CLV-type recordable optical disk and apparatus for recording information onto the optical disk

CLV-type recordable optical disk includes a plurality of tracks which are formed in such a manner that 2.pi.Tp/.lambda. substantially equals an even-number multiple of 0.5 where Tp is a track pitch and .lambda. is a wavelength of a track wobble. Each of the tracks is divided into a plurality of ECC blocks, and each of the ECC blocks is composed of 16 sectors. Each of the sectors is composed of 26 sync frames. In each of the sectors of the track, information recording areas are set normally in even-numbered sync frames. However, in each portion where there would occur overlap in the information recording area, in the radial direction of the disk, between the track and an adjoining track located inward of the track, the information recording areas are set in odd-numbered sync frames. One piece of address information is divided into a plurality of address information elements and recorded dispersedly in the sync frames across a plurality of the sectors. With such arrangements, the optical disk can minimize adverse influences that would result from cross-talk between wobble signals from the adjoining tracks.

BACKGROUND OF THE INVENTION
 The present invention relates generally to CLV (Constant Linear
 Velocity)-type recordable optical disks having track wobbles and apparatus
 for recording desired information onto such optical disks, and more
 particularly to a technique of minimizing unwanted cross-talk between
 wobble signals from adjoining tracks.
 In recordable optical disks based on CD standards, such as CD-R
 (CD-Recordable) and CD-RW (CD-Rewritable) media, a plurality of tracks are
 previously formed as guide grooves, each of which wobbles typically at a
 fixed frequency of 22.05 kHz and has recorded thereon address (ATIP:
 Absolute Time In-Pregroove) information, indicative of absolute positions
 in the track, in FM-modulated form. The track wobbles are used as
 detection signals for disk rotation control at the time of recording on
 the optical disk, and are also used to generate reference clock pulses for
 the recording. Further, wobble signals detected from the optical disk
 during the recording are FM-demodulated to acquire the address
 information.
 Further, in DVD-R (Digital Versatile Disk-Recordable) media, tracks are
 previously formed as grooves each wobbling typically at a fixed frequency
 of 140 kHz without modulation. Address information is recorded as pre-pits
 in lands (between the grooves). In this case too, the track wobbles are
 used as detection signals for disk rotation control at the time of
 recording on the disk.
 In recording desired information onto such optical disks with the track
 wobbles, however, wobble signals from adjoining tracks tend to be detected
 as cross-talk signals. Particularly, with high-density optical disks, the
 cross-talk would occur in a considerably great amount because the track
 pitch is reduced relative to the size of a light spot irradiated onto the
 disk. With the CLV (Constant Linear Velocity)-type disks, the wobble
 signals, detected by the push-pull scheme, would be greatly modulated in
 both amplitude and phase by the cross-talk signals, resulting in beat
 signals. Thus, in the case where the address information is recorded in
 the track wobbles, the phase modulation by the cross-talk causes the
 address information to jitter, which would prevent accurate data-write
 linking. These jitters also lead to jitters in the recording reference
 clock pulses generated from the wobble signals, which would also prevent
 accurate data-write linking and degrade the quality of recording signals.
 SUMMARY OF THE INVENTION
 In view of the foregoing, it is an object of the present invention to
 provide a recordable optical disk and apparatus for recording information
 onto the optical disk which can minimize influences of cross-talk between
 wobble signals from adjoining tracks to thereby substantially eliminate
 phase modulation of the wobble signals.
 Explanation is given below about influences of cross-talk between wobble
 signals from adjoining tracks in recording/reproduction to/or a CLV
 (Constant Linear Velocity)--type optical disk having track wobbles.
 (1) Definition of Variables and Constants:
 Principal variables and Constants are defined as follows:
 Tp: track pitch;
 .lambda.: wavelength of track wobbles;
 .omega.o: angular frequency of the track wobbles (wobble frequency
 fo=2.pi..omega.o)
 Tc: time required to trace one round of an nth track;
 rn: radial distance of the nth track from the center of the disk when
EQU t=Tc/2; w=2.pi.Tp/.lambda.,
 namely, a difference in the number of wobble waves between adjoining tracks
 (fraction); and
EQU .alpha.=w.lambda./ 2.pi.rn=Tp/rn
 (2) Calculation of Relative Angular Frequency of Wobble Waves:
 Here, relative angular frequencies of the wobble waves in two tracks
 adjoining a particular track (nth track) on both sides of the particular
 track are calculated. First, let's consider a difference in the number of
 the wobble waves in one complete round between the tracks. Using the
 number of the wobble waves in one complete round of the nth track,
 Wn=2.pi.rn/.lambda.,
 the numbers of the wobble waves in the two adjoining (n+1)th and (n-1)th
 tracks can be expressed as follows:
EQU (n+1)th track: Wn+w (n-1)th track: Wn-w
 Then, respective periods of the wobble waves in the two adjoining (n+1)th
 and (n-1)th tracks relative to that of the nth track is determined.
 Because the period of the wobble waves in the nth track can be evaluated
 by dividing the time required for tracing one complete round of the nth
 track by the number of the wobble waves, the periods of the wobble waves
 in the adjoining (n+1)th and (n-1)th tracks can be computed as follows:
EQU (n+1)th track: Tc/(Wn+w) (n-1)th track: Tc/(Wn-w)
 Thus, the angular frequencies of the wobble waves in the two adjoining
 (n+1)th and (n-1)th tracks relative to that of the nth track can be
 determined as follows, using .omega.o:
EQU (n+1)th track: 2.pi.(Wn+w)/Tc =2.pi.{1+(Tp/rn)} fo=(1+.alpha.) .omega.o
EQU (n-1)th track: 2.pi. (Wn-w)/Tc =2.pi.{1+(Tp/rn)} fo=(1-.alpha.) .omega.o
 (3) Calculation of Wobble Waves:
 Now that the relative angular frequencies of the wobble waves in the two
 tracks adjoining the particular track (nth track) on both sides of the
 particular track have been calculated in the manner mentioned at item (2)
 above, mathematical expressions indicative of the individual wobble waves
 are evaluated in the following manner.
 If the wobble waves in the nth track (actual wobble waves) is expressed by
EQU Yn=cos (.omega.o t)
 ,then the wobble waves in the (n+1)th and (n-1)th tracks can be expressed
 as follows:
EQU (n+1)th track: cos {(1+.alpha.) .omega.o t+.phi.n+1}(n-1)th track: cos
 {(1-.alpha.) .omega.o t+.phi.n-1}
 Note that some relationships based on the following boundary conditions
 exist between the wobble waves of the nth track and the wobble waves of
 the (n+1) and (n-1) tracks:
 (a) The wobble waves in the nth track and (n+1)th track connect with each
 other continuously at a time point t (=Tc) of the former, i.e., at a zero
 time point t (=0) of the latter.
 (b) The wobble waves in the nth track and (n-1)th track connect with each
 other continuously at a zero time point t (=0) of the former, i.e., at a
 time point t (=Tc) of the latter.
 Thus, the following can be given:
EQU from item (a) above, cos {(1+.alpha.) .omega.o.multidot.0+.phi.n+1)=cos
 (.omega.o Tc),
 and
EQU from item (b) above, cos {(1-.alpha.) .omega.o Tc+.phi.n-1)=cos
 (.omega.o.cndot.0)
 Solving these give
EQU .phi.n+1=4.pi..sup.2 rn/.lambda., and
EQU .phi.n-1=-(1-.alpha.) 4.pi..sup.2 rn/.lambda.
 If .phi.=4.pi..sup.2 rn/.lambda., then .phi.n+1 and .phi.n-1 can be
 expressed as follows:
EQU .phi.n+1=.phi.
EQU .phi.n-1=-(1-.alpha.) .phi.
 From the foregoing, the wobble waves in the (n+1)th and (n-1)th tracks can
 be expressed as follows:
EQU (n+1)th track: cos {(1+.alpha.) .omega.o t+.phi.}(n-1)th track: cos
 {(1-.alpha.) .omega.o t-(1-.alpha.)}
 (4) Push-pull Detection Signal:
 If one detection signal output from a four-quadrant photodetector is
 represented by "A+D" and the other detection signal is represented by
 "B+C", a tracking error signal can be determined by "(A+D)-(B+C)". Now
 that the mathematical expressions representing the wobbles of the
 adjoining tracks relative to those of the nth track have been determined
 at item (3) above, the push-pull detection signal "(A+D)-(B+C)" relative
 to the nth track can be determined as follows while taking into account
 influences of the adjoining tracks:
EQU (A+D)-(B+C)=cos (.omega.o t)
EQU -K cos {(1+.alpha.) .omega.o t+.phi.}
EQU -K'cos {(1-.alpha.) .omega.o t-(1-.alpha.) .phi.}
EQU =cos (.omega.o t)-Q(t) Expression (a)
EQU Q (t)=Kcos {(1 +.alpha.) .omega.o t+.phi.}+K'cos {(1-.alpha.) .omega.o
 t-(1-.alpha.) .phi.}
 Here, K and K' are constants indicative of degree of influences exerted on
 the nth track by the adjoining (n+1)th and (n-1)th tracks. Assuming that
 the adjoining (n+1)th and (n-1)th tracks both exert the same degree of
 influences on the nth track, K and K' can be considered to be equal to
 each other (K=K'), in which case Q (t) can be modified as follows:
EQU Q (t)=K [cos {(1+.alpha.).omega.o t+.phi.}
EQU +cos {(1-.alpha.) .omega.o t-(1-.alpha.) .phi.}]
EQU =K [cos {(1+.alpha.) .phi.o t} COS (.phi.)
EQU -sin {(1+.alpha.) .omega.o t } sin (.phi.)
EQU +cos {(1-.alpha.) .omega.o t} cos {(1-.alpha.) .phi.}
EQU +sin {(1-.alpha.) .omega.o t} sin {(1-.alpha.) .phi.}
EQU =K [{cos (.omega.o t) cos (.alpha..omega.o t)
EQU -sin (.omega.o t) sin (.alpha..omega.o t)} cos (.phi.)
EQU -{sin (.omega.o t) cos (.alpha..omega.o t)
EQU +cos (.omega.o t) sin (.alpha..omega.o t)} sin (.phi.)
EQU +{cos (.omega.o t) cos (.alpha..omega.o t)
EQU +sin (.omega.o t) sin (.alpha..omega.o t)}
EQU {cos (.phi.) cos (.alpha..phi.)+sin (.phi.) sin (.alpha..phi.)}
EQU +{sin (.omega.o t) cos (.alpha..omega.o t)}
EQU -cos (.omega.o t) sin (.alpha..omega.o t)}
EQU {sin (.phi.) cos (.alpha..phi.)-cos (.phi.) sin (.alpha..phi.)}]
 Expression (b)
 Vector diagram of the push-pull detection signal based on Expression (a)
 and Expression (b) above is generally as illustrated in FIG. 2, where
 various reference characters are defined as follows:
 a: vector of the wobble signal of the nth track (which is used as a
 reference vector in the example of FIG. 2).
 b: vector of cross-talk by the wobble signal of the (n+1)th track, where
 the vector has a magnitude K and rotates in a counterclockwise direction
 at an angular frequency of .alpha..omega.o, and the phase at the zero time
 point t (=0) is .pi.+.phi..
 c: vector of cross-talk by the wobble signal of the (n-1)th track, where
 the vector has a magnitude K and rotates in a clockwise direction at an
 angular frequency of .alpha..omega.o, and the phase at the zero time point
 t (=0) is .pi.-(.phi.-2.pi.w).
 d: a composite vector of the above-mentioned vectors b and c (which
 stretches and contracts along an A axis).
 d' and d": maximum values of the composite vector d.
 e: a composite vector of the above-mentioned vectors a and d.
 e': a composite vector of the above-mentioned vectors a and d'.
 e": a composite vector of the above-mentioned vectors a and d".
 The wobble signal detected here has the composite vector e of the vectors a
 and d, and the tip of the vector e moves between e' and e" along an axis
 parallel to the A axis. Therefore, the detected wobble signal would vary,
 in both phase and amplitude, due to cross-talk between wobble signals from
 the adjoining (n+1)th and (n-1)th tracks.
 (5) Variation in the Push-pull Detection Signal "(A+D)-(B+C)" Depending on
 a Condition of w:
 At item (4) above, a general formula representative of the push-pull
 detection signal "(A+D)-(B+C)" has been determined as Expression (a) and
 Expression (b).
 Here, let's consider the push-pull detection signal "(A+D)-(B+C)" when the
 value w is an even-number multiple of 0.5, namely, w=0.5.times.2n (n is a
 natural number). When w=0.5.times.2n, .alpha..phi. can be expressed as
 .alpha..phi.=(w.lambda./2.pi.rn).multidot.(4.pi..sup.2
 rn/.lambda.)=2.pi.w=2n.pi.
 Thus, sin (.alpha..phi.) and cos (.alpha..phi.) in the third and fourth
 terms of Expression (b) become "0" and "1", respectively, namely,
 sin (.alpha..phi.)=0, and cos (.alpha..phi.)=1
 Accordingly, Expression (b) is modified as
EQU Q(t)=2Kcos (.alpha..omega.o t+.phi.) COS (.omega.o t)
 At that time, the push-pull detection signal "(A+D)-(B+C)" can be expressed
 as follows on the basis of Expression (a):
EQU (A+D)-(B+C)=cos (.omega.o t) -2Kcos (.alpha..omega.o t+.phi.) cos (.omega.o
 t) ={1-2Kcos (.alpha..omega.o t+.phi.)} cos (.omega.o t) Expression (c)
 FIG. 3 is a vector diagram of the push-pull detection signal based on
 Equation (c) above, where reference characters used have the same meanings
 as explained earlier in relation to FIG. 2. In FIG. 3, the vector d
 stretches and contracts along a real-number axis, so that the vector e of
 the wobble signal, detected as the composite vector of the vectors a and
 d, moves between e' and e" along the real-number axis. Solid lines in FIG.
 4 show a waveform of the thus-detected wobble signal, which is modulated
 only in amplitude as compared to when there is no cross-talk (dotted
 lines), but not modulated in phase at all (i.e., its zero-cross points
 have not been shifted at all). As a result, the present invention can
 provide accurate position information free of jitters and also can
 generate recording reference clock pulses with no fluctuation.
 The present invention is based on the above-discussed principles. Namely,
 the present invention provides a CLV-type recordable optical disk
 including a plurality of tracks, in which the tracks are formed in such a
 manner that 2.pi.Tp/.lambda. substantially equals an even-number multiple
 of 0.5 where Tp is a track pitch and .lambda. is a wavelength of a track
 wobble. Each of the tracks is divided into a plurality of address sections
 each including a first predetermined number of wobble waves, and each of
 the address sections is divided into a plurality of small-size sections
 each including a second predetermined number of the wobble waves.
 Information recording area having a length smaller than a half of the
 length of the small-size section is set, for each of the tracks, in each
 particular one of the small-size sections of the track located where there
 occurs no overlap in the information recording area, in a radial direction
 of the optical disk, between the track and other tracks adjoining the
 track. One piece of address information for each of the address sections
 is divided into a plurality of address information elements that are
 allotted to respective ones of the information recording areas within the
 address section. Further, the track wobble at a predetermined position
 within each of the information recording areas having the address
 information elements allotted thereto is recorded with
 180.degree.-two-phase modulation performed thereon in accordance with the
 allotted address information, and the track wobbles in other areas than
 the information recording areas are recorded in non-modulated form.
 The present invention further provides a CLV-type recordable optical disk
 including a plurality of tracks, in which the tracks are formed in such a
 manner that 2.pi.Tp/.lambda. substantially equals an even-number multiple
 of 0.5 where Tp is a track pitch and .lambda. is a wavelength of a track
 wobble, and each of the tracks is divided into a plurality of address
 sections each including a first predetermined number of wobble waves, each
 of the address sections being divided into a plurality of medium-size
 sections each including a second predetermined number of the wobble waves,
 each of the medium-size sections being divided into a plurality of
 small-size sections each including a third predetermined number of the
 wobble waves. Information recording area having a length smaller than a
 half of the length of the small-size section is set, for each of the
 tracks, in each particular one of the small-size sections located where
 there occurs no overlap in the information recording area, in a radial
 direction of the optical disk, between the track and other tracks
 adjoining the track, and a leading-information-recording-area
 syncronization signal is allotted to a leading one of the information
 recording areas in each of the medium-size sections, to identify the
 leading information recording area in the medium-size section. One piece
 of address information for each of the address sections is divided into a
 plurality of address information elements, which are allotted to the
 respective information recording areas within the address section, other
 than the leading information recording area, where the
 leading-information-recording-area syncronization signal is not allotted
 (i.e., non-leading information recording areas). The track wobble at a
 predetermined position in the leading information recording area of each
 of the medium-size sections where the leading-information-recording-area
 syncronization signal is allotted is recorded with 180.degree.-two-phase
 modulation performed thereon in accordance with the allotted
 leading-information-recording-area syncronization signal, the track wobble
 at a predetermined position in each of the other information recording
 areas where the address information elements are allotted is recorded with
 180.degree.-two-phase modulation performed thereon in accordance with the
 allotted address information element, and the track wobbles in remaining
 areas are recorded in non-modulated form.
 According to the recordable optical disk of the present invention, an
 unwanted phase variation of the detected wobble signal from a given track
 can be minimized, although the detected wobble signal of the given track
 may vary in amplitude due to cross-talk by the wobble signals from
 adjoining tracks located on both sides of the given track. Therefore, when
 reference clock pulses are to be generated on the basis of the detected
 wobble signal, they can be generated in a stabilized condition without
 involving any significant phase variation. Further, the present invention
 can detect the address information recorded in the track wobble without
 the phase variation, so that it achieves accurate data-write linking and
 improved quality of recording signals.
 In a preferred implementation of the present invention, the information
 recording area is set primarily in every other small-size section of each
 of the tracks, and in each portion of the optical disk where there would
 occur overlap in the information recording area, in the radial direction
 of the optical disk, between the currently-traced track and other tracks
 adjoining the track, the information recording areas of the tracks are
 displaced in position from each other by the length of one small-size
 section to thereby avoid the overlap.
 In another preferred implementation, the information recording area is set
 primarily in every other small-size section of each of the tracks, and in
 each portion of the optical disk where there would occur overlap in the
 information recording area, in the radial direction of the optical disk,
 between the track and other tracks adjoining the track, the information
 recording areas of the tracks are displaced in position from each other by
 the length of one small-size section to thereby avoid the overlap.
 Further, the information recording area is set only in each of
 even-numbered small-size sections or in each of odd-numbered small-size
 sections within each of the medium-size sections, and an
 even-number/odd-number identifying signal is allotted to the leading
 information recording area in each of the medium-size sections in order to
 indicate whether the information recording area is set only in each of the
 even-numbered small-size sections or in each of the odd-numbered
 small-size sections within each of the medium-size sections. In this case,
 the track wobble at a predetermined position within each of the
 information recording areas is recorded with 180.degree.-two-phase
 modulation performed thereon in accordance with the allotted
 even-number/odd-number identifying signal.
 The information recording area may be set, for example, in the start
 position of the small-size section, and an information recording area
 synchronization signal produced by recording the track wobble successively
 for a predetermined period in non-modulated and 180.degree.-inverted form
 may be recorded at the head of the information recording area.
 Further, the present invention may be arranged in such a manner that each
 of the small-size sections corresponds to a sync frame in a DVD standard
 and a total number of the wobble waves within the sync frame is set to 42.
 In this case, the sync frame and the track wobble may be synchronous in
 phase with each other so that the track wobble is set to a 0.degree. phase
 at a start point of the sync frame.
 According to another aspect of the present invention, there is provided an
 optical disk recording apparatus which is directed to recording desired
 information onto any one of the improved CLV-type recordable optical disk
 as discussed above. The optical disk recording apparatus of the present
 invention comprises: a 180.degree.-two-phase demodulation circuit that
 performs 180.degree.-two-phase demodulation on a wobble signal detected
 from the optical disk to thereby demodulate information recorded in the
 information recording areas; an address information demodulation circuit
 that, on the basis of the information demodulated by the
 180.degree.-two-phase demodulation circuit, demodulates the address
 information recorded dispersedly in the small-size sections of each of the
 address sections; and a recording position control circuit that performs
 recording position control on the basis of the address information
 demodulated by the address information demodulation circuit.
 According to still another aspect of the present invention, there is
 provided a CLV-type recordable optical disk including a plurality of
 tracks, where the tracks are formed in such a manner that 2.pi.Tp/.lambda.
 substantially equals an even-number multiple of 0.5 where Tp is a track
 pitch and .lambda. is a wavelength of a track wobble, and each of the
 tracks is divided into a plurality of address sections, a predetermined
 number of wobble waves in the track constituting an address section, the
 address section being divided into a plurality of small-size sections. One
 piece of address information to be recorded for each of the address
 sections of the track is divided into a plurality of address information
 elements that are allotted to respective ones of the small-size sections
 within the address section located in a position where there occurs no
 overlap in the information recording area, in a radial direction of the
 optical disk, between the track and other tracks adjoining the particular
 track. Further, the track wobble in each of the small-size sections to
 which the address information element is allotted is recorded with
 180.degree.-two-phase modulation performed thereon in accordance with the
 allotted address information element and the track wobble in the other
 small-size sections are recorded in non-modulated form.
 In the recordable optical disk according to the other aspect of the present
 invention, the information recording areas where the address information
 elements are allotted may be each set to any other length than half the
 length of the small-size section; for example, such an information
 recording area may be set over the entire length of the small-size
 section. Further, the information recording area may be set in every three
 (or more) small-size sections. In this case too, in each portion of the
 optical disk where there would occur overlap in the information recording
 area, in the radial direction of the optical disk, between the
 currently-traced track and other tracks adjoining the track, the
 information recording areas of the tracks may be displaced in position
 from each other by the length of one small-size section to thereby avoid
 the overlap. With such arrangements, an unwanted phase variation of the
 detected wobble signal from a given track can be minimized, although the
 detected wobble signal of the given track may vary in amplitude due to
 cross-talk by the wobble signals from adjoining tracks located on both
 sides of the given track. Therefore, when reference clock pulses are to be
 generated on the basis of the detected wobble signal, they can be
 generated in a stabilized condition without involving any significant
 phase variation. Further, the present invention can detect the address
 information recorded in the track wobble without the phase variation, so
 that it achieves accurate data-write linking and improved quality of
 recording signals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIGS. 1(a) and 1(b) are views showing an optical disk 10 in accordance with
 a preferred embodiment of the present invention, which is a recordable
 (write-once or rewritable) optical disk of the CLV (Constant Linear
 Velocity) type. As shown in an enlarged scale in part (b) of FIG. 1(b),
 the optical disk 10 has a plurality of tracks in the form of grooves 11
 formed in its recording surface, which wobble at a predetermined frequency
 (e.g., 140 kHz); the pitch Tp between every adjoining tracks is set to be
 constant. Further, a wavelength .lambda. of the track wobbles and the
 track pitch Tp are set to the following relationship:
EQU 2.pi.Tp/.lambda.=(2n+2)/2 (n=0, 1, 2, . . . )
 Namely, the wavelength .lambda. of the track wobbles and the track pitch Tp
 in the embodiment are set such that 2.pi.Tp/.lambda. becomes an even
 number multiple of 0.5. In each of the track wobbles, there is recorded
 wobble recording information that is obtained by modulating the wobble in
 accordance with a 180.degree.-two-phase modulation scheme and includes
 address information indicative of absolute positions on the optical disk
 10.
 The following paragraphs describe an exemplary format in which the wobble
 recording information is recorded in the track wobble. As shown in FIG.
 5A, each of the tracks (grooves 11) of the optical disks 10 is divided
 into a plurality of ECC (Error-Correction Code) blocks. Each of the ECC
 blocks is a minimum unit with which is performed information recording
 based on pit formation. In reproduction, error correction can be made by
 reading out the wobble recording information on a block-by-block basis.
 Each of the ECC blocks can also be set as a minimum unit of address
 information (ADIP: Address In Pre-groove) to be recorded in the track
 wobble; that is, each of the ECC blocks can be set as an address section.
 As shown in FIG. 5B, each of the ECC blocks is made up of a predetermined
 number of (16 in the illustrated example) sectors (medium-size sections).
 As shown in FIG. 5C, each of the sectors is made up of a predetermined
 number of (26 in the illustrated example) sync frames (small-size
 sections). In each of the sectors, information recording areas are set in
 the even-numbered sync frames (0.sup.th, 2.sup.nd, 4.sup.th, . . . ,
 24.sup.th sync frames, namely, sync frames in odd-numbered places as
 counted from the start point of the sector) or set in the odd-numbered
 sync frames (1.sup.st, 3.sup.rd, 5.sup.th, . . . , 25.sup.th sync frames,
 i.e., sync frames in even-numbered places as counted from the start point
 of the sector). Each piece of the address information is divided into a
 plurality of address information elements and recorded dispersedly into
 the information recording areas of the sync frames across the plurality of
 sectors.
 FIG. 5D shows an exemplary organization of the sync frame, where the
 information recording area is set as a portion of a predetermined length
 extending from the beginning of the sync frame to a position slightly
 displaced off the middle of the sync frame toward the beginning. In the
 information recording area, there are recorded the address information
 elements and other information, as wobble recording information, obtained
 by modulating the wobble with the 180.degree.-two-phase modulation scheme
 according to the information. Further, in another area than the
 information recording area of the sync frame (or in an entire area of the
 sync frames having no such information recording area), the wobble is
 recorded without modulation, i.e., in non-modulated form. Note that
 predetermined synchronization data is imparted to the start point of each
 of the sync frames to identify the sync frame start point while other
 synchronization data is imparted to the start point of each of the sectors
 to identify the sector start point. Further, each of the ECC blocks can be
 identified by a kind of address information called "ID" information
 provided in each of the sectors constituting that ECC block.
 In the case where the wobble is recorded with 180.degree.-two-phase
 modulation performed thereon according to the wobble recording
 information, the relationship of "2.pi.Tp/.lambda." would be lost in a
 region where one of two particular tracks n-1 and n+1 immediately
 preceding and following a currently-traced track n is inverted while the
 other is non-inverted. In such a region, detected wobble signals would be
 modulated in phase by the wobbles of the two tracks n-1 and n+1 adjoining
 the current track n. To avoid the undesired phase modulation, it is only
 necessary to prevent the information recording areas from overlapping
 between the adjoining tracks in the radial direction of the optical disk.
 Thus, in the preferred embodiment, each of the information recording areas
 is set to a length smaller than half the length of the sync frame, and
 such information recording areas are provided only in the even-numbered
 sync frames (namely, one information recording area is established in
 every other sync frame), as an essential feature of the present invention.
 Additionally, the preferred embodiment is arranged in such a manner that
 in each sector whose information recording area overlaps, in the disk's
 radial direction, at least partly that of an inner adjoining track, the
 information recording area is displaced rearward so as to be set in the
 following odd-numbered sync frame.
 In FIG. 6, there is shown an exemplary manner in which the information
 recording areas are set in a plurality of adjoining tracks on the optical
 disk 10; illustration of the waves of the wobble is omitted for simplicity
 and each of the information recording areas is shown by hatching. Let's
 also assume that there are no boundaries between the sectors in the
 illustrated range. The information recording areas of a given track m do
 not overlap those of an adjoining track (m-1: not shown) located inwardly
 the track m, and are set in its even-numbered sync frames. Similarly, the
 information recording areas of a next track m+1 do not overlap those of
 the track m adjoining and located inwardly of the track m+1, and are set
 in its even-numbered sync frames. In each of the even-numbered sync frames
 of another track m+2 where there would occur an overlap between the
 information recording areas of the tracks m+2 and the inner adjoining
 track m+1, the information recording area of the track m+2 is shifted
 rearwardly, by a distance corresponding to the length of one sync frame,
 to be set in the odd-numbered sync frame immediately following that
 even-numbered sync frame. In another track m+3, there would occur no
 overlap between the information recording areas of the tracks m+3 and the
 inner adjoining track m+2, so that the information recording area is set
 in each of its even-numbered sync frames.
 FIGS. 7(a)-7(d) are diagrams, each showing an exemplary manner in which the
 track wobble in the information recording area is recorded on the optical
 disk in accordance with the DVD standard, where
 track pitch Tp=0.741 .mu.m
 one sync frame=1488 channel bits
 one channel bit length=0.133 .mu.m
 Circumferential length of one round of each track can be represented by
 "2.pi.Tp/.lambda.", and if a wavelength .lambda. of the track wobbles is
 chosen such that it equals the circumferential length of one track round,
 then
 2.pi.Tp/.lambda.=1
 , which satisfies the condition that "2.pi.Tp/.lambda." be an even number
 multiple of 0.5. Thus, the wobble signal to be reproduced becomes quite
 unsusceptible to phase modulation by cross-talk between adjoining tracks,
 at which time .lambda.=4.649 .mu.m.
 On the other hand, one sync frame length is
EQU 1488.times.0.133=197.904 .mu.m
 Therefore, when .lambda.=4.649 .mu.m, the number of the wobble waves within
 one sync frame is
 197.904/4.649=42.569 waves
 However, because the number of the wobble waves within one sync frame must
 be an integer and have a submultiple, "43" is selected as an integer close
 to 42.569. If the number of the wobble waves within one sync frame is set
 to "42", then the wavelength .lambda. of the track wobbles becomes 4.7121
 .mu.m because 197.904/.lambda.=42. At that time,
 2.pi.Tp/.lambda.=0.987
 , which substantially satisfies "2.pi.Tp/.lambda." be an even number
 multiple of 0.5, so that the reproduced wobble signal can almost be
 prevented from being phase-modulated by cross-talk between adjoining
 tracks.
 In the illustrated example of FIGS. 7(a)-7(d), each of the sync frame
 contains 42 wobble waves. The track wobble is synchronous in phase with
 the sync frame and has a 0.degree. phase at the start point of the sync
 frame. Divisor of the wobble waves within the sync frame is set as a
 minimum wave inversion period, so that the wobble phase at each wave
 inversion point is 0.degree.. In the example of FIGS. 7(a)-7(d), the
 minimum wave inversion period is set to equal three waves and represented
 by "w-bit"; that is,
 one sync frame =42 wobble waves =14 w-bits
 The information recording area is provided over a range of 6 w-bits from
 the start point of the sync frame to a point before the middle of the sync
 frame; namely, the information recording area has a length smaller than
 half the length of the sync frame. In the remaining 8 w-bits, the track
 wobble is recorded in non-modulated form.
 Specifically, FIGS. 7(a) and 7(b) show the track wobble recorded in the
 leading or first information recording area of one of the sectors; more
 specifically, FIG. 7(a) shows a case where the information recording area
 is in an even-numbered sync frame while FIG. 7(b) shows a case where the
 information recording area is in an odd-numbered sync frame. Further,
 FIGS. 7(c) and 7(d) in FIG. 7 show the track wobble recorded in the second
 or subsequent information recording area of the sector, which includes
 address information elements.
 The information recording area is made up of the 0.sup.th to 5.sup.th
 w-bits, and in the 0.sup.th to 3.sup.rd w-bits out of these five w-bits,
 there is recorded an information recording area synchronization signal
 that is composed of a code "0001". The reason why the leading 0.sup.th to
 2.sup.nd w-bits are "000" (i.e., non-modulated) is that if any information
 recording area An-1 exists in an adjoining track n-1 at a position
 immediately before the start point of an information recording area An of
 a currently-traced track n, jitters of a wobble PLL (Phase-Locked Loop),
 caused by cross-talk by the adjoining track n-1 during the tracing of the
 position immediately before the start point of the information recording
 area An, would remain due to a delayed response even after the information
 recording area An starts. Namely, with a view to eliminating the jitters
 of the wobble PLL, the non-modulated region is provided across the leading
 0.sup.th to 2.sup.nd w-bits of the information recording area.
 Further, at the fourth w-bit of the information recording area in FIGS.
 7(a)-7(d), a code "1" is recorded as a leading-information-recording-area
 syncronization signal to identify the leading information recording area
 within the sector (medium-size section); however, a code "0" is recorded
 as a syncronization signal to identify information recording areas other
 than the leading one (i.e., non-leading information recording areas)
 within the sector.
 At the fifth w-bit of the information recording area in FIGS. 7(a)-7(d),
 there is recorded information that differs depending on the code of the
 fourth w-bit. Namely, when the code of the fourth w-bit is "1" that is
 indicative of the leading information recording area, information
 (even-number/odd-number identifying information) is recorded at the fifth
 w-bit which indicates whether the information recording areas are each set
 in an odd-numbered sync frame or in an even-numbered sync frame of the
 sector. More specifically, if the code recording at the fifth w-bit is
 "1", it means that all the information recording areas of the sector are
 set in the even-numbered sync frames, but if the code recording at the
 fifth w-bit is "0", it means that all the information recording areas of
 the sector are set in the odd-numbered sync frames.
 When the code of the fourth w-bit is "0" that is indicative of one of the
 non-leading information recording areas, on the other hand, there is
 recorded, at the fifth w-bit, data of a bit of the address information at
 the corresponding position as an address information element. Namely, a
 code "1" recorded at the fifth w-bit indicates that the data value of the
 address information element is "1" while a code "0" recorded at the fifth
 w-bit indicates that the data value of the address information element is
 "0". Particular bit in a bit stream constituting the address information,
 which corresponds to the address information element, can be identified by
 ascertaining from which one of the sectors as counted from the start point
 of the ECC block and which one of the sync frames as counted from the
 start point of that sector the address information element has been read
 out.
 FIG. 9 is a block diagram of wobble signal generation circuitry that is
 employed in a master recording apparatus for manufacturing the optical
 disk 10 of FIG. 1A and is constructed to record wobbling tracks as shown
 in FIGS. 7(a)-7(d). Further, FIGS. 10(a)-10(d) show waveforms output from
 various components of FIG. 9. In FIG. 9, a reference clock generator
 circuit 12 includes generates reference clock pulses using a quartz
 oscillator. Each of the reference clock pulses generated by the clock
 generator circuit 12 is given to a frequency divider 14, so to generate a
 wobble signal (carrier wave signal) at a predetermined frequency (e.g.,
 140 kHz) as illustrated in FIG. 10(a). Each of the reference clock pulses
 is also given to another frequency divider 16, so as to generate a wobble
 clock pulse at a frequency three times as low as the wobble signal as
 illustrated in FIG. 10(b). Wobble recording information generator circuit
 18 generates wobble recording information in synchronism with the wobble
 clock pulse as illustrated in FIG. 10(c). Phase modulation circuit 20
 performs 180.degree.-two-phase modulation on the wobble signal in
 accordance with the wobble recording information, to thereby generate a
 180.degree.-two-phase-modulated wobble signal as illustrated in FIG.
 10(d); that is, this phase modulation circuit 20 inverts the wobble signal
 when the wobble recording information is of the value "1", but does not
 invert the wobble signal when the wobble recording information is of the
 value "0". Thus, in the master disk is recorded a track wobbling in
 accordance with the waveform of the 180.degree.-two-phase-modulated wobble
 signal.
 FIG. 11 is a block diagram showing an exemplary setup of an optical disk
 recording apparatus for recording desired information onto the optical
 disk 10 of FIG. 1(a) where the grooves are formed in the above-mentioned
 manner. Laser diode 22 emits and irradiates a recording/reproducing laser
 light beam onto the recording surface of the optical disk 10 for recording
 or reproduction of desired information to or from the disk 10. At that
 time, a reflection of the laser light beam from the optical disk 10 is
 received by a four-quadrant or four-part photodetector 24, which produces
 four light reception signals via the respective quadrants. The light
 reception signals from one pair of the quadrants A and D adjoining each
 other along a longitudinal direction of the track are added together, and
 similarly the light reception signals from another pair of the quadrants B
 and C adjoining each other along the direction of the track are added
 together, and a subtracter 26 performs subtraction the resultant sums of
 the quadrant pairs, i.e., "(A+D)-(B+C)", so that a push-pull signal as
 shown in FIG. 4 is provided. Tracking servo control is performed on the
 basis of the push-pull signal.
 Further, the push-pull signal is passed through a band-pass filter 28 to
 extract a wobble signal component. The thus-extracted wobble signal
 component is sent to a 180.degree.-two-phase demodulation circuit 44
 constituting a wobble PLL. Namely, a phase comparator 48 in the
 180.degree.-two-phase demodulation circuit 44 compares the phases of the
 extracted wobble signal and an output signal from a VCO
 (Voltage-Controlled Oscillator) 46, and generates a signal corresponding
 to the phase difference between the two signals. The output signal from
 the phase comparator 48, indicative of the phase difference between the
 extracted wobble signal and the VCO output signal, is averaged via a loop
 filter 47, to control the frequency and phase of the VCO 46. Because most
 of the wobble signal is recorded in non-inverted form, the phase of the
 output signal from the VCO 46 is synchronized with that of the
 non-inverted wobble signal. Thus, the phase comparator 48 produces phase
 comparison outputs that increase in level in response to a region where
 the wobble signal is recorded in phase-inverted form (i.e., in response to
 a region where the code of the wobble recording information is "1" as
 illustrated in FIG. 10(c). Therefore, a demodulated signal of the wobble
 recording information can be provided by passing the output signal from
 the phase comparator 48 through a low-pass filter 50 to eliminate ripples
 corresponding to the wobble frequency.
 ADIP (Address In-Pregroove) decoder (address information demodulator)
 circuit 52 demodulates the wobble recording information by sampling the
 demodulated signal of the wobble recording information in accordance with
 the output signals from the VCO 46 (wobble clock pulses) and collects the
 address information elements dispersedly recorded within the ECC block, to
 thereby acquire the address information indicative of the position of the
 ECC block.
 Wobble clock pulse output from the VCO 46 is passed to a frequency divider
 53 for frequency division by a factor of seven and then multiplied by 248
 via a frequency multiplier 54, so as to generate a recording clock of a
 channel bit period (i.e., one sync frame=42 wobble waves=1488 channel
 bits).
 Further, a link position control circuit (recording position control
 circuit) 64 detects a data-write link position on the basis of the address
 information output from the ADIP decoder circuit 52 and generates a start
 signal at a predetermined link position (at the start position of the ECC
 block), so that a data-write linking can be effected in response to the
 start signal. Namely, in response to the start signal, a recording data
 output circuit 56 outputs recording data, and an EFM modulation circuit 58
 performs EFM (Eight-to-Fourteen Modulation) operations on the recording
 data in synchronism with recording reference clock pulses. Further, a
 laser modulation circuit 60 performs modulations to adjust the length,
 timing and level of a laser drive signal in accordance with time lengths
 of the level "1" and "0" regions of the laser drive signal. Then, a driver
 62 drives the laser diode 22 in accordance with the thus-modulated laser
 drive signal so that desired information can be recorded onto the optical
 disk 10.
 Rotation of a spindle motor 42 is controlled on the basis of the wobble
 clock pulses output from the VCO 46. More specifically, each of the wobble
 clock pulses from the VCO 46 is frequency-divided via a frequency divider
 32, while each of the reference clock pulses generated by the quartz
 oscillator is frequency-divided via another frequency divider 34. Phase
 comparator 36 makes a comparison between the phases of the two clock
 pulses from the frequency dividers 32 and 34, and the output from the
 comparator 36 is smoothed via a low-pass filter 38, in accordance with
 which the spindle motor 42 is controlled, via a motor driver 40, to rotate
 at a constant linear velocity.
 The preferred embodiment has been described above as allotting one address
 to each ECC block and one-bit address information element to each
 information recording area. The following paragraphs describe arrangements
 to allot individual addresses to all areas of the optical disk at the
 above-mentioned rate of allotment.
 As seen in FIGS. 5(a)-5(d), each of the ECC blocks comprises 16 sectors,
 and each of the sectors comprises 26 sync frames. The information
 recording areas are set in half of the 26 sync frames, i.e., 13 sync
 frames, respectively, and the address information elements can be allotted
 to twelve of these 13 sync frames, one-bit address information element per
 sync frame; note that the value "1" at the fifth w-bit of the
 syncronization signal indicative of the sector's leading information
 recording area FIG. 7(a) is allotted to the remaining one information
 recording area. Therefore, a total of 192 (16.times.12) bits of the
 address information elements can be allotted to each of the ECC blocks. In
 the case of the DVD (Digital Versatile Disk), each of the ECC block can be
 identified by an address of only 20 bits, even though the DVD has two
 recording layers in each of the two surfaces (i.e., four recording layers
 in total); each of the ECC block has a storage capacity of 32 Kbytes (2
 Kbytes/sector.times.16 sectors). Namely, only 20 bits out of the reserved
 192 bits are sufficient to constitute the address information, which means
 that the 192 bits are quite enough even when parity check bits are taken
 into account.
 Note that various form of address information allotment other than the
 above-mentioned is also possible in the present invention. For example,
 the address information may be allotted to every half of the ECC block. In
 this case, the number of the addresses doubles if the above-mentioned
 conditions are to be satisfied, and the necessary number of bits for the
 address information becomes 21. On the other hand, the total number of the
 address information elements that can be allotted to each half of the ECC
 block decreases in half to 96 bits. However, because only 21 bits out of
 the reserved 96 bits are sufficient to constitute the address information,
 which means that the 96 bits are still quite enough even when parity check
 bits are taken into account. Furthermore, the address information may be
 allotted every quarter of the ECC block. In this case, if the
 above-mentioned conditions are to be satisfied, the number of the
 addresses increases four times as compared to the case where one address
 is allotted per ECC block, and the necessary number of bits for the
 address information becomes 22. On the other hand, the total number of the
 address information elements that can be allotted to each quarter of the
 ECC block decreases in quarter to 48 bits. However, because only 22 bits
 out of the reserved 48 bits are sufficient to constitute the address
 information, which means that the 48 bits are still enough even when
 parity check bits are taken into account.
 Further, whereas the preferred embodiment has been described above as
 allotting the one-bit address information element to each of the
 information recording areas, the present invention is not so limited; for
 example, address information element of a plurality of bits may be
 allotted to each of the information recording areas.
 Described below is a recordable optical disk in accordance with another
 embodiment of the present invention. In this recordable optical disk, a
 plurality of tracks are formed such that "2.pi.Tp/.lambda." substantially
 equals an even-number multiple of 0.5, where Tp represents the track pitch
 and .lambda. represents the wavelength of the track wobbles. One address
 section is defined by each of the ECC blocks, and each piece of address
 information to be recorded in one of the address sections is divided into
 a plurality of address information elements. Each of the address
 information elements is set to or allotted to a predetermined position in
 a sync frame within the corresponding address section where there occurs
 no overlap in the information recording area, in the radial direction of
 the optical disk, with an adjoining track. The wobble in each of the sync
 frames where the address information element is allotted is recorded with
 180.degree.-two-phase modulation performed thereon in accordance with the
 address information element, with the wobbles in the other sync frames
 being recorded in non-modulated form. FIG. 12 is explanatory of an
 exemplary manner in which the information recorded areas are set in a
 plurality of the tracks in a given portion of the optical disk 10 to which
 the present invention is applied. In FIG. 12, illustration of the wobble
 waves is omitted for simplicity and each of the information recording
 areas is shown by hatching; let it also be assumed that there are no
 boundaries between the sectors in the illustrated range. In the
 illustrated example of FIG. 12, the entire length of each sync frame is
 provided as the information recording area, and wobble recording
 information is in the same format as shown in FIGS. 5(a)-5(d), except that
 the information recording area is set throughout the length of the sync
 frame. Further, the illustrated example of FIG. 12 is characterized by
 providing the information recording area every three sync frames, so that
 in each region of the optical disk where there would occur overlap in the
 information recording area, in the radial direction of the disk, between
 adjoining tracks, the information recording areas of these adjoining
 tracks are displaced in position from each other by the length of one sync
 frame to thereby avoid such overlap. Note that the information recording
 area may be set within a range smaller than the length of the sync frame.