U.S. patent application number 16/204853 was filed with the patent office on 2019-05-30 for systems, devices, and methods for aperture-free hologram recording.
The applicant listed for this patent is NORTH INC.. Invention is credited to John Cormier.
Application Number | 20190163128 16/204853 |
Document ID | / |
Family ID | 66632290 |
Filed Date | 2019-05-30 |
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United States Patent
Application |
20190163128 |
Kind Code |
A1 |
Cormier; John |
May 30, 2019 |
SYSTEMS, DEVICES, AND METHODS FOR APERTURE-FREE HOLOGRAM
RECORDING
Abstract
Systems, devices, and methods for aperture-free hologram
recording are described. The apertures typically used for hologram
recording create unwanted secondary holograms by diffracting light.
Aperture-free hologram recording eliminates these unwanted
secondary holograms. Aperture-free hologram recording includes
applying a mask to the holographic recording medium. The mask
controls the size of the recorded hologram like an aperture but
does not create unwanted secondary holograms. Hologram fringes are
only present in the desired recording area and a thin boundary
region. The mask may be present during recording, or the mask may
be used to pre-bleach the holographic recording medium.
Pre-bleaching the holographic recording medium renders a portion of
the holographic recording medium insensitive to light, the hologram
is recorded in the light-sensitive portions of the holographic
recording medium.
Inventors: |
Cormier; John; (Waterloo,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NORTH INC. |
Kitchener |
|
CA |
|
|
Family ID: |
66632290 |
Appl. No.: |
16/204853 |
Filed: |
November 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62593073 |
Nov 30, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03H 1/181 20130101;
G03H 2001/0212 20130101; G03H 2001/266 20130101; G03H 1/0248
20130101; G03H 2260/34 20130101; G02B 27/0172 20130101; G03H 1/0236
20130101; G03H 2270/21 20130101; G03H 1/0486 20130101; G03H
2001/0264 20130101; G02B 2027/0109 20130101; G02B 2027/0178
20130101; G03H 1/265 20130101; G03H 2260/12 20130101; G03H 2270/55
20130101; G03H 2001/0415 20130101; G03H 1/0252 20130101; G03H
2222/13 20130101; G03H 2222/16 20130101; G03H 2222/12 20130101;
G02B 2027/0105 20130101; G02B 27/0103 20130101; G02B 2027/0174
20130101 |
International
Class: |
G03H 1/02 20060101
G03H001/02; G02B 27/01 20060101 G02B027/01; G03H 1/26 20060101
G03H001/26 |
Claims
1. A method of fabricating a holographic recording medium ("HRM"),
the method comprising: applying a mask to a layer of holographic
material, the mask comprising: at least one obstructive area
wherein the at least one obstructive area is configured to shield a
portion of the layer of holographic material from light exposure;
and at least one permissive area wherein the at least one
permissive area is configured to expose a portion of the layer of
holographic material to light; bleaching the masked layer of
holographic material, wherein bleaching the masked layer of
holographic material includes exposing the at least one permissive
area of the mask to light; and removing the mask from the layer of
holographic material.
2. The method of claim 1 wherein the layer of holographic material
comprises a front surface and a back surface, and wherein applying
a mask to the layer of holographic material includes: applying a
front mask to the front surface of the layer of holographic
material, wherein the front mask comprises at least one permissive
area and at least one obstructive area; and applying a back mask to
the back surface of the layer of holographic material, wherein the
back mask comprises a single obstructive area.
3. The method of claim 1 wherein applying a mask to a layer of
holographic material includes applying a mask to a layer of
holographic material wherein the mask includes at least one
obstructive area with a shape selected from a group consisting of:
a circle, an oval, a triangle, a square, a rectangle, a hexagon,
and an octagon.
Description
BACKGROUND
Technical Field
[0001] The present systems, devices, and methods generally relate
to hologram recording and particularly relate to aperture-free
hologram recording.
Description of the Related Art
Holograms
[0002] A hologram is a recording of a light field, with a typical
light field comprising a pattern of optical fringes generated by
two beams of laser light. The hologram is made up of physical
fringes, where physical fringes comprise variations in the
refractive index or absorbance of the holographic recording
medium.
[0003] At least a portion of the light field used to record a
hologram may be recreated by illuminating the hologram with laser
light. If the laser light comprises the same wavelength and angle
as one of the beams of laser light used to record the hologram, the
holographic medium will emit laser light with the same angle and
pattern as the other beam of laser light used to record the
hologram. The intensity of the emitted light is determined by the
efficiency of the hologram, with a higher efficiency hologram
emitting more intense laser light. The efficiency of a hologram
depends on both the angle and the wavelength of light used to
illuminate the holographic medium. Multiple holograms may be
recorded in a single holographic recording medium, the multiple
holograms comprising a multiplexed hologram. A hologram may form a
holographic optical element (HOE), where the hologram refracts,
diffracts, attenuates or otherwise modifies the properties of the
light illuminating the hologram.
Hologram Recording
[0004] A pattern of optical fringes may be generated by the
interference of two beams of laser light; the two beams of laser
light may be created by splitting a single beam of laser light. The
two beams of laser light are typically referred to as the object
beam and the reference beam. Hologram recording is typically
designed such that, during playback, the recorded hologram is
illuminated with laser light recreating the reference beam and the
object beam is then replicated by the hologram.
[0005] Holograms are recorded in a holographic recording medium
which may be a silver halide photographic emulsion, dichromated
gelatin, photopolymer, or other physical media. Silver halide
emulsions record a hologram as a pattern of absorbance and
reflectance of light. Dichromated gelatin and photopolymer both
record a hologram as a pattern of varying refractive index.
Recording a hologram as a pattern of refractive index is
advantageous since all of the illuminating laser light may
theoretically leave the hologram; no light is necessarily absorbed
by the hologram.
Apertures
[0006] A typical hologram recording assembly includes at least one
aperture. An aperture is a device that is placed in the optical
path of the laser light and controls the amount of light that is
able to travel further along the optical path. Apertures may be
used to control the overall intensity of a beam of laser light;
apertures may also control the spot size of the beam of laser
light. In a typical hologram recording assembly, the physical size
of the recorded hologram is determined by the spot size of the
object and reference beams at the holographic recording medium.
[0007] A typical aperture comprises multiple, typically five or six
but possibly more, movable blades. The blades are positioned and
oriented such that they form an approximate circle with a central
gap. The gap is positioned in the path of the beam of laser light
such that at least a portion of the beam of laser light may pass
through the gap. Laser light that impinges on the blades is blocked
and cannot pass any further along the optical path. The size of the
gap may be varied by moving the blades relative to one another. As
the size of the gap varies, the size of the beam of laser light
which may pass through the gap varies.
BRIEF SUMMARY
[0008] A holographic optical element ("HOE") comprising a single
contiguous layer of photopolymer material may be summarized as
including: a recorded area oriented perpendicular to the principal
axis of the HOE wherein the recorded area includes hologram fringes
that define at least one hologram and wherein the hologram fringes
comprise a photopolymer material with a first amount of refractive
index contrast; an unrecorded area oriented perpendicular to the
principal axis of the HOE wherein the unrecorded area comprises
photopolymer material with a uniform refractive index; and a
boundary area oriented perpendicular to the principal axis of the
HOE positioned between the recorded area and the unrecorded area
wherein the boundary area includes hologram fringes comprising a
photopolymer material with a second amount of refractive index
contrast, wherein the second amount of refractive index contrast is
less than the first amount of refractive index contrast, and
wherein the boundary area has a thickness measured in at least one
direction perpendicular to the principal axis of the HOE less than
a thickness of the HOE measured parallel to the principal axis of
the HOE.
[0009] The thickness of the HOE as measured parallel to the
principal axis of the HOE may be selected from a group consisting
of: less than one millimeter, less than one hundred micrometers,
and less than six micrometers. The HOE may further include a
protective layer carried by the photopolymer layer. The HOE may be
curved around a center or axis of curvature located on an eye-side
thereof.
[0010] The HOE may comprise N layers of photopolymer, where N is an
integer greater than or equal to 1, and wherein each of the N
layers of photopolymer includes: a respective one of N recorded
areas, wherein each recorded area includes a respective one of N
sets of hologram fringes that define a respective one of N
holograms wherein each respective set of hologram fringes comprise
a photopolymer material with a respective one of N first amounts of
refractive index contrast; a respective one of N unrecorded areas,
wherein each unrecorded area comprises a photopolymer material with
a uniform refractive index; and a respective one of N boundary
areas, wherein each boundary area is positioned between each
respective recorded area and each respective unrecorded area,
wherein each boundary area includes a respective one of N sets of
secondary hologram fringes comprising a photopolymer material with
a respective one of N second amounts of refractive index contrast,
wherein each second amount of refractive index contrast is less
than each respective first amount of refractive index contrast, and
wherein the thickness of each of the N boundary areas as measured
in at least one direction perpendicular to the principal axis of
the HOE is less than the thickness each respective photopolymer
layer as measured parallel to the principal axis of the HOE. The
recorded area may include M multiplexed holograms, wherein M is an
integer greater than or equal to 1.
[0011] The at least one hologram may comprise a reflection
hologram. The at least one hologram may comprise at least one
angle-multiplexed hologram. The at least one hologram may comprise
at least one wavelength-multiplexed hologram. The at least one
wavelength-multiplexed hologram may comprise a red hologram, a
green hologram, and a blue hologram. The at least one
wavelength-multiplexed hologram may comprise an infrared hologram.
The at least one hologram may comprise a hologram with a
redirection angle greater than 45 degrees. The recorded area may
have a thickness measured in at least one direction perpendicular
to the principal axis of the HOE less than 2 millimeters. The
recorded area may comprise a holographic incoupler.
[0012] A holographic recording medium ("HRM") comprising a single
contiguous layer of holographic material may be summarized as
including: a recording area, wherein in the recording area a
holographic material of the HRM is photopolymerizable to a first
degree; a bleached area, wherein in the bleached area the
holographic material of the HRM is not photopolymerizable; and a
boundary area positioned between the recorded area and the
unrecorded area, wherein in the boundary area the holographic
material of the HRM is photopolymerizable to a second degree,
wherein the first degree to which the holographic material of the
HRM is photopolymerizable in the recording area is higher than the
second degree to which the holographic material of the HRM is
photopolymerizable in the boundary area and wherein the boundary
area has a thickness as measured in at least one direction
perpendicular to the principal axis of the HRM less than the
thickness of the HRM as measured parallel to the principal axis of
the HRM.
[0013] The thickness of the HRM as measured parallel to the
principal axis of the HRM may be selected from a group consisting
of: less than one millimeter, less than one hundred micrometers,
and less than six micrometers. The HRM may further include a
protective layer carried by the holographic material layer. The
protective layer may include a first protective layer and a second
protective layer, wherein the first protective layer and the second
protective layer cover opposing surfaces of the photopolymer layer,
and wherein at least one of the first protective layer and the
second protective layer comprise a provisional protective layer.
The recording area may have a thickness measured in at least one
direction perpendicular to the principal axis of the HOE less than
2 millimeters.
[0014] A method of fabricating a holographic recording medium
("HRM") may be summarized as including: applying a mask to a layer
of holographic material, the mask comprising: at least one
obstructive area wherein the at least one obstructive area is
configured to shield a portion of the layer of holographic material
from light exposure; and at least one permissive area wherein the
at least one permissive area is configured to expose a portion of
the layer of holographic material to light; bleaching the masked
layer of holographic material, wherein bleaching the masked layer
of holographic material includes exposing the at least one
permissive area of the mask to light; and removing the mask from
the layer of holographic material.
[0015] The layer of holographic material may include a front
surface and a back surface, and applying a mask to the layer of
holographic material may include: applying a front mask to the
front surface of the layer of holographic material, wherein the
front mask comprises at least one permissive area and at least one
obstructive area; and applying a back mask to the back surface of
the layer of holographic material, wherein the back mask comprises
a single obstructive area.
[0016] Applying a mask to a layer of holographic material may
include applying a mask to a layer of holographic material wherein
the mask includes at least one obstructive area with a shape
selected from a group consisting of: a circle, an oval, a triangle,
a square, a rectangle, a hexagon, and an octagon.
[0017] A method of recording a hologram may be summarized as
including: mounting a layer of holographic material in an
aperture-free hologram recording assembly; applying a mask to the
layer of holographic material, the mask comprising: at least one
obstructive area wherein the at least one obstructive area is
configured to shield a portion of the layer of holographic material
from light exposure; and at least one permissive area wherein the
at least one permissive area is configured to expose a portion of
the layer of holographic material to light; illuminating the layer
of holographic material with laser light, wherein illuminating the
layer of holographic material with laser light includes routing
laser light from a laser light source along an aperture-free
optical path to the layer of holographic material; removing the
mask from the HRM; and bleaching the HRM.
[0018] Routing the laser light from the laser light source along an
aperture-free optical path to the layer of holographic material may
include: splitting the laser light with a beamsplitter to form an
object beam and a reference beam; collimating the object beam;
routing the object beam to illuminate the layer of holographic
material; collimating the reference beam; and routing the reference
beam to illuminate the layer of holographic material.
[0019] The layer of holographic material may include a front
surface and a back surface, and applying a mask to the layer of
holographic material may include: applying a front mask to the
front surface of the layer of holographic material, wherein the
front mask comprises at least one permissive area and at least one
obstructive area; and applying a back mask to the back surface of
the layer of holographic material, wherein the back mask comprises
at least one permissive area and at least one obstructive area, and
wherein the back mask is positioned and oriented such that: each
permissive area of the back mask is aligned with a respective
permissive area of the front mask along the principal axis of the
layer of holographic material; and each obstructive area of the
back mask is aligned with a respective obstructive area of the
front mask along the principal axis of the layer of holographic
material.
[0020] Applying a front mask to the front surface of the layer of
holographic material may include applying a front mask to the front
surface of the layer of holographic material wherein the front mask
comprises at least one permissive area with a shape selected from a
group consisting of: a circle, an oval, a triangle, a square, a
rectangle, a hexagon, and an octagon; and applying a back mask to
the back surface of the layer of holographic material may include
applying a back mask to the back surface of the layer of
holographic material wherein the back mask comprises at least one
permissive area with a shape chosen from a group consisting of: a
circle, an oval, a triangle, a square, a rectangle, a hexagon, and
an octagon.
[0021] The method may further include: pre-bleaching the layer of
holographic material subsequent to applying a mask to the layer of
holographic material, wherein applying a mask to the layer of
holographic material includes applying a negative mask to the layer
of holographic material. Illuminating the layer of holographic
material with laser light may include illuminating the layer of
holographic material with laser light that comprises N different
wavelengths of laser light, where N is an integer greater than 1.
Illuminating the layer of holographic material with laser light may
include concurrently illuminating a same surface of the layer of
holographic material with both a laser light reference beam and a
laser light object beam.
[0022] Illuminating the layer of holographic material with laser
light may include concurrently illuminating a first surface of the
layer of holographic material with a laser light reference beam and
a second surface of the layer of holographic material with a laser
light object beam, wherein the second surface of the layer of
holographic material is located opposite the first surface of the
layer of holographic material. Illuminating the layer of
holographic material with laser light may include illuminating the
layer of holographic material with at least one laser light
reference beam and at least two laser light object beams.
Illuminating the layer of holographic material with laser light may
include illuminating the layer of holographic material with laser
light generated by a laser light source wherein the laser light
source comprises an aperture. Illuminating the layer of holographic
material with laser light may include illuminating the layer of
holographic material with laser light that comprises N different
angles, where N is an integer greater than 1.
[0023] A method of recording a hologram may be summarized as
including: mounting a layer of holographic material in an
aperture-free hologram recording assembly; applying a mask to the
layer of holographic material, the mask comprising: at least one
obstructive area wherein the at least one obstructive area is
configured to shield a portion of the layer of holographic material
from light exposure; and at least one permissive area wherein the
at least one permissive area is configured to expose a portion of
the layer of holographic material to light; generating a laser
light signal with at least one laser light source; splitting the
laser light signal with a beamsplitter to form an object beam and a
reference beam; routing the object beam to illuminate the layer of
holographic material; shaping the object beam to a desired
cross-section at the layer of holographic material; routing the
reference beam to illuminate the layer of holographic material;
shaping the reference beam to a desired cross-section at the layer
of holographic material; generating a pattern of optical fringes in
at least a portion of the layer of holographic material by a
combination of the reference beam and the object beam; recording
the pattern of optical fringes as a pattern of physical fringes in
at least a portion of the layer of holographic material; removing
the mask from the layer of holographic material; and bleaching the
layer of holographic material.
[0024] The layer of holographic material may include a front
surface and a back surface, and applying a mask to the layer of
holographic material may include: applying a front mask to the
front surface of the layer of holographic material, wherein the
front mask comprises at least one permissive area and at least one
obstructive area; and applying a back mask to the back surface of
the layer of holographic material, wherein the back mask comprises
at least one permissive area and at least one obstructive area, and
wherein the back mask is positioned and oriented such that: each
permissive area of the back mask is aligned with a respective
permissive area of the front mask along the principal axis of the
layer of holographic material; and each obstructive area of the
back mask is aligned with a respective obstructive area of the
front mask along the principal axis of the layer of holographic
material.
[0025] Applying a front mask to the front surface of the layer of
holographic material may include applying a front mask to the front
surface of the layer of holographic material wherein the front mask
comprises at least one permissive area with a shape selected from a
group consisting of: a circle, an oval, a triangle, a square, a
rectangle, a hexagon, and an octagon; and applying a back mask to
the back surface of the layer of holographic material may include
applying a back mask to the back surface of the layer of
holographic material wherein the back mask comprises at least one
permissive area with a shape chosen from a group consisting of: a
circle, an oval, a triangle, a square, a rectangle, a hexagon, and
an octagon. The method may further include: pre-bleaching the layer
of holographic material subsequent to applying a mask to the layer
of holographic material, wherein applying a mask to the layer of
holographic material includes applying a negative mask to the layer
of holographic material.
[0026] Generating a laser light signal may include generating a
laser light signal comprising N wavelengths of laser light, where N
is an integer greater than 1, and generating a pattern of optical
fringes in at least a portion of the layer of holographic material
by a combination of the reference beam and the object beam may
include generating N sub-patterns of optical fringes in at least a
portion of the layer of holographic material by the combination of
the reference beam and the object beam; and recording the pattern
of optical fringes as a pattern of physical fringes in at least a
portion of the layer of holographic material may include recording
the N sub-patterns of optical fringes as N sub-patterns of physical
fringes in at least a portion of the layer of holographic
material.
[0027] Routing the object beam to illuminate the layer of
holographic material may include routing the object beam to
illuminate a first surface of the layer of holographic material,
and routing the reference beam to illuminate the layer of
holographic material may include routing the reference beam to
illuminate the first surface of the layer of holographic material.
Routing the object beam to illuminate the layer of holographic
material may include routing the object beam to illuminate a first
surface of the layer of holographic material, and routing the
reference beam to illuminate the layer of holographic material may
include routing the reference beam to illuminate a second surface
of the layer of holographic material, wherein the first surface of
the layer of holographic material and the second surface of the
layer of holographic material are opposite surfaces of the layer of
holographic material.
[0028] Generating a laser light signal may include generating a
laser light signal with a laser light source wherein the laser
light source comprises an aperture. Generating a laser light signal
may include generating a laser light signal comprising M angles,
where M is an integer greater than 1, and wherein generating a
pattern of optical fringes in at least a portion of the layer of
holographic material by a combination of the reference beam and the
object beam may include generating M sub-patterns of optical
fringes in at least a portion of the layer of holographic material
by the combination of the reference beam and the object beam; and
recording the pattern of optical fringes as a pattern of physical
fringes in at least a portion of the layer of holographic material
may include recording the M sub-patterns of optical fringes as N
sub-patterns of physical fringes in at least a portion of the layer
of holographic material.
[0029] A method of recording a hologram may be summarized as
including: mounting a layer of holographic material in an
aperture-free hologram recording assembly; applying a mask to a
layer of holographic material, the mask comprising: at least one
obstructive area wherein the at least one obstructive area is
configured to shield a portion of the layer of holographic material
from light exposure; and at least one permissive area wherein the
at least one permissive area is configured to expose a portion of
the layer of holographic material to light; generating a laser
light signal with at least one laser light source; splitting the
laser light signal with at least one beamsplitter to form N object
beams and M reference beams, where N and M are both integers that
are greater than or equal to 1; routing the N object beams to
illuminate the layer of holographic material; shaping the N object
beams to N respective cross-sections at the layer of holographic
material; routing the M reference beams to illuminate the layer of
holographic material; and shaping the M reference beams to M
respective cross-sections at the layer of holographic material;
generating a pattern of optical fringes in at least a portion of
the layer of holographic material by a combination of the M
reference beams and the N object beams; recording the pattern of
optical fringes as a pattern of physical fringes in at least a
portion of the layer of holographic material; removing the mask
from the layer of holographic material; and bleaching the layer of
holographic material.
[0030] The method may further include: pre-bleaching the layer of
holographic material subsequent to applying a mask to the layer of
holographic material, wherein applying a mask to the layer of
holographic material includes applying a negative mask to the layer
of holographic material.
[0031] The layer of holographic material may comprise a front
surface and a back surface, and applying a mask to the layer of
holographic material may include: applying a front mask to the
front surface of the layer of holographic material, wherein the
front mask comprises at least one permissive area and at least one
obstructive area; and applying a back mask to the back surface of
the layer of holographic material, wherein the back mask comprises
at least one permissive area and at least one obstructive area, and
wherein the back mask is positioned and oriented such that: each
permissive area of the back mask is aligned with a respective
permissive area of the front mask along the principal axis of the
layer of holographic material; and each obstructive area of the
back mask is aligned with a respective obstructive area of the
front mask along the principal axis of the layer of holographic
material.
[0032] Applying a front mask to the front surface of the layer of
holographic material may include applying a front mask to the front
surface of the layer of holographic material wherein the front mask
comprises at least one permissive area with a shape selected from a
group consisting of: a circle, an oval, a triangle, a square, a
rectangle, a hexagon, and an octagon; and applying a back mask to
the back surface of the layer of holographic material may include
applying a back mask to the back surface of the layer of
holographic material wherein the back mask comprises at least one
permissive area with a shape chosen from a group consisting of: a
circle, an oval, a triangle, a square, a rectangle, a hexagon, and
an octagon.
[0033] Splitting the laser light signal with at least one
beamsplitter to form N object beams and M reference beams may
include splitting the laser light signal to form N object beams
wherein each of the N object beams possesses a different angle than
each of the other N object beams. Splitting the laser light signal
with at least one beamsplitter to form N object beams and M
reference beams may include splitting the laser light signal to
form M reference beams wherein each of the M reference beams
possesses a different angle than each of the other M reference
beams.
[0034] Generating a laser light signal may include generating a
laser light signal comprising L wavelengths of laser light, where L
is an integer greater than 1, and wherein generating a pattern of
optical fringes in at least a portion of the layer of holographic
material by a combination of the M reference beams and the N object
beams may include generating L sub-patterns of optical fringes in
at least a portion of the layer of holographic material for each of
the combinations of the M reference beams and the N object beams;
and recording the pattern of optical fringes as a pattern of
physical fringes in at least a portion of the layer of holographic
material may include recording the L sub-patterns of optical
fringes as L sub-patterns of physical fringes in at least a portion
of the layer of holographic material.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0035] In the drawings, identical reference numbers identify
similar elements or acts. The sizes and relative positions of
elements in the drawings are not necessarily drawn to scale. For
example, the shapes of various elements and angles are not
necessarily drawn to scale, and some of these elements are
arbitrarily enlarged and positioned to improve drawing legibility.
Further, the particular shapes of the elements as drawn are not
necessarily intended to convey any information regarding the actual
shape of the particular elements, and have been solely selected for
ease of recognition in the drawings.
[0036] FIG. 1 is a top-elevational view of typical hologram
recording assembly 100.
[0037] FIG. 2A is a cross-sectional view of HOE 200 in accordance
with the present systems, devices, and methods.
[0038] FIG. 2B is a side elevational view of HOE 200 in accordance
with the present systems, devices, and methods.
[0039] FIG. 3A is a cross-sectional view of HRM 300 in accordance
with the present systems, devices, and methods.
[0040] FIG. 3B is a side elevational view of HRM 300 in accordance
with the present systems, devices, and methods.
[0041] FIG. 4 is a flow-diagram showing a method 400 of fabricating
a HRM in accordance with the present systems, devices, and
methods.
[0042] FIG. 5A is a side elevational view of masked layer of
holographic material 500 in accordance with the present systems,
devices, and methods.
[0043] FIG. 5B is a front elevational view of masked layer of
holographic material 500 in accordance with the present systems,
devices, and methods.
[0044] FIG. 6 is a top-elevational view of aperture-free hologram
recording assembly 600 in accordance with the present systems,
devices, and methods.
[0045] FIG. 7 is a flow-diagram showing a method 700 of recording a
hologram in accordance with the present systems, devices, and
methods.
[0046] FIG. 8 is a flow-diagram showing a method 800 of recording a
hologram in accordance with the present systems, devices, and
methods.
[0047] FIG. 9 is a flow-diagram showing a method 900 of recording a
hologram in accordance with the present systems, devices, and
methods.
[0048] FIG. 10 is a top elevational view of curved HOE 1000 in
accordance with the present systems, devices, and methods.
DETAILED DESCRIPTION
[0049] In the following description, certain specific details are
set forth in order to provide a thorough understanding of various
disclosed embodiments. However, one skilled in the relevant art
will recognize that embodiments may be practiced without one or
more of these specific details, or with other methods, components,
materials, etc. In other instances, well-known structures
associated with portable electronic devices and head-worn devices,
have not been shown or described in detail to avoid unnecessarily
obscuring descriptions of the embodiments.
[0050] Unless the context requires otherwise, throughout the
specification and claims which follow, the word "comprise" and
variations thereof, such as, "comprises" and "comprising" are to be
construed in an open, inclusive sense, that is as "including, but
not limited to."
[0051] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structures, or
characteristics may be combined in any suitable manner in one or
more embodiments.
[0052] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the content clearly dictates otherwise. It should also be noted
that the term "or" is generally employed in its broadest sense,
that is as meaning "and/or" unless the content clearly dictates
otherwise.
[0053] The headings and Abstract of the Disclosure provided herein
are for convenience only and do not interpret the scope or meaning
of the embodiments.
[0054] The various embodiments described herein provide systems,
devices, and methods for aperture-free hologram recording and are
particularly well-suited for use in holographic displays,
particularly holographic displays used in wearable heads-up
displays.
[0055] A typical hologram recording assembly records multiple
unintended holograms within and outside the desired hologram
recording area in addition to recording the intended hologram. The
use of apertures in the hologram recording assembly creates
unintended holograms because apertures diffract and reflect light
and the diffracted and/or reflected light creates additional
patterns of optical fringes. Eliminating apertures from the
hologram recording assembly eliminates the recording of at least
some of the unintended holograms, however apertures perform
important functions during hologram recording and therefore novel
systems, devices, and methods are required to record holograms in
an aperture-free hologram recording assembly.
[0056] A hologram may comprise a holographic optical element HOE.
In some implementations, the HOE may be carried on or by another
structure. For instance, one or more HOEs may be carried on or by a
waveguide or lightguide structure and may serve as, for example, an
in-coupler, out-coupler, or exit pupil expander for such waveguide
or lightguide structure. Thus, for the purposes of the present
systems, device, and methods, including the appended claims, the
term "HOE" includes a diffractive material combined with
waveguide/lightguide structures. Likewise, when the term "HOE" is
used, the HOE may be carried on or by other structures or layers,
or may itself carry other structures or layers, depending on the
specific implementation.
[0057] When a hologram is illuminated with light with a wavelength
and angle matching the reference beam used to record the hologram,
the hologram diffracts the reference beam to create light with a
wavelength and angle matching the object beam used to record the
hologram (i.e. the hologram plays back the reference beam to form
the object beam). The hologram may direct the object beam in one of
two directions. If the light played back travels in the opposite
direction of the reference beam (in other words, the playback light
appears to be reflected by the hologram), the hologram is referred
to as a reflection hologram. A reflection hologram may be recorded
with an object beam and a reference beam positioned on the same
side of a holographic recording medium. If the light played back
travels in the same direction as the reference beam (in other
words, the playback light appears to have been transmitted through
the hologram), the hologram is referred to as a transmission
hologram. A transmission hologram may be recorded with an object
beam and a reference beam positioned on opposite sides of a
holographic recording medium.
[0058] The object beam played back by the hologram may have a
different angle than the reference beam, the difference in angle
between the object beam and the reference beam played back by the
hologram is the redirection angle.
[0059] FIG. 1 is a top-elevational view of typical hologram
recording assembly 100. Typical hologram recording assembly 100
comprises aperture-containing optical path 110, holographic
recording medium ("HRM") 120, beamsplitter 130, object beam 141,
reference beam 142, object beam mirror 151, object beam mirror 152,
reference beam mirror 153, object beam aperture assembly 154,
reference beam aperture assembly 155, collimating aperture assembly
160, laser light source 170 and baffle 180. Each of object beam
aperture assembly 154, reference beam aperture assembly 155, and
collimating aperture assembly 160 comprise a respective aperture,
focusing lens, and collimating lens.
[0060] Recording a hologram requires the generation of a pattern of
optical fringes with laser light; the pattern of optical fringes is
then recorded as a pattern of physical fringes in a HRM. The laser
light may be generated by a laser light source; the laser light may
then be manipulated to generate a pattern of optical fringes.
Non-exclusive examples of laser light manipulations include
focusing the laser light with a lens, reflecting the laser light
with a mirror, and blocking a portion of the laser light with an
aperture. Laser light source 170 generates a laser light signal.
Beamsplitter 130 splits the laser light signal into object beam 141
and reference beam 142. Object beam mirror 151 and object beam
mirror 152 route object beam 141 to HRM 120. Reference beam mirror
153 routes reference beam 142 to HRM 120. The combination of object
beam 141 and reference beam 142 at HRM 120 creates a pattern of
optical fringes, the pattern of optical fringes is recorded as a
pattern of physical fringes in HRM 120.
[0061] The pattern of optical fringes is recorded as a pattern of
physical fringes via a reaction between the HRM and the laser light
comprising the pattern of optical fringes. The reaction between the
HRM and the laser light may be physical; non-exclusive examples of
physical reactions include melting, ablation, and light-induced
changes in refractive index. The reaction between the HRM and may
be chemical, a non-exclusive example of a chemical reaction is
photopolymerization.
[0062] In a photopolymerization, a photoinitiator absorbs light and
produces active centers. Non-exclusive examples of active centers
include anions, cations, and free radicals. The active centers
convert a monomer to a polymer until all of the available monomer
has reacted or until the active centers are destroyed by at least
one quenching reaction. A photopolymerizable HRM comprises a
photoinitiator, a monomer, and a matrix polymer. The monomer may be
converted to photopolymer by exposing the HRM to light. The matrix
polymer has a first refractive index and the photopolymer has a
second refractive index; the first refractive index may be higher
than the second refractive index and the first refractive index may
be lower than the second refractive index. The pattern of optical
fringes is recorded in the photopolymerizable HRM as a pattern of
photopolymer, where the pattern of photopolymer comprises a pattern
of higher or lower refractive index.
[0063] A typical HRM is larger than the desired hologram to allow
variation in the size and position of the recorded hologram. The
position of the pattern of optical fringes determines the position
of the hologram and the position of the pattern of optical fringes
may be controlled by routing the laser light with mirrors. The spot
size of the laser light at the HRM typically determines the size of
the recorded hologram and the spot size of the laser light may be
controlled by blocking a portion of the laser light with an
aperture. Object beam aperture assembly 154, reference beam
aperture assembly 155, and collimating aperture assembly 160 each
comprise an aperture that blocks a portion of the laser light to
control the size of the hologram recorded in HRM 120.
[0064] Blocking a portion of the laser light with an aperture is
disadvantageous since the laser light will diffract as it passes
the sharp edge of the movable blade of the aperture. Diffracting
the laser light may produce an Airy disk around the beam of laser
light, where an Airy disk comprises a series of rings of laser
light surrounding the primary beam of laser light. The distance
between the primary beam of laser light and the rings of the Airy
disk is determined by the distance over which the diffracting laser
light can propagate. No observable Airy disk is formed immediately
adjacent to the aperture, however the Airy disk becomes visible,
and the distance between the primary beam of laser light and the
rings of the Airy disk increases, as the distance between the
aperture and HRM 120 increases.
[0065] Multiple apertures along aperture-containing optical path
110 cause successive diffractions of the laser light, resulting in
complex patterns of optical fringes within and outside the intended
hologram recording area in HRM 120 in addition to the intended
pattern of optical fringes created by the combination of object
beam 141 and reference beam 142.
[0066] Apertures are typically constructed of light-absorbing
materials to reduce the amount of stray light generated by blocking
a portion of the laser light signal. The light absorbing-materials
used in aperture construction are not perfectly efficient,
therefore blocking a portion of laser light with an aperture will
generate some stray light. Stray light can reach the HRM and create
an unintended pattern of optical fringes that may be recorded as an
unintended pattern of physical fringes in HRM 120. Baffle 180 is
typically included in conventional hologram recording assembly 100
in an attempt to prevent stray light from reaching HRM 120. Baffle
180 is typically constructed of light-absorbing materials that are
not perfectly efficient and may reflect stray light, therefore the
inclusion of baffle 180 in typical hologram recording assembly 100
does not necessarily reduce the amount of stray light that reaches
HRM 120 and may in fact increase the amount of stray light reaching
HRM 120.
[0067] A person of skill in the art would appreciate that, in the
various embodiments described herein, photopolymer is used as an
exemplary holographic material. Unless the specific context
requires otherwise, the present systems, devices, and methods can
be employed with holographic materials other than photopolymer e.g.
photographic emulsion, dichromated gelatin, photothermoplastics,
and photorefractives, and references to photopolymer should
generally be construed to encompass any holographic material.
[0068] FIG. 2A is a cross-sectional view of holographic optical
element ("HOE") 200 in accordance with the present systems,
devices, and methods. HOE 200 comprises a single contiguous layer
of photopolymer material. HOE 200 includes recorded area 210,
unrecorded area 220, and boundary area 230. Throughout this
specification and the appended claims, the term "layer" generally
refers to a thickness of some material that provides and/or is
spread over a surface, such as a stratum or a coating on a surface.
A layer may include or cover a single side or face of a structure,
such as a dielectric layer in a printed circuit board or a layer of
cheese on a pizza, or a layer may include or cover multiple sides
or faces of a three-dimensional structure, such as a layer of
clothing or a layer of planet Earth (e.g., the crust, mantle,
etc.). A person of skill in the art will appreciate that the
material of one layer may form the substrate of another layer.
[0069] Recorded area 210 includes hologram fringes that define at
least one hologram. Recorded area 210 is oriented perpendicular to
the principal axis of HOE 200. Throughout this specification and
the appended claims, the term "principal axis" generally refers to
the line parallel to the smallest dimension of a holographic
optical element or a holographic recording medium. An exemplary HOE
has a thickness in a first dimension less than two millimeters, and
a thickness in a second dimension and a thickness in a third
dimension greater than one centimeter. The principle axis of the
exemplary HOE would therefore be parallel to the first dimension
and perpendicular to the second and third dimensions.
[0070] The hologram fringes of recorded area 210 comprise a
photopolymer material with a first amount of refractive index
contrast. The first amount of refractive index contrast may be
greater than 0.005, greater than 0.016, or greater than 0.06. A
refractive index contrast greater than 0.005 is advantageous since
holograms with a refractive index contrast below 0.005 typically do
not possess sufficiently high diffraction efficiencies for
photopolymer of a typical thickness. A refractive index contrast
greater than 0.016 and/or greater than 0.06 may be advantageous as
a higher refractive index contrast typically causes a hologram to
have a higher efficiency, however a person of skill in the art will
appreciate that an excessively high refractive index contrast may
cause the hologram to be overmodulated, reducing the efficiency of
the hologram. Unrecorded area 220 comprises photopolymer material
with a uniform refractive index. Photopolymer material with a
uniform refractive index contains no hologram fringes. The absence
of hologram fringes in unrecorded area 200 includes the absence of
hologram fringes from unwanted secondary holograms. Unrecorded area
220 is oriented perpendicular to the principal axis of HOE 200.
[0071] Boundary area 230 includes hologram fringes comprising a
photopolymer material with a second amount of refractive index
contrast wherein the second amount of refractive index contrast is
less than the first amount of refractive index contrast. The
hologram fringes of boundary area 230 comprise a hologram with a
lower diffraction efficiency than the hologram located in recorded
area 210 due to the lower refractive index contrast of the hologram
fringes of boundary area 230.
[0072] Boundary area 230 is oriented perpendicular to the principal
axis of HOE 200. Boundary area 230 has a thickness as measured in
at least one direction perpendicular to the principal axis of HOE
200 less than a thickness of HOE 200 measured parallel to the
principal axis of HOE 200. The thickness of boundary area 230 as
measured perpendicular to the principal axis of HOE 200 may be less
than one millimeter, less than one hundred micrometers, or less
than six micrometers. Boundary area 230 is positioned between
recorded area 210 and unrecorded area 220. The limited thickness
and reduced diffraction efficiency of boundary area 230 may be
created by recording HOE 200 in an aperture-free hologram recording
assembly.
[0073] The at least one hologram defined by the hologram fringes in
recorded area 210 may comprise a wavelength-multiplexed hologram. A
wavelength multiplexed hologram comprises at least two
wavelength-specific holograms, wherein each wavelength-specific
hologram has a respective playback wavelength; each
wavelength-specific hologram may have a respective incident
playback angle and a respective redirection angle. A wavelength
multiplexed hologram may include a red hologram, a green hologram,
and a blue hologram, which advantageously allows the hologram to be
used in a full-color display (as a holographic combiner or as a
holographic incoupler/outcoupler). A wavelength multiplexed
hologram may include an infrared hologram, which advantageously may
be employed in eye tracking applications.
[0074] The at least one hologram defined by the hologram fringes in
recorded area 210 may possess a redirection angle greater than 30
degrees, greater than 45 degrees, or greater than 60 degrees. A
high redirection angle is advantageous for HOEs employed as
incouplers and/or outcouplers in light guides, since a higher
redirection angle increases the resolution of light guide based
displays.
[0075] Recorded area 210 may possess a thickness measured in at
least one direction perpendicular to the principal axis of HOE 200
less than 2 millimeters; a HOE with a smaller thickness in at least
one direction perpendicular to the principal axis of the HOE is
advantageous for use as a holographic incoupler for a light guide
based display, as a smaller incoupler increases the resolution of
said display.
[0076] FIG. 2B is a side elevational view of HOE 200 in accordance
with the present systems, devices, and methods. HOE 200 may
comprise a protective layer 240 carried by the single contiguous
layer of photopolymer of HOE 200. Non-exclusive examples of
protective layer materials include acrylic, polystyrene, and
polycarbonate. Protective layer 240 is physically coupled to HOE
200. The protection provided by protective layer 240 includes
protection from scratches, tears, and water damage.
[0077] HOE 200 may be curved around a center or axis of curvature
located on an eye-side of HOE 200. A curved HOE may be a
spherically curved HOE; a spherically curved HOE is curved around a
center of curvature. A curved HOE may be a cylindrically curved
HOE; a cylindrically curved HOE is curved around an axis of
curvature. The center or axis of curvature, as appropriate, of HOE
200 may be located on the eye-side of HOE 200 at a distance of
between 1 and 10 centimeters, between 10 and 50 cm, or between 50
and 100 cm from HOE 200.
[0078] Throughout this specification and the appended claims, the
term "eye-side" refers to the side of the object that, when
employed in a device worn by a user, faces towards the eye of the
user, while the term "world-side" refers to the side of the
eyeglass lens that, when employed in a device worn by a user, faces
away from the eye of the user and towards the outside world.
[0079] A curved HOE may be more easily incorporated into curved
lenses for use as a transparent combiner in a wearable heads-up
display ("WHUD"); curved lenses have greater aesthetic appeal than
planar lenses. Recorded area 210 may include M multiplexed
holograms, where M is an integer greater or equal to 1. The M
multiplexed holograms may be wavelength-multiplexed holograms,
angle multiplexed holograms, or any combination thereof.
[0080] Recorded area 210, unrecorded area 220, and boundary area
230 comprise a single layer of photopolymer. HOE 200 may comprise N
layers of photopolymer, where N is an integer greater than or equal
to 1. Each of the N layers of photopolymer include a respective one
of N recorded areas 210, a respective one of N unrecorded areas
220, and a respective one of N boundary areas 230.
[0081] Each of the N recorded areas 210 includes a respective one
of N sets of hologram fringes that define at least one hologram.
Each set of hologram fringes comprise a photopolymer material with
a respective one of N first amounts of refractive index contrast.
Each of the N unrecorded areas 220 comprises a photopolymer with a
uniform refractive index.
[0082] Each of the N boundary areas 230 is positioned between each
respective recorded area and each respective unrecorded area. Each
boundary area 230 includes a respective one of N sets of secondary
hologram fringes; each set of secondary hologram fringes comprises
a photopolymer material with a respective one of N second amounts
of refractive index contrast. Each of the N second amounts of
refractive index contrast is less than each respective first amount
of refractive index contrast. The thickness of each of the N
boundary areas, as measured in at least one direction perpendicular
to the principal axis of the HOE, is less than the thickness of
each one of the N boundary areas as measured parallel to the
principal axis of the HOE.
[0083] FIG. 3A is a cross-sectional view of holographic recording
medium ("HRM") 300 in accordance with the present systems, devices,
and methods. HRM 300 comprises a single contiguous layer of
holographic material. HRM 300 comprises recording area 310,
bleached area 320 and boundary area 330. In recording area 310 a
holographic material of HRM 300 is photopolymerizable to a first
degree. In bleached area 320 the holographic material of HRM 300 is
not photopolymerizable.
[0084] The degree to which a holographic material is
photopolymerizable is determined by the amount of photoinitiator
and the amount of monomer present in the holographic material. A
holographic material is photopolymerizable if the holographic
material contains both photoinitiator and monomer. A holographic
material is not photopolymerizable if the holographic material
lacks sufficient quantities of either photoinitiator or monomer to
produce photopolymer upon exposure to light. A holographic material
with a greater amount of photoinitiator and a greater amount of
monomer is more photopolymerizable than a holographic material with
a lesser amount of photoinitiator and a lesser amount of monomer.
Exposing a holographic material to light causes the holographic
material to become less photopolymerizable by consuming both
photoinitiator and monomer.
[0085] Boundary area 330 is positioned between recorded area 310
and bleached area 320. In boundary area 320 the holographic
material of HRM 300 is photopolymerizable to a second degree. The
first degree to which the holographic material of HRM 300 is
photopolymerizable in recording area 310 is higher than the second
degree to which the holographic material of HRM 300 is
polymerizable in boundary area 330. Boundary area 330 has a
thickness as measured in at least one direction perpendicular to
the principal axis of HRM 300 less than a thickness of HRM 300
measured parallel to the principal axis of HRM 300. The thickness
of boundary area 330 as measured perpendicular to the principal
axis of HRM 300 may be less than one millimeter, less than one
hundred micrometers, less than six micrometers.
[0086] A hologram may be recorded in HRM 300. The size of the
hologram recorded in HRM 300 may not exceed the area of recording
area 310 and boundary area 300 combined; the size of the hologram
will not significantly exceed the area of recording area 310 due to
the limited dimensions of boundary area 330 as described above. The
size limits imposed on hologram recording by the size of recording
area 310 are advantageous, since this allows the size of the
hologram to be determined by the physical dimensions of recording
area 310 rather than the spot sizes of beams of laser light used to
record holograms. The spot size of a beam of laser light is
typically controlled by an aperture. Eliminating the need to
control spot sizes when recording a hologram in HRM 300 therefore
eliminates the need for apertures when recording a hologram in HRM
300.
[0087] Recording area 310 may possess a thickness measured in at
least one direction perpendicular to the principal axis of HRM 300
less than 2 millimeters; a recording area with a smaller thickness
in at least one direction perpendicular to the principal axis of
the HOE is advantageous for use as a recording material for
holographic incouplers for a light guide based display, as a
smaller incoupler increases the resolution of said display.
[0088] FIG. 3B is a side elevational view of HRM 300 in accordance
with the present systems, devices, and methods. HRM 300 may
comprise a protective layer 340 carried by the single contiguous
layer of holographic material of HRM 300. Protective layer 340 may
comprise first protective layer 360 and second protective layer
370. First protective layer 360 and second protective layer 370
cover opposing surfaces of the single contiguous layer of
holographic material of HRM 300. At least one of first protective
layer 360 and second protective layer 370 may comprise a
provisional protective layer. A provisional protective layer may be
physically de-coupled from HRM 300 without causing damage to HRM
300. A provisional protective layer is advantageous as it protects
HRM 300 from damage during processing and may then be removed prior
to any subsequent processes that are incompatible with the
protective layer.
[0089] FIG. 4 is a flow-diagram showing a method 400 of fabricating
a HRM in accordance with the present systems, devices, and methods.
Method 400 includes three acts 401, 402, and 403 though those of
skill in the art will appreciate that in alternative embodiments
certain acts may be omitted and/or additional acts may be added.
Those of skill in the art will also appreciate that the illustrated
order of the acts is shown for exemplary purposes only and may
change in alternative embodiments.
[0090] As an illustrative example of the physical elements of
method 400, analogous structures from FIG. 5 are called out in
parentheses throughout the description of acts 401, 402, and
403.
[0091] At 401, a mask (520) is applied to a layer of holographic
material (510). The mask (520) is a layer of material that is
provisionally physically coupled to the layer of holographic
material (510); the mask (520) may be applied to the layer of
holographic material (510) and the mask (520) may also be removed
from the layer of holographic material (510). The mask (520)
comprises at least one permissive area (531) and at least one
obstructive area (532). The at least one permissive area (531)
allows a subsequent treatment to occur in the area of the layer of
holographic material covered by the at least one permissive area
(531). The at least one obstructive area (532) prevents a
subsequent treatment from occurring in the area of the layer of
holographic material covered by the at least one obstructive area
(532). Non-exclusive examples of treatments include bleaching,
etching, and hardening.
[0092] Permissive areas (531) may be non-contiguous. Permissive
areas (531) may have shapes and features with an upper size limit
determined by the size of the mask (520) since a given feature must
be able to fit entirely within the mask (520). Permissive areas
(531) may have shapes and features with a lower size limit
determined by the resolution limit of the mask fabrication method.
Masks may be produced via photolithographic techniques which can
produce features with a resolution limit of 50 nanometers.
Obstructive areas (532) may be non-contiguous. Obstructive areas
(532) may have shapes and features with an upper size limit
determined by the size of the mask (520) and a lower size limit
determined by the resolution limit of the mask fabrication method.
The obstructive area (532) may have a shape selected from a group
consisting of: a circle, an oval, a triangle, a square, a
rectangle, a hexagon, and an octagon.
[0093] The layer of holographic material (510) may comprise a front
surface (511) and a back surface (512). Applying a mask (520) to a
layer of holographic material (510) may include applying a front
mask (521) to the front surface of the layer of holographic
material (511). The front mask (521) comprises at least one
permissive area (531) and at least one obstructive area (532).
Applying a mask (520) to a layer of holographic material (510) may
include applying a back mask (522) to the back surface of the layer
of holographic material (512). The back mask (522) comprises a
single obstructive area.
[0094] At 402, the masked layer of holographic material (500) is
bleached. Bleaching includes exposing the masked layer of
holographic material (500) to a bleaching agent. Non-exclusive
examples of a bleaching agents include acids, peroxides,
hypochlorites, and light. Photobleaching includes exposing a masked
layer of holographic material (500) to light. The light used for
photobleaching may be incoherent. The light used for photobleaching
may be polychromatic, wherein at least a portion of the light which
is used for photobleaching may be absorbed by the photoinitiator or
the monomer.
[0095] Photobleaching the masked layer of holographic material
(500) converts at least a portion of the layer of holographic
material (510) from a photopolymerizable material to a material
that is not photopolymerizable. During photobleaching, the
permissive areas (531) of the mask (520) are transparent to at
least one wavelength of the light used for photobleaching. During
photobleaching, the obstructive areas (532) of the mask (520) are
opaque to all wavelengths of the light used for photobleaching that
may be absorbed by the photoinitiator or the monomer.
[0096] At 403, the mask is removed from the layer of holographic
material (510).
[0097] FIG. 5A is a side elevational view of masked layer of
holographic material 500 in accordance with the present systems,
devices, and methods. Masked layer of holographic material 500
includes layer of holographic material 510 and mask 520. Layer of
holographic material 510 includes front surface of the layer of
holographic material 511 and back surface of the layer of
holographic material 512. Mask 520 comprises front mask 521 and
back mask 522.
[0098] FIG. 5B is a front elevational view of masked layer of
holographic material 500 in accordance with the present systems,
devices, and methods. Only front mask 521 is visible in FIG. 5B due
to the front elevational view; layer of holographic material 510
and back mask 522 are obscured from view by front mask 521 due to
the viewing angle in FIG. 5B. Front mask 521 comprises at least one
permissive area 531 and at least one obstructive area 532. Back
mask may be substantively similar to front mask 531. Back mask 522
comprises at least one obstructive area 532 and may comprise at
least one permissive area 531.
[0099] FIG. 6 is a top-elevational view of aperture-free hologram
recording assembly 600 in accordance with the present systems,
devices, and methods. Aperture-free hologram recording assembly 600
comprises: aperture-free optical path 610, HRM 620, beamsplitter
630, object beam 641, reference beam 642, object beam mirror 651,
object beam mirror 652, reference beam mirror 653, object beam lens
654, reference beam lens 655, collimating lens 660 and laser light
source 670.
[0100] Laser light source 670 generates a beam of laser light. The
beam of laser light travels along aperture-free optical path 610.
Aperture-free optical path 610 includes HRM 620, beamsplitter 630,
object beam mirror 651, object beam mirror 652, reference beam
mirror 653, object beam lens 654, reference beam lens 655, and
collimating lens 660. Aperture-free optical path 610 does not
include laser light source 670. Collimating lens 660 collimates the
beam of laser light after the beam of laser light exits laser light
source 670. HRM 620 may comprise a layer of holographic material.
HRM 620 may comprise a masked layer of holographic material
substantively similar to masked layer of holographic material
500.
[0101] Beamsplitter 630 splits the beam of laser light to form
object beam 641 and reference beam 642. Object beam mirror 651 and
object beam mirror 652 route object beam 641 to illuminate HRM 620.
Object beam lens 654 shapes object beam 641 to a desired
cross-section at HRM 620. Reference beam mirror 653 routes
reference beam 642 to illuminate HRM 620. Reference beam lens 655
shapes reference beam 642 to a desired cross-section at HRM
620.
[0102] Aperture-free hologram recording assembly 600 may record a
hologram in HRM 620 by illuminating HRM 620 with object beam 641
and reference beam 642. HRM 620 may be substantively similar to HRM
300 (FIG. 3). The use of a HRM substantively similar to HRM 300 is
advantageous since the recorded hologram will not be significantly
larger than recording area 310 (FIG. 3) regardless of the spot size
of the object beam or the spot size of the reference beam; a
hologram cannot be recorded in bleached area 320 (FIG. 3) and
boundary area 330 (FIG. 3) is typically small relative to the size
of recording area 310. The insensitivity of HRM to large spot sizes
allows for larger tolerances in spot size, reducing the need for
careful positioning of object beam lens 654 and reference beam lens
655.
[0103] FIG. 7 is a flow-diagram showing a method 700 of recording a
hologram in accordance with the present systems, devices, and
methods. Method 700 includes five acts 701, 702, 703, 704, and 705
though those of skill in the art will appreciate that in
alternative embodiments certain acts may be omitted and/or
additional acts may be added. Those of skill in the art will also
appreciate that the illustrated order of the acts is shown for
exemplary purposes only and may change in alternative
embodiments.
[0104] As an illustrative example of the physical elements of
method 700, analogous structures from FIG. 5 and FIG. 6 are called
out in parentheses throughout the description of acts 701, 702,
703, 704, and 705.
[0105] At 701, a layer of holographic material (510, 620) is
mounted in an aperture-free recording assembly (600). The
aperture-free hologram recording assembly (600) comprises a laser
light source (670) and an aperture-free optical path (610). The
laser light source (670) does not require an aperture in order to
generate a laser light signal, the beam diameter of the laser light
signal generated by the laser light source (670) may be controlled
via controlling the geometry of a resonant chamber of the laser
light source (670). A person of skill in the art will appreciate
that controlling the geometry of the resonant chamber of the laser
light source controls where and how photons of light are created
rather than blocking light in a manner consistent with an aperture.
The laser light source may comprise at least one aperture. The
aperture-free optical path (610) may comprise beam-routing mirrors
(651, 652, 653), and the aperture-free optical path (610) may
comprise beam-shaping lenses (654, 655), however the aperture-free
optical path (610) does not comprise any apertures. The
aperture-free optical path (610) does not include the laser light
source (670).
[0106] At 702, a mask (520) is applied to the layer of holographic
material (510, 620). The mask (520) comprises at least one
obstructive area (532) wherein the at least one obstructive area
(532) is configured to shield a portion of the layer of holographic
material from light exposure. The mask (520) comprises at least one
permissive area (531) wherein the at least one permissive area
(531) is configured to expose a portion of the layer of holographic
material to light.
[0107] The layer of holographic material (510, 620) may comprise a
front surface (511) and a back surface (512). Applying a mask (520)
to the layer of holographic material (510, 620) may include
applying a front mask (521) to the front surface of the layer of
holographic material (511). The front mask comprises at least one
permissive area (531) and at least one obstructive area (532).
Applying a mask (520) to the layer of holographic material (510,
620) may include applying a back mask (522) to the back surface of
the layer of holographic material (512). The back mask comprises at
least one permissive area (531) and at least one obstructive area
(532). Each permissive area (531) of the back mask (522) is aligned
with a respective permissive area (521) of the front mask (521)
along the principal axis of the layer of holographic material. Each
obstructive area (532) of the back mask (522) is aligned with a
respective obstructive area (532) of the front mask along the
principal axis of the layer of holographic material.
[0108] The front mask (521) may comprise at least one permissive
area with a shape selected from a group consisting of: a circle, an
oval, a triangle, a square, a rectangle, a hexagon, and an octagon.
The back mask (522) may comprise at least one permissive area with
a shape selected from a group consisting of: a circle, an oval, a
triangle, a square, a rectangle, a hexagon, and an octagon.
[0109] At 703, the layer of holographic material (510, 620) is
illuminated with laser light. The layer of holographic material
(510, 620) may comprise a masked layer of holographic material
(500). Illuminating the layer of holographic material (510, 620)
with laser light includes routing laser light from a laser light
source (670) along an aperture-free optical path (610) to the layer
of holographic material (510, 620). Illuminating the layer of
holographic material (510, 620) with laser light may include
illuminating the layer of holographic material (510, 620) with
laser light generated by a laser light source (670) wherein the
laser light source (670) comprises an aperture. An aperture within
the laser light source (670) may create an undesirable diffraction
pattern, however the distance between the laser light source (670)
and the layer of holographic material (510, 620) may be large
enough to ensure that the undesirable diffraction pattern falls on
a portion of the layer of holographic material that is covered by
the obstructive area (532) of the mask (520) covering the layer of
holographic material (510, 620).
[0110] Illuminating the layer of holographic material (510, 620)
with laser light records a hologram in the layer of holographic
material (510, 620). If the layer of holographic material (510,
620) comprises a masked layer of holographic material (500), the
hologram is not recorded in any area of the layer of holographic
material (510, 620) covered by the at least one obstructive area
(532) because the obstructive area (532) shields the layer of
holographic material (510, 620) from the laser light. If the layer
of holographic material (510, 620) comprises a masked layer of
holographic material (500), the hologram is recorded in the area of
the layer of holographic material (510, 620) covered by the at
least one permissive area (531) because the at least one permissive
area (531) allows the layer of holographic material (510, 620) to
be exposed to the laser light. If the layer of holographic material
(510, 620) comprises a masked layer of holographic material (500),
the mask (520) limits the size and position of a recorded hologram
to the area of the layer of holographic material (510, 620) covered
by the at least one permissive area (531) of the mask, therefore
the mask (520) eliminates the need for apertures in the
aperture-free hologram recording assembly (600).
[0111] A person of skill in the art will appreciate that a mask
(520) and an aperture both block at least a portion of laser light
from reaching the layer of holographic material (510, 620) and
simultaneously comprise a sharp edge that diffracts laser light. A
mask (520) is placed in direct physical contact with the layer of
holographic material (510, 620), therefore any diffraction caused
by the mask (520) can only propagate through a distance equal to
the thickness of the layer of holographic material (510, 620) and
any included protective materials. The thickness of the layer of
holographic material (510, 620) is typically less than two
millimeters and no significant diffraction can occur with such a
short propagation distance. An aperture is typically positioned at
a distance of more than ten centimeters from the layer of
holographic material (510, 620), since an aperture is designed to
allow additional beam manipulation further along the optical path
of the beam. Significant diffraction propagation can occur over a
distance of more than ten centimeters leading to the recording of
unintentional secondary holograms in the layer of holographic
material (510, 620).
[0112] Routing the laser light from the laser light source along an
aperture-free optical path to the layer of holographic material may
include splitting the laser light with a beamsplitter to form a
laser light object beam and a laser light reference beam. Routing
the laser light from the laser light source along an aperture-free
optical path to the layer of holographic material may include
collimating the laser light object beam, collimating the laser
light reference beam, routing the laser light object beam to
illuminate the layer of holographic material (500), and routing the
laser light reference beam to illuminate the layer of holographic
material (500).
[0113] Collimating the laser light object beam includes collimating
the laser light object beam with a collimating lens. Collimating
the laser light reference beam includes collimating the laser light
reference beam with a collimating lens. Routing the laser light
object beam to illuminate the layer of holographic material (500)
includes routing the laser light object beam with an object beam
mirror (653). Routing the laser light reference beam to illuminate
the layer of holographic material (500) includes routing the laser
light reference beam with a reference beam mirror (651, 652)
[0114] Illuminating the layer of holographic material (510, 620)
with laser light may include illuminating the layer of holographic
material (510, 620) with laser light that comprises N wavelengths
of laser light, where N is an integer greater than 1. Illuminating
the layer of holographic material (510, 620) with laser light
comprising N different wavelengths of laser light records a
wavelength-multiplexed hologram in the layer of holographic
material (510, 620). A wavelength-multiplexed hologram is
advantageous because wavelength-multiplexed holograms can produce
full-color displays when used in holographic display
applications.
[0115] Illuminating the layer of holographic material (510, 620)
with laser light may include illuminating the layer of holographic
material (510, 620) with laser light that comprises N angles, where
N is an integer greater than 1. Illuminating the layer of
holographic material (510, 620) with laser light comprising N
different angles records an angle-multiplexed hologram in the layer
of holographic material (510, 620). An angle-multiplexed hologram
is advantageous because angle-multiplexed holograms possess an
effectively increased angular bandwidth that increases the field of
view of displays employing the angle-multiplexed hologram.
Illuminating the layer of holographic material (510, 620) with
laser light may include concurrently illuminating a same surface of
the layer of holographic material (510, 620) with both a laser
light reference beam (642) and a laser light object beam (641).
Illuminating the layer of holographic material with laser light
concurrently with a laser light reference beam (642) and a laser
light object beam (641) on a same surface records a transmission
hologram in the layer of holographic material (510, 620).
[0116] Illuminating the layer of holographic material (510, 620)
with laser light may include concurrently illuminating a first
surface of the layer of holographic material of the layer of
holographic material (510, 620) with a laser light reference beam
(642) and a second surface of the layer of holographic material
with a laser light object beam (641). The second surface of the
layer of holographic material (510, 620) is located opposite the
first surface of the layer of holographic material (510, 620).
Illuminating the layer of holographic material with laser light
concurrently with a laser light reference beam (642) and a laser
light object beam (641) on opposite surfaces records a reflection
hologram in the layer of holographic material (510, 620).
[0117] Illuminating the layer of holographic material (510, 620)
with laser light may include illuminating the layer of holographic
material with at least one laser light reference beam and at least
two laser light object beams. Each of the at least two laser light
object beams may illuminate the layer of holographic material (510,
620) with a respective one of .theta. angles, where .theta. is an
integer greater than 1.
[0118] At 704, the mask (520) is removed from the layer of
holographic material (510, 620). Removal of the mask (520) allows
the areas of the layer of holographic material (510, 620) that were
previously covered by the obstructive areas (532) of the mask (520)
to subsequently be exposed to light.
[0119] At 705, the layer of holographic material (510, 620) is
bleached. Bleaching the layer of holographic material (510, 620)
may include photobleaching. Photobleaching the layer of holographic
material (510, 620) includes exposing the layer of holographic
material to light. The light used for photobleaching may be
incoherent light. The light used for photobleaching may be
polychromatic, wherein at least a portion of the light which is
used for photobleaching may be absorbed by the photoinitiator or
the monomer. Photobleaching the layer of holographic material (510,
620) converts at least a portion of the layer of holographic
material (510, 620) from a photopolymerizable material to a
material that is not photopolymerizable.
[0120] Method 700 may further comprise pre-bleaching the layer of
holographic material (510, 620). Pre-bleaching the layer of
holographic material (510, 620) includes converting a portion of
the layer of holographic material (510, 620) from a material that
is photopolymerizable to a material that is not photopolymerizable.
Pre-bleaching the layer of holographic material (510, 620) may
include photo-bleaching the layer of holographic material (510,
620).
[0121] Pre-bleaching the layer of holographic material (510, 620)
occurs subsequent to applying a mask (520) to the layer of
holographic material (510, 620). Pre-bleaching the layer of
holographic material (510, 620) occurs prior to removing the mask
(520) from the layer of holographic material (510, 620). If the
layer of holographic material (510, 620) is pre-bleached, applying
a mask (520) to the layer of holographic material (510, 620)
includes applying a negative mask to the layer of holographic
material (510, 620). A negative mask comprises a mask (520) wherein
the obstructive areas (532) cover the portion of the layer of
holographic material (510, 620) that, subsequent to pre-bleaching,
comprises a material that is photopolymerizable. A negative mask
comprises a mask (520) wherein the at least one permissive area
(531) covers the portion of the layer of holographic material (510,
620) that, subsequent to pre-bleaching, comprises a material that
is not photopolymerizable. The maximum size of a hologram that may
be recorded in the layer of holographic material (510, 620) is
equal to the size of the areas of the layer of holographic material
(510, 620) that were covered by the at least one obstructive area
(532) of the negative mask. The limits on the size of the
recordable hologram imposed by pre-bleaching the layer of
holographic material (510, 620) with a negative mask eliminate the
need for apertures in the aperture-free hologram recording assembly
(600).
[0122] FIG. 8 is a flow-diagram showing a method 800 of recording a
hologram in accordance with the present systems, devices, and
methods. Method 800 includes twelve acts 801, 802, 803, 804, 805,
806, 807, 808, 809, 810, 811, and 812 though those of skill in the
art will appreciate that in alternative embodiments certain acts
may be omitted and/or additional acts may be added. Those of skill
in the art will also appreciate that the illustrated order of the
acts is shown for exemplary purposes only and may change in
alternative embodiments.
[0123] As an illustrative example of the physical elements of
method 700, analogous structures from FIG. 5 and FIG. 6 are called
out in parentheses throughout the description of acts 801, 802,
803, 804, 805, 806, 807, 808, 809, 810, 811, and 812.
[0124] At 801, a layer of holographic material (510, 620) is
mounted in an aperture-free recording assembly (600). The
aperture-free hologram recording assembly (600) comprises a laser
light source (670) and an aperture-free optical path (610). The
laser light source (670) does not require an aperture in order to
generate a laser light signal, the beam diameter of the laser light
signal may be controlled via careful design of a resonant chamber
of the laser light source (670). The laser light source may
comprise at least one aperture. The aperture-free optical path
(610) may comprise beam-routing mirrors (651, 652, 653), and the
aperture-free optical path (610) may comprise beam-shaping lenses
(654, 655), however the aperture-free optical path (610) does not
comprise any apertures. The aperture-free optical path (610) does
not include the laser light source (670).
[0125] At 802, a mask (520) is applied to the layer of holographic
material (510, 620). The mask (520) comprises at least one
obstructive area wherein the at least one obstructive area is
configured to shield a portion of the layer of holographic material
from light exposure. The mask (520) comprises at least one
permissive area wherein the at least one permissive area is
configured to expose a portion of the layer of holographic material
to light. The mask (520) eliminates the need for apertures in the
aperture-free hologram recording assembly (600).
[0126] The layer of holographic material (510, 620) may comprise a
front surface (511) and a back surface (512). Applying a mask (520)
to the layer of holographic material (510, 620) may include
applying a front mask (521) to the front surface of the layer of
holographic material (511). The front mask comprises at least one
permissive area (531) and at least one obstructive area (532).
Applying a mask (520) to the layer of holographic material (510,
620) may include applying a back mask (522) to the back surface of
the layer of holographic material (512). The back mask comprises at
least one permissive area (531) and at least one obstructive area
(532). Each permissive area (531) of the back mask (522) is aligned
with a respective permissive area (521) of the front mask (521)
along the principal axis of the layer of holographic material. Each
obstructive area (532) of the back mask (522) is aligned with a
respective obstructive area (532) of the front mask along the
principal axis of the layer of holographic material.
[0127] The front mask (521) may comprise at least one permissive
area with a shape selected from a group consisting of: a circle, an
oval, a triangle, a square, a rectangle, a hexagon, and an octagon.
The back mask (522) may comprise at least one permissive area with
a shape selected from a group consisting of: a circle, an oval, a
triangle, a square, a rectangle, a hexagon, and an octagon.
[0128] At 803, a laser light signal is generated with at least one
laser light source (670). Generating a laser light signal may
include generating a laser light signal comprising N wavelengths of
laser light, where N is an integer greater than 1. Generating a
laser light signal may include generating a laser light signal with
a laser light source (670), wherein the laser light source (670)
comprises an aperture.
[0129] At 804, the laser light signal is split with a beamsplitter
(630) to form an object beam (641) and a reference beam (642).
Non-exclusive examples of beamsplitters include a beamsplitter
cube, a Wollaston prism, and a semi-silvered mirror.
[0130] At 805, the object beam (641) is routed to illuminate the
layer of holographic material (500). Non-exclusive examples of
object beam routing components include a mirror (651, 652), a
prism, split wedges, and an optical fiber. Routing the object beam
to illuminate the layer of holographic material (510, 620) may
include routing the object beam to illuminate a first surface of
the layer of holographic material (510, 620).
[0131] At 806, the object beam (641) is shaped to a desired
cross-section at the layer of holographic material (500).
Non-exclusive examples of object beam shaping components include a
lens (654) and a diffractive optical element.
[0132] At 807, the reference beam (642) is routed to illuminate the
layer of holographic material (500). Non-exclusive examples of
reference beam routing components include a mirror (653), a prism,
split wedges, and an optical fiber.
[0133] Routing the reference beam to illuminate the layer of
holographic material (510, 620) may include routing the reference
beam to illuminate a first surface of the layer of holographic
material (510, 620). Routing the object beam and the reference beam
to the same surface of the layer of holographic material (510, 620)
allows recording of a transmission hologram. Routing the reference
beam to illuminate the layer of holographic material (510, 620) may
include routing the reference beam to illuminate a second surface
of the layer of holographic material (510, 620). The second surface
of the layer of holographic material (510, 620) is opposite the
first surface of the layer of holographic material (510, 620).
Routing the object beam and the reference beam to opposite surfaces
of the layer of holographic material (510, 620) allows recording of
a reflection hologram.
[0134] At 808, the reference beam (642) is shaped to a desired
cross-section at the layer of holographic material (500).
Non-exclusive examples of reference beam shaping components include
a lens (655) and a diffractive optical element.
[0135] At 809, a pattern of optical fringes is generated in at
least at least a portion of the layer of holographic material (510,
620) by a combination of the reference beam and the object beam.
The layer of holographic material (510, 620) may comprise a masked
layer of holographic material (500). If the layer of holographic
material (510, 620) comprises a masked layer of holographic
material (500), the pattern of optical fringes is generated only in
the portion of the layer of holographic material (510, 620) covered
by the at least one permissive area (531) of the mask.
[0136] Generating a pattern of optical fringes in at least a
portion of the layer of holographic material (510, 620) by a
combination of the reference beam and the object beam may include
generating N sub-patterns of optical fringes in at least a portion
of the layer of holographic material by the combination of the
reference beam and the object beam, where N is an integer greater
than 1.
[0137] At 810, the pattern of optical fringes is recorded as a
pattern of physical fringes in at least a portion of the layer of
holographic material (510, 620). If the layer of holographic
material (510, 620) comprises a masked layer of holographic
material (500), the pattern of optical fringes is recorded as a
pattern of physical fringes only in the portion of the layer of
holographic material (510, 620) covered by the at least one
permissive area (531) of the mask.
[0138] Recording a pattern of optical fringes as a pattern of
physical fringes in at least a portion of the layer of holographic
material (510, 620) may include recording N sub-patterns of optical
fringes as N sub-patterns of physical fringes in at least a portion
of the layer of holographic material, where N is an integer greater
than 1.
[0139] At 811, the mask (520) is removed from the layer of
holographic material (510, 620).
[0140] At 812, the layer of holographic material is bleached.
Bleaching the layer of holographic material (510, 620) may include
photobleaching. Method 800 may further comprise pre-bleaching the
layer of holographic material (510, 620). Pre-bleaching the layer
of holographic material (510, 620) may include photo-bleaching the
layer of holographic material (510, 620).
[0141] Pre-bleaching the layer of holographic material (510, 620)
occurs prior to removing the mask (520) from the layer of
holographic material (510, 620). If the layer of holographic
material (510, 620) is pre-bleached, applying a mask (520) to the
layer of holographic material (510, 620) includes applying a
negative mask to the layer of holographic material (510, 620). A
negative mask comprises a mask (520) wherein the obstructive areas
(532) cover the portion of the layer of holographic material that
will contain a recorded hologram. A negative mask comprises a mask
(520) wherein the at least one permissive area (531) covers the
portion of the layer of holographic material that will not contain
a recorded hologram. Pre-bleaching the layer of holographic
material (510, 620) covered by a negative mask eliminates the need
for apertures in the aperture-free hologram recording assembly
(600).
[0142] Generating a laser light signal may include generating a
laser light signal comprising M angles, where M is an integer
greater than 1. Generating a pattern of optical fringes in at least
a portion of the layer of holographic material by a combination of
the reference beam and the object beam may include generating M
sub-patterns of optical fringes in at least a portion of the layer
of holographic material by the combination of the reference beam
and the object beam. Recording the pattern of optical fringes as a
pattern of physical fringes in at least a portion of the layer of
holographic material may include recording the M sub-patterns of
optical fringes as M sub-patterns of physical fringes in at least a
portion of the layer of holographic material. Recording the M
sub-patterns of optical fringes as M sub-patterns of physical
fringes records an angle-multiplexed hologram in the layer of
holographic material (510, 620).
[0143] FIG. 9 is a flow-diagram showing a method 900 of recording a
hologram in accordance with the present systems, devices, and
methods. Method 900 includes twelve acts 901, 902, 903, 904, 905,
906, 907, 908, 909, 910, 911, and 912 though those of skill in the
art will appreciate that in alternative embodiments certain acts
may be omitted and/or additional acts may be added. Those of skill
in the art will also appreciate that the illustrated order of the
acts is shown for exemplary purposes only and may change in
alternative embodiments.
[0144] As an illustrative example of the physical elements of
method 900, analogous structures from FIG. 5 and FIG. 6 are called
out in parentheses throughout the description of acts 901, 902,
903, 904, 905, 906, 907, 908, 909, 910, 911, and 912.
[0145] At 901, a layer of holographic material (510, 620) is
mounted in an aperture-free recording assembly (600). The
aperture-free hologram recording assembly (600) comprises a laser
light source (670) and an aperture-free optical path (610). The
laser light source (670) does not require an aperture in order to
generate a laser light signal, the beam diameter of the laser light
signal may be controlled via careful design of a resonant chamber
of the laser light source (670). The laser light source may
comprise at least one aperture. The aperture-free optical path
(610) may comprise beam-routing mirrors (651, 652, 653), and the
aperture-free optical path (610) may comprise beam-shaping lenses
(654, 655), however the aperture-free optical path (610) does not
comprise any apertures. The aperture-free optical path (610) does
not include the laser light source (670).
[0146] At 902, a mask (520) is applied to the layer of holographic
material (510, 620). The mask (520) comprises at least one
obstructive area wherein the at least one obstructive area is
configured to shield a portion of the layer of holographic material
from light exposure. The mask (520) comprises at least one
permissive area wherein the at least one permissive area is
configured to expose a portion of the layer of holographic material
to light. The mask (520) eliminates the need for apertures in the
aperture-free hologram recording assembly (600).
[0147] At 903, a laser light signal is generated with at least one
laser light source (670). Generating a laser light signal may
include generating a laser light signal with a laser light source
(670), wherein the laser light source (670) comprises an
aperture.
[0148] At 904, the laser light signal is split with at least one
beamsplitter (630) to form N object beams (641) and M reference
beams (642), where N and M are both integers that are greater than
or equal to 1. Non-exclusive examples of beamsplitters include a
beamsplitter cube, a Wollaston prism, and a semi-silvered
mirror.
[0149] At 905, the N object beams (641) are routed to illuminate
the layer of holographic material (510, 620). Non-exclusive
examples of object beam routing components include a mirror (651,
652), a prism, split wedges, and an optical fiber. Routing the N
object beams to illuminate the layer of holographic material (510,
620) may include routing the object beam to illuminate a first
surface of the layer of holographic material (510, 620).
[0150] At 906, the N object beams (641) are shaped to N respective
cross-sections at the layer of holographic material (510, 620).
Non-exclusive examples of object beam shaping components include a
lens (654) and a diffractive optical element.
[0151] At 907, the M reference beams (642) are routed to illuminate
the layer of holographic material (500). Non-exclusive examples of
reference beam routing components include a mirror (653), a prism,
split wedges, and an optical fiber.
[0152] Routing the M reference beams (642) to illuminate the layer
of holographic material (510, 620) may include routing the M
reference beams (642) to illuminate a first surface of the layer of
holographic material (510, 620). Routing the N object beams and the
M reference beams to the same surface of the layer of holographic
material (510, 620) allows recording of a transmission hologram.
Routing the M reference beams to illuminate the layer of
holographic material (510, 620) may include routing the M reference
beams to illuminate a second surface of the layer of holographic
material (510, 620). The second surface of the layer of holographic
material (510, 620) is opposite the first surface of the layer of
holographic material (510, 620). Routing the N object beams and the
M reference beams to opposite surfaces of the layer of holographic
material (510, 620) allows recording of a reflection hologram.
[0153] At 908, the M reference beams (642) are shaped to M
respective cross-sections at the layer of holographic material
(510, 620). Non-exclusive examples of reference beam shaping
components include a lens (655) and a diffractive optical
element.
[0154] At 909, a pattern of optical fringes is generated in at
least a portion of the layer of holographic material (510, 620) by
a combination of the M reference beams and the N object beams. The
layer of holographic material (510, 620) may comprise a masked
layer of holographic material (500). If the layer of holographic
material (510, 620) comprises a masked layer of holographic
material (500), the pattern of optical fringes is generated only in
the portion of the layer of holographic material (510, 620) covered
by the at least one permissive area (531) of the mask.
[0155] At 910, the pattern of optical fringes is recorded as a
pattern of physical fringes in at least a portion of the layer of
holographic material (500). If the layer of holographic material
(510, 620) comprises a masked layer of holographic material (500),
the pattern of optical fringes is recorded as a pattern of physical
fringes only in the portion of the layer of holographic material
(510, 620) covered by the at least one permissive area (531) of the
mask.
[0156] Generating a pattern of optical fringes in at least a
portion of the layer of holographic material (510, 620) by a
combination of the reference beam and the object beam may include
generating L sub-patterns of optical fringes in at least a portion
of the layer of holographic material by the combination of the
reference beam and the object beam, where L is an integer greater
than 1.
[0157] At 911, the mask is removed from the layer of holographic
material (510, 620).
[0158] At 912, the layer of holographic material is bleached.
Bleaching the layer of holographic material (510, 620) may include
photobleaching. Method 900 may further comprise pre-bleaching the
layer of holographic material (510, 620). Pre-bleaching the layer
of holographic material (510, 620) may include photo-bleaching the
layer of holographic material (510, 620).
[0159] Pre-bleaching the layer of holographic material (510, 620)
occurs prior to removing the mask (520) from the layer of
holographic material (510, 620). If the layer of holographic
material (510, 620) is pre-bleached, applying a mask (520) to the
layer of holographic material (510, 620) includes applying a
negative mask to the layer of holographic material (510, 620). A
negative mask comprises a mask (520) wherein the obstructive areas
(532) cover the portion of the layer of holographic material that
will contain a recorded hologram. A negative mask comprises a mask
(520) wherein the at least one permissive area (531) covers the
portion of the layer of holographic material that will not contain
a recorded hologram. Pre-bleaching the layer of holographic
material (510, 620) covered by a negative mask eliminates the need
for apertures in the aperture-free hologram recording assembly
(600).
[0160] Generating a laser light signal may include generating a
laser light signal comprising L wavelengths of laser light, where L
is an integer greater than 1. Generating a pattern of optical
fringes in at least a portion of the layer of holographic material
by a combination of the reference beam and the object beam may
include generating L sub-patterns of optical fringes in at least a
portion of the layer of holographic material by the combination of
the reference beam and the object beam. Recording the pattern of
optical fringes as a pattern of physical fringes in at least a
portion of the layer of holographic material may include recording
the L sub-patterns of optical fringes as L sub-patterns of physical
fringes in at least a portion of the layer of holographic material.
Recording the L sub-patterns of optical fringes as N sub-patterns
of physical fringes records an angle-multiplexed hologram in the
layer of holographic material (510, 620).
[0161] FIG. 10 is a top elevational view of curved HOE 1000 in
accordance with the present systems, devices, and methods. Curved
HOE 1000 comprises a single contiguous layer of photopolymer
material. Curved HOE 1000 may be substantively similar to HOE 200.
Curved HOE comprises eye-side surface 1010 and world-side surface
1020. Curved HOE 1000 is cylindrically curved around an axis of
curvature, the axis of curvature of HOE 200 is located on the
eye-side of curved HOE 1000 at a distance of between 1 and 10
centimeters, between 10 and 50 cm, or between 50 and 100 cm from
eye-side surface 1010.
[0162] Throughout this specification and the appended claims,
infinitive verb forms are often used. Examples include, without
limitation: "to detect," "to provide," "to transmit," "to
communicate," "to process," "to route," and the like. Unless the
specific context requires otherwise, such infinitive verb forms are
used in an open, inclusive sense, that is as "to, at least,
detect," to, at least, provide," "to, at least, transmit," and so
on.
[0163] The above description of illustrated embodiments, including
what is described in the Abstract, is not intended to be exhaustive
or to limit the embodiments to the precise forms disclosed.
Although specific embodiments of and examples are described herein
for illustrative purposes, various equivalent modifications can be
made without departing from the spirit and scope of the disclosure,
as will be recognized by those skilled in the relevant art. The
teachings provided herein of the various embodiments can be applied
to other portable and/or wearable electronic devices, not
necessarily the exemplary wearable electronic devices generally
described above.
[0164] The various embodiments described above can be combined to
provide further embodiments. To the extent that they are not
inconsistent with the specific teachings and definitions herein,
all of the U.S. patents, U.S. patent application publications, U.S.
patent applications, foreign patents, foreign patent applications
and non-patent publications referred to in this specification
and/or listed in the Application Data Sheet which are owned by
Thalmic Labs Inc., including but not limited to: US Patent
Application Publication No. US 2017-0068095 A1, US Patent
Application Publication No. US 2017-0212290 A1, U.S. Provisional
Patent Application Ser. No. 62/487,303, U.S. Provisional Patent
Application Ser. No. 62/534,099, U.S. Provisional Patent
Application Ser. No. 62/565,677, U.S. Provisional Patent
Application Ser. No. 62/482,062, and U.S. Provisional Patent
Application Ser. No. 62/593,073 are incorporated herein by
reference, in their entirety. Aspects of the embodiments can be
modified, if necessary, to employ systems, circuits and concepts of
the various patents, applications and publications to provide yet
further embodiments.
[0165] These and other changes can be made to the embodiments in
light of the above-detailed description. In general, in the
following claims, the terms used should not be construed to limit
the claims to the specific embodiments disclosed in the
specification and the claims, but should be construed to include
all possible embodiments along with the full scope of equivalents
to which such claims are entitled. Accordingly, the claims are not
limited by the disclosure.
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