KR100295476B1 - Recording medium, reproducing apparatus thereof, and apparatus and method for reproducing data - Google Patents

Abstract

Data recorded on the optical disc is read by optical pickup, waveform equalization processing is performed by a waveform equalizer, and then demodulated through a data slicer. An optical disc has recorded thereon parameters for obtaining waveform equalization characteristics that are optimal for reading the recorded data. The demodulated parameter is decoded by the data processor, which switches the waveform equalization characteristics of the waveform equalizer based on the content of the parameter.

Description

Recording medium, its reproducing apparatus, data reproducing apparatus and data reproducing method {RECORDING MEDIUM, REPRODUCING APPARATUS THEREOF, AND APPARATUS AND METHOD FOR REPRODUCING DATA}

The present invention relates to a recording medium on which digital data such as compressed moving image data, sub-picture data and audio data is recorded, a reproducing apparatus for reproducing the recording medium, a data reproducing apparatus for reproducing the data, and a data reproducing method. In particular, it relates to the automatic control of the playback state to the best state.

As is known, conventional optical discs are spreading, for example, compact discs dedicated to music, laser discs corresponding to moving images, and the like.

On the other hand, recently, moving image data, audio data, and video data (e.g., subtitle data) and the like are compressed and recorded on an optical disc having the same radius as the above-mentioned CD, and different languages are used for audio and subtitles. Have been recorded in various types, and a system has been developed in which audio and subtitles of a desired language can be freely selected and reproduced at the time of reproduction. Optical discs corresponding to this type of system are generally referred to as DVDs.

As such, there have been various optical discs. The reproducing apparatus for reproducing such an optical disc has a rotary servo unit for rotating control of the optical disc, an optical pickup unit for reading out a modulated signal recorded on the optical disc by irradiating a laser beam to the signal recording surface of the optical disc and detecting the reflected light. .

The modulated signal read out by this optical pickup section is first input to a waveform equalization circuit and subjected to waveform equalization processing. The waveform equalized signal is supplied to the error correction circuit, subjected to error correction processing, and guided to the demodulation circuit for demodulation.

In a conventional optical disc reproducing apparatus, the waveform equalizing circuit is characterized. The reason for this is that it is assumed that the optical disc and the reproduction apparatus for reproducing the disc are in one-to-one correspondence.

In reality, however, optical discs of different types exist as described above. For this reason, when the optical disc reproducing apparatus is equipped with an optical disc of a different type from the original corresponding optical disc, and the optical disc is reproduced, the characteristics of the modulation signal obtained from the optical pickup section are completely out of the characteristics intended by the reproducing apparatus. There may be a case. In such a case, the user may be mistaken for the failure of the optical disc reproducing apparatus or the defect of the optical disc.

In addition, even with optical discs of the same standard, various parameters do not necessarily satisfy the standard ideally due to the image of the manufacturer of the optical disc or the characteristic change of the optical disc reproducing apparatus. As a result, in an optical disc reproducing apparatus, an ideal modulated signal may not be obtained. In this case, the probability of a data error becomes high, and a good reproduction signal cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a recording medium, a reproducing apparatus, a data reproducing apparatus, and a data reproducing method which can automatically set the most suitable characteristics according to the type of optical disc.

1 is a block diagram showing the whole of an optical disc reproducing apparatus, showing a second embodiment of the present invention.

Fig. 2 is a block diagram showing the pickup servo means of the second embodiment.

Fig. 3 is a block diagram showing a main part of the second embodiment.

4A and 4B are diagrams for explaining an example of the operation of the second embodiment, respectively.

5A and 5B are diagrams for describing another operation example of the second embodiment, respectively.

6A to 6C are views showing, in principle cross-section, the structure of various optical discs, respectively.

7A to 7C are enlarged perspective views showing signal recording surfaces of various optical discs, respectively.

8 is a characteristic diagram showing a level change of a focus error signal.

Fig. 9 is a diagram showing a recording data structure of an optical disc as an example of a recording medium to which the present invention is applied.

Fig. 10 is a diagram showing a logical structure of data recorded on the same optical disc.

Fig. 11 is a block diagram showing the whole of the optical disc reproducing apparatus, showing the second embodiment of the present invention.

Fig. 12 is a configuration diagram showing details of the optical pickup section, the preamplifier and the error signal generation section in the same second embodiment.

13 is a flowchart showing the operation of the error correction unit in the same second embodiment.

14 is a flowchart showing the operation of the same second embodiment.

Fig. 15 is a block diagram showing details of main parts of the same second embodiment.

Fig. 16 is a flowchart showing operation of the modification of the same second embodiment.

17 is a characteristic diagram for explaining another modification of the same second embodiment.

18 to 21 are flow charts showing the operation of the same or different modifications.

<Description of Symbols for Main Parts of Drawings>

11: optical disc

12: disc motor

21: optical pickup

22: preamplifier

23: waveform equalizer

24: slicer

25: data extraction unit

26: error correction circuit

27: sync signal separator

28: spindle servo circuit

The recording medium according to the present invention is such that a part of the recording data includes a parameter capable of obtaining at least waveform equalization characteristics which become a standard for reading the recording data.

The recording medium according to the present invention further includes a pickup section for reading data recorded in the data recording area, a waveform equalizer for performing waveform equalization processing on the high frequency modulated signal output from the pickup section, and an output signal of the waveform equalizer. The data recorded in the data recording area is reproduced by a reproducing apparatus having a demodulation unit for performing a demodulation process. In the data recording area, parameters indicating the recording form of the data recorded in the data recording area are recorded. Based on the contents of the demodulated parameters, the waveform equalizer switches the waveform equalization characteristics.

Further, the reproducing apparatus according to the present invention reproduces the recorded recording medium including at least a parameter for obtaining waveform equalization characteristics that are most suitable for reading the recording data to a part of the recording data, and reproducing the recording data from the recording medium. A pickup unit for reading, a waveform equalizer for performing waveform equalization on the high frequency modulated signal output from the pickup unit, a demodulator for demodulating the output signal of the waveform equalizer, and a parameter demodulated in the demodulator Based on the content, the control means which switches the waveform equalization characteristic of a waveform equalizer is provided.

In addition, the reproducing apparatus according to the present invention includes a pickup section for reproducing a recording medium recorded with a part of the recording data including a parameter indicating a recording form of the recording data, and reading the recording data from the recording medium; A waveform equalizer for performing waveform equalization on the high frequency modulated signal output from the demodulator, a demodulator for demodulating the output signal of the waveform equalizer, and a type of recording medium based on the contents of the demodulated parameters in the demodulator. A discriminating unit for discriminating is provided.

According to the above configuration, when the recording medium is reproduced, the control direction of the reproduction characteristics, the selection of the reproduction characteristics, or the type or recording characteristics of the recording medium can be determined based on the contents of the parameters, so that the most suitable signal reproduction characteristics Can be built early.

In addition, the data reproducing apparatus according to the present invention performs a waveform equalization process on an input high frequency modulated signal, and a binary equalizer capable of selectively switching a plurality of waveform equalization characteristics, and a binarization for binarizing the output signal of the waveform equalizer. Section, an error correction section for detecting an error of an output signal of the binarization section and performing an error correction process, an error occurrence rate detection section for obtaining information on the occurrence rate of the error detected by the error correction section, and an error obtained by the error occurrence rate detection section. On the basis of the occurrence rate information, control means for switching the waveform equalization characteristics of the waveform equalizer is provided.

Further, the data reproducing method according to the present invention performs a waveform equalization process on the input high frequency modulated signal, and selectively converts a plurality of waveform equalization characteristics, and binarizes the waveform equalized signal in this waveform equalization step. An error occurrence rate detection step of detecting an error of the binarized signal in this binarization step to obtain information on the occurrence rate of the error, and waveform equalization based on the occurrence rate information of the error obtained in the error occurrence rate detection step. A control step of switching the waveform equalization characteristics of the step is included.

According to the above configuration and method, the most suitable waveform equalization characteristic according to the error occurrence rate of the input data can be obtained, and the data reproduction capability can be improved.

Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 shows the overall configuration of the optical disc reproducing apparatus explained in this second embodiment. That is, in Fig. 1, reference numeral 11 denotes an optical disc, and is rotated by the disc motor 12. The optical pickup section 21 is disposed on the signal recording surface side of the optical disc 11. The optical pickup 21 is controlled to move in the radial direction of the optical disk 11 by a pickup transport motor (not shown).

The high frequency modulated signal output from the optical pickup section 21 is input to the waveform equalizer 23 through the preamplifier 22 and subjected to waveform equalization. This waveform equalized modulated signal is input to the data slicer 24 and binarized. This binarized signal is supplied to the data extraction section 25. This data extraction section 25 includes a data synchronization clock generator using a phase locked loop (PLL) circuit.

For this reason, in the data extraction part 25, a data clock is generated and a modulated signal is sampled using this data clock. As a result, the data extraction section 25 extracts the digital data recorded on the optical disc 11. The extracted digital data is supplied to an error correction circuit (ECC) 26 and a synchronization signal separator 27 that separates the synchronization signal, respectively.

The data clock reproduced by the data extraction section 25 and the synchronization signal obtained by the synchronization signal separator 27 are input to the spindle servo circuit 28. The spindle servo circuit 28 inputs a synchronization signal synchronized with the data clock, and controls the rotation speed of the disk motor 12 based on the frequency and phase of the synchronization signal. In this case, the spindle servo circuit 28 performs the rotational speed control of the disk motor 12 so that the synchronization signal of a predetermined frequency is obtained from the synchronization signal separator 27 in the state where normal reproduction is being performed.

In Fig. 1, reference numeral 29 denotes a data processor, which controls the slice level of the data slicer 24, the characteristics switching and control of the PLL circuit in the data extraction section 25, the spindle servo circuit 28, and the synchronization. Switching control of the operation timing of the signal separator 27, output control of the error correction circuit 26, and the like are performed. In particular, the data processor 29 performs the characteristic control of the waveform equalizer 23 as described later.

The optical disc reproducing apparatus is also provided with pickup servo means for the optical pickup section 21. The pickup servo means processes the error signal generated by the focus error detector 31, the 3-beam tracking error detector 32, the phase difference tracking error detector 33, and the detectors 31, 32, and 33 by And a servo signal processor 34 for obtaining a control signal for each error correction. The control signal obtained from this servo signal processing section 34 is supplied to the optical pickup section 21 through the amplifier 34a.

2 shows the configuration of the focus error detector 31, the 3-beam tracking error detector 32, and the phase difference tracking error detector 33 constituting the pickup servo means. That is, FIG. 2 shows the arrangement of the photodetectors A to F constituting the photodetector section of the optical pickup section 21, the interior of the preamplifier 22, and the error detection sections 31, 32 and 33. FIG.

In this example, the photodetector is composed of four-segment photodetectors A, B, C, and D, and two photodetectors E, F arranged before and after. Ideally, the central reflected beam is received at equal proportions (areas) on each of the light receiving surfaces of the four-segment photodetectors A, B, C, and D. In the good tracking state, the reflected beams corresponding to each of the front and rear photodetectors E and F are equally received.

The outputs of the photodetectors A to F are input to the buffer amplifiers 22a to 22f, respectively. Among these, the outputs A and C of the buffer amplifiers 22a and 22c are added to the adder 35 and output as an (A + C) signal. The outputs B and D of the buffer amplifiers 22b and 22d are added to the adder 36 and output as a (B + D) signal.

The outputs of the adders 35 and 36 are inputted to the subtractor 37, respectively, to perform arithmetic processing of (A + C)-(B + D), thereby generating a focus error signal. This focus error signal is input to an S-shaped level detection circuit (not shown) provided in the focus error detection unit 31 and contributes to the detection of the focus state. This detection operation will be described later.

In addition, each output of the adders 35 and 36 is input to the phase difference detector 38. The phase difference detector 38 detects the phase difference between the (A + C) signal and the (B + D) signal. This detection signal is used as a phase difference tracking error signal. This phase difference tracking error signal is used as a valid signal when the DVD is reproduced.

Each output of the buffer amplifiers 22e and 22f is subtracted by the subtractor 39, thereby generating an (E-F) signal. This (E-F) signal is used as a three beam tracking error signal. This three-beam tracking error signal is used as a valid signal when the CD is reproduced.

In addition, each output of the buffer amplifiers 22a, 22b, 22c, and 22d is added to the adder 41, thereby generating an (A + B + C + D) signal. This (A + B + C + D) signal is supplied to the waveform equalizer 23 as an RF (Radio Frequency) signal.

3 illustrates one of the features of the present invention. In FIG. 3, the same code | symbol is attached | subjected to the same part as FIG. That is, the outputs of the four-part photodetectors A, B, C, and D of the optical pickup section 21 are added by the adder 41 and input to the waveform equalizer 23. Here, the waveform equalizer 23 can switch to at least two waveform equalization characteristics. The switching of the waveform equalization characteristics is realized by switching either or both of the delay characteristics and the amplitude characteristics. In Fig. 3, characteristics 1, 2, 3,. It is shown as

In the switching of the waveform equalization characteristic, the most suitable characteristic is selected by the data processor 29 determining the data from the data slicer 24 or the reproduction data after the error correction is performed.

As a means of this most suitable characteristic, there exist various embodiment as follows. FIG. 4: A has shown the progress of operation | movement at the time of selecting the most suitable characteristic. First, when the optical disc reproducing apparatus starts reproducing the optical disc 11, the optical pickup section 21 is moved to a predetermined position so that the rotation speed of the disc motor 12 is automatically set at a predetermined speed.

In addition, the waveform equalization characteristic of the waveform equalizer 23 is also set to a predetermined characteristic. The optical system of the optical pickup section 21 and the predetermined beam characteristics are also set to predetermined characteristics, respectively. In addition, the data sampling clock in the data processor 29 is also set to a predetermined frequency.

Here, there is a convention between the optical disc 11 and the optical disc reproducing apparatus. That is, in the optical disc 11, if it is rotated at a predetermined speed and is set to a predetermined waveform equalization characteristic and a predetermined beam characteristic, an optical disc of any kind (for example, DVD1 in a one-layer structure or DVD2 in a two-layer structure) is provided. Even in (11), a recording area (for example, a lead-in area) in which a signal can be read is provided, and parameters indicating the type of the optical disc 11 are recorded in this area (see Fig. 4B).

The data processor 29 determines that the loaded optical disc 11 is DVD1 having a one-layer structure if the parameter read out from the area is repeated, for example, "1000". If the data processor 29 repeats with "1100", the data processor 29 has a DVD2 having a two-layer structure. It is programmed to determine. Further, if the parameter is repeated at &quot; l100 &quot;, it can be determined to be DVD2, and otherwise, it can be determined to be DVD1.

In this way, the data processor 29 can determine whether the optical disc 11 during reproduction is DVDl or DVD2. For this reason, the data processor 29 can set the rotational speed of the disk motor l2 to the speed suitable for the optical disk 11 on which it is mounted. In addition, the data processor 29 can convert the internal characteristics of the waveform equalizer 23 into the characteristics for DVD1 or DVD2.

The above parameter may be a specific parameter indicating the relationship, for example, the ratio between the recording bit clock frequency of the recording data and the spatial frequency when the optical pickup unit 21 reads the recording data. In this case, the data processor 29 is programmed to automatically set the characteristics of each part, such as an optical system and a signal processing system, in accordance with the contents of this parameter.

For example, there are two types of DVD-R0M and DVD-R having a linear density of 0.267 µm / bit and 0.293 µm / bit with respect to the data recording density. "0000" is recorded as a parameter on a DVD having a linear density of 0.267 µm / bit, and "0001" is recorded as a parameter on a DVD having a linear density of 0.293 µm / bit.

Therefore, when the read parameter is "0000", the data processor 29 judges that the DVD has a linear density of 0.267 µm / bit, and when the read parameter is "0001", the DVD has a linear density of 0.293 µm / bit. It determines and automatically changes the characteristic of each part, such as an optical system and a signal processing system.

Some DVD-RAMs have a linear density of 0.409 to 0.435 µm / bit with respect to the data recording density, and "0010" is recorded as the parameter. The reason why the linear density has a width of 0.409 to 0.435 µm / bit is that the DVD-RAM adopts the ZCLV (Zone Constant Linear Velocity) method.

5A and 5B show an example in which the second embodiment is developed. That is, when the type of the optical disc 11 is determined, the data processor 29 can set the rotational speed of the disc motor 12 to a speed suitable for the mounted optical disc 11 as in the previous example. In addition, the data processor 29 can switch and set the internal characteristics of the waveform equalizer 23 to the characteristics for DVD1 or DVD2.

In this example, the characteristics of the waveform equalizer 23 are finely adjusted after setting the characteristics of each part to the characteristics corresponding to the optical disc 11 being reproduced. Firstly, in the second example, the characteristics of the waveform equalizer 23 are a1, a2, a3,... In this case, the characteristics are obtained, for example, to obtain the highest reproduction level. For example, if the highest reproduction level is obtained when the characteristic a2 is obtained, the characteristic a2 is adopted as the characteristic of the waveform equalizer 23. Although the switching of this characteristic is described only in the column on the DVD1 side in Fig. 5A, the same applies to the case where the DVD2 is played back.

In the second example, a plurality of parameters, for example, for obtaining fine waveform equalization characteristics, are recorded in a part of the recording data of the DVD2. The contents of the parameters which can be read best among the plurality of parameters are determined, and the waveform equalization characteristics according to the contents are set.

For example, three parameters Xl, X2, and X3 with slightly different frequency of the bit clock are recorded on the disk. By the waveform equalization characteristic set once, the instruction content for setting a normal waveform equalization characteristic is shown to the parameter which has little noise and read at least in the best state.

In other words, when the parameter X2 is normally read, the waveform equalization characteristic currently set is the best. In addition, when parameter X1 is read normally, it is assumed that the currently set waveform equalization characteristic is shifted from the normal waveform equalization characteristic to the higher side (upper side) on the frequency axis. Similarly, when parameter X3 is read normally, it is assumed that the waveform equalization characteristic currently set is shifted to the lower side (lower side) on the frequency axis from the normal waveform equalization characteristic.

For this reason, the command to adjust the current waveform equalization characteristic to the lower side is described in the parameter X1, and the command to adjust the current waveform equalization characteristic to the higher side is described in the parameter X3.

In the above description, after determining the type of the optical disc 11, fine waveform equalization characteristics are determined, and the characteristics are adjusted. However, for example, in the case of the optical disc reproducing apparatus in which it is determined from the beginning that DVD2 is to be mounted, the above-described second example process can be executed immediately.

In other words, for example, a plurality of parameters for recording fine waveform equalization characteristics are recorded in a part of the recording data of DVD2. The contents of the parameters that can be read most appropriately among the plurality of parameters are determined, and the waveform equalization characteristics according to the contents are set.

In the system composed of such an optical disc 11 and its reproducing apparatus, not only parameters for setting waveform equalization characteristics, but also parameters for changing characteristics of each part are recorded on the optical disc 11, so that this parameter is recorded on the reproducing apparatus side. You can switch each part. Examples of switching objects in this case include a compensation amplifier and a signal processing mode.

In the second embodiment described above, when the parameters are recorded on the optical disc 11 itself, and the parameters are read and decoded, setting data for setting the reproduction characteristics most suitable for the optical disc 11 can be obtained.

Next, the structure of the optical pickup section 11 which is presently mixed will be described. 6A to 6C show cross sections of various optical discs 11 in principle. First, Fig. 6A shows a conventional music CD, and its thickness is defined as 1.2 mm.

6B and 6C show a DVD in which a high-density recording is realized to record a video code and an audio code in which data is compressed, and includes a high-density optical disc capable of recording and reproducing. That is, this DVD includes a so-called read-only memory (DVD-ROM) and a recordable DVD-RAM (Read After Memory).

6B shows a DVD of a one-layer structure composed of one substrate on which a signal recording surface is formed. 6C shows a two-layer DVD-ROM formed by adhering two substrates each having a signal recording surface. In either case, the thickness of the entire optical disc 11 is 1.2 mm, and the thickness of the substrate is defined as 0.6 mm. In addition, both CDs and DVDs are equally defined with a diameter of l2cm / 8cm.

7A to 7C show the signal recording surface of the above-described optical disc 11 in an enlarged manner. FIG. 7A shows the structure of the signal recording surface of the CD, FIG. 7B shows the structure of the signal recording surface of the DVD-R0M, and FIG. 7C shows the structure of the signal recording surface of the DVD-ROM.

7A to 7C also show dimensions such as the thickness, bit width, track width, and the like of the disk substrate. In this way, the optical disc 11 may have a different track pitch, and may have a different recording format.

Next, the focus servo will be described. That is, the focus error signal is supplied to the S-shaped level detection circuit of the focus error detector 31. This S-shaped level detection circuit detects that the level of the focus error signal changes as shown in Fig. 8 in accordance with the focus state.

The level information detected by this S-shaped level detection circuit is input to the servo signal processor 34. The servo signal processing unit 34 then performs focus servo on the optical system of the optical pickup 21 based on the input level information.

The S-shaped detection level information can also be used as a material for judging the type of the optical disc 11. In this case, after determining the type of the optical disc 11 by the S-shaped detection level information, it is possible to obtain final confirmation by the preceding parameter.

That is, in order to judge the type of the optical disc 11 based on the S-shaped detection level information, the optical disc 11 such as a CD or DVD having a one-layer structure as described above, and a DVD-ROM or DVD-RAM having a two-layer structure are described. The optical disc 11 uses a different reflectance when light beams are irradiated.

That is, the reflectance of the light beam is about 60 to 70% in the optical disk 11 such as a CD or DVD having a one-layer structure, and 25 to 30% in the optical disk 11 such as a DVD-ROM having a two-layer structure. In an optical disc 11 such as a DVD-RAM having a structure, the ratio is 20% or less.

For this reason, for example, when the focus error signal is at a high level, it can be determined that an optical disc 11 such as a CD or a DVD having a one-layer structure is mounted. When the focus error signal is a low FP bell, a two-layer DVD-ROM is used. Alternatively, it can be determined that an optical disc 11 such as a DVD-RAM is mounted.

In addition, in order to determine whether the optical disk 11 of the one-layer structure or the optical disk 11 of the two-layer structure, the objective lens (not shown) built in the optical pickup section 21 is gradually brought closer to the optical disk 11, and the focus is reached. The number of times the confocal point determined from the error signal may be used.

When the determination is made by this means, the optical disc 11 is stopped without rotation, without being rotated by the rotation servo system of the optical disc 11 through the spindle servo circuit 28, or is forced to slowly or less than half a rotation or constant. It is preferable to rotate. The reason is that there is a risk of runaway using the rotary servo system.

In addition, as the rotational speed when the optical disk 11 is slowly rotated constantly, the minimum rotational speed when the rotational speed of the optical disk 11 is controlled by CLV (Constant Linear Velocity) or the minimum rotational speed of the optical disk 11 assumed is assumed. It is requested. Such a control method of the rotational speed is performed in the same manner even when a tracking error signal described later is used for discriminating the optical disc 11.

9 shows the recording data structure of the optical disc 11 as an example of a recording medium to which the present invention is applied. The optical disk ll is, for example, a double-sided adhesive disk having a storage capacity of about 5G bytes on one side, and a plurality of recording tracks are arranged between the lead-in area on the inner circumference side and the lead-out area on the outer circumference side. Each track is composed of a plurality of logical sectors, and various pieces of information (compressed digital data) are stored in each sector.

FIG. 10 shows the data structure of a video (video) file recorded on the optical disc 11 shown in FIG. As shown in FIG. 10, this video file includes file management information 1 and video data 2. The video data 2 includes a video data unit (block), an audio data unit (block), a sub-picture data unit (block), and information NAV (DSI; Data Search Information and PCI) necessary for controlling the reproduction of these data. NAV unit (block) for recording Picture Control Information.

Each unit is divided into, for example, packets of a certain data size for each type of data. The video data unit, audio data unit and sub-picture data unit are reproduced in synchronization with each other based on the NAVs arranged immediately before these unit groups.

That is, a system area for storing system data used for reproducing the optical disc 11, a volume management information area, and a plurality of file areas are formed in the aggregate of the plurality of logical sectors shown in FIG.

Among the plurality of file areas, for example, the file 1 is composed of main video information (video data in the drawing), sub-video information (sub-picture data in the drawings), and audio having auxiliary contents for the main video as shown in FIG. Information (audio data in the figure), reproduction information, and the like.

Since the NAV unit has a data recording space (storage unit), parameters can be newly described in this storage unit. As described above, since the NAV unit is described in plural places (the outer circumferential side and the inner circumferential side) of the optical disc 11, it is necessary to provide several checkpoints and describe various parameters for system check in the NAV unit at this position. It becomes possible.

This parameter may be information specifying waveform equalization characteristics as well as information for controlling the rotational speed of the disc motor 12. In this way, it is always possible to set the reproduction state of the optical disc reproducing apparatus to a state most suitable for the optical disc 11.

According to the second embodiment described above, since the reproduction output state of at least the modulated signal recorded on the optical disc 11 can be identified, the type of the optical disc 11 can be discriminated. In addition, when the modulated signal recorded on the optical disc 11 is read, at least the reproduction characteristic of the modulated signal can be obtained closer to the ideal characteristic. In addition, the reproduction state of the optical disc reproducing apparatus can be maintained in the best state by utilizing the parameters of the optical disc ll.

Next, a second embodiment of the present invention will be described. That is, in Fig. 1L, reference numeral 51 denotes an optical disc and is rotationally driven by the disc motor 52. The optical pickup section 53 is disposed on the signal recording surface side of the optical disk 51. The optical pickup section 53 is controlled to move in the radial direction of the optical disk 51 by a pickup transport motor (not shown).

The high frequency modulated signal output from the optical pickup section 53 is input to the waveform equalizer 55 through the preamplifier 54 and subjected to waveform equalization. This waveform equalized modulated signal is input to the data slicer 56 and binarized. This binarized signal is supplied to the data extraction section 57. This data extraction section 57 includes a data synchronization clock generator using a phase locked loop (PLL) circuit.

For this reason, in the data extraction section 57, a data clock is generated and a modulated signal is sampled using this data clock. As a result, the data extraction unit 57 extracts the digital data recorded on the optical disc 51. The extracted digital data is supplied to a sync detection / demodulation section 58 including an error correction circuit (ECC), a sync signal separator for separating sync signals, a demodulator for converting a modulated signal into an original bit string, and the like.

The output of the synchronous detection / demodulation section 58 is input to the error correction section 59, and error correction processing is performed by a predetermined method. The serial data subjected to this error correction processing is input to the data processing unit 60 so as to perform data separation processing, decoding processing, and the like.

The data clock in the data processing unit 60, the synchronization signal of the synchronization detection / demodulation unit 58, and the like are input to the disk servo circuit 61. The disk servo circuit 61 inputs a synchronization signal synchronized with the data clock, and controls the rotation speed of the disk motor 52 based on the frequency and phase of the synchronization signal. And this disc servo circuit 61 controls the rotation speed of the disc motor 52 so that the synchronous signal of predetermined frequency and phase may be acquired when normal reproduction is performed.

In addition, the output of the preamplifier 54 is input to the error signal generator 62. As described later, the error signal generation unit 62 uses the output signal from the photoelectric conversion element built in the optical pickup unit 53, and each servo system such as a focus servo, a phase difference tracking servo and a three beam tracking servo. A focus error signal, a phase difference tracking error signal, and a three beam tracking error signal are generated, which are suitable for.

Among these, the focus error signal is supplied to the focus servo circuit 63, and the phase difference tracking error signal and the three beam tracking error signal are input to the tracking servo circuit 64. The output of this circuit 63 is supplied to the focus driver of the optical pickup unit 52. Moreover, the output of the tracking servo circuit 64 is supplied to the tracking drive part of the optical pickup part 53, and is also supplied to the pickup feed motor drive part 65. As shown in FIG.

This pick-up feed motor drives the optical pickup 53 to move in the radial direction of the optical disc 51, and is driven when tracking control is performed or during jump operation. The optical pickup unit 53 is supplied with an NA switching signal for controlling the numerical aperture NA in a disc type discrimination circuit (not shown).

By this NA switching signal, the lens is switched when the optical pickup unit 53 is provided with the two lens switching method (two optical lens systems are prepared), and the adjustment aperture is switched when the adjustment switching method is performed. . In addition, in the case of the optical focusing section 53 in the case of a two-focal lens system (two focal points exist in the optical axis direction), switching is not particularly necessary.

12 shows the configuration of the photoelectric conversion element of the optical pickup section 53 and the error signal generator 62 for obtaining the focus error signal, the phase difference tracking error signal, and the three beam tracking error signal. That is, FIG. 12 shows the arrangement of the photodetectors A to F which are the photoelectric conversion elements of the optical pickup section 53, the interior of the preamplifier 54, and the interior of the error signal generator 62.

In this example, the photoelectric conversion element is composed of four-segment photodetectors A, B, C, and D, and two photodetectors E and F arranged before and after. Ideally, the central reflected beam is received at equal proportions (areas) on each of the light receiving surfaces of the four-segment photodetectors A, B, C, and D. Further, in the good tracking state, the corresponding reflected beams are equally received by the front and rear photodetectors E and F, respectively.

The outputs of the photodetectors A to F are input to the buffer amplifiers 54a to 54f, respectively. Among these, the outputs A and C of the buffer amplifiers 54a and 54c are added to the adder 66 and output as (A + C) signals. The outputs B and D of the buffer amplifiers 54b and 54d are added to the adder 67 and output as a (B + D) signal.

The outputs of the adders 66 and 67 are input to the subtractor 68, respectively, and are taken out as a focus error signal by performing arithmetic processing of (A + C)-(B + D). This focus error signal is input to an S-shaped level detection circuit (not shown) provided in the focus servo circuit 68 to contribute to the detection of the focus state.

In addition, each output of the adders 66 and 67 is input to the phase difference detector 69. The phase difference detector 69 detects the phase difference between the (A + C) signal and the (B + D) signal. This detection signal is used as a phase difference tracking error signal. This phase difference tracking error signal is used as a valid signal when the DVD is reproduced.

In addition, each output of the buffer amplifiers 54e and 54f is subtracted by the subtractor 70 to generate an (E-F) signal. This (E-F) signal is used as a three beam tracking error signal. This three-beam tracking error signal is used as a valid signal when the CD is reproduced.

In addition, each output of the buffer amplifiers 54a, 54b, 54c, 54d is added to the adder 71 to generate an (A + B + C + D) signal. This (A + B + C + D) signal is supplied to the waveform equalizer 55 as an RF signal.

Here, referring back to FIG. 11 again, the error occurrence state of the error correcting unit 59 is monitored by the error rate detecting unit 72. The error rate detection unit 72 switches the waveform equalization characteristics of the waveform equalizer 55 in accordance with the detected error rate. In addition, the error rate detected by the error rate detection unit 72 is also useful for switching the characteristics of other parts.

13 shows the processing of the error correction unit 59. First, the error correction unit 59 inputs data of one frame (for one block) of the demodulation signal based on the synchronization signal (step A1), and executes error processing line by line using an error check word. After the error checking processing of each row is finished, error checking processing of each column is executed (step A2). As a result, the error correction unit 59 can obtain information about the number of occurrences of the error and the error position.

If error correction is possible, the error correction unit 59 performs an error correction process (steps A3 and A4), and determines whether all error correction processes have been completed for one block of data to be corrected ( Step A5). When all error correction processing is not completed for one block, the error correction unit 59 performs error detection and correction on the next row or column. When all error checking and correction for one block is completed, data of the next block is input.

If error correction is not possible in step A3, the error correction unit 59 describes the flag in correspondence with the row or column determined to be impossible (step A6). This flag is stored in the management memory. Then, a determination is made as to whether or not the inspection for one block has ended (step A7), and when it is finished, the error correction unit 59 inputs the next block data, and if not, the inspection of the next row or column. Go to processing.

As described above, the error checking and correction processing is performed for each block, but the information on the number of flags and the error position (error number) is monitored by the error rate detection unit 72. The error rate detected by the error rate detection unit 72 contributes to controlling the switching of the characteristics of each part of the optical disc reproducing apparatus.

14 shows the procedure of the control operation of the error rate detection unit 72. That is, when the optical disc reproducing apparatus is started, the error rate detecting unit 72 determines whether the reproduction elapsed time TN has elapsed for a predetermined time T1 (step B1). This is because the error rate of data is high at the start of the optical disc reproducing apparatus.

Thereafter, the error rate detection unit 72 determines whether the flag number FN for the plurality of blocks for which the error correction is performed is equal to or greater than the predetermined number F1 (step B2). Since the flag is generated when there is a point where error correction is impossible, the numerical aperture NA may not match when the flag number is F1 or more. Thus, the error rate detection unit 72 switches the numerical aperture NA (step B3) and proceeds to the processing of step B1.

If the reproduction elapsed time TN has passed the predetermined time Tl, the error rate detection unit 72 proceeds to step B4 and again determines whether the flag number FN for the plurality of blocks is equal to or greater than the predetermined number F1. During normal playback after the predetermined time T1 has elapsed, if the flag number FN is equal to or greater than the predetermined number Fl, the error rate detection unit 72 is often caused, for example, because an abnormality occurs in the optical disc 51. Executes warning on / off (steps B5 and B6).

When the flag number FN is equal to or less than the predetermined number Fl, in step B7, the error rate detection unit 72 determines whether the error number EN for the plurality of blocks is equal to or less than the predetermined number E1. If the error number EN is equal to or less than the predetermined number E1, the error rate detection unit 72 determines that the current reproduction characteristic is not matched with the optical disc 51 being reproduced, and maintains the current characteristic (step B3).

When the error number EN is greater than or equal to the predetermined number E1, the error rate detection unit 72 determines that the waveform equalization characteristics of the waveform equalizer 55 are not matched, and switches the waveform equalization characteristics to the second direction first. (Step B9). After waiting for the signal processing period for a plurality of blocks (step B10), the error rate detection unit 72 returns to step B4 to determine whether the error number EN has increased or decreased.

In the second time, if the error number EN decreases, the error rate detection unit 72 determines that the control direction is correct, and switches the waveform equalization characteristics of the waveform equalizer 55 toward the control direction. On the contrary, if the error number EN is increasing, the error rate detection unit 72 determines that the control direction is wrong, switches the waveform equalization characteristic of the waveform equalizer 55 in the opposite direction to the previous time, and again performs the process of step B4. Return to

FIG. 15 shows various examples of what is to be controlled when controlling the waveform equalization characteristics of the waveform equalizer 55. This waveform equalizer 55 can vary its delay and amplitude characteristics, respectively. The variable control of these characteristics is realized by generating the delay characteristic control signal and the amplitude characteristic control signal from the previous error rate detection unit 72. The error rate detection unit 72 is specifically a microprocessor (MPU).

Further, in the waveform equalizer 55, the characteristic can be switched by varying the delay amount of the delay element D therein, and the coefficient is multiplied by a multiplier that multiplies the coefficient by the output of each delay element D. The characteristic can also be switched by varying the value of k.

16 shows an example of operation for switching control of the characteristics of the waveform equalizer 55. FIG. This operation example is slightly different from the operation of setting the waveform equalization characteristic in which the minimum number of errors is realized and setting the characteristic in which the error number of a few degrees or less is realized, as shown in FIG.

First, the error rate detection unit 72 sets the delay characteristic of the waveform equalizer 55 to an intermediate characteristic of the variable range (step Cl). Next, the error rate detection unit 72 switches the amplitude characteristics of the waveform equalizer 55 in a plurality of stages, and sets the error count [EN1, EN2,... , EN (n)] respectively. The error rate detection unit 72 detects EN (min), which is the minimum among these errors, and sets the amplitude characteristics corresponding to the minimum error number EN (min) to the waveform equalizer 55 again. (Steps C2, C3).

Next, the error rate detection unit 72 switches the delay characteristics of the waveform equalizer 55 in a plurality of stages, and sets the error number [EN (n + 1), EN (n + 2), … , EN (m)]. The error rate detection unit 72 detects EN (min) which is the minimum among these error numbers, and sets the delay characteristic corresponding to the minimum error number EN (min) to the waveform equalizer 55 again. (Steps C4, C5).

By performing the above process, the recording data of the optical disc 51 can be obtained in the best state. In addition, this control process may be performed periodically at predetermined time intervals, or may be executed within the first predetermined period, and after that, the control process may be performed depending on the reproduction position of the optical disc 51.

According to the second embodiment described above, the error occurrence rate at the time of reading out the modulation signal recorded on the optical disc 51 and performing the error correction of the binarization output of the modulation signal or the demodulation signal, and the error occurrence rate The most suitable waveform equalization characteristic can be set according to the content of the information.

Next, another example for switching control of the characteristics of the waveform equalizer 55 will be described. That is, FIG. 17 shows the change of the error rate with respect to the change of the amplitude characteristic of the waveform equalizer 55. FIG. If the variable range of the amplitude characteristics of the waveform equalizer 55 is from A to B, first, it is set to the intermediate amplitude characteristic C, and based on the error rate at that time, the amplitude characteristic at which the error rate is minimum ( Obtain D)

Thereafter, the amplitude characteristics are sequentially changed from D to A at regular intervals to obtain an amplitude characteristic E whose error rate is three times the minimum error rate. Further, the amplitude characteristic is sequentially changed from D to B at regular intervals to obtain an amplitude characteristic F whose error rate is three times the minimum error rate. The amplitude characteristic in the middle of E and F is set as the most suitable amplitude characteristic.

18 to 21 show flowcharts for realizing switching control of the waveform equalization characteristics as described above. First, the error rate detection unit 72 sets the amplitude characteristic of the waveform equalizer 55 to the intermediate characteristic C of the variable range (step D1), and reads the error rate at that time (step D2). Thereafter, the error rate detection unit 72 sequentially changes the amplitude characteristics of the waveform equalizer 55 from C to the A side at regular intervals, thereby obtaining the amplitude characteristics D at which the error rate is minimized (steps D3 to 3). D9).

Next, the error rate detection unit 72 sequentially changes the amplitude characteristics of the waveform equalizer 55 at regular intervals from C to B, so that the error rate becomes smaller than the error rate in the amplitude characteristic D previously obtained. By searching for D (steps D10 to D17), an amplitude characteristic D is obtained which results in the minimum error rate within the range of A to B.

After that, the error rate detection unit 72 sequentially changes the amplitude characteristics of the waveform equalizer 55 from D to the A side at regular intervals, thereby obtaining amplitude characteristics E such that the error rate is three times the minimum error rate (steps D18 to 18). D28). Next, the error rate detection unit 72 sequentially changes the amplitude characteristics of the waveform equalizer 55 from D to B at regular intervals, thereby obtaining an amplitude characteristic F in which the error rate is three times the minimum error rate (step). D24 to D29).

Then, the error rate detection unit 72 sets the intermediate amplitude characteristics of the amplitude characteristics S and F obtained as described above as the optimum amplitude characteristics (step D30).

In the above description, in order to switch the waveform equalization characteristics of the waveform equalization circuit 55, the amplitude characteristics are controlled. However, the waveform equalization characteristics are not limited to this. You may want to control it.

In addition, this invention is not limited to each said Example, In addition, various deformation | transformation can be implemented in the range which does not deviate from the summary.

As described above, according to the present invention, at least the reproduction output state of the modulation signal recorded on the optical disc can be identified, and the type of the optical disc can be discriminated.

In addition, according to the present invention, when the modulated signal recorded on the optical disc is picked up, at least the reproduction state of the modulated signal can be made closer to the ideal characteristic, and the reproduction state of the reproducing apparatus can be maintained at the best state by using the parameters of the optical disc. have.

Claims (41)

Data is recorded, and a part of the data includes a parameter for setting a waveform equalization characteristic which becomes a standard for reading the data, and the waveform equalization characteristic is switched by the waveform equalization circuit based on the contents of the parameter, and at least A recording medium characterized by obtaining one waveform equalization characteristic. 2. The recording medium of claim 1, wherein the recording data is read by an optical pickup section, and the parameter indicates a length per unit bit of the recording data on the recording medium. The method according to claim 1, wherein the parameter indicates at least one of the case where the linear density of the recording data on the recording medium is 0.267 µm / bit, the 0.293 µm / bit, and the 0.409 to 0.435 µm / bit. Characterized in that the recording medium. The recording medium of claim 1, wherein the parameter is recorded in a lead-in area of the recording medium. A recording medium according to claim 1, wherein a plurality of kinds of said parameters are recorded in order to designate the characteristics of each part of the reproduction apparatus. The recording medium of claim 1, wherein the parameter is recorded at various places of the recording medium. The recording medium of claim 1, wherein the parameter is identification data for identifying a type of the recording medium. 2. The recording apparatus according to claim 1, wherein the recording data is read by an optical pickup section, and the parameter is data for changing a waveform equalization characteristic by controlling a frequency band amplitude characteristic of a high frequency modulated signal output from the optical pickup section. Recording media. 2. The recording apparatus according to claim 1, wherein the recording data is read by the optical pickup section, and the parameter is data for changing the waveform equalization characteristic by controlling the frequency band delay characteristic for the high frequency modulated signal output from the optical pickup section. Recording media. The data of claim 1, wherein the recording data is read by the optical pickup section, and the parameter controls data of the waveform equalization characteristic by controlling both frequency band amplitude characteristics and frequency band delay characteristics for the high frequency modulated signal output from the optical pickup section. Recording medium. A pickup section for reading data recorded in the data recording area, waveform equalization means for performing waveform equalization processing on the high frequency modulated signal output from the pickup section, demodulation means for demodulating the output signal of the waveform equalization information, and A recording medium in which data recorded in the data recording area is reproduced by a reproduction device having control means, In the data recording area, a plurality of parameters indicating the recording form of the data recorded in the data recording area are recorded. And the control means switches the waveform equalization characteristic of the waveform equalization means based on the contents of the parameter demodulated by the demodulation means. 12. The recording medium of claim 11, wherein the parameter indicates a length per unit bit of data recorded in the data recording area. 12. The method according to claim 11, wherein the parameter indicates at least one of a case where the linear density of data recorded in the data recording area is 0.267 µm / bit, 0.293 µm / bit, and 0,409 to 0.435 µm / bit. And a recording medium. 12. The recording medium of claim 11, wherein the parameter is data for controlling the frequency equalization characteristic of the waveform equalization means with respect to the high frequency modulated signal output from the pickup section to change the waveform equalization characteristic. 12. The recording medium of claim 11, wherein the parameter is data for controlling a frequency versus delay characteristic of the waveform equalization means with respect to a high frequency modulated signal output from the pickup section to change the waveform equalization characteristic. 12. The recording according to claim 11, wherein the parameter is data for controlling both the frequency band amplitude characteristic and the frequency band delay characteristic of the waveform equalizing means with respect to the high frequency modulated signal output from the pickup section to change the waveform equalization characteristic. media. A reproducing apparatus for reproducing a recorded recording medium including at least a parameter for obtaining waveform equalization characteristics that are optimal for reading the recorded data into a part of the recorded data. A pickup section for reading the record data from the record medium; Waveform equalization means for performing waveform equalization processing on the high frequency modulated signal output from the pickup section; Demodulation means for performing a demodulation process on the output signal of the waveform equalization means; And control means for switching waveform equalization characteristics of said waveform equalization means based on the contents of said parameter demodulated by said demodulation means. 18. The reproducing apparatus as set forth in claim 17, wherein said demodulation means comprises binarization means for binarizing an output signal of said waveform equalization means. 18. The reproducing apparatus as set forth in claim 17, wherein the control means controls the frequency versus amplitude characteristics of the waveform equalization means with respect to the high frequency modulated signal output from the pickup section to change the waveform equalization characteristics. 18. The reproducing apparatus as set forth in claim 17, wherein the control means controls a frequency band delay characteristic of the waveform equalization means with respect to the high frequency modulated signal output from the pickup section to change the waveform equalization characteristic. 18. The reproducing apparatus as set forth in claim 17, wherein the control means controls both the frequency band amplitude characteristic and the frequency band delay characteristic of the waveform equalization means with respect to the high frequency modulated signal output from the pickup unit to change the waveform equalization characteristic. . 18. The reproduction apparatus according to claim 17, wherein the parameter represents a length per unit bit of the recording data on the recording medium. 18. The apparatus according to claim 17, wherein the parameter indicates at least one of the case where the linear density of the recording data on the recording medium is 0.267 µm / bit, when 0.293 µm / bit, and when 0.409 to 0.435 µm / bit. A playback apparatus, characterized in that. 18. The playback apparatus according to claim 17, wherein the parameter is a command for controlling the characteristics of each part of the playback apparatus. A reproduction apparatus for reproducing a recording medium recorded by including a parameter indicating a recording form of the recording data in a part of the recording data, A pickup section for reading the record data from the record medium; Waveform equalization means for performing waveform equalization processing on the high frequency modulated signal output from the pickup section; Demodulation means for performing a demodulation process on the output signal of the waveform equalization means; And discriminating means for discriminating the type of said recording medium based on the contents of said parameter demodulated by said demodulation means. Waveform equalization means for performing waveform equalization processing on the input high frequency modulated signal to selectively switch a plurality of waveform equalization characteristics; Binarization means for binarizing an output signal of the waveform equalization means; Error correction means for detecting an error in an output signal of said binarization means and performing an error correction process; Error occurrence rate detection means for obtaining occurrence rate information of an error detected by the error correction means; And control means for switching the waveform equalization characteristic of said waveform equalization means based on the occurrence rate information of the error obtained by said error occurrence rate detection means. 27. The data reproducing apparatus according to claim 26, wherein the control means controls the frequency band amplitude characteristics of the waveform equalization means with respect to the high frequency modulated signal to change the waveform equalization characteristics. 27. The data reproducing apparatus as set forth in claim 26, wherein said control means controls a frequency band delay characteristic of said waveform equalization means with respect to said high frequency modulated signal to change its waveform equalization characteristic. 27. The data reproducing apparatus as set forth in claim 26, wherein said control means controls both the frequency equalization characteristic and the frequency equalizing delay characteristic of said waveform equalizing means with respect to said high frequency modulated signal to change its waveform equalizing characteristics. The method of claim 29, wherein the control means, First means for setting a frequency versus delay characteristic of said waveform equalizing means to an intermediate characteristic in a variable range; By the second means, the frequency characteristic of the waveform equalizing means is set to an intermediate characteristic of a variable range, and the frequency characteristic of the waveform equalizing means is changed to change the frequency characteristic of the amplitude so that the occurrence rate of the error is minimized. Second means for searching for and setting the waveform equalization means; By the second means, the frequency equalizing characteristic of the waveform equalizing means is set, the frequency equalizing delay characteristic of the waveform equalizing means is changed to search for a delay characteristic at which the occurrence rate of the error is minimized, and the waveform equalizing is performed. And a third means for setting the means. 30. The data reproducing apparatus according to claim 29, wherein the control means sets the frequency-to-amplitude characteristic of the waveform equalizing means so as to fall within a range between the minimum occurrence rate of the error and a value higher by a predetermined amount than the minimum value. . 30. The data reproducing apparatus according to claim 29, wherein the control means sets the frequency band delay characteristic of the waveform equalizing means so as to fall within a range between the minimum occurrence rate and the value higher by the predetermined amount than the minimum value. 30. The apparatus as set forth in claim 29, wherein the control means sets the frequency-to-amplitude characteristics and the frequency-delay characteristics of the waveform equalizing means so as to fall within a range between the minimum occurrence rate and the value higher than the minimum value by a predetermined amount. Data reproducing device. A waveform equalization step of performing a waveform equalization process on the input high frequency modulated signal and selectively switching a plurality of waveform equalization characteristics; A binarization step of binarizing the waveform equalized signal in the waveform equalization step; An error occurrence rate detecting step of detecting an error of a signal binarized in the binarizing step to obtain information on an occurrence rate of the error; And a control step of switching the waveform equalization characteristic based on the occurrence rate information of the error obtained in the error occurrence rate detecting step. 35. The data reproduction method according to claim 34, wherein said controlling step changes the waveform equalization characteristic by controlling the frequency band amplitude characteristic of said waveform equalization with respect to said high frequency modulated signal. 35. The method of claim 34, wherein said controlling step changes the waveform equalization characteristic by controlling the frequency versus delay characteristic of said waveform equalization with respect to said high frequency modulated signal. 35. The method of claim 34, wherein the switching control step controls both the frequency equalization amplitude and the frequency equal delay characteristic of the waveform equalization for the high frequency modulated signal to change the waveform equalization characteristic. 35. The method of claim 34, wherein the controlling step comprises: a first step of setting the frequency versus delay characteristic of the waveform equalization to an intermediate characteristic of a variable range; In the first step, the frequency characteristic of the waveform equalization is changed while the frequency characteristic of the waveform equalization is set to an intermediate characteristic of a variable range, thereby retrieving the amplitude characteristic of which the occurrence rate of the error is minimized. A second step of setting the waveform equalization characteristic; In the state in which the frequency-to-amplitude characteristic of the waveform equalization is set in the second step, the frequency-to-delay characteristic of the waveform equalization is changed to search for a delay characteristic that minimizes the occurrence of the error, and sets the waveform equalization characteristic. And a third step. 35. The method of claim 34, wherein the controlling step is set such that the frequency-to-amplitude characteristic of the waveform equalization falls within a range between the minimum occurrence rate and the value higher by a predetermined amount than the minimum value. 35. The method of claim 34, wherein the controlling step sets the frequency-to-delay characteristic of the waveform equalizing step so as to fall within a range between the minimum occurrence rate of the error and a value higher by a predetermined amount than the minimum value. 35. The method of claim 34, wherein the controlling step sets the frequency-to-amplitude characteristics and the frequency-to-delay characteristics of the waveform equalization so as to fall within a range between the minimum occurrence of the error and a value higher than the minimum by a predetermined amount. Data playback method.

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