U.S. patent number RE40,556 [Application Number 11/200,545] was granted by the patent office on 2008-10-28 for multi-layer information recording medium and information recording and reproducing apparatus.
This patent grant is currently assigned to Pioneer Corporation. Invention is credited to Takanori Maeda, Seiichi Ohsawa.
United States Patent |
RE40,556 |
Ohsawa , et al. |
October 28, 2008 |
Multi-layer information recording medium and information recording
and reproducing apparatus
Abstract
A multi-layer-information-recording medium is applied to an
information recording and reproducing apparatus capable of
recording or reproducing information on and from either of a
single-layer-information-recording medium having a single recording
layer on one side, and a multi-layer-information-recording layer
having a plurality of recording layers layered on a spacer layer on
one side as a change in reflectivity by irradiating a light beam.
The multi-layer-information-recording medium is compatible in terms
of at least reproducing and recording with a
single-layer-information-recording medium having a cover layer
having a predetermined refractive index "n" and a thickness "t"
disposed on a recording layer on a light incident side surface. The
multi-layer-information-recording medium includes a deepest
recording layer deepest from the light incident side surface. The
deepest recording layer is formed at an optical distance d1 from
the light incident side surface satisfying an equation d1=nt. The
multi-layer-information-recording medium also includes at least one
shallow recording layer formed at an optical distance d2 satisfying
an inequality d2<nt from the light incident side surface.
Inventors: |
Ohsawa; Seiichi (Tsurugashima,
JP), Maeda; Takanori (Tsurugashima, JP) |
Assignee: |
Pioneer Corporation (Tokyo,
JP)
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Family
ID: |
19000481 |
Appl.
No.: |
11/200,545 |
Filed: |
August 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11094756 |
Mar 31, 2005 |
Re. 39322 |
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Reissue of: |
10147979 |
May 20, 2002 |
06773781 |
Aug 10, 2004 |
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Foreign Application Priority Data
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May 25, 2001 [JP] |
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2001-156477 |
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Current U.S.
Class: |
428/64.1;
430/270.11; 428/64.4 |
Current CPC
Class: |
G11B
7/13925 (20130101); G11B 7/00745 (20130101); G11B
7/0945 (20130101); G11B 7/08511 (20130101); G11B
7/24038 (20130101); G11B 2007/0013 (20130101); Y10T
428/21 (20150115); G11B 2007/0006 (20130101) |
Current International
Class: |
B32B
3/02 (20060101) |
Field of
Search: |
;428/64.1,64.4
;430/270.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 694 915 |
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Jan 1996 |
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EP |
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03-054740 |
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Mar 1991 |
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JP |
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05-151591 |
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Jun 1993 |
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JP |
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09-054981 |
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Feb 1997 |
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JP |
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09-138970 |
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May 1997 |
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JP |
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Other References
European Search Report dated Jan. 3, 2005 for European Patent
Application No. 05 00 1940. cited by other .
Office Action issued by Japanese Patent Office on Jul. 27, 2005 for
Japanese Patent Application No. 2001-156477. cited by
other.
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Primary Examiner: Mulvaney; Elizabeth
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP
Parent Case Text
.Iadd.CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation reissue application of U.S.
Reissue patent application Ser. No. 11/094,756, filed Mar. 31, 2005
now U.S. Pat. No. RE. 39,322, which is a reissue application of
U.S. Pat. No. 6,773,781 B2, issued Aug. 10, 2004, from U.S. patent
application Ser. No. 10/147,979, filed on May 20, 2002, the
entirety of which is incorporated herein by reference. This
application claims the benefits of priority under 35 U.S.C. .sctn.
119,120 to Japanese Patent Application No. 2001-156477, which was
filed in the Japanese Patent Office on May 25, 2001, the entirety
of which is incorporated herein by reference. Other related reissue
applications claiming priority to this reissue application include
U.S. Reissue patent application Ser. No. 11/200,543, filed Aug. 10,
2005, now pending; and U.S. Reissue patent application Ser. No.
11/200,544, filed Aug. 10, 2005, now pending..Iaddend.
Claims
What is claimed is:
.[.1. A multi-layer-information-recording medium having a plurality
of recording layers layered on a spacer layer on one side and
adapted to an information recording and reproducing apparatus
capable of recording or reproducing information on a
single-layer-information-recording medium having a single recording
layer and a cover layer on one side as a change in reflectivity by
irradiating a light beam through the cover layer onto the recording
layer, said multi-layer-information-recording medium comprising: a
deepest recording layer disposed deepest from a light incident side
surface at an optical distance d1 satisfying an equation d1=nt
wherein "n" denotes a predetermined refractive index of the cover
layer of the single-layer-information-recording medium compatible
in terms of at least reproducing and recording with said
multi-layer-information-recording medium and "t" denotes a
thickness of said cover layer; and at least one shallow recording
layer disposed at an optical distance d2 satisfying an inequality
d2<nt from the light incident side surface..].
.[.2. A multi-layer-information-recording medium according to claim
1, wherein said multi-layer-information-recording medium consists
of said deepest recording layer and said shallow recording layer as
only two layers..].
.[.3. A multi-layer-information-recording medium according to claim
1, wherein said multi-layer-information-recording medium includes
physical address information recorded sequentially from said
shallow recording layer to said deepest recording layer in a
shallower order from the light incident side surface..].
.[.4. A multi-layer-information-recording medium according to claim
1, wherein said multi-layer-information-recording medium includes
physical address information sequentially recorded in order from an
inner periphery to an outer periphery of said deepest recording
layer..].
.[.5. A multi-layer-information-recording medium according to claim
4, wherein said multi-layer-information-recording medium includes
the physical address information sequentially recorded alternately
in a forward direction from the inner periphery to the outer
periphery and in an opposite direction from the outer periphery to
the inner periphery in each of the recording layers from said
shallow recording layer to said deepest recording layer in the
shallower order from the light incident side surface..].
.[.6. A multi-layer-information-recording medium according to claim
1, wherein said multi-layer-information-recording medium includes
predetermined content information related to all contents on said
shallow recording layer recorded in said deepest recording
layer..].
.[.7. An information recording and reproducing apparatus capable of
recording or reproducing information on either of a
single-layer-information-recording medium having a single recording
layer and a multi-layer-information-recording medium having a
plurality of recording layers layered on a spacer layer on one side
by irradiating a light beam thereto, said information recording and
reproducing apparatus comprising: an optical pickup having an
objective lens which irradiates a light beam to a
multi-layer-information-recording medium which includes a deepest
recording layer disposed deepest from a light incident side surface
at an optical distance d1 satisfying an equation d1=nt wherein "n"
denotes a predetermined refractive index of the cover layer of the
single-layer-information-recording medium compatible in terms of at
least reproducing and recording with said
multi-layer-information-recording medium and "t" denotes a
thickness of said cover layer, and at least one shallow recording
layer disposed at an optical distance d2 satisfying an inequality
d2<nt from the light incident side surface; and a focus servo
circuit which controls the objective lens to first of all focus the
light beam to said deepest recording layer at the optical distance
d1, and executes an initial focus servo operation..].
.[.8. An information recording and reproducing apparatus according
to claim 7, wherein said focus servo circuit executes a focus servo
operation for jumping a focused position to said shallow recording
layer at the optical distance d2 after executing said initial focus
servo operation..].
.[.9. An information recording and reproducing apparatus according
to claim 7, wherein said objective lens has a numerical aperture
equal to or larger than 0.8 for producing a focused spot of the
light beam..].
.[.10. An information recording and reproducing apparatus according
to claim 9, further comprising an wave aberration correcting
portion which varies the amount of wave aberration included in said
focused spot..].
.[.11. An information recording and reproducing apparatus according
to claim 9, wherein said objective lens comprises a group of lenses
which minimizes the amount of wave aberration in the light beam
when the spot is focused at a position spaced by the optical
distance d1..].
.Iadd.12. A multi-layer-information-recording medium that is
compatible with a single-layer-information-recording medium in
terms of reproducing or recording, the
single-layer-information-recording medium having a cover layer
having a refractive index "n" and a thickness "t" on the light
incident side, said multi-layer-information-recording medium
comprising a first recording layer and a second recording layer
that are layered in order from the light incident side surface of
the multi-layer-information-recording medium, wherein the second
recording layer is disposed at an optical distance "d1" from the
light incident side surface satisfying an equation d1=n.times.t;
wherein the first recording layer is disposed at an optical
distance "d2" from the light incident side surface satisfying an
inequality d2<n.times.t; and wherein the second recording layer
has an information region for recording content information related
to contents of said first recording layer..Iaddend.
.Iadd.13. A multi-layer-information-recording medium according to
claim 12, wherein said content information is related to all
contents of said first and second recording layers..Iaddend.
.Iadd.14. A multi-layer-information-recording medium according to
claim 12, wherein said content information is recorded in said
information region..Iaddend.
.Iadd.15. A multi-layer-information-recording medium according to
claim 12, wherein a physical address information is recorded from
said second recording layer to said first recording
layer..Iaddend.
.Iadd.16. A multi-layer-information-recording medium according to
claim 12, wherein a physical address information is recorded in
order from an inner periphery to an outer periphery of said second
recording layer..Iaddend.
.Iadd.17. A multi-layer-information-recording medium according to
claim 16, wherein the physical address information is recorded in
order from an outer periphery to an inner periphery of said first
recording layer..Iaddend.
.Iadd.18. A multi-layer-information-recording medium according to
claim 12, wherein a compatibility of the
multi-layer-information-recording medium and the
single-layer-information-recording medium is common in disc
diameter, overall disc thickness, and track pitch..Iaddend.
.Iadd.19. A multi-layer-information-recording medium according to
claim 18, wherein a compatibility of the
multi-layer-information-recording medium and the
single-layer-information-recording medium is common in minimum
pitch length, bowing angle, birefringence, and format..Iaddend.
.Iadd.20. A multi-layer-information-recording medium that is
compatible with a single-layer-information-recording medium in
terms of reproducing or recording, the
single-layer-information-recording medium having a cover layer
having a refractive index "n" and a thickness "t" on the light
incident side, said multi-layer-information-recording medium
comprising a cover layer, a first recording layer, a spacer layer,
and a second recording layer that are layered in order from the
light incident side surface of the
multi-layer-information-recording medium, wherein on condition that
the cover layer has a refractive index "nC" and a thickness "tC"
and the first recording layer has a refractive index "nL1" and a
thickness "tL1" and the spacer layer has a refractive index "nS"
and a thickness "tS", the second recording layer is disposed at an
optical distance "d1" from the light incident side surface
satisfying an equation
d1=n.times.t=nC.times.tC+nL1.times.tL1+nS.times.tS; wherein the
first recording layer is disposed at an optical distance "d2" from
the light incident side surface satisfying an equation
d2=nC.times.tC<n.times.t; and wherein the second recording layer
has an information region for recording content information related
to contents of said first recording layer..Iaddend.
.Iadd.21. A multi-layer-information-recording medium according to
claim 20, wherein said content information is related to all
contents of said first and second recording layers..Iaddend.
.Iadd.22. A multi-layer-information-recording medium according to
claim 20, wherein said content information is recorded in said
information region..Iaddend.
.Iadd.23. A multi-layer-information-recording medium according to
claim 20, wherein a physical address information is recorded from
said second recording layer to said first recording
layer..Iaddend.
.Iadd.24. A multi-layer-information-recording medium according to
claim 20, wherein a physical address information is recorded in
order from an inner periphery to an outer periphery of said second
recording layer..Iaddend.
.Iadd.25. A multi-layer-information-recording medium according to
claim 24, wherein the physical address information is recorded in
order from an outer periphery to an inner periphery of said first
recording layer..Iaddend.
.Iadd.26. A multi-layer-information-recording medium according to
claim 20, wherein a compatibility of the
multi-layer-information-recording medium and the
single-layer-information-recording medium is common in disc
diameter, overall disc thickness, and track pitch..Iaddend.
.Iadd.27. A multi-layer-information-recording medium according to
claim 26, wherein a compatibility of the
multi-layer-information-recording medium and the
single-layer-information-recording medium is common in minimum
pitch length, bowing angle, birefringence, and format..Iaddend.
.Iadd.28. A multi-layer-information-recording medium that is
compatible with a single-layer-information-recording medium in
terms of reproducing or recording, the
single-layer-information-recording medium having a cover layer
having a refractive index "n" and a thickness "t" on the light
incident side, said multi-layer-information-recording medium
comprising a deepest recording layer and one or more shallow
recording layers shallower than the deepest recording layer that
are layered in order from the light incident side surface of the
multi-layer-information-recording medium, wherein the deepest
recording layer is disposed at an optical distance "d1" from the
light incident side surface satisfying an equation d1=n.times.t;
wherein the shallow recording layer is disposed at an optical
distance "d2" from the light incident side surface satisfying an
inequality d2<n.times.t; wherein the deepest recording layer has
an information region for recording content information related to
contents of said shallow recording layer..Iaddend.
.Iadd.29. A multi-layer-information-recording medium according to
claim 28, wherein said content information is related to all
contents of said shallow and deepest recording layers..Iaddend.
.Iadd.30. A multi-layer-information-recording medium according to
claim 28, wherein said content information is recorded in said
information region..Iaddend.
.Iadd.31. A multi-layer-information-recording medium according to
claim 28, wherein said multi-layer-information-recording medium
consists of said deepest recording layer and said shallow recording
layer as only two layers..Iaddend.
.Iadd.32. A multi-layer-information-recording medium according to
claim 28, wherein a physical address information is recorded from
said deepest recording layer to said shallow recording
layer..Iaddend.
.Iadd.33. A multi-layer-information-recording medium according to
claim 28, wherein a physical address information is recorded in
order from an inner periphery to an outer periphery of said deepest
recording layer..Iaddend.
.Iadd.34. A multi-layer-information-recording medium according to
claim 33, wherein the physical address information is recorded in
order from an outer periphery to an inner periphery of said shallow
recording layer..Iaddend.
.Iadd.35. A multi-layer-information-recording medium according to
claim 28, wherein a compatibility of the
multi-layer-information-recording medium and the
single-layer-information-recording medium is common in disc
diameter, overall disc thickness, and track pitch..Iaddend.
.Iadd.36. A multi-layer-information-recording medium according to
claim 35, wherein a compatibility of the
multi-layer-information-recording medium and the
single-layer-information-recording medium is common in minimum
pitch length, bowing angle, birefringence, and format..Iaddend.
.Iadd.37. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 12..Iaddend.
.Iadd.38. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 13..Iaddend.
.Iadd.39. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 14..Iaddend.
.Iadd.40. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 15..Iaddend.
.Iadd.41. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 16..Iaddend.
.Iadd.42. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 17..Iaddend.
.Iadd.43. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 18..Iaddend.
.Iadd.44. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 19..Iaddend.
.Iadd.45. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 20..Iaddend.
.Iadd.46. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 21..Iaddend.
.Iadd.47. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 22..Iaddend.
.Iadd.48. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 23..Iaddend.
.Iadd.49. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 24..Iaddend.
.Iadd.50. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 25..Iaddend.
.Iadd.51. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 26..Iaddend.
.Iadd.52. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 27..Iaddend.
.Iadd.53. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 28..Iaddend.
.Iadd.54. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 29..Iaddend.
.Iadd.55. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 30..Iaddend.
.Iadd.56. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 31..Iaddend.
.Iadd.57. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 32..Iaddend.
.Iadd.58. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 33..Iaddend.
.Iadd.59. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 35..Iaddend.
.Iadd.60. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 35..Iaddend.
.Iadd.61. An information reproducing apparatus for reproducing
information from a multi-layer-information-recording medium
according to claim 36..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an information recording
medium such as an optical disc, an optical card and the like, and
more particularly to a multi-layer-information-recording medium
which has a plurality of recording layers layered on spacer
layers.
2. Description of the Related Art
In recent years, optical discs are widely used as means for
recording and reproducing data such as video data, audio data,
computer data and the like. A high density recording disc called
DVD (Digital Versatile Disc) has been used in practice. As one type
of DVD, there is a multi-layer disc in a laminate structure which
has a plurality of recording layers that can be read from one side
of the disc. A two-layer disc having two recording layers on one
side has been used in practice as a disc dedicated to
reproduction.
As illustrated in FIG. 1, the two-layer DVD dedicated to
reproduction comprises a shallow recording layer, which is the
first layer viewed from the side on which data is read, i.e.,
closer to a light incident side surface, and a deep or second
recording layer. With the two-layer disc, any signal recorded in
the shallow recording layer and the deep recording layer can be
read from one side of the disc only by moving the focus of a
reproducing light beam. The shallow recording layer is made of a
translucent film such that a light beam can transmit the shallow
recording layer and read a signal from the deep recording layer,
and the film thickness and material are chosen conveniently for the
shallow recording layer. A reflective film is used for the deep
recording layer. An optically transparent spacer layer having a
high transmittance at the wavelength of light is disposed between
the shallow recording layer and the deep recording layer in order
to separate these layers by a constant distance.
The DVD standard defines that a transparent cover layer on a
recording layer of a single-layer disc, having only one recording
layer, 600 .mu.m thick, as illustrated in FIG. 2. On the other
hand, a two-layer disc is formed to have a first recording layer
and a second recording layer positioned at depths of 570 .mu.m and
630 .mu.m from the surface on which a light beam is incident, i.e.,
above and below the depth of 600 .mu.m at which the recording layer
of a single-layer DVD is disposed. The positioning of the two
layers above and below the single recording layer in the thickness
direction is employed in the two-layer disc because an optical
pickup system for recording and reproducing signals conforming to
the DVD standard comprises an objective lens having a relatively
small numerical aperture of 0.6 which is designed for the cover
layer of 600 .mu.m thick, and even with such an objective lens
having a small numerical aperture, a deviation of approximately 30
.mu.m in depth of the first layer and the second layer each from
the single recording layer does not significantly affect the
reading of signals. In this event, though the deviation of 30 .mu.m
of the recording layers causes wave aberration in a reading light
beam, the amount of wave aberration is too small to cause a problem
when the numerical aperture is on the order of 0.6.
A long program such as a movie which overflows the first recording
layer of the two-layer disc is reproduced from the two recording
layers. The DVD standard also defines a single side
signal-reproducing scheme, called an opposite track path scheme,
for continuously reproducing from two layers. The opposite track
path scheme involves reproducing from the recording layer at a
depth of 570 .mu.m from the inner periphery to the outer periphery,
jumping the focus from the outer periphery of this recording layer
to the recording layer at a depth of 630 .mu.m, and reproducing
signals on the deeper recording layer from the outer periphery to
the inner periphery. In this event, by reading an information
region representing the contents of the disc recorded on the layer
at a depth of 570 .mu.m, the apparatus can sense the title of the
DVD, a program duration, or the two-layer disc in accordance with
the opposite track path scheme.
Meanwhile, an increasing amount of information requires a higher
density for next-generation optical disc. It is considered that the
numerical aperture of the objective lens be increased to 0.8 or
more for a higher density. When using an objective lens having such
a large numerical aperture, the amount of wave aberration caused by
an error in thickness of the cover layer on the recording layer
increases too much to read signals, thereby failing to readily
reproduce a next-generation optical disc when it is in a two
recording layer structure. It is therefore considered that an
optical system capable of adjusting the amount of wave aberration
should be incorporated in a pickup to make a compensation for
preventing the wave aberration in accordance with the depth of a
recording layer.
When an optical system for compensating for the wave aberration is
used to read a single-layer disc and a multi-layer disc such as a
two-layer disc of the next-generation while maintaining the
compatibility, the difference exists in thickness of a cover layer
corresponding to depths between the respective recording layers, so
that a light beam must be focused on each recording layer while
correcting the same for the wave aberration to search for lead-in
information and the like. This gives rise to a problem that the
time taken for starting reproduction becomes long if a two-layer
disc is reproduced immediately after a single-layer disc was
reproduced. In addition, with a large numerical aperture, a larger
thickness of the cover layer causes an allowable range to be
significantly narrowed down for the inclined disc, so that a
multi-layer disc which has a larger thickness of cover layer than a
single-layer disc must be fabricated with an improved planarity for
the surface of the disc more than the single-layer disc.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made in view of the situation as
described above, and it is an object of the invention to provide a
multi-layer-information-recording medium which permits rapid data
reproduction even when information is recorded or reproduced using
an objective lens having a large numerical aperture of 0.8 or more,
and which can be fabricated with an equivalent planarity to a
single-layer disc, and an information recording and reproducing
apparatus suitable for use with the
multi-layer-information-recording medium.
According to the present invention, there is provided a
multi-layer-information-recording medium having a plurality of
recording layers layered on a spacer layer on one side and applied
to an information recording and reproducing apparatus capable of
recording or reproducing information on a
single-layer-information-recording medium having a single recording
layer and a cover layer on one side as a change in reflectivity by
irradiating a light beam through the cover layer onto the recording
layer.
The multi-layer-information-recording medium of the present
invention comprises: a deepest recording layer disposed deepest
from a light incident side surface at an optical distance d1
satisfying an equation d1=nt wherein "n" denotes a predetermined
refractive index of the cover layer of the
single-layer-information-recording medium compatible in terms of at
least reproducing and recording with said
multi-layer-information-recording medium and "t" denotes a
thickness of said cover layer; and at least one shallow recording
layer disposed at an optical distance d2 satisfying an inequality
d2<nt from the light incident side surface.
According to one aspect of the present invention, said
multi-layer-information-recording medium comprises only two layers
consisting of said deepest recording layer and said shallow
recording layer.
According to another aspect of the present invention of the
multi-layer-information-recording medium, physical address
information is recorded sequentially from said shallow recording
layer to said deepest recording layer in a shallower order from the
light incident side surface.
According to a further aspect of the present invention of the
multi-layer-information-recording medium, physical address
information is sequentially recorded in order from an inner
periphery to an outer periphery of said deepest recording
layer.
According to a still further aspect of the present invention of the
multi-layer-information-recording medium, the physical address
information is sequentially recorded alternately in a forward
direction from the inner periphery to the outer periphery and in an
opposite direction from the outer periphery to the inner periphery
in each of the recording layers from said shallow recording layer
to said deepest recording layer in the shallower order from the
light incident side surface.
According to another aspect of the present invention of the
multi-layer-information-recording medium, predetermined content
information related to all contents on said shallow recording layer
is recorded in said deepest recording layer.
According to the present invention, there is also provided an
information recording and reproducing apparatus capable of
recording or reproducing information on either of a
single-layer-information-recording medium having a single recording
layer and a multi-layer-information-recording medium having a
plurality of recording layers layered on a spacer layer on one side
by irradiating a light beam thereto.
The information recording and reproducing apparatus of the present
invention comprises: an optical pickup having an objective lens
which irradiates a light beam to a
multi-layer-information-recording medium which includes a deepest
recording layer disposed deepest from a light incident side surface
at an optical distance d1 satisfying an equation d1=nt wherein "n"
denotes a predetermined refractive index of the cover layer of the
single-layer-information-recording medium compatible in terms of at
least reproducing and recording with said
multi-layer-information-recording medium and "t" denotes a
thickness of said cover layer, and at least one shallow recording
layer disposed at an optical distance d2 satisfying an inequality
d2<nt from the light incident side surface; and a focus servo
circuit which controls the objective lens to, first of all, focus
the light beam to said deepest recording layer at the optical
distance d1, and executes an initial focus servo operation.
According to one aspect of the present invention of the information
recording and reproducing apparatus, said focus servo circuit
executes a focus servo operation for jumping a focused position to
said shallow recording layer at the optical distance d2 after
executing said initial focus servo operation.
According to another aspect of the present invention of the
information recording and reproducing apparatus, said objective
lens has a numerical aperture equal to or larger than 0.8 for
producing a focused spot of the light beam
According to a further aspect of the present invention of the
information recording and reproducing apparatus, the apparatus
further comprises an wave aberration correcting portion which
varies the amount of wave aberration included in said focused
spot.
According to a still further aspect of the present invention of the
information recording and reproducing apparatus, said objective
lens comprises a group of lenses which minimizes the amount of wave
aberration in the light beam when the spot is focused at a position
spaced by the optical distance d1.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view schematically showing a two-layer
disc;
FIG. 2 is a cross-sectional view schematically showing a
single-layer disc;
FIG. 3 is a cross-sectional view schematically showing a two-layer
disc according to the present invention;
FIG. 4 is a cross-sectional view schematically showing a
single-layer disc which is compatible with the two-layer disc of
the present invention; and
FIG. 5 is a block diagram for schematically describing the
configuration of a recording and reproducing apparatus according to
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Next, embodiments of the present invention will be described with
reference to the accompanying drawings.
Two-Layer Disc
An exemplary multi-layer disc according to a first embodiment of
the present invention is a two-layer disc having a two-layer
structure comprised of recording layers L1, L2, for example, as
shown in FIG. 3. This is a two-layer disc which is compatible in
terms of reproduction or recording with a single-layer disc (FIG.
4) on which reproduction or recording is performed by a
predetermined reproducing or recording means through a cover layer
on a recording layer on a light incident side surface having a
predetermined refractive index n and a thickness t.
The deepest recording layer, i.e., the recording layer positioned
deepest from the light incident side surface of the recording
layers of the two-layer disc is covered with a cover layer having a
thickness which is related to an optical distance d1 as expressed
by d1=n.times.t.
The shallow recording layer, other than the deepest recording
layer, is covered with a cover layer having a thickness which is
related to an optical distance d2 as expressed by d2 <n.times.t.
The two-layer disc comprises the deepest recording layer formed at
the optical distance d1 which satisfies the equation d1=n.times.t,
and the shallow recording layer formed at the optical distance d2
which satisfies the inequality d2<n.times.t.
In this two-layer disc, since the deepest recording layer is set at
the optical distance d1 at the same position of the optical path
thickness as the recording layer of the single-layer disc,
information on the deepest recording layer at the optical distance
d1 can be reproduced without searching for the position of the
shallower recording layer of the multi-layer disc even by a pickup
which is adapted to minimize the wave aberration for the
single-layer disc. Also, since the optical distance d2 is set
shorter than d1, an allowance for an inclined disc, when recording
or reproducing is performed on the shallow recording layer, is not
more strict than for the single-layer disc, so that the planarity
need not be improved as compared with the single-layer disc.
With the two-layer disc, information may be recorded on the
assumption that it is reproduced from the two layers in a
predetermined order in which the shallow recording layer at the
optical distance d2 is reproduced ahead of the deepest recording
layer. Specifically, physical address information can be recorded
sequentially from the shallow recording layer to the deepest
recording layer, in an order of shallower layers from the light
incident side surface.
Further, with the two-layer disc, signals are reproduced from the
inner periphery to the outer periphery of the surface at the
optical distance d2. Alternatively, signals may be reproduced from
the outer periphery to the inner periphery of the surface at the
optical distance d1. Also, the physical address information can be
recorded in order from the inner periphery to the outer periphery
of the deepest recording layer.
By thus designing the two-layer disc, for reproducing a program
which exceeds a recording limit amount of the shallow recording
layer, remaining information recorded on the deepest recording
layer is reproduced after completion of reproduction from the
shallow recording layer having a larger allowance for an inclined
disc, so that it is possible to increase the allowance for a
normally inclined disc.
In the two-layer disc, predetermined content information related to
all contents on the two layers can be recorded on the deepest
recording layer at the optical distance d1. In this event, a signal
reproducing apparatus reads the title of the two-layer disc, a
program recording time, or predetermined information indicating
that this two-layer disc conforms to the opposite track path scheme
or the like from the deepest recording layer at the optical
distance d1, and then jumps a focused position to the inner
periphery of the shallow recording layer at the optical distance d2
and can continue to reproduce signals. Physical address information
may be sequentially recorded alternately in a forward direction
from the inner periphery to the outer periphery and in the opposite
direction from the outer periphery to the inner periphery in each
recording layer in the order of depth from the deepest recording
layer to the shallow recording layer.
With the disc on which information is recorded in the foregoing
manner, predetermined information indicative of the content of the
disc over two layers can be read in the same wave aberration
correcting state as a single-layer disc, so that the reproducing
apparatus can be aware of a two-layer disc on which information is
recorded without searching for the position of the recording layers
by its wave aberration correcting unit, and can immediately start
the reproduction. Thus, according to the present invention, when
the adjacent recording layers are reproduced from the shallow
recording layer, the optical pickup can be smoothly moved between
reproducing planes of the recording layers.
This information may be such one that is recorded in an inner
peripheral portion of the deepest recording layer as a pit, or a
bar code, or what is called a PEF which forms a bar code like one
using pits, or a wave aberration correcting signal for a region in
which a signal is recorded for use in detection of wave aberration
in order to correct the wave aberration.
When the numerical aperture of an objective lens for converging a
light spot is chosen to be 0.8 or more, the objective lens is
designed to minimize the amount of wave aberration when it focuses
through the optical distance d1.
While the foregoing example has been described for the two-layer
disc, a disc having three or more layers can be designed in a
similar manner, and other recording layers may also be provided
even if they do not satisfy the foregoing condition. Also, while
the recording density has not been described, the two recording
layers may have the same recording density, or may differ from each
other in recording density.
While in the foregoing example, the thickness of the cover layers
has been described to be equal in the length of optical path. This
can be of course realized by materials equal in the refractive
index to each other and identical in thickness. Otherwise, even
with materials having different refractive indexes, they may be
sized to be equal in the product of the refractive index and
thickness, i.e., the optical thickness (distance). Also, when a
material (spacer) filled between layers has a different refractive
index, it can be set to have an equivalent optical path length by
sequential calculations.
For example, assuming that the cover layer on the light incident
side surface of the two-layer disc has a refractive index n.sub.c
and a thickness t.sub.c, the shallow recording layer L1 has a
refractive index n.sub.L1 and a thickness t.sub.L1, and a spacer
layer between the recording layers L1, L2 has a refractive index
n.sub.s and a thickness t.sub.s the disc is designed such that the
optical distance d1 from the surface on the light incident side of
the deepest recording layer L2 satisfies
d1=n.times.t=n.sub.c.times.t.sub.c+n.sub.L1.times.t.sub.L1+n.su-
b.s.times.t.sub.s, and the optical distance d2 from the surface on
the light incident side of the shallow recording layer L1 satisfies
d2=n.sub.c.times.t.sub.c<n.times.t.
Each of the recording layers L1, L2 has a laminate structure
comprised of a recording layer made of a phase changing material
such as Ag--In--Sb--Te, and glass protection layers made of, for
example, ZnS--SiO.sub.2 or the like which sandwich the recording
layer. For an optical disc which uses a recording layer made of a
phase changing material and on which data can be recorded or
erased, i.e., rewritten using an optical beam, each recording layer
can be provided with a rewritable region in which data can be
rewritten, i.e., recorded or erased, and a prepit region which is
provided with trains of emboss pits that carry addresses as
sequential physical addresses and information such as recording
timing. While an example of rewritable two-layer disc using a phase
changing material is described, the material for the recording
layer is not limited to the phase changing material in the present
invention, but a write-once pigment material may be used. Moreover,
the two-layer disc may be implemented as a disc dedicated to
reproduction.
The single-layer and multi-layer discs compatible for reproducing
and recording are common in the disc diameter, overall disc
thickness, track pitch, minimum pitch length, bowing angle,
birefringence, format, and the like, other than the aforementioned
conditions. For example, these may conform to a CAV (constant
angular velocity) or a CLV (constant linear velocity) scheme.
Alternatively, they may be multi-layer disc in accordance with a
zone CAV or a CLV scheme which is a combination of CAV and CLV. In
addition, each recording layer of the multi-layer disc is
previously formed with convex groove tracks and concave groove
tracks alternately in a spiral or concentric shape. Each of the
groove tracks may be wobbled at a frequency corresponding to the
rotational speed of the multi-layer disc.
Recording/Reproducing Apparatus
Data is recorded on the multi-layer disc by irradiating a prepit
region and a rewritable region of a recording layer thereof with a
reproducing light beam having a low intensity (reading power) for
scanning to detect land prepits and groove prepits in the prepit
region, recognizing the position on a track to be recorded, and
irradiating the rewritable region of the track with a focused
recording light beam (writing power) having a high intensity
modulated in accordance with the data.
FIG. 5 is a block diagram illustrating the configuration of a
recording and reproducing apparatus according to the present
invention.
An optical pickup 21 comprises an optical system which includes a
focusing lens, a beam splitter, an objective lens, and the like; a
semiconductor laser which is a light source; a photodetector; an
objective lens actuator; and the like. The objective lens 21a has a
numerical aperture equal to or larger than 0.8 and produces a
focused spot of a light beam on a recording layer. The objective
lens 21a is comprised of a group of lenses which minimize the
amount of wave aberration of the light beam when either of a
compatible single-layer or multi-layer disc is loaded at a normal
position, and when the spot is focused at the optical distance d1
from the surface. The optical pickup 21 comprises a wave aberration
correcting means 21b for varying the amount of wave aberration
included in the focused spot.
When loading a multi-layer disc 1 onto a turntable 1a driven by a
spindle motor, the optical pickup 21 irradiates the multi-layer
disc 1 with a light beam as recording light or a reading light. The
optical pickup 21 comprises the photodetector which detects a
reflected light beam from a recording layer of the multi-layer disc
to read a signal corresponding to a track and prepits or recording
marks formed on the multi-layer disc 1 as a change in reflectivity.
A servo circuit 20 has a focus servo circuit and a tracking servo
circuit for performing a servo control for focusing and tracking of
the pickup, a control for a preproduced position (radial position),
a control for the rotational speed of the spindle motor, and the
like based on a control signal provided from the optical pickup 21
and a control command provided from a control unit (CPU) 26. When
the multi-layer disc in the aforementioned example, for example, a
two-layer disc is loaded, the optical beam is first irradiated to
the deepest recording layer L2 at the optical distance d1, executes
an initial focus servo operation, and performs a tracking servo and
a focus servo control for the objective lens such that the light
beam is focused correctly on the recording layer of the multi-layer
disc. The focus servo circuit also executes a focus servo operation
for jumping a focused position to the shallow recording layer L1 at
the optical distance d2 after executing the initial focus servo
operation.
A read signal (RF signal) output from the optical pickup 21 is
amplified in an amplifier circuit, and supplied to a pre-address
decoder 23 and a decoder 43.
The pre-address decoder 23 extracts prepits, wobble signals, and
the like, and a synchronous clock and timing signal generator
circuit within the pre-address decoder 23 generates a clock signal
and a timing signal in synchronism with the rotation of the
multi-layer disc 1. The timing signal represents a current position
on the disc such as a prepit region or a writable region recorded
(reproduced) by the light beam, or a land track or a groove track
or the like. The pre-address decoder 23 reads address information
from a signal read from emboss pits in the prepit region of the
disc by the pickup, and sends the address information and timing
signal to the CPU 26. The pre-address decoder 23 includes a circuit
for detecting the rewritable region and prepit region on the
multi-layer disc.
The CPU 26 detects the position of the prepit region on the
recording layer from these signals. A storage device is contained
in or connected to the CPU 26 for storing necessary data and the
like. The CPU 26 generally controls the apparatus based on signals
supplied thereto. The CPU 26 reads the address information from the
pre-address decoder 23, and sends a control command to a recording
control circuit 36 and servo circuit 20 to control a recording and
reproducing operation at a predetermined address.
The recording control circuit 36 controls the power of the laser in
the pickup in accordance with a particular state such as recording,
erasing, reproducing and the like based on a control command from
the CPU 26 and a timing signal from the pre-address decoder 23. In
a recording state, the recording control circuit 36 modulates the
power of the laser in the pickup based on a signal from an encoder
27 to record information on the disc. In a reproducing state (when
data in the rewritable region is reproduced, or when address
information in the prepit region is reproduced), the recording
control circuit 36 controls the reading power to maintain at
constant low power so as not to erase information recorded on the
disc.
The encoder 27 adds a parity code for error correction to data to
be recorded, and converts the resulting data to an RLL (Run Length
Limited) code for encoding to a signal suitable for recording on
the multi-layer disc 1. The encoded signal is sent from the encoder
27 to the recording control circuit 36.
The decoder 43 performs the processing reverse to that performed in
the encoder (demodulation of an RLL code, error correction, and the
like) on a signal read from the rewritable region of the disc to
recover originally recorded data.
As described above, the present invention provides a
multi-layer-information-recording medium which has two or more
recording layer compatible with a single-layer disc, and a cover
layer having the same optical path length as a cover layer of the
single-layer disc, with another recording layer disposed at the
position of a cover layer thinner than that, so that the
multi-layer-information-recording medium excels in stability for
planarity of the disc, and information can be recorded and
reproduced in such an order that signals can be continuously
reproduced from these recording layers.
It is understood that the foregoing description and accompanying
drawings set forth the preferred embodiments of the invention at
the present time. Various modifications, additions and alternative
designs will, of course, become apparent to those skilled in the
art in light of the foregoing teachings without departing from the
spirit and scope of the disclosed invention. Thus, it should be
appreciated that the invention is not limited to the disclosed
embodiments but may be practiced within the full scope of the
appended claims.
This application is based on a Japanese Patent Application No.
2001-156477 which is hereby incorporated by reference.
* * * * *