Gas separation
Reexamination Certificate
1999-08-25
2001-09-25
Schuberg, Darren (Department: 2872)
Gas separation
C359S015000, C359S025000, C359S030000
Reexamination Certificate
active
06293898
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a holographic memory.
2. Background of the Related Art
As large scale recording and reproduction of information is required, optical information recording/reproduction technologies which can make three dimensional information recording/reproduction using holography is under development recently in addition to two dimensional recording/reproduction devices that use optical disk recording medium, such as CD and DVD and the like.
Referring to
FIG. 1
, the in-formation recording/reproduction device using holography is provided with a laser
15
for a light source, and a beam splitter
14
for splitting a beam
16
from the laser
15
into a reference beam
6
and an object beam
7
. The reference beam part is provided with in an order of a beam expander
12
for expanding a diameter of the reference beam
6
, a beam deflector
11
for directing the reference beam
6
expanded by the beam expander
12
toward a telescope
9
with an 1:1 magnifying power and changing an incident angle to the telescope
9
, and the telescope
9
for forming an image of a reflecting plane of the beam deflector
11
on a recording medium
3
, and the object beam part is provided with in an order of a beam interrupter
17
for controlling advance of the beam, a beam expander
13
for expanding a diameter of the object beam
7
, a reflector
10
for deflecting a direction of beam an SLM(Spatial Light Modulator)
1
for displaying information, an FTL(Fourier Transform Lens)
2
for subjecting an image displayed on the SLM
1
to Fourier transform onto the recording medium
3
. The recording medium
3
is disposed at a place the reference beam
6
and the object beam
7
are met, an image forming lens
4
is provided at a place a given distance away from the recording medium
3
in the direction of the object beam
7
, a CCD)(Charge Coupled Device)
5
is provided at an image forming plane of the image forming lens
4
for converting an image from the SLM
1
into an electrical signal, and the SLM
1
and the CCD
5
are put under the control of a computer
8
.
The operation of the aforementioned holographic memory will be explained.
Upon displaying information on the SLM
8
by the computer
8
and directing the reference beam
6
and the object beam
7
to the recording medium
3
on the same time, the object beam
7
and the reference beam
6
make an interference, to form an interference pattern, which is recorded on the recording medium
3
. After the recording, if the object beam
7
is interrupted by the beam interrupter
17
while the reference beam
6
is directed to the recording medium
3
, the reference beam
6
is diffracted by the interference pattern recorded on the recording medium
3
, to reproduce the object beam
7
which advances in the direction of the CCD
5
. If the object beam
7
is made to form an image on the CCD
5
through the image forming lens
4
, the image displayed on the SLM
1
is formed on the CCD
5
, and the computer
8
stores and analysis the electrical signal from the CCD
5
. Another information may be recorded by displaying the another information on the SLM
1
and changing an angle of deflection of the beam deflector
11
, wherein, even if the angle of deflection is changed by the beam deflector
11
, an incident angle of the reference beam
6
to the recording medium
3
is changed while the image formation of the image formation plane on the recording medium
3
is maintained the same, because the telescope
9
positioned between the beam deflector
11
and the recording medium
3
has a magnifying power of 1:1. Eventually, the reference beams
6
having slightly different incident angles and the object beam
7
form slightly different interference patterns respectively at the same position of the recording medium
3
, which are recorded on the recording medium
3
. Therefore upon directing the reference beam
6
to the interference patterns overlapped at the same position, only the interference pattern formed by the reference beam
6
having the same incident angle with the reference beam
6
used in recording and the object beam
7
satisfies the Bragg condition, thereby reproducing only one object beam
7
. That is by controlling an incident angle of the reference beam
6
, the object beam
7
can be reproduced, selectively.
There have been a variety of studies for increasing a recording capacity of the memory using the aforementioned holography, a related art of which is illustrated in FIG.
2
. The device illustrated in
FIG. 2
is the related art device shown in
FIG. 1
added with beam deflectors
18
and
19
for deflecting beam in a direction perpendicular to the direction of beam deflection of the beam deflector
11
, i.e., at a xz-plane. As shown in
FIGS. 3A and 3B
, information is recorded on the recording medium
3
dividing the recording medium in a z-axis direction, for increasing a recording capacity.
However, since the technology utilizes the recording medium
3
only one dimensionally too, the technology has a limitation in increasing the recording capacity.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a holographic memory that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a holographic memory which can increase a recording capacity by using an HOE(Holographic Optical Element).
Another object of the present invention is to provide a holographic memory at a low cost.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the holographic memory includes a light source for emitting a beam, a beam splitter for splitting the beam into a reference beam and an object beam, a hologram memory unit for recording information on a cell to which the reference beam and the object beam are incident together, and reproducing information recorded previously when only the reference beam is incident thereto, a first beam path changing unit for directing the reference beam to an arbitrary direction for recording and reproducing the information, a composite HOE having a plurality of HOEs(Holographic Optical Element) stacked in a vertical direction each for diffracting the reference beam from the first beam path changing unit toward an arbitrary cell of the hologram memory unit, and a second beam path changing unit for adjusting a beam path of the object beam such that the object beam is incident to the hologram memory unit for recording the information.
The first beam path changing unit includes a beam expander for expanding a diameter of the reference beam split at the beam splitter, a reflector for changing a direction of advance of the reference beam expanded at the beam expander, a first beam deflector for deflecting the reference beam reflected at the reflector to an arbitrary direction, and a second beam deflector for re-deflecting the reference beam deflected at the first beam deflector perpendicular to a deflection direction of the first beam deflector.
The second beam path changing unit includes a first beam blocking unit for passing the object beam incident thereto in recording and blocking the object beam incident thereto in reproduction, a third beam deflector for deflecting the object beam passed through the beam blocking unit toward an arbitrary direction, a beam expander for expanding a diameter of the object beam deflected at the third beam deflector, a reflector for changing a direction of advance of the object beam expanded by the beam expan
Fleshner & Kim LLP
LG Electronics Inc.
Schuberg Darren
LandOfFree
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