Phase-change optical recording method using pulse width modulation technique

• US 5,761,179 A
• Filed: 04/12/1996
• Issued: 06/02/1998
• Est. Priority Date: 04/14/1995
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Harigaya, Makoto, Ide, Yukio, Abe, Michiharu, Kageyama, Yoshiyuki, Iwasaki, Hiroko
• Primary Examiner(s): DINH, TAN X
• Application Number:
  US08/631,327
• Time in Patent Office: 781 Days
• Field of Search: 369/116, 369/54, 369/59, 369/14, 369/126, 369/48, 369/47, 369/110
• US Class Current: 369/59.11
• CPC Class Codes: G11B 20/1403 characterised by the use of two levels
• CPC Class Codes: G11B 20/1816 Testing
• CPC Class Codes: G11B 7/00454 involving phase-change effects
• CPC Class Codes: G11B 7/005 Reproducing G11B7/0065 takes precedence
• CPC Class Codes: G11B 7/006 Overwriting G11B7/0065 takes precedence
• CPC Class Codes: G11B 7/0062 Overwriting strategies, e.g. recording pulse sequences with erasing level used for phase-change media
• CPC Class Codes: G11B 7/126 Circuits, methods or arrangements for laser control or stabilisation
• CPC Class Codes: G11B 7/1267 Power calibration
• CPC Class Codes: G11B 7/24 Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the arrangement of information on the carrier G11B7/007

Abstract

When recording data according to the PWM recording system by modulating signals, pulse modulation for pulse modulation for recording for recording a 0 signal or the like having a signal width of nT (T: Clock time) after modulation is a continuous electro-magnetic wave at a power level e, a record signal pulse array for recording a 1 signal or the like having a signal width of nT after modulation comprises a pulse section fp having a time width x and a power level a, a multi-pulse section mp in which a low level pulse at a power level b and a high power pulse at a power level c having a time width T in total alternately appear (n-n'"'"') times in all with a duty ratio y, and a pulse section op having a time width z and a power level d, and x, y, z are integers satisfying the conditions of 0.5 T≦x≦2 T, 0.4≦y≦0.6 and 0.5 T≦z≦1 T, and n'"'"' is a positive integer which is equal to or smaller than n, and controls are provided so that the condition of (a and c)>e >(b and d) is satisfied.

Claims

1. A pulse width modulation (PWM) data recording/regenerating method, comprising the steps of:

providing a data recording medium comprising a recording layer; and

irradiating the recording layer with an electromagnetic wave to generate a phase change therein, whereby data is selectively recorded in, or rewritten in, said recording layer,

wherein, in thus transferring data to or from said data recording medium by modulating signals according to the PWM system,

pulse modulation for recording when recording or rewriting a 0 signal having a signal width of nT (where T is clock time) after modulation is a continuous electromagnetic wave at a power level e, a record signal pulse array when recording or rewriting one signal having a signal width of "nT" (where n is an integer, and n≦

1) after modulation is an electromagnetic wave pulse array comprising a pulse section fp having a time width x and a power level a, a multi-pulse section mp in which lower level pulses at a power level b having a time width of T in total, n is an integer, and high power level pulses at a power level c alternately appear at a duty ratio of y (n-n'"'"') times in total (where n'"'"' is also an integer, and n'"'"'≦

n), and a pulse section op having a time width z and a power level d;

x, y and z satisfy the relationships 0.5 T≦

x≦

2 T, 0.4≦

y≦

0.6, and 0.5 T≦

z≦

1 T; and

also controls are provided so that the relationship (a and c)≧

e≧

(b and d) is satisfied,

pulse modulation for recording when recording or rewriting a signal having a prespecified signal width after modulation is a continuous electromagnetic wave at a first power level,

pulse modulation for recording pulse array when recording or rewriting a single signal having a prespecified signal width after modulation is an electromagnetic wave pulse array comprising a pulse section having a first time width and a second power level,

a multi-pulse section in which low level pulses each at a third power level having a time width totally equal to a clock time and high level pulses each at a fourth power level alternately appear at a prespecified duty ratio prespecified times, and

a pulse section having a second time width and a fifth power level, said first time width, said duty ratio, and said second time width are respectively set according to a linear speed.

2. The method according to claim 1, wherein:

a system of modulating a signal to be recorded is one of an EFM modulating system or an improvement thereof, and n'"'"'=2.

3. The method according to claim 1, wherein:

when regenerating data, a signal detected by a detecting means from the data recording medium is subjected to DC coupling according to

space="preserve" listing-type="equation">m=(I1-I2)/I1×

100

in which I1 indicates a high level in an output level of this DC coupling and I2 indicates a low level thereof are computed, and at least one of a and c is substantially decided according to this m.

4. The method according to claim 1, wherein:

a signal detected by the detecting means when regenerating data from the data recording medium is subjected to an AC coupling according to

space="preserve" listing-type="equation">β

=(S1+S2)/(S1-S2)×

100

in which S1 indicates a high level and S2 indicates a low level in an output of the AC coupling and S1 and S2 are computed, and at least one of e, a and c is substantially decided according to this β

.

5. The method according to claim 1, comprising the further step of:

detecting an error, and deciding b and d substantially according to the error.

6. The method according to claim 1, wherein:

a signal is selectively recorded and/or rewritten by controlling a power level of an electromagnetic wave so that β

is not less than -2 and not more than 10.

7. The method according to claim 1, wherein:

a signal is selectively recorded and/or rewritten by controlling a power level of an electromagnetic wave so that e/a or e/c is not less than 0.3 and not more than 0.7.

8. The method according to claim 1, wherein:

x, y, z, and a power level of an electromagnetic wave for regenerating a signal are decided according to an amplitude of a reflected wave when data is regenerated from the data recording medium.

9. The method according to claim 1, wherein:

the data recording medium is rotated at a rotational linear speed of not less than 1.2 m/s and not more than 5.6 m/s, where data is recorded therein.

10. The method according to claim 1, wherein:

x satisfies the relationship 1 T≦

x≦

1.75 T.

11. The method according to claim 1, wherein:

z satisfies the relationship 0.5 T≦

z≦

1 T.

12. The method according to claim 1, wherein:

x, y and z satisfy the relationships 1 T≦

x≦

1.75 T, 0.4≦

y≦

0.6, and 0.5 T≦

z≦

1 T, respectively, when the data recording medium is moved at a standard linear speed for a compact disk.

60. The method according to claim 1, wherein:

said data recording medium comprises at least a substrate, a heat-resisting protection layer, and a recording layer.

13. A data recording/regenerating method, comprising the steps of:

providing a data recording medium comprising a recording layer; and

irradiating the recording layer with an electromagnetic wave to generate a phase change therein, whereby data is selectively recorded in, regenerated from, or rewritten in, said data recording layer,

wherein, in thus transferring data to or from said data recording medium by modulating signals according to the PWM recording system,

pulse modulation for recording when recording or rewriting a 0 signal having a signal width of nT is a clock time) after modulation is a continuous electromagnetic wave at a power level e, pulse modulation for recording pulse array when recording or rewriting a signal having a signal width of nT (where n is an integer, and n≦

1) after modulation is an electromagnetic wave pulse array comprising a pulse section fp having a time width x and a power level a, a multi-pulse section mp in which lower level pulses at a power level b having a time width of T in total, and high power level pulses at a power level c alternately appear at a duty ratio of y (n-n'"'"') times in total (where n'"'"' is also an integer, and n'"'"'-n), and a pulse section op having a time width z and a power level d,;

x, y, and z satisfy the relationships 0.5 T≦

x≦

2 T, 0.4≦

y≦

0.6, and 0.5 T≦

z≦

1 T, respectively, and relationship (a and c)>

e>

(b and d).

14. The method according to claim 13, wherein:

a system of modulating a signal to be recorded is one of an EFM modulating system or an improvement thereof, and n'"'"'=2.

15. The method according to claim 13, wherein:

when regenerating data, a signal detected by a detecting means from the data recording medium is subjected to DC coupling according to

space="preserve" listing-type="equation">m=(I1=I2)/I1×

100

in which I1 indicates a high level and I2 indicates a low level in an output of the DC coupling, and I1 and I2 are computed, and at least one of a and c is substantially decided according to this m.

16. The method according to claim 13, wherein:

a signal detected by the detecting means from the data recording medium when regenerating data from the data recording medium is subjected to AC coupling according to;

space="preserve" listing-type="equation">β

=(S1+S2)/(S1-S2)×

100,

in which S1 indicates a high level and S2 indicates a low level in an output level of the AC coupling and S1 and S2 are computed, and at least one of e, a and c is substantially decided according to this β

.

17. The method according to claim 13, comprising the further step of:

detecting an error and deciding b and d substantially according to the error.

18. The method according to claim 13, wherein:

a signal is selectively recorded and/or rewritten by controlling a power level of an electromagnetic wave so that β

is not less than -2 and not more than 10.

19. The method according to claim 13, wherein:

a signal is selectively recorded and/or rewritten by controlling a power level of an electromagnetic wave so that e/a or e/c is not less than 0.3 and not more than 0.7.

20. The method according to claim 13, wherein:

x, y, z, and a power level of an electromagnetic wave for regenerating a signal are decided according to an amplitude of a reflected wave when data is regenerated from the data recording medium.

21. The method according to claim 13, wherein:

the data recording medium is rotated at a rotational linear speed of not less than 1.2 m/s and not more than 5.6 m/s, where data is recorded therein.

22. The method according to claim 13, wherein:

x satisfies the relationship 1 T≦

x≦

1.75 T.

23. The method according to claim 13, wherein:

z satisfies the relationship 0.5 T≦

z≦

1 T.

24. The method according to claim 13, wherein:

x, y and z satisfy the relationships 1 T≦

x≦

1.75 T, 0.4≦

y≦

0.6, and 0.5 T≦

z≦

1 T, respectively when the data recording medium is moved at a standard linear speed for a compact disk.

25. A data recording/regenerating apparatus in which, by irradiating an electromagnetic wave to a data recording medium to generate a phase change in a recording layer, data is recorded in and regenerated from said data recording medium, and in which rewriting of data is also possible, comprising:

a recording means for recording data in a data recording medium by modulating signals according to a PWM recording system; and

a recording control means for controlling said recording means,

wherein, in recording data in said data recording medium by modulating signals according to the PWM recording system, pulse modulation for recording when recording or rewriting a signal having a prespecified signal width after modulation is a continuous electromagnetic wave at a first power level, and

wherein pulse modulation for recording pulse array when recording or rewriting a signal having a prespecified signal width after modulation is an electromagnetic wave pulse array comprising a pulse section having a first time width and a second power level, a multi-pulse section in which low level pulses each at a third power level having a time width totally equal to a clock time and high level pulses each at a fourth power level alternately appear at a prespecified duty ratio prespecified times, and a pulse section having a second time width and a fifth power level, and

wherein said recording control means sets said first time width, said duty ratio and said second time width, respectively, according to a linear speed.

26. The apparatus according to claim 25, wherein:

said recording means modulates a signal to be recorded according to an EFM modulating system or an improvement thereof, and n'"'"'=2.

27. The apparatus according to claim 25, comprising:

a detecting means for detecting a signal from said data recording medium when regenerating data from said data recording medium;

a DC coupling means for subjecting a signal detected by the detecting means to a DC coupling; and

a means for computing m=(I1-I2)/I1×

100, from a high level I1 to a low level I2 in an output from the DC coupling means, and deciding at least one of a and c according to the computed m.

28. The apparatus according to claim 25, comprising:

a detecting means for detecting a signal from the data recording medium when regenerating data from the data recording medium;

an AC coupling means for subjecting a signal detected by the detecting means to an AC coupling; and

a means for computing β

=(S1+S2)/(S1-S2)×

100, from a high level S1 to a low level S2 in an output level of the AC coupling, and deciding at least one of e, a and c substantially according to this β

.

29. The apparatus according to claim 25, comprising:

a means for detecting an error and deciding b and d substantially according to the error.

30. The apparatus according to claim 25, comprising:

a means for selectively having a signal recorded and/or rewritten by controlling a power level of an electromagnetic wave so that β

is not less than -2 and not more than 10.

31. The apparatus according to claim 25, comprising:

a means for selectively having a signal recorded and/or rewritten by controlling a power level of an electromagnetic wave so that e/a and e/c are each not less than 0.3 and not more than 0.7.

32. The apparatus according to claim 25, comprising:

a means for deciding x, y, z and a power level of an electromagnetic wave for regenerating a signal according to an amplitude of a reflected wave when regenerating data from the data recording medium.

33. The apparatus according to claim 25, wherein:

the data recording medium is rotated at a rotational linear speed of not less than 1.2 m/s and not more than 5.6 m/s when data is recorded therein.

34. The apparatus according to claim 25, wherein:

the data recording medium is rotated at a rotational linear speed of not less than 1.2 m/s and not more than 5.6 m/s where data is recorded therein.

35. The apparatus according to claim 25, comprising:

a means for temporally storing therein a portion of data to be recorded.

36. The apparatus according to claim 25, comprising:

a means for increasing a rotational linear speed of the data recording medium, when data is recorded therein, to a level higher than a rotational linear speed of the data recording medium when data is regenerated therefrom.

37. A data recording/regenerating apparatus in which, by irradiating an electromagnetic wave to a data recording medium to generate a phase change in a recording layer, data is recorded in and regenerated from said data recording medium, and in which rewriting of data is also possible, comprising:

a recording means for recording data in said data recording medium by modulating signals according to a PWM recording system,

wherein, in said recording means, pulse modulation for recording when recording or rewriting a 0 signal having a signal width of nT (where T is a clock time) after modulation is a continuous electromagnetic wave at a power level e, pulse modulation for recording a pulse array when recording or rewriting a signal having a signal width of nT after modulation is an electromagnetic wave pulse array comprising a pulse section fp having a time width x and a power level a, a multi-pulse section mp in which lower level pulses at a power level b having a time width of T in total and high power level pulses at a power level c alternately appear at a duty ratio of y (n-n'"'"') times in total, and a pulse section op having a time width z and a power level d,

wherein x, y, and z satisfy the relationships 0.5 T≦

x≦

2 T, 0.4≦

y≦

0.6, and 0.5 T≦

z≦

1 T, respectively, n'"'"' is an integer equal to or smaller than n; and

relationships (a and c)>

e>

(b and d) are satisfied.

38. The apparatus according to claim 37, wherein:

said recording means modulates a signal to be recorded according to an EFM modulating system or an improvement thereof, and n'"'"'=2.

39. The apparatus according to claim 37, comprising:

a detecting means for detecting a signal from said data recording medium when regenerating data from said data recording medium;

a DC coupling means for subjecting a signal detected by the detecting means to a DC coupling; and

a means for computing m=(I1-I2)/I1×

100 from a high level I1 to a low level I2 in an output level from the DC coupling means, and deciding at least one of a and c according to the computed m.

40. The apparatus according to claim 37, comprising:

a detecting means for detecting a signal from the data recording medium when regenerating data from the data recording medium;

an AC coupling means for subjecting a signal detected by this detecting means to an AC coupling; and

a means for computing β

=(S1+S2)/(S1-S2)×

100 from a high level S1 to a low level S2 in an output of the AC coupling, and deciding at least one of e, a and c substantially according to the computed β

.

41. The apparatus according to claim 37, comprising:

a means for detecting an error and deciding b and d substantially according to the error.

42. The apparatus according to claim 37, comprising:

a means for selectively having a signal recorded and/or rewritten by controlling a power level of an electromagnetic wave so that β

is not less than -2 and not more than 10.

43. The apparatus according to claim 37, comprising:

a means for selectively having a signal recorded and/or rewritten by controlling a power level of an electromagnetic wave so that e/a or e/c is not less than 0.3 and not more than 0.7.

44. The apparatus according to claim 37, comprising:

a means for deciding x, y, z and a power level of an electromagnetic wave for regenerating a signal according to an amplitude of a reflected wave when regenerating data from the data recording medium.

45. The apparatus according to claim 37, wherein:

the data recording medium is rotated at a rotational linear speed of not less than 1.2 m/s and not more than 5.6 m/s when data is recorded therein.

46. The apparatus according to claim 37, wherein:

the data recording medium is rotated at a rotational linear speed of not less than 1.2 m/s and not more than 5.6 m/s, where data is recorded therein.

47. The apparatus according to claim 37, comprising:

a means for temporally storing therein a portion of data to be recorded.

48. The apparatus according to claim 37, comprising:

a means for increasing a rotational linear speed of the data recording medium, when data is recorded therein, to a level higher than a rotational linear speed of the data recording medium when data is regenerated therefrom.

49. The apparatus according to claim 37, wherein:

said data recording medium further comprises at least one of a substrate and a heat-resisting protection layer.

50. The apparatus according to claim 49, wherein:

the data recording medium further comprises a reflecting/radiating layer.

51. The apparatus according to claim 49, wherein:

said heat-resisting protection layer is provided at both sides of said recording layer so that the heat-resisting protection layer holds the recording layer from the two sides.

52. The apparatus according to claim 49, wherein:

a film thickness of said heat-resisting protection layer provided between said substrate and said recording layer is in a range from 500 to 2500 angstroms.

53. The apparatus according to claim 49, wherein:

a film thickness of said heat-resisting protection layer is in a range from 100 to 1500 angstroms.

54. The apparatus according to claim 49, wherein:

main constituent elements of said recording layer are Ag, In, Sb and Te.

55. The apparatus according to claim 49, wherein:

a film thickness of said recording layer is in a range from 100 to 1000 angstroms.

56. The apparatus according to claim 49, wherein:

said substrate is composed of at least one of glass, ceramics, or resin.

57. The apparatus according to claim 49, wherein:

a material for said heat-resisting protection layer is a metallic oxide such as SiO, SiO₂, ZnO, SnO₂, Al₂ O₂, TiO₂, In₂ O₂, MgO, or ZrO₂ ;

a nitride such as Si₂ N₄, AlN, TiN, BN, or ZrN;

a sulfide such as ZnS, In₂ S₃, and TaS₄ ;

a carbide such as SiC, Tac, B₄ C, WC, TiC, or ZrC;

a diamond carbon or a mixture thereof.

58. The apparatus according to claim 49, wherein:

said reflecting/radiating layer is composed of a metallic material selected from a group consisting of Al, Au, and an alloy thereof.

59. The apparatus according to claim 50,wherein:

a film thickness of said reflecting/radiating layer is in a range from 300 to 2000 angstroms.