U.S. patent application number 11/382451 was filed with the patent office on 2006-08-31 for double facing double storage capacity.
This patent application is currently assigned to RESEARCH INVESTMENT NETWORK, INC.. Invention is credited to IDRISS EL HAFIDI, ROMUALDA GRZYMALA, PATRICK MEYRUEIS.
Application Number | 20060193023 11/382451 |
Document ID | / |
Family ID | 36931709 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060193023 |
Kind Code |
A1 |
EL HAFIDI; IDRISS ; et
al. |
August 31, 2006 |
DOUBLE FACING DOUBLE STORAGE CAPACITY
Abstract
A first holographic data storage device has a first set of
holograms stored thereon. A second holographic data storage device
has a second set of holograms stored thereon. An opaque layer is
disposed between and attached to one side of the first and the
second holographic data storage devices. In the case of double
reflective diffractive recording, the opaque layer is not
necessary.
Inventors: |
EL HAFIDI; IDRISS;
(STRASBOURG, FR) ; GRZYMALA; ROMUALDA;
(STRASBOURG, FR) ; MEYRUEIS; PATRICK; (STRASBOURG,
FR) |
Correspondence
Address: |
DISCOVISION ASSOCIATES
2265 E. 220TH STREET
LONG BEACH
CA
90810
US
|
Assignee: |
RESEARCH INVESTMENT NETWORK,
INC.
IRVINE
CA
|
Family ID: |
36931709 |
Appl. No.: |
11/382451 |
Filed: |
May 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10511624 |
Oct 18, 2004 |
|
|
|
11382451 |
May 9, 2006 |
|
|
|
Current U.S.
Class: |
359/15 ;
G9B/7.027; G9B/7.167 |
Current CPC
Class: |
G03H 1/26 20130101; G11B
7/24038 20130101; G03H 2001/2228 20130101; G03H 2250/33 20130101;
G03H 2001/2231 20130101; G03H 2001/0264 20130101; G03H 1/265
20130101; G03H 2001/2615 20130101; G11B 7/0065 20130101 |
Class at
Publication: |
359/015 |
International
Class: |
G02B 5/32 20060101
G02B005/32 |
Claims
1. An apparatus for reading a double-sided diffractive holographic
data storage device having first and second reflective holograms
stored on first and second sides respectively, comprising: a first
multi-scanning device for directing a first read beam incident on
the first side at a first predetermined angle; and a first
detecting device for detecting the first read beam reflected from
the storage device.
2. The apparatus according to claim 1 further comprising a rotating
unit for rotating the double-sided diffractive holographic data
storage device into first and second positions.
3. The apparatus according to claim 2 wherein the rotating unit is
in the first position when the read beam is incident upon the first
side and the detecting device detects a first diffractive data
output packets produced by reflective diffraction from the first
side.
4. The apparatus according to claim 2 wherein the rotating unit is
in the second position when the first read beam is incident upon
the second side and the detecting device detects a second data
packet output produced by reflective diffraction from the second
side.
5. The apparatus according to claim 1 wherein the first and second
reflective holograms are angularly multiplexed holograms.
6. The apparatus according to claim 1 wherein the double-sided
device includes an organic material.
7. The apparatus according to claim 6 wherein the organic material
is a polypeptide.
8. The apparatus according to claim 1 wherein the first read beam
is coherent or incoherent.
9. The apparatus according to claim 8 further comprising: a second
multi-scanning device for directing a second read beam incident
upon a second side of the diffractive device at a second
predetermined angle; and a second detecting device for detecting a
second diffractive holographic image formed by the second
reflectively diffractive read beam reflected from the second
side.
10. The apparatus according to claim 9 wherein the first read beam
is generated from a coherent or non-coherent light having a same
wavelength as a recording light.
11. The apparatus according to claim 9 wherein the second read beam
is coming from a laser or a portion of the first read beam is
coming through a beam splitter.
12. The apparatus according to claim 9 wherein the dual layer
located on double-faced plate is an angularly multiplexed
hologram.
13. The apparatus according to claim 9 wherein the second read beam
is coherent or incoherent.
14. A method for reading a double-sided holographic data storage
device having first and second reflective holograms stored on first
and second sides respectively, comprising: directing a first read
beam incident on first side at a predetermined angle; and detecting
the first read beam reflectively diffracted from the storage
device.
15. The method according to claim 14 further comprising rotating
the double-sided diffractive holographic data storage device into
first and second positions.
16. The method according to claim 15 wherein the rotating is in the
first position when the first beam is incident on the first side
and the detecting device detects a first output data packet
produced by reflective diffraction from the first side.
17. The method according to claim 15 wherein the rotating unit is
in the second position when the first beam is incident upon the
second side and the detecting device detects a second holographic
image reflectively diffracted from the second side of the
holographic storage device.
18. The method according to claim 14 wherein the first and second
reflective holograms are angularly multiplexed holograms.
19. The method according to claim 14 wherein the double-sided
device includes an organic material.
20. The method according to claim 14 wherein the organic material
is a polypeptide.
21. The method according to claim 14 wherein the first read beam is
coherent or incoherent light beam.
22. A method according 14 further comprising: directing a second
read beam incident upon a second side of the diffractive device at
a second predetermined angle; and detecting a second diffractive
holographic image formed by the second reflectively diffractive
read beam reflected from the second side.
23. The method according to claim 22 wherein the first read beam is
generated from a coherent or non-coherent light having a same
wavelength as a recording light.
24. The method according to claim 22 wherein the second read beam
is coming from a laser or a portion of the first read beam is
coming through a beam splitter.
25. The apparatus according to claim 22 wherein the dual layer
located on double-faced plate is an angularly multiplexed hologram.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 10/511,624, filed Oct. 18, 2004.
FIELD OF THE INVENTION
[0002] The present invention generally relates to photonics data
memory devices. In particular, the present invention relates to a
double-faced diffractive holographic data storage device.
BACKGROUND OF THE INVENTION
[0003] There is a strong interest in high-capacity data storage
systems with fast data access due to an ever-increasing demand for
data storage. Limitations in the storage density of conventional
magnetic memory devices have led to considerable research in the
field of optical memories. Holographic memories have been proposed
to supersede the optical disc (CD-ROMs and DVDs) as a high-capacity
digital storage medium. The high density and speed of holographic
memory results from the use of three-dimensional recording and from
the ability to simultaneously read out an entire page of data. The
principal advantages of holographic memory are a higher information
density, a short random-access time, and a high information
transmission rate.
[0004] While holographic data storage systems have not yet replaced
current CD and DVD systems, many advances continue to be made which
further increase the potential of storage capacity of holographic
memories. This includes the use of various multiplexing techniques
such as angle, wavelength, phase-code, fractal, peristrophic, and
shift. However, previous methods for recording information in
highly multiplexed volume holographic elements, and for reading
them out, have not proved satisfactory in terms of throughput,
crosstalk, and storage capacity.
[0005] It has also been proposed to use double-sided holographic
data storage device. However, issues such as crosstalk between
layers, speed of data access and speed of access to the double
diffractive holographic layers continue to challenge technological
advances in this area.
[0006] Thus, it would be desirable to provide a diffractive
holographic data storage device, which increases storage capacity
by utilizing double layers of the data storage device. Also, it
would be desirable to provide techniques for providing fast access
to double sides and layers of a diffractive holographic data
storage device. Furthermore, it will be desirable to provide a
diffractive holographic data storage device, that is compatible
with the traditional HYDIF multiplexing technology. The
compatibility is coming from the smart association of two
diffractive sides recorded with HYDIF process but allowing by an
improvement a simultaneous simple reading of both faces. This
association doubles the storage capacity and increase global
reading speed of stored data access.
SUMMARY OF THE INVENTION
[0007] According to one aspect of the invention, a double-sided
diffractive holographic data storage device includes a first
diffractive holographic data storage device having a first set of
holograms stored thereon and a second diffractive holographic data
storage device having a second set of holograms stored thereon. The
first reflective hologram is formed by the diffracted part of the
reference beam processed by the first side of the double-side
diffractive holographic data storage device. The storage device may
be coated with polypeptide material. As an example, an opaque layer
is disposed between and attached to one side of the first and
second diffractive holographic data storage devices. In accordance
with another aspect of the invention, an apparatus and method for
reading a double-sided diffractive holographic data storage device
having first and second reflective holograms stored on first and
second sides respectively is provided. The apparatus includes a
light source for generating a reference beam, a multi-scanning
device for directing the reference beam incident on the first side
of the double-sided diffractive holographic data storage device at
a predetermined angle, wherein a first reflective hologram is
formed by the reference beam reflected from the first side of the
double-sided diffractive holographic data storage device. A
detecting device is provided for detecting the reference beam
reflected from the double-sided diffractive holographic data
storage device. A rotating unit rotates the double-sided
diffractive holographic data storage device into one of two
positions, wherein when the rotating unit is in a first position,
the reference beam is incident upon the first side of the
double-sided diffractive holographic data storage device and the
detecting device detects the first output data packet (i.e.,
diffractive holographic image) reflected from the first side of the
diffractive holographic data storage device, and when the rotating
unit is in a second position, the reference beam is incident upon a
second side of a double-sided diffractive holographic data storage
device, and its detecting device detects the second output data
packet (i.e., diffractive holographic image) reflected from the
second side of the diffractive holographic data storage device.
[0008] According to another aspect of the invention, an apparatus
and method of reading a double-sided diffractive holographic data
storage device having a reflective and a transmissive set of
diffractive patterns storing data packets on first and second sides
is provided.
[0009] Further objects, advantages, and novel features of the
present invention will become apparent to those skilled in the art
from this disclosure, including the following detailed description,
as well as by practice of the invention. While the invention is
described below with reference to a preferred embodiment(s), it
should be understood that the invention is not limited thereto.
Those of ordinary skill in the art having access to the teachings
herein will recognize additional implementations, modifications,
and embodiments, as well as other fields of use, which are within
the scope of the invention as disclosed and claimed herein and with
respect to which the invention could be of significant utility.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] In order to facilitate a fuller understanding of the present
invention, reference is now made to the appended drawings. These
drawings should not be construed as limiting the present invention,
but are intended to be exemplary only.
[0011] FIGS. 1A-1D are graphs illustrating recording and reading
processes of transmissive and reflective holography in accordance
with one embodiment of the present invention.
[0012] FIG. 2 is a schematic representation of an apparatus for
recording data in the form of a reflective hologram in accordance
with one embodiment of the present invention.
[0013] FIG. 3 is a graph showing the effect of recording angle on
angular selectivity in accordance with one embodiment of the
present invention.
[0014] FIG. 4 is a schematic representation of a double-faced
diffractive holographic data storage device in accordance with one
embodiment of the invention.
[0015] FIG. 5 is a schematic representation of an apparatus for
reading information stored on the double-faced diffractive
holographic data storage device shown in FIG. 4 in accordance with
one embodiment of the invention.
[0016] FIG. 6 is a schematic representation of an apparatus for
reading information stored on the double-faced diffractive
holographic data storage device shown in FIG. 4 in accordance with
another embodiment of the invention.
[0017] FIG. 7 is a schematic representation of an apparatus for
reading information stored on the double-faced diffractive
holographic data storage device shown on FIG. 4 in accordance with
yet another embodiment of the invention.
[0018] FIG. 8 is a schematic representation of an apparatus for
reading information stored on the double-faced diffractive
holographic data storage device incorporating both reflective and
transmissive holograms in accordance with one embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
Storing/Recording Phase
[0019] A diffractive holographic data storage device contains
information stored during a phase of storing information. In the
storing or recording phase, a laser emits a coherent light beam
that is split into two beams, a reference beam and an object beam,
by means of a splitter (as shown in FIG. 2). The object beam may be
filtered and collimated. The object beam is directed to a display
means, which displays an image to be recorded. The object beam
becomes modulated by the information to be recorded by means of
reflection off the display or transmission through the display.
[0020] The display may be any device for displaying a data packet
in a system, such as a spatial light modulator (SLM) or liquid
crystal light valve (LCLV). The plurality of bits represented on
the display screen of the display may be presented as a
two-dimensional pattern of transparent and opaque pixels (i.e.,
data packet). The data packet displayed is derived from any source
such as a computer program, the Internet, and so forth. In an
Internet storage application, the packets displayed may be
formatted similarly to the packets of the Internet.
[0021] The reference laser beam defines the address where the
information is to be stored. The reference laser beam interferes
coherently with the object beam, which is the laser beam carrying
the information to be stored, to form the interference pattern or
hologram, which is stored in the memory device due to the
perturbation in the refractive index. Thus, each hologram is stored
at a unique angle of the reference beam. The separation between the
various holograms stored within the same volume relies on the
coherent nature of the hologram, in order to allow its retrieval in
phase with the volume only for a defined angle value. It is noted
that the reference beam may undergo various reflections and
orientations using a set of mirrors to modify the angle between the
reference beam and the object beam. Thus, by this mechanism angular
multiplexing is implemented. In other words, angular multiplexing
is carried out by sequentially changing the angle of the reference
beam by means of mirrors. The multiplexing process may be
programmable. It is also contemplated that the reference beam
provides an identity for the page carried by the signal beam or
object beam, so that the information is distinguishable from other
pages sharing the same volume inside the diffractive holographic
data storage medium.
[0022] Whether a reflective holograph memory or a transmissive
holograph memory is produced depends on the recording process. A
transmissive hologram is produced when, in the recording process,
the reference beam and object beam are on the same side of the
diffractive holographic plate (FIG. 1A). A reflective hologram is
produced when, in the recording process, the reference beam and
object beam are on the opposite side of the diffractive holographic
plate (FIG. 1C). Details of a reading process of the different
types of holograms are described below.
Reading Phase
[0023] Retrieving the stored information from the diffractive
holographic data storage device requires the use of a read beam
whose characteristics correspond to those employed for writing or
for storage (wavelength, angle of incidence and position within the
storage material). This read beam induces diffraction due to
perturbation in the refractive index corresponding to the
characteristics of the beam, thereby creating the stored modulated
beam. The read beam carries the address of the page selected for
retrieval. Physically, addressing during retrieval is similar to
the recording phase (i.e., the read beam replicates the reference
beam used for storing the desired pages).
[0024] The read beam may be controlled by an addressing-read system
that includes mirrors or micromirrors associated with actuators,
i.e., galvanometers or micromotors, therefore capable of undergoing
rotation that allows each mirror to be oriented in the desired
direction. These mirrors may be positioned at defined points or
nodes by software, for the purpose of angularly indexing a
wavefront for a point of defined coordinates (X,Y) in the memory
device. The laser beam angular processing can be also implemented
through dynamic means of grating or acoustic optics or a joint use
of both or other microtechnologies.
[0025] In angular multiplexing, the read beam is positioned in
order to access a data packet contained at a defined point (X,Y) in
a diffractive holographic data storage device corresponding to an
addressing angle. The reference beam angles in the reading
procedure are similar to the reading (e.g., reference) beam angles
the writing or recording procedure. However, the reading procedure
may be carried out with a greater degree of tolerance than the
recording procedure. It is possible to use a very compact laser
source of a solid-state type for the reading process because laser
power necessary for reading is much lower than the one for
recording. It is contemplated that the wavelength of the read beam
may be the same at the wavelength of the recording beam (e.g.,
reference beam).
[0026] Referring to FIG. 1A, there is shown a schematic
representation of a transmissive hologram in accordance with
conventional holographic recording techniques. In the recording set
up, the object beam and the reference beam reach the recording
plate on the same side. Referring to FIG. 1C, there is shown a
schematic representation of a reflective hologram in accordance
with non-conventional holographic recording techniques. In this
recording setup, the object beam and the reference beam reach the
recording plate on the opposite side. FIG. 1B is referring to a
schematic representation of a transmissive hologram in accordance
with diffractive holographic reading techniques. To read a page or
a packet of information, the reading and output beams are located
on the opposite side of the transmissive hologram, while FIG. 1D is
referring to a schematic representation of a reflective hologram in
accordance with diffractive holographic reading techniques. In this
case, the reading and output beams are located on the same side of
the reflective hologram.
[0027] Referring to FIG. 2, there is shown a schematic
representation of an apparatus 200 for recording data in the form
of a reflective hologram according to one embodiment of the
invention. The recording apparatus 200 includes a laser 220, a beam
splitter 270, a tilting micromirror 240, a multimirror device 260,
a data recording plate 280, a first lens 230, a second lens 210, a
display device (e.g., spatial light modulator (SLM)) 250, mirrors
215, 225, and a computer 290.
[0028] In the recording apparatus 200 shown in FIG. 2, a light beam
201 from the laser 220 is directed to the splitter 270 which splits
the light beam 201 into an object beam 202 and a reference beam
203. The reference beam 203 is then emitted to the tilting
micromirror unit 240, which directs the beam to a preselected
mirror in the multimirror device 260. The light is reflected from
the multimirror device 260 to a data recording plate 280 which
comprises a polypeptide material or other materials with similar
characteristics. Further details of the angular multiplexing
technique used in the recording apparatus of 200 as well as the
polypeptide material in the recording plate 280 are described in a
copending application entitled "Photonics Data Storage System Using
a Polypeptide Material and Method for Making Same", Serial No.
PCT/FR01/02386, which is hereby incorporated by reference in its
entirety.
[0029] The polypeptide layer may be calibrated to resolve in a
thickness range of approximately 10 to 40 micros depending on the
application. It should be noted that some crosstalk between the
layers may limit the density of each layer so as to reduce the
density of the optical density. Nevertheless, the two sides result
in a doubling of the global density which more than makes up for
this loss. To optimize the crosstalk, each layer may be constructed
using a different composition. For example, each layer may have
different doping. It is noted that the underneath layer receives
less light energy than the above one layers and because every layer
absorbs one part of the energy, the underneath layer has the
response. Therefore, the doping may be adapted to compensate for
different layers. The process is to be adapted for every layer and
that through the process, the top layer is more hardened because it
supports the protective coat. Thus, a controlling process of the
thickness of every layer may be developed to achieve optimization
of the crosstalk.
[0030] The computer 290 generates data recorded with two
consecutive angles, which is to be stored on the data recording
plate 280. This data is transferred to an optical representation on
the SLM 250. The object beam light 202 reflects off mirrors 215 and
225 and passes through the SLM 250. After passing through the SLM
250, the light is modulated and reaches lenses 230 and 210 which
collimate the light and direct it to the back of the data recording
plate 280, forming a reflective diffractive holographic image by
interference between the reference beam 203 reflected from the
multimirror device 260.
[0031] Referring to FIG. 3, a graph is provided showing the effect
of recording angle on angular selectivity according to one
embodiment of the invention. Angular selectivity is defined as the
angle of separation, which is required to prevent crosstalk between
two adjacent packets of data in an angularly multiplexed hologram.
The graph shows that for the same thickness of a polypeptide layer
the angular selectivity is between 10 and 60 for a transmissive
hologram and less 1.degree. for a reflective hologram.
[0032] The angle selectivity .DELTA..THETA. may be different in the
reflective case and in the transmissive case, the reason being that
the physics of the layer internal molecular organization induced by
light modulation in the two cases is not the same. The angular
selectivity is defined as: .DELTA..THETA.=.lamda./2d sin
(.THETA..sub.B)
[0033] Where .DELTA..THETA. is the angular difference between two
angular multiplexing angles;
[0034] d is the thickness of the polypeptide layer; and
[0035] .THETA..sub.B is the Bragg angle.
[0036] In is contemplated that this angle, for a given modulation,
gives maximum diffraction efficiency. In one embodiment, this angle
can be the recording angle in the case where there is no
modification of the thickness of the polypeptide layer between
recording and reading.
[0037] FIG. 4 is a schematic representation of a double-faced
diffractive holographic data storage device in accordance with one
embodiment of the invention. The double-faced diffractive
holographic data storage device 400 includes a first face 410, a
second face 420 and an opaque medium 430.
[0038] Each of the 410 and 420 faces is recorded using the
recording apparatus as shown in FIG. 1. Each separate diffractive
holographic data storage device is then attached to opposite sides
of an opaque medium 430. In one embodiment, these separate
diffractive holographic memories are reflective holograms. The
reflective hologram is formed when the object beam and the
reference beam are located at the opposite side of the recording
plate during the recording process. The opaque medium 430 is used
to prevent light from coming from one side of the reading beam and
reading the second side in the reading process. The opaque medium
430 may include a photosensitive layer that is coated between the
glass substrates and darkened after UV (ultraviolet) light.
[0039] FIG. 5 is a schematic representation of an apparatus for
reading information stored on the double-sided diffractive
holographic data storage device as shown in FIG. 4 according to one
embodiment of the invention. The apparatus 500 includes a laser
538, a multi-scanning device 540, a detector 546, imaging lenses
542 and 544, a rotating table 550, and the double-faced memory unit
400.
[0040] The laser 538 generates a beam of light, which is directed
by a multi-scanning device 540 to the double-faced memory unit 400.
As described in FIG. 4, the double-faced memory unit 400 includes
first and second faces 410 and 420. One of the reflective holograms
from the double-faced memory unit 400 passes through the pair of
lenses 542, 544 before reaching the detector 546. The first side
(i.e., face) 410 of the double-faced memory unit 400 is read in the
configuration shown. In order to read the opposite side 420 of the
double-faced memory unit 400, the rotating table 550 is rotated at
an angle (e.g., 180.degree.) so that the beam from the
multi-scanning device 540 reaches that second face 420. The reading
process of information on the second face 420 is similar to the
reading process on the first face 410.
[0041] FIG. 6 is a schematic representation of the apparatus for
reading the double-faced memory unit 400 according to another
embodiment of the present invention. The apparatus 600 includes a
detector multi-scanning device 640, the double-faced memory unit
400, a detecting system 610, and a pair of lenses 642 and 644.
[0042] The multi-scanning device 640 includes a tilting micromirror
650 and a multimirror device 652. The detecting system 610
comprises a CCD (charge-coupled device), e.g., camera 646 coupled
to a computer 654 and a monitor 656. The reading process applied in
this embodiment is similar to the reading process described in FIG.
5 in which the reading of one side of the recording plate 400
occurs before the reading of the other side of the recording
plate.
[0043] Referring now to FIG. 7, another embodiment of an apparatus
for reading a double-faced memory unit 400 is shown. The apparatus
700 includes a laser 758, a beam splitter 760, mirrors 761 and 762,
two multi-scanning devices 764 and 768, the double-faced memory
unit 400, two pairs of imaging lenses 772, 770 and 776 and 778, and
two detectors 774 and 780.
[0044] This apparatus 700 eliminates the necessity of a rotating
table (e.g., rotating table 650 shown in FIG. 6) and thus greatly
increases the speed of the reading process since the reading of the
double-faced memory unit 400 is simultaneous. In other words, both
sides of the double-faced memory 400 can be read in parallel with
this implementation.
[0045] The beam splitter 760 receives a light beam from the laser
758 and performs a splitting function to the light beam. The mirror
761 and 762 each directs a portion of the beam from the laser 758
to the first and second multi-scanning devices 764 and 768,
respectively. The multi-scanning devices 764, 768 each direct a
beam to a respective first and second side 410, 420 of the
double-faced diffractive holographic data storage device 400. The
resulting hologram from the first side 410 passes through imaging
lenses 770 and 772 and is detected by detector 774. Additionally,
the resulting holograph from the second side 420 is directed to a
pair of lenses 776 and 778 and is directed by detector 780.
[0046] FIG. 8 is a schematic representation of an apparatus for
reading information stored on the double-faced diffractive
holographic data storage device incorporating both reflective and
transmissive holograms in accordance with one embodiment of the
present invention. The apparatus 800 includes a double-faced
hologram memory device 810, a detector 820, and a detector 830. The
memory device 810 includes a memory component 845 and a memory
component 855. The two holograms are bonded together in such a
manner that in a reading setup simultaneous access of both
components 845 and 855 is achieved. When the reference beam emits
upon the component 845, a first hologram is generated and a first
output is detected by the detector 820. The same reference beam
passes through component 845 and reaches component 855 to generate
a second hologram and a second output page is detected from the
hologram by detector 830. A portion of the reading beam diffracted
by the multiplexed volume hologram forms the reconstruction, which
is detected by the detectors 820 and 830. The reconstructed beam
carries the data that is a replica of the desired page. It is
contemplated that there is not an opaque medium between the two
components 845 and 855 so that simultaneous reading can be
achieved. In order to read information from both sides of the
combined memory device 810, component 845 is a reflective hologram
and component 855 is a transmissive hologram.
[0047] The present invention is not to be limited in scope by the
specific embodiments described herein. Indeed, this application is
intended to cover any modifications of the present invention, in
addition to those described herein, and the present invention is
not confined to the details which have been set forth. Thus, the
scope of the invention should be determined by the appended claims
and their legal equivalents, rather than by the examples given.
* * * * *