U.S. patent application number 16/276038 was filed with the patent office on 2019-08-15 for systems, devices, and methods for side lobe control in holograms.
The applicant listed for this patent is North Inc.. Invention is credited to Robin W. Tsen.
Application Number | 20190250562 16/276038 |
Document ID | / |
Family ID | 67540484 |
Filed Date | 2019-08-15 |
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United States Patent
Application |
20190250562 |
Kind Code |
A1 |
Tsen; Robin W. |
August 15, 2019 |
SYSTEMS, DEVICES, AND METHODS FOR SIDE LOBE CONTROL IN
HOLOGRAMS
Abstract
Systems, devices, and methods for side lobe control in holograms
are described. The magnitude of the side lobes of a hologram
depends on the distribution of refractive index modulation
(.DELTA.n), therefore control of side lobe magnitude may be
achieved by controlling the distribution of .DELTA.n. The
distribution of .DELTA.n may be controlled by replicating a
hologram from a master with two reference beams, where the
wavelength and angle of each reference beam, the playback angle of
the master hologram, and the thickness of the master hologram, the
copy holographic recording medium (HRM), and the recording
substrate are carefully chosen to achieve a pattern of
meta-interference within the HRM that matches the desired
distribution of .DELTA.n.
Inventors: |
Tsen; Robin W.; (Kitchener,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
North Inc. |
Kitchener |
|
CA |
|
|
Family ID: |
67540484 |
Appl. No.: |
16/276038 |
Filed: |
February 14, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62631278 |
Feb 15, 2018 |
|
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62664758 |
Apr 30, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03H 1/0236 20130101;
G02B 27/0172 20130101; G02B 2027/0174 20130101; G03H 2001/026
20130101; G03H 1/02 20130101; G03H 1/2645 20130101; G03H 1/26
20130101; G03H 2001/0489 20130101; G03H 2222/13 20130101; G03H
1/0248 20130101; G03H 2001/0212 20130101; G03H 2001/0439 20130101;
G03H 1/202 20130101; G02B 2027/0178 20130101; G03H 2001/266
20130101; G03H 1/28 20130101; G03H 1/0486 20130101 |
International
Class: |
G03H 1/26 20060101
G03H001/26; G02B 27/01 20060101 G02B027/01; G03H 1/02 20060101
G03H001/02 |
Claims
1. A hologram with controlled side lobes comprising: a first
surface; a second surface opposite the first surface; an initial
set of fringes within the volume of the hologram, the initial set
of fringes comprising an initial fringe phase, an initial fringe
spacing and an initial fringe slant angle; and at least one
additional set of fringes within the volume of the hologram,
wherein each additional set of fringes comprises a respective net
phase shift relative to the phase of the initial set of fringes, an
additional fringe spacing, and an additional fringe slant angle
wherein each additional fringe spacing is equal to the initial
fringe spacing, each additional fringe slant angle is not equal to
the initial fringe slant angle or any other additional fringe slant
angle, the initial set of fringes and all additional sets of
fringes meta-interfere, and the magnitude of .DELTA.n within the
hologram varies between the first surface and the second
surface.
2. The hologram of claim 1 wherein the intensity of each of the
side lobes is less than one percent of the intensity of the primary
hologram peak.
3. The hologram of claim 1 wherein the intensity of at least one of
the side lobes is greater than the intensity of the primary
hologram peak.
4. The hologram of claim 1 wherein: the initial set of fringes and
each additional set of fringes meta-interfere most constructively
at a depth through the hologram between the first surface and the
second surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially destructively at the
first surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially destructively at the
second surface; the magnitude of .DELTA.n at the first surface is
equal to or less than 50% of the greatest magnitude of .DELTA.n
within the hologram; and the magnitude of .DELTA.n at the second
surface is equal to or less than 50% of the greatest magnitude of
.DELTA.n within the hologram.
5. The hologram of claim 4 wherein the magnitude of .DELTA.n
increases continuously from the first surface to the maximum value
of .DELTA.n within the hologram and the magnitude of .DELTA.n
increases continuously from the second surface to the maximum value
of .DELTA.n within the hologram.
6. The hologram of claim 1 wherein: the initial set of fringes and
each additional set of fringes meta-interfere most destructively at
a depth through the hologram between the first surface and the
second surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially constructively at the
first surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially constructively at the
second surface; at least one of: the first surface and the second
surface possess the greatest magnitude of .DELTA.n; the minimum
magnitude of .DELTA.n within the volume of the hologram is no
greater than 50% of the greatest magnitude of .DELTA.n within the
hologram; and the magnitude of .DELTA.n decreases continuously from
the first surface to the minimum value of .DELTA.n within the
hologram and the magnitude of .DELTA.n decreases continuously from
the second surface to the minimum value of .DELTA.n within the
hologram.
7. The hologram of claim 1 wherein the hologram comprises a
wavelength-multiplexed hologram.
8. The hologram of claim 7 wherein the wavelength-multiplexed
hologram comprises a blue hologram, a green hologram, a red
hologram, and an infrared hologram.
9. The hologram of claim 8 wherein: the intensity of the side lobes
of the blue hologram relative to the intensity of primary peak of
the blue hologram is equal to the intensity of the side lobes of
the green hologram relative to the intensity of primary peak of the
green hologram; the intensity of the side lobes of the green
hologram relative to the intensity of primary peak of the green
hologram is equal to the intensity of the side lobes of the red
hologram relative to the intensity of primary peak of the red
hologram; and the intensity of the side lobes of the red hologram
relative to the intensity of primary peak of the red hologram is
equal to the intensity of the side lobes of the infrared hologram
relative to the intensity of primary peak of the infrared
hologram.
10. An eyeglass lens for use in a wearable heads-up display, the
eyeglass lens comprising: a hologram with controlled side lobes
comprising: a first surface; a second surface opposite the first
surface; an initial set of fringes within the volume of the
hologram comprising an initial fringe spacing and an initial slant
angle; and at least one additional set of fringes within the volume
of the hologram, wherein each additional set of fringes comprises a
respective net phase shift relative to the phase of the initial set
of fringes, an additional fringe spacing, and an additional fringe
slant angle wherein each additional fringe spacing is equal to the
initial fringe spacing, each additional fringe slant angle is not
equal to the initial fringe slant angle or any other additional
fringe slant angle, the initial set of fringes and all additional
sets of fringes meta-interfere, and the magnitude of .DELTA.n
within the hologram varies between the first surface and the second
surface; and at least one lens portion, wherein each lens portion
is physically coupled to the hologram with controlled side
lobes.
11. The lens of claim 10 wherein the intensity of each of the side
lobes of the hologram is less than one percent of the intensity of
the primary hologram peak.
12. The lens of claim 10 wherein the intensity of at least one of
the side lobes of the hologram is greater than the intensity of the
primary hologram peak.
13. The lens of claim 10 wherein the initial set of fringes and
each additional set of fringes meta-interfere most constructively
at a depth through the hologram between the first surface and the
second surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially destructively at the
first surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially destructively at the
second surface; the magnitude of .DELTA.n at the first surface is
equal to or less than 50% of the greatest magnitude of .DELTA.n
within the hologram; and the magnitude of .DELTA.n at the second
surface is equal to or less than 50% of the greatest magnitude of
.DELTA.n within the hologram.
14. The lens of claim 10 wherein the initial set of fringes and
each additional set of fringes meta-interfere most destructively at
a depth through the hologram between the first surface and the
second surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially constructively at the
first surface; the initial set of fringes and each additional set
of fringes meta-interfere at least partially constructively at the
second surface; at least one of: the first surface and the second
surface possess the greatest magnitude of .DELTA.n; the minimum
magnitude of .DELTA.n within the volume of the hologram is no
greater than 50% of the greatest magnitude of .DELTA.n within the
hologram; and the magnitude of .DELTA.n decreases continuously from
the first surface to the minimum value of .DELTA.n within the
hologram and the magnitude of .DELTA.n decreases continuously from
the second surface to the minimum value of .DELTA.n within the
hologram.
15. The lens of claim 10 wherein the hologram comprises a
wavelength-multiplexed hologram, the wavelength-multiplexed
hologram comprising a blue hologram, a green hologram, a red
hologram, and an infrared hologram.
16. A wearable heads-up display comprising: a support structure; a
projector; and a transparent combiner positioned and oriented to
appear in a field of view of an eye of a user when the support
structure is worn on a head of the user, the transparent combiner
comprising: a hologram with controlled side lobes comprising: a
first surface; a second surface opposite the first surface; an
initial set of fringes within the volume of the hologram comprising
an initial fringe spacing and an initial slant angle; and at least
one additional set of fringes within the volume of the hologram,
wherein each additional set of fringes comprises a given additional
fringe spacing and a given additional slant angle wherein each
additional fringe spacing is equal to the initial fringe spacing,
each additional slant angle is not equal to the initial slant angle
or any other additional slant angle, the initial set of fringes and
all additional sets of fringes meta-interfere, and the magnitude of
.DELTA.n within the hologram varies between the first surface and
the second surface; and at least one lens portion, wherein each
lens portion is physically coupled to the hologram with controlled
side lobes.
17. The wearable heads-up display of claim 16 wherein the intensity
of each of the side lobes of the hologram is less than one percent
of the intensity of the primary hologram peak.
18. The wearable heads-up display of claim 16 wherein the intensity
of at least one of the side lobes of the hologram is greater than
the intensity of the primary hologram peak.
19. The wearable heads-up display of claim 16 wherein the initial
set of fringes and each additional set of fringes meta-interfere
most constructively at a depth through the hologram between the
first surface and the second surface; the initial set of fringes
and each additional set of fringes meta-interfere at least
partially destructively at the first surface; the initial set of
fringes and each additional set of fringes meta-interfere at least
partially destructively at the second surface; the magnitude of
.DELTA.n at the first surface is equal to or less than 50% of the
greatest magnitude of .DELTA.n within the hologram; and the
magnitude of .DELTA.n at the second surface is equal to or less
than 50% of the greatest magnitude of .DELTA.n within the
hologram.
20. The wearable heads-up display of claim 16 wherein the initial
set of fringes and each additional set of fringes meta-interfere
most destructively at a depth through the hologram between the
first surface and the second surface; the initial set of fringes
and each additional set of fringes meta-interfere at least
partially constructively at the first surface; the initial set of
fringes and each additional set of fringes meta-interfere at least
partially constructively at the second surface; at least one of:
the first surface and the second surface possess the greatest
magnitude of .DELTA.n; the minimum magnitude of .DELTA.n within the
volume of the hologram is no greater than 50% of the greatest
magnitude of .DELTA.n within the hologram; and the magnitude of
.DELTA.n decreases continuously from the first surface to the
minimum value of .DELTA.n within the hologram and the magnitude of
.DELTA.n decreases continuously from the second surface to the
minimum value of .DELTA.n within the hologram.
21. The wearable heads-up display of claim 16 wherein the hologram
comprises a wavelength-multiplexed hologram, the
wavelength-multiplexed hologram comprising a blue hologram, a green
hologram, a red hologram, and an infrared hologram.
Description
TECHNICAL FIELD
[0001] The present systems, devices, and methods generally relate
to holograms and particularly relate to controlling the side lobes
in holograms.
BACKGROUND
Description of the Related Art
[0002] Holograms
[0003] A hologram is a recording of a light field, with a typical
light field comprising a pattern of optical fringes generated by
interference between 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.
[0004] During hologram playback, 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 the first beam of laser light used to
record the hologram, and the fringes have not been altered after
recording, the holographic medium will diffract laser light with
the same angle and pattern as the second beam of laser light used
to record the hologram. The intensity of the diffracted light is
determined by the efficiency of the hologram, where the efficiency
of the hologram is the fraction of the light of the first beam of
laser light that is diffracted in the direction of the second beam
of laser light; hologram efficiency may be in a range from 0-100%.
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.
[0005] Hologram Recording
[0006] 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.
[0007] 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.
[0008] Wearable Heads-Up Displays
[0009] A head-mounted display is an electronic device that is worn
on a user's head and, when so worn, secures at least one electronic
display within a viewable field of at least one of the user's eyes,
regardless of the position or orientation of the user's head. A
wearable heads-up display is a head-mounted display that enables
the user to see displayed content but also does not prevent the
user from being able to see their external environment. The
"display" component of a wearable heads-up display is either
transparent or at a periphery of the user's field of view so that
it does not completely block the user from being able to see their
external environment. Examples of wearable heads-up displays
include: the Google Glass.RTM., the Optinvent Ora.RTM., the Epson
Moverio.RTM., and the Sony Glasstron.RTM., just to name a few.
[0010] The optical performance of a wearable heads-up display is an
important factor in its design. When it comes to face-worn devices,
however, users also care a lot about aesthetics. This is clearly
highlighted by the immensity of the eyeglass (including sunglass)
frame industry. Independent of their performance limitations, many
of the aforementioned examples of wearable heads-up displays have
struggled to find traction in consumer markets because, at least in
part, they lack fashion appeal. Most wearable heads-up displays
presented to date employ large display components and, as a result,
most wearable heads-up displays presented to date are considerably
bulkier and less stylish than conventional eyeglass frames.
[0011] A challenge in the design of wearable heads-up displays is
to minimize the bulk of the face-worn apparatus will still
providing displayed content with sufficient visual quality. There
is a need in the art for wearable heads-up displays of more
aesthetically-appealing design that are capable of providing
high-quality images to the user without limiting the user's ability
to see their external environment.
BRIEF SUMMARY
[0012] A method of producing a hologram with controlled side lobes
may be summarized as including: providing a recording substrate
comprising a first surface and a second surface opposite the first
surface; mounting a master hologram on the first surface of the
recording substrate; mounting a holographic recording material
("HRM") on the second surface of the recording substrate;
replicating the master hologram within the HRM with at least two
reference beams to produce a hologram with controlled side lobes,
wherein the hologram with controlled side lobes comprises a first
surface and a second surface opposite the first surface; and
dismounting the hologram with controlled side lobes from the
recording substrate.
[0013] The method may further include replicating the master
hologram within the HRM with at least two reference beams to
produce a hologram with controlled side lobes includes replicating
the master hologram within the HRM with at least two reference
beams to produce a hologram wherein the intensity of each of the
side lobes is less than one percent of the intensity of the primary
hologram peak. The method may further include replicating the
master hologram within the HRM with at least two reference beams to
produce a hologram with controlled side lobes includes replicating
the master hologram within the HRM with at least two reference
beams to produce a hologram wherein the intensity of at least one
of the side lobes is greater than the intensity of the primary
hologram peak. The method may further include The method of claim
1, further comprising bleaching the hologram with controlled side
lobes. The method may further include recording a master hologram.
The method may further include replicating the master hologram
within the HRM with at least two reference beams to produce a
hologram with controlled side lobes includes replicating the master
hologram with at least two reference beams wherein each reference
beam is of a different angle than each other reference beam. The
method may further include replicating the master hologram within
the HRM with at least two reference beams to produce a hologram
with controlled side lobes includes replicating the master hologram
with at least two reference beams wherein each reference beam is of
a different wavelength than each other reference beam. The method
may further include replicating the master hologram within the HRM
with at least two reference beams to produce a hologram with
controlled side lobes includes replicating a wavelength-multiplexed
master hologram with at least two reference beams to produce a
wavelength-multiplexed hologram with controlled side lobes.
[0014] The wavelength multiplexed hologram with controlled side
lobes may comprise a blue hologram, a red hologram, and a green
hologram, and replicating a wavelength-multiplexed master hologram
with at least two reference beams to produce a
wavelength-multiplexed hologram with controlled side lobes may
include replicating a wavelength-multiplexed master hologram
comprising a blue master hologram, a red master hologram, and a
green master hologram.
[0015] Replicating a wavelength-multiplexed master hologram
comprising a blue master hologram, a red master hologram, and a
green master hologram may include replicating a
wavelength-multiplexed master hologram comprising a blue master
hologram, a red master hologram, and a green master hologram
wherein the bandwidth of the red master hologram is greater than
the bandwidth of the green master hologram, and the bandwidth of
the green master hologram may be greater than the bandwidth of the
blue master hologram. Replicating a wavelength-multiplexed master
hologram may include replicating a wavelength-multiplexed master
hologram with at least two blue beams of laser light, at least two
green beams of laser light, and at least two red beams of laser
light.
[0016] Replicating a wavelength-multiplexed master hologram with at
least two blue beams of laser light, at least two green beams of
laser light, and at least two red beams of laser light may include:
replicating the wavelength-multiplexed master hologram with two
blue beams of laser light wherein the two blue beams of laser light
differ in wavelength by a first .DELTA..lamda.; replicating the
wavelength-multiplexed master hologram with two green beams of
laser light wherein the two green beams of laser light differ in
wavelength by a second .DELTA..lamda.; and replicating the
wavelength-multiplexed master hologram with two red beams of laser
light wherein the two red beams of laser light differ in wavelength
by a third .DELTA..lamda.; wherein the first .DELTA.A may be less
than the second .DELTA..lamda. and the second .DELTA..lamda. may be
less than the third .DELTA..lamda..
[0017] Replicating the master hologram within the HRM with at least
two reference beams to produce a hologram with controlled side
lobes may include replicating the master hologram with at least two
reference beams to record an initial set of fringes and at least
one additional set of fringes within the HRM, wherein the initial
set of fringes may possess a phase within the HRM, each additional
set of fringes may possess a net phase shift relative to the
initial set of fringes within the HRM, and wherein the initial set
of fringes and each additional set of fringes may
meta-interfere.
[0018] Replicating the master hologram with at least two reference
beams to record an initial set of fringes and at least one
additional set of fringes within the HRM may include replicating
the master hologram with at least two reference beams to record an
initial set of fringes and at least one additional set of fringes
within the HRM wherein: the initial set of fringes and each
additional set of fringes may meta-interfere most destructively at
a depth within the hologram corresponding to at least one of: the
first surface and the second surface; and the initial set of
fringes and each additional set of fringes may meta-interfere most
constructively at a depth between the first surface and the second
surface.
[0019] Replicating the master hologram with at least two reference
beams to record an initial set of fringes and at least one
additional set of fringes within the HRM may include replicating
the master hologram with at least two reference beams to record an
initial set of fringes and at least one additional set of fringes
within the HRM wherein: the initial set of fringes and each
additional set of fringes may meta-interfere most constructively at
a depth within the hologram corresponding to at least one of: the
first surface and the second surface; and the initial set of
fringes and each additional set of fringes may meta-interfere most
destructively at a depth between the first surface and the second
surface.
[0020] The master hologram may possess a Bragg peak wavelength,
each reference beam may possess a reference beam wavelength, and
wherein replicating the master hologram within the HRM with at
least two reference beams to produce a hologram with controlled
side lobes may include replicating the master hologram within the
HRM with at least two reference beams to produce a hologram with
controlled side lobes wherein the difference between the Bragg peak
wavelength of the master hologram and reference beam wavelength of
each reference beam may be less than 2 nanometers.
[0021] Replicating the master hologram within the HRM with at least
two reference beams to produce a hologram with controlled side
lobes may include replicating the master hologram within the HRM
with at least two reference beams to produce a hologram with
controlled side lobes wherein at least one of the reference beams
may comprise a plane wave. Replicating the master hologram within
the HRM with at least two reference beams to produce a hologram
with controlled side lobes may include replicating the master
hologram within the HRM with at least two reference beams to
produce a hologram with controlled side lobes wherein at least one
of the reference beams comprises a spherical wave.
[0022] A hologram with controlled side lobes may be summarized as
including: a first surface; a second surface opposite the first
surface; an initial set of fringes within the volume of the
hologram, the initial set of fringes comprising an initial fringe
phase, an initial fringe spacing and an initial fringe slant angle;
and at least one additional set of fringes within the volume of the
hologram, wherein each additional set of fringes comprises a
respective net phase shift relative to the phase of the initial set
of fringes, an additional fringe spacing, and an additional fringe
slant angle wherein each additional fringe spacing is equal to the
initial fringe spacing, each additional fringe slant angle is not
equal to the initial fringe slant angle or any other additional
fringe slant angle, the initial set of fringes and all additional
sets of fringes meta-interfere, and the magnitude of .DELTA.n
within the hologram varies between the first surface and the second
surface.
[0023] The intensity of each of the side lobes may be less than one
percent of the intensity of the primary hologram peak. The
intensity of at least one of the side lobes may greater than the
intensity of the primary hologram peak. The hologram may further
include: the initial set of fringes and each additional set of
fringes may meta-interfere most constructively at a depth through
the hologram between the first surface and the second surface; the
initial set of fringes and each additional set of fringes may
meta-interfere at least partially destructively at the first
surface; the initial set of fringes and each additional set of
fringes may meta-interfere at least partially destructively at the
second surface; the magnitude of .DELTA.n at the first surface may
be equal to or less than 50% of the greatest magnitude of .DELTA.n
within the hologram; and the magnitude of .DELTA.n at the second
surface may be equal to or less than 50% of the greatest magnitude
of .DELTA.n within the hologram. The magnitude of .DELTA.n may
increase continuously from the first surface to the maximum value
of .DELTA.n within the hologram and the magnitude of .DELTA.n may
increase continuously from the second surface to the maximum value
of .DELTA.n within the hologram. The hologram may include: the
initial set of fringes and each additional set of fringes may
meta-interfere most destructively at a depth through the hologram
between the first surface and the second surface; the initial set
of fringes and each additional set of fringes may meta-interfere at
least partially constructively at the first surface; the initial
set of fringes and each additional set of fringes may
meta-interfere at least partially constructively at the second
surface; at least one of: the first surface and the second surface
may possess the greatest magnitude of .DELTA.n; the minimum
magnitude of .DELTA.n within the volume of the hologram may be no
greater than 50% of the greatest magnitude of .DELTA.n within the
hologram; and the magnitude of .DELTA.n may decreases continuously
from the first surface to the minimum value of .DELTA.n within the
hologram and the magnitude of .DELTA.n decreases continuously from
the second surface to the minimum value of .DELTA.n within the
hologram.
[0024] The hologram may comprise a wavelength-multiplexed hologram.
The wavelength-multiplexed hologram may comprises a blue hologram,
a green hologram, a red hologram, and an infrared hologram. The
hologram may further include: the intensity of the side lobes of
the blue hologram relative to the intensity of primary peak of the
blue hologram may be equal to the intensity of the side lobes of
the green hologram relative to the intensity of primary peak of the
green hologram; the intensity of the side lobes of the green
hologram relative to the intensity of primary peak of the green
hologram may be equal to the intensity of the side lobes of the red
hologram relative to the intensity of primary peak of the red
hologram; and the intensity of the side lobes of the red hologram
relative to the intensity of primary peak of the red hologram may
be equal to the intensity of the side lobes of the infrared
hologram relative to the intensity of primary peak of the infrared
hologram.
[0025] A hologram with controlled side lobes recording system may
be summarized as including: a recording substrate comprising a
master-side surface and copy-side surface; a copy holographic
recording medium ("HRM") comprising a first copy HRM surface and a
second copy HRM surface, wherein the first copy surface is
physically coupled to the copy HRM-side surface of the recording
substrate; a master hologram comprising master hologram fringes
wherein the master hologram is physically coupled to the
master-side surface; a laser light source; a first reference beam
produced by the laser light source, wherein the first reference
beam passes through the copy HRM, passes through the recording
substrate, and impinges on the master hologram; a second reference
beam produced by the laser light source, wherein the second
reference beam passes through the copy HRM, passes through the
recording substrate, and impinges on the master hologram; a first
diffracted object beam, wherein the first diffracted object beam
passes through the recording substrate and passes through the copy
HRM; and a second diffracted object beam, wherein the second
diffracted object beam passes through the recording substrate and
passes through the copy HRM.
[0026] The second reference beam may be of a different wavelength
than the first reference beam. The second reference beam may be of
a different angle than the first reference beam. The first
reference beam and the first diffracted object beam may interfere
to produce an initial set of fringes, the second reference beam and
the second diffracted object beam may interfere to form an
additional set of fringes, and the initial set of fringes and the
additional set of fringes may meta-interfere. The initial set of
fringes and each additional set of fringes may meta-interfere most
destructively at a depth within the hologram corresponding to at
least one of: the first copy HRM surface and the second copy HRM
surface and the initial set of fringes and each additional set of
fringes may meta-interfere most constructively at a depth
equidistant between the first copy HRM surface and the second copy
HRM surface. The initial set of fringes and each additional set of
fringes may meta-interfere most constructively at a depth within
the hologram corresponding to at least one of: the first copy HRM
surface and the second copy HRM surface and the initial set of
fringes and each additional set of fringes may meta-interfere most
destructively at a depth equidistant between the first copy HRM
surface and the second copy HRM surface.
[0027] The master hologram may comprise a wavelength-multiplexed
master hologram, the wavelength-multiplexed master hologram
comprising: a red hologram; a green hologram; and a blue hologram;
and wherein the hologram with controlled side lobes recording
system may further comprise: at least two blue reference beams; at
least two green reference beams; and at least two red reference
beams.
[0028] An eyeglass lens for use in a wearable heads-up display may
be summarized as including: a hologram with controlled side lobes
comprising: a first surface; a second surface opposite the first
surface; an initial set of fringes within the volume of the
hologram comprising an initial fringe spacing and an initial slant
angle; and at least one additional set of fringes within the volume
of the hologram, wherein each additional set of fringes comprises a
respective net phase shift relative to the phase of the initial set
of fringes, an additional fringe spacing, and an additional fringe
slant angle wherein each additional fringe spacing is equal to the
initial fringe spacing, each additional fringe slant angle is not
equal to the initial fringe slant angle or any other additional
fringe slant angle, the initial set of fringes and all additional
sets of fringes meta-interfere, and the magnitude of .DELTA.n
within the hologram varies between the first surface and the second
surface; and at least one lens portion, wherein each lens portion
is physically coupled to the hologram with controlled side
lobes.
[0029] The intensity of each of the side lobes of the hologram may
be less than one percent of the intensity of the primary hologram
peak. The intensity of at least one of the side lobes of the
hologram may be greater than the intensity of the primary hologram
peak. The initial set of fringes and each additional set of fringes
may meta-interfere most constructively at a depth through the
hologram between the first surface and the second surface; the
initial set of fringes and each additional set of fringes may
meta-interfere at least partially destructively at the first
surface; the initial set of fringes and each additional set of
fringes may meta-interfere at least partially destructively at the
second surface; the magnitude of .DELTA.n at the first surface may
be equal to or less than 50% of the greatest magnitude of .DELTA.n
within the hologram; and the magnitude of .DELTA.n at the second
surface may be equal to or less than 50% of the greatest magnitude
of .DELTA.n within the hologram. The initial set of fringes and
each additional set of fringes may meta-interfere most
destructively at a depth through the hologram between the first
surface and the second surface; the initial set of fringes and each
additional set of fringes may meta-interfere at least partially
constructively at the first surface; the initial set of fringes and
each additional set of fringes may meta-interfere at least
partially constructively at the second surface; at least one of:
the first surface and the second surface may possess the greatest
magnitude of .DELTA.n; the minimum magnitude of .DELTA.n within the
volume of the hologram may be no greater than 50% of the greatest
magnitude of .DELTA.n within the hologram; and the magnitude of
.DELTA.n may decrease continuously from the first surface to the
minimum value of .DELTA.n within the hologram and the magnitude of
.DELTA.n decreases continuously from the second surface to the
minimum value of .DELTA.n within the hologram. The hologram may
include a wavelength-multiplexed hologram, the
wavelength-multiplexed hologram comprising a blue hologram, a green
hologram, a red hologram, and an infrared hologram.
[0030] A wearable heads-up display may be summarized as including:
a support structure; a projector; and a transparent combiner
positioned and oriented to appear in a field of view of an eye of a
user when the support structure is worn on a head of the user, the
transparent combiner comprising: a hologram with controlled side
lobes comprising: a first surface; a second surface opposite the
first surface; an initial set of fringes within the volume of the
hologram comprising an initial fringe spacing and an initial slant
angle; and at least one additional set of fringes within the volume
of the hologram, wherein each additional set of fringes comprises a
given additional fringe spacing and a given additional slant angle
wherein each additional fringe spacing is equal to the initial
fringe spacing, each additional slant angle is not equal to the
initial slant angle or any other additional slant angle, the
initial set of fringes and all additional sets of fringes
meta-interfere, and the magnitude of .DELTA.n within the hologram
varies between the first surface and the second surface; and at
least one lens portion, wherein each lens portion is physically
coupled to the hologram with controlled side lobes.
[0031] The intensity of each of the side lobes of the hologram may
be less than one percent of the intensity of the primary hologram
peak. The intensity of at least one of the side lobes of the
hologram may be greater than the intensity of the primary hologram
peak. The initial set of fringes and each additional set of fringes
may meta-interfere most constructively at a depth through the
hologram between the first surface and the second surface; the
initial set of fringes and each additional set of fringes may
meta-interfere at least partially destructively at the first
surface; the initial set of fringes and each additional set of
fringes may meta-interfere at least partially destructively at the
second surface; the magnitude of .DELTA.n at the first surface may
be equal to or less than 50% of the greatest magnitude of .DELTA.n
within the hologram; and the magnitude of .DELTA.n at the second
surface may be equal to or less than 50% of the greatest magnitude
of .DELTA.n within the hologram. The initial set of fringes and
each additional set of fringes may meta-interfere most
destructively at a depth through the hologram between the first
surface and the second surface; the initial set of fringes and each
additional set of fringes may meta-interfere at least partially
constructively at the first surface; the initial set of fringes and
each additional set of fringes may meta-interfere at least
partially constructively at the second surface; at least one of:
the first surface and the second surface may possess the greatest
magnitude of .DELTA.n; the minimum magnitude of .DELTA.n within the
volume of the hologram may be no greater than 50% of the greatest
magnitude of .DELTA.n within the hologram; and the magnitude of
.DELTA.n may decrease continuously from the first surface to the
minimum value of .DELTA.n within the hologram and the magnitude of
.DELTA.n may decrease continuously from the second surface to the
minimum value of .DELTA.n within the hologram. The hologram may
comprise a wavelength-multiplexed hologram, the
wavelength-multiplexed hologram comprising a blue hologram, a green
hologram, a red hologram, and an infrared hologram.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0032] 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.
[0033] FIG. 1 is a flow-diagram showing a method of producing a
hologram with controlled side lobes in accordance with the present
systems, devices, and methods.
[0034] FIG. 2 is a cross-sectional view of hologram with controlled
side lobes in accordance with the present systems, devices, and
methods.
[0035] FIG. 3A is a cross-sectional view of hologram with unmatched
fringe spacing in accordance with the present systems, devices, and
methods.
[0036] FIG. 3B is a cross-sectional view of hologram with unmatched
phase in accordance with the present systems, devices, and
methods.
[0037] FIG. 4 is a cross-sectional view of hologram with controlled
side lobes recording system in accordance with the present systems,
devices, and methods.
[0038] FIG. 5 is a cross-sectional view of an exemplary eyeglass
lens with an embedded hologram with controlled side lobes suitable
for use as a transparent combiner in a WHUD in accordance with the
present systems, devices, and methods.
[0039] FIG. 6 is a partial-cutaway perspective view of a WHUD that
includes an eyeglass lens with an embedded hologram with controlled
side lobes in accordance with the present systems, devices, and
methods.
[0040] FIG. 7 is a cross-sectional view of hologram with controlled
side lobes in accordance with the present systems, devices, and
methods.
[0041] FIG. 8 is a cross-sectional view of an exemplary eyeglass
lens with comprising a light guide and a hologram with controlled
side lobes in accordance with the present systems, devices, and
methods.
DETAILED DESCRIPTION
[0042] 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.
[0043] 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."
[0044] 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.
[0045] 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.
[0046] The headings and Abstract of the Disclosure provided herein
are for convenience only and do not interpret the scope or meaning
of the embodiments.
[0047] The various embodiments described herein provide systems,
devices, and methods for side lobe control in holograms and are
particularly well-suited for use in wearable heads-up displays
(WHUDs).
[0048] A hologram is a repeating pattern of physical fringes that,
when illuminated with coherent light with the same wavelength and
angle as one of the lasers used to record the fringes, diffracts at
least a portion of the incident light at an angle equal to the
angle of the other laser used to record the physical fringes; the
wavelength of the light remains unchanged. Physical fringes may
comprise local maxima (or minima) of refractive index within a
recorded hologram. Physical fringes are the physical structures
that comprise the recorded hologram.
[0049] A holographic optical element (HOE) comprises a hologram. A
HOE may comprise one or more cover sheets. A cover sheet comprises
a transparent material physically coupled to a surface of the
hologram, cover sheets are advantageous as they may improve the
strength, durability, scratch resistance, or ease of adhesion of
the HOE.
[0050] A hologram may be recorded within a holographic recording
medium (HRM). A HRM comprises photosensitive material which
undergoes a chemical or physical change upon exposure to light.
When a HRM is exposed to a pattern of optical fringes, the
photosensitive material records the pattern of optical fringes as a
pattern of physical fringes. HRMs are typically physically coupled
to at least one transparent support covering at least one surface
of the HRM. The transparent support maintains the shape of the HRM
before, during, and after hologram recording; the transparent
support may also protect the HRM from damage. Non-exclusive
examples of materials which may comprise a transparent support
include glass, polycarbonate, polystyrene, acrylic, or other
optical plastic materials.
[0051] HRMs are typically flat, planar materials with a thickness
less than 0.1 mm; however, HRMs may have a thickness of up to 1 mm
and may be curved. A curved surface may be a spherically curved
surface; a spherically curved surface is curved around a center of
curvature. A curved surface may be a cylindrically curved surface;
a cylindrically curved surface is curved around an axis of
curvature. The center or axis of curvature, as appropriate, of the
HRM may be located at a distance of between 1 and 10 centimeters,
between 10 and 50 cm, or between 50 and 100 cm from the surface of
the HRM.
[0052] A side lobe in a hologram is a local maximum adjacent to the
primary peak in a plot of hologram efficiency versus either
wavelength or angle of incidence. Side lobes may arise from the
sharp difference in refractive index modulation (.DELTA.n) between
where the hologram is recorded within the HOE and where the
hologram is not recorded within the transparent support. .DELTA.n
(i.e., refractive index modulation) is the difference between the
highest and lowest refractive indices in a recorded hologram.
[0053] In a typical hologram, .DELTA.n as a function of depth
through the hologram can be described by a square-wave function.
Within a hologram, depth is the distance from a surface of the
hologram to a point within the hologram measured in the z
direction, where the z direction is normal to the surface of the
plane, cylinder, or sphere of the hologram film (for planar,
cylindrical, and spherical holograms, respectively).
[0054] Since the efficiency of the hologram with respect to either
wavelength or angle is the Fourier transform of .DELTA.n as a
function of depth, the efficiency response of a typical hologram is
the Fourier transform of a square wave function. A sinc function
(an abbreviation of "sine cardinal function") is a mathematical
function that describes the Fourier transform of a square wave
function; a sinc squared function is the square of a sinc function.
A sinc squared function possesses a primary peak and multiple side
lobes, therefore a hologram with a .DELTA.n profile equivalent to a
square-wave function also has side lobes.
[0055] The presence of side lobes in a hologram may create a number
of potential problems. A hologram recorded at a particular
wavelength will be responsive to wavelengths outside the desired
primary playback wavelength and therefore produce playback light
when illuminated with light with a wavelength higher or lower than
the wavelength used to record the hologram. Playback is the process
of illuminating a hologram with light that replicates the reference
beam in order to replicate the object beam. The reference beam is
one of the laser beams used to record the hologram, the object beam
is another laser used to record the hologram.
[0056] For example, a hologram recorded with green laser light
could produce playback light when illuminated with blue laser light
if the blue laser light is of a wavelength corresponding to one of
the side lobes of the hologram recorded with green laser light; the
same green hologram may also produce playback light when
illuminating the hologram with red laser light matching another
side lobe of the green hologram. The playback light produced by the
side lobes will have a different playback angle than the playback
light produced by the primary peak.
[0057] The creation of additional playback beams at multiple angles
due to side lobes is problematic when a hologram is used in a
holographic display, including a holographic WHUD. If the
additional playback beams are able to enter the eye of the user,
the additional playback beams create secondary visible images
displaced in space from the primary image being produced by the
display. These additional images are typically lower in intensity
than the main image and are referred to as "ghost images". Ghost
images may reduce the resolution of the display by blurring any
images produced by the display, and ghost images may also occlude
the primary images of the display if the ghost image produced by
one portion of the primary image overlaps another portion of the
primary image.
[0058] Ghost image formation may be reduced or eliminated by
reducing or eliminating, respectively, the presence of side lobes
in the hologram. Softening the edges of the .DELTA.n profile as a
function of depth reduces the strength of the side lobes. Apodizing
the .DELTA.n profile as a function of depth significantly reduces
or eliminates the presence of side lobes. An apodized hologram is a
hologram with a minimum value of .DELTA.n at both the maximum and
minimum depth of the hologram, a maximum value of .DELTA.n at some
intermediate depth of the hologram, and no observable local maxima
or minima of .DELTA.n through the depth of the hologram.
Alternatively, if side lobes are desired, the side lobes could be
accentuated by anti-apodizing the .DELTA.n profile as a function of
depth.
[0059] A hologram with controlled side lobes comprises a hologram
with side lobes that differ from the side lobes present in a
hologram recorded with a single reference beam; in other words a
hologram with controlled side lobes comprises a hologram with side
lobes that are either greater or lesser in magnitude than the side
lobes described by a sinc function.
[0060] Described herein is a method of producing holograms with
controlled side lobes, the resulting holograms, and components,
systems, and devices comprising holograms with controlled side
lobes.
[0061] FIG. 1 is a flow-diagram showing a method 100 of producing a
hologram with controlled side lobes 100 in accordance with the
present systems, devices, and methods. Method 100 includes five
acts 101, 102, 103, 104, and 105 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.
[0062] At 101, a recording substrate is provided. The recording
substrate comprises a first surface and a second surface. A master
hologram is a recorded hologram that may be used repeatedly to
replicate a hologram in a second (or copy) holographic recording
medium (HRM). Replication is the process of recording a copy
hologram using a master and includes contact and non-contact
copying, with contact copying being more typically used for mass
production. In contact copying, the master is affixed to a first
surface of a recording substrate.
[0063] A recording substrate is an inflexible transparent substrate
that defines the shape of a hologram during recording. Typical
recording substrates are flat and planar, however recording
substrates may be at least partially spherically curved and/or at
least partially cylindrically curved; typical recording substrate
materials include glass and polycarbonate. A HRM is affixed to a
second surface of the recording substrate, where the second surface
is opposite the first surface. A reference beam is passed through
the HRM, the substrate, and the master. The master diffracts at
least a portion of the reference beam to produce a diffracted
object beam. The diffracted object beam and the reference beam
interfere within the HRM, recording a hologram within the HRM that
is substantively similar to the hologram recorded within the
master.
[0064] Contact copying is advantageous because the minimal distance
between the master and the copy ensures that the path length
difference between the reference beam and diffracted object beam is
very small, allowing the use of less expensive laser light sources
with shorter coherence lengths. Since contact copying includes
physically coupling the master and copy hologram to the same
substrate, motion of the copy hologram relative to the master
hologram during recording is essentially eliminated and stringent
vibration control is no longer needed.
[0065] At 102, a master hologram is mounted on the first surface of
the recording substrate. Mounting the master hologram on the
recording substrate includes physically coupling the master
hologram to the first surface of the recording substrate.
[0066] At 103, a HRM is mounted on the recording substrate.
Mounting the HRM on the recording substrate includes physically
coupling the HRM to the second surface of the recording substrate,
wherein the second surface of the recording substrate is opposite
the first surface of the recording substrate.
[0067] At 104, the master hologram is replicated within the HRM
with at least two reference beams to produce a hologram with
controlled side lobes. The at least two reference beams may each be
of a different wavelength than each other reference beam. The at
least two reference beams may each be of a different angle than
each other reference beam.
[0068] Replicating the master hologram within the HRM with at least
two reference beams to produce a hologram with controlled side
lobes may include replicating the master hologram within the HRM
with at least two reference beams to produce a hologram wherein the
intensity of the side lobes is less than 25%, less than 10%, or
less than one percent of the intensity of the primary hologram
peak. Side lobes with minimal intensity relative to the primary
hologram peak may be produced by apodizing the distribution of
.DELTA.n as a function of depth within the hologram. Replicating
the master hologram within the HRM with at least two reference
beams to produce a hologram with controlled side lobes may include
replicating the master hologram within the HRM with at least two
reference beams to produce a hologram wherein the intensity of at
least one of the side lobes is at least 25% of, at least 50% of, or
greater than the intensity of the primary hologram peak. Side lobes
with maximal intensity relative to the primary hologram peak may be
produced by anti-apodizing the distribution of .DELTA.n as a
function of depth within the hologram.
[0069] Replicating the master hologram with at least two reference
beams will produce at least two diffracted object beams; each of
the at least two diffracted object beams will interfere with each
of the at least two reference beams to produce at least two sets of
optical fringes (at least a portion of each set of optical fringes
is located within an internal volume of the HRM). The light
diffracted by the master hologram follows the diffraction grating
equation:
.lamda. n .LAMBDA. = sin .theta. 1 - sin .theta. 2 ##EQU00001##
[0070] where .lamda. is the wavelength of the laser light, .LAMBDA.
is the lateral grating spacing (of the optical fringes),
.theta..sub.1 is the angle of incidence (relative to the normal),
.theta..sub.2 is the angle of diffraction (relative to the normal),
and n is an integer. The lateral spacing of the fringes produced by
interference between incident light and any light produced by the
master hologram will be the same; any changes in incident
wavelength or angle will affect the angle of the diffracted light
(and therefore the angle of the resulting fringes) but not the
spacing of the resulting fringes. The fringe spacing is always the
same when replicating a single master with two laser beams, thus
the at least two sets of optical fringes will both possess the same
fringe spacing as the master hologram. The at least two sets of
optical fringes may be recorded within the HRM to form at least two
sets of physical fringes.
[0071] In other words, replicating the master hologram with at
least two reference beams includes illuminating the HRM and the
master hologram with at least two reference beams; during
replication the master hologram and the HRM are separated from one
another by the recording substrate. Replicating the master hologram
within the HRM includes passing each reference beam through the
HRM, the recording substrate, and the master hologram. Replicating
a transmission hologram includes passing each reference beam
through the master hologram prior to passing each reference beam
through the HRM. Replicating a reflection hologram includes passing
each reference beam through the HRM prior to passing each reference
beam through the master hologram.
[0072] Replication may include recording a pattern of fringes
within HRM that is substantively similar to the pattern of fringes
within the master hologram. During replication, each reference beam
possesses a phase within the HRM and each object beam possesses a
phase within the HRM. Both the reference beam and the object beam
must pass through the recording substrate, but the path length
through the recording substrate of the reference beam is not
necessarily equal to the path length through the recording
substrate of the object beam. The difference in path length between
the object beam and the reference beam causes a phase shift between
the object beam and the reference beam within the HRM. The phase of
the optical fringes produced by interference between the object
beam and the reference beam within the HRM depends on the phase
shift between the object beam and the reference beam.
[0073] Throughout this specification and the appended claims, the
term "meta-interference" refers to interference between sets of
fringes; each set of fringes may be the product of interference
between each reference beam and the respective object beam
diffracted from each reference beam. Replicating the master
hologram within the HRM with at least two reference beams produces
at least two sets of optical fringes that undergo
meta-interference. The meta-interference of the at least two sets
of optical fringes increases .DELTA.n in regions of constructive
meta-interference and decreases .DELTA.n in regions of destructive
meta-interference. The magnitude of the increase or decrease in
.DELTA.n depends on the magnitude of the constructive or
destructive meta-interference, respectively. The position of the
increased or decreased .DELTA.n within the HRM depends on the net
phase shift of each set of fringes, where the net phase shift of a
set of optical fringes is the relative difference in phase between
that set of optical fringes and another set of optical fringes
within the HRM.
[0074] Control over the side lobes of a hologram requires control
over the positions of high and low .DELTA.n within the HRM. Control
over the positions of high and low .DELTA.n within the HRM may be
achieved by controlling the precise angle and wavelength of each
reference beam employed during replication. The angle and
wavelength of each reference beam determines the phase shift of
each object beam, and therefore the phase of each set of optical
fringes, the net phase shift between each set of optical fringes,
the meta-interference between sets of optical fringes, and thereby
the positions of high and low .DELTA.n within the HRM.
[0075] Consider FIG. 2, which shows a cross-sectional view of
hologram with controlled side lobes 200 in accordance with the
present systems, devices, and methods. Hologram with controlled
side lobes 200 may be produced by method 100. Hologram with
controlled side lobes 200 comprises first set of fringes 210 and
second set of fringes 220. First set of fringes 210 and second set
of fringes 220 may be formed by replicating a master hologram with
two reference beams. First set of fringes 210 and second set of
fringes 220 have the same spacing but different angles, which
causes first set of fringes 210 and second set of fringes 220 to
interfere with each other. At the top and bottom surface of
hologram with controlled side lobes 200 first set of fringes 210
and second set of fringes 220 interfere destructively, reducing
.DELTA.n to a minimum. At the middle depth of hologram with
controlled side lobes 200 first set of fringes 210 and second set
of fringes 220 interfere constructively, increasing .DELTA.n to a
maximum. .DELTA.n increases smoothly from either surface of the
hologram towards the maximum. Hologram with controlled side lobes
200 is therefore apodized and will have minimal, if any, side
lobes. In order to achieve this smooth interference between sets of
fringes with a maximum .DELTA.n at a desired depth, the sets of
fringes must have precisely matched spacing and phase.
[0076] First set of fringes 210 may comprise an initial set of
fringes. Second set of fringes 220 may comprise an additional set
of fringes. A person of skill in the art will appreciate that for
the sake of clarity only two sets of fringes are depicted in Figure
two, however hologram with controlled side lobes 200 may comprise n
sets of fringes (where n is equal to or greater than 2) with one
initial set of fringes and n-1 additional sets of fringes, the
various sets of fringes having different angles and, or different
phase shifts from those of the other sets of fringes.
[0077] In some implementations, hologram 200 may be carried on or
by another structure, and such other structure may, for example,
provide at least some additional optical function. For instance,
one or more holograms 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 "hologram" may include a HRM layer and a combination of
optional additional layers or structures such as protective
material, waveguide/lightguide structures, substrates, etc.
depending on the specific implementation. Likewise, when the term
"hologram with controlled side lobes" is used, said hologram with
controlled side lobes may be carried on or by other structures or
layers, or may itself carry other structures or layers, depending
on the specific implementation.
[0078] Returning to FIG. 1, replicating the master hologram within
the HRM with at least two reference beams to produce a hologram
with controlled side lobes may include replicating a
wavelength-multiplexed master hologram with at least two reference
beams to produce a wavelength-multiplexed hologram with controlled
side lobes. A wavelength-multiplexed hologram is a hologram
comprising multiple wavelength-specific holograms. Each
wavelength-specific hologram comprising a wavelength-multiplexed
hologram diffracts laser light of a specific wavelength; a
wavelength-specific hologram cannot diffract light of a wavelength
outside of the spectral bandwidth of the wavelength-specific
hologram. Wavelength-multiplexed holograms are advantageous since a
wavelength-multiplexed hologram may be employed as a holographic
combiner in a WHUD with a full-color display; single-wavelength
holograms may be employed in monochromatic displays.
[0079] A wavelength-multiplexed master hologram may be replicated
to produce a wavelength-multiplexed hologram with controlled side
lobes. A wavelength-multiplexed master hologram may comprise a blue
master hologram, a green master hologram, and a red master
hologram. A wavelength-multiplexed hologram with controlled side
lobes may comprise a blue hologram with controlled side lobes, a
green hologram with controlled side lobes, and a red hologram with
controlled side lobes. A wavelength-multiplexed hologram with
controlled sidelobes may be replicated from a
wavelength-multiplexed master hologram with at least two blue beams
of laser light, at least two green beams of laser light, and at
least two red beams of laser light. Each beam of laser light used
to replicate a wavelength-multiplexed hologram with controlled
sidelobes from a wavelength-multiplexed possesses a respective
wavelength.
[0080] A blue wavelength-specific hologram with controlled
sidelobes comprising a wavelength-multiplexed hologram with
controlled sidelobes may be replicated from a
wavelength-multiplexed master with two blue beams of laser light,
where the two blue beams of laser light differ in wavelength by a
first .DELTA..lamda.. A green wavelength-specific hologram with
controlled sidelobes comprising a wavelength-multiplexed hologram
with controlled sidelobes may be replicated from a
wavelength-multiplexed master with two green beams of laser light,
where the two green beams of laser light differ in wavelength by a
second .DELTA..lamda.. A red wavelength-specific hologram with
controlled sidelobes comprising a wavelength-multiplexed hologram
with controlled sidelobes may be replicated from a
wavelength-multiplexed master with two red beams of laser light,
where the two red beams of laser light differ in wavelength by a
third .DELTA..lamda.. The first .DELTA..lamda. may be greater than,
less than, or equal to the second .DELTA..lamda.. The second
.DELTA..lamda. may be greater than, less than, or equal to the
third .DELTA..lamda.. A wavelength-multiplexed hologram with
controlled side lobes, where each wavelength-specific hologram has
the same intensity of side lobes relative to the intensity of the
primary hologram peak, may be replicated when the first
.DELTA..lamda. is highest and the third .DELTA..lamda. is
lowest.
[0081] The master hologram possesses a Bragg peak wavelength. Each
reference beam possesses a reference beam wavelength. Replicating
the master hologram within the HRM with at least two reference
beams to produce a hologram with controlled side lobes may include
replicating the master hologram within the HRM with at least two
reference beams to produce a hologram with controlled side lobes
wherein the difference between the Bragg peak wavelength of the
master hologram and reference beam wavelength of each reference
beam is less than 2 nanometers. Replicating the master hologram
with a reference beam wherein the difference between the Bragg peak
wavelength of the master hologram and the reference beam wavelength
is small is advantageous since the efficiency of the master
hologram may decrease significantly at wavelengths greater than 2
nanometers from the Bragg peak wavelength of the master hologram.
Significant changes in master hologram efficiency may cause
significant changes in the phase of any laser light diffracted by
the master hologram, and therefore make it difficult to control the
phase of the initial set of optical fringes and the net phase shift
of the additional sets of optical fringes within the HRM.
[0082] The bandwidth of a hologram is the range of angles and
wavelengths of incident laser light that the hologram efficiently
diffracts; bandwidth includes angular bandwidth and wavelength
bandwidth. The angular bandwidth of a hologram is the range of
angles of incident laser light that satisfies the Bragg condition
for the hologram and therefore may be efficiently diffracted by the
hologram. The wavelength bandwidth of a hologram is the range of
wavelengths of incident laser light that satisfies the Bragg
condition for the hologram and therefore may be efficiently
diffracted by the hologram. Typically, a hologram with a narrow
angular bandwidth also possesses a narrow wavelength bandwidth and
a hologram with a broad angular bandwidth also possesses a broad
wavelength bandwidth. Any process that increases or decreases the
angular bandwidth of a hologram will typically also proportionally
increase or decrease (respectively) the wavelength bandwidth of a
hologram. A person of skill of art will appreciate that the term
"bandwidth" therefore may refer either to the angular bandwidth or
the wavelength bandwidth of a hologram unless otherwise specified
as "angular bandwidth" or "wavelength bandwidth". Each
wavelength-specific hologram comprising a wavelength-multiplexed
hologram possesses its own bandwidth. In other words, for a
wavelength-multiplexed hologram comprising a blue hologram, a green
hologram, and a red hologram, the bandwidth of the blue hologram
may be greater than or less than the bandwidth of the green
hologram, and the bandwidth of the green hologram may be greater
than or less than the bandwidth of the red hologram. The phase
shift introduced to the diffracted object beam by the master
hologram due to the thickness of the master hologram depends on the
bandwidth of the master hologram. A hologram with broader bandwidth
will have a weaker dependence of phase shift on hologram thickness;
varying the bandwidth of the wavelength-specific holograms allows
further control of the phase shift of the respective diffracted
object beams and therefore the side lobes of the resulting
holograms.
[0083] Replicating the master hologram within the HRM with at least
two reference beams to produce a hologram with controlled side
lobes may include replicating the master hologram with at least two
reference beams to record an initial set of fringes and at least
one additional set of fringes within the HRM. The initial set of
fringes possesses a phase within the HRM. Each additional set of
fringes possesses a net phase shift relative to the initial set of
fringes within the HRM. The net phase shift between each additional
set of fringes and the initial set of fringes controls the
meta-interference between each additional set of fringes and the
initial set of fringes.
[0084] A person of skill in the art will appreciate that defining a
particular set of fringes as being an initial set of fringes (while
all other sets of fringes are additional fringes) is advantageous
as such a definition establishes a common frame of reference for
determining the phase of each set of fringes relative to each other
set of fringes. A determination of the relative phase of each set
of fringes may eliminate the need to determine the absolute phase
of any set of fringes.
[0085] Each set of fringes (initial or additional) will
meta-interfere with each other set of fringes within the HRM.
Constructive meta-interference between sets of fringes increases
.DELTA.n, while destructive meta-interference between sets of
fringes decreases .DELTA.n. The locations within the HRM where
fringes meta-interfere constructively or destructively depends on
the phase of the initial set of fringes within the HRM and the net
phase shift of the at least one additional set of fringes within
the HRM. The net phase shift of each additional set of fringes may
be expressed in radians. The net phase shift of each additional set
of fringes may be measured at a depth within the hologram
equidistant from the first surface and the second surface of the
HRM. A net phase shift of 0 will result in maximum constructive
meta-interference at a depth within the hologram equidistant from
the first surface and the second surface of the HRM and maximum
destructive meta-interference at the first surface and at the
second surface; in other words, a net phase shift of 0 will produce
an apodized hologram with minimized side lobes. A net phase shift
of .pi. will result in maximum destructive meta-interference at a
depth within the hologram equidistant from the first surface and
the second surface of the HRM and maximum constructive
meta-interference at the first surface and at the second surface;
in other words, a phase shift of .pi. will produce an anti-apodized
hologram with maximized side lobes.
[0086] Factors that determine the phase of the initial set of
fringes within the HRM include: the thickness of the recording
substrate, the refractive index of the recording substrate, the
thickness of the master hologram, the bandwidth of the master
hologram, the angle of the reference beam diffracted by the master
hologram to produce the initial set of fringes, and the wavelength
of the reference beam diffracted by the master hologram to produce
the initial set of fringes. Factors that determine the net phase
shift of each additional set of fringes within the HRM include: the
thickness of the recording substrate, the refractive index of the
recording substrate, the thickness of the master hologram, the
bandwidth of the master hologram, the angle of the reference beam
diffracted by the master hologram to produce each additional set of
fringes, and the wavelength of the reference beam diffracted by the
master hologram to produce each additional set of fringes.
[0087] Control over the side lobes of a hologram may be achieved by
controlling the factors that determine the phase of the initial set
of fringes within the HRM and by controlling the factors that
determine the net phase shift of each set of additional fringes
within the HRM. The thickness of the recording substrate may be
controlled by casting, milling, cutting, grinding, or otherwise
producing a recording substrate with a desired thickness. The
refractive index of the recording substrate may be controlled by
choosing a recording substrate material with a desired refractive
index. The thickness of the master hologram may be controlled by
recording the master hologram in a HRM with a desired thickness.
The bandwidth of the master hologram may be controlled by
controlling the thickness of the master hologram, where thicker
master holograms typically have a narrower bandwidth. The bandwidth
of the master hologram may be increased with bandwidth-broadening
treatments. The angle of a reference beam may be controlled by
positioning the laser light source for a given reference beam at a
desired angle. The wavelength of a reference beam may be controlled
by choosing a laser light source with appropriate wavelength
outputs; laser light sources with variable wavelength outputs may
have their output wavelength determined by the conditions under
which the variable output laser light source is operated.
[0088] A hologram with apodized .DELTA.n will have side lobes with
the least magnitude, and thereby comprises a hologram with
controlled side lobes. A hologram with apodized .DELTA.n comprises
a hologram wherein .DELTA.n is lowest at the shallowest and deepest
depth within the hologram and wherein .DELTA.n is highest at a
depth between the shallowest and deepest depth within the hologram.
In other words, .DELTA.n is lowest at the first and second surface
of the hologram and .DELTA.n is highest at a depth between the
first and second surface. A hologram with anti-apodized .DELTA.n
will have side lobes with the greatest magnitude, and thereby
comprises a hologram with controlled side lobes. A hologram with
anti-apodized .DELTA.n comprises a hologram wherein .DELTA.n is
highest at the shallowest and deepest depth within the hologram and
wherein .DELTA.n is lowest at a depth between the shallowest and
deepest depth within the hologram. In other words, .DELTA.n is
highest at the first and second surface of the hologram and
.DELTA.n is lowest at a depth between the first and second
surface.
[0089] Typically, a master hologram with a given thickness and
bandwidth is used in combination with a recording substrate with a
given thickness and refractive index (in accordance with the
present systems, devices, and methods). The wavelength and angle of
the reference beam diffracted by the master hologram to produce the
initial set of fringes within the HRM is fixed to achieve a desired
playback wavelength and angle for the recorded hologram. The
wavelength and angle of each reference beam diffracted by the
master hologram to record each additional set of fringes is then
fixed to achieve the necessary net phase shift for each additional
set of fringes, such that the interference between the initial set
of fringes and each additional set of fringes within the HRM will
produce variations of .DELTA.n within the HRM that give the desired
magnitude of side lobes relative to the main peak of the hologram
with controlled side lobes.
[0090] A reference beam comprises laser light. A reference beam may
comprise a plane wave, wherein a plane wave comprises laser light
with parallel wave fronts. A plane wave does not converge to a
point and a plane wave does not diverge from a point. A plane wave
may be generated by collimating laser light, wherein collimating
laser light may include reflecting laser light with a mirror or
refracting laser light with a lens. A hologram recorded with a
plane wave will have the most parallel fringes; in other words, the
slant angle of the fringes will have minimal change throughout the
hologram. Recording a hologram with a plane wave may therefore be
advantageous since the distribution of .DELTA.n as a function of
depth within the resulting hologram will be the most consistent
across the lateral dimensions of the hologram.
[0091] A reference beam may comprise a spherical wave, wherein a
spherical wave comprises laser light with spherically curved wave
fronts; the curvature of the wave fronts includes a focal point. A
spherical wave either converges to a focal point or diverges from a
focal point. A spherical wave may be generated by focusing laser
light with a converging lens or a converging mirror; a spherical
wave may be generated by defocusing laser light with a diverging
lens or a diverging mirror. Recording a hologram with a spherical
wave may be advantageous since the recorded hologram will possess
an optical power and therefore the recorded hologram may focus (or
defocus) light in addition to any other optical functions the
recorded hologram performs. A hologram recorded with a spherical
wave will not have perfectly parallel fringes; in other words, the
slant angle of the fringes will not be exactly the same throughout
the lateral dimensions of the hologram. However, the difference in
slant angle between fringes does not affect the magnitude of the
side lobes of the hologram so long as the focal point of the
spherical wave(s) is (are) at a distance from the hologram equal to
at least 50%, at least 100%, or at least 200% of the largest
lateral dimension of the hologram with controlled side lobes.
Increasing the focal distance (relative to the size of the
hologram) decreases the difference in slant angle between fringes,
bringing the fringes of a hologram recorded with a spherical wave
closer to parallel.
[0092] Consider FIG. 3A, which shows a cross-sectional view of
hologram with unmatched fringe spacing 300a in accordance with the
present systems, devices, and methods. Hologram with unmatched
fringe spacing 300a comprises first set of fringes 310a and second
set of fringes 320a, where the spacing of first set of fringes 310a
is less than the spacing of second set of fringes 320a. Hologram
with unmatched fringe spacing 300a comprises a hologram with
anti-apodized .DELTA.n. Because the spacings of first set of
fringes 310a and second set of fringes 320a do not match, the depth
of maximum constructive interference, and therefore the depth of
maximum .DELTA.n, will vary throughout the hologram laterally.
[0093] Consider FIG. 3B, which shows a cross-sectional view of
hologram with unmatched phase 300b in accordance with the present
systems, devices, and methods. Hologram with unmatched phase 300b
comprises first set of fringes 310b and second set of fringes 320b.
The phase of first set of fringes 310b and second set of fringes
320b combine such that first set of fringes 310b and second set of
fringes 320b interfere constructively at the highest and lowest
depth of hologram with unmatched phase 300b and interfere
destructively at the middle depth of hologram with unmatched phase
300b. .DELTA.n within hologram with unmatched phase 300b is
therefore at a maximum at the highest and lowest depth of hologram
with unmatched phase 300b and at a minimum at the middle depth of
hologram with unmatched phase 300b; hologram with unmatched phase
300b is therefore anti-apodized and would show the strongest
possible side lobes. This is advantageous if strong side lobes are
desirable, however it is disadvantageous if minimal side lobes are
desirable. Therefore, the phase of the diffracted object beams must
be controlled during replication.
[0094] Returning to FIG. 1, at 105, the hologram with controlled
side lobes is dismounted from the recording substrate. Dis-mounting
the hologram with controlled side lobes from the recording
substrate includes physically de-coupling the hologram with
controlled side lobes from the recording substrate.
[0095] Method 100 may further comprise bleaching the hologram with
controlled side lobes. Bleaching includes exposing the hologram
with controlled side lobes to a bleaching agent. Non-exclusive
examples of a bleaching agents include acids, peroxides,
hypochlorites, and light. Photobleaching includes exposing the
hologram with controlled side lobes 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 within the hologram with controlled side lobes.
[0096] Photobleaching the hologram with controlled side lobes
converts at least a portion of the hologram with controlled side
lobes from a photopolymerizable material to a material that is not
photopolymerizable.
[0097] Method 100 may further comprise recording a master hologram.
Recording a master hologram may include illuminating a master HRM
with an object beam and a reference beam.
[0098] FIG. 4 is a cross-sectional view of hologram with controlled
side lobes recording system 400 in accordance with the present
systems, devices, and methods. Although FIG. 4 is a cross-sectional
view, a dot-fill pattern has been used to differentiate various
elements in FIG. 4 rather than a cross-hatch pattern to avoid
confusion between the diagonal lines denoting fringes and diagonal
lines denoting cross-hatching.
[0099] Hologram with controlled side lobes recording system 400
comprises copy HRM 410, recording substrate 420, master hologram
430, laser light source 440, first reference beam 441, second
reference beam 442, first diffracted object beam 443, and second
diffracted object beam 444. Hologram with controlled side lobes
recording system 400 may be employed to produce a hologram
substantively similar to hologram with controlled side lobes 200
via method of producing a hologram with controlled side lobes
100.
[0100] Copy HRM 410 comprises first copy HRM surface 411 and second
copy HRM surface 412. Recording substrate 420 comprises master-side
surface 461 and copy HRM-side surface 462. Master hologram 430 is
physically coupled to master-side surface 461 of recording
substrate 420, while first copy HRM surface 411 of copy HRM 410 is
physically coupled to copy HRM-side surface 462 of recording
substrate 420.
[0101] Laser light source 440 produces first reference beam 441 and
second reference beam 442. First reference beam 441 may be of a
different wavelength than second reference beam 442. First
reference beam 441 may be of a different angle than second
reference beam 442. First reference beam 441 and second reference
beam 442 impinge on master hologram 430. Master hologram 430
comprises master hologram fringes 431. Master hologram fringes 431
diffract first reference beam 441 and second reference beam 442 to
produce first diffracted object beam 443 and second diffracted
object beam 444. Master hologram 430 produces first diffracted
object beam 443 from first reference beam 441 and produces second
diffracted object beam 444 from second diffracted object beam 444.
First diffracted object beam 443 and first reference beam 441
interfere to produce initial set of optical fringes 451. Second
diffracted object beam 444 and second reference beam 442 interfere
to produce additional set of optical fringes 452.
[0102] Initial set of optical fringes 451 and additional set of
optical fringes 452 meta-interfere with each other within copy HRM
410. Constructive meta-interference between initial set of optical
fringes 451 and additional set of optical fringes 452 causes an
increase in .DELTA.n in the physical fringes recorded from the
optical fringes, while destructive meta-interference between
initial set of optical fringes 451 and additional set of optical
fringes 452 causes a decrease in .DELTA.n in the physical fringes
recorded from the optical fringes. The depth within copy HRM 410 at
which constructive or destructive meta-interference between initial
set of optical fringes 451 and additional set of optical fringes
452 occurs depends on the phase of the initial set of optical
fringes 451 relative to the additional set of optical fringes
452.
[0103] First reference beam 441 will have a given phase at copy
HRM-side surface 462. First diffracted object beam 443 will have a
phase at copy HRM-side surface 462 that depends on the phase of
first reference beam 441 at copy HRM-side surface 462 and the
effective distance travelled by the light comprising first
diffracted object beam 443. The effective distance travelled by the
light comprising first diffracted object beam 443 depends on the
thickness and refractive index of recording substrate 420. The
difference in phase between first reference beam 441 and first
diffracted object beam 443 at HRM-side surface 462 is the phase
shift of first diffracted object beam 443.
[0104] Second reference beam 442 will have a given phase at copy
HRM-side surface 462. Second diffracted object beam 444 will have a
phase at copy HRM-side surface 462 that depends on the phase of
second reference beam 442 at copy HRM-side surface 462 and the
effective distance travelled by the light comprising second
diffracted object beam 444. The effective distance travelled by the
light comprising second diffracted object beam 444 depends on the
thickness and refractive index of recording substrate 420. The
difference in phase between second reference beam 442 and second
diffracted object beam 444 at HRM-side surface 462 is the phase
shift of second diffracted object beam 444.
[0105] The difference between the phase shift of second diffracted
object beam 444 and the phase shift of first diffracted object beam
443 is the net phase shift of second diffracted object beam 444.
The phase of initial set of optical fringes 451 depends on the
phase shift of first diffracted object beam 443. The phase of
additional set of optical fringes 452 depends on the phase shift of
second diffracted object beam 444. The difference in phase between
additional set of optical fringes 452 and initial set of optical
fringes 451 is the net phase shift of additional set of optical
fringes 452. The net phase shift of additional set of optical
fringes 452 depends on the net phase shift of second diffracted
object beam 444.
[0106] The net phase shift of additional set of optical fringes 452
determines the location of constructive and destructive
interference of initial set of optical fringes 451 and additional
set of optical fringes 452. The net phase shift of additional set
of optical fringes 452 may be measured in radians at a depth within
copy HRM 410 equidistant between first copy HRM surface 411 and
second copy HRM surface 412. If the net phase shift of additional
set of optical fringes 452 is 0, then meta-interference between
initial set of optical fringes 451 and additional set of optical
fringes 452 will be most constructive at a depth within copy HRM
410 equidistant between first copy HRM surface 411 and second copy
HRM surface 412 and most destructive at depths closest to first
copy HRM surface 411 and second copy HRM surface. If the net phase
shift of additional set of optical fringes 452 is .pi., then
meta-interference between initial set of optical fringes 451 and
additional set of optical fringes 452 will be most destructive at a
depth within copy HRM 410 equidistant between first copy HRM
surface 411 and second copy HRM surface 412 and most constructive
at depths closest to first copy HRM surface 411 and second copy HRM
surface.
[0107] If first reference beam 441 and the second reference beam
442 comprise light of differing angles with the same wavelength,
first reference beam 441 and second reference beam 442 will travel
different paths to reach master hologram 430, and first diffracted
object beam 443 and second diffracted object beam 444 will travel
different paths to reach copy HRM 410. The effective distance
travelled by first diffracted object beam 443 and second diffracted
object beam 444 will be different. The effective distance travelled
by first diffracted object beam 443 is equivalent to a first number
of wavelengths of first diffracted object beam 443. The effective
distance travelled by second diffracted object beam 444 is
equivalent to a second number of wavelengths of second diffracted
object beam 444. Due to the different effective distances
travelled, the first number of wavelengths of first diffracted
object beam 443 is not equal to the second number of wavelengths of
second diffracted object beam 444, and the difference between the
first number of wavelengths of first diffracted object beam 443 and
the second number of wavelengths of second diffracted object beam
444 is the net phase shift of second diffracted object beam 444.
The difference between the first number of wavelengths of first
diffracted object beam 443 and the second number of wavelengths of
second diffracted object beam 444 depends on the thickness and the
refractive index of recording substrate 420 since the difference in
effective distance travelled depends on the thickness of recording
substrate 420. Therefore, the net phase shift of second diffracted
object beam 444 will be determined by the thickness and refractive
index of recording substrate 420.
[0108] If first reference beam 441 and the second reference beam
442 comprise light of differing wavelengths with the same angle,
the net phase shift of second diffracted object beam 444 will be
determined by the thickness and refractive index of recording
substrate 420. First reference beam 441 and second reference beam
442 will travel identical paths to reach master hologram 430, and
first diffracted object beam 443 and second diffracted object beam
444 will travel identical paths to reach copy HRM 410. The
effective distance travelled by first diffracted object beam 443
and second diffracted object beam 444 will be identical. The
effective distance travelled by first diffracted object beam 443 is
equivalent to a first number of wavelengths of first diffracted
object beam 443. The effective distance travelled by second
diffracted object beam 444 is equivalent to a second number of
wavelengths of second diffracted object beam 444. The first number
of wavelengths of first diffracted object beam 443 is not equal to
the second number of wavelengths of second diffracted object beam
444, and the difference between the first number of wavelengths of
first diffracted object beam 443 and the second number of
wavelengths of second diffracted object beam 444 is the net phase
shift of second diffracted object beam 444; the difference between
the first number of wavelengths of first diffracted object beam 443
and the second number of wavelengths of second diffracted object
beam 444 depends on the thickness and the refractive index of
recording substrate 420.
[0109] For a desired location of maximum constructive interference,
a thickness of recording substrate 420 may be calculated for the
specific wavelengths of the first sub-beam of laser light and the
second sub-beam of laser light at a given angle. In this manner,
the phase of the light comprising initial set of optical fringes
451 and additional set of optical fringes 452 may be controlled; by
extension the interference between initial set of optical fringes
451 and additional set of optical fringes 452 and thereby the
location of maximum and minimum .DELTA.n may be controlled.
[0110] In a preferred embodiment, hologram with controlled side
lobes recording system 400 comprising a first reference beam with
an angle of 50 degrees and a wavelength of 455.0 nm, a second
reference beam with an angle of 50 degrees and a wavelength of
454.3 nm, a master hologram with a playback angle of 0 degrees and
a thickness of 20 micrometers, a recording substrate with a
thickness of 57 um, and a copy HRM thickness of 8 um will produce a
copy HRM with the greatest magnitude of .DELTA.n at a depth
equidistant from first copy HRM surface 411 and second copy HRM
surface 412, the least magnitude of .DELTA.n at first copy HRM
surface 411 and second copy HRM surface 412, and side lobes with
the least magnitude.
[0111] In an alternative embodiment, the parameters of the
preferred embodiment are used with one modification chosen from a
group consisting of: increasing the wavelength of the first
reference beam by up to 0.1 nm, decreasing the wavelength of the
first reference beam by up to 0.1 nm, increasing the wavelength of
the second reference beam by up to 0.1 nm, decreasing the
wavelength of the second reference beam by up to 0.1 nm, increasing
the angle of the first reference beam and the second reference beam
each by up to 8 degrees, decreasing the angle of the first
reference beam and the second reference beam each by up to 8
degrees, increasing the master hologram playback angle by up to 8
degrees, decreasing the master hologram playback angle by up to 8
degrees, increasing the master thickness by up to 30 um, decreasing
the master thickness by up to 5 um, increasing the recording
substrate thickness by up to 9 um, decreasing the recording
substrate thickness by up to 9 um, increasing the copy HRM
thickness my 1 um, and decreasing the copy HRM thickness by 1 um.
The alternative embodiment will produce a copy HRM with a magnitude
of .DELTA.n at first copy HRM surface 411 and second copy HRM
surface 412 less than or equal to 50% of the highest magnitude of
.DELTA.n within the copy HRM. A person of skill in the art of
holography will appreciate that if more than one of the
modifications disclosed in the alternative embodiment are applied
to the preferred embodiment, and the magnitude of each modification
is greater than the magnitude of the modifications disclosed in the
alternative embodiment, then a copy HRM with a magnitude of
.DELTA.n at first copy HRM surface 411 and second copy HRM surface
412 less than or equal to 50% of the highest magnitude of .DELTA.n
within the copy HRM may be produced; the effect of each
modification may at least partially counteract the effect of each
other modification.
[0112] Substantively similar control of the location of maximum and
minimum .DELTA.n may be achieved via control of the angles of the
first sub-beam of laser light and the second sub-beam of laser
light. Substantively similar control of the location of maximum and
minimum .DELTA.n may be achieved via control of the thickness of
master hologram 430. Each fringe in the master hologram diffracts
the incoming laser light, at an angle such that the diffracted
light interferes at least partially constructively. If the
diffracted light is at an angle that results in interference that
is not completely constructive, then the interference is also
partially destructive. The partially destructive interference
decreases the amplitude of the diffracted laser light and
simultaneously shifts the phase of the diffracted laser light. The
magnitude of the decrease in amplitude and shift in phase is
proportional to the number of fringes that contribute to the
partially destructive interference, which is in turn dependent on
the thickness of the master hologram.
[0113] FIG. 4 depicts hologram with controlled side lobes recording
system 400 set up to replicate a reflection hologram since laser
light source 440 is located on the same side as copy HRM 410. A
person of skill in the art will appreciate that hologram with
controlled side lobes recording system 400 may also be used to
replicate a transmission hologram by moving laser light source 440
to the same side as master hologram 430.
[0114] A person of skill in the art of holography will appreciate
that while two reference beams are produced by laser light 440 in
FIG. 4, laser light source 440 may alternatively produce 3, 4, or
more reference beams. Each additional reference beam (in other
words, each reference beam beyond the second) will have a
wavelength and an angle, will pass through the master hologram, the
recording substrate, and the copy HRM, and produce a respective
additional diffracted object beam that passes through the recording
substrate and the copy HRM. Each additional diffracted object beam
will possess a net phase shift and interfere with each respective
additional reference beam to produce a respective additional set of
optical fringes. Each additional set of optical fringes will
possess a respective net phase shift (determined by the wavelength
and angle of the respective reference beam, the thickness and
playback angle of the master hologram, and the thickness of the
recording substrate) and will meta-interfere with each other set of
optical fringes to record a hologram with .DELTA.n varying as a
function of depth. The presence of additional sets of
meta-interfering optical fringes allows more complex .DELTA.n
profiles as a function of depth, allowing greater control of the
side lobes of the holograms recorded with hologram with controlled
side lobes recording system 400.
[0115] FIG. 5 is a cross-sectional view of an exemplary eyeglass
lens 500 with an embedded hologram with controlled side lobes 510
suitable for use as a transparent combiner in a WHUD in accordance
with the present systems, devices, and methods. Eyeglass lens 500
with an embedded HOE 510 comprises hologram with controlled side
lobes 510 and lens assembly 520. Hologram with controlled side
lobes 510 may be substantively similar to hologram with controlled
side lobes 200. Hologram with controlled side lobes 510 is embedded
within an internal volume of lens assembly 520. Hologram with
controlled side lobes 510 may be physically coupled to lens
assembly 520 with a low-temperature optically clear adhesive
(LT-OCA).
[0116] Hologram with controlled side lobes 510 comprises initial
set of fringes 511, additional set of fringes 512, first hologram
surface 513, and second hologram surface 514. First hologram
surface 513 is opposite second hologram surface 514. First hologram
surface 513 and second hologram surface 514 each comprise a
two-dimensional surface; first hologram surface 513 and second
hologram surface 514 may comprise parallel surfaces. The distance
between first hologram surface 513 and second hologram surface 514
is the thickness of hologram with controlled side lobes 510.
Hologram with controlled side lobes 510 may be less than ten
micrometers thick, less than 100 micrometers thick, or less than
one millimeter thick.
[0117] Initial set of fringes 511 and additional set of fringes 512
are contained within an internal volume of hologram with controlled
side lobes 510. Initial set of fringes 511 possesses initial fringe
spacing 531 and initial fringe slant angle 541. Initial fringe
spacing 531 comprises the distance between one fringe comprising
initial set of fringes 511 and an immediately adjacent fringe
comprising initial set of fringes 511. Initial fringe spacing 531
may be measured parallel to first hologram surface 513 and/or
second hologram surface 514. Initial fringe slant angle 541
comprises the angle between the fringes comprising initial set of
fringes 511 and a line normal to at least one of: first hologram
surface 513 and second hologram surface 514.
[0118] Additional set of fringes 512 comprises additional fringe
spacing 532, additional fringe slant angle 542, and net phase shift
550. Net phase shift 550 comprises the difference in phase between
initial set of fringes 511 and additional set of fringes 512 at a
depth equidistant between first hologram surface 513 and second
hologram surface 514. Additional fringe spacing 532 comprises the
distance between one fringe comprising additional set of fringes
512 and an immediately adjacent fringe comprising additional set of
fringes 512. Additional fringe spacing 532 may be measured parallel
to first surface 513 and/or second surface 514. Additional fringe
spacing 532 is equal to initial fringe spacing 531. Additional
fringe slant angle 542 comprises the angle between the fringes
comprising additional set of fringes 512 and a line normal to at
least one of: first hologram surface 513 and second hologram
surface 514. Additional fringe slant angle 542 is not equal to
initial fringe slant angle 541.
[0119] Initial set of fringes 511 and additional set of fringes 512
exhibit meta-interference. Portions of hologram with controlled
side lobes 510 that exhibit constructive meta-interference between
initial set of fringes 511 and additional set of fringes 512
possess higher .DELTA.n. Portions of hologram with controlled side
lobes 510 that exhibit destructive meta-interference between
initial set of fringes 511 and additional set of fringes 512
possess lower .DELTA.n. If .DELTA.n is least at depths closest to
first surface 513 and/or second surface 514, and if .DELTA.n is
greatest at a depth equidistant from first hologram surface 513 and
second hologram surface 514, then hologram with controlled side
lobes 510 will have side lobes with the least possible magnitude.
If .DELTA.n at depths closest to first hologram surface 513 and/or
second hologram surface 514 is less than 50% of .DELTA.n at a depth
equidistant from first hologram surface 513 and second hologram
surface 514 then hologram with controlled side lobes 700 is at
least partially apodized and may exhibit side lobes with an
intensity less than 25%, less than 10%, or less than one percent of
the intensity of the primary peak.
[0120] If .DELTA.n is greatest at depths closest to first surface
513 and/or second surface 514, and if .DELTA.n is least at a depth
equidistant from first hologram surface 513 and second hologram
surface 514, then hologram with controlled side lobes 510 will have
side lobes with the greatest possible magnitude. If .DELTA.n at a
depth equidistant from first hologram surface 513 and second
hologram surface 514 is less than 50% of .DELTA.n at depths closest
to first hologram surface 513 and/or second hologram surface 514
then hologram with controlled side lobes 510 is at least partially
anti-apodized and will exhibit side lobes with an intensity at
least 25% of, at least 50% of, or greater than the intensity of the
primary peak.
[0121] If net phase shift 550 is equal to 0, then hologram with
controlled side lobes 510 will be apodized. If net phase shift 550
is equal to .pi., then hologram with controlled side lobes 510 will
be anti-apodized. A person of skill in the art of holography will
appreciate that the position of highest .DELTA.n within hologram
with controlled side lobes 510 depends on net phase shift 550, and
since the magnitude of the side lobes of hologram with controlled
side lobes 510 depends on the position of highest .DELTA.n, the
side lobes of hologram with controlled side lobes 510 may therefore
be controlled by controlling net phase shift 550. Control of net
phase shift 550 may be achieved by controlling the angle and
wavelength of the reference beams used to record initial set of
fringes 511 and additional set of fringes 512.
[0122] A person of skill in the art of holography will appreciate
that hologram with controlled side lobes 510 may comprise more than
one additional set of fringes; where each additional set of fringes
comprises a respective additional fringe spacing (equal to the
initial fringe spacing), additional slant angle, and net phase
shift. Each additional set of fringes will also exhibit
meta-interference with initial set of fringes 511; hologram with
controlled side lobes 510 would thereby possess a more complex
distribution of .DELTA.n as a function of depth and greater
possible control over the relative magnitude of the side lobes of
hologram with controlled side lobes 510.
[0123] Hologram with controlled side lobes 510 may comprise a
wavelength-multiplexed hologram, where initial set of fringes 511
comprises at least two wavelength-specific sub-sets of fringes and
additional set of fringes 512 comprises at least two
wavelength-specific sub-sets of fringes.
[0124] FIG. 6 is a partial-cutaway perspective view of a WHUD 600
that includes an eyeglass lens 630 with an embedded hologram with
controlled side lobes 631 in accordance with the present systems,
devices, and methods. Eyeglass lens 630 may be substantially
similar to eyeglass lens 500 from FIG. 5. Embedded hologram with
controlled side lobes 631 may be substantively similar to hologram
with controlled side lobes 200. WHUD 600 comprises a support
structure 610 that is worn on the head of the user and has a
general shape and appearance of an eyeglasses (e.g., sunglasses)
frame. Support structure 610 carries multiple components,
including: an image source 620, and an eyeglass lens 630. Image
source 620 is positioned and oriented to direct light towards the
eyeglass lens and may include, for example, a micro-display system,
a scanning laser projection system, or another system for
generating display images. FIG. 6 provides a partial-cutaway view
in which regions of support structure 610 have been removed in
order to render visible portions of image source 620 and clarify
the location of image source 620 within WHUD 600. Eyeglass lens 630
is positioned within a field of view of an eye of the user when the
support structure is worn on the head of the user and serves as
both a conventional eyeglass lens (i.e., prescription or
non-prescription depending on the needs of the user) and a
transparent combiner.
[0125] Eyeglass lens 630 with an embedded hologram with controlled
side lobes 631 comprises hologram with controlled side lobes 631
and lens assembly 632. Hologram with controlled side lobes 631 is
embedded within an internal volume of lens assembly 632. Hologram
with controlled side lobes 631 may be physically coupled to lens
assembly 632 with a low-temperature optically clear adhesive
(LT-OCA).
[0126] Hologram with controlled side lobes 631 comprises initial
set of fringes 633, additional set of fringes 634, first hologram
surface 635, and second hologram surface 636. First hologram
surface 635 is opposite second hologram surface 636. First hologram
surface 635 and second hologram surface 636 each comprise a
two-dimensional surface; first hologram surface 635 and second
hologram surface 636 may comprise parallel surfaces. The distance
between first hologram surface 635 and second hologram surface 636
is the thickness of hologram with controlled side lobes 631.
Hologram with controlled side lobes 631 may be less than ten
micrometers thick, less than 100 micrometers thick, or less than
one millimeter thick.
[0127] Initial set of fringes 633 and additional set of fringes 634
are contained within an internal volume of hologram with controlled
side lobes 631. Initial set of fringes 633 possesses initial fringe
spacing 641 and initial fringe slant angle 643. Initial fringe
spacing 641 comprises the distance between one fringe comprising
initial set of fringes 633 and an immediately adjacent fringe
comprising initial set of fringes 633. Initial fringe spacing 641
may be measured parallel to first hologram surface 635 and/or
second hologram surface 636. Initial fringe slant angle 643
comprises the angle between the fringes comprising initial set of
fringes 633 and a line normal to at least one of: first hologram
surface 635 and second hologram surface 636.
[0128] Additional set of fringes 634 comprises additional fringe
spacing 642, additional fringe slant angle 644, and net phase shift
645. Net phase shift 645 comprises the difference in phase between
initial set of fringes 633 and additional set of fringes 634 at a
depth equidistant between first hologram surface 635 and second
hologram surface 636. Additional fringe spacing 642 comprises the
distance between one fringe comprising additional set of fringes
634 and an immediately adjacent fringe comprising additional set of
fringes 634. Additional fringe spacing 642 may be measured parallel
to first surface 635 and/or second surface 636. Additional fringe
spacing 642 is equal to initial fringe spacing 641. Additional
fringe slant angle 644 comprises the angle between the fringes
comprising additional set of fringes 634 and a line normal to at
least one of: first hologram surface 635 and second hologram
surface 636. Additional fringe slant angle 644 is not equal to
initial fringe slant angle 643.
[0129] Initial set of fringes 633 and additional set of fringes 634
exhibit meta-interference. Portions of hologram with controlled
side lobes 631 that exhibit constructive meta-interference between
initial set of fringes 633 and additional set of fringes 634
possess higher .DELTA.n. Portions of hologram with controlled side
lobes 631 that exhibit destructive meta-interference between
initial set of fringes 633 and additional set of fringes 634
possess lower .DELTA.n. If .DELTA.n is least at depths closest to
first surface 635 and/or second surface 636, and if .DELTA.n is
greatest at a depth equidistant from first hologram surface 635 and
second hologram surface 636, then hologram with controlled side
lobes 631 will have side lobes with the least possible magnitude.
If .DELTA.n at depths closest to first hologram surface 635 and/or
second hologram surface 636 is less than 50% of .DELTA.n at a depth
equidistant from first hologram surface 635 and second hologram
surface 636 then hologram with controlled side lobes 631 is at
least partially apodized and may exhibit side lobes with an
intensity less than 25%, less than 10%, or less than one percent of
the intensity of the primary peak.
[0130] If .DELTA.n is greatest at depths closest to first surface
635 and/or second surface 636, and if .DELTA.n is least at a depth
equidistant from first hologram surface 635 and second hologram
surface 636, then hologram with controlled side lobes 631 will have
side lobes with the greatest possible magnitude. If .DELTA.n at a
depth equidistant from first hologram surface 635 and second
hologram surface 636 is less than 50% of .DELTA.n at depths closest
to first hologram surface 635 and/or second hologram surface 636
then hologram with controlled side lobes 631 is at least partially
anti-apodized and will exhibit side lobes with an intensity at
least 25% of, at least 50% of, or greater than the intensity of the
primary peak.
[0131] If net phase shift 645 is equal to 0, then hologram with
controlled side lobes 631 will be apodized. If net phase shift 645
is equal to .pi., then hologram with controlled side lobes 631 will
be anti-apodized. A person of skill in the art of holography will
appreciate that the position of highest .DELTA.n within hologram
with controlled side lobes 631 depends on net phase shift 645, and
since the magnitude of the side lobes of hologram with controlled
side lobes 631 depends on the position of highest .DELTA.n, the
side lobes of hologram with controlled side lobes 631 may therefore
be controlled by controlling net phase shift 645. Control of net
phase shift 645 may be achieved by controlling the angle and
wavelength of the reference beams used to record initial set of
fringes 633 and additional set of fringes 634.
[0132] A person of skill in the art of holography will appreciate
that hologram with controlled side lobes 631 may comprise more than
one additional set of fringes; where each additional set of fringes
comprises a respective additional fringe spacing (equal to the
initial fringe spacing), additional slant angle, and net phase
shift. Each additional set of fringes will also exhibit
meta-interference with initial set of fringes 633; hologram with
controlled side lobes 631 would thereby possess a more complex
distribution of .DELTA.n as a function of depth and greater
possible control over the relative magnitude of the side lobes of
hologram with controlled side lobes 631.
[0133] Hologram with controlled side lobes 631 may comprise a
wavelength-multiplexed hologram, where initial set of fringes 633
comprises at least two wavelength-specific sub-sets of fringes and
additional set of fringes 634 comprises at least two
wavelength-specific sub-sets of fringes.
[0134] FIG. 7 is a cross-sectional view of hologram with controlled
side lobes 700 in accordance with the present systems, devices, and
methods. Hologram with controlled side lobes 700 is substantively
similar to hologram with controlled side lobes 200. Hologram with
controlled side lobes 700 may be produced by method 100. Hologram
with controlled side lobes 700 comprises initial set of fringes
710, additional set of fringes 720, first surface 731, and second
surface 732.
[0135] First surface 731 is opposite second surface 732. First
surface 731 and second surface 732 each comprise a two-dimensional
surface. Hologram with controlled side lobes 700 occupies the
volume between first surface 731 and second surface 732. First
surface 731 and second surface 732 are separated by thickness 733
wherein thickness 733 comprises the shortest distance between first
surface 731 and second surface 732 at a given point on or within
hologram with controlled side lobes 700. Thickness 733 may be less
than ten micrometers, less than one hundred micrometers, or less
than one millimeter.
[0136] First surface 731 may comprise a curved surface; first
surface 731 may be curved spherically or cylindrically around a
focal point or focal line, respectively. Second surface 732 may
comprise a curved surface; second surface 732 may be curved
spherically or cylindrically around a focal point or focal line,
respectively. First surface 731 and second surface 732 may comprise
parallel surfaces.
[0137] Initial set of fringes 710 is located within an internal
volume of hologram with controlled side lobes 700. For the sake of
clarity, initial set of fringes 710 has been depicted as a series
of lines, where the lines denote the spacing between fringes. A
person of skill in the art of holography will appreciate that
fringes may comprise local maxima (or minima) of either absorbance
or refractive index, and these maxima (or minima) may not show
sharp boundaries between regions of high (or low) absorbance or
refractive index; however, the maxima (or minima) of either
absorbance or refractive index demonstrate directionality and
periodicity and may be reasonably depicted and interpreted as a
repeating pattern of discrete lines.
[0138] Initial set of fringes 710 comprises initial fringe phase
741, initial fringe spacing 751, and initial fringe slant angle
761. Initial fringe phase 741 is depicted as being measured from
the lateral edge of hologram with controlled side lobes 700 to a
particular fringe of initial set of fringes 710 at a depth
equidistant between first surface 731 and second surface 732,
however a person of skill in the art of holography will appreciate
that, due to the periodic nature of the fringes comprising initial
set of fringes 710, initial fringe phase 741 could be measured from
any fixed point in or on hologram with controlled side lobes 700 to
any fringe of initial set of fringes 710.
[0139] Initial fringe spacing 751 comprises the distance between
one fringe comprising initial set of fringes 710 and an immediately
adjacent fringe comprising initial set of fringes 710. Initial
fringe spacing 751 may be measured parallel to first surface 731
and/or second surface 732. Initial fringe spacing 751 at least
partially determines the wavelength or range of wavelengths of
incident light that may be diffracted by initial set of fringes
710; in other words, initial fringe spacing 751 at least partially
determines the wavelength(s) of light that may be used as an object
beam to play back the hologram which initial set of fringes 710
comprises.
[0140] Initial fringe slant angle 761 comprises the angle between
the fringes comprising initial set of fringes 710 and a line normal
to at least one of: first surface 731 and second surface 732. In
other words, if the fringes comprising initial set of fringes 710
are parallel to first surface 731 then the fringes comprising
initial set of fringes 710 would have a slant angle of 90 degrees.
If the laser light used to record initial set of fringes 710
consists of plane waves then initial fringe slant angle 761 will be
constant throughout hologram with controlled side lobes 700. If the
laser light used to record initial set of fringes 710 comprises
spherical waves then initial fringe slant angle 761 will vary
throughout hologram with controlled side lobes 700; however, the
variation in slant angle caused by spherical waves is negligible
with regard to controlling the distribution of .DELTA.n, and
thereby controlling the sidelobes of hologram with controlled
sidelobes 700, so long as the focal point of each spherical wave is
located at a distance equal to at least 50%, at least 100%, or at
least 200% of the largest lateral dimension of hologram with
controlled side lobes 700.
[0141] Additional set of fringes 720 is located within an internal
volume of hologram with controlled side lobes 700. For the sake of
clarity, additional set of fringes 720 has been depicted as a
series of lines, where the lines denote the angle, phase, and the
spacing between fringes. Additional set of fringes 720 comprises
net phase shift 742, additional fringe spacing 752, and additional
fringe slant angle 762. Net phase shift 742 comprises the
difference in phase between initial set of fringes 710 and
additional set of fringes 720 at a depth equidistant between first
surface 731 and second surface 732. Net phase shift 742 is depicted
as being measured between a particular fringe of additional set of
fringes 720 and a particular fringe of initial set of fringes 710,
however a person of skill in the art of holography will appreciate
that, due to the periodic nature of the fringes comprising
additional set of fringes 720, net phase shift 742 could be
measured from any fringe of initial set of fringes 710 to any
fringe of additional set of fringes 720. Additional fringe spacing
752 comprises the distance between one fringe comprising additional
set of fringes 720 and an immediately adjacent fringe comprising
additional set of fringes 720.
[0142] Additional fringe spacing 752 may be measured parallel to
first surface 731 and/or second surface 732. Additional fringe
spacing 752 at least partially determines the wavelength or range
of wavelengths of incident light that may be diffracted by
additional set of fringes 720; in other words, additional fringe
spacing 752 at least partially determines the wavelength(s) of
light that may be used as an object beam to play back the hologram
which additional set of fringes 720 comprises. Additional fringe
spacing 752 is equal to initial fringe spacing 751.
[0143] Additional fringe slant angle 762 comprises the angle
between the fringes comprising additional set of fringes 720 and a
line normal to at least one of: first surface 731 and second
surface 732. If the laser light used to record additional set of
fringes 720 consists of plane waves then additional fringe slant
angle 762 will be constant throughout hologram with controlled side
lobes 700. If the laser light used to record additional set of
fringes 720 comprises spherical waves then additional fringe slant
angle 762 will vary throughout hologram with controlled side lobes
700; however, the variation in slant angle caused by spherical
waves is negligible with regard to controlling the distribution of
.DELTA.n, and thereby controlling the sidelobes of hologram with
controlled sidelobes 700, so long as the focal point of each
spherical wave is located at a distance equal to at least 50%, at
least 100%, or at least 200% of the largest lateral dimension of
hologram with controlled side lobes 700. Additional fringe slant
angle 762 is not equal to initial fringe slant angle 761.
[0144] Initial set of fringes 710 and additional set of fringes 720
exhibit meta-interference. Portions of hologram with controlled
side lobes 700 that exhibit constructive meta-interference between
initial set of fringes 710 and additional set of fringes 720
possess higher .DELTA.n. Portions of hologram with controlled side
lobes 700 that exhibit destructive meta-interference between
initial set of fringes 710 and additional set of fringes 720
possess lower .DELTA.n. If .DELTA.n is least at depths closest to
first surface 731 and/or second surface 732, and if .DELTA.n is
greatest at a depth equidistant from first surface 731 and second
surface 732, then hologram with controlled side lobes 700 will have
side lobes with the least possible magnitude; in other words
hologram with controlled side lobes 700 is apodized. If .DELTA.n at
depths closest to first surface 731 and/or second surface 732 is
less than 50% of .DELTA.n at a depth equidistant from first surface
731 and second surface 732 then hologram with controlled side lobes
700 is at least partially apodized and may exhibit side lobes with
an intensity less than 25%, less than 10%, or less than one percent
of the intensity of the primary peak.
[0145] If .DELTA.n is greatest at depths closest to first surface
731 and/or second surface 732, and if .DELTA.n is least at a depth
equidistant from first surface 731 and second surface 732, then
hologram with controlled side lobes 700 will have side lobes with
the greatest possible magnitude; in other words, hologram with
controlled side lobes 700 is anti-apodized. Higher .DELTA.n at
first surface 731 and second surface 732 increases the magnitude of
the side lobes, while higher .DELTA.n at a point equidistant
between first surface 731 and second surface 732 increases the
magnitude of the primary peak. If .DELTA.n at a depth equidistant
from first surface 731 and second surface 732 is less than 50% of
.DELTA.n at depths closest to first surface 731 and/or second
surface 732 then hologram with controlled side lobes 700 is at
least partially anti-apodized and will exhibit side lobes with an
intensity at least 25% of, at least 50% of, or greater than the
intensity of the primary peak.
[0146] Net phase shift 742 may be expressed in units of radians,
where a phase shift of 2.pi. is equal to a phase shift of 0. If net
phase shift 742 is equal to 0, then hologram with controlled side
lobes 700 will be apodized. If net phase shift 742 is equal to
.pi., then hologram with controlled side lobes 700 will be
anti-apodized. A person of skill in the art of holography will
appreciate that the position of highest .DELTA.n within hologram
with controlled side lobes 700 depends on net phase shift 742, and
since the magnitude of the side lobes of hologram with controlled
side lobes 700 depends on the position of highest .DELTA.n, the
side lobes of hologram with controlled side lobes 700 may therefore
be controlled by controlling net phase shift 742. Control of net
phase shift 742 may be achieved by controlling the angle and
wavelength of the reference beams used to record initial set of
fringes 710 and additional set of fringes 720.
[0147] Any increase in .DELTA.n as a function of depth within
hologram with controlled side lobes 700 will be a continuous
increase if only two sets of fringes are present in hologram with
controlled side lobes 700. Any decrease in .DELTA.n as a function
of depth within hologram with controlled side lobes 700 will be a
continuous decrease if only two sets of fringes are present in
hologram with controlled side lobes 700. More complex variation in
.DELTA.n as a function of depth within hologram with controlled
side lobes 700 requires more than two sets of fringes within
hologram with controlled side lobes 700.
[0148] A person of skill in the art of holography will appreciate
that hologram with controlled side lobes 700 may comprise more than
one additional set of fringes; where each additional set of fringes
comprises a respective additional fringe spacing (equal to the
initial fringe spacing), additional slant angle, and net phase
shift. Each additional set of fringes will also exhibit
meta-interference with initial set of fringes 710; hologram with
controlled side lobes 700 would thereby possess a more complex
distribution of .DELTA.n as a function of depth and greater
possible control over the relative magnitude of the side lobes of
hologram with controlled side lobes 700.
[0149] Hologram with controlled side lobes 700 may comprise a
wavelength-multiplexed hologram, where initial set of fringes 710
comprises at least two wavelength-specific sub-sets of fringes and
additional set of fringes 720 comprises at least two
wavelength-specific sub-sets of fringes. A wavelength-specific
sub-set of fringes diffracts laser light with a range of
wavelengths that is at least partially different from the range of
wavelengths diffracted by each other wavelength-specific sub-set of
fringes. Hologram with controlled side lobes 700 may comprise a red
hologram, a green hologram, a blue hologram, and an infrared
hologram, where each color of hologram corresponds to a respective
initial wavelength-specific sub-set of initial and additional
fringes.
[0150] The intensity of the side lobes of a hologram may be
measured relative to the intensity of the primary peak of the
hologram. Relative to the primary peak of the hologram, the
intensity of the side lobes of the blue hologram, the green
hologram, the red hologram, and the infrared hologram may be equal.
Due to the large difference in wavelength between each color
hologram, careful selection of wavelength and angle is required for
each reference beam employed in the production of hologram with
controlled side lobes 700 to ensure that each color hologram has
the same net phase shift when recorded on a recording substrate
with a constant thickness.
[0151] FIG. 8 is a cross-sectional view of an exemplary eyeglass
lens 800 with comprising a light guide and a hologram with
controlled side lobes in accordance with the present systems,
devices, and methods. Eyeglass lens 800 comprises light guide 810,
in-coupler 811, out-coupler 812, cladding layer 818 and lens layer
819.
[0152] Cladding layer 818 surrounds light guide 810, in-coupler
811, and GRIN-outcoupler 812. Cladding layer 818 comprises a low
index material, where cladding layer may comprise a material with a
refractive index of 1.5, 1.2, or 1.0. A lower refractive index is
more advantageous as this increases the field of view of the light
guide when the light guide is used as a display. A non-exclusive
example of a cladding material with a refractive index of 1.5 is a
plastic material (PET, acrylic, Nylon, etc.). A non-exclusive
example of a cladding material with a refractive index of 1.2 is a
layer of silica sol-gel. A non-exclusive example of a cladding
material with a refractive index of 1.0 is air, where a cladding
layer comprising air typically includes additional material to
provide structural support to the light guide.
[0153] In-coupler 811 comprises first surface 813 and third surface
815. In-coupler 811 is physically coupled to light guide 810 at
first surface 813; in-coupler 811 is positioned and oriented to
redirect light into light guide 810. Out-coupler 812 comprises
second surface 814 and fourth surface 816. Out-coupler 812 is
physically coupled to light guide 810 at second surface 814;
out-coupler 812 is positioned and oriented to redirect light out of
light guide 810.
[0154] Beam of light 820 impinges on in-coupler 811 with incident
angle 823 and is redirected into light guide 810 at an angle
greater than the critical angle for light guide 810. Beam of light
820 is diffracted by incoupler 811 and is converted to guided light
821. Guided light 821 propagates through light guide 810 at an
angle greater than the critical angle, bouncing off of the opposed
surfaces of light guide 810 due to total internal reflection (TIR).
Upon reaching out-coupler 812, guided light 821 is redirected out
of light guide 810 to form redirected light 822; redirected light
822 is directed towards an eye of a user 813.
[0155] Eyeglass lens 800 may further comprise exit pupil expander
817; exit pupil expander 817 may be physically coupled to light
guide 810. Exit pupil expander 817 may replicate guided light 821
to form additional beams of light, where the additional beams of
light propagate to the outcoupler and may be redirected out of
light guide 810 towards an eye of a user 813, expanding the eyebox
of eyeglass lens 800 when eyeglass lens 800 is utilized in a
wearable heads-up display. Light guide 810 may advantageously
comprise a high index material.
[0156] Each of: in-coupler 811, out-coupler 812, and/or exit pupil
expander 817, may comprise a hologram with controlled side lobes
substantively similar to hologram with controlled side lobes 200.
Eyeglass lens 800 may be similar in some ways to eyeglass lens 500.
Eyeglass lens 800 may similar in some ways to eyeglass lens
630.
[0157] A person of skill in the art will appreciate that the
various embodiments for side lobe control in holograms described
herein may be applied in non-WHUD applications. For example, the
present systems, devices, and methods may be applied in
non-wearable heads-up displays and/or in other applications that
may or may not include a visible display.
[0158] In some implementations, one or more optical fiber(s) may be
used to guide light signals along some of the paths illustrated
herein.
[0159] The WHUDs described herein may include one or more sensor(s)
(e.g., microphone, camera, thermometer, compass, altimeter, and/or
others) for collecting data from the user's environment. For
example, one or more camera(s) may be used to provide feedback to
the processor of the WHUD and influence where on the display(s) any
given image should be displayed.
[0160] The WHUDs described herein may include one or more on-board
power sources (e.g., one or more battery(ies)), a wireless
transceiver for sending/receiving wireless communications, and/or a
tethered connector port for coupling to a computer and/or charging
the one or more on-board power source(s).
[0161] The WHUDs described herein may receive and respond to
commands from the user in one or more of a variety of ways,
including without limitation: voice commands through a microphone;
touch commands through buttons, switches, or a touch sensitive
surface; and/or gesture-based commands through gesture detection
systems as described in, for example, U.S. Non-Provisional patent
application Ser. No. 14/155,087, U.S. Non-Provisional patent
application Ser. No. 14/155,107, PCT Patent Application
PCT/US2014/057029, and/or U.S. Provisional Patent Application Ser.
No. 62/236,060, all of which are incorporated by reference herein
in their entirety.
[0162] Throughout this specification and the appended claims the
term "communicative" as in "communicative pathway," "communicative
coupling," and in variants such as "communicatively coupled," is
generally used to refer to any engineered arrangement for
transferring and/or exchanging information. Exemplary communicative
pathways include, but are not limited to, electrically conductive
pathways (e.g., electrically conductive wires, electrically
conductive traces), magnetic pathways (e.g., magnetic media),
and/or optical pathways (e.g., optical fiber), and exemplary
communicative couplings include, but are not limited to, electrical
couplings, magnetic couplings, and/or optical couplings.
[0163] 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.
[0164] 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.
[0165] For instance, the foregoing detailed description has set
forth various embodiments of the devices and/or processes via the
use of block diagrams, schematics, and examples. Insofar as such
block diagrams, schematics, and examples contain one or more
functions and/or operations, it will be understood by those skilled
in the art that each function and/or operation within such block
diagrams, flowcharts, or examples can be implemented, individually
and/or collectively, by a wide range of hardware, software,
firmware, or virtually any combination thereof. In one embodiment,
the present subject matter may be implemented via Application
Specific Integrated Circuits (ASICs). However, those skilled in the
art will recognize that the embodiments disclosed herein, in whole
or in part, can be equivalently implemented in standard integrated
circuits, as one or more computer programs executed by one or more
computers (e.g., as one or more programs running on one or more
computer systems), as one or more programs executed by on one or
more controllers (e.g., microcontrollers) as one or more programs
executed by one or more processors (e.g., microprocessors, central
processing units, graphical processing units), as firmware, or as
virtually any combination thereof, and that designing the circuitry
and/or writing the code for the software and or firmware would be
well within the skill of one of ordinary skill in the art in light
of the teachings of this disclosure.
[0166] When logic is implemented as software and stored in memory,
logic or information can be stored on any processor-readable medium
for use by or in connection with any processor-related system or
method. In the context of this disclosure, a memory is a
processor-readable medium that is an electronic, magnetic, optical,
or other physical device or means that contains or stores a
computer and/or processor program. Logic and/or the information can
be embodied in any processor-readable medium for use by or in
connection with an instruction execution system, apparatus, or
device, such as a computer-based system, processor-containing
system, or other system that can fetch the instructions from the
instruction execution system, apparatus, or device and execute the
instructions associated with logic and/or information.
[0167] In the context of this specification, a "non-transitory
processor-readable medium" can be any element that can store the
program associated with logic and/or information for use by or in
connection with the instruction execution system, apparatus, and/or
device. The processor-readable medium can be, for example, but is
not limited to, an electronic, magnetic, optical, electromagnetic,
infrared, or semiconductor system, apparatus or device. More
specific examples (a non-exhaustive list) of the computer readable
medium would include the following: a portable computer diskette
(magnetic, compact flash card, secure digital, or the like), a
random access memory (RAM), a read-only memory (ROM), an erasable
programmable read-only memory (EPROM, EEPROM, or Flash memory), a
portable compact disc read-only memory (CDROM), digital tape, and
other non-transitory media.
[0168] 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
Publication No. US 2015-0378161 A1, U.S. Non-Provisional patent
application Ser. No. 15/046,234, U.S. Non-Provisional patent
application Ser. No. 15/046,254, U.S. Non-Provisional patent
application Ser. No. 15/046,269, U.S. Provisional Patent
Application Ser. No. 62/156,736, U.S. Provisional Patent
Application Ser. No. 62/214,600, U.S. Provisional Patent
Application Ser. No. 62/167,767, U.S. Provisional Patent
Application Ser. No. 62/271,135, U.S. Provisional Patent
Application Ser. No. 62/245,792, U.S. Non-Provisional patent
application Ser. No. 14/155,087, U.S. Non-Provisional patent
application Ser. No. 14/155,107, PCT Patent Application
PCT/US2014/057029, and/or U.S. Provisional Patent Application Ser.
No. 62/236,060, 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.
62/482,062; U.S. Provisional Patent Application Ser. No.
62/534,099, U.S. Provisional Patent Application Ser. No.
62/557,551, U.S. Provisional Patent Application Ser. No.
62/557,554, U.S. Provisional Patent Application Ser. No.
62/565,677, U.S. Provisional Patent Application Ser. No.
62/631,278, and U.S. Provisional Patent Application Ser. No.
62/664,758 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.
[0169] 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.
* * * * *