Recording and retrieving method on rewritable optical recording medium
View Patent ↗In a rewritable compact disc having a wobble groove on a substrate, crystal and amorphous states of a phase-change recording layer are an unrecorded/erased state and a recorded state, respectively. When the recording layer is exposed to recording light, amorphous marks assuming the recorded state are formed. At any of 2-, 4- and 8-times velocities with respect to a reference velocity (1-times velocity) whose linear velocity is 1.2–1.4 m/s, modulation m 11 of a recorded signal when the recording light of approximately 780 nm in wavelength irradiates the recording layer via an optical system with NA=0.5 or 0.55 is 60–80%. A topmost level R top of reflectivity of the eye pattern of the recorded signal during retrieving at the 1-times velocity is 15–25%, and a jitter of the individual length of marks and inter-mark spaces during retrieving at 1-times velocity is 35 ns or less. Recording at 8-times or higher velocities is thereby realized without any risk of impairing the read-compatibility with the conventional CD-RW specifications at least at 4-times velocity.
1. A method of recording EFM-modulated information in terms of different mark lengths on a rewritable disc-shaped optical recording medium having a phase-change recording layer by CLV (constant linear velocity) operation, an individual recorded mark has a time length nT (T is the data reference clock period, and n is an integer within a range of from 3 to 11), and for recorded marks, the time length (n−j)T is divided into α 1 T, β 1 T, α 2 T, β 2 T, . . . , α m T, β m T (where m=n−1 or m=n−2) in this sequence so as to satisfy Σ i (α i +β i )=n−j (j is a real number within a range of 0.0≦j≦2.0), said method comprising the steps of:
irradiating inter-mark portions with a recording light of erasure power Pe, which is able to crystallize an amorphous-state portion;
irradiating the recording layer with a recording light of recording power Pw (Pw>Pe), which is able to melt the recording layer within the time length α i T (1≦i≦m); and
irradiating the recording layer with a recording light of bias power Pb (0<Pb≦0.5Pe) within the time length β i T (1≦i≦m) to overwrite; and wherein
when a linear velocity within a range of 1.2 m/s to 1.4 m/s is the reference velocity (1-times velocity) and 231 nsec (ns) is a reference clock period,
(1) for the 4-times velocity, α 1 =from 0.3 to 1.5,
α i =from 0.2 to 0.7 (2≦i≦m), α i +β i-1 =from 1 to 1.5 (3≦i≦m),
(2) for the 1- or the 2-times velocity, α 1 =from 0.05 to 1.0, α i =from 0.05 to 0.5 (2≦i≦m), α i +β i-1 =from 1 to 1.5 (3≦i≦m) and
(3) for any of 6-, 8-, 10- and 12-times velocities,
α 1 =from 0.3 to 2, α i =from 0.3 to 1 (2≦i≦m),
α i +β i-1 =from 1 to 1.5 (3≦i≦m),
wherein for any of the described linear velocity in use,
each of α 1 T, α i T (wherein i=2 to m), and α i +β i-1 is constant (where i is an integer within a range of from 3 to m);
wherein for any of the described linear velocity in use,
β m =from 0 to 1.5, and
β m is constant for every linear velocity, or decreases as the linear velocity increases.
2. A recording method according to claim 1 ,
α 1 =approximately 1, α i =from 0.3 to 0.6 (where i is an integer within a range of from 2 to m), and
α i +β i-1 is constant (where i is an integer within a range of from 3 to m), and
α i is monotonically reduced for the lower linear velocity (where i is an integer within a range of from 2 to m).
3. A recording method according to claim 2 , wherein for any of the described linear velocity in use,
m is only one of n−1 or n−2, and
α i +β i-1 =approximately 1 for every i (where i is an integer within a range of from 2 to m).
4. A recording method according to claim 1 , wherein α i /α 1 =from 0.3 to 0.7 (where i is an integer within a range of from 2 to m).
5. A recording method according to claim 1 , wherein for any of the described linear velocity in use, each of α i T (1≦i≦m) and β i T (1≦i≦m−1) is 10 ns or more.
6. A method of recording various mark and inter-mark lengths in terms of EFM-modulated information on a rewritable disc-shaped optical recording medium having a predetermined recording area by CAV (constant angular velocity) operation, in which the recording medium is rotated at a constant angular velocity, when a linear velocity within a range of from 1.2 m/s to 1.4 m/s is a reference velocity (1-times velocity), the disc-shaped optical recording medium is rotated in a way that a linear velocity at an outermost periphery of the recording area is as high as 10 times of the reference velocity, if a time length of an individual recorded mark is nT (T is a data reference clock period varying according to its radial position in a way that a product VT (V is a linear velocity in the radial position is constant, and n is an integer within a range of from 3 to 11), and for recorded marks, the time length (n−j)T is divided into α 1 T, β 1 T, α 2 T, β 2 T, . . . , α m T, β m T (where m=n−1, α 1 /α 1 =from 0.3 to 0.7 (i is an integer within a range of from 2 to m), α i +β i-1 =approximately 1 (3≦i≦m) in this sequence so as to satisfy Σ i (α i +β i )=n−j (j is a real number within a range of 0.0≦j≦2.0), said method comprising the steps of:
irradiating inter-mark portions with a recording light of erasure power Pe, which is able to crystallize an amorphous-state portion;
irradiating the recording layer within the time length α i T (1≦i≦m), with a recording light, whose record power Pw (Pw>Pe) is enough to melt said recording layer; and
irradiating the recording layer within the time length β i T (1≦i≦m), with a recording light of bias power Pb (0<Pb≦0.5Pe), and wherein
each of α i T (i=from 2 to m) and α i +β i-1 (i=from 3 to m) is constant for any radial position;
wherein said recording area of said rewritable disc-shaped optical recording medium is divided into a plurality of virtual zones for every radial position, β m =from 0 to 1.5, and β m is monotonically increased for the radially inner zone.
7. The method of recording according to claim 6 , wherein said rewritable disc-shaped optical recording medium is a rewritable compact disc (CD-RW) in which at least a radius ranging from 23 to 58 mm is defined as said recording area.
8. The method of recording according to claim 6 , wherein each of α i T (1≦i≦≦m) and β i T (1≦i≦m) is 10 ns or more for any radial position.
9. The method of recording according to claim 8 , wherein for any linear velocity in use, a value of each of Pb, Pw, and Pe/Pw is substantially constant.
10. The method of recording according to claim 6 , wherein
said rewritable disc-shaped optical recording medium has on a substrate a wobble groove having a wobble signal whose frequency is modulated by ±1 kHz according to ATIP (absolute time in pre-groove) information with a carrier frequency of approximately 22.05 kHz in terms of the frequency at the 1-times velocity,
said carrier frequency is detected while said rewritable disc-shaped optical recording medium is rotated at a constant angular velocity, and a data reference clock according to a disc radius is obtained by multiplying the detected frequency with 196, and
an ATIP (absolute time in pre-groove) signal, which is the ATIP information, is detected, and a data reference clock, which is in synchronism with a synchronization pattern in the detected ATIP signal and a disc rotation, is obtained.
11. The method of recording according claim 6 , wherein
said rewritable disc-shaped optical recording medium has on a substrate a wobble groove that has a wobble signal, whose frequency is modulated by ±1 kHz according to ATIP information with a carrier frequency of approximately 22.05 kHz in terms of the frequency at the 1-times velocity, and also clock marks arranged along the groove at a repeating frequency in a range of from 2 to 8 times of 22.05 kHz, and
the individual clock mark is detected while said rewritable disc-shaped optical recording medium is rotated at a constant angular velocity, and a data reference clock is obtained by multiplying said repeating frequency of the clock mark with a predetermined multiplier.
12. The method of recording according to claim 6 , wherein
said wobble groove has a wobble signal, whose carrier frequency is constant when the linear velocity is constant, and also has address information and a synchronization pattern in terms of whether the wobble is modulated in phase or whether a specified position is devoid of wobble, and
said carrier frequency is detected while said rewritable disc-shaped optical recording medium is rotated at a constant angular velocity, and a data reference clock is obtained by multiplying the detected frequency with a predetermined multiplier.
13. The method of recording according to claim 6 , wherein
said rewritable disc-shaped optical recording medium has absolute time information in terms of a sub-code Q channel signal recorded previously in the entire recording area as an EFM-modulated signal, and
said EFM-modulated signal is detected while said rewritable disc-shaped optical recording medium is rotated at a constant angular velocity, and a data reference clock and address information are obtained from said EFM modulated signal.
14. The method of recording according to claim 6 , wherein
said rewritable disc-shaped optical recording medium has a block data structure according to CD-ROM specifications recorded previously in the entire recording area as EFM-modulated signal, and
said EFM-modulated signal is detected while said rewritable disc-shaped optical recording medium is rotated at a constant angular velocity, and a data reference clock and address information are obtained from the detected EFM-modulated signal.
15. The method of recording according to claim 6 , wherein recording and retrieving to and from an information area are made at the same angular velocity.
16. The method of recording according to claim 6 , wherein α 1 T=T top +α 1 ′T, each of T top and α 1 ′ being constant irrespective of the linear velocity.