U.S. patent application number 14/240643 was filed with the patent office on 2014-07-24 for wearable data display.
The applicant listed for this patent is Milan Momcilo Popovich, Jonathan David Waldern. Invention is credited to Milan Momcilo Popovich, Jonathan David Waldern.
Application Number | 20140204455 14/240643 |
Document ID | / |
Family ID | 46963982 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140204455 |
Kind Code |
A1 |
Popovich; Milan Momcilo ; et
al. |
July 24, 2014 |
WEARABLE DATA DISPLAY
Abstract
A transparent wearable data display having a source of
collimated light a deflector for deflecting the collimated light
into a scanned beam, and a first array including one column and
integer N rows of switchable grating elements sandwiched between
first and second parallel transparent substrates. The substrates
together functioning as a first light guide, and a second array
including M columns and N rows of switchable grating elements
sandwiched between third and fourth parallel transparent substrates
which together function as a second lightguide. Transparent
electrodes are applied to opposing substrates. A first coupling for
directing the scanned beam into a first TIR light path of the first
lightguide along the first array column; and a second coupling for
directing the first TIR light into a second TIR path of the second
lightguide along a row of elements of the second array.
Inventors: |
Popovich; Milan Momcilo;
(Leicester, GB) ; Waldern; Jonathan David; (Los
Altos Hills, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Popovich; Milan Momcilo
Waldern; Jonathan David |
Leicester
Los Altos Hills |
CA |
GB
US |
|
|
Family ID: |
46963982 |
Appl. No.: |
14/240643 |
Filed: |
August 22, 2012 |
PCT Filed: |
August 22, 2012 |
PCT NO: |
PCT/GB2012/000677 |
371 Date: |
February 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61573067 |
Aug 24, 2011 |
|
|
|
Current U.S.
Class: |
359/316 ;
359/567 |
Current CPC
Class: |
G02B 5/18 20130101; G02B
6/0028 20130101; G02B 27/0101 20130101; G02B 27/0172 20130101; G02F
1/292 20130101; G02B 6/0078 20130101; G02B 27/4227 20130101; G02F
1/13342 20130101; G02B 2027/0118 20130101; G02B 6/0035
20130101 |
Class at
Publication: |
359/316 ;
359/567 |
International
Class: |
G02B 27/01 20060101
G02B027/01; G02F 1/29 20060101 G02F001/29; G02B 27/42 20060101
G02B027/42 |
Claims
1. A transparent wearable data display comprising: a source of
light; a means for collimating said light; a means for deflecting
said collimated light into a scanned beam; a first array comprising
one column containing M switchable grating elements sandwiched
between first and second parallel transparent substrates, said
substrates together functioning as a first light guide; a second
array comprising N columns and M rows of switchable grating
elements sandwiched between third and fourth parallel transparent
substrates, said substrates together functioning as a second light
guide; transparent electrodes applied to said first and second and
said third and fourth substrates; a first coupling means for
directing said scanned beam into a first TIR light path between the
outer surfaces of said first lightguide along said first array
column; and a second coupling means linking each element of said
first array to the first element of a row of elements of said
second array, said switchable grating elements each having a
diffracting state and a non diffracting state, each element of said
first array when in its diffracting state directing light via said
second coupling means into a second TIR path along a row of said
second array, each element of said second array in said diffracting
state deflecting light through said fourth substrate.
2. The wearable data display of claim 1 wherein at least one of
said electrodes of said first array is patterned into 1.times.N
independently switchable elements each said element overlapping one
of said first array grating elements, wherein at least one of said
electrodes of said second array is patterned into M.times.N
independently switchable elements each said element overlapping one
of said second array grating elements.
3. The wearable data display of claim 1 wherein said switchable
grating elements each have a diffracting state when no electric
field is applied across said electrodes and a non diffracting state
when a field is applied across said electrodes.
4. The wearable data display of claim 1 wherein each element of
said first array is disposed adjacent a first element of a row of
said second array.
5. The wearable data display of claim 1 wherein each said grating
element of said second array encodes image information.
6. The wearable display of claim 1 wherein said fourth substrate
faces a viewer of the display.
7. The wearable data display of claim 1 wherein at any point in
time said element of said second array in said diffracting state
forms an image of the information encoded within said grating
element at a predefined viewing range and an angular bearing
defined by the instantaneous deflection angles of said scanned
beam.
8. The wearable data display of claim 1 wherein said substrates of
said first array are parallel to said substrates of said second
array.
9. The wearable data display of claim 1 wherein said substrates of
said first array are orthogonal to said substrates of said second
array.
10. The wearable data display of claim 1 wherein said first
coupling means is a grating device.
11. The wearable data display of claim 1 wherein said second
coupling means is a grating device abutting each of said first and
second arrays.
12. The wearable data display of claim 1 wherein each switchable
grating element of said second array is divided into independently
switchable columns aligned orthogonally to the direction of said
output array TIR path.
13. The wearable data display of claim 1 wherein said switchable
grating is a Switchable Bragg Grating.
14. The wearable data display of claim 1 wherein said scanned beam
is characterised by angular deflections in two orthogonal
directions.
15. The wearable data display of claim 1 wherein the intensity of
said scanned beam is modulated by varying the refractive index
modulation of at least one of the switchable grating elements
traversed by the beam.
16. The wearable data display of claim 1 wherein said light
comprises first, second and third wavelength light.
17. The wearable data display of claim 1 wherein said light
comprises first second and third wavelength light and each
switchable grating element is a multiplexed SBG comprising a first
grating for diffracting said first wavelength light and a second
grating for diffracting said second and third wavelength light.
18. The wearable data display of claim 1 wherein said light
comprises first second and third wavelength light and each
switchable grating element is a multiplexed SBG comprising a first
grating for diffracting said first wavelength light, a second
grating for diffracting said second wavelength light and a third
grating for diffracting said third wavelength light.
19. The wearable data display of claim 1 wherein each said
switchable grating is a surface relief grating backfilled with an
electrically variable refractive index medium.
20. The wearable data display of claim 1 wherein each switchable
grating element in at least one of said first array and said second
array is divided into independently switchable columns aligned
orthogonally to said TIR paths, wherein the refractive index
modulation of each element in said switchable column is dynamically
controlled such that a predetermined amount of light is diffracted
by said switchable column through said fourth substrate.
21. The wearable data display of claim 1 wherein said data display
is one of a pair of left and right eyepieces.
22. The wearable data display of claim 1 wherein said means for
deflecting said collimated light is an electro optical device.
23. The wearable data display of claim 1 wherein said means for
deflecting said collimated light comprises: a first transparent
optical substrate with an input surface and an output surface; a
second transparent optical substrate with an input surface and an
output surface; transparent electrodes applied to said output
surface of said first substrate and said input surface of said
second substrate; an electrically variable refractive index layer
having a planar surface and a second surface shaped to provide an
array of prisms; and a fixed refractive index layer having a planar
surface and a second surface shaped to provide an array of
prismatic cavities, said prisms and said prismatic cavities having
identical and opposing geometries, each said prism abutting one of
said prismatic cavities, wherein said planar surface of said
variable refractive index layer abuts said output surface of said
first substrate and said planar surface of said fixed refractive
index layer abuts said input surface of said second substrate,
wherein said transparent electrodes are electrically couple to a
variable voltage generating means, wherein at least one of said
transparent electrodes is patterned into independently switchable
electrode elements having substantially the same cross sectional
area as said prisms such that said variable refractive index prisms
may be selectively switched in discrete steps from a fully
diffracting to a non diffracting state by an electric field applied
across said transparent electrodes.
Description
REFERENCE TO PRIORITY APPLICATION
[0001] This application claims the priority of U.S. Provisional
Patent Application No. 61/573,067 with filing date 24 Aug. 2011
entitled "Wearable Data Display".
REFERENCE TO RELATED APPLICATIONS
[0002] Each of the following applications is incorporated herein by
reference in its entirety: PCT Application No.: US2008/001909, with
International Filing Date: 22 Jul. 2008, entitled LASER
ILLUMINATION DEVICE; PCT Application No.: US2006/043938, entitled
METHOD AND APPARATUS FOR PROVIDING A TRANSPARENT DISPLAY; PCT
Application No.: PCT/GB2010/001982 entitled COMPACT EDGE
ILLUMINATED EYEGLASS DISPLAY PCT Application No.: PCT/GB2010/000835
with International Filing Date: 26 Apr. 2010 entitled COMPACT
HOLOGRAPHIC EDGE ILLUMINATED EYEGLASS DISPLAY; and PCT Application
No.: PCT/GB2010/002023 filed on 2 Nov. 2010 entitled APPARATUS FOR
REDUCING LASER SPECKLE, U.S. patent application Ser. No. 10/555,661
filed 4 Nov. 2005 entitled SWITCHABLE VIEWFINDER DISPLAY; U.S.
Provisional Patent Application No. 61/344,748 WITH FILING DATE 28
Sep. 2010 ENTITLED EYE Tracked Holographic Edge Illuminated
Eyeglass Display; No. 61/457,835 with filing date 16 Jun. 2011
entitled HOLOGRAPHIC BEAM STEERING DEVICE FOR AUTOSTEREOSCOPIC
DISPLAYS; and U.S. Provisional Patent Application No. 61/573,066
with filing date 24 Aug. 2011 by the present inventors entitled
IMPROVEMENTS TO HOLOGRAPHIC POLYMER DISPERSED LIQUID CRYSTAL
MATERIALS AND DEVICES.
BACKGROUND OF THE INVENTION
[0003] This invention relates to a wearable display device, and
more particularly to a wearable display using electrically
switchable holographic optical elements.
[0004] There is a requirement for a compact see through data
display capable of displaying image content ranging from symbols
and alphanumeric characters to high-resolution pixelated images.
The display should be highly transparent and the displayed image
content should be clearly visible when superimposed over a bright
background scene. The display should provide full colour with an
enhanced colour gamut for optimal data visibility and impact. A
prime requirement is that the display should be as easy to wear,
natural and non-distracting as possible with a form factor similar
to that of ski goggles or, more desirably, sunglasses. The eye
relief and pupil should be big enough to avoid image loss during
head movement even for demanding military and sports activities.
The image generator should be compact, solid state and have low
power consumption.
[0005] The above goals are not achieved by current technology.
Current wearable displays only manage to deliver see through,
adequate pupils, eye relief and field of view and high brightness
simultaneously at the expense of cumbersome form factors. In many
cases weight is distributed in the worst possible place for a
wearable display, in front of the eye. The most common approach to
providing see through relies on reflective or diffractive visors
illuminated off axis. Microdisplays, which provide high-resolution
image generators in tiny flat panels, do not necessarily help with
miniaturizing wearable displays because the requirement for very
high magnifications inevitably results in large diameter optics.
Several ultra low form factor designs offering spectacle-like form
factors are currently available but usually require aggressive
trade-offs against field of view, eye relief and exit pupil.
[0006] The optical design benefits of diffractive optical elements
(DOEs) are well known including unique and efficient form factors
and the ability to encode complex optical functions such as optical
power and diffusion into thin layers. Bragg gratings (also commonly
termed volume phase gratings or holograms), which offer the highest
diffraction efficiencies, have been widely used in devices such as
Head Up Displays.
[0007] It is also known that diffractive optical elements can be
used to provide virtual images for direct viewing or for viewing
with the aid of optical systems. U.S. Pat. No. 6,052,540 by Koyama
discloses a viewfinder device comprising a transmission hologram
that can be located at a position other than in an image plane. The
position of the virtual image formed by the transmission hologram
is arranged to lie at the image plane of the optical system.
[0008] An important class of diffractive optical element known as
an electrically Switchable Bragg Gratings (SBG) is based on
recording Bragg gratings into a polymer dispersed liquid crystal
(PDLC) mixture. Typically, SBG devices are fabricated by first
placing a thin film of a mixture of photopolymerisable monomers and
liquid crystal material between parallel glass plates. One or both
glass plates support electrodes, typically transparent indium tin
oxide films, for applying an electric field across the PDLC layer.
A Bragg grating is then recorded by illuminating the liquid
material with two mutually coherent laser beams, which interfere to
form the desired grating structure. During the recording process,
the monomers polymerize and the PDLC mixture undergoes a phase
separation, creating regions densely populated by liquid crystal
micro-droplets, interspersed with regions of clear polymer. The
alternating liquid crystal-rich and liquid crystal-depleted regions
form the fringe planes of the grating. The resulting Bragg grating
can exhibit very high diffraction efficiency, which may be
controlled by the magnitude of the electric field applied across
the PDLC layer. In the absence of an applied electric field the SBG
remains in its diffracting state. When an electric field is applied
to the hologram via the electrodes, the natural orientation of the
LC droplets is changed thus reducing the refractive index
modulation of the fringes and causing the hologram diffraction
efficiency to drop to very low levels. The diffraction efficiency
of the device can be adjusted, by means of the applied voltage,
over a continuous range from essentially zero to near 100%. U.S.
Pat. No. 5,942,157 by Sutherland et al. and U.S. Pat. No. 5,751,452
by Tanaka et al. describe monomer and liquid crystal material
combinations suitable for fabricating SBG devices.
[0009] There is a requirement for a compact, lightweight wearable
data display providing a high brightness, high contrast information
display with a high degree of transparency to external light.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a
compact, lightweight wearable data display providing high
brightness and high contrast information visibility with a high
degree of transparency to external light.
[0011] The objects of the invention are achieved in a first
embodiment in which there is provided a transparent wearable data
display comprising: a source; a means of collimating light from the
source; a means for deflecting the collimated light into a scanned
beam; a first array comprising one column containing N switchable
grating elements sandwiched between first and second parallel
transparent substrates, the substrates together functioning as a
first light guide; a second array comprising integer M columns and
integer N rows of switchable grating elements sandwiched between
third and fourth parallel transparent substrates, the substrates
together functioning as a second light guide. Transparent
electrodes are applied to the first and second and the third and
fourth substrates. Each switchable grating element has a
diffracting state and a non diffracting state. The apparatus
further comprises a first coupling means for directing the scanned
beam into a first total internal reflection (TIR) light path
between the outer surfaces of the first lightguide along the first
array column; and a second coupling means linking each element of
the first array to the first element of a row of elements of the
second array. Each element of the first array when in its
diffracting state directing light via the second coupling means
into a second TIR path along a row of the second array for
directing the first TIR light into a second TIR path between the
outer surfaces of the second lightguide along a row of elements of
the second array. At least one of said electrodes of the first
array is patterned into 1.times.N independently switchable elements
each element overlapping one of the first array grating elements.
At least one of the electrodes of said second array is patterned
into M.times.N independently switchable elements, each element
overlapping one of the second array grating elements. In one
embodiment of the invention each element of the first array is
disposed adjacent to a first element of a row of said second
array.
[0012] In one embodiment of the invention each switchable grating
element has a diffracting state when no electric field is applied
across the electrodes sandwiching the grating element and a non
diffracting state when a field is applied across the electrodes.
Each element of the first array when in its diffracting state
directs light from the first TIR path into the second TIR path
starting at the first element of a row of elements of the second
array and proceeding along said row. In one embodiment of the
invention the elements of said first array are switched
sequentially into their diffracting states. In one embodiment of
the invention the elements of rows of the second array adjacent an
element of the first array in its diffracting state are switched
sequentially into their diffracting states. Each element of the
second array when in its diffracting state deflects light through
the fourth substrate.
[0013] In one embodiment of the invention each grating element of
the second array encodes image information.
[0014] In one embodiment of the invention the outer surface of the
fourth substrate faces a viewer of the display.
[0015] In one embodiment of the invention an element of the second
array in its diffracting state forms an image of the information
encoded within the grating element at a predefined viewing range
and an angular bearing defined by the sweep angles of the scanned
beam at.
[0016] In one embodiment of the invention the substrates of the
first array are parallel to the substrates of the second array.
[0017] In one embodiment of the invention the substrates of the
first array are orthogonal to the substrates of the second
array.
[0018] In one embodiment of the invention the first coupling means
is a grating device.
[0019] In one embodiment of the invention the second coupling means
is a grating device abutting each of the first and second
arrays.
[0020] In one embodiment of the invention each switchable grating
element of the output array is divided into independently
switchable columns aligned orthogonally to the TIR path direction
in the output array.
[0021] In one embodiment of the invention a switchable grating is a
Switchable Bragg Grating (SBG).
[0022] In one embodiment of the invention the scanned beam is
characterised by angular deflections in two orthogonal
directions.
[0023] In one embodiment of the invention the intensity of the
scanned beam is modulated by varying the refractive index
modulation of at least one of the switchable grating elements
traversed by the beam.
[0024] In one embodiment of the invention the source of collimated
light provides first, second and third wavelength light.
[0025] In one embodiment of the invention the source of collimated
light provides comprises first second and third wavelength light
and each switchable grating element is a multiplexed SBG comprising
a first grating for diffracting first wavelength light and a second
grating for diffracting second and third wavelength light.
[0026] In one embodiment of the invention the source of collimated
light provides comprises first second and third wavelength light
and each switchable grating element is a multiplexed SBG comprising
a first grating for diffracting first wavelength light, a second
grating for diffracting second wavelength light and a third grating
for diffracting third wavelength light.
[0027] In one embodiment of the invention a switchable grating
element comprises a surface relief grating backfilled with an
electrically variable refractive index medium.
[0028] In one embodiment of the invention each switchable grating
element in at least one of the first array and second array is
divided into independently switchable columns aligned orthogonally
to the TIR paths. The refractive index modulation of each
switchable column is dynamically controlled such that a
predetermined amount of light is diffracted by the switchable
column through the fourth substrate.
[0029] In one embodiment of the invention N is equal to 4 and M is
equal to 4.
[0030] In one embodiment of the invention the data display is one
of an identical pair of left and right eyepieces.
[0031] In one embodiment of the invention the means for providing a
scanned beam comprises: a first transparent optical substrate with
an input surface and an output surface; a second transparent
optical substrate with an input surface and an output surface;
transparent electrodes applied to the output surface of the first
substrate and the input surface of the second substrate; an
electrically variable refractive index layer having a planar
surface and a second surface shaped to provide an array of prisms;
and a fixed refractive index layer having a planar surface and a
second surface shaped to provide an array of prismatic cavities.
The prisms and prismatic cavities have identical and opposing
geometries, each prism abutting one of said prismatic cavities. The
planar surface of the variable refractive index layer abuts the
output surface of the first substrate and the planar surface of the
fixed refractive index layer abuts the input surface of the second
substrate. The transparent electrodes are electrically coupled to a
variable voltage generating means. At least one of the transparent
electrodes is patterned into independently switchable electrode
elements having substantially the same cross sectional area as the
prisms such that said the refractive index prisms may be
selectively switched in discrete steps from a fully diffracting to
a non diffracting state by an electric field applied across the
transparent electrodes.
[0032] A more complete understanding of the invention can be
obtained by considering the following detailed description in
conjunction with the accompanying drawings, wherein like index
numerals indicate like parts. For purposes of clarity, details
relating to technical material that is known in the technical
fields related to the invention have not been described in
detail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a schematic front elevation view of a wearable
display in a first embodiment of the invention.
[0034] FIG. 2 is a schematic cross-sectional view of a wearable
display in a first embodiment of the invention.
[0035] FIG. 3A is a schematic front elevation view of a switchable
grating element in a first embodiment of the invention.
[0036] FIG. 3A is a schematic cross-sectional view of a switchable
grating element in a first embodiment of the invention.
[0037] FIG. 4A is a schematic cross-sectional view of a switchable
grating element in a first embodiment of the invention.
[0038] FIG. 4B is a schematic front elevation view of a switchable
grating element in a first embodiment of the invention.
[0039] FIG. 5 is a schematic plan view of an illumination source in
one embodiment of the invention.
[0040] FIG. 6 is a schematic cross-sectional view of a portion of a
wearable display in one embodiment of the invention.
[0041] FIG. 7 is an example of a image provided in one embodiment
of the invention.
[0042] FIG. 8 is a schematic cross-section view of a wearable
display eyepiece in one embodiment of the invention.
[0043] FIG. 9 is a schematic illustration showing the subdivision
of grating elements into column shaped elements in one embodiment
of the invention.
[0044] FIG. 10 is a schematic illustration showing the subdivision
of grating elements into column shaped elements in one embodiment
of the invention.
[0045] FIG. 11 is a schematic cross-sectional view of a portion of
a grating element subdivided into column elements showing the
diffraction of TIR light.
[0046] FIG. 12 is a schematic front elevation view of a wearable
display in one embodiment of the invention.
[0047] FIG. 13 is a schematic cross-sectional view of a wearable
display in one embodiment of the invention.
[0048] FIG. 14 is a schematic cross-sectional view of a wearable
display in one embodiment of the invention.
[0049] FIG. 15 is a schematic cross-sectional view of a portion of
a wearable display in one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0050] The invention will now be further described by way of
example only with reference to the accompanying drawings.
[0051] It will apparent to those skilled in the art that the
present invention may be practiced with some or all of the present
invention as disclosed in the following description. For the
purposes of explaining the invention well-known features of optical
technology known to those skilled in the art of optical design and
visual displays have been omitted or simplified in order not to
obscure the basic principles of the invention.
[0052] Unless otherwise stated the term "on-axis" in relation to a
ray or a beam direction refers to propagation parallel to an axis
normal to the surfaces of the optical components described in
relation to the invention. In the following description the terms
light, ray, beam and direction may be used interchangeably and in
association with each other to indicate the direction of
propagation of light energy along rectilinear trajectories.
[0053] Parts of the following description will be presented using
terminology commonly employed by those skilled in the art of
optical design.
[0054] It should also be noted that in the following description of
the invention repeated usage of the phrase "in one embodiment" does
not necessarily refer to the same embodiment.
[0055] In a first embodiment of the invention illustrated in the
schematic front elevation view of FIG. 1 there is provided a
transparent wearable data display comprising: an illumination
source 1, a first switchable grating array 2 and a second
switchable grating array 3. The display provides an eyepiece that
may be one of pair of identical elements used in a binocular
display. Alternatively the display may simply provide a monocular
eyepiece. The illumination source which will be discussed in more
detail later in the description comprises a light source, a means
for collimating the light; and a means for deflecting the
collimated light into a scanned beam. Desirably, the source is a
laser. The first array 2 comprises one column and integer number N
switchable grating elements (1.times.N) sandwiched between first
and second parallel transparent substrates 25,26. The substrates
25,26 together function as a first light guide. The second array
comprises M columns and N rows of switchable grating elements
sandwiched between third and fourth parallel transparent substrates
30,31. The substrates 30,31 together function as a second light
guide. The substrates 30,31 are in orthogonal planes to those of
25,26. Transparent electrodes which are not illustrated are applied
to the first and second and the third and fourth substrates.
Advantageously the electrodes are applied to opposing faces of the
substrates. The electrodes are configured such that the applied
electric field will be perpendicular to the substrates. The
electrodes would typically be fabricated from Indium Tin Oxide
(ITO). In one embodiment of the invention the outer surface of the
fourth substrate faces a viewer of the display.
[0056] In one embodiment of the invention the switchable grating is
a Switchable Bragg Grating (SBG).
[0057] In the embodiment of FIG. 1 the integer M is equal to 4 and
N is equal to 4 in other words the first array is a 1.times.4 array
and the second array is a 4.times.4 array. The invention does not
assume any particular value for M or N.
[0058] The illumination source further comprises a first coupling
means for directing the scanned beam into a first TIR light path
between the outer surfaces of the first lightguide along the first
array column. There is further provided a second coupling means 16
for directing the first TIR light into a second TIR path between
the outer surfaces of the second lightguide along a row of elements
of the second array. In one embodiment of the invention the first
coupling means is a grating device. In one embodiment of the
invention the second coupling means is a grating device abutting
each of the first and second arrays as indicated in FIG. 1.
[0059] At least one of said electrodes of the first array is
patterned into 1.times.N independently switchable elements each
element overlapping one of the first array grating elements. At
least one of the electrodes of said second array is patterned into
M.times.N independently switchable elements each element
overlapping one of the second array grating elements. Again we will
assume M=4 and N=4.
[0060] In one embodiment of the invention each element of the first
array is disposed adjacent to a first element of a row of said
second array. Each switchable grating element has a diffracting
state when no electric field is applied across the electrodes
sandwiching the grating element and a non diffracting state when a
field is applied across the electrodes. Each element of the first
array when in its diffracting state directs light from the first
TIR path into the second TIR path starting at the first element of
a row of elements of the second array and proceeding along said
row.
[0061] In one embodiment of the invention the elements of said
first array are switched sequentially into their diffracting
states. The elements of rows of the second array adjacent an
element of the first array in its diffracting state are switched
sequentially into their diffracting states. Each element of the
second array when in its diffracting state deflects light through
the fourth substrate towards the eye of the user of the display.
The rows of the second array are switched sequentially. For
example, in FIG. 1 the switchable grating elements of the first
array are indicated by 24A-24D with the element 24B being indicated
as being in its diffracting state by a dashed line. The diffracted
light 102R,102G,102B is diffracted into the row of elements 11A-11D
of the second array starting at element 11A. Input colour
sequential red, green blue light from the light source 40 is
indicated by the rays 100R,100G,100B. It should be noted that the
light is in collimated spaced throughout the optical process to be
described. The rays are coupled into the first array lightguide
into the TIR paths 101R,101G,101B which are coupled the TIR paths
indicated by the rays 102R,102G,102B along the row of elements
11A-11B by the grating element 24B which is in its active
state.
[0062] FIG. 2 is a schematic cross-sectional view of the display
showing the input array and the output array. The switchable
grating element 24B of the first array and the row of switchable
grating elements 11A-11B of the second array are illustrated. Only
the red TIR path 102R is illustrated.
[0063] In one embodiment of the invention each grating element of
the second array encodes image information. For the purpose of
understanding the invention this image information may comprise a
binary dot pattern or a symbol where the dots or symbols comprise
regions of material into which gratings have been recorded
surrounded by regions containing no gratings. In other words when
illuminated by collimated light and in its diffracting state the
grating element diffracts the light to form an image corresponding
to said image information. In one embodiment of the invention an
element of the second array in its diffracting state forms an image
of the information encoded within the grating element at a
predefined viewing range and an angular bearing defined by the
instantaneous deflection angles of the scanned beam. The encoded
information may comprise a numeric symbol or a portion of a numeric
symbol. The information may be a gray level pixel. The information
may be a binary pixel or symbol characterised solely by "on" and
"off" states. In other embodiments of the invention the information
may provide a three dimensional or holographic image when the
grating element is in its diffracting state. The invention does not
assume any particular type of image information.
[0064] In one embodiment of the invention the source of collimated
light provides color sequential red, green and blue illumination
and each switchable grating element is a multiplexed Bragg grating
comprising a first grating for diffracting red light and a second
grating for diffracting blue and green light.
[0065] FIG. 3 illustrates the elements of the first array in more
detail. FIG. 3A is a schematic plan view of a grating element of
the first array. The grating contains two multiplexed gratings
having slant angles in the YX plane. The fringes 22A, 22B from the
first grating and the fringes as 23A, 23B in the second grating are
indicated. The same fringes are shown in the orthogonal YZ plane in
FIG. 3B.
[0066] FIG. 4 illustrates the elements of the second array in more
detail. FIG. 3A is a schematic cross sectional view of a switchable
grating element of the second array. The grating contains two
multiplexed gratings having slant angles in the ZX plane. The
fringes 32A, 32B from the first grating and the fringes as 33A, 33B
in the second grating are indicated. The same fringes are shown in
the orthogonal YX plane in FIG. 4B.
[0067] In a further embodiment of the invention based on the
embodiment of FIGS. 3-4 the switchable grating multiplexes separate
red, green and blue diffracting Bragg gratings.
[0068] It should be apparent from consideration of FIGS. 3-4 that
the invention may provide a monochrome display by recording a
single monochrome grating within each switchable grating element.
Further, since the display is fundamentally transparent red green
and blue diffracting arrays may be stacked to provide a colour
display. However such an implementation of the invention would
suffer from increased thickness.
[0069] FIG. 5 is a schematic plan view of an illumination source in
one embodiment of the invention comprising a laser module emitting
red, green and blue collimated light 110R,110G,110B, a scanner 42
providing the scanned beams 111R,111G,111B, and angular sweep
expansion means 43 providing the beams 112R,112G,112B and a grating
coupler 44 (essentially the first coupling means discussed above)
for deflecting scanned beams 113R,113G,113B into a TIR path insider
the lightguide formed by the first array. The angular sweep
expansion means may comprise an a focal system of lenses or other
equivalent means known to those skilled in the art of optical
design. The invention does not assume any particular configuration
of the grating coupler with respect to the first array and many
alternative schemes should be apparent to those skilled in the art
of optical design. The grating coupler may employ any known grating
technology. In a typical eyeglass where the display provides left
and right eyepieces it would be ergonomically advantageous to
integrate the illumination source within the arms of the
spectacles.
[0070] In one embodiment of the invention the scanned beams are
characterised by angular deflections in two orthogonal directions
which advantageously correspond to the Y and X coordinate
directions indicated in FIG. 1. Techniques for scanning a beam in
orthogonal direction are well documented in the prior art.
[0071] The invention does not assume any particular beam scanning
method. Advantageously the scanner will be an electro optical
device However, devices based on piezoelectric deflectors and micro
electro mechanical systems (MEMS) may be also considered. Separate
scanners may be provided for red, green and blue light.
Alternatively, a single scanner operating on colour sequential
light from separate red green and blue sources may be used. The
relative merits of such technologies in terms of scanning speed,
optical efficiency, physical robustness, size and cost should be
apparent to those skilled in the art of optical design.
[0072] In one embodiment of the invention, the scanner is similar
to the electro optical micro scanner disclosed in U.S. Provisional
Patent Application No. 61/457,835 by the present inventors with
filing date 16 Jun. 2011 entitled HOLOGRAPHIC BEAM STEERING DEVICE
FOR AUTOSTEREOSCOPIC DISPLAYS. The micro scanner described in that
reference comprises: a first transparent optical substrate with an
input surface and an output surface; a second transparent optical
substrate with an input surface and an output surface; transparent
electrodes applied to the output surface of the first substrate and
the input surface of the second substrate; an electrically variable
refractive index layer having a planar surface and a second surface
shaped to provide an array of prisms; and a fixed refractive index
layer having a planar surface and a second surface shaped to
provide an array of prismatic cavities. The prisms and prismatic
cavities have identical and opposing geometries, each prism
abutting one of the prismatic cavities. The planar surface of the
variable refractive index layer abuts the output surface of the
first substrate and the planar surface of the fixed refractive
index layer abuts the input surface of the second substrate. The
transparent electrodes are electrically coupled to a variable
voltage generating means. At least one of the transparent
electrodes is patterned into independently switchable electrode
elements having substantially the same cross sectional area as the
prisms such that the refractive index prisms may be selectively
switched in discrete steps from a fully diffracting to a non
diffracting state by an electric field applied across the
transparent electrodes.
[0073] In one embodiment of the invention the scanner scans the
light into discrete angular steps. In an alternative embodiment of
the invention the scanner scans the light in continuous sweeps. In
one embodiment of the invention the intensity of the scanned beam
is modulated by varying the refractive index modulation of at least
one of the switchable grating elements traversed by the beam.
Advantageously the elements of the first array are used to modulate
the beam. However, it will be apparent from consideration of the
description and drawings that other modulation schemes based on
varying the refractive index modulation of any of the grating
elements along the beam path from the light source to the output
surface of the display may be used.
[0074] The formation of a viewable image by the display is
illustrated in more detail in FIGS. 6-7. In a typical application
of the invention the viewable image is overlaid on the external
scene in the manner of a Heads Up Display (HUD). FIG. 7 is a
schematic cross-sectional view of a portion of the second array
including the grating elements 11A-11C (see FIGS. 1-2). The element
11C is in its diffracting state. A voltage source for applying a
voltage across each grating element is indicated by 5 and the
circuit connection to the switching electrodes across the grating
element is indicated by 51. Typically, an active matrix switching
scheme would be used to control the voltages applied to the first
and second arrays. The TIR path of the illumination light at one
point in the beam angular sweep is indicated by the rays
114R,114G,114B. The light deflected out of the display at one
extreme of the beam angular sweep is indicated by rays
115R,115G,115B and at the other extreme of the beam angular sweep
by the rays 116R,116G,116B. The output light forms a virtual image
111 at infinity. It should be apparent from consideration of FIG. 6
that by scanning the beam in the X and Y directions and modulating
the voltage applied across the active grating element a symbol
image such as the one illustrated in FIG. 7 may be written. The
symbol image comprises bright pixels 113 and dark pixels 114. In
this case the voltage modulation as indicated by the chart 52
showing voltage V plotted against time t would have a binary
waveform represented by the characteristic 53. The output light is
viewed through the pupil 112. It should be noted that each element
of the second array requires a unique prescription to that all
light diffracted out of the eye glass passes through an exit pupil
through which the eye may observe the entire displayed image. It
should be apparent that by switching the voltage to provide grey
levels and taking advantage of the colour gamut provided by the
red, green blue illumination more complex images may be
generated.
[0075] FIG. 8 is a schematic side elevation view of the display 15
in relation to the observer eye 17 in one embodiment of the
invention, showing the angular extent of the display data in
relation to the overall field of view defined by the physical
aperture of the display. The limiting rays defining the overall
field of view are illustrated by 115A,115B. The rays 116A.116b
define the vertical extent of the displayed data. In typical
applications such as data displays for sports it is desirable to
project data into the lower portion of the field of view. The data
may extend across the full horizontal field if necessary.
[0076] In one embodiment of the invention each switchable grating
element in at least one of the input and output arrays is divided
into independently switchable columns, aligned orthogonally to the
TIR paths. FIG. 9 provides a front elevation of view of the
elements 11A-11D of the second array. One column of the grating
element 11A is indicated by the numeral 13. The invention does not
place any restrictions on the width of and number of column
elements in a column. The refractive index modulation of each
switchable column is dynamically controlled by active matrix
voltage control circuitry which is not illustrated. The refractive
index modulation within a column can be set by the SBG recording
conditions or can be varied dynamically by modulating each column
in synchronization with the scanning of the input light.
Alternatively, a combination of fixed and dynamic index modulation
may be used.
[0077] The columns maximise the extraction of light from the
lightguide by diffracting a predetermined amount of light from an
active column out of the display towards the eye. Non-diffracted or
zero-order light which would otherwise be confined to the
lightguide by TIR is depleted in small steps each time the beam
interacts with a column until all of the light has been extracted.
In other applications of diffractive optical elements zero-order
light is treated as a loss. However, in the present application the
zero order light is recycled to allow uniform out-coupling of TIR
light. The diffraction efficiency of individual column elements is
controlled by adjusting the index modulation in synchronisation
with the beam scanning.
[0078] In the embodiment of the invention illustrated in FIG. 9 the
grating elements are identical in size and contain equal numbers of
columns. The use of columns elements as described above allows the
grating element widths to vary across an array row as in the case
of the grating elements indicated by 11E-11H in FIG. 10. The
grating elements widths may be varied dynamically to match the
extraction efficiency to the time varying beam angle. This
overcomes the problem that TIR rays with incidence angles that do
not meet the exact Bragg condition (off-Bragg rays) are diffracted
with progressively diminishing efficiency as the angle increases up
to the angular bandwidth limit, requiring more bounces before the
beam or an acceptable portion of the beam is ejected from the
lightguide.
[0079] FIG. 11 is a schematic plan view of a portion of the grating
element 11a illustrating the propagation of TIR light through the
columns labelled by 13A-13C. The TIR path light inside the light
guide is indicated by the ray 102R. The diffraction efficiencies of
the column elements 13A,13B,13C for rays meeting the exact Bragg
diffraction angle (referred to as on-Bragg rays) are k,k',k''
respectively. If the TIR light is injected into the lightguide with
power P.sub.0 the power diffracted at element 13A is kP.sub.0 in to
the ray direction 102RA. The power diffracted at the element 13B is
k'(1-k)P.sub.0 into the ray direction 102RB and so on until most of
the beam power has been extracted and the output light is
distributed over the ray directions generally indicated by 120R.
The k factors are specified to give a fixed light output at each
bounce of the TIR beam ensuring a uniform light distribution across
the exit pupil of the display. Other light distributions maybe
obtained by suitable specification of the k-factors.
[0080] In embodiments of the invention using the switchable column
principle described above the grating element is no longer a fixed
functional element of the display as discussed in relation to the
embodiments of FIGS. 1-8. The term now describes the instantaneous
extent of the set of columns over which extraction of the light
corresponds to a defined image element (pixel) takes place. In
addition to maximising the extraction of light from the display the
switchable columns principle also allow the output put light to be
distributed uniformly over the exit pupil. Furthermore, the
switchable column principle allow the size of the exit pupil to be
expanded by using a sufficiently large subset of columns and
matching the column prescriptions to the scanned beam ray
directions. Switchable column designs for use with the present
invention may be based on the embodiments and teachings disclosed
in the U.S. Provisional Patent Application No. 61/457,835 with
filing date 16 Jun. 2011 entitled HOLOGRAPHIC BEAM STEERING DEVICE
FOR AUTOSTEREOSCOPIC DISPLAYS which is incorporated by reference
herein in its entirety.
[0081] In the embodiment of FIG. 1 the first array is orthogonal
the second array. In an alternative embodiment of the invention
illustrated in FIGS. 12-15 the substrates of the first array are
parallel to the substrates of the second array. The advantage of
such a configuration which will now be discussed with reference to
FIGS. 12-15 is that the first and second arrays may share common
substrates and transparent electrode layers avoiding the
fabrication problems of aligning the first and second arrays. Again
the drawings are referred to the coordinate system defined by the
axes labelled XYZ. FIG. 12 is a schematic front elevation view of
the display showing the illumination source 1 the first array 6
which further comprises the elements 24A-24D and the second array
3. The illumination source and second array are unchanged from the
embodiment of FIG. 1. FIG. 13 is a schematic cross-sectional view
of the first and second arrays showing the propagation of red beam.
FIG. 14 is a schematic cross sectional view of the first array 6 in
the ZY plane. FIG. 15 is schematic cross sectional view of the
first array in the ZX plane. The first and second arrays may abut
as shown in FIG. 13. In alternative embodiments of the invention
the first and second arrays may sandwich an air gap or a slab of
transparent material. Turning now to FIG. 13 we see that the first
and second arrays are sandwiched by the substrates 30,31 to which
transparent electrodes (not illustrated) are applied on opposing
faces. The first array grating element 24B and the second array
gratings elements 11A-11D are indicated. A passive grating device
comprises a grating 29B sandwiched by substrates 28A,28B abuts the
substrate 30 overlapping the element 24A. As indicated in FIG. 14
the passive grating device extends over the entire length of the
first array. Although the passive grating is illustrated as four
distinct elements 29A-29D in FIG. 13 the grating will typically
have a uniform prescription along its length. The illumination
source injects colour-sequential TIR light 121R,121G,121B into the
lightguide formed by the first array substrates which is diffracted
by the active element 24B into the ray directions 122R,122G,122B.
The passive grating diffracts the light which is totally internally
reflected at the outer surface of the substrate 28B as represented
by the ray paths 123R,124R lying in the plane ZY in FIG. 12 and
FIG. 14. The light then proceeds to follow the TIR path 102R within
the second array. At least one of the first or second arrays may
use the column element scheme described earlier.
[0082] In one embodiment of the invention a switchable grating
element according to the principles of the invention is a surface
relief grating backfilled with an electrically variable refractive
index medium based on the embodiments and teachings disclosed in
the United States Provisional Patent Application No. 61/457,835
with filing date 16 Jun. 2011 entitled HOLOGRAPHIC BEAM STEERING
DEVICE FOR AUTOSTEREOSCOPIC DISPLAYS which is incorporated by
reference herein in its entirety.
[0083] In order to ensure high transparency to external light, high
contrast of displayed data (ie high diffraction efficiency) and
very low haze due to scatter the following material characteristics
are desirable. A low index-modulation residual grating, with a
modulation not greater than 0.007, is desirable. This will require
a good match between the refractive index of the polymer region and
the ordinary index of the liquid crystal. The material should have
a high index modulation capability with a refractive index
modulation not less than 0.06. The material should exhibit very low
haze for HPDLC cell thicknesses in the range 2-6 micron. The HPDLC
should have a good index match (to within +0.015) for glass or
plastic at 630 nm. One option is 1.515 (for example, 1737F or BK7
glasses). An alternative option would be 1.472 (for example
Borofloat or 7740 Pyrex glasses).
[0084] Desirably the light sources are solid-state lasers. The low
etendue of lasers results in considerable simplification of the
optics. LEDs may also be used with the invention. However, LEDs
suffer from large etendue, inefficient light collection and complex
illuminator and projection optics. A further disadvantage with
regard to SBGs is that LEDs are fundamentally unpolarized.
[0085] Any display device using lasers will tend to suffer from
speckle. The present invention may incorporate any type of
despeckler. Advantageously, the despeckler would be based on
electro-optical principles. A despeckler for use with the present
invention may be based on the disclosed embodiments and teachings
of PCT Application No.: US2008/001909, with International Filing
Date: 22 Jul. 2008, entitled LASER ILLUMINATION DEVICE. and PCT
Application No.: PCT/GB2010/002023 filed on 2 Nov. 2010 by the
present inventors entitled APPARATUS FOR REDUCING LASER SPECKLE
each of which is incorporated by reference herein in its entirety.
The need for a despeckler may be eliminated by using a miniature,
broadband (4 nm) ROB lasers of the type supplied by Epicrystal
Inc.
[0086] Speckle arising from laser sources can be reduced by
applying decorrelation procedures based on combining multiple sets
of speckle patterns or cells from a given speckle-generating
surface during the spatio-temporal resolution of the human eye.
Desirably the despeckler is an electro-optical device configured to
generate set of unique speckle phase cells by operating on the
angular or polarization characteristic of rays propagating through
the device. Furthermore, the despeckler device may be configured in
several different ways to operate on one of more of the phase, and
ray angular characteristics of incoming light. The invention does
not rely on any particular despeckler technology. Any method for
generating and averaging speckle cells may be used with the
invention. However, solid-state methods using SBGs offer more scope
for miniaturization of the illuminator module.
[0087] The optical design of a wearable display according to the
principles of the invention will be dictated by basic geometrical
considerations well known to those skilled in the art of optical
design. The goal is to maximize eye relief, exit pupil and field of
view. Since these parameters will impact on geometrical
aberrations, dispersion and other factors affecting image quality
some performance versus form factor trade-offs are inevitable. The
preferred light source is a laser. If broadband sources such as
LEDs are used the design will require careful attention to the
correction of chromatic dispersion and monochromatic geometrical
aberrations. Dispersion is a problem for any DOE illuminated by a
broadband source. The degree of defocus or image blur due to
dispersion depends on the source spectral bandwidth and the
distance from the DOE to the virtual image plane. Typically, the
angular blur for a given wavelength and a source spectral bandwidth
will be of the order of the bandwidth divided by the wavelength.
The effect of monochromatic geometrical aberrations will depend on
the field of view and pupil size.
[0088] A wearable display based on any of the above-described
embodiments may be implemented using plastic substrates. Using
sufficiently thin substrates such embodiments could be implemented
as a long clear strip applique running from the nasal to ear ends
of each eyeglass with a small illumination module continuing laser
dies, light guides and display drive chip tucked into the sidewall
of the eyeglass. Standard index matched glue would be used to fix
the display to the surfaces of the eyeglasses. The plastic
substrates may be fabricated from materials such as polycarbonate.
The transparent electrodes may be fabricated from carbon nanotubes
(CNTs) which may be more suitable than ITO for use with flexible
substrates. The display may further comprise an environmental seal.
A plastic SBG for use in the present invention may be based on the
HPDLC material system and processes disclosed in a United States
Provisional Patent Application by the present inventors entitled
IMPROVEMENTS TO HOLOGRAPHIC POLYMER DISPERSED LIQUID CRYSTAL
MATERIALS AND DEVICES for which no filing number is available at
the present but which is referenced by the Applicant's docket
number SBG104 which is incorporated by reference herein in its
entirety.
[0089] Although a planar display element using flat substrates has
been discussed in the above description an eyepiece according to
the principles of the invention may be fabricated using curved
surfaces. The invention the invention may be used to provide a
facetted surface display. In one embodiment of the invention the
switchable gratings are SBGs operated in reverse mode. In reverse
mode the SBG has low diffraction efficiency when no electric field
is applied and has high efficiency when a field is applied. A
reverse mode SBG for use in the present invention may be based on
the HPDLC material system and processes disclosed in U.S.
Provisional Patent Application No. 61/573,066 with filing date 24
Aug. 2011 by the present inventors entitled IMPROVEMENTS TO
HOLOGRAPHIC POLYMER DISPERSED LIQUID CRYSTAL MATERIALS AND DEVICES
which is incorporated by reference herein in its entirety.
[0090] A key feature of all of the embodiments described above is
that they provide the benefit of see-through. The latter is of
great importance in Head Up Displays for automobile, aviation and
other transport applications; private see-through displays such for
security sensitive applications; architectural interior signage and
many other applications. With the addition of a holographic
brightness enhancing film, or other narrow band reflector affixed
to one side of the display, the purpose of which is to reflect the
display illumination wavelength light only, the see-through display
can be made invisible (and hence secure) in the opposite direction
of view. Here the reflected display illumination is effectively
mirrored and therefore blocked in one direction, making it ideal
for transparent desktop display applications in customer or
personal interview settings common in bank or financial services
settings.
[0091] Although the present application addresses wearable displays
it will be clear that in any of the above embodiments the eye lens
and retina may be replaced by any type of imaging lens and a
screen. Any of the above described embodiments of the invention may
be used in either directly viewed or virtual image displays.
Possible applications range from miniature displays such as those
used in viewfinders to large area public information displays. The
above described embodiments may be used in applications where a
transparent display is required. For example the invention may be
used in applications where the displayed imagery is superimposed on
a background scene such as heads up displays and teleprompters. The
invention may be used to provide a display device that is located
at or near to an internal image plane of an optical system. For
example any of the above described embodiments may be used to
provide a symbolic data display for a camera viewfinder in which
symbol data is projected at an intermediate image plane and then
magnified by a viewfinder eyepiece. It will be clear the invention
may be applied in biocular or monocular displays. The invention may
also be used in a stereoscopic wearable display. Any of the above
described embodiments of the invention may be used in a rear
projection television. The invention may be applied in avionic,
industrial and medical displays. There are applications in
entertainment, simulation, virtual reality, training systems and
sport.
[0092] SBG arrays may be fabricated using a diffractive optical
mask formed on a transparent sapphire wafer. The SBG cell optical
prescriptions are defined on a cell to cell basis. The process of
fabricating the SBG array may start with the creation of a
multiphase computer generated hologram encoding the desired optical
functions which is then holographically recorded in the SBG.
[0093] It should be noted that the total internal reflection ray
paths shown in the drawings are meant to be schematic only. The
number of total internal reflections will depend on the scrolling
scheme used and the overall geometry of the light guide formed by
the display layers. Typically, in order to ensure that TIR occurs
the incidence angles must lie in the range of about 42 to about 70
degrees. It should be emphasized that the drawings are exemplary
and that the dimensions have been exaggerated.
[0094] The method of fabricating the SBG pixel elements and the ITO
electrodes used in any of the above-described embodiments of the
invention may be based on the process disclosed in the PCT
Application No.: US2006/043938, claiming priority to U.S.
provisional patent application 60/789,595 filed on 6 Apr. 2006,
entitled METHOD AND APPARATUS FOR PROVIDING A TRANSPARENT DISPLAY,
which is incorporated by reference herein in its entirety.
[0095] The display devices disclosed in the present invention may
employ features of the transparent edge lit display embodiments and
teachings disclosed in U.S. patent application Ser. No. 10/555,661
filed 4 Nov. 2005 entitled SWITCHABLE VIEWFINDER DISPLAY which is
incorporated by reference herein in its entirety.
[0096] The despeckler referred to in the above description may be
based on the disclosed embodiments and teachings of PCT Application
No.: US2008/001909, with International Filing Date: 22 Jul. 2008,
entitled LASER ILLUMINATION DEVICE. and PCT Application No.:
PCT/GB2010/002023 filed on 2 Nov. 2010 by the present inventors
entitled APPARATUS FOR REDUCING LASER SPECKLE each of which is
incorporated by reference herein in its entirety.
[0097] The optical design of the display disclosed in the present
application may be guided by the teachings of PCT Application No.:
PCT/GB2010/001982 entitled COMPACT EDGE ILLUMINATED EYEGLASS
DISPLAY by the present inventors (and also referenced by the
Applicant's docket number SBG081PCT) which is incorporated by
reference herein in its entirety.
[0098] The display disclosed in the present application may
incorporate an eye tracker based on the embodiments and teachings
disclosed in U.S. Provisional Patent Application No. 61/344,748
with filing date 28 Sep. 2010 entitled EYE TRACKED HOLOGRAPHIC EDGE
ILLUMINATED EYEGLASS DISPLAY (and also referenced by the
Applicant's docket number SBG092) which is incorporated by
reference herein in its entirety.
[0099] The means for scanning collimated input light and the column
array technique for improving the light extraction efficiency from
switchable gratings discussed above may be based on the embodiments
and teachings disclosed in the U.S. Provisional Patent Application
No. 61/457,835 with filing date 16 Jun. 2011 entitled HOLOGRAPHIC
BEAM STEERING DEVICE FOR AUTOSTEREOSCOPIC DISPLAYS which is
incorporated by reference herein in its entirety.
[0100] The optical design of display disclosed in the present
application may be guided by the teachings of PCT Application No.:
PCT/GB2010/000835 with International Filing Date: 26 Apr. 2010
entitled COMPACT HOLOGRAPHIC EDGE ILLUMINATED EYEGLASS DISPLAY
which is incorporated by reference herein in its entirety, which
discloses eyeglass display architectures based on a light guiding
eyepiece in which a two dimension array of SBG deflectors is
combined with an input beam.
[0101] The display disclosed in the present application may
fabricated using the HPDLC material system and processes disclosed
in a U.S. Provisional Patent Application No. 61/573,066 with filing
date 24 Aug. 2011 by the present inventors entitled IMPROVEMENTS TO
HOLOGRAPHIC POLYMER DISPERSED LIQUID CRYSTAL MATERIALS AND DEVICES
which is incorporated by reference herein in its entirety.
[0102] It should be understood by those skilled in the art that
while the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. Various
modifications, combinations, sub-combinations and alterations may
occur depending on design requirements and other factors insofar as
they are within the scope of the appended claims or the equivalents
thereof.
* * * * *