U.S. patent application number 11/494861 was filed with the patent office on 2007-03-22 for holographic recording medium.
Invention is credited to Toshikazu Kanaoka, Akiyoshi Uchida.
Application Number | 20070064289 11/494861 |
Document ID | / |
Family ID | 37301248 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070064289 |
Kind Code |
A1 |
Uchida; Akiyoshi ; et
al. |
March 22, 2007 |
Holographic recording medium
Abstract
A holographic recording medium according to the present
invention includes a holographic material layer in which
information is to be recorded by irradiating the same region with
information light corresponding to the information to be recorded
and reference light to read the recorded information. The
holographic material layer is divided into a plurality of recording
zones by a plurality of light shielding walls. The light shielding
wall is formed of a material which does not transmit bleaching
light to be applied to the recording zone in which a recording
process has been performed and the recorded information is to be
fixed.
Inventors: |
Uchida; Akiyoshi; (Kawasaki,
JP) ; Kanaoka; Toshikazu; (Kawasaki, JP) |
Correspondence
Address: |
GREER, BURNS & CRAIN
300 S WACKER DR
25TH FLOOR
CHICAGO
IL
60606
US
|
Family ID: |
37301248 |
Appl. No.: |
11/494861 |
Filed: |
July 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11321159 |
Dec 28, 2005 |
7133170 |
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11494861 |
Jul 28, 2006 |
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Current U.S.
Class: |
359/3 ; 359/15;
G9B/7.027; G9B/7.166 |
Current CPC
Class: |
G03H 1/0236 20130101;
G03H 2001/0264 20130101; G03H 2223/12 20130101; G03H 2250/37
20130101; G03H 1/26 20130101; G03H 2270/54 20130101; G03H 1/182
20130101; G11B 7/261 20130101; G11B 7/24044 20130101; G11B 7/0065
20130101; G03H 2250/33 20130101; G03H 1/02 20130101; G03H 2260/30
20130101 |
Class at
Publication: |
359/003 ;
359/015 |
International
Class: |
G03H 1/02 20060101
G03H001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2005 |
JP |
2005-272445 |
Claims
1. A holographic recording medium comprising: a holographic
material layer in which information is to be recorded by
irradiating the same region with information light corresponding to
the information to be recorded and reference light to read the
recorded information, wherein the holographic material layer is
divided into a plurality of recording zones by a plurality of light
shielding walls, and the light shielding wall is formed of a
material which does not transmit bleaching light irradiated for
fixing the recorded information to the recording zone in which a
recording process has been performed.
2. The holographic recording medium according to claim 1, wherein
the light shielding wall reflects or absorbs the bleaching light so
that the bleaching light proceeds only to a recording zone in which
the recorded information is to be fixed, and the bleaching light
does not proceed to a recording zone adjacent to the recording zone
in which the recorded information is to be fixed.
3. The holographic recording medium according to claim 1, wherein
the light shielding wall includes either acrylic or polycarbonate
material.
4. The holographic recording medium according to claim 1, wherein
the holographic material layer is formed on a disk-shaped or
polygonal substrate, the light shielding wall is formed on the
substrate and in the holographic material layer in a latticed
pattern, and the recording zone is a region surrounded by the
lattice-shaped light shielding walls.
5-6. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to Japanese Patent Application
No. 2005-272445 filed on Sep. 20, 2005, whose priority is claimed
under 35 USC .sctn. 119, the disclosure of which is incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a holographic recording
medium and, more particularly, to a holographic recording medium in
which a fixing process is performed by applying bleaching light in
order to fix holographic recorded data in the medium.
[0004] 2. Description of the Related Art
[0005] As a medium in which large-capacity information can be
recorded at high density, there is a holographic recording medium.
In the holographic recording medium, page data having capacity of
several hundreds of megabytes can multiplex-recorded in the same
region. The holographic recording is such that a light beam from a
single light source is separated to reference light and information
light and the same position on the recording medium is irradiated
with the reference light and the information light and an
irradiation angle or a wavelength of the reference light is varied
to generate different interferences, so that different information
is recorded in the same position on the recording medium in
piles.
[0006] The region in which information is recorded by the
holographic recording is a region having a three-dimensional
thickness and its optical characteristics are varied even when weak
light such as a fluorescent lamp in a room is applied, depending on
its material. When the optical characteristics are varied, a
reproduction error could be generated. Thus, a medium in which a
holographic recording medium is housed in a cartridge or a medium
in which a light shielding layer is provided on a holographic
recording layer have been proposed (refer to Japanese Unexamined
Patent Publication No. 2004-279942).
[0007] In addition, according to a holographic recording medium in
which data can be written only one time such as a CD-R, in order to
stabilize the optical characteristics, after data is recorded with
hologram, data fixing process called bleaching is performed. The
bleaching is a process such that a region in which holographic
recording has been performed is irradiated with white light
(referred to as bleaching light) having relatively high intensity
which does not destroy its recorded data.
[0008] In the recording region irradiated with the bleaching light,
reactivity of the recording material is fixed and its optical
characteristics are not varied by weak light such as a fluorescent
lamp, so that the recorded data can be stably reproduced.
[0009] FIGS. 21 and 22 show a schematic constitution of a
conventional holographic recording medium. FIG. 21 is a sectional
view showing the medium and FIG. 22 is a plan view showing a
substrate constitution.
[0010] As shown in FIGS. 21 and 22, the holographic recording
medium has a constitution in which a resin substrate 12 and a
holographic material layer 13 are sandwiched between two glass
substrates 10 (10-1, 10-2). The resin substrate 12 includes a
reflection film 11 at a boundary with one of the glass substrates
10-1.
[0011] When the reference light and the information light are
applied at the same time from an upper part of the glass substrate
10-2 of the medium, data is recorded in a region of the holographic
material layer 13. After the data is recorded, the bleaching light
is applied to fix the recorded data. Thus, the data is fixed in the
region of the holographic material layer 13 irradiated with the
bleaching light.
[0012] FIGS. 23A and 23B show a schematic explanatory diagram of
the conventional medium when the bleaching light is applied.
[0013] As shown in FIGS. 23A and 23B, when the bleaching light 15
proceeds into the recording region of the holographic material
layer 13, it is diffused and diffracted. The bleaching light
proceeds to its adjacent region 17 by diffusion and diffraction
besides a light beam proceeding to the intended irradiation region
16. As a result, data recorded in the regions (16 and 17) to which
the bleaching light 15 proceeded is fixed.
[0014] However, when the data is fixed by the bleaching light in
the conventional holographic medium, there are following
problems.
[0015] As shown in FIG. 24, it is assumed that a holographic
recording completed region 18 and an unrecorded region 19 are
adjacent to each other in the holographic material layer 13. Here,
according to the holographic recording completed region 18, it is
assumed that data recording with the information light and the
reference light has been completed but the bleaching light is not
applied yet.
[0016] According to the unrecorded region 19, it is assumed that
data has not been recorded yet.
[0017] As shown in FIG. 25, it is assumed that the bleaching light
15 is applied to the medium in this state to fix the data of the
recording completed region 18. At this time, the data can be fixed
as intended in the recording completed region 18 which is apart
from the unrecorded region 19. However, when the bleaching light 15
is applied to a boundary region with the region 19, since the
holographic material layer 13 has a thickness in the vertical
direction, it is diffused and diffracted as shown in FIGS. 23A and
23B, so that the bleaching light proceeds beyond a boundary 20.
That is, the bleaching light 15 proceeds to regions 16 and 17 and
the region 17 irradiated with the bleaching light is spread to the
left side of the boundary 20 in FIG. 25.
[0018] As a result, as shown in FIG. 26, the data in the unrecorded
region 19 in the vicinity of the boundary is also fixed in addition
to the data of the intended recording completed region 18. A region
21 shown in FIG. 26 is the data fixed region. That is, although the
region 19 is to be used for recording data in the future, since
unintended fixing process was performed, the holographic recording
cannot be performed any more in that region 19.
[0019] Alternatively, in the fixed region in the unrecorded region
19, its diffraction efficiency is extremely lowered and even if the
recording and reproducing can be performed thereafter, SNR at the
time of recording and reproducing deteriorates.
[0020] As described above, when the bleaching process is performed
in the conventional holographic recording medium, recording and
reproducing characteristics deteriorate and recording capacity is
reduced in the boundary region of the recording completed
region.
[0021] In addition, data is managed by logical and physical
addresses in a conventional storage. Since the logical address and
the physical address are related at an initial stage, when the
unrecorded region becomes a region in which data cannot be
recorded, performance is considerably lowered because of its
recording error or frequent occurrence of alternating processes.
Thus, in the case of the medium in which recording capacity is
varied, it is necessary to develop a data management method which
is different from the conventional method.
SUMMARY OF THE INVENTION
[0022] The present invention provides a holographic recording
medium including a holographic material layer in which information
is to be recorded by irradiating the same region with information
light corresponding to the information to be recorded and reference
light to read the recorded information, wherein the holographic
material layer is divided into a plurality of recording zones by a
plurality of light shielding walls, and the light shielding wall is
formed of a material which does not transmit bleaching light
irradiated for being fixed the recorded information to the
recording zone in which a recording process has been performed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIGS. 1A and 1B are sectional views each showing a
holographic recording medium according to one embodiment of the
present invention;
[0024] FIG. 2 is a plan view showing the holographic recording
medium according to one embodiment of the present invention;
[0025] FIG. 3 is a plan view showing a holographic recording medium
according to one embodiment of the present invention;
[0026] FIG. 4 is a plan view showing a holographic recording medium
according to one embodiment of the present invention;
[0027] FIGS. 5A and 5B are sectional views each showing a
holographic recording medium according to one embodiment of the
present invention;
[0028] FIG. 6 is a perspective view showing the holographic
recording medium according to one embodiment of the present
invention;
[0029] FIG. 7 is a plan view showing a holographic recording medium
according to one embodiment of the present invention;
[0030] FIG. 8 is a plan view showing a holographic recording medium
according to one embodiment of the present invention;
[0031] FIG. 9 is a plan view showing a holographic recording medium
according to one embodiment of the present invention;
[0032] FIGS. 10A and 10B are sectional views each showing a
holographic recording medium according to one embodiment of the
present invention;
[0033] FIGS. 11A and 11B are sectional views each showing a
holographic recording medium according to one embodiment of the
present invention;
[0034] FIGS. 12A and 12B are sectional views each showing a
holographic recording medium according to one embodiment of the
present invention;
[0035] FIG. 13 is an explanatory diagram showing an embodiment of
multiplex recording of holographic data according to the present
invention;
[0036] FIG. 14 is an explanatory diagram showing a prohibited
embodiment of multiplex recording of holographic data according to
the present invention;
[0037] FIG. 15 is a flowchart showing a recording process and a
bleaching process according to the present invention;
[0038] FIG. 16 is an explanatory diagram of bleaching of a
recording zone according to the present invention;
[0039] FIG. 17 is an explanatory diagram of bleaching of a
recording zone according to the present invention;
[0040] FIG. 18 is an explanatory view showing a manufacturing
method of a holographic recording medium according to the present
invention;
[0041] FIG. 19 is an explanatory view showing the manufacturing
method of the holographic recording medium according to the present
invention;
[0042] FIGS. 20A and 20B are explanatory views each showing the
manufacturing method of the holographic recording medium according
to the present invention;
[0043] FIG. 21 is a sectional view showing a conventional
holographic recording medium;
[0044] FIG. 22 is an explanatory view showing a constitution of the
conventional holographic recording medium;
[0045] FIGS. 23A and 23B are explanatory views each showing
bleaching light in the conventional holographic recording
medium;
[0046] FIG. 24 is an explanatory view showing a recording region of
the conventional holographic recording medium;
[0047] FIG. 25 is an explanatory view showing proceeding of the
bleaching light of the conventional holographic recording medium;
and
[0048] FIG. 26 is an explanatory view showing a fixed region of the
conventional holographic recording medium.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] The present invention is a holographic recording medium in
which bleaching light can be prevented from proceeding to an
unintended holographic recording region.
[0050] The present invention provides a holographic recording
medium including a holographic material layer in which information
is to be recorded by irradiating the same region with information
light corresponding to the information to be recorded and reference
light to read the recorded information, wherein the holographic
material layer is divided into a plurality of recording zones by a
plurality of light shielding walls, and the light shielding wall is
formed of a material which does not transmit bleaching light to be
applied to the recording zone in which a recording process has been
performed and the recorded information is to be fixed.
[0051] Preferably, the light shielding wall reflects or absorbs the
bleaching light so that the bleaching light proceeds only to a
recording zone in which the recorded information is to be fixed,
and the bleaching light does not proceed to a recording zone
adjacent to the recording zone in which the recorded information is
to be fixed.
[0052] Herein, the light shielding wall may include either acrylic
or polycarbonate material.
[0053] Preferably, the holographic material layer is formed on a
disk-shaped or polygonal substrate, the light shielding wall is
formed on the substrate and in the holographic material layer in a
latticed pattern, and the recording zone is a region surrounded by
the lattice-shaped light shielding walls. Herein, examples of the
substrate may include a glass substrate, a resin substrate and the
like.
[0054] The substrate may be a laminated substrate formed by
laminating various types of substrates. In the later-described
embodiment, a structure including a glass substrate and a resin
substrate provided with a reflection film is described as one
example of the substrate (refer to FIG. 1).
[0055] Preferably, the holographic material layer is formed on a
disk-shaped or polygonal substrate, the light shielding wall is
formed on the substrate and in the holographic material layer, a
waveguide layer to introduce the bleaching light is provided
between the substrate and the holographic material layer, and the
waveguide layer is formed so that the applied bleaching light is
led to each recording zone of the holographic material layer.
[0056] Preferably, the holographic recording medium includes a
light shielding member provided on the holographic material layer
and the light shielding wall, and the light shielding member is any
one of a thin film which can be removed from/attached to each
recording zone, a movable member which can control permission and
prohibition of light proceeding to the holographic material layer
in each recording zone, and a liquid crystal element which can vary
light transmission to the holographic material layer in each
recording zone.
[0057] An embodiment of the present invention will be described
with reference to the drawings hereinafter. In addition, the
present invention is not limited to the embodiment.
(Structure of Holographic Recording Medium)
[0058] FIGS. 1A and 1B are sectional views each showing a
holographic recording medium according to one embodiment of the
present invention.
[0059] Referring to FIGS. 1A and 1B, the medium according to the
present invention includes a holographic material layer 33 and a
light shielding wall 34 on a laminated structure in which a glass
substrate 30, a reflection film 31, and a resin substrate 32 are
laminated in this order.
[0060] The above medium is different from the conventional medium
shown in FIG. 21 in that it includes the light shielding walls 34.
The light shielding walls 34 are provided in the holographic
material layer 33 at regular intervals (about several millimeters,
for example) so as to divide the holographic material layer 33 into
a plurality of regions (referred to as a recording zone or a zone
simply hereinafter).
[0061] The holographic recording is volume recording and the
holographic material layer 33 has a thickness of about several
millimeters in general, in which information is multiplex-recorded.
However, its thickness depends on its specification.
[0062] The multiplex recording is performed with information light
and reference light outputted from a single light source and split
by a beam splitter. The information light is light corresponding to
information to be recorded and it is modulated by a special light
modulator (SLM) having two-dimensional special information
corresponding to the information to be recorded.
[0063] Although the reference light is used for reading recorded
information, at the time of recording, it is also used for
recording the information in the holographic material layer 33 by
interference with the information light applied to the same
region.
[0064] In a recording process, the information to be recorded is
recorded as two-dimensional page data when the information light
and the reference light are applied to the same region of the
holographic material layer.
[0065] In addition, when the reference light whose angle is varied
is applied to the same region in which the data has been recorded,
multiplex recording of plural pieces of two-dimensional page data
can be performed, for example.
[0066] In addition, this medium according to the present invention
is a so-called write-once medium which is fixed by bleaching
(fixing process) so that recorded data is not erased and not varied
due to a chemical reaction.
[0067] FIG. 1A shows a state in which the holographic material
layer 33 is divided into three recording zones (A, B and C) by the
light shielding walls 34. FIG. 3 is a plan view showing the
holographic material layer taken from above in FIGS. 1A and 1B.
[0068] For example, when information is recorded in the zone B,
reference light and information light outputted from a single light
source are applied to the zone B and plural pieces of information
are multiplex-recorded in the holographic material layer 33 of the
zone B by varying an irradiation angle of the reference light.
[0069] The light shielding wall 34 does not transmit bleaching
light 15 and it is formed of a material which does not transmit the
bleaching light 15, so that the bleaching light 15 does not proceed
to the adjacent recording zone. The bleaching light 15 is to fix
the already recorded information in the recording zone.
[0070] For example, when the zone B shown in FIG. 1B is irradiated
with the bleaching light 15, the bleaching light 15 reflects when
it meets the light shielding wall 34 or it is absorbed by the light
shielding wall 34, so that it does not enter the zone A which is
the adjacent region.
[0071] In the case of FIG. 1B, although the bleaching light 15 is
diffused in the zone B in a left direction, it does not enter the
zone A on the right side of the light shielding wall 34 because of
the light shielding wall 34.
[0072] Thus, the light shielding wall 34 which does not transmit
the bleaching light 15 is made of a colored acrylic resin, for
example.
[0073] In addition, the light shielding wall may be made by mixing
a material such as carbon graphite to the above and coloring the
mixture, thereby transmitting no bleaching light. In general, when
it absorbs the bleaching light, the color is preferably black.
[0074] In addition, the holographic material layer 33 is formed of
a material mainly containing (meta)acrylate, styrene, vinyl ether,
epoxy and the like. Depending on its material, a chemical reaction
generated when the bleaching light is applied could be spread in
the region to which the bleaching light does not directly
proceed.
[0075] That is, diffusion could occur in the fixed region due to
the chemical reaction of the holographic material layer 33 other
than the diffusion in the fixed region due to scattering or
diffraction of the bleaching light as shown in FIGS. 23A and
23B.
[0076] Thus, it is preferable that the light shielding wall 34 has
a property (which is inactive to the chemical reaction) to prevent
the fixed region from being diffused by the chemical reaction. For
example, the acrylic resin or polycarbonate is inactive to the
chemical reaction.
[0077] In FIGS. 1A and 1B, the substrate 30, the reflection film 31
and the resin substrate 32 may be formed of the same material as in
the conventional medium shown in FIG. 21.
[0078] In addition, although it is not shown in FIGS. 1A and 1B, a
glass substrate may be provided on the holographic material layer
33 as shown in FIG. 21.
[0079] When it is assumed that the zone B is a recording completed
region and the zone A is an unrecorded region in FIG. 1B, the zone
B is irradiated with the bleaching light 15 to fix the recorded
data in the zone B. At this time, although the bleaching light 15
is diffused in the right and left direction in the zone B, it is
prevented from further being diffused in the right direction by the
light shielding wall 34, so that the bleaching light 15 is not
diffused in the zone A as the unrecorded region.
[0080] Therefore, the unrecorded region (zone A) is prevented from
being fixed by mistake. Then, when data is recorded in the
unrecorded region (zone A), the data can be recorded in good SNR.
That is, good recording and reproducing characteristics of the
unrecorded region can be assured and recording capacity in which
stable recording and reproducing can be performed as designed can
be assured.
[0081] Meanwhile, the medium shown in FIG. 3 according to the
present invention is a polygonal (rectangular in FIG. 3)
card-shaped medium, and in order to fix the data in a certain
recording zone; it is necessary to control a position of an optical
component so that the bleaching light 15 is applied only to that
recording zone. In general, the recording and reproducing device to
perform a recording process and a reproducing process in the
holographic material layer mainly includes optical components such
as a light source, a beam splitter, a special light modulator
(SLM), an objective lens, and a photodetector (CCD), so that it is
necessary to provide a position adjusting mechanism (actuator) for
relative alignment between each recording zone and a light source
of the bleaching light when the medium according to the present
invention is bleached. The light source of the bleaching light may
be separately provided from the light source of the reference light
and the like.
[0082] In addition, in the recording process with the reference
light and the information light, it is also necessary to control
the position of the optical component so that only one recording
zone is irradiated with a recording spot as will be described below
(refer to FIG. 13).
(Construction Example of Holographic Recording Medium)
[0083] FIG. 2 and the like show a plan view and a sectional view
showing a holographic recording medium according to an embodiment
of the present invention.
[0084] The medium shown in FIG. 2 is a disk-shaped rotation medium,
in which light shielding walls 34 are provided at regular intervals
concentrically and a holographic material layer 33 is provided
between them. In this case, the donut-shaped region between the
concentrically adjacent light shielding walls 34 is one recording
zone. In addition, the intervals between the light shielding walls
34 may be the same or may be different.
[0085] A medium shown in FIG. 4 is a rectangular card-shaped medium
similar to FIG. 3, and lattice-shaped light shielding walls 34 are
formed in a holographic material layer 33. In this case, the
rectangular region surrounded by the lattice-shaped light shielding
walls 34 serves as one recording zone.
[0086] A medium shown in FIG. 5 is a medium in which a waveguide
layer 35 is added to the medium shown in FIG. 1. The waveguide
layer 35 is provided between a resin substrate 32 and a holographic
material layer 33. The waveguide layer 35 transmits the bleaching
light and leads it to the holographic material layer 33, and it is
formed of a material such as transparent acrylic material or olepin
material. The bleaching light 15 is introduced into the waveguide
layer 35.
[0087] FIG. 6 is a perspective view showing the medium shown in
FIGS. 5A and 5B, and arrows show proceeding directions of bleaching
lights 15-A, 15-B and 15-C. Each bleaching light 15 is inputted
into a side face of the waveguide layer 35 of each recording zone.
For example, when the information recorded in the zone C is to be
fixed, the bleaching light 15-C is inputted to the side face of the
waveguide layer of the zone C.
[0088] The inputted bleaching light 15-C proceeds into the
waveguide layer 35 and also proceeds to the upper holographic
material layer 33 by scattering and reflection. The holographic
recorded data in the zone is fixed by this upward bleaching light
15.
[0089] FIG. 5B shows that the bleaching light 15-B proceeds upward
in the zone B. Here, although the, bleaching light 15-B is diffused
in the zone B, it does not proceed to the adjacent zone A because
the light shielding wall 34 exists in the right side.
[0090] Therefore, when it is assumed that the zone B is a recording
completed region and the zone A is an unrecorded region in FIGS. 5A
and 5B, the recorded data in the zone B is fixed by the bleaching
light 15-B and the zone A is prevented from being fixed because the
bleaching light does not proceed to the adjacent zone A in which
data is not recorded.
[0091] A medium shown in FIG. 7 is a disk-shaped rotation medium
which includes a waveguide layer 35 like in FIGS. 5A and 5B. In
this case, the waveguide layer 35 is formed under each recording
zone of a donut-shaped holographic material layer 33 and separated
by a light shielding wall 34 every recording zone. In addition, the
bleaching light 15 is inputted from an inlet 25 provided on a side
face of the medium. For example, the inlet 25 is provided in each
zone and a waveguide to connect each inlet to each zone optically
is provided. The bleaching light inputted to the inlet 25 passes
through the waveguide layer 35 connected to the inlet and it is led
to the connected recording zone.
[0092] A medium shown in FIG. 8 is a disk-shaped medium and
includes an inlet 25 for each zone, to which the bleaching light 15
is inputted from an upper part of the medium. The bleaching light
15 inputted from the inlet 25 of a certain zone is led to a
waveguide layer 35 of the zone and scattered in a holographic
material layer 33 of the zone and data recorded in the zone is
fixed. The inlet 25 may be provided under the medium on the side of
a substrate 30 instead of being provided above the medium on the
side of the holographic material layer.
[0093] A medium shown in FIG. 9 is a disk-shaped medium and
includes an inlet 25 for each zone, to which bleaching light 15 is
inputted from an upper part of the medium. FIG. 9 shows a case in
which the plural inlets are collected to one place. When the inlets
25 are enlarged, each of the small inlets (Z1 to Z12) is provided
for each zone as shown in FIG. 9. If the number of zones is 12, the
inlet Z1 is for the zone 1 and the inlet Z12 is for the zone
12.
[0094] For example, the inlet Z5 is connected to the zone 5 through
a waveguide layer 35 and data in the zone 5 is fixed by the
bleaching light inputted from the inlet Z5. The position of the
inlets 25 is not limited to a position in the vicinity of the inner
periphery as shown in FIG. 9, and it may be provided other than in
the recording zone or in the vicinity of an outer periphery of the
medium.
[0095] In this case, the recording and reproducing device has a
position adjustment mechanism to irradiate the inlet of the zone to
be fixed with the bleaching light 15.
[0096] Several embodiments for the medium including the waveguide
layer have been described. When the waveguide layer is provided,
the mechanism to adjust the irradiation position with the bleaching
light can be simplified.
[0097] According to a medium shown in FIGS. 10A and 10B, a light
shielding member 41 is provided on a holographic material layer 33.
The light shielding member 41 prevents the holographic material
layer 33 from causing a chemical reaction due to external light
such as a fluorescent lamp while the medium is stored and the like,
and it may be formed of an acrylic material or a polycarbonate
material.
[0098] Alternatively, it is preferable that a thin film which can
be removed from/attached to each recording zone is used so that a
recording process and a fixing process can be performed in each
recording zone.
[0099] Fig. 10A shows a state when the medium is shipped. For
example, the thin film (light shielding member) 41 which covers the
holographic material layer 33 is attached to each recording zone.
Thus, the holographic material layer 33 can be protected while it
is stored.
[0100] FIG. 10B shows a state at the time of recording process and
at the time of fixing process by the bleaching light. In this case,
after the light shielding thin film 41 is removed from the zone B
in which the data is to be recorded or fixed, for example, the zone
B is irradiated with information light and reference light.
Alternatively, the fixing process is performed in the zone B by
irradiation of the bleaching light. After the fixing process by the
bleaching light, since the data is fixed and not erased, it is not
necessary to attach the light shielding thin film 41 again. In this
case, a tool or a mechanism to remove the light shielding thin film
41 is needed.
[0101] FIGS. 11A and 11B show a medium in which a light shielding
member 41 is provided on a holographic material layer 33 in each
zone like in FIGS. 10A and 10B as a slidable member so that the
zone can be opened or closed. Since the slidable member 41 is
provided every recording zone, the light is permitted to proceed or
prohibited from proceeding to the holographic material layer in
each recording zone.
[0102] The light shielding members (41A, 41B and 41C) can be slid
in the right and left direction of the drawing. When the light
shielding member 41B of the zone B to be irradiated with the light
is slid, for example, the light can be transmitted to the
holographic material layer 33 of the zone B. In this case, it is
necessary to provide a mechanism to slide the light shielding
member 41 in each zone.
[0103] FIG. 11A shows a state in which the medium is shipped and
FIG. 11B shows a state in which the recording process or the fixing
process is performed to the zone B.
[0104] FIGS. 12A and 12B show an embodiment in which a liquid
crystal element 42 is used for a light shielding member 41. The
liquid crystal element 42 varies light transmission to a
holographic material layer in each recording zone. That is, it
controls shielding and transmitting of the reference light or the
bleaching light. Therefore, it is necessary to provide a mechanism
to drive the liquid crystal element 42.
[0105] FIG. 12A shows a state in which the medium is shipped and
the liquid crystal element 42 stably shields the light. FIG. 12B
shows a state in which the liquid crystal element 42 in a zone B is
driven to transmit the light to the zone B.
[0106] The embodiments in which the light shielding member 41 is
provided on the holographic material layer 33 have been described.
In this case, since the light shielding member 41 is provided, in
addition to the effect that the bleaching light is prevented from
being diffused to the unrecorded region by the light shielding wall
34, a chemical reaction of the holographic material layer due to
external light can be prevented at the time of storage.
(Recording Process and Bleaching Process According to the Present
Invention)
[0107] FIG. 15 shows a schematic flowchart of the recording process
and the bleaching process according to the present invention.
[0108] In a case the holographic recording medium according to the
present invention is a transportable medium like a conventional
CD-ROM or DVD-R, when the medium according to the present invention
is inserted into the recording and reproducing device and a
recording command is transferred to the recording and reproducing
device from a higher-order device such as a personal computer
connected to the recording and reproducing device, a recording
process is started.
[0109] The flowchart shown in FIG. 15 shows details of the process
in the recording and reproducing device.
[0110] This recording process is executed by a microcomputer having
a CPU and the like mounted on the recording and reproducing
device.
[0111] It is determined whether the recording command is provided
from the higher-order device or not in step S1 in FIG. 15 and if
the command is not provided, the step S1 is repeated. When the
recording command of data is provided, the operation proceeds to
step S2 where information (address, data to be recorded and the
like) contained in the command is examined and a predetermined
recording process is performed in the holographic recording
medium.
[0112] Although the recording to the holographic recording medium
has a feature in that multiplex recording is performed to a
two-dimensional region in general, a method of performing multiplex
recording to the same physical region includes an angle multiplex
method or a shift multiplex method. For example, according to the
shift multiplex method, while a part of a prior recording spot and
a part of the next recording spot are overlapped, the recording is
performed, shifting the recording spot sequentially.
[0113] According to the present invention, when the recording spot
is shifted, the position of the recording spot is controlled so
that it may be shifted within one recording zone and it may not be
shifted beyond the recording zone.
[0114] In other words, the position of the optical component for
recording is controlled so that the reference light or the
information light may not proceed to the adjacent zone beyond the
light shielding wall 34 according to the present invention.
[0115] FIG. 13 shows an embodiment of a movement range of the
recording spot in the shift multiplex method according to the
present invention.
[0116] Here, one circle corresponds to the recording spot and the
recording spot can be moved around in one zone only.
[0117] FIG. 14 shows a recording method which is not employed in
the present invention. That is, the position of the recording spot
is controlled so that the recording spot may not extend across the
light shielding wall 34 between adjacent zones.
[0118] When the recording spot is controlled as shown in FIG. 13,
data is prevented from being recorded in the adjacent zone to which
data is not to be recorded. In addition, in the bleaching process
as will be described below, the position of the light spot of the
bleaching light is also controlled like in FIG. 13.
[0119] The recording process in step S2 may be almost the same as
the recording process in the conventional holographic material
layer.
[0120] For example, the following processes are sequentially
performed:
[0121] (1) a process for physically moving a component for
recording, in which a position of the recording component is
controlled so that a physical position of the medium indicated by
the recording command may be irradiated with the recording
spot,
[0122] (2) a process for preparing a recording process, in which an
encoding process and the like is performed to the data to be
recorded so that the data is converted to a form to be recorded in
the medium actually,
[0123] (3) a holographic recording process in which the reference
light and the information light are applied to a predetermined
position of the medium,
[0124] (4) a verifying process or a rewriting process to confirm
whether the recording is performed normally or not, and
[0125] (5) a process such as a completion noticing process to
inform the higher-order device of the completion of the commanded
recording.
[0126] However, according to the present invention, in the media
shown in FIGS. 10A, 10B, 11A, 11B and 12A, 12B, the light shielding
member is controlled as shown in FIGS. 10B, 11B and 12B in the
preparing process (2) among the above series of processes so that
the holographic material layer 33 of the zone in which data is to
be recorded may be irradiated with the light. For example,
according to the medium shown in FIG. 11, when the zone B is the
recording region, the light shielding member 41B which covers the
zone B is slid in the right direction.
[0127] It is determined whether the bleaching is to be performed or
not in step S3 in FIG. 15.
[0128] When it is not, the operation is returned to the step S1.
When the bleaching is to be performed, the operation proceeds to
step S4.
[0129] The case it is determined that the bleaching is to be
performed is as follows:
[0130] (a) a case the holographic recording medium is changed
according to a specific operation of a user,
[0131] (b) a case a bleaching command for a specific recording zone
is received from the higher-order device by an input of the user,
and
[0132] (c) a case a zone runs out of free space as a result of
confirming the present recorded capacity in each zone, or a case
remaining capacity is less than a predetermined value (remaining
capacity <recorded capacity.times.1%, for example).
[0133] Although the present invention is not limited to the above
three cases, when any case among the three cases is generated, the
bleaching process s performed in step S4.
[0134] FIGS. 16 and 17 are views to explain an embodiment in which
the bleaching process is to be performed.
[0135] FIG. 16 shows a case the multiplex recording process have
been carried out eight times for one zone and entire capacity in
the zone is used and recording cannot be performed any more. In
this case, it is confirmed that the entire zone is used, so that
the bleaching process for the entire zone, that is, the fixing
process for the recorded data is performed.
[0136] FIG. 17 shows a case the bleaching process is performed by a
bleaching command from the user although there is still free
capacity (empty region) in the zone. After the bleaching process,
data cannot be recorded in the empty region any more.
[0137] In step S4 shown in FIG. 15, the target recording zone of
the medium is irradiated with the bleaching light as shown in FIG.
1B or FIG. 23 to perform the bleaching process.
[0138] Here, as described in FIGS. 1B, 5B and 13, the position of
the optical component of the recording and reproducing device is
controlled so that only the recording zone in which the data is to
be fixed is irradiated with the bleaching light and the adjacent
zone is not irradiated with the bleaching light.
[0139] Since the holographic recording medium according to the
present invention includes the light shielding wall 34 shown in
FIG. 1, when the recording process and the bleaching process are
performed as shown in FIG. 15, the light for the recording process
or the bleaching light is not diffused in the unrecorded region, so
that the recording and reproducing SNR can be improved and more
stable recording and reproducing characteristics are
implemented.
(Embodiment of Manufacturing Method of the Medium According to the
Present Invention)
[0140] The same manufacturing method as the conventional method may
be used for the holographic recording medium according to the
present invention except for a step of providing the light
shielding wall 34.
[0141] For example, the resin substrate 32 provided with the
reflection film 31 is manufactured by spattering the reflection
film 31 formed of a material such as aluminum or aluminum chrome or
silver to the entire of the resin substrate 32 formed of acrylic
material.
[0142] Then, as shown in FIG. 1, the substrate 30 formed of glass
or polycarbonate is prepared and the substrate 30 and the resin
substrate 32 are adhered to each other through an adhesive such as
UV cure resin and the like.
[0143] Then, as shown in FIG. 18, a stamper in which a recessed
pattern is provided to form the long and thin light shielding
member corresponding to the light shielding wall 34 is prepared and
a colored acrylic resin is applied to the recessed pattern surface
of the stamper and stretched by a spin coating or blade method, to
form the light shielding member corresponding to the light
shielding wall 34 on the stamper. Then, a surface of the light
shielding member on the stamper and the face of the substrate 32
provided with the reflection film and the substrate 30 are opposed
and adhered by an anaerobic adhesive or a UV combined anaerobic
adhesive or the like.
[0144] Then, as shown in FIG. 19, when the light shielding member
is removed from the stamper, the structure in which the light
shielding wall 34 is formed on the substrate 32 can be
provided.
[0145] Then, as shown in FIG. 20A, the holographic material 33
which is semisolid or has viscosity such as (meta)acrylate,
styrene, vinyl ether, epoxy and the like is poured into the zones
A, B and C shown in FIGS. 1A and 1B. Thus, the holographic
recording medium shown in FIG. 1A is completed (refer to FIG. 20B).
However, this manufacturing method is an example and the present
invention is not limited to this.
[0146] In addition, as shown in FIGS. 5A and 5B, when the waveguide
layer 35 is formed, before the light shielding wall 34 is formed, a
transparent material such as acrylic or olepin material is applied
to the surface of the substrate 32 to form the waveguide layer.
[0147] According to the present invention, since the holographic
material layer is divided into the plurality of recording zones by
the light shielding walls which do not transmit the bleaching
light, the bleaching light applied to a certain recording zone can
be prevented from being diffused or proceeding to its adjacent
recording zone.
[0148] In addition, when the adjacent recording zone is an
unrecorded region, the bleaching light is not diffused in that
unrecorded region. Thus, when data is recorded in the unrecorded
region in the future, the SNR at the time of recording and
reproducing is improved and substantial recording and reproducing
characteristics can be improved. Furthermore, the substantially
intended recording capacity can be assured and the same data
management method as in the conventional storage can be
employed.
* * * * *