U.S. patent application number 10/583604 was filed with the patent office on 2007-08-09 for holographic multiplex recording method, and holographic recording apparatus and holographic recording medium employing the method.
This patent application is currently assigned to TDK Corporation. Invention is credited to Hideaki Miura, Tetsuro Mizushima, Takuya Tsukagoshi, Jiro Yoshinari.
Application Number | 20070183009 10/583604 |
Document ID | / |
Family ID | 34746888 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070183009 |
Kind Code |
A1 |
Tsukagoshi; Takuya ; et
al. |
August 9, 2007 |
Holographic multiplex recording method, and holographic recording
apparatus and holographic recording medium employing the method
Abstract
A holographic multiplex recording method which can keep a
recording data rate constant and equalize nonuniformity in
recording due to vibrations or the like, and a holographic
recording apparatus and a holographic recording medium, which
employ the method are provided. In a process of multiplex-recording
information, the time of exposure to a laser beam per data page is
kept constant, and the laser output power of the laser beam is
increased in accordance with a decrease in recording sensitivity of
the holographic recording medium.
Inventors: |
Tsukagoshi; Takuya;
(Kanagawa, JP) ; Yoshinari; Jiro; (Tokyo, JP)
; Miura; Hideaki; (Tokyo, JP) ; Mizushima;
Tetsuro; (Oosaka, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TDK Corporation
1-13-1, Nihonbashi, Chuo-ku
Tokyo
JP
103-8272
|
Family ID: |
34746888 |
Appl. No.: |
10/583604 |
Filed: |
December 6, 2004 |
PCT Filed: |
December 6, 2004 |
PCT NO: |
PCT/JP04/18165 |
371 Date: |
June 20, 2006 |
Current U.S.
Class: |
359/10 ;
G9B/7.027; G9B/7.105 |
Current CPC
Class: |
G03H 1/28 20130101; G11B
7/083 20130101; G11B 7/128 20130101; G03H 1/265 20130101; G11B
7/0065 20130101 |
Class at
Publication: |
359/010 |
International
Class: |
G03H 1/10 20060101
G03H001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2003 |
JP |
2003-434319 |
Claims
1. A holographic multiplex recording method for multiplex-recording
information as a hologram on a holographic recording medium using
interference fringes of an object beam and a reference beam, into
which a laser beam is split, wherein in a process of
multiplex-recording the information, a time of exposure to the
laser beam per data page is kept constant, and a laser output power
of the laser beam is increased in accordance with a decrease in
recording sensitivity of the holographic recording medium.
2. A holographic multiplex recording method for multiplex-recording
information as a hologram on a holographic recording medium using
interference fringes of an object beam and a reference beam, into
which a laser beam is split, wherein in a process of
multiplex-recording the information, a time of exposure to the
laser beam per data page and a laser output power are kept
constant, and a spatial light modulator having a plurality of
pixels for intensity modulating of the object beam is used to
increase the number of pixels of the spatial light modulator to be
allocated to one bit of the information in accordance with a
decrease in recording sensitivity of the holographic recording
medium.
3. The holographic multiplex recording method according to claim 2,
wherein an array of pixels of the spatial light modulator to be
allocated to one bit of the information is formed in a square grid
shape.
4. The holographic multiplex recording method according to claim 2,
wherein, when a recording sensitivity of the holographic recording
medium is reduced to less than or equal to 1/N.sup.2 (N is an
integer equal to two or greater) of an initial value of the
recording sensitivity, the number of pixels of the spatial light
modulator to be allocated to one bit of the information is
increased to N.sup.2.
5. A holographic recording apparatus for multiplex-recording
information as a hologram on a holographic recording medium using
interference fringes of an object beam and a reference beam, into
which a laser beam is split, wherein in a process of
multiplex-recording the information, a time of exposure to the
laser beam per data page is kept constant, and a laser output power
of the laser beam can be increased in accordance with a decrease in
recording sensitivity of the holographic recording medium.
6. A holographic recording apparatus for multiplex-recording
information as a hologram on a holographic recording medium using
interference fringes of an object beam and a reference beam, into
which a laser beam is split, includes a spatial light modulator
having a plurality of pixels for intensity modulating of the object
beam, and wherein in a process of multiplex-recording the
information, a time of exposure to the laser beam per data page and
a laser output power are kept constant, and the number of pixels of
the spatial light modulator to be allocated to one bit of the
information is set to increase in accordance with a decrease in
recording sensitivity of the holographic recording medium.
7. The holographic recording apparatus according to claim 6,
wherein an array of pixels of the spatial light modulator to be
allocated to one bit of the information is formed in a square grid
shape.
8. The holographic recording method according to claim 6, wherein
the number of pixels of the spatial light modulator to be allocated
to one bit of the information is set to increase to N.sup.2 when a
recording sensitivity of the holographic recording medium is
reduced to less than or equal to 1/N.sup.2 (N is an integer equal
to two or greater) of an initial value of the recording
sensitivity.
9. A holographic recording medium on which information is multiplex
recorded as a hologram using interference fringes of an object beam
and a reference beam, into which a laser beam is split, wherein a
time of exposure to the laser beam and a laser output power are
kept constant, and a spatial light modulator having a plurality of
pixels for intensity modulation of the object beam is used to
increase the number of pixels of the spatial light modulator to be
allocated to one bit of the information in accordance with a
decrease in recording sensitivity of the holographic recording
medium, thereby allowing the information to be
multiplex-recorded.
10. The holographic recording medium according to claim 9, wherein
an array of pixels of the spatial light modulator to be allocated
to one bit of the information is formed in a square grid shape,
thereby allowing the information to be multiplex-recorded.
11. The holographic recording medium according to claim 9, wherein,
when a recording sensitivity of the holographic recording medium is
reduced to less than or equal to 1/N.sup.2 (N is an integer equal
to two or greater) of an initial value of the recording
sensitivity, the number of pixels of the spatial light modulator to
be allocated to one bit of the information is increased to N.sup.2,
thereby allowing the information to be multiplex-recorded.
12. The holographic multiplex recording method according to claim
3, wherein, when a recording sensitivity of the holographic
recording medium is reduced to less than or equal to 1/N.sup.2 (N
is an integer equal to two or greater) of an initial value of the
recording sensitivity, the number of pixels of the spatial light
modulator to be allocated to one bit of the information is
increased to N.sup.2.
13. The holographic recording method according to claim 7, wherein
the number of pixels of the spatial light modulator to be allocated
to one bit of the information is set to increase to N.sup.2 when a
recording sensitivity of the holographic recording medium is
reduced to less than or equal to 1/N.sup.2 (N is an integer equal
to two or greater) of an initial value of the recording
sensitivity.
14. The holographic recording medium according to claim 10,
wherein, when a recording sensitivity of the holographic recording
medium is reduced to less than or equal to 1/N.sup.2 (N is an
integer equal to two or greater) of an initial value of the
recording sensitivity, the number of pixels of the spatial light
modulator to be allocated to one bit of the information is
increased to N.sup.2, thereby allowing the information to be
multiplex-recorded.
Description
TECHNICAL FIELD
[0001] The present invention relates to a holographic multiplex
recording method, and a holographic recording apparatus and a
holographic recording medium which employ the method.
BACKGROUND ART
[0002] As shown in FIG. 4, conventionally suggested as one of
holographic recording methods is a holographic multiplex recording
method based on angle multiplexing, in which the incident angle of
a reference beam 6 is modulated while the incident angle of an
object beam 4 is kept constant with respect to a recording layer 2A
in a holographic recording medium 2 (e.g., see Japanese Patent
Laid-Open Publication No. 2003-178460).
[0003] Note that since such angle multiplex recording allows a
number of multiplexed holograms to be provided in the same area of
a recording material, the amount of exposure for recording needs to
be increased step by step as the multiplex recording proceeds.
Thus, "scheduling of recording" is carried out to control the
amount of exposure for recording according to the history of
recording on the recording material or the residual dynamic
range.
[0004] This "scheduling of recording" will now be explained in more
detail with reference to FIG. 5. Note that FIG. 5 shows the
relationship among the amount of exposure, the refractive index
modulation degree, and the recording sensitivity for the
holographic recording medium 2, in which the maximum refractive
index modulation degree for a photosensitive material of the
holographic recording medium 2 is n1, and both the refractive index
modulation degree and the recording sensitivity are normalized to
have a maximum value of one.
[0005] For example, to record N data pages by angle multiplex
recording, the maximum refractive index modulation degree n1 is
divided into N equal parts, and the refractive index modulation
degree per data page n1/N is kept constant. However, since a
photosensitive component in the photosensitive material decreases
as the multiplex recording proceeds causing degradation in
photosensitivity (recording sensitivity) to a laser beam, the
refractive index modulation degree and the exposure time t exhibit
a nonlinear relationship. Accordingly, in order to keep the
refractive index modulation degree per data page n1/N constant, the
exposure time t needs to be varied for each data page to increase
the amount of exposure E (t) step by step.
[0006] As described above, the time t of exposure to a laser beam
had to be varied in the conventional recording scheduling.
Accordingly, this causes control to be readily complicated and the
time required for recording to vary for each data page, resulting
in inconsistency in recording data rate.
[0007] Furthermore, there is a problem with the holographic
recording that microscopic vibrations or scintillations during
recording cause blurring (nonuniformity in recording) to occur in
interference fringes. In addition, there is a problem that
different exposure times t for each data page cause such blurring
to have inconsistent effects thereby impeding proper data
readout.
DISCLOSURE OF THE INVENTION
[0008] The present invention has been made to solve the
abovementioned problems. It is therefore an object of the invention
to provide a holographic multiplex recording method which can
provide a constant recording data rate and equalize nonuniformity
in recording due to vibrations or the like, and a holographic
recording apparatus and a holographic recording medium which employ
the method.
[0009] The present inventors have conducted intensive studies and
consequently found that a holographic multiplex recording method
which can provide a constant recording data rate and equalize
nonuniformity in recording due to vibrations or the like, and a
holographic recording apparatus and a holographic recording medium
which employ the method.
[0010] In summary, the above-described objectives are achieved by
the following aspects of the present invention.
[0011] (1) A holographic multiplex recording method for
multiplex-recording information as a hologram on a holographic
recording medium using interference fringes of an object beam and a
reference beam, into which a laser beam is split, wherein in a
process of multiplex-recording the information, a time of exposure
to the laser beam per data page is kept constant, and a laser
output power of the laser beam is increased in accordance with a
decrease in recording sensitivity of the holographic recording
medium.
[0012] (2) A holographic multiplex recording method for
multiplex-recording information as a hologram on a holographic
recording medium using interference fringes of an object beam and a
reference beam, into which a laser beam is split, wherein in a
process of multiplex-recording the information, a time of exposure
to the laser beam per data page and a laser output power are kept
constant, and a spatial light modulator having a plurality of
pixels for intensity modulating of the object beam is used to
increase the number of pixels of the spatial light modulator to be
allocated to one bit of the information in accordance with a
decrease in recording sensitivity of the holographic recording
medium.
[0013] (3) The holographic multiplex recording method according to
(2), wherein an array of pixels of the spatial light modulator to
be allocated to one bit of the information is formed in a square
grid shape.
[0014] (4) The holographic multiplex recording method according to
(3) or (4), wherein, when a recording sensitivity of the
holographic recording medium is reduced to less than or equal to
1/N.sup.2 (N is an integer equal to two or greater) of an initial
value of the recording sensitivity, the number of pixels of the
spatial light modulator to be allocated to one bit of the
information is increased to N.sup.2.
[0015] (5) A holographic recording apparatus for
multiplex-recording information as a hologram on a holographic
recording medium using interference fringes of an object beam and a
reference beam, into which a laser beam is split, wherein in a
process of multiplex-recording the information, a time of exposure
to the laser beam per data page is kept constant, and a laser
output power of the laser beam can be increased in accordance with
a decrease in recording sensitivity of the holographic recording
medium.
[0016] (6) A holographic recording apparatus for
multiplex-recording information as a hologram on a holographic
recording medium using interference fringes of an object beam and a
reference beam, into which a laser beam is split, includes a
spatial light modulator having a plurality of pixels for intensity
modulating of the object beam, and wherein in a process of
multiplex-recording the information, a time of exposure to the
laser beam per data page and a laser output power are kept
constant, and the number of pixels of the spatial light modulator
to be allocated to one bit of the information is set to increase in
accordance with a decrease in recording sensitivity of the
holographic recording medium.
[0017] (7) The holographic recording apparatus according to (6),
wherein an array of pixels of the spatial light modulator to be
allocated to one bit of the information is formed in a square grid
shape.
[0018] (8) The holographic recording method according to (6) or
(7), wherein the number of pixels of the spatial light modulator to
be allocated to one bit of the information is set to increase to
N.sup.2when a recording sensitivity of the holographic recording
medium is reduced to less than or equal to 1/N.sup.2 (N is an
integer equal to two or greater) of an initial value of the
recording sensitivity.
[0019] (9) A holographic recording medium on which information is
multiplex recorded as a hologram using interference fringes of an
object beam and a reference beam, into which a laser beam is split,
wherein a time of exposure to the laser beam and a laser output
power are kept constant, and a spatial light modulator having a
plurality of pixels for intensity modulation of the object beam is
used to increase the number of pixels of the spatial light
modulator to be allocated to one bit of the information in
accordance with a decrease in recording sensitivity of the
holographic recording medium, thereby allowing the information to
be multiplex-recorded.
[0020] (10) The holographic recording medium according to (9),
wherein an array of pixels of the spatial light modulator to be
allocated to one bit of the information is formed in a square grid
shape, thereby allowing the information to be
multiplex-recorded.
[0021] (11) The holographic recording medium according to (9) or
(10), wherein, when a recording sensitivity of the holographic
recording medium is reduced to less than or equal to 1/N.sup.2 (N
is an integer equal to two or greater) of an initial value of the
recording sensitivity, the number of pixels of the spatial light
modulator to be allocated to one bit of the information is
increased to N.sup.2, thereby allowing the information to be
multiplex-recorded.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is an optical system diagram illustrating a
holographic recording apparatus to which a holographic multiplex
recording method according to a first embodiment of the present
invention is applied.
[0023] FIG. 2 is a schematic side view illustrating a process of
recording on a holographic recording medium of FIG. 1.
[0024] FIG. 3 is a schematic plan view illustrating a holographic
multiplex recording method according to a second embodiment of the
present invention.
[0025] FIG. 4 is a schematic side view illustrating how angle
multiplex recording is carried out with a conventional holographic
recording apparatus.
[0026] FIG. 5 is a graph showing the relationship among the amount
of exposure, the refractive index modulation degree, and the
recording sensitivity for a holographic recording medium.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] The present invention relates to a holographic multiplex
recording method for multiplex-recording information as a hologram
on a holographic recording medium using interference fringes of an
object beam and a reference beam, into which a laser beam is split.
In the process of multiplex-recording the information, the method
allows the time of exposure to the laser beam per data page to be
kept constant and the laser output power of the laser beam to be
increased in accordance with a decrease in recording sensitivity of
the holographic recording medium, thereby solving the
aforementioned problems.
[0028] The present invention also relates to a holographic
multiplex recording method for multiplex-recording information as a
hologram on a holographic recording medium using interference
fringes of an object beam and a reference beam, into which a laser
beam is split. In the process of multiplex-recording the
information, the method allows the time of exposure to the laser
beam per data page and the laser output power to be kept constant.
The method also allows a spatial light modulator having a plurality
of pixels for intensity modulation of the object beam to be used to
increase the number of pixels of the spatial light modulator that
are allocated to one bit of the information in accordance with a
decrease in recording sensitivity of the holographic recording
medium. This can solves the same aforementioned problems.
First Embodiment
[0029] Now, with reference to FIG. 1, a description will be given
of a holographic recording apparatus 10 to which a holographic
multiplex recording method according to a first embodiment of the
present invention is applied.
[0030] The holographic recording apparatus 10 is configured to
include: a laser beam source 12; a polarizing beam splitter 14 for
transmitting one of linear polarizations having orthogonal planes
of oscillation of a laser beam from the laser beam source 12, for
example, a p-polarized component, and for reflecting an s-polarized
component; an object optical system 18 for guiding the p-polarized
component having transmitted through the polarizing beam splitter
14 to a holographic recording medium 16; and a reference optical
system 20 for guiding the s-polarized component reflected from the
polarizing beam splitter 14 to the holographic recording medium
16.
[0031] The object optical system 18 is configured to include: a
beam expander 18A for expanding the beam diameter of the object
beam emitted from the laser beam source 12; a mirror 18B for
perpendicularly reflecting the object beam having passed through
the beam expander 18A; a spatial light modulator (hereinafter
referred to as the SLM) 18C on which the object beam having
reflected off the mirror 18B is incident; and a Fourier lens 18D
for focusing the object beam having passed through the SLM 18C into
the holographic recording medium 16.
[0032] On the other hand, the reference optical system 20 is
configured to include: a mirror 20A for reflecting an incident
reference beam toward the holographic recording medium 16; and two
angle adjustment lenses 20B and 20C, in this order from the side of
the polarizing beam splitter 14. Note that the mirror 20A is
supported by a rotation stage 22 so that the angle of reflection is
adjustable, thereby allowing the reference optical system 20 to
modulate the incident angle of the reference beam relative to the
holographic recording medium 16. That is, the angle multiplex
recording is made possible.
[0033] Now, an explanation will be given to a process for recording
information on the holographic recording medium 16 using the
holographic recording apparatus 10.
[0034] An object beam which is incident upon the object optical
system 18 is reflected by the mirror 18B, and is provided with data
in the form of intensity modulation in the SLM 18C. Thereafter, the
object beam is collected and subjected to Fourier transform of
intensity distribution by the Fourier lens 18D, and is projected
onto the holographic recording medium 16.
[0035] On the other hand, a reference beam which is incident upon
the reference optical system 20 is reflected by the mirror 20A and
then passes through the angle adjustment lenses 20B and 20C to
intersect the projected object beam within the holographic
recording medium 16.
[0036] These object and reference beams produce optical
interference in a region where both the beams intersect each other,
and the optical interference is recorded as diffraction gratings on
the holographic recording medium 16.
[0037] More specifically, multiple pieces of information are
recorded on the holographic recording medium 16 by angle multiplex
recording through the processes to be described below. Note that
the first embodiment shows an example where four data pages are
recorded on a recording layer 16A of the holographic recording
medium 16 by angle multiplex recording.
[0038] To begin with, as shown in FIG. 2(A), an object beam in a
direction orthogonal to the surface of the holographic recording
medium 16 and a reference beam at an incident angle .THETA..sub.1
relative to the object beam are projected onto the holographic
recording medium 16 to form the interference fringes of the two
beams, thereby recording the first data page.
[0039] Then, the laser output power of the laser beam (the object
beam and the reference beam) is increased in accordance with a
decrease in recording sensitivity of the holographic recording
medium 16. Then, as shown in FIG. 2(B), with the object beam kept
unchanged as in FIG. 2(A) and with the reference beam at an
incident angle .THETA..sub.2 as in FIG. 2(B), the second data page
is multiplex-recorded on the recording layer 16A of the holographic
recording medium 16. Note that the time of exposure to the laser
beam per data page for recording the second data page is set to be
the same as for recording the first data page, thus allowing the
time of exposure to the laser beam per data page to be kept
constant all the time for recording.
[0040] Likewise, for the third and fourth data pages, the laser
output power of the laser beam is increased step by step in
accordance with a decrease in recording sensitivity of the
holographic recording medium 16. The reference beam at an incident
angle different from those for the first and second data pages
(with the object beam remaining unchanged) is projected onto the
recording layer 16A of the holographic recording medium 16,
allowing the interference fringes to be used to record information
by angle multiplexing.
[0041] According to the holographic multiplex recording method of
the first embodiment, in the process of multiplex-recording
information, the time of exposure to a laser beam per data page is
kept constant, and the laser output power of the laser beam is
increased in accordance with a decrease in recording sensitivity of
the holographic recording medium 16. This makes it possible to keep
the recording data rate constant and equalize nonuniformity in
recording due to vibrations or the like.
[0042] Note that with the first embodiment, such an example has
been shown in which the laser output power of the laser beam is
increased for each of the four data pages; however, the present
invention is not limited thereto. The laser output power of the
laser beam may be increased as appropriate in accordance with a
decrease in recording sensitivity of the holographic recording
medium.
Second Embodiment
[0043] Now, with reference to FIG. 3, an explanation will be given
to a holographic multiplex recording method according to a second
embodiment of the present invention. Note that FIG. 3 schematically
shows some of pixels of the SLM 18C according to the aforementioned
first embodiment.
[0044] As with the aforementioned first embodiment, an example will
be discussed where four data pages are recorded by angle
multiplexing on the recording layer 16A of the holographic
recording medium 16.
[0045] To begin with, the number of pixels of the SLM 18C to be
allocated to one bit of information is set to one pixel as shown in
FIG. 3(A), and the object beam is intensity modulated by the SLM
18C to record the first data page.
[0046] Then, when the recording sensitivity of the holographic
recording medium 16 has been reduced to less than or equal to 1/4
(=1/2.sup.2) of the initial value of the recording sensitivity at
the time of recording the second data page, the number of pixels of
the SLM 18C to be allocated to one bit of information is increased
to four pixels formed in a 2 by 2 square grid shape as shown in
FIG. 3(B). Then, the object beam is intensity modulated by the SLM
18C to multiplex-record the second data page. Note that the time of
exposure to a laser beam per data page and the laser output power
for recording the second data page are set to be the same as those
for recording the first data page. Thus, the time of exposure to a
laser beam per data page and the laser output power are kept
constant all the time for recording.
[0047] Likewise, at the time of recording the third and fourth data
pages, when the recording sensitivity of the holographic recording
medium 16 has been reduced to less than or equal to 1/9
(=1/3.sup.2) and 1/16 (=1/4.sup.2) of the initial value of the
recording sensitivity, respectively, the number of pixels of the
SLM 18C to be allocated to one bit of information is increased to 9
pixels formed in a 3 by 3 square grid shape and 16 pixels formed in
a 4 by 4 square grid shape as shown in FIGS. 3(C) and (D),
respectively. Then, the object beam is intensity modulated by the
SLM 18C to multiplex-record the third and fourth data pages.
[0048] As described above, the second embodiment is adapted such
that the number of pixels of the SLM 18C to be allocated to one bit
of information is increased to N.sup.2 when the recording
sensitivity of the holographic recording medium 16 has been reduced
to less than or equal to 1/N.sup.2 (N is an integer equal to two or
greater) of the initial value of the recording sensitivity.
[0049] According to the holographic multiplex recording method of
the second embodiment, in the process of multiplex-recording
information, the time of exposure to a laser beam per data page and
the laser output power are kept constant. Additionally, the number
of pixels of the SLM 18C to be allocated to one bit of information
is increased in accordance with a decrease in recording sensitivity
of the holographic recording medium 16 using the SLM 18C having a
plurality of pixels for intensity modulating the object beam. This
makes it possible to keep the frame rate constant and thus equalize
nonuniformity in recording due to vibrations or the like.
Furthermore, since the time of exposure to a laser beam per data
page and the laser output power can be kept constant, control can
be provided more easily.
[0050] In particular, since the pixels of the SLM 18C to be
allocated to one bit of information are formed in a square grid
shape, it is easy to correlate a pixel of the SLM with a pixel of
an imaging device at the time of reproduction. Accordingly, this
eliminates the need for providing optical components such as a
cylindrical lens for correlating pixels with each other, thereby
making it possible to provide apparatuses at reduced size and
costs.
[0051] Note that the second embodiment is adapted such that the
number of pixels of the SLM 18C to be allocated to one bit of
information is increased to N.sup.2 when the recording sensitivity
of the holographic recording medium has been reduced to less than
or equal to 1/N.sup.2 (N is an integer equal to two or greater) of
the initial value of the recording sensitivity; however, the
present invention is not limited thereto. The number of pixels of
the SLM to be allocated to one bit of information may also be
increased as appropriate in accordance with a decrease in recording
sensitivity of the holographic recording medium.
[0052] Furthermore, in the aforementioned first and second
embodiments, such an example has been shown where information is
multiplex-recorded by angle multiplex recording; however, the
present invention is not limited thereto. For example, the
holographic multiplex recording method according to the present
invention may also be applied to wavelength multiplex recording,
peristrophic multiplex recording and so on.
[0053] Furthermore, such an example has been shown where four data
pages are multiplex-recorded; however, the present invention is not
limited thereto, but is also applicable to the case where two or
three data pages are multiplex-recorded or five or more data pages
are multiplex recorded.
INDUSTRIAL APPLICABILITY
[0054] The holographic multiplex recording method according to the
present invention, and the holographic recording apparatus and the
holographic recording medium, which employ the method, provide
excellent effects that the recording data rate can be kept constant
and nonuniformity in recording due to vibrations or the like can be
equalized.
* * * * *