JP3922012B2 - Optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk device, and more particularly to a technique for erasing data of a phase-change optical disk on which data has been recorded.
[0002]
[Prior art]
Conventionally, as a method for erasing a recorded optical disk on which data has already been recorded, two methods are known: (1) physical erase for performing DC erase, and (2) logical erase for overwriting a specific pattern. In the DC erase, the erase DC power optimized to such an extent that the recorded data cannot be reproduced by the drive reproduction system and the recording film is not destroyed by the overpower is irradiated a plurality of times. Data is erased and it takes time to erase. On the other hand, in the logical erase, since it is only necessary to overwrite a specific pattern, data can be erased more easily than in the physical erase.
[0003]
Japanese Patent Laid-Open No. 63-167428 shows an example of logical erase. In this prior art, it is described that a signal is generated according to a random number generated by a random number generator, and logical erasure is performed by overwriting the random number signal, and a continuous signal having a predetermined value is generated. It also describes performing logical erase by overwriting.
[0004]
[Problems to be solved by the invention]
However, even in the logical erase, the erasing speed is determined at the maximum speed for normally writing specific data, and there is a problem that it is difficult to achieve further high speed erasing.
[0005]
That is, in the phase change type optical disk, recording is performed by amorphization, and erasure is performed by crystallization. Therefore, when overwriting, the recorded data is crystallized and erased by erasing power, and is amorphized by recording power. However, if the rotational speed is increased to perform high-speed erasure, the relative speed between the optical disk and the laser light increases, and the temperature change becomes steep and the time required for crystallization is obtained. Instead, the recorded data remains unerased. Since logical erase is premised on overwriting with certainty, the rotational speed of the optical disk must be kept below a certain value in order to prevent the remaining recorded data from disappearing.
[0006]
On the other hand, in a write-once optical disc that cannot be erased as disclosed in Japanese Patent Laid-Open No. 5-290281, the pits are recorded overlapping with the already recorded pits, and the reproduced data is made different from the original recorded data. Although a method for disabling data reproduction has been proposed, when an optical disk is rotated at a high speed in order to perform high-speed erasure, duplicate pits are not recorded, and as a result, there is a possibility that unerasure remains.
[0007]
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an optical disc apparatus capable of erasing data at a higher speed than a phase change optical disc on which data has already been recorded. There is to do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an optical disc apparatus for recording on a phase change optical disc, and reproducing recorded data by recording a signal of a predetermined pattern on the portion of the optical disc on which data has already been recorded. the and having a signal recording means for logically impossible, and control means for shifting to the long side of the pulse width occurrence frequency distribution with respect to the pulse width frequency distribution of the time of data recording of the predetermined pattern.
[0009]
Here, it is preferable that the control means shifts the pulse width appearance frequency distribution of the predetermined pattern to the longer side as the recording speed of the optical disc increases.
[0010]
The present invention also relates to an optical disc apparatus for recording on a phase change optical disc, wherein a recorded signal is recorded on a portion of the optical disc on which data has already been recorded, so that reproduction of the recorded data is logically impossible. Signal recording means for controlling, and control means for making the shortest pulse width of the predetermined pattern larger than the shortest pulse width at the time of data recording.
[0011]
In this apparatus, it is preferable that the control means increases the shortest pulse width as the recording speed of the optical disc increases.
[0012]
In the apparatus of the present invention, the signal recording means can record the signal with a multi-pulse that repeats only the reproduction level and the recording level.
[0013]
It is also preferable to have a driving means for rotating the optical disc at a higher speed when recording the signal than when recording the data.
[0014]
As described above, in the present invention, a phase-change type optical disk such as a CD-RW or a DVD-RW is used to record a signal of a predetermined pattern having no meaning by utilizing the fact that recording by amorphization can be performed at high speed. Thus, the recorded data cannot be reproduced and high-speed erasure is performed. In conventional logical erase, erasing is performed by overwriting data. However, since it takes a physical time to crystallize the erase, an upper limit of the speed is defined. In this embodiment, the erase operation by such crystallization is performed. Since it is only necessary to record a predetermined pattern row that does not have any meaning per se, the erasing speed can be increased without being limited by the crystallization time. In the present invention, it can be said that a phase change type optical disk is used, and data is erased at high speed by amorphization instead of crystallization.
[0015]
On the other hand, if erasing is simply performed by amorphization, recording cannot be performed with high-speed rotation of the optical disc, and the original data remains unerased. In particular, with a pulse having a short time width such as 3T, the recording film of the optical disk cannot be heated to the melting temperature, and recording becomes impossible. Therefore, the pulse width appearance frequency is shifted to the long side to reduce the number of pulses having a short pulse width as much as possible, or the lower limit of the pulse width used for recording is increased to 5T, 9T, etc. instead of 3T (the shortest pulse width during data recording). By doing so, the signal can be reliably recorded and the original data can be erased even during high-speed rotation.
[0016]
Further, in the present invention, since data is erased without crystallization, even when a signal is recorded using a multi-pulse, the erase level required at the time of overwriting becomes unnecessary, and only the reproduction level and the recording level are required. From this point of view, the erasing speed can be increased.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, “data recording” means a normal recording operation, and “signal recording” or “signal pattern recording” means an erasing operation of already recorded data.
[0018]
FIG. 1 is a block diagram showing the configuration of the optical disc apparatus according to this embodiment. The optical disk 10 is rotationally driven by a spindle motor (SPM) 12. As the optical disk 10, a phase change optical disk such as a CD-RW or a DVD-RW is used. In these phase-change optical disks, the recording film is heated to the melting point by irradiating laser light of recording power, and then rapidly cooled to transition from the crystalline state to the amorphous state (amorphous state) to record data.
[0019]
The pickup 14 includes a laser diode (LD) unit that is disposed so as to face the optical disc 10 and performs recording and reproduction by irradiating the optical disc 10 with laser light. The LD unit is driven based on a signal from the LD control unit 16, and the LD control unit 16 drives the LD unit with a predetermined recording strategy by the strategy CIRC modulation unit 18. At the time of recording, recording data from a host computer (for example, a notebook personal computer) is received via the interface unit 24, and the received recording data is stored in the data buffer RAM 22 and then modulated by the modulation / demodulation unit 20. It is supplied to the strategy CIRC modulation unit 18. At the time of data reproduction, the reproduction RF signal from the pickup 14 is supplied to the modulation / demodulation unit 20, demodulated, and supplied to the host computer via the system controller 28 and the interface unit 24.
[0020]
Further, the pickup 14 is subjected to focus control and tracking control by the pickup servo unit 32, and recording and reproduction are performed in an in-focus state and an on-track state. A servo signal in the pickup servo unit 32 is generated based on a focus error signal and a tracking error signal obtained from the digital servo CIRC demodulation unit 36.
[0021]
The rotation speed of the spindle motor SPM 12 is controlled by the SPM servo unit 34.
[0022]
The system controller 28 controls the operation of each unit according to a control program stored in the memory 30. Specifically, based on a command received from the host computer via the interface 24, the modulation / demodulation unit 20 functions as a modulation unit during data recording, and the recording strategy in the strategy CIRC modulation unit 18 is adjusted. At the time of data reproduction, the data demodulated by the modulation / demodulation unit 20 functioning as a demodulation unit is received and transmitted to the host computer. On the other hand, in the present embodiment, the erasing of the recorded data is not an overwrite in which all the recorded data is erased and new data is overwritten as in the past, but a specific signal pattern is “recorded” on the existing portion of the recorded data. Is done. Therefore, when receiving an “erase” command from the host computer, the system controller 28 controls the strategy in the strategy CIRC modulation unit 18 to a specific pattern.
[0023]
The system controller 28 drives the SPM servo unit 34 and the SPM 12 at the time of data erasure, that is, at the time of signal pattern recording, and drives the optical disc 10 at a higher speed than at the time of normal data recording. Data erasure in this embodiment is not overwriting as in the prior art, but is merely recording a meaningless signal pattern, so there is no need to consider erasing by crystallization of recorded data, and it is faster than data recording. Can be realized. However, as the optical disk 10 is rotated at a higher speed, the laser power required for heating the recording film also increases, so that a specific condition is required for the signal pattern. This condition will be further described later.
[0024]
FIG. 2 shows an operation flowchart at the time of data erasure in the present embodiment. First, the system controller 28 receives a BLANK command from a host computer such as a notebook personal computer via the interface unit 24 (S101). This BLANK command is a command for requesting data erasure from the host.
[0025]
When the BLANK command is received, the system controller 28 controls the spindle motor SPM 12 to adjust the optical disc 10 to a predetermined recording speed N (S102). This recording speed is a speed at the time of normal data recording, and can be, for example, 10 times speed.
[0026]
Next, the modulation / demodulation unit 20 is set for data recording (S103), and an optimum recording power P is calculated by executing OPC (Optimum Power Control) (S104). In this OPC, a test pattern is recorded in a PCA area formed on the inner periphery of the optical disc 10 by changing the recording power, and the test pattern is reproduced to select the recording power that provides the best jitter or error rate. It is an operation to do.
[0027]
After the OPC is executed to calculate the optimum recording power P, the power required for the recording speed k · N at the time of erasing data is calculated (S105). As described above, since the system controller 28 drives the optical disc 10 at a higher speed during data erasing (erasing) than at the time of normal data recording, k> 1, for example, erasing at 40 × speed with k = 2. In some cases, the optimum recording power P determined by OPC is increased by 20%. This calculation can be performed based on a correlation equation between the rotation speed obtained in advance and the optimum recording power. Of course, the optimum recording power P at the recording speed k · N may be set by setting the rotation speed of the optical disk 10 to k · N in S102 and executing OPC in this state. However, since the OPC requires a certain time, the former processing is preferable from the viewpoint of high-speed erasure.
[0028]
After calculating the optimum recording power for erasing, the strategy CIRC modulation unit 18 is set for erasing (erase) (S106). This process is to set the recording strategy to a predetermined pattern. Specifically, the pulse width appearance frequency distribution of 3T to 11T (T is a bit length and 3T to 11T and 14T for DVD) at the time of data recording is long. This means shifting to the side (11T or 14T side). In general, when recording normal data, the 3T pulse width has the highest appearance frequency, and the appearance frequency decreases as the pulse width increases. However, in the present embodiment, as the predetermined pattern for erasure, the short pulse width appearance frequency distribution such as 3T and 4T is reduced, and conversely, the long pulse width appearance frequency such as 10T, 11T, and 14T is increased. In this process, a repetitive pattern of a reproduction level and a recording level is used as a recording strategy. That is, the signal pattern is recorded only with the reproduction level and the recording level without using the erase level.
[0029]
After the signal pattern is set, the SPM 12 is controlled to set the recording speed of the optical disc 10 to k · N (S107), the LD is driven with the set recording strategy, and the optical disc 10 is irradiated with the laser beam to form a predetermined pattern. Is recorded (S108). By this signal pattern recording, the already recorded significant data is logically rendered unreproducible.
[0030]
FIG. 3 shows an example of a recording strategy. FIG. 3A shows a recording strategy of this embodiment, and FIG. 3B shows a recording strategy at the time of normal data recording. As shown in (b), at the time of normal data recording, data is recorded with multi-pulses using three levels of power levels of a reproduction level Po, an erase level Pe, and a recording level Pr. That is, the data already recorded at the first erase level Pe is crystallized and erased, and the data is recorded at a plurality of subsequent recording levels Pr. On the other hand, in the strategy of this embodiment shown in (a), as described above, it is not necessary to crystallize and erase the recorded data, and only a meaningless pattern is recorded. A multi-pulse having a power Po and a recording power Pr can be obtained. By performing erasing by amorphization, high-speed erasing is possible, and by eliminating the erase power Pe, further high-speed erasing can be achieved.
[0031]
FIG. 4 shows the pulse width appearance frequency distribution of the signal pattern in the present embodiment. In the figure, the horizontal axis is the pulse width T, and in the case of CD, 3T to 11T exist as shown in the figure. In the case of DVD, it is 3T-14T. The vertical axis represents the appearance frequency of pulse widths of 3T to 11T. An alternate long and short dash line denoted by reference numeral 100 represents a frequency distribution during normal data recording, and the appearance frequency of 3T having a short pulse width is large and the appearance frequency of 11T having a long pulse width is small. On the other hand, solid lines indicated by reference numerals 102 and 104 are frequency distributions of the embodiment, and 6T to 11T are larger than 3T, 4T, and the like. This is because, in this embodiment, erasing is performed by making it amorphous, and a sufficient pulse width is secured to make it amorphous even at high speed rotation. That is, if the pulse width is short during high-speed rotation, the optical disk 10 cannot be amorphized by irradiating it with sufficient heat energy, and signals cannot be recorded. If the signal cannot be recorded, recorded data remains in that portion, and significant data can be reproduced. Therefore, a signal is surely recorded and data is erased by using many long pulse widths without using a short pulse width as a signal pattern.
[0032]
Reference numeral 102 denotes an appearance frequency distribution when k = 2 (20 times speed), and reference numeral 104 denotes an appearance frequency distribution when k = 4 (40 times speed). In the case of k = 4, a longer pulse width is required to make the recording film amorphous compared to the case of k = 2, and therefore the pulse width appearance frequency distribution is shifted to the longer side. It is noted that the pulse frequency appearance frequency of 3T is 0 when k = 2, whereas the pulse frequency appearance frequency shorter than 6T is 0 and only 7T to 11T exist when k = 4. I want.
[0033]
FIG. 5 specifically illustrates a signal pattern in the case of k = 2. Signal patterns include 9T (mark), 4T (space), 10T (mark), 4T (space), 11T (mark), 4T (space), 9T (mark), 4T ( Space), 10T (mark), ...
Also, as shown in (b), 10T (mark), 10T (space), 10T (mark), 10T (space),...
As described above, a 10T repeating pattern can be used. The mark means a portion where the recording film Pr is irradiated with the laser beam with the recording power Pr, and the space indicates a portion where the laser beam with the reproduction power Po is irradiated and the state transition does not occur.
[0034]
Thus, by recording a meaningless signal pattern on the optical disc 10, high-speed erasure becomes possible. Then, in a meaningless pattern, high-speed erasure is surely performed by reducing the appearance frequency of a short pulse width such as 3T and increasing the appearance frequency of a long pulse width such as 11T (or 14T). be able to.
[0035]
As the recording speed on the optical disk 10 increases, it becomes difficult to make amorphous, and therefore the appearance frequency distribution needs to be shifted to the longer side as the recording speed increases. It is preferable to change the pulse width according to the number of rotations of the optical disk 10.
[0036]
FIG. 6 shows the relationship between the rotational speed of the optical disc 10 and the shortest pulse width (lower limit T) used for signal recording. In the figure, the horizontal axis represents the number of rotations of the optical disc 10 and the vertical axis represents the lower limit T. When the rotational speed of the optical disk 10 is No (for example, equal speed), the lower limit T is set to 3T. However, the lower limit T is increased as the rotational speed becomes 2 × speed, 4 × speed, 10 × speed,. In the case of the rotational speed Nu, the lower limit T is set to 9T, and a signal is recorded using only a pulse width of 9T to 11T (9T to 14T in the case of DVD). As described above, the appearance frequency distribution of the pulse width equal to or higher than the lower limit T can be increased as the pulse width is longer, and the frequency of appearance of the pulse width equal to or higher than the lower limit T can be all the same. FIG. 7 shows a case where the appearance frequency distributions of pulse widths of 9T or more are the same.
[0037]
When a random number is simply used as the signal pattern, if the rotation speed of the optical disk 10 is increased, a signal with a short pulse width cannot be recorded, and as a result, there is a possibility that unerased residue may be generated. By increasing the lower limit T and recording a signal using only pulses whose time width is longer than a certain time, it is possible to prevent such disappearance.
[0038]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.
[0039]
For example, in the present embodiment, a multi-pulse that does not require the erase power Pe is used to achieve higher-speed erasure. Since the recorded data is erased by doing so, it is of course possible to erase the data using the strategy having the erase level Pe as shown in FIG.
[0040]
Further, in the present invention, it is only necessary to make the recorded data unreproducible by overwriting a signal pattern (erased data) of a predetermined pattern. Therefore, it is not always necessary to write the erased data continuously. The erasure data may be recorded on the.
[0041]
【The invention's effect】
As described above, according to the present invention, high-speed erasure can be performed on a phase change optical disk.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram of an embodiment.
FIG. 2 is a processing flowchart of the embodiment.
FIG. 3 is an explanatory diagram of a recording strategy of the embodiment.
FIG. 4 is an explanatory diagram of a pulse width appearance frequency distribution according to the embodiment.
FIG. 5 is an explanatory diagram of a signal pattern according to the embodiment.
FIG. 6 is a graph showing the relationship between the optical disc rotation speed and the pulse width lower limit value according to the embodiment.
FIG. 7 is an explanatory diagram of another pulse width appearance frequency distribution according to the embodiment.
[Explanation of symbols]
10 optical disk, 12 spindle motor (SPM), 18 strategy CIRC modulator, 20 modulator / demodulator, 28 system controller.

Claims (6)

An optical disk device for recording on a phase change optical disk,
A signal recording means for logically disabling the reproduction of the recorded data by recording a signal of a predetermined pattern on a portion of the optical disk on which data has already been recorded;
Control means for shifting the pulse width appearance frequency distribution of the predetermined pattern to the longer side with respect to the pulse width appearance frequency distribution at the time of data recording,
An optical disc apparatus comprising: The apparatus of claim 1.
The optical disc apparatus characterized in that the control means shifts the pulse width appearance frequency distribution of the predetermined pattern to the longer side as the recording speed of the optical disc increases. An optical disk device for recording on a phase change optical disk,
A signal recording means for logically disabling the reproduction of the recorded data by recording a signal of a predetermined pattern on a portion of the optical disk on which data has already been recorded;
Control means for making the shortest pulse width of the predetermined pattern larger than the shortest pulse width at the time of data recording;
An optical disc apparatus comprising: The apparatus of claim 3.
The optical disc apparatus, wherein the control means increases the shortest pulse width as the recording speed of the optical disc increases. In the apparatus in any one of Claims 1-4,
The optical disc apparatus characterized in that the signal recording means records the signal by a multi-pulse that repeats only a reproduction level and a recording level. The apparatus according to any one of claims 1 to 5, further comprising:
Drive means for rotationally driving the optical disc at a higher speed than during the data recording during the signal recording;
An optical disc apparatus comprising:

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