JP4170241B2 - Optical disc, clock signal generation method, and optical disc apparatus - Google Patents

Description

  The present invention relates to an optical disc, a clock signal generation method, and an optical disc apparatus. More specifically, the present invention relates to an optical disc on which multilevel information is recorded, and a clock for generating a clock signal used when reproducing information from the optical disc. The present invention relates to a signal generation method and an optical disc apparatus for reproducing information from the optical disc.

  In recent years, with the advancement of digital technology and the improvement of data compression technology, CD-ROM and CD-ROM have been used as media for recording information (hereinafter also referred to as “content”) such as music, movies, photographs, and computer software. DVD-ROM and other optical discs that can record about 7 times the data on a disc with the same diameter as a CD-ROM have been attracting attention, and at the same time, the content recorded on the optical disc is played back. The optical disk device to be used became popular.

  A reproduction-only optical disk such as a CD-ROM or DVD-ROM has a spiral or concentric pit string formed on the recording surface. Information is recorded by the length of pits, the length between pits, and combinations thereof. In this case, the information is converted (binarized) into a combination of two types of numerical values (binary) of 0 and 1, and written on the optical disc. Hereinafter, such a recording method is referred to as a binary recording method.

  By the way, the information amount of the content tends to increase year by year, and a further increase in the amount of information that can be recorded on the optical disc is expected. One way to increase the amount of information that can be recorded on an optical disc is to convert the information into a combination of three or more numerical values and write it to the optical disc. Has been done. Therefore, hereinafter, for the sake of convenience, converting information into a combination of three or more types of numerical values is referred to as multi-value data, and multi-value data is referred to as multi-value data. In addition, such a recording method for recording information with multiple values is called a multi-value recording method.

  In addition, since the distance between adjacent pit rows is small in an optical disc, it is difficult to narrow the light spot formed on the recording surface to only the target pit row (hereinafter abbreviated as “target pit row”). A part of the spot may be applied to a pit row adjacent to the target pit row (hereinafter abbreviated as “adjacent pit row”). In this case, crosstalk (crosstalk) from the adjacent pit row occurs, and the detected signal is a signal in which the signal from the adjacent pit row is superimposed on the signal from the target pit row. Become. As a result, the S / N ratio of the required signal may be reduced. In particular, in the multi-value recording system, the influence of crosstalk is larger than that in the conventional binary recording system, and there is a possibility that the reproduction timing is shifted. In view of this, an information recording medium that is not easily affected by crosstalk in the multilevel recording method has been proposed (see, for example, Patent Document 1).

  However, the information recording medium disclosed in Patent Document 1 is effective when sectors are arranged by the CAV (Constant Angular Velocity) method, the ZCAV (Zoned CAV) method, and the ZCLV (Zoned Constant Linear Velocity) method. However, there is a possibility that the CLV (Constant Linear Velocity) method capable of increasing the recording capacity cannot be supported.

JP 2003-85774 A

  The present invention has been made under such circumstances, and a first object thereof is to provide an optical disc capable of accurately obtaining a position where multi-valued information is recorded.

  A second object of the present invention is to provide a clock signal generation method capable of accurately positioning the reproduction position when reproducing information from the optical disk of the present invention.

  A third object of the present invention is to provide an optical disc apparatus capable of stably reproducing information recorded on the optical disc of the present invention.

  The invention according to claim 1 is an optical disc having a recording surface in which a plurality of pits corresponding to information multi-valued to three or more values have a recording surface formed as a pit row in a spiral shape or concentric circle shape, The optical disk includes a plurality of predetermined reference marks that periodically meander in a row and have a corresponding relationship with the meandering cycle.

  According to this, since a plurality of predetermined reference marks are formed in correspondence with the meander period of the pit row together with the multi-valued information, the reference marks are not affected by the meandering. It can be detected with high accuracy. Therefore, by referring to the reference mark, it is possible to accurately obtain the position where the multivalued information is recorded.

  In this case, as in the optical disk according to claim 2, the reference mark may be formed with a period that is ½ of the period of the meandering.

  In the optical disk according to the first aspect, the reference mark may be formed with a period that is an integral multiple of the meandering period, as in the optical disk according to the third aspect.

  In each of the optical discs according to claims 1 to 3, the reference mark may be included at a position where the meandering phase has a predetermined value as in the optical disc according to claim 4. .

  In this case, the predetermined value may be 0 degree or 180 degrees as in the optical disk according to the fifth aspect.

  In each of the optical disks according to the first to fifth aspects, as in the optical disk according to the sixth aspect, a synchronization mark indicating a delimiter of information is recorded in the pit row at a predetermined period, and the reference mark is , At least for each synchronization mark.

  In each of the optical discs according to the first to sixth aspects, as in the optical disc according to the seventh aspect, the pit row is virtually divided into a plurality of partial regions having the same length in the tangential direction of the pit row. The number of the partial areas included in one cycle of the reference mark may be an integer of 50 to 260.

  In each of the optical discs according to claims 1 to 7, as in the optical disc according to claim 8, the pit row is virtually divided into a plurality of partial regions having the same length in the tangential direction of the pit row. The number of the partial regions included in one cycle of the meandering may be an integer of 20 to 160.

  In each of the optical discs according to claims 1 to 8, as in the optical disc according to claim 9, the pit row includes a phase modulation wave portion including predetermined information and a carrier wave portion for generating a clock signal, The phase modulation wave unit may be phase modulated with the same period as the carrier wave unit.

  In each of the optical discs according to any one of claims 1 to 8, as in the optical disc according to claim 10, the pit row includes a phase modulation wave portion including predetermined information and a carrier wave portion for generating a clock signal, The phase modulation wave unit may be phase-modulated with a period twice that of the carrier wave unit.

  The invention according to claim 11 is a clock signal generation method for generating a clock signal used when reproducing information from the optical disk according to any one of claims 1 to 10, wherein the recording surface of the optical disk A method for generating a clock signal, comprising: detecting a reference mark included in a pit row of the optical disc based on reflected light from the optical disc; and generating a clock signal based on the reference mark.

  According to this, when information is reproduced from the optical disc according to any one of claims 1 to 10, the reference contained in the pit row of the optical disc is based on the reflected light from the recording surface of the optical disc. A mark is detected and a clock signal is generated based on the reference mark. In this case, since the reference mark is formed in correspondence with the meandering cycle of the pit row, the reference mark can be detected with high accuracy without being affected by the meandering. Therefore, the clock signal can be generated with high accuracy. That is, when reproducing information from the optical disk of the present invention, it is possible to accurately position the reproduction position.

  In this case, as in the clock signal generation method according to claim 12, further comprising a step of detecting a wobble signal including information on the meandering shape of the pit row based on the reflected light from the recording surface of the optical disc, In the step of generating the clock signal, a pseudo pulse signal is generated based on the wobble signal, and the clock signal is generated based on the pseudo pulse signal and the reference mark. it can.

  The invention according to claim 14 is an optical disc apparatus for reproducing information from the optical disc according to any one of claims 1 to 10, wherein the optical disc is based on reflected light from the recording surface of the optical disc. Clock signal generating means for detecting a reference mark included in the pit row and generating a clock signal based on the reference mark; and reproducing means for reproducing information recorded on the optical disk using the clock signal; An optical disc device comprising:

  According to this, when information is reproduced from the optical disc according to any one of claims 1 to 10, the clock signal generating means generates a pit string on the optical disc based on the reflected light from the recording surface of the optical disc. The included reference mark is detected, and a clock signal is generated based on the reference mark. Here, since the reference mark is formed in correspondence with the meandering cycle of the pit row, the reference mark is accurately detected without being affected by the meandering, so that the clock signal is accurately stabilized. Is generated. As a result, stable reproduction of information is performed by the reproduction means. That is, information recorded on the optical disc of the present invention can be stably reproduced.

  In this case, the optical disk apparatus according to claim 15, further comprising wobble signal detection means for detecting a wobble signal including information on the meandering shape of the pit row based on the reflected light from the recording surface of the optical disk. The reproducing means may generate a pseudo pulse signal based on the wobble signal, and generate the clock signal based on the pseudo pulse signal and the reference mark.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1A and 1B show a recording surface of an optical disc 15 according to an embodiment of the present invention.

  On the recording surface of the optical disc 15, spiral pit rows are periodically meandered (wobbled).

  By the way, the light intensity center of the light spot formed at the time of reproduction (hereinafter abbreviated as “spot center”) is located at substantially the center of the pit row when it is assumed that the pit row does not meander. Therefore, as shown in FIG. 1B, the spot center locus OTL does not coincide with the line TC passing through the center of the meandering pit row. That is, the spot center may deviate from the center position of the pit row during reproduction.

  Here, the meandering cycle of the pit row is called a wobble cycle (Twbl), and the distance between the OTLs of adjacent pit rows is called a pit row pitch (TP). Furthermore, the meandering amplitude (Wwbl) of the pit row is called meandering width. In this embodiment, as an example, Twbl = 5 μm and TP = 0.74 μm. The meandering width Wwbl will be described later.

  The meandering shape of the pit row is determined by information to be added (hereinafter also referred to as “wobble information”) and a carrier wave. In the present embodiment, when the size of one period (wobble period) of the carrier wave is one wobble, as shown in FIG. 2 as an example, a wobble information part (hereinafter referred to as “wobble information part”) and the carrier wave Is a basic unit (hereinafter referred to as “wobble unit”) composed of a portion (hereinafter referred to as “carrier wave portion”) as 93 wobbles (wobble number 0 to wobble number 92). Then, in one wobble unit, wobble number 0 to wobble number 7 are the wobble information part, and wobble number 8 to wobble number 92 are the carrier part. The wobble information part is phase-modulated (PSK: Phase Shift Keying) according to the contents.

  In the area where the address is allocated, the wobble information part is composed of synchronization information and address information. Here, as shown in FIG. 2, wobble number 0 to wobble number 3 are synchronization information, and wobble number 4 to wobble number 7 are address information.

  The address information represents 4-bit wobble and 1-bit data (hereinafter abbreviated as “bit data”). When this bit data is “0”, as shown in the wobble shape B in FIG. 3, the front two wobbles have the same phase as the carrier wave, and the rear two wobbles have the opposite phase to the carrier wave. On the other hand, when the bit data is “1”, as shown in the wobble shape C in FIG. 3, the front two wobbles are in reverse phase with the carrier wave, and the rear two wobbles are in phase with the carrier wave.

  When the first bit data of the address data is stored in the address information in the next wobble unit, the synchronization information is word sync information, that is, 4 wobbles as shown in the wobble shape A in FIG. All are in phase opposite to the carrier. Further, when bit data is stored in the address information, as shown in the wobble shape B and the wobble shape C in FIG. 3, bit sync information, that is, the first one wobble is set in reverse phase with the carrier wave, The remaining three wobbles are in phase with the carrier wave.

  Therefore, for example, when 51 pieces of bit data are required as address data, one address data is obtained from 52 wobble units as shown in FIG. The address data obtained here is a physical address (absolute address). Hereinafter, a group of wobble units corresponding to one physical address is referred to as one wobble block. Therefore, here, 1 wobble block = 52 wobble units.

  In an area where no address data is required, information relating to the optical disc such as vendor information, so-called media parameters, is added as wobble information instead of the address information.

  As an example, this optical disk 15 corresponds to laser light having a wavelength of about 660 nm, and data is recorded by a multi-value recording method. The recording data is assumed to be multi-valued to 8 values (0 to 7) as an example. Further, it is assumed that when recording data is modulated, band limitation is performed as in the binary recording method. This band limitation is to limit the pattern of the data string when modulating the recording data in order to avoid the generation of a signal having a frequency near the frequency of the servo signal (5 KHz or less) in the reproduction signal.

  In the multi-value recording method, as shown in FIG. 5 as an example, the pit row is virtually divided into a plurality of regions (hereinafter also referred to as “cells”) for each predetermined length with respect to the tangential direction of the pit row. . One multi-value data is stored in one cell. When the value of the multi-value data is 1 to 7, a pit having an area corresponding to the value is formed at the center of the cell. When the value of the multi-value data is 0, no pit is formed.

  The distance between the centers of adjacent cells is called a cell period (Tcell). The relationship between the wobble period and the cell period is preferably such that the wobble period is an integral multiple of the cell period in order to simplify the configuration of the clock signal generation circuit described later. It should be noted that even if the wobble period is 0.25 times or 0.5 times the cell period, it can be dealt with if the 2-4 wobble period matches the integer multiple of the cell period.

  In the portion where the pit is formed, the reflectance of the laser beam decreases as the area of the pit increases. Therefore, a reproduction signal (RF signal) generated from the laser beam reflected on the recording surface of the optical disk is shown in FIG. As shown, the maximum level (L0) is obtained when the value of the multilevel data is 0, and the minimum level (L7) is obtained when the value of the multilevel data is 7. The signal levels when the multi-value data is 1 to 6 are L1 to L6.

  Here, the meandering width Wwbl will be described.

  An example of the measurement result of the C / N (carrier / noise) value indicating the signal quality of the wobble signal is shown in FIGS. FIG. 6A shows the C / N value of the wobble signal obtained from the area recorded by the binary recording method. 6B and 6C show the C / N values of the wobble signal obtained from the area recorded by the 8-value multi-value recording method. Here, FIG. 6B shows a case where the band limitation is not performed when recording data is modulated, and FIG. 6C shows a case where the band limitation is performed. In FIGS. 6A to 6C, recording is performed on the same optical disk at the same clock cycle.

  According to this, as shown in FIG. 7, the result that the quality deterioration of the wobble signal is less in the multi-value recording method than in the binary recording method. In the binary recording method (for example, DVD + RW), data is recorded using marks and spaces having a length of 3T to 14T (T is a clock cycle). Therefore, when a mark and a space having a length of about 5T or more are continuous, The reproduction signal changes with a maximum amplitude. On the other hand, in the multi-level recording method (eight values here), the reproduction signal changes with the maximum amplitude only when the minimum level L7 continues immediately after the maximum level L0 continues or vice versa. . That is, in the multilevel recording method, the frequency of the reproduction signal changing with the maximum amplitude is less than that in the binary recording method, so that the leakage of the reproduction signal into the wobble signal is smaller than in the case of the binary recording method, and the wobble It is considered that deterioration of the signal quality of the signal is suppressed.

  Therefore, the optical disk using the multi-level recording system can have a narrower meandering width than the optical disk using the binary recording system. For example, a DVD + RW using a binary recording method employs a meandering width of about ± 4% of the track pitch. Therefore, in an optical disc using a multi-value recording system, the meandering width is about ± 2.4% of the pit row pitch when band limitation is performed, and ± 3.4 of the pit row pitch when band limitation is not performed. If it is about%, it is possible to obtain a wobble signal of the same quality as in the binary recording system. Therefore, in this embodiment, since the pit row pitch TP is 0.74 μm and the band is limited, the meandering width Wwbl is set to ± 17.8 nm.

  As described above, in the multilevel recording method, the meandering width can be made narrower than in the binary recording method, so that the wobble component leaking into the reproduction signal is reduced, and the quality deterioration of the reproduction signal due to the wobble component is suppressed. it can.

  Next, the data format of data recorded on the optical disc 15 will be described. Assuming that a group of data for one address (logical address) is one data block, in this embodiment, as shown in FIG. 8 as an example, one data block has three clock marks (hereinafter “CM”) as reference marks. Are also inserted at regular intervals. Hereinafter, the CM insertion interval is also referred to as a CM cycle (Tcmk). Further, a synchronization mark indicating an information delimiter is arranged between the leading CM and the data.

  The CM is a mark for specifying the center position of the cell, and here, as an example, a multi-value data string “00700” is used as shown in FIG. That is, the CM has a size of 5 cells, and the third cell has a maximum area pit, and the other cells have no pit. Therefore, this CM playback signal (hereinafter also referred to as “CM signal” for convenience) is a “V-shaped” signal having a bottom value (L7) corresponding to the center of the third cell, as shown in FIG. Become. Therefore, since there are two cells each storing a fixed value (here, 0) before and after the central cell, for example, even when the cell size is small with respect to the spot diameter of the light spot, The CM can be easily detected, and the center position of the cell can be specified from the timing indicating the bottom value (L7).

  As the synchronization mark, as shown in FIG. 10, for example, a multi-value data string “00007777” is used. This pattern of the multi-value data string is a pattern that does not appear in the user data. The reproduction signal of the synchronization mark (hereinafter also referred to as “synchronization signal” for the sake of convenience) is composed of a maximum level (L0) for four cells and a minimum level (L7) for four cells, as shown in FIG. Signal. Therefore, the synchronization mark is easily detected, and for example, the start position of information can be obtained.

  Incidentally, the physical address added to the wobble signal and the logical address recorded as data in the pit string must be uniquely associated with the absolute position on the optical disc. In order to ensure this association, the length of one data block (hereinafter also referred to as “data block length”) and the length of one wobble block (hereinafter also referred to as “wobble block length”) have a predetermined relationship. Necessary. For example, when the data block length and the wobble block length are equal to each other, the association between the physical address and the logical address is easy. Even if both block lengths are not the same, for example, when two wobble blocks correspond to one data block, the association between the physical address and the logical address is easy.

  Further, when detecting a CM, the wobble signal becomes a noise component, and when detecting a wobble signal, the CM becomes a noise component.

  Therefore, the relationship between the CM cycle Tcmk and the wobble cycle Twbl is provided with regularity so that the association between the physical address and the logical address is easy and both the CM and the wobble signal can be detected with high accuracy. Here, when m = Tcmk / Tcell and n = Twbl / Tcell, the relationship between m and n will be described with reference to FIG. In FIG. 11, for the sake of convenience, the wobble period Twbl is shown to change, but here, the CM period Tcmk changes.

<< When m = n >>
In the case of m = n, CMs can be arranged at positions where the meandering phase is always the same.

  As shown in the wobble signal 2 of FIG. 11, when the CM is arranged at a position where the meandering phase is 0 degree, the spot center at the CM position is always located substantially at the center of the pit row. Thereby, when detecting the CM, noise due to the wobble signal is reduced, and the CM can be detected with high accuracy. Further, when detecting the wobble signal, the noise caused by the CM is reduced, and the wobble signal can be detected with high accuracy. The same applies when the CM is arranged at a position where the meandering phase is 180 degrees.

  When the CM is arranged at a position where the meandering phase is 90 degrees or 270 degrees, the center of the spot is shifted from the center of the pit row, but the shift amount is almost constant. In this case, the noise due to the wobble signal when detecting the CM is not small, but the noise level is always almost the same. Therefore, it is possible to easily remove the noise component by acquiring the noise level in advance. Is possible. Similarly, the noise caused by CM when detecting a wobble signal is not small, but the noise level is always almost the same, so it is possible to easily remove the noise component by acquiring the noise level in advance. It is. Accordingly, both the CM and the wobble signal can be detected with high accuracy.

  When a multi-value data string having a pattern similar to the CM signal and the wobble signal is used as the CM, the CM is preferably arranged at a position where the meandering phase is 90 degrees or 270 degrees. When generating a clock signal from a normal wobble signal, the level of the amplitude center of the wobble signal is used as a reference, so that when the CM signal and the wobble signal are similar, the meandering phase is 0 degrees or 180 degrees. If the CM is arranged at a certain position, the level of the amplitude center may fluctuate due to leakage of the CM signal, and the accuracy of the clock signal may decrease. However, if the CM is arranged at a position where the meandering phase is 90 degrees or 270 degrees, the level fluctuation of the amplitude center can be reduced even when the CM signal and the wobble signal are similar.

  Further, the CM may be arranged at a position where the meandering phase is 45 degrees or 135 degrees. In this case, as in the case where the CM is arranged at a position where the meandering phase is 90 degrees or 270 degrees, the noise component can be easily removed, so both the CM and the wobble signal can be accurately obtained. It becomes possible to detect.

<< When m = n / 2 >>
When m = n / 2, two CMs are inserted in one wobble period. Also in this case, the CM can be arranged at a position where the meandering phase is always the same.

  As shown in the wobble signal 1 in FIG. 11, when CMs are respectively arranged at the meandering phases of 0 degrees and 180 degrees, the spot center at the CM position is always located substantially at the center of the pit row. . Thereby, when detecting the CM, noise due to the wobble signal is reduced, and the CM can be detected with high accuracy. Further, when detecting the wobble signal, the noise caused by the CM is reduced, and the wobble signal can be detected with high accuracy.

  In this case, since the frequency of CM insertion increases and the length of the CM needs to be shortened in order to ensure the data recording capacity, there are many patterns in which the CM signal and the wobble signal are similar. There is no possibility that the value data string is used as a CM, and there is no merit of arranging the CM at a position where the meandering phase is 90 degrees or 270 degrees.

  In this case, since the cycle of the clock signal obtained from the CM is equal to the cycle of the clock signal obtained from the wobble signal, the parameters of the PLL circuit may be the same in the clock signal generation circuit described later. It becomes possible and control becomes easy.

<< When m = a * n >>
When m = a × n (a is an integer), one CM is inserted in the wobble a cycle. Also in this case, the CM can be arranged at a position where the meandering phase is always the same. An example when a = 2 is shown as wobble signals 3 and 4 in FIG. 11, and an example when a = 3 is shown as wobble signal 5 in FIG.

  As shown in the wobble signal 3 in FIG. 11, when the CM is arranged at one of the positions where the meandering phase is 0 degree, the spot center at the CM position is always located substantially at the center of the pit row. Thereby, when detecting the CM, noise due to the wobble signal is reduced, and the CM can be detected with high accuracy. Further, when detecting the wobble signal, the noise caused by the CM is reduced, and the wobble signal can be detected with high accuracy. The same applies when the CM is arranged at one of the positions where the meandering phase is 180 degrees.

  Further, as shown in the wobble signal 4 of FIG. 11, when the CM is arranged at one of the positions where the meandering phase is 90 degrees, the spot center is shifted from the center of the pit row. The amount of deviation is almost constant. In this case, the noise due to the wobble signal when detecting the CM is not small, but the noise level is always almost the same. Therefore, it is possible to easily remove the noise component by acquiring the noise level in advance. Is possible. Similarly, the noise caused by CM when detecting a wobble signal is not small, but the noise level is always almost the same, so it is possible to easily remove the noise component by acquiring the noise level in advance. It is. Accordingly, both the CM and the wobble signal can be detected with high accuracy. The same is true when the CM is arranged at one of the positions where the meandering phase is 270 degrees.

  Furthermore, as shown in the wobble signal 5 in FIG. 11, when the CM is arranged at one of the positions where the meandering phase is 45 degrees, the spot center is shifted from the center of the pit row. The amount of deviation is almost constant. In this case, as in the case where the CM is arranged at one of the positions where the meandering phase is 90 degrees, the noise component can be easily removed, so that both the CM and the wobble signal can be accurately obtained. It becomes possible to detect. The same applies when the CM is arranged at one of the positions where the meandering phase is 135 degrees, 225 degrees, and 315 degrees.

  Note that the reproduction clock signal generated from the CM and the reference clock signal generated from the wobble signal are each required to have stability within an allowable accuracy, and therefore the value of a is limited. Therefore, using a virtual clock signal generation circuit VC as shown in FIG. 12A, jitter (hereinafter also referred to as “clock jitter”) in the generated clock signal was obtained by simulation. The clock signal generation circuit VC includes a binarization circuit V1 that binarizes an input signal S1, and a PLL circuit V2 that generates a clock signal S3 based on the signal S2 binarized by the binarization circuit V1. And a frequency divider V3 that divides the clock signal S3 and makes a phase comparison with the signal S2 by the PLL circuit V2. The characteristics of the PLL circuit V2 are general, and the cell frequency is 25 MHz and the crossing frequency is about 2.6 kHz. FIG. 12B shows, as an example of the simulation result, the relationship between the cycle of the signal S2 (hereinafter also referred to as “edge cycle”) and the clock jitter in the clock signal S3 for each signal quality of the signal S1. Yes.

  The quality of the wobble signal is about 45 dB (when not recorded), referring to the recordable CD or DVD currently on the market. The allowable jitter of the reference clock signal may be empirically 5% or less of the cell period. Therefore, when the signal S1 is a wobble signal, it can be seen from FIG. 12B that the period of the signal S2 should be 80 cells or less from the quality and jitter conditions of the wobble signal. In the case of the wobble signal, the phase comparison can be performed at the rising edge and the falling edge, so that the wobble cycle can be extended to 160 cells. From the viewpoint of band separation from multilevel data, the wobble period is preferably 1/10 or less of the frequency of the minimum repetitive pattern at which data changes for each cell. That is, the wobble period is preferably 20 times or more of the cell period. Therefore, n (= Twbl / Tcell) is an integer of 20 to 160. In the recorded area, the quality of the wobble signal varies slightly depending on the recording method.

  The quality of the CM signal is higher than that of the wobble signal, and 55 dB or more is obtained. Further, the allowable jitter of the recovered clock signal is empirically required to be 5% or less of the cell period. Therefore, when the signal S1 is a CM signal, the quality and jitter of the CM signal are determined from FIG. From the conditions, it can be seen that the period of the signal S2 should be 260 cells or less. However, if the CM insertion frequency is increased, the CM detection accuracy is improved, but the amount of data information is reduced. Therefore, it is desirable to keep the ratio of CM in the total information amount within 10%. Accordingly, m (= Tcmk / Tcell) is an integer of 50 to 260. Therefore, the maximum value of a is 13 (= 260/20).

  That is, as for the relationship between m and n, any of m = n, m = n / 2, and m = n × a may be satisfied.

  FIG. 13 shows a schematic configuration of an optical disc apparatus 20 according to an embodiment of the present invention. The optical disk apparatus 20 shown in FIG. 13 includes a spindle motor 22 for rotating the optical disk 15, an optical pickup apparatus 23, a seek motor 21 for driving the optical pickup apparatus 23 in the sledge direction, and a laser control circuit 24. An encoder 25, a servo control circuit 26, a reproduction signal processing circuit 28, a buffer RAM 34, a buffer manager 37, an interface 38, a flash memory 39, a CPU 40, a RAM 41, and the like. Note that the arrows in FIG. 13 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block. Further, the optical disk device 20 is also compatible with recordable optical disks (for example, DVD-R, DVD-RW, DVD + R, DVD + RW).

  The optical pickup device 23 is a device for irradiating the recording surface of the optical disc 15 with laser light and receiving reflected light from the recording surface. As shown in FIG. 14A as an example, the optical pickup device 23 includes a light source unit 51, a coupling lens 52, a beam splitter 54, an objective lens 60, a detection lens 58, a light receiver PD, and an I / V amplifier 62. , And a drive system 61 for driving the objective lens 60.

  The light source unit 51 includes a semiconductor laser LD as a light source that emits laser light having a wavelength of about 660 nm. In the present embodiment, the maximum intensity emission direction of the laser light emitted from the light source unit 51 is the + X direction. The coupling lens 52 is disposed on the + X side of the light source unit 51, and the light beam emitted from the light source unit 51 is made to be substantially parallel light.

  The beam splitter 54 is disposed on the + X side of the coupling lens 52, transmits the light beam from the coupling lens 52 as it is, and branches the light beam (return light beam) reflected by the optical disk 15 in the -Z direction. The objective lens 60 is disposed on the + X side of the beam splitter 54, and the light beam transmitted through the beam splitter 54 is condensed on the recording surface of the optical disk 15.

  The detection lens 58 is disposed on the −Z side of the beam splitter 54 and condenses the return light beam branched in the −Z direction by the beam splitter 54 on the light receiving surface of the light receiver PD. As shown in FIG. 14B as an example, the light receiving surface of the light receiver PD is perpendicular to the dividing line DL1 in the direction corresponding to the tangential direction of the pit row of the optical disc 15 and the dividing line DL1. It is divided into four parts (light receiving areas Da, Db, Dc and Dd) by a dividing line (DL2). Each light receiving region generates a signal corresponding to the amount of received light by photoelectric conversion.

  The I / V amplifier 62 converts a signal from each light receiving region of the light receiver PD into a voltage signal, amplifies it with a predetermined gain, and outputs it to the reproduction signal processing circuit 28.

  The drive system 61 includes a focusing actuator for minutely driving the objective lens 60 in the focus direction that is the optical axis direction of the objective lens 60 and a small amount of the objective lens 60 in the tracking direction that is perpendicular to the tangential direction of the pit row. And a tracking actuator for driving.

  Returning to FIG. 13, the reproduction signal processing circuit 28 includes a servo signal detection circuit 28b, a wobble signal detection circuit 28c, an RF signal detection circuit 28d, a decoder 28e, a clock signal generation circuit 28f, a demodulation circuit 28g, and the like. .

  The servo signal detection circuit 28b detects servo signals such as a focus error signal and a track error signal based on the output signal of the I / V amplifier 62. The servo signal detected here is output to the servo control circuit 26.

  The RF signal detection circuit 28d detects an RF signal based on the output signal of the I / V amplifier 62. The RF signal detected here is output to the clock signal generation circuit 28f and the decoder 28e.

  The wobble signal detection circuit 28 c detects a wobble signal based on the output signal of the I / V amplifier 62. The wobble signal detected here is output to the clock signal generation circuit 28f and the demodulation circuit 28g.

  FIG. 15 shows a specific example of a circuit in which the servo signal detection circuit 28b, the RF signal detection circuit 28d, and the wobble signal detection circuit 28c are combined. The circuit shown in FIG. 15 has six adders (281 to 286), two subtractors (287 and 288), and four filters (291 to 294). The adder 281 adds four signals (Va, Vb, Vc, and Vd) from the I / V amplifier 62. The signals Va, Vb, Vc, and Vd are output signals of the I / V amplifier 62 corresponding to the output signals of the light receiving areas Da, Db, Dc, and Dd of the light receiver PD, respectively. The output signal of the adder 281 has a wide band and is output as an RF signal Srf to the clock signal generation circuit 28f and the decoder 28e.

  The adder 282 adds the signal Va and the signal Vd, and the adder 283 adds the signal Vb and the signal Vc. The adder 284 adds the signal Va and the signal Vc, and the adder 285 adds the signal Vb and the signal Vd. The adder 286 adds the output signal of the adder 282 and the output signal of the adder 283. The subtracter 287 subtracts the output signal of the adder 283 from the output signal of the adder 282. The subtracter 288 subtracts the output signal of the adder 285 from the output signal of the adder 284.

  The filter 291 removes a low-frequency component included in the output signal of the subtracter 287. The output signal of the filter 291 is a high-frequency signal, and is output to the clock signal generation circuit 28f and the demodulation circuit 28g as a wobble signal Swb.

  The filter 292 removes a high frequency component contained in the output signal of the subtracter 287. The output signal of the filter 292 is a low frequency signal and is output to the servo control circuit 26 as a track error signal Str. That is, the track error signal Str is obtained by a so-called push-pull method.

  The filter 293 removes a high frequency component contained in the output signal of the adder 286. The output signal of the filter 293 is a low frequency signal and is output to the servo control circuit 26 as a track cross signal Stc.

  The filter 294 removes a high frequency component contained in the output signal of the subtracter 288. The output signal of this filter 294 is a low frequency signal and is output to the servo control circuit 26 as a focus error signal Sfe. That is, the focus error signal Sfe is acquired by a so-called astigmatism method.

  The clock signal generation circuit 28f generates a reproduction clock signal (referred to as Rck) based on the RF signal, and generates a reference clock signal (referred to as Wck) based on the wobble signal. Here, as shown in FIG. 16, as an example, the clock signal generation circuit 28f includes a reproduction clock signal generation circuit Kr that generates the reproduction clock signal Rck and a reference clock signal generation circuit Kw that generates the reference clock signal Wck. is doing.

  The reproduction clock signal generation circuit Kr includes a CM detection circuit f1, a bottom detection circuit f2, a PLL circuit f3, and a frequency divider f4. The CM detection circuit f1 monitors the RF signal and detects the CM signal. The bottom detection circuit f2 detects the bottom position of the CM signal detected by the CM detection circuit f1. Therefore, the output signal of the bottom detection circuit f2 is a pulse signal synchronized with the CM cycle as shown in FIG. 17 as an example. Here, since the CM cycle is m times the cell cycle, the PLL circuit f3 generates a signal obtained by multiplying the frequency of the output signal of the bottom detection circuit f2 by m times (see FIG. 17). The output signal of the PLL circuit f3 is supplied as a reproduction clock signal Rck to the decoder 28e and the like. Note that the output signal of the PLL circuit f3 is subjected to phase comparison with the output signal of the bottom detection circuit f2, so that it is frequency-divided by m by the frequency divider f4 and then input to the PLL circuit f3. As a result, a stable reproduction clock signal Rck is output.

  The reference clock signal generation circuit Kw includes a binarization circuit f5, a PLL circuit f6, and a frequency divider f7. The binarization circuit f5 binarizes the wobble signal with reference to the amplitude center level. Since the wobble cycle is n times the cell cycle, the PLL circuit f6 generates a signal that is n times the frequency of the output signal of the binarization circuit f5. The output signal of the PLL circuit f6 is supplied as a reference clock signal Wck to the encoder 25, the servo control circuit 26, and the like. Note that the output signal of the PLL circuit f6 is subjected to phase comparison with the output signal of the binarization circuit f5, and after being frequency-divided by n by the frequency divider f7, is input to the PLL circuit f6. As a result, a stable reference clock signal Wck is output. The output signal of the frequency divider f7 is supplied to the demodulation circuit 28g.

  Returning to FIG. 13, the decoder 28e acquires multi-value data from the RF signal in synchronization with the recovered clock signal Rck, performs decoding processing, error detection processing, and the like. When an error is detected, error correction processing is performed. Is stored in the buffer RAM 34 via the buffer manager 37 as reproduction data. Here, since the center of the cell is accurately identified by the reproduction clock signal Rck, it is possible to obtain the reproduction data stably and accurately. The RF signal includes address data, and the decoder 28e outputs the address data extracted from the RF signal to the CPU 40. This address data is logical address data.

  The demodulation circuit 28g demodulates the wobble information part based on the wobble signal and the output signal of the frequency divider f7, and acquires address data or media parameters. The address data and media parameters obtained here are supplied to the CPU 40.

  The servo control circuit 26 includes a PU control circuit 26a, a seek motor control circuit 26b, and an SP motor control circuit 26c.

  The PU control circuit 26 a generates a focusing actuator drive signal based on the focus error signal and outputs it to the optical pickup device 23 in order to correct the focus shift of the objective lens 60. The PU control circuit 26 a generates a tracking actuator drive signal based on the track error signal and outputs the tracking actuator drive signal to the optical pickup device 23 in order to correct the tracking deviation of the objective lens 60. Thereby, tracking control and focus control are performed.

  The seek motor control circuit 26 b generates a drive signal for driving the seek motor 21 based on an instruction from the CPU 40 and outputs the drive signal to the seek motor 21.

  The SP motor control circuit 26 c generates a drive signal for driving the spindle motor 22 based on an instruction from the CPU 40 and outputs the drive signal to the spindle motor 22. Further, the disk rotational speed is detected based on the reference clock signal, and the rotational speed of the spindle motor 22 is controlled by comparison with the target speed.

  The buffer RAM 34 temporarily stores data reproduced from the optical disc 15 (reproduced data) and the like. Data input / output to / from the buffer RAM 34 is managed by the buffer manager 37. When a recordable optical disk is set, the recording data sent from the host device 90 is accumulated in the buffer RAM 34.

  When a recordable optical disc is set, the encoder 25 takes out the recording data stored in the buffer RAM 34 based on an instruction from the CPU 40 via the buffer manager 37, and converts the data modulation and error correction code. Addition is performed to generate a write signal. The write signal generated here is output to the laser control circuit 24.

  The laser control circuit 24 controls the power of laser light emitted from the semiconductor laser LD. Here, since the optical disk 15 is exclusively for reproduction, the laser control circuit 24 generates a drive signal for the semiconductor laser LD corresponding to the reproduction power. When recording is performed on a recordable optical disk, the laser control circuit 24 generates a drive signal for the semiconductor laser LD based on the write signal, recording conditions, light emission characteristics of the semiconductor laser LD, and the like.

  The interface 38 is a bidirectional communication interface with a host device 90 (for example, a personal computer), and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface) and SCSI (Small Computer System Interface).

  The flash memory 39 includes a program area and a data area. In the program area of the flash memory 39, a program written in a code decodable by the CPU 40 is stored. The data area of the flash memory 39 stores recording conditions, light emission characteristics of the semiconductor laser LD, and the like.

  The CPU 40 controls the operation of each unit in accordance with the program stored in the program area of the flash memory 39, and stores data necessary for control in the RAM 41 and the buffer RAM 34.

  As is apparent from the above description, in the optical disc apparatus 20 according to the present embodiment, the reproduction clock signal generation circuit Kr constitutes the clock signal generation means, and the decoder 28e constitutes the reproduction means. The wobble signal detection circuit 28c constitutes a wobble signal detection means.

  In the reproduction clock signal generation circuit Kr, a step of detecting a reference mark and a step of generating a clock signal in the signal generation method according to the present invention are performed.

  As described above, according to the optical disc 15 according to the present embodiment, a plurality of CMs (reference marks) are included in the multivalued information in correspondence with the meander cycle of the pit row. In addition, the CM can be detected with high accuracy without being affected by meandering. Therefore, by referring to the reference mark, it is possible to accurately obtain the position where the multivalued information is recorded.

  Further, since the CM is formed at a position where the spot center and the center position of the pit row substantially coincide or at a position where the deviation amount between the spot center and the center position of the pit row becomes a predetermined value, the CM and the wobble signal Can be detected with high accuracy.

  Further, any relationship of m = n, m = n / 2, and m = n × a is satisfied between the number of cells m included in the CM period and the number n of cells included in the wobble period. Therefore, both the CM and the wobble signal can be detected with high accuracy.

  In addition, since m is an integer of 50 to 260, it is possible to generate a reproduction clock signal with high accuracy without significantly reducing the amount of recordable information.

  Further, since n is an integer of 20 to 160, the reference clock signal can be generated with high accuracy.

  In addition, since the address information (phase modulation wave unit) in the wobble information unit is phase-modulated with the same period as that of the carrier wave unit, the wobble information can be easily demodulated.

  Furthermore, since the CM is added to the synchronization mark, the synchronization mark can be detected with high accuracy, and the delimiter of information can be easily clarified.

  In addition, according to the optical disk device 20 according to the present embodiment, a spiral or concentric pit row has a recording surface formed by periodically meandering, and multi-valued information includes a plurality of CMs (references). When reproducing the optical disk 15 in which the mark) has a corresponding relationship with the meandering period, the CM is detected based on the reflected light from the recording surface of the optical disk 15, and the reproduction clock signal is based on the CM. (Clock signal) is generated. Here, since the CM is formed in correspondence with the meandering cycle of the pit row, the CM is accurately detected without being affected by the meandering, so that the reproduced clock signal is accurately stabilized. Generated. As a result, the information recorded on the optical disk 15 is stably reproduced. That is, information recorded on the optical disc of the present invention can be stably reproduced.

  In the clock signal generation circuit 28f of the above embodiment, a reproduction clock signal generation circuit Kr ′ shown in FIG. 18 may be used instead of the reproduction clock signal generation circuit Kr. The reproduction clock signal generation circuit Kr ′ generates a pseudo clock signal (pulse signal) based on the wobble signal, and generates a reproduction clock signal based on the pseudo clock signal and CM. That is, coarse synchronization clock pull-in is performed with a wobble signal, and fine synchronization clock pull-in is performed with a reproduction signal. Therefore, the reproduction clock signal generation circuit Kr ′ has a configuration in which a changeover switch f8, a frequency divider f9, and a synchronization detection circuit f10 are added to the reproduction clock signal generation circuit Kr.

  The frequency divider f9 divides the reference clock signal Wck from the reference clock signal generation circuit Kw by m. The changeover switch f8 selects one of the output signal of the frequency divider f9 and the output signal of the bottom detection circuit f2, and outputs the selected signal to the PLL circuit f3. The synchronization detection circuit f10 detects a synchronization state based on the output signal of the PLL circuit f3 and controls the changeover switch f8.

  Here, the operation of the reproduction clock signal generation circuit Kr ′ will be briefly described. First, the synchronization detection circuit f10 sets the changeover switch f8 to the frequency divider f9 side. As a result, the output signal of the frequency divider f9 is supplied to the PLL circuit f3, and a rough frequency pull-in, that is, coarse synchronization is performed in the PLL circuit f3. When the frequency roughly matches the coarse synchronization, the synchronization detection circuit f10 sets the changeover switch f8 to the bottom detection circuit f2 side. As a result, the output signal of the bottom detection circuit f2 is supplied to the PLL circuit f3, and the PLL circuit f3 performs accurate frequency pulling, that is, fine synchronization. Therefore, it is possible to generate the reproduction clock signal more quickly than the reproduction clock signal generation circuit Kr.

  In this case, when m is a natural number multiple of n, as shown in FIG. 19 as an example, the output signal of the binarization circuit f5 is used instead of the frequency divider f9 in the reproduction clock signal generation circuit Kr ′. A reproduction clock signal generation circuit Kr ″ having a frequency divider f11 that divides m / n may be used. In the case of coarse synchronization, the output signal of the frequency divider f11 is selected by the changeover switch f8, and in the case of fine synchronization, The output signal of the bottom detection circuit f2 is selected by the changeover switch f8, so that, for example, the reference clock signal is unnecessary, and even when the PLL circuit f6 constituting the reference clock signal generation circuit Kw is not operating, the recovered clock signal Can be generated quickly.

  In the above embodiment, the case where the address information is phase-modulated with the same period as that of the carrier wave is described. However, the present invention is not limited to this. For example, as shown in FIG. It may be modulated. In this case, if the CM period and the wobble period are equal to each other, the CM can be arranged at a position where the spot center and the center position of the pit row substantially coincide.

  Moreover, although the case where three CMs are inserted in one data block has been described in the above embodiment, the present invention is not limited to this. For example, one CM may be inserted in one data block.

  In the above embodiment, the case where the first CM of the data block and the synchronization mark are individually arranged has been described. However, for example, when the center of the cell can be specified by the synchronization mark, FIG. As shown in FIG. 4, there is no need for a CM in front of the synchronization mark. For example, as shown in FIG. 21B, when the multilevel data string “007000777” is used as a synchronization mark, the center of the cell can be specified by the five cells ahead.

  In the above-described embodiment, the case where the multi-value data string “00007777” is used as the synchronization mark has been described. However, the present invention is not limited to this. For example, as shown in FIG. 22, a multi-value data string “007770077” may be used as a synchronization mark. In short, any pattern that does not appear in user data may be used.

  In the above-described embodiment, the case where the multi-value data string “00700” is used as the CM has been described. However, the present invention is not limited to this. For example, as shown in FIG. 23, a multi-value data string “0077” may be used as a CM. In this case, a clock signal is generated based on the amplitude center of the reproduction signal. That is, since the timing of the cell boundary can be obtained by detecting the timing crossing the amplitude center, when the clock signal having the rising edge at the cell boundary is generated, the length of the cell is known, and as shown in FIG. In addition, a clock signal whose falling edge indicates the center of the cell can be easily generated. Therefore, in this case, the reproduction clock signal generation circuit Krc shown in FIG. 24 is used instead of the reproduction clock signal generation circuit Kr in the above embodiment. In the reproduction clock signal generation circuit Krc, an amplitude center detection circuit f2 ′ for detecting the amplitude center of the reproduction signal is used instead of the bottom detection circuit f2 in the reproduction clock signal generation circuit Kr.

  In the above embodiment, the case where the recording data is multi-valued to 8 values has been described, but the present invention is not limited to this.

  In the above embodiment, the case where the track error signal is acquired by the push-pull method has been described. However, the present invention is not limited to this. For example, a phase difference method (DPD method) may be used. Further, the light beam emitted from the semiconductor laser LD may be divided into three beams, and a three-spot method and a differential push-pull (DPP) method may be used. In short, it is sufficient that the track error signal is detected with high quality. The configurations of the optical pickup device 23 and the reproduction signal processing circuit 28 correspond to the detection method.

  In the above embodiment, the case where the focus error signal is acquired by the astigmatism method has been described. However, the present invention is not limited to this. For example, a knife edge method may be used. In short, it is sufficient that the focus error signal is detected with good quality. The configurations of the optical pickup device 23 and the reproduction signal processing circuit 28 correspond to the detection method.

  Moreover, although the said embodiment demonstrated the case where the light-receiving surface of light receiver PD was divided into four, it is not limited to this. In short, the servo signal, the RF signal, and the wobble signal may be detected with high quality.

  In the above embodiment, the meandering width is set to ± 17.8 nm, but may be changed according to the band limiting method.

  In the above embodiment, the case where band limitation is performed when recording data is modulated has been described. However, the present invention is not limited to this, and band limitation may not be performed. In this case, the meandering width is preferably ± 25.2 nm.

  In the above embodiment, the case where the wobble period is 5 μm and the pit row pitch is 0.74 μm has been described, but the present invention is not limited to this. Therefore, for example, if the pitch of the pit row is 0.45 μm, the meandering width when band limitation is performed is preferably ± 10.8 nm, and the meandering width when band limitation is not performed is preferably ± 15.3 nm. For example, when the pit row pitch is 0.32 μm, the meandering width when band limitation is performed is preferably ± 7.7 nm, and the meandering width when band limitation is not performed is preferably ± 10.9 nm.

  In the above embodiment, the case where one wobble unit is 93 wobbles has been described. However, the present invention is not limited to this.

  In the above embodiment, a case where wobble number 0 to wobble number 7 is a wobble information part and wobble number 8 to wobble number 92 is a carrier part in one wobble unit has been described. However, the present invention is not limited to this. .

  Moreover, although the said embodiment demonstrated the case where 51 bits were required as address data, it is not limited to this. In this case, the number of wobble units constituting one wobble block is defined according to the number of bits of the address data.

  In the above embodiment, when the period of the reproduction signal is close to the period of the wobble signal, the phase comparison in the PLL circuit f6 in the reference clock signal generation circuit Kw is temporarily stopped at the synchronization mark position. May be.

  In the above embodiment, the case where the light receiver PD and the I / V amplifier 62 are individually provided has been described. However, the present invention is not limited to this, and the light receiver PD and the I / V amplifier 62 may be integrated. .

  In the above embodiment, the optical disk corresponds to a laser beam having a wavelength of about 660 nm. However, the present invention is not limited to this. For example, the laser beam has a wavelength of about 780 nm and a wavelength of about 405 nm. It is possible to correspond to the laser beam.

  Further, in the above-described embodiment, the case where the pit area is different depending on the value of the multi-value data has been described. Also good. In short, it is only necessary that the signal level of the reproduction signal differs depending on the value of the multi-value data.

  In the above embodiment, the case where the optical pickup device includes one semiconductor laser has been described. However, the present invention is not limited thereto, and for example, a plurality of semiconductor lasers that emit light beams having different wavelengths may be included. In this case, for example, at least one of a semiconductor laser that emits a light beam with a wavelength of about 405 nm, a semiconductor laser that emits a light beam with a wavelength of about 660 nm, and a semiconductor laser that emits a light beam with a wavelength of about 780 nm may be included. . That is, the optical disk apparatus may be an optical disk apparatus that supports a plurality of types of optical disks that conform to different standards. At this time, the multi-level recording method may be used for at least one of the plurality of types of optical discs.

  In the above embodiment, the case where the optical disk apparatus is an optical disk apparatus capable of recording and reproduction has been described. However, a reproduction-only optical disk apparatus may be used.

FIG. 1A and FIG. 1B are diagrams for explaining the recording surface of an optical disc according to an embodiment of the present invention. It is a figure for demonstrating a wobble unit. It is a figure for demonstrating the phase modulation of a wobble information part. It is a figure for demonstrating a wobble block. It is a figure for demonstrating a cell and a pit. FIGS. 6A to 6C are waveform diagrams showing the signal quality of the wobble signal. It is a figure for demonstrating the difference in the signal quality of the wobble signal by a recording system. It is a figure for demonstrating the structure of a data block. It is a figure for demonstrating a clock mark (CM). It is a figure for demonstrating a synchronization mark. It is a figure for demonstrating the relationship between a wobble period and CM period. FIG. 12A is a block diagram for explaining a virtual clock signal generation circuit used for simulating the relationship between the edge period and the clock jitter, and FIG. 12B is for explaining the simulation result. FIG. 1 is a block diagram showing a configuration of an optical disc device according to an embodiment of the present invention. FIG. 14A is a diagram for explaining the configuration of the optical pickup device in FIG. 13, and FIG. 14B is a diagram for explaining the light receiver in FIG. 14A. It is a figure for demonstrating the specific circuit structure of the servo signal detection circuit in FIG. 13, a wobble signal detection circuit, and RF signal detection circuit. It is a figure for demonstrating the clock signal generation circuit in FIG. FIG. 17 is a diagram for explaining the operation of the reproduction clock signal generation circuit of FIG. 16. It is a figure for demonstrating the modification (the 1) of a clock signal generation circuit. It is a figure for demonstrating the modification (the 2) of a clock signal generation circuit. It is a figure for demonstrating the modification of the phase modulation in a wobble information part. FIG. 21A is a diagram for explaining a data block when the synchronization mark has a CM function, and FIG. 21B is a diagram for explaining the synchronization mark at that time. It is a figure for demonstrating the modification of a synchronous mark. It is a figure for demonstrating the modification of CM. It is a figure for demonstrating a clock signal generation circuit when CM of FIG. 23 is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 ... Optical disk, 20 ... Optical disk apparatus, 28c ... Wobble signal detection circuit (wobble signal detection means), 28e ... Decoder (reproduction means), CM ... Clock mark (reference mark), Kr ... Reproduction clock signal generation circuit (Clock signal generation) means).

Claims (14)

An optical disc having a recording surface in which a plurality of pits corresponding to information multi-valued to three or more values is formed as a pit row in a spiral shape or a concentric shape,
The pit row meanders periodically,
An optical disc in which a plurality of predetermined reference marks corresponding to the meandering cycle are included in the pit row.   The optical disc according to claim 1, wherein the reference mark is included in a period that is ½ of the period of the meandering.   The optical disc according to claim 1, wherein the reference mark is included in a period that is an integral multiple of the meandering period.   The optical disk according to claim 1, wherein the reference mark is included at a position where the meandering phase has a predetermined value.   The optical disc according to claim 4, wherein the predetermined value is 0 degree or 180 degrees. The information includes a synchronization mark indicating a break of information at a predetermined period,
6. The optical disc according to claim 1, wherein the reference mark is included at least for each synchronization mark. The pit row is virtually divided into a plurality of partial areas having the same length in the tangential direction of the pit row,
The optical disc according to any one of claims 1 to 6, wherein the number of the partial areas included in one period of the reference mark is an integer of 50 to 260. The pit row is virtually divided into a plurality of partial areas having the same length in the tangential direction of the pit row,
8. The optical disk according to claim 1, wherein the number of the partial areas included in one cycle of the meander is an integer of 20 to 160. 9. The pit row has a phase modulation wave portion including predetermined information and a carrier wave portion for generating a clock signal,
The optical disk according to claim 1, wherein the phase-modulated wave unit is phase-modulated with the same period as the carrier wave unit. The pit row has a phase modulation wave portion including predetermined information and a carrier wave portion for generating a clock signal,
The optical disk according to claim 1, wherein the phase-modulated wave unit is phase-modulated with a period twice that of the carrier wave unit. A clock signal generation method for generating a clock signal used when reproducing information from the optical disc according to any one of claims 1 to 10,
Detecting a reference mark included in a pit row of the optical disk based on reflected light from the recording surface of the optical disk;
Generating a clock signal based on the reference mark. Further comprising a step of detecting a wobble signal including information on the meandering shape of the pit row based on the reflected light from the recording surface of the optical disc;
In the step of generating the clock signal, a pseudo pulse signal is generated based on the wobble signal, and the clock signal is generated based on the pseudo pulse signal and the reference mark. The clock signal generation method according to claim 11. An optical disc apparatus for reproducing information from the optical disc according to any one of claims 1 to 10,
Clock signal generating means for detecting a reference mark included in a pit row of the optical disk based on reflected light from the recording surface of the optical disk and generating a clock signal based on the reference mark;
An optical disc apparatus comprising: reproducing means for reproducing information recorded on the optical disc using the clock signal. Further comprising wobble signal detection means for detecting a wobble signal including information on the meandering shape of the pit row based on reflected light from the recording surface of the optical disc;
The clock signal generation unit generates a pseudo pulse signal based on the wobble signal, and generates the clock signal based on the pseudo pulse signal and the reference mark. 14. An optical disc device according to item 13.

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