JP2004030911A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture an optical recording medium from which address information can accurately be detected while realizing high density recording of an information signal. <P>SOLUTION: The optical recording medium has wobbled grooves 1 and forms a plurality of grooves 2 denoting address information in a radial direction so as to connect the grooves 1 adjacent to each other. <P>COPYRIGHT: (C)2004,JPO

Description

TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium having wobbled grooves, and more particularly to a novel optical recording medium capable of recording information signals at high density.
[0001]
[Prior art]
For example, a CD-R disk used in a so-called compact disk recordable system (CD-R) has a wobbled groove, and sector information including address information is recorded by modulation of a wobble signal.
[0002]
That is, in the CD-R recording / reproducing apparatus, a wobble signal having a carrier of, for example, 22 kHz is detected by a recording / reproducing light beam focused on a groove, and a data string including address information is subjected to FM demodulation. To be detected.
[0003]
In the method of arranging the address at the head of the sector, the address information and the recording information are recorded in a time-division manner, and the recorded signal becomes discontinuous. However, in this method, the data is recorded continuously. This is possible, and is highly useful in applications that emphasize compatibility with a read-only disc on which signals are continuously recorded.
[0004]
[Problems to be solved by the invention]
By the way, in the method of recording address information by modulation of a wobble signal, when the track pitch, which is the distance between adjacent grooves, is reduced, the leakage of the wobble signal from the adjacent groove increases, and the S / N ratio of the wobble signal decreases. As a result, not only the demodulation of the address information cannot be performed correctly, but also the detection of the carrier wave of the wobble signal necessary for the control of the rotation of the disk becomes difficult.
[0005]
In order to record signals at a high density, it is necessary to narrow the track pitch. Therefore, it is necessary to reproduce address information accurately even at a narrow track pitch.
[0006]
In the above-described method, the position accuracy of the spot of the recording / reproducing light beam on the disk obtained by the reproduced address information depends on the frequency of the carrier wave, and is approximately on the order of the wavelength of the carrier wave. On the other hand, it is necessary to select a relatively low frequency of the carrier wave, that is, the wobbling frequency so as not to adversely affect the recording signal. In the case of a CD-R, the frequency is 22 kHz and the wavelength on the disk is 54 μm.
[0007]
In the case where data is recorded at intervals rather than continuously, and data is subsequently recorded in an unrecorded portion, it is necessary to record data at an accurate position on the disk. If recording cannot be performed accurately, it is necessary to provide a so-called gap for absorbing a recording position error for each unit of data to be recorded so as to avoid duplication of recording data.
[0008]
Since the gap reduces the recordable capacity of the disc, its length needs to be as small as possible, but the accuracy described above is insufficient.
[0009]
The present invention has been proposed in view of such a conventional situation. It is possible to accurately obtain address information and disk rotation control information even at a narrow track pitch, and to record signals at high density. It is an object of the present invention to provide an optical recording medium capable of performing the above.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an optical recording medium according to the present invention has a wobbled groove and has a plurality of grooves formed in the radial direction so as to continue between adjacent grooves.
A plurality of grooves formed so as to be continuous between adjacent grooves are used for indicating address information.
[0011]
In the optical recording medium according to the present invention, even at a narrow track pitch, address information and rotation control information of the optical recording medium can be accurately obtained, and high-density signal recording is achieved.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the optical recording medium according to the present invention will be specifically described. The optical recording medium according to the present invention has wobbled grooves, and pits are formed at predetermined intervals in an area between the grooves. This enables density recording.
[0012]
The pits are formed in a region between the grooves, that is, in the land portion, and the shape may be a normal pit, or a notch in the land portion connecting the grooves, that is, a groove adjacent to the groove. It may be formed continuously.
[0013]
The pit usually has sector information including a sync pit, an address pit, and the like, and the address information and the like can be obtained from the sector information. However, in the case of the present invention, such pit information is not always required. May not exist, and may have only sync pits or only address pits. Note that the sync pit is a pit indicating the start position of the sector information. For example, the sync pit is formed as two pits arranged close to each other or as a pit having a different pit length from the other pits. It is possible to detect separately.
[0014]
On the other hand, the groove may have a wobble signal of a single frequency, or may have sector information in which a synchronization signal and address data are recorded by modulation.
[0015]
The sector information is information associated with a sector of recording data or a cluster which is a set of recording data sectors, and includes a synchronization signal or address data, or both a synchronization signal and address data. These combinations are also arbitrary. For example, a combination of a groove and a sync pit having a wobble signal of a single frequency, an address pit, a groove and a sync having a wobble signal in which sector information such as a synchronization signal and address data are recorded by modulation, and a sync Examples include a combination of pits and address pits, and a combination of a groove having a wobble signal in which sector information is recorded by modulation and pits at fixed intervals.
[0016]
Of the above combinations, for example, when a combination of a groove having a single frequency wobble signal, a sync pit, and an address pit is employed, synchronization information and address information can be reliably obtained by the sync pit and the address pit, The rotation control information of the disk can be accurately obtained by the wobble signal.
[0017]
If the wobble signal is a single-frequency signal, even if the leakage signal from the adjacent groove becomes large, the leakage signal has exactly the same frequency as the signal to be detected. Only a slow change in the amplitude of the wobble signal to be detected, and therefore the single frequency to be detected is easily detected.
[0018]
When a combination of a groove having a wobble signal in which sector information including a synchronization signal and address data is recorded by modulation, and a combination of a sync pit and an address pit, the synchronization information and the address information are applied to both the groove and the pit. Since the information is recorded twice, accuracy and reliability are increased.
[0019]
When the groove and the pit are combined as described above, if the pit position is formed at random with respect to the groove, the level of the reproduced signal obtained by the pit position may fluctuate, and it may be difficult to detect the pit accurately. There is. Alternatively, there is also a problem that a clock generating circuit in a reproducing apparatus for reproducing these is complicated.
[0020]
Therefore, in order to solve this, it is preferable that the relationship between the wobble frequency fw (average frequency) and the pit frequency fp be an integer relationship as shown in the following equation (1).
[0021]
M × fw = N × fp (where M and N are integers) (1)
In other words, the relationship between the wobble period Tw and the pit period Tp is an integer relationship shown in the following equation (2).
[0022]
M × Tw = N × Tp (where M and N are integers) (2)
The wobble period Tw is an average period of the wobble, and the pit period Tp is a predetermined interval when pits are recorded at an integral multiple of a predetermined interval. For example, in a pit period Tp when two consecutive pits are set as sync pits, the two consecutive pits are regarded as one pit, and the period between these two pits is ignored.
[0023]
If the wobble frequency fw and the pit frequency fp are in an integer relationship in this manner, it is possible to use one reference clock or one voltage-controlled oscillator VCO, thereby simplifying the clock generation circuit of the recording / reproducing apparatus. It can be.
[0024]
Further, a signal synchronized with the pit period can be generated from the wobble signal using the PLL, and as a result, the pit can be accurately detected.
[0025]
Alternatively, the pits may be detected accurately by matching the phases of the wobbles and the pits.
[0026]
That is, the pit position is made to correspond to the constant phase of the wobble, and the pit is formed at a position where the wobble amount (groove meandering amount) is constant, so that the pit detection signal can be stabilized, and the pit can be accurately detected. It becomes possible to detect.
[0027]
In this case, as shown in FIG. 1, the pits P are formed corresponding to the wobble center position of the groove G (the position where the wobble amount is minimum). Alternatively, as shown in FIG. 2, the pit P may be formed at a position where the wobble amount is substantially maximum and is close to an adjacent groove. In the former case, crosstalk from other grooves is minimized, and in the latter case, pits can be detected only at the signal level without removing the wobble signal component.
[0028]
If sector information including synchronization information and address information is recorded in the wobble signal, and the pits also have sector information such as sync pits and address pits, the sector information, especially the synchronization signal between the sync pit and the wobble signal, is recorded. Is preferably constant. For example, in the reproduction direction, a synchronization signal by wobble is recorded within one pit cycle before a sync pit.
[0029]
As described above, by previously knowing the position of the pit address synchronization section from the wobble signal, it is possible to more accurately detect the synchronization of the pit address, and as a result, the pit address reading becomes more reliable.
[0030]
When performing recording and reproduction on the optical recording medium described above, the rotation of the disk is controlled using a signal detected from the wobbled groove, and the information detected from the pits on the land portion is used to record the recording signal on the disk. Control the position.
[0031]
At this time, if the wobble signal and the pit signal are read out simultaneously by one beam spot using the push-pull method, the simplification of the recording / reproducing apparatus can be realized.
[0032]
【Example】
Hereinafter, specific examples to which the present invention is applied will be described in detail with reference to the drawings.
[0033]
Example 1
The optical disc of this embodiment is a write-once disc having a recording film of an organic dye capable of recording with a laser beam having a wavelength of 635 nm and having a diameter of 12 cm.
[0034]
The disk substrate on which the recording film of the optical disk is formed is formed by injection molding polycarbonate, and has a guide groove (groove) and a land portion between the grooves.
[0035]
The groove has a width of about 0.25 μm and a depth of about 70 nm, and is formed as a continuous spiral from the inner circumference to the outer circumference at a groove interval (track pitch) of about 0.74 μm.
[0036]
A wobble signal having a single frequency is recorded in the groove as information for controlling the rotation speed of the disk and the clock frequency of the recording signal. Note that the wobble is to meander the groove slightly in the radial direction of the disk.
[0037]
In this example, the meandering width is 20 nm, and the meandering cycle is about 30 μm. Therefore, when this disk is rotated at a linear velocity of 3.5 m / sec and the wobble signal is reproduced, the frequency is about 120 kHz.
[0038]
On the other hand, in a land portion between the grooves, a groove having a width of about 0.3 μm and a depth of about 70 nm, which is the same as the groove, is formed as a pit (address pit) for recording address information.
[0039]
FIG. 3 schematically shows the above-mentioned grooves and address pits. In this example, address pits 2 are formed at predetermined intervals in a region between grooves 1 to be wobbled. Each address pit 2 continues between adjacent grooves and is formed as a groove in the radial direction of the disk.
[0040]
The address pits are formed at intervals of about 0.2 mm in this example and correspond to 1/0 of information. That is, there is an address pit at a position corresponding to information 1 and no address pit at a position corresponding to information 0. Therefore, the presence or absence of the address pit corresponds to 1/0 of the information.
[0041]
FIG. 4 shows a signal obtained when the beam spot B is scanned along the groove. Specifically, a pulse due to the inner address pits and a pulse due to the outer address pits having the opposite polarity are obtained. Therefore, the address information may be detected based on one of these.
[0042]
In this recording method, it is expected that if the information continues, the state in which the address pits are not recorded continues, making it difficult to detect the address pits. In the present embodiment, the information to be recorded is preliminarily so-called bi-phase modulation. However, the sequence of 0s is a maximum of 2 bits.
[0043]
However, in the synchronizing signal, a pattern outside the modulation rule of 000111 is provided to facilitate detection of the synchronizing signal. Therefore, in the synchronizing signal section, there is a portion where address pits are not recorded continuously for three channel bits. .
[0044]
FIG. 5 shows an example of synchronization pattern and data bit modulation. The synchronization pattern is 0110001110001110, and includes 0 and 1 consecutive three channel bits outside the modulation rule as described above.
[0045]
The data bits are modulated such that 0 is 1-0 and 1 is 0-1. Therefore, the data portion does not include a continuation of 1 and a continuation of 0 of three or more channel bits.
[0046]
FIG. 6 shows an example of a recording format of the sector information. The sector information is composed of a total of 208 channel bits (channel @ bit), the first 16 channel bits are a synchronization pattern, and a parity for error correction of a 4-byte Reed-Solomon code is added to 8-byte address data. Is added.
[0047]
In this recording format, up to 2 bytes can be corrected by a 4-byte parity. Therefore, even if 2 channel bits at an arbitrary position in the 208 channel bit sector information are incorrect, address data can be correctly detected. .
[0048]
Next, the signal reproduction of the optical disk configured as described above will be described. Here, a method of simultaneously reading out a groove wobble signal and a pit address signal using a push-pull method with one beam spot will be described.
[0049]
FIG. 7 is a block diagram of the signal reproducing circuit. In FIG. 3, the return light from the beam spot B condensed on the groove 1 is photoelectrically converted by using the PIN diodes A, B, C, and D of four detectors as detectors, and IV-converted to IV conversion. Signals A, B, C, and D corresponding to the respective diodes obtained.
[0050]
Of these signals, the sum of the signals A, B, C, and D (A + B + C + D) is a reproduced signal of the recorded signal. Reproduction data is obtained by binarization by the circuit 12, and a clock of the reproduction data is obtained from the binarized data by a PLL circuit constituted by a phase comparator 13 and a voltage controlled oscillator (VCO) 14.
[0051]
On the other hand, when an operation of (AB) + (CD) is performed using the signals A, B, C, and D, a focus error signal of an astigmatism method is obtained.
[0052]
The focus error signal is sent to the focus drive circuit 16 via the phase compensation circuit 15, and the focus drive circuit 16 outputs a focus drive signal for controlling the focus position of the objective lens.
[0053]
Further, when an operation of (A + B)-(CD) is performed using the signals A, B, C, and D, a so-called push-pull tracking error signal is obtained. Since this signal is a signal corresponding to the relative position of the groove and the beam spot B in the radial direction, the wobble signal of the groove is reproduced at the same time. Further, even at the position where the address pit is recorded, a plus or minus pulse is detected depending on whether the address pit is on the inner circumference side or the outer circumference side of the disk, and this signal is also a signal (A + B). -(CD).
[0054]
Therefore, first, only the tracking error signal is extracted from the signal (A + B)-(CD) through a low-pass filter (LPF) 17 and sent to a tracking drive circuit 19 via a phase compensation circuit 18 to convert the tracking drive signal. Output.
[0055]
In order to detect a pulse signal generated by an address pit, a high-pass filter (HPF) for suppressing a signal of 130 kHz or less in order to avoid the influence of a wobble signal and the influence of noise in a low frequency band due to wobble meandering. 20 is used.
[0056]
Since the wobble signal is a signal in a narrow band, a good S / N wobble signal can be obtained by using a band-pass filter (BPF) 21 that passes the band. The obtained wobble signal is binarized by a binarization circuit 22, and the binarized data is compared with a reference frequency in a frequency comparison circuit 23 to obtain a spindle motor control signal.
[0057]
As described above, in the present embodiment, it is possible to obtain all the signals necessary for signal reproduction with one 4-division PIN diode.
[0058]
Example 2
In this example, various combinations of wobbles and pits will be described.
[0059]
First, the first example is an example in which a wobble of a single frequency and pits are formed so as to have an integer relationship with the frequency of the wobble signal.
[0060]
In this case, the obtained signal is as shown in FIG. 8, and the pit signal Sp is detected at intervals of an integral multiple of the period Tw of the wobble signal Sw, that is, at intervals of an integral multiple of the pit period Tp.
[0061]
The second example is an example in which a pit is formed by adjusting the phase of a modulated wobble signal. This example is an example in which a pit is formed at a position where the wobble amount is substantially maximum and is close to an adjacent groove. As shown in FIG. 9, the pit signal Sp is located at the vertex of the wobble signal Sw, and Pits are detected only by the signal level of the signal Sp.
[0062]
In FIG. 9, a pit signal Sp is a pit signal generated by pits arranged on the inner circumference side of the groove being tracked, while a pit signal Sp ′ is generated by pits arranged on the outer circumference side of the groove. This is the generated pit signal.
[0063]
In the first embodiment, the pit signal is detected after the wobble signal is removed from the pit signal by the high-pass filter. However, the high-pass filter in the present embodiment allows the wobble signal to pass and the pit signal including the wobble signal to pass. A pit is detected by comparing the signal Sp with the detection level L. This is because when the frequency band of the wobble signal and the frequency band of the pit signal are close to each other, it is assumed that the frequency separation by the high-pass filter is difficult.
[0064]
Further, in this example, the pits on the inner peripheral side of the groove are recorded at positions where the groove wobbles by the maximum amount on the inner peripheral side. In this case, the pits on the outer periphery are recorded at positions where the adjacent grooves on the outer periphery are wobbled by the maximum amount toward the inner periphery.
[0065]
Since the wobble signals between adjacent grooves do not always match, as shown in FIG. 9, even if the pit signal Sp due to the pits on the inner circumference is located at a position where the wobble signal has a constant value, it is associated with another groove. The pit signal Sp 'of the outer peripheral pit recorded in this manner is located irrespective of the wobble signal.
[0066]
As shown in FIG. 9, while the peak value of the pit signal Sp 'due to the outer peripheral pit positioned independently of the wobble signal varies for each pit, the inner peripheral side recorded at a position where the wobble amount is constant The peak value of the pit signal Sp due to the pit is constant.
[0067]
When the peak value is constant, for example, even if the amplitude of the pit signal changes, the peak value can be easily detected by a simple peak hold circuit, and the detected peak value is used to optimize the pit detection level. It is possible to detect pits stably by keeping the value. This is an advantage obtained when a pit is formed at a position where the wobble amount is substantially constant.
[0068]
Further, in this example, since the pit signal Sp is located at the vertex of the wobble signal Sw, the allowable fluctuation width of the detection level is the largest. This is an advantage in the case where pits are formed at positions where the wobble amount is almost maximum and adjacent grooves are adjacent.
[0069]
FIG. 10 shows an example in which a synchronization signal Sws is recorded in a wobble signal, and this is combined with a sync pit Ssp.
[0070]
In this case, the position of the sync pit Ssp can be known in advance from the synchronization signal Sws of the wobble signal, and the sync pit Ssp can be detected more reliably.
[0071]
As described above, various combinations of wobbles and pits are conceivable, and the following advantages are obtained by these combinations.
[0072]
First, the case where the wobbles and pits are formed in phase will be described.
[0073]
FIG. 11 shows a reproduction signal obtained from such an optical disk, and this reproduction signal is composed of a wobble signal Sw and a pit signal Sp. Here, it is assumed that the pit signal includes a noise component Sn.
[0074]
FIG. 12 is a block diagram of a reproducing apparatus for reproducing the wobble signal and the pit signal.
[0075]
In this reproducing apparatus, the wobble signal Sw is supplied to a binarization circuit 32 via a band-pass filter 31, while the pit signal Sp is supplied to a binarization circuit 34 via a high-pass filter 33, and each of the pit signals Sp is supplied to a binarization circuit 34. Valued.
[0076]
At this time, the pit signal Sp and the noise component Sn are output from the binarization circuit 34 as shown in FIG.
[0077]
The wobble signal Sw is further sent to the phase comparison circuit 35, and the oscillation frequency of the voltage controlled oscillator 36 is divided by 1 / (M * 100) by the 1/100 frequency dividing circuit 37 and the 1 / M frequency dividing circuit 38. The phase is compared with the signal. By controlling the voltage-controlled oscillator 36 based on the phase information detected by the phase comparison circuit 35, a phase-locked loop is formed. As a result, the frequency Fo of (M * 100) times the wobble signal frequency Fw is increased. Output from
[0078]
Assuming that the wobble frequency Fw and the pit frequency Fp have a relationship of Fw * M = Fp * N, the oscillation frequency Fo of the voltage controlled oscillator 36 is Fo = Fw * (M * 100) = Fp * (N * 100) Therefore, the frequency becomes (N * 100) times the pit frequency Fp.
[0079]
Therefore, by dividing the output of the voltage controlled oscillator 36 by the 1 / (N * 100) counter 39, the phase information shown in FIG. 11C is obtained and output to the pit pulse detection / interpolation circuit 40.
[0080]
Then, by taking the AND of the phase information shown in FIG. 11C and the output from the binarization circuit 34, the noise component Sn is canceled as shown in FIG. 11D, and the original pit signal Sp Only the pit data clock shown in FIG. 11E and the pit data shown in FIG. 11F are output.
[0081]
As in this example, when the wobble frequency Fw and the pit frequency Fp have a relationship of Fw * M = Fp * N (M and N are integers), phase information is obtained from the wobble signal in a pit cycle by a phase locked loop. Thus, accurate pit address detection is possible.
[0082]
Next, an example in which a synchronization signal (sync) is recorded in a wobble signal and this is combined with a sync pit will be described.
[0083]
In FIG. 13, the wobble signal shown in (a) is FM-modulated, and the result of demodulation is shown in (b). On the other hand, by arranging the sync of the pre-pit immediately after the sync of the wobble as shown in (c), it is possible to detect the sync of the pre-pit after detecting the sync of the wobble.
[0084]
The positional accuracy of the wobble itself is not as accurate as that of the prepit, but the safety of the prepit signal itself can be improved by creating a mechanism for protecting the prepit in a system different from the prepit.
[0085]
As a use method other than the gate, as shown in FIG. 14, it is also possible to insert a head discrimination signal of the pre-pit string by wobble.
[0086]
As a result, it is not necessary to form a sync pattern with pre-pits, and it is possible to increase pre-pit information. Further, since it is not necessary to detect the pre-pit sync pattern, the circuit can be saved, and the reliability is increased because the control system is duplicated.
[0087]
【The invention's effect】
As described above, the optical recording medium according to the present invention has wobbled grooves, and a plurality of grooves indicating address information information are formed in the radial direction so as to continue between adjacent grooves. An optical recording medium on which information is recorded can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example in which pits are arranged at the center of a wobble in an optical disc to which the present invention is applied.
FIG. 2 is a schematic diagram showing an example in which a pit is formed at a position where a wobble amount is maximum and is close to an adjacent groove in an optical disc to which the present invention is applied.
FIG. 3 is a schematic plan view of an essential part schematically showing an example of grooves and pits in an optical disc to which the present invention is applied.
FIG. 4 is a waveform diagram showing a pulse signal obtained from a pit.
FIG. 5 is a diagram showing an example of modulation of a synchronization pattern and data bits.
FIG. 6 is a diagram illustrating an example of a recording format of address information.
FIG. 7 is a circuit diagram illustrating an example of a signal reproducing circuit.
FIG. 8 is a waveform diagram illustrating an example of a reproduced signal when the frequencies of a wobble signal and a pit signal are set to an integer relationship.
FIG. 9 is a waveform diagram showing an example of a reproduced signal when the phases of a wobble signal and a pit signal are matched.
FIG. 10 is a waveform diagram showing an example of a reproduced signal when a synchronization signal is recorded in both wobbles and pits.
FIG. 11 is a timing chart when the phases of a wobble signal and a pit signal are matched.
FIG. 12 is a block diagram illustrating an example of a reproduction circuit in the reproduction device.
FIG. 13 is a timing chart when a synchronization signal is recorded in both wobbles and pits.
FIG. 14 is a timing chart in a case where a head discrimination signal of a pre-pit string is inserted by wobble.
[Explanation of symbols]
1 groove, 2 pits

Claims (1)

An optical recording medium having a wobbled groove and a plurality of grooves formed in a radial direction so as to be continuous between adjacent grooves.

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