of the code pattern recorded before that, the recording medium such as chalcogen has low power consumption.
The portion receiving W0 becomes crystalline with high light reflectance, and the portion hatched in the figure receiving high power W1 becomes amorphous with the reflectance being about one-third lower. In the figure, code patterns of data having different reflectances corresponding to these electric powers W0 and W1 are shown by P0 and P1, respectively, and the pattern P0 represents a code of 0 and the pattern P1 represents a code of 1, respectively. Usually, the pattern P1 is used as a unit code UC, and the pattern P0 is a code pattern that continues for a multiple of that. For example, the range indicated by three P1s in FIG. 4B and three P0s between them corresponds to 100010001 code patterns.

As described above, the code pattern of the data written in the recording medium of the track T can be read by applying a spot of a weak laser beam and receiving the reflected light by a phototransistor or the like at the time of reproduction. Even if it is done carefully, it is unavoidable that a defect DF rarely occurs on the recording medium of the track T as shown in FIG. 4 (c), and of course the code of the patterns P0 and P1 can be read at the place where the defect DF occurs. It disappears, or the code pattern itself cannot be written.

For this reason, as is well known, an error correction code has been conventionally written at the same time as data in each sector which is a recording unit of data in an optical disk, and even if several codes cannot be read due to a defect DF. It is designed to recover or reproduce the original data to prevent a read error. It is also possible to increase the probability that an error can be corrected by a method called interleaving, in which writing of data in a sector is complicated in units of bytes or bits. To prevent the occurrence of a write error, so-called verify is performed to verify whether or not the data was written and read correctly each time the data is written, and if an error occurs, the data is rewritten to the substitute sector. Is customary.

[0006]

However, in the phase change type optical disk, the defect DF tends to grow gradually as data overwrite is repeated, as shown in FIG. 4 (d). If the size exceeds a certain limit after overwriting a number of times, there is a problem that the error cannot be corrected by the above-described error correction code and a read error occurs.

In the phase-change type optical disk, the recording medium is made crystalline or amorphous by utilizing the difference between the heating temperature and the cooling rate by the laser light spot. It is considered that this is because the defects propagate with the strain, and it is very difficult to prevent the defect growth from the reason of this. It is known that the growth of a defect is particularly fast when it is caused by the inclusion of minute dust or the like.

Further, since the above-mentioned error correction code is originally suitable when the disturbance of the read signal due to the defect is small, the correction becomes impossible if the disturbance becomes large, and the occurrence of the read error is unavoidable or rare. However, there are also cases where incorrect data is read and incorrect data is read. As a countermeasure against this, a means for inserting a so-called resynchronization code into the recorded data is known.
Even if it is useful for preventing erroneous correction, it does not have a function of correcting even the disturbance of the read signal due to a large grown defect. The same applies to the interleave method described above. Furthermore, errors during writing can be almost completely prevented by the above-mentioned verification.
Since it is necessary to wait for the rotation, for example, 15-20 mS of time is wasted each time data is written in each track, and the effective access time at the time of writing is extended.

In view of the above problems, it is an object of the present invention to prevent a read / write error from occurring even if a defect in a phase change type optical disk grows as overwriting is repeated.

[0010]

According to the method of the present invention, an optical disk storage device in which data is overwritten on a phase change recording medium has an abnormally high light reflectance from a data read signal. This is achieved by providing a defect detection circuit for detecting a defect and its size, and when a defect of a predetermined size or more is detected, the data recording area including the defect portion is switched to another sector in sector units. It

In order to match the data handling operation of the optical disk storage device, the above-mentioned defect detection circuit detects a defect of the phase change type recording medium with a size represented by the number of unit codes of the data recording code pattern. Therefore, it is advantageous to configure the defect detecting means so as to operate in synchronization with a clock pulse that specifies the speed of the spindle motor for driving the optical disk.

Further, at the start of use of the optical disk storage device, a sector including a defect is previously detected and placed by a defect detection circuit before writing the first data on the optical disk, and at this time, a defect of a predetermined size is detected. It is advantageous to set the data recording area of the optical disk storage device in a consistent sector number order within the optical disk only for sound sectors excluding the detected sectors. It is preferable that the criterion of (3) is, for example, about 3 unit codes or more, which is considerably stricter than the size that can be corrected by the error correction code.

Further, during use of the optical disk storage device, a defect detection circuit detects and stores a defect in the optical disk between data read / write operations, and the defect is detected in a sector in which a defect having a predetermined size or more is detected. When writing data, it is advantageous to switch it to a preset alternative sector in the optical disc and write it. The criterion for determining the size of the defect to which this sector should be switched is to start using the optical disc storage device. In this case, it is preferable that the unit code is looser than the standard for excluding the sector, but about 5 unit codes or more, which is stricter than the size that can be corrected by the error correction code. It should be noted that it is advantageous to set the replacement sector in advance on a specific track set in the optical disc. Furthermore, in the above-mentioned defect detection while the optical disk storage device is in use, data overwrite is performed a predetermined number of times, for example, 1
It is practical to do it every time it is repeated.

In carrying out the method of the present invention, in order to control the above-mentioned defect detection and the switching of the recording area based on it, a processor incorporated in the optical disk storage device for internal control including the read / write operation thereof is carried out. The defect detecting means and the recording area switching means are loaded as software, and the recording area management table including the logical or physical address of the sector is stored and the defect detecting means activates the defect detecting circuit and outputs the defect detection result. It is preferable that the recording area switching means has a role of storing information and the recording area switching means has a function of switching a sector including a defect to a sound sector based on the stored contents of the defect detection means and the recording area management table.

[0015]

According to the present invention, in the disk storage device having the phase change type optical disk, the reading of the data code pattern is performed by utilizing the difference in light reflectance between the crystalline portion and the amorphous portion in the recording medium. , And because the defects of the recording medium, especially its grown portion, have higher reflectance than the crystalline portion,
Focusing on the fact that a portion with an abnormally high reflectance can be detected as a defect from the waveform of the read signal of the code pattern, the defect detection circuit described in the configuration of the previous section is incorporated in the optical disk storage device to identify the defect location in the optical disk. The size is detected as needed, and when the detected defect is larger than a predetermined size, the sector containing the defect is switched to a healthy sector, and the defect grows and a read error actually occurs. This is to eliminate the cause of the error before it occurs, that is, before the defect grows large while it is still small. Therefore, according to the method of the present invention, the read error can be almost eliminated, and the write error can be similarly prevented in advance.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration circuit diagram showing an internal configuration example of an optical disk storage device suitable for carrying out the recording area switching method of the present invention.
3 is an enlarged view of a portion including a defect of a track showing a defect detection procedure and a waveform diagram of a read signal corresponding thereto, and FIG. 3 is a circuit diagram of a specific configuration example of the defect detection circuit.

The optical disk 1 shown in the upper part of FIG. 1 is formed by cutting a track setting groove on a lower surface of a plastic substrate having a diameter of, for example, 5.25 inches and forming a recording medium 1a on the upper surface thereof. For example, ZnS and Ge ₂ Sb ₂ Te ₅
ZnS and Al are sequentially laminated to have film thicknesses of 120, 60, 170, and 100 nm, respectively, and Ge ₂ Sb ₂ Te _{5 in this} is the actual recording medium. This optical disk 1 is driven at a high speed by a spindle motor 2 as usual, and the rotation speed is a clock pulse CP given to its drive circuit 2a from the processor 10 side.
Specified by.

A head 3 shown on the lower left side of the optical disk 1.
Is for focusing a small spot of the laser beam LB on the recording medium 1a, and the position in the left-right direction of the drawing is controlled by the drive circuit 3a which receives the drive signal DS from the processor 10, and the inside of which generates the laser beam LB. The power applied to the laser diode is switched according to the read / write command RW, and is controlled by the write signal WS that specifies the data code pattern. When reading data,
The reflected light of the weak laser beam LB given to the recording medium 1a is detected by a phototransistor or the like in the head 3 and then an analog read signal RSa is output. It is converted and synchronized by the synchronizing circuit 5, and then given to the encoder / decoder circuit 6. The circuit 6 decodes the read signal RS into a digital pulse DP such as NLZ or encodes the digital pulse DP into a write signal WS according to the read / write command RW given from the processor 10.

The processor 10 is incorporated in the optical disk storage device for overall control of its read / write operation, and includes a data control circuit 11 which is a data-only processor and a communication bus.
Interfaced with internal bus 13 via 12
It is connected to a computer (not shown) via 14 and an external bus 15. The data control circuit 11 uses a serial digital pulse DP
To parallel data and load it on the internal bus 13 via the RAM 11a, or conversely from the internal bus 13 to the RAM 11a.
The parallel data is read via and output as a serial digital pulse DP.

According to the present invention, the defect detection circuit 20 is incorporated in the optical disk storage device having the above-described structure to provide the head 3
The read signal RSa is given from and the analog waveform is shown in FIG.
The defect DF in the track T shown in (a) is detected. Figure 2
As shown in (b), the read signal RSa is composed of two levels, high and low, corresponding to the code pattern P0 of high quality and high reflectance of the detection quality and the code pattern P1 of amorphous and low reflectance of FIG. However, if the defect DF exists on the track T, an abnormally high level waveform appears as shown in the figure, and the defect detection circuit 20 utilizes this to detect the defect DF.

Therefore, as shown in the circuit example of FIG. 3, the read signal RSa is compared with a predetermined threshold value Vt by the comparator 21 of the defect detection circuit 20, and the waveform of the read signal RSa of FIG. Forces its output high when the threshold Vt is exceeded. One-shot circuit 22p of FIG. 3 receiving this comparison output
Responds to the rising to the high level and the one-shot circuit 22n to the falling to the low level, and outputs a pulse having a predetermined width to the data inputs of the D flip-flops 23 and 24, respectively. In this embodiment, the operation of the defect detection circuit 20 is related to the code patterns P0 and P1 of FIG.
A clock pulse CP having the same period as the width of the unit code UC on the code pattern is applied to the trigger inputs of the flip-flops 23 and 24. Therefore, these flip-flops 23
And 24 are set in synchronism with the clock pulse CP when receiving the output pulses of the one-shot circuits 22p and 22n, respectively, and the flip-flops 25 of the subsequent stage are set by their Q outputs.
To set and reset respectively.

In this way, the Q of the flip-flop 25 is
The output becomes high only during the time when the waveform of the read signal RSa in FIG. 2 exceeds the threshold value Vt expressed by the number of unit codes UC, and as a detection signal S indicating that the defect DF is detected, the defect detection circuit It is output from 20. Further, the AND gate 26 is enabled by the high level of the Q output, and the clock pulse CP is given to the counter 27 to count and store the above-mentioned unit code number indicating the size of the detected defect DF.

Corresponding to the defect detecting circuit 20 as described above, in this embodiment, the defect detecting means 30 is loaded as software on the processor 10 of FIG. In order to detect a defect in the optical disk 1, a reset pulse is output from the defect detecting means 30.
The RP is sent to the defect detection circuit 20 to clear the count value of the counter 27. When the defect detection circuit 20 detects a defect, it outputs a detection signal S, and the defect detection means 30 receiving this signal waits for its disappearance and reads the count value N of the counter 27 indicating the size of the defect. At the same time, the defect detection means 30 causes the head 3
Since the position on the optical disc 1 is designated by the above-mentioned drive signal DS, the location of the detected defect is stored together with its size.

Further, in this embodiment, the recording area switching means 40, which operates based on the defect stored in the defect detecting means 30 in the processor 10, is loaded as software, and the sector to be referred to at the time of the operation is loaded. The recording area management table 41 that stores logical addresses and physical addresses
Set within 10 storage areas. As is well known, the data to be read and written from the computer side is designated by a logical address, but the optical disk storage device side refers to this logical address by referring to the recording area management table 41 for storing the destination where the storage area is switched. Read / write after converting to the physical address in. It should be noted that the same contents as the recording area management table 41 are recorded and stored in a specific range in the optical disk 1, and are read into the processor 10 from there each time the optical disk storage device is powered on and activated.

Now that the description of the configuration of the optical disk storage device related to the implementation of the method of the present invention has been completed, an example of its operation will be described. The above-mentioned recording medium 1a is usually formed on the optical disk 1 by a high-frequency magnetron method, but since it is initially amorphous, it is first irradiated with laser light to be crystalline before being used. In this embodiment, the optical disc 1 is 36
The data is read / written by rotating the laser at 00 rpm and applying a laser beam LB having a wavelength of 830 nm from the head 3 in FIG. The laser light power at the time of writing is set to 9 mW as the so-called erasing power level for the crystalline code pattern P0 in FIG. 2 (a),
The recording power level for the amorphous code pattern P1 is set to 15
mW. This code pattern is the usual RLL 2-7
The modulation method was used, and the unit code UC time width was 55 nS.

Data can be written immediately after the recording medium 1a of the optical disk 1 is made crystalline, but in the method of the present invention, it is preferable to detect a defect before this, and this defect detection is carried out on a trial basis by overwriting the data. It is desirable to carry out after repeating several hundred to several thousand times. In this embodiment, after overwriting 1000 times, the defect detection circuit 20 is operated to detect defects over the entire surface of the optical disc 1. The size of the defect detected at this time is usually at most 2 in terms of the number of unit codes, but the maximum defect of about 4 unit codes is rarely detected.

As a result of continuous overwriting on this not so good optical disc 1, a maximum defect of 10 unit codes was detected 40,000 times from the beginning, and a maximum defect of 20 unit codes was detected at 100,000 times. Of course, it was impossible to correct the read data by the error correction code after it was detected. Since the defects tend to grow gradually in this way, in this embodiment, the recording area switching means 40 is operated at the start of use of the optical disk storage device, and the sectors in which the defects of three unit codes or more are detected by the above-mentioned defect detection are selected. I tried to write the data except.

As a result, the data is written only to the sound sector from which the defective sector has been skipped, so that the data recording area at the start of use does not need to move the head 3 unnecessarily so that the sector number is consistent in the optical disk 1. Set in order. The initial setting result is the recording area management table.
It is stored in 41 and is also recorded in the aforementioned specific range in the optical disc 1. In this way, when starting the use of the optical disk storage device and setting the data recording area by excluding the sectors having defects of 3 unit codes or more, no read error occurs even after overwriting 1 million times, and the defective sectors are recorded. If not excluded, a read error occurred after 100,000 overwrites.

After starting the use of the optical disk storage device in this way, the defect detection circuit 20 is operated between the data reading and writing operations in use to detect defects over the entire surface of the optical disk 1. This defect detection need not always be performed each time the read / write operation is interrupted, but may be performed after overwriting is repeated about 10,000 times. As a result of the experiment in which the data is continuously overwritten on the ordinary optical disc 1 having the defect of 2 unit code or less at the beginning, the defect of 3 unit code or more starts to be detected after the overwrite of 40,000 times from the beginning. Later, defects exceeding 10 unit codes are detected. Therefore, in this embodiment, a sector in which a defect having a unit code of 5 or more is detected at the time of detecting a defect after the use of the optical disk storage device is stored, and the data is written in the defective sector in the optical disk 1 next time. Then, the data is switched to and written to the preset replacement sector.

In the optical disk storage device in which the storage area is thus switched by the method of the present invention, a defective sector that may cause an error is switched to a sound replacement sector before the read error actually occurs, so that no read error occurs. Almost nothing. As a result of an experiment in which data is repeatedly overwritten on a sector in which a defect of 5 unit codes or more is detected, a read error occurs after 100,000 overwrites after the defect is detected. Further, as a result of operating the optical disk storage device according to the method of the present invention without verifying at the time of writing data, there is almost no writing error, and the average access time at the time of writing data can be shortened by about 20%. Has been obtained.

[0031]

According to the method of the present invention, a defect detection circuit for detecting a defect having an abnormally high light reflectance and its size from a read signal of data for an optical disk storage device which overwrites data on a phase change recording medium. When a defect of a predetermined size or more is detected by this, the data recording area including the defect portion is switched to another sector in the optical disk in sector units, and the following effects are obtained.

(A) By switching a sector in which a defect of a predetermined size or more is detected to a healthy sector, the cause of the error is eliminated before the defect grows and a read error actually occurs. Therefore, almost no read error occurs. By implementing the present invention, it is possible to improve the guaranteed number of times of data overwriting of the optical disk storage device to 1 million times or more. (b) Conventionally, it took a long time to rewrite data in a sound sector when the verification after writing fails, but the method of the present invention can substantially eliminate the need for rewriting at the time of writing data. .. (c) In order to prevent the occurrence of a data read error, it is customary to perform a so-called retry 2 or 3 times when the first read fails, but in the present invention, the defect in each sector is corrected by an error correction code. Since it can be managed within the size as much as possible, the probability of read failure can be reduced and the average access time during read can be shortened accordingly.

As described above, the method of the present invention compensates for the defects that the defects of the phase-change recording medium grow as data is repeatedly overwritten, and improves the long-term operation reliability and the operation performance of the optical disk storage device. It is possible to make a significant contribution to its practical application and spread.

[Brief description of drawings]

FIG. 1 is a configuration circuit diagram illustrating an internal configuration of an optical disk storage device suitable for implementing a recording area switching method according to the present invention.

2A and 2B show a procedure for detecting a defect in an optical disk by a defect detection circuit. FIG. 2A is an enlarged development view of a part of a track including a defect, and FIG. 2B is a waveform of a corresponding read signal. It is a figure.

FIG. 3 is a circuit diagram of a specific configuration example of a defect detection circuit.

FIG. 4 shows a procedure for writing a data code pattern on an optical disc using a phase-change recording medium. FIG. 4A is a waveform diagram of laser light power at the time of writing the code pattern,
The figure (b) is a partially enlarged development view of the track in which the code pattern is written, the figure (c) is a partially enlarged development view of the track including the defect, and the figure (d) shows that this defect is overwritten. It is a partially expanded development view of the track after it grew up by repetition.

[Explanation of symbols]

 1 Optical Disc 1a Recording Medium 3 Head 10 Embedded Processor of Optical Disc Storage Device 20 Defect Detection Circuit 30 Defect Detection Means Loaded in Processor 40 Recording Area Switching Means Loaded in Processor 41 Recording Area Management Table DF Defects Stored in Processor N Number of unit code indicating size of defect P0 code pattern P1 code pattern S Defect detection signal T Track UC Unit code

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tanio Urushitani, No. 1 Tanabe Shinden, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (72) Kenji Ozawa, 1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 within Fuji Electric Co., Ltd.

Claims (4)

[Claims] 1. A method of switching a data recording area of an optical disk storage device in which data is overwritten on a phase-change type recording medium, wherein a defect having an abnormally high light reflectance from a read signal of data and its size are detected. A defect detection circuit for detecting is provided, and when a defect larger than a predetermined size is detected by the defect detection circuit, the data recording area including the location of the defect is switched to another sector in the optical disk in sector units. A data recording area switching method for an optical disk storage device, comprising: 2. The method according to claim 1, wherein a sector including a defect is previously detected by a defect detection circuit before the first data is written on the optical disc, and a data recording area is set to a sector where the defect is detected. A method for switching a data recording area of an optical disk storage device, wherein the sectors in the optical disk other than the above are set in a consistent sector number order. 3. The method according to claim 1, wherein a defect in the optical disk is detected and stored by a defect detection circuit during a read / write operation of data during use of the optical disk storage device, and the defect is detected. A method for switching a data recording area of an optical disk storage device, characterized in that the sector is switched to a preset replacement sector in the optical disk when writing data to the optical disk. 4. The data of an optical disk storage device according to claim 1, wherein the defect detection circuit detects the size of the defect represented by the number of unit codes of the data recording code pattern. Recording area switching method.