U.S. patent application number 14/706596 was filed with the patent office on 2015-08-27 for inducing phase delays to vary an aggregate wavefront for augmented or virtual reality.
This patent application is currently assigned to Magic Leap, Inc.. The applicant listed for this patent is Magic Leap, Inc.. Invention is credited to Brian T. Schowengerdt, Matthew D. Watson.
Application Number | 20150241696 14/706596 |
Document ID | / |
Family ID | 53199737 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150241696 |
Kind Code |
A1 |
Schowengerdt; Brian T. ; et
al. |
August 27, 2015 |
INDUCING PHASE DELAYS TO VARY AN AGGREGATE WAVEFRONT FOR AUGMENTED
OR VIRTUAL REALITY
Abstract
Configurations are disclosed for presenting virtual reality and
augmented reality experiences to users. The system may comprise an
image-generating source to provide one or more frames of image data
in a time-sequential manner, a light modulator configured to
transmit light associated with the one or more frames of image
data, a substrate to direct image information to a user's eye,
wherein the substrate houses a plurality of reflectors, a first
reflector of the plurality of reflectors to reflect transmitted
light associated with a first frame of image data at a first angle
to the user's eye, and a second reflector to reflect transmitted
light associated with a second frame of the image data at a second
angle to the user's eye.
Inventors: |
Schowengerdt; Brian T.;
(Seattle, WA) ; Watson; Matthew D.; (Bellevue,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Magic Leap, Inc. |
Dania Beach |
FL |
US |
|
|
Assignee: |
Magic Leap, Inc.
Dania Beach
FL
|
Family ID: |
53199737 |
Appl. No.: |
14/706596 |
Filed: |
May 7, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14555585 |
Nov 27, 2014 |
|
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14706596 |
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61909774 |
Nov 27, 2013 |
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Current U.S.
Class: |
345/633 |
Current CPC
Class: |
G02B 27/017 20130101;
G06T 2213/08 20130101; G02B 27/0087 20130101; G06T 17/10 20130101;
G09G 5/10 20130101; G02F 1/17 20130101; H04N 13/363 20180501; G02B
2027/0125 20130101; G02B 5/005 20130101; G02B 5/1828 20130101; G06K
9/52 20130101; G06T 15/00 20130101; G06T 5/50 20130101; G06T 19/006
20130101; G06T 2207/30201 20130101; H04N 13/239 20180501; H04N
13/361 20180501; H04N 13/366 20180501; H04N 2013/0085 20130101;
G06T 7/73 20170101; G02B 5/20 20130101; G02F 1/29 20130101; G09G
5/003 20130101; G02B 6/34 20130101; G02B 2027/0118 20130101; G06T
5/003 20130101; G06T 2207/10021 20130101; G02B 6/40 20130101; G06T
15/10 20130101; G02B 5/1814 20130101; G02C 7/049 20130101; G06F
3/1423 20130101; G02B 6/06 20130101; G06T 13/40 20130101; G06K
9/0061 20130101; H04N 13/344 20180501; G02F 1/292 20130101; G02B
3/0037 20130101; G02B 30/24 20200101; G02F 1/1334 20130101; G06T
19/20 20130101; G02F 2001/294 20130101; G06T 7/50 20170101; H04N
5/74 20130101; G02B 27/0176 20130101; G06T 5/002 20130101; G02B
17/08 20130101; G02B 2027/0134 20130101; G02B 2027/014 20130101;
G02C 2202/16 20130101; G06F 3/013 20130101; H04N 5/21 20130101;
G02B 26/0808 20130101; G02B 27/01 20130101; G02B 2006/0098
20130101; G02B 2027/0123 20130101; G02B 2027/0163 20130101; G02B
2027/0178 20130101; G06T 19/003 20130101; G06F 3/017 20130101; H04N
13/341 20180501; G02B 3/0006 20130101; G02B 6/00 20130101; G02B
6/02042 20130101; G02B 27/0172 20130101; G02F 1/0105 20130101; G02F
1/31 20130101; G09G 5/02 20130101; H04N 13/117 20180501; G06T
15/506 20130101; G09G 5/18 20130101; H04N 13/286 20180501; H04N
13/383 20180501; G02B 27/0093 20130101; H04N 5/225 20130101; G02B
27/4205 20130101; G06F 3/011 20130101; G02B 6/32 20130101; G02C
7/104 20130101 |
International
Class: |
G02B 27/01 20060101
G02B027/01; G06T 19/00 20060101 G06T019/00 |
Claims
1. A system of displaying virtual content to a user, the system
comprising: an image-generating source to provide one or more
frames of image data; a multicore assembly comprising a plurality
of multicore fibers to project light associated with the one or
more frames of image data, a multicore fiber of the plurality of
multicore fibers emitting light in a wavefront, such that the
multicore assembly produces an aggregate wavefront of the projected
light; and a phase modulator to induce phase delays between the
multicore fibers in a manner such that the aggregate wavefront
emitted by the multicore assembly is varied, thereby varying a
focal distance at which the user perceives the one or more frames
of image data.
2. The system of claim 1, wherein an inverse Fourier transform of a
desired beam is injected into the multicore fibers, such that a
desired aggregate wavefront is produced.
3. The system of claim 1, wherein the aggregate wavefront is a
spherical wavefront.
4. The system of claim 1, wherein wavefronts generated by the
plurality of microfibers interfere with each other.
5. The system of claim 4, wherein the interference is a
constructive interference.
6. The system of claim 4, wherein the interference is a destructive
interference.
7. The system of claim 1, wherein the aggregate wavefront is a
planar wavefront.
8. The system of claim 7, wherein the planar wavefront corresponds
to an optical infinity depth plane.
9. The system of claim 3 wherein the spherical wavefront
corresponds to a depth plane closer than optical infinity.
10. The system of claim 1 implemented as a method.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of pending U.S. patent
application Ser. No. 14/555,585, filed Nov. 27, 2014, entitled
"VIRTUAL AND AUGMENTED REALITY SYSTEMS AND METHODS, which claims
priority from U.S. Provisional Application Ser. No. 61/909,774,
filed Nov. 27, 2013, entitled "VIRTUAL AND AUGMENTED REALITY
SYSTEMS AND METHODS". The contents of the aforementioned
applications are hereby expressly incorporated by reference into
the present application their entireties.
FIELD OF THE INVENTION
[0002] The present disclosure relates to virtual reality and
augmented reality imaging and visualization systems.
BACKGROUND
[0003] Modern computing and display technologies have facilitated
the development of systems for so called "virtual reality" or
"augmented reality" experiences, wherein digitally reproduced
images or portions thereof are presented to a user in a manner
wherein they seem to be, or may be perceived as, real. A virtual
reality, or "VR", scenario typically involves presentation of
digital or virtual image information without transparency to other
actual real-world visual input; an augmented reality, or "AR",
scenario typically involves presentation of digital or virtual
image information as an augmentation to visualization of the actual
world around the user. For example, referring to FIG. 1, an
augmented reality scene (4) is depicted wherein a user of an AR
technology sees a real-world park-like setting (6) featuring
people, trees, buildings in the background, and a concrete platform
(1120). In addition to these items, the user of the AR technology
also perceives that he "sees" a robot statue (1110) standing upon
the real-world platform (1120), and a cartoon-like avatar character
(2) flying by which seems to be a personification of a bumble bee,
even though these elements (2, 1110) do not exist in the real
world. As it turns out, the human visual perception system is very
complex, and producing a VR or AR technology that facilitates a
comfortable, natural-feeling, rich presentation of virtual image
elements amongst other virtual or real-world imagery elements is
challenging.
[0004] Referring to FIG. 2A, stereoscopic wearable glasses (8) type
configurations have been developed which generally feature two
displays (10, 12) that are configured to display images with
slightly different element presentation such that a
three-dimensional perspective is perceived by the human visual
system. Such configurations have been found to be uncomfortable for
many users due to a mismatch between vergence and accommodation
which must be overcome to perceive the images in three dimensions;
indeed, some users are not able to tolerate stereoscopic
configurations. FIG. 2B shows another stereoscopic wearable glasses
(14) type configuration featuring two forward-oriented cameras (16,
18) configured to capture images for an augmented reality
presentation to the user through stereoscopic displays. The
position of the cameras (16, 18) and displays generally blocks the
natural field of view of the user when the glasses (14) are mounted
on the user's head.
[0005] Referring to FIG. 2C, an augmented reality configuration
(20) is shown which features a visualization module (26) coupled to
a glasses frame (24) which also holds conventional glasses lenses
(22). The user is able to see an at least partially unobstructed
view of the real world with such a system, and has a small display
(28) with which digital imagery may be presented in an AR
configuration to one eye--for a monocular AR presentation. FIG. 2D
features a configuration wherein a visualization module (32) may be
coupled to a hat or helmet (30) and configured to present monocular
augmented digital imagery to a user through a small display (34).
FIG. 2E illustrates another similar configuration wherein a frame
(36) couple-able to a user's head in a manner similar to an
eyeglasses coupling so that a visualization module (38) may be
utilized to capture images and also present monocular augmented
digital imagery to a user through a small display (40). Such a
configuration is available, for example, from Google, Inc., of
Mountain View, Calif. under the trade name GoogleGlass.RTM.. None
of these configurations is optimally suited for presenting a rich,
binocular, three-dimensional augmented reality experience in a
manner that will be comfortable and maximally useful to the user,
in part because prior systems fail to address some of the
fundamental aspects of the human perception system, including the
photoreceptors of the retina and their interoperation with the
brain to produce the perception of visualization to the user.
[0006] Referring to FIG. 3, a simplified cross-sectional view of a
human eye is depicted featuring a cornea (42), iris (44), lens--or
"crystalline lens" (46), sclera (48), choroid layer (50), macula
(52), retina (54), and optic nerve pathway (56) to the brain. The
macula is the center of the retina, which is utilized to see
moderate detail; at the center of the macula is a portion of the
retina that is referred to as the "fovea", which is utilized for
seeing the finest details, and which contains more photoreceptors
(approximately 120 cones per visual degree) than any other portion
of the retina. The human visual system is not a passive sensor type
of system; it is configured to actively scan the environment. In a
manner somewhat akin to use of a flatbed scanner to capture an
image, or use of a finger to read Braille from a paper, the
photoreceptors of the eye fire in response to changes in
stimulation, rather than constantly responding to a constant state
of stimulation. Thus motion is required to present photoreceptor
information to the brain (as is motion of the linear scanner array
across a piece of paper in a flatbed scanner, or motion of a finger
across a word of Braille imprinted into a paper). Indeed,
experiments with substances such as cobra venom, which has been
utilized to paralyze the muscles of the eye, have shown that a
human subject will experience blindness if positioned with his eyes
open, viewing a static scene with venom-induced paralysis of the
eyes. In other words, without changes in stimulation, the
photoreceptors do not provide input to the brain and blindness is
experienced. It is believed that this is at least one reason that
the eyes of normal humans have been observed to move back and
forth, or dither, in side-to-side motion in what are called
"microsaccades".
[0007] As noted above, the fovea of the retina contains the
greatest density of photoreceptors, and while humans typically have
the perception that they have high-resolution visualization
capabilities throughout their field of view, they generally
actually have only a small high-resolution center that they are
mechanically sweeping around a lot, along with a persistent memory
of the high-resolution information recently captured with the
fovea. In a somewhat similar manner, the focal distance control
mechanism of the eye (ciliary muscles operatively coupled to the
crystalline lens in a manner wherein ciliary relaxation causes taut
ciliary connective fibers to flatten out the lens for more distant
focal lengths; ciliary contraction causes loose ciliary connective
fibers, which allow the lens to assume a more rounded geometry for
more close-in focal lengths) dithers back and forth by
approximately 1/4 to 1/2 diopter to cyclically induce a small
amount of what is called "dioptric blur" on both the close side and
far side of the targeted focal length; this is utilized by the
accommodation control circuits of the brain as cyclical negative
feedback that helps to constantly correct course and keep the
retinal image of a fixated object approximately in focus.
[0008] The visualization center of the brain also gains valuable
perception information from the motion of both eyes and components
thereof relative to each other. Vergence movements (i.e., rolling
movements of the pupils toward or away from each other to converge
the lines of sight of the eyes to fixate upon an object) of the two
eyes relative to each other are closely associated with focusing
(or "accommodation") of the lenses of the eyes. Under normal
conditions, changing the focus of the lenses of the eyes, or
accommodating the eyes, to focus upon an object at a different
distance will automatically cause a matching change in vergence to
the same distance, under a relationship known as the
"accommodation-vergence reflex." Likewise, a change in vergence
will trigger a matching change in accommodation, under normal
conditions. Working against this reflex, as do most conventional
stereoscopic AR or VR configurations, is known to produce eye
fatigue, headaches, or other forms of discomfort in users.
[0009] Movement of the head, which houses the eyes, also has a key
impact upon visualization of objects. Humans move their heads to
visualize the world around them; they often are in a fairly
constant state of repositioning and reorienting the head relative
to an object of interest. Further, most people prefer to move their
heads when their eye gaze needs to move more than about 20 degrees
off center to focus on a particular object (i.e., people do not
typically like to look at things "from the corner of the eye").
Humans also typically scan or move their heads in relation to
sounds--to improve audio signal capture and utilize the geometry of
the ears relative to the head. The human visual system gains
powerful depth cues from what is called "head motion parallax",
which is related to the relative motion of objects at different
distances as a function of head motion and eye vergence distance
(i.e., if a person moves his head from side to side and maintains
fixation on an object, items farther out from that object will move
in the same direction as the head; items in front of that object
will move opposite the head motion; these are very salient cues for
where things are spatially in the environment relative to the
person--perhaps as powerful as stereopsis). Head motion also is
utilized to look around objects, of course.
[0010] Further, head and eye motion are coordinated with something
called the "vestibulo-ocular reflex", which stabilizes image
information relative to the retina during head rotations, thus
keeping the object image information approximately centered on the
retina. In response to a head rotation, the eyes are reflexively
and proportionately rotated in the opposite direction to maintain
stable fixation on an object. As a result of this compensatory
relationship, many humans can read a book while shaking their head
back and forth (interestingly, if the book is panned back and forth
at the same speed with the head approximately stationary, the same
generally is not true--the person is not likely to be able to read
the moving book; the vestibulo-ocular reflex is one of head and eye
motion coordination, generally not developed for hand motion). This
paradigm may be important for augmented reality systems, because
head motions of the user may be associated relatively directly with
eye motions, and the system preferably will be ready to work with
this relationship.
[0011] Indeed, given these various relationships, when placing
digital content (e.g., 3-D content such as a virtual chandelier
object presented to augment a real-world view of a room; or 2-D
content such as a planar/flat virtual oil painting object presented
to augment a real-world view of a room), design choices may be made
to control behavior of the objects. For example, the 2-D oil
painting object may be head-centric, in which case the object moves
around along with the user's head (e.g., as in a GoogleGlass
approach); or the object may be world-centric, in which case it may
be presented as though it is part of the real world coordinate
system, so that the user may move his head or eyes without moving
the position of the object relative to the real world.
[0012] Thus when placing virtual content into the augmented reality
world presented with an augmented reality system, whether the
object should be presented as world centric (i.e., the virtual
object stays in position in the real world so that the user may
move his body, head, eyes around it without changing its position
relative to the real world objects surrounding it, such as a real
world wall); body, or torso, centric, in which case a virtual
element may be fixed relative to the user's torso, so that the user
can move his head or eyes without moving the object, but that is
slaved to torso movements; head centric, in which case the
displayed object (and/or display itself) may be moved along with
head movements, as described above in reference to GoogleGlass; or
eye centric, as in a "foveated display" configuration, as is
described below, wherein content is slewed around as a function of
what the eye position is.
[0013] With world-centric configurations, it may be desirable to
have inputs such as accurate head pose measurement, accurate
representation and/or measurement of real world objects and
geometries around the user, low-latency dynamic rendering in the
augmented reality display as a function of head pose, and a
generally low-latency display.
[0014] The systems and techniques described herein are configured
to work with the visual configuration of the typical human to
address these challenges.
SUMMARY
[0015] Embodiments of the present invention are directed to
devices, systems and methods for facilitating virtual reality
and/or augmented reality interaction for one or more users. In one
aspect, a system for displaying virtual content is disclosed.
[0016] In one or more embodiment, the system comprises an
image-generating source to provide one or more frames of image data
in a time-sequential manner, a light modulator configured to
transmit light associated with the one or more frames of image
data, a substrate to direct image information to a user's eye,
wherein the substrate houses a plurality of reflectors, a first
reflector of the plurality of reflectors to reflect light
associated with a first frame of image data at a first angle to the
user's eye, and a second reflector of the plurality of reflectors
to reflect light associated with a second frame of image data at a
second angle to the user's eye.
[0017] In another embodiment, a system for displaying virtual
content comprises an image-generating source to provide one or more
frames of image data in a time-sequential manner, a display
assembly to project light rays associated with the one or more
frames of image data, the display assembly comprises a first
display element corresponding to a first frame-rate and a first bit
depth, and a second display element corresponding to a second
frame-rate and a second bit depth, and a variable focus element
(VFE) configurable to vary a focus of the projected light and
transmit the light to the user's eye.
[0018] In yet another embodiment, a system for displaying virtual
content comprises an array of optical fibers to transmit light
beams associated with an image to be presented to a user, and a
lens coupled to the array of the optical fibers to deflect a
plurality of light beams output by the array of optical fibers
through a single nodal point, wherein the lens is physically
attached to the optical fibers such that a movement of the optical
fiber causes the lens to move, and wherein the single nodal point
is scanned.
[0019] In another embodiment, a virtual reality display system
comprises a plurality of optical fibers to generate light beams
associated with one or more images to be presented to a user, and a
plurality of phase modulators coupled to the plurality of optical
fibers to modulate the light beams, wherein the plurality of phase
modulators modulate the light in a manner that affects a wavefront
generated as a result of the plurality of light beams.
[0020] In one embodiment, a system for displaying virtual content
to a user comprises a light projection system to project light
associated with one or more frames of image data to a user's eyes,
the light project system configured to project light corresponding
to a plurality of pixels associated with the image data and a
processor to modulate a size of the plurality of pixels displayed
to the user.
[0021] In one embodiment, a system of displaying virtual content to
a user, comprises an image-generating source to provide one or more
frames of image data, a multicore assembly comprising a plurality
of multicore fibers to project light associated with the one or
more frames of image data, a multicore fiber of the plurality of
multicore fibers emitting light in a wavefront, such that the
multicore assembly produces an aggregate wavefront of the projected
light, and a phase modulator to induce phase delays between the
multicore fibers in a manner such that the aggregate wavefront
emitted by the multicore assembly is varied, thereby varying a
focal distance at which the user perceives the one or more frames
of image data.
[0022] In another embodiment, a system for displaying virtual
content to a user comprises an array of microprojectors to project
light beams associated with one or more frames of image data to be
presented to the user, wherein the microprojector is configurable
to be movable relative to one or more microprojectors of the array
of the microprojectors, a frame to house the array of
microprojectors, a processor operatively coupled to the one or more
microprojectors of the array of microprojectors to control one or
more light beams transmitted from the one or more projectors in a
manner such that the one or more light beams are modulated as a
function of a position of the one or more microprojectors relative
to the array of microprojectors, thereby enabling delivery of a
lightfield image to the user.
[0023] Additional and other objects, features, and advantages of
the invention are described in the detail description, figures and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 illustrates a user's view of augmented reality (AR)
through a wearable AR user device, in one illustrated
embodiment.
[0025] FIGS. 2A-2E illustrates various embodiments of wearable AR
devices.
[0026] FIG. 3 illustrates a cross-sectional view of the human eye,
in one illustrated embodiment.
[0027] FIGS. 4A-4D illustrate one or more embodiments of various
internal processing components of the wearable AR device.
[0028] FIGS. 5A-5H illustrate embodiments of transmitting focused
light to a user through a transmissive beamsplitter substrate.
[0029] FIGS. 6A and 6B illustrate embodiments of coupling a lens
element with the transmissive beamsplitter substrate of FIGS.
5A-5H.
[0030] FIGS. 7A and 7B illustrate embodiments of using one or more
waveguides to transmit light to a user.
[0031] FIGS. 8A-8Q illustrate embodiments of a diffractive optical
element (DOE).
[0032] FIGS. 9A and 9B illustrate a wavefront produced from a light
projector, according to one illustrated embodiment.
[0033] FIG. 10 illustrates an embodiment of a stacked configuration
of multiple transmissive beamsplitter substrate coupled with
optical elements, according to one illustrated embodiment.
[0034] FIGS. 11A-11C illustrate a set of beamlets projected into a
user's pupil, according to the illustrated embodiments.
[0035] FIGS. 12A and 12B illustrate configurations of an array of
microprojectors, according to the illustrated embodiments.
[0036] FIGS. 13A-13M illustrate embodiments of coupling
microprojectors with optical elements, according to the illustrated
embodiments.
[0037] FIGS. 14A-14F illustrate embodiments of spatial light
modulators coupled with optical elements, according to the
illustrated embodiments.
[0038] FIGS. 15A-15C illustrate the use of a wedge type waveguides
along with a plurality of light sources, according to the
illustrated embodiments.
[0039] FIGS. 16A-160 illustrate embodiments of coupling optical
elements to optical fibers, according to the illustrated
embodiments.
[0040] FIG. 17 illustrates a notch filter, according to one
illustrated embodiment.
[0041] FIG. 18 illustrates a spiral pattern of a fiber scanning
display, according to one illustrated embodiment.
[0042] FIGS. 19A-19N illustrate occlusion effects in presenting a
darkfield to a user, according to the illustrated embodiments.
[0043] FIGS. 20A-200 illustrate embodiments of various waveguide
assemblies, according to the illustrated embodiments.
[0044] FIGS. 21A-21N illustrate various configurations of DOEs
coupled to other optical elements, according to the illustrated
embodiments.
[0045] FIGS. 22A-22Y illustrate various configurations of freeform
optics, according to the illustrated embodiments.
DETAILED DESCRIPTION
[0046] Referring to FIGS. 4A-4D, some general componentry options
are illustrated. In the portions of the detailed description which
follow the discussion of FIGS. 4A-4D, various systems, subsystems,
and components are presented for addressing the objectives of
providing a high-quality, comfortably-perceived display system for
human VR and/or AR.
[0047] As shown in FIG. 4A, an AR system user (60) is depicted
wearing a frame (64) structure coupled to a display system (62)
positioned in front of the eyes of the user. A speaker (66) is
coupled to the frame (64) in the depicted configuration and
positioned adjacent the ear canal of the user (in one embodiment,
another speaker, not shown, is positioned adjacent the other ear
canal of the user to provide for stereo/shapeable sound control).
The display (62) is operatively coupled (68), such as by a wired
lead or wireless connectivity, to a local processing and data
module (70) which may be mounted in a variety of configurations,
such as fixedly attached to the frame (64), fixedly attached to a
helmet or hat (80) as shown in the embodiment of FIG. 4B, embedded
in headphones, removably attached to the torso (82) of the user
(60) in a backpack-style configuration as shown in the embodiment
of FIG. 4C, or removably attached to the hip (84) of the user (60)
in a belt-coupling style configuration as shown in the embodiment
of FIG. 4D.
[0048] The local processing and data module (70) may comprise a
power-efficient processor or controller, as well as digital memory,
such as flash memory, both of which may be utilized to assist in
the processing, caching, and storage of data a) captured from
sensors which may be operatively coupled to the frame (64), such as
image capture devices (such as cameras), microphones, inertial
measurement units, accelerometers, compasses, GPS units, radio
devices, and/or gyros; and/or b) acquired and/or processed using
the remote processing module (72) and/or remote data repository
(74), possibly for passage to the display (62) after such
processing or retrieval. The local processing and data module (70)
may be operatively coupled (76, 78), such as via a wired or
wireless communication links, to the remote processing module (72)
and remote data repository (74) such that these remote modules (72,
74) are operatively coupled to each other and available as
resources to the local processing and data module (70).
[0049] In one embodiment, the remote processing module (72) may
comprise one or more relatively powerful processors or controllers
configured to analyze and process data and/or image information. In
one embodiment, the remote data repository (74) may comprise a
relatively large-scale digital data storage facility, which may be
available through the internet or other networking configuration in
a "cloud" resource configuration. In one embodiment, all data is
stored and all computation is performed in the local processing and
data module, allowing fully autonomous use from any remote
modules.
[0050] Referring to FIGS. 5A through 22Y, various display
configurations are presented that are designed to present the human
eyes with photon-based radiation patterns that can be comfortably
perceived as augmentations to physical reality, with high-levels of
image quality and three-dimensional perception, as well as being
capable of presenting two-dimensional content.
[0051] Referring to FIG. 5A, in a simplified example, a
transmissive beamsplitter substrate (104) with a 45-degree
reflecting surface (102) directs incoming radiation (106), which
may be output from a lens (not shown), through the pupil (45) of
the eye (58) and to the retina (54). The field of view for such a
system is limited by the geometry of the beamsplitter (104). To
accommodate the desire to have comfortable viewing with minimal
hardware, in one embodiment, a larger field of view can be created
by aggregating the outputs/reflections of various different
reflective and/or diffractive surfaces and using, e.g., a
frame-sequential configuration wherein eye (58) is presented with a
sequence of frames at high frequency that provides the perception
of a single coherent scene. As an alternative to, or in addition
to, presenting different image data via different reflectors in a
time-sequential fashion, the reflectors may separate content by
other means, such as polarization selectivity or wavelength
selectivity. In addition to being capable of relaying
two-dimensional images, the reflectors can relay the
three-dimensional wavefronts associated with true-three-dimensional
viewing of actual physical objects.
[0052] Referring to FIG. 5B, a substrate (108) comprising a
plurality of reflectors at a plurality of angles (110) is shown,
with each reflector actively reflecting in the depicted
configuration for illustrative purposes. The reflectors may be
switchable elements to facilitate temporal selectivity. In one
embodiment, the reflective surfaces would intentionally be
sequentially activated with frame-sequential input information
(106), in which each reflective surface presents a narrow field of
view sub-image which is tiled with other narrow field of view
sub-images presented by the other reflective surfaces to form a
composite wide field of view image. For example, referring to FIGS.
5C, 5D, and 5E, surface (110), about in the middle of substrate
(108), is switched "on" to a reflecting state, such that it
reflects incoming image information (106) to present a relatively
narrow field of view sub-image in the middle of a larger field of
view, while the other potential reflective surfaces are in a
transmissive state.
[0053] Referring to FIG. 5C, incoming image information (106)
coming from the right of the narrow field of view sub-image (as
shown by the angle of incoming beams 106 relative to the substrate
108 input interface 112, and the resultant angle at which they exit
the substrate 108) is reflected toward the eye (58) from reflective
surface (110). FIG. 5D illustrates the same reflector (110) active,
with image information coming from the middle of the narrow field
of view sub-image, as shown by the angle of the input information
(106) at the input interface (112) and its angle as it exits
substrate (108). FIG. 5E illustrates the same reflector (110)
active, with image information coming from the left of the field of
view, as shown by the angle of the input information (106) at the
input interface (112) and the resultant exit angle at the surface
of the substrate (108). FIG. 5F illustrates a configuration wherein
the bottom reflector (110) is active, with image information (106)
coming in from the far right of the overall field of view. For
example, FIGS. 5C, 5D, and 5E can illustrate one frame representing
the center of a frame-sequential tiled image, and FIG. 5F can
illustrate a second frame representing the far right of that tiled
image.
[0054] In one embodiment, the light carrying the image information
(106) may strike the reflective surface (110) directly after
entering substrate (108) at input interface (112), without first
reflecting from the surfaces of substrate (108). In one embodiment,
the light carrying the image information (106) may reflect from one
or more surfaces of substrate (108) after entering at input
interface (112) and before striking the reflective surface (110);
for instance, substrate (108) may act as a planar waveguide,
propagating the light carrying image information (106) by total
internal reflection. Light may also reflect from one or more
surfaces of the substrate (108) from a partially reflective
coating, a wavelength-selective coating, an angle-selective
coating, and/or a polarization-selective coating.
[0055] In one embodiment, the angled reflectors may be constructed
using an electro-active material, such that upon application of a
voltage and/or current to a particular reflector, the refractive
index of the material comprising such reflector changes from an
index substantially matched to the rest of the substrate (108), in
which case the reflector is in a transmissive configuration, to a
reflective configuration wherein the refractive index of the
reflector mismatches the refractive index of the substrate (108)
such that a reflection effect is created. Example electro-active
material includes lithium niobate and electro-active polymers.
Suitable substantially transparent electrodes for controlling a
plurality of such reflectors may comprise materials such as indium
tin oxide, which is utilized in liquid crystal displays.
[0056] In one embodiment, the electro-active reflectors (110) may
comprise liquid crystal, embedded in a substrate (108) host medium
such as glass or plastic. In some variations, liquid crystal may be
selected that changes refractive index as a function of an applied
electric signal, so that more analog changes may be accomplished as
opposed to binary (from one transmissive state to one reflective
state). In an embodiment wherein 6 sub-images are to be presented
to the eye frame-sequential to form a large tiled image with an
overall refresh rate of 60 frames per second, it is desirable to
have an input display that can refresh at the rate of about 360 Hz,
with an electro-active reflector array that can keep up with such
frequency. In one embodiment, lithium niobate may be utilized as an
electro-active reflective material as opposed to liquid crystal;
lithium niobate is utilized in the photonics industry for
high-speed switches and fiber optic networks and has the capability
to switch refractive index in response to an applied voltage at a
very high frequency; this high frequency may be used to steer
line-sequential or pixel-sequential sub-image information,
especially if the input display is a scanned light display, such as
a fiber-scanned display or scanning mirror-based display.
[0057] In another embodiment, a variable switchable angled mirror
configuration may comprise one or more high-speed mechanically
repositionable reflective surfaces, such as a MEMS
(micro-electro-mechanical system) device. A MEMS device may include
what is known as a "digital mirror device", or "DMD", (often part
of a "digital light processing", or "DLP" system, such as those
available from Texas Instruments, Inc.). In another
electromechanical embodiment, a plurality of air-gapped (or in
vacuum) reflective surfaces could be mechanically moved in and out
of place at high frequency. In another electromechanical
embodiment, a single reflective surface may be moved up and down
and re-pitched at very high frequency.
[0058] Referring to FIG. 5G, it is notable that the switchable
variable angle reflector configurations described herein are
capable of passing not only collimated or flat wavefront
information to the retina (54) of the eye (58), but also curved
wavefront (122) image information, as shown in the illustration of
FIG. 5G. This generally is not the case with other waveguide-based
configurations, wherein total internal reflection of curved
wavefront information causes undesirable complications, and
therefore the inputs generally must be collimated. The ability to
pass curved wavefront information facilitates the ability of
configurations such as those shown in FIGS. 5B-5H to provide the
retina (54) with input perceived as focused at various distances
from the eye (58), not just optical infinity (which would be the
interpretation of collimated light absent other cues).
[0059] Referring to FIG. 5H, in another embodiment, an array of
static partially reflective surfaces (116) (i.e., always in a
reflective mode; in another embodiment, they may be electro-active,
as above) may be embedded in a substrate (114) with a
high-frequency gating layer (118) controlling outputs to the eye
(58) by only allowing transmission through an aperture (120) which
is controllably movable. In other words, everything may be
selectively blocked except for transmissions through the aperture
(120). The gating layer (118) may comprise a liquid crystal array,
a lithium niobate array, an array of MEMS shutter elements, an
array of DLP DMD elements, or an array of other MEMS devices
configured to pass or transmit with relatively high-frequency
switching and high transmissibility upon being switched to
transmission mode.
[0060] Referring to FIGS. 6A-6B, other embodiments are depicted
wherein arrayed optical elements may be combined with exit pupil
expansion configurations to assist with the comfort of the virtual
or augmented reality experience of the user. With a larger "exit
pupil" for the optics configuration, the user's eye positioning
relative to the display (which, as in FIGS. 4A-4D, may be mounted
on the user's head in an eyeglasses sort of configuration) is not
as likely to disrupt his experience--because due to the larger exit
pupil of the system, there is a larger acceptable area wherein the
user's anatomical pupil may be located to still receive the
information from the display system as desired. In other words,
with a larger exit pupil, the system is less likely to be sensitive
to slight misalignments of the display relative to the user's
anatomical pupil, and greater comfort for the user may be achieved
through less geometric constraint on his or her relationship with
the display/glasses.
[0061] As shown in FIG. 6A, the display (140) on the left feeds a
set of parallel rays into the substrate (124). In one embodiment,
the display may be a scanned fiber display scanning a narrow beam
of light back and forth at an angle as shown to project an image
through the lens or other optical element (142), which may be
utilized to collect the angularly-scanned light and convert it to a
parallel bundle of rays. The rays may be reflected from a series of
reflective surfaces (126, 128, 130, 132, 134, 136) which may be
configured to partially reflect and partially transmit incoming
light so that the light may be shared across the group of
reflective surfaces (126, 128, 130, 132, 134, 136) approximately
equally. With a small lens (138) placed at each exit point from the
waveguide (124), the exiting light rays may be steered through a
nodal point and scanned out toward the eye (58) to provide an array
of exit pupils, or the functional equivalent of one large exit
pupil that is usable by the user as he or she gazes toward the
display system.
[0062] For virtual reality configurations wherein it is desirable
to also be able to see through the waveguide to the real world
(144), a similar set of lenses (139) may be presented on the
opposite side of the waveguide (124) to compensate for the lower
set of lenses; thus creating a the equivalent of a
zero-magnification telescope. The reflective surfaces (126, 128,
130, 132, 134, 136) each may be aligned at approximately 45 degrees
as shown, or may be configured to have different alignments, akin
to the configurations of FIGS. 5B-5H, for example). The reflective
surfaces (126, 128, 130, 132, 134, 136) may comprise
wavelength-selective reflectors, band pass reflectors, half
silvered mirrors, or other reflective configurations. The lenses
(138, 139) shown are refractive lenses, but diffractive lens
elements may also be utilized.
[0063] Referring to FIG. 6B, a somewhat similar configuration is
depicted wherein a plurality of curved reflective surfaces (148,
150, 152, 154, 156, 158) may be utilized to effectively combine the
lens (element 138 of FIG. 6A) and reflector (elements 126, 128,
130, 132, 134, 136 of FIG. 6A) functionality of the embodiment of
FIG. 6A, thereby obviating the need for the two groups of lenses
(element 138 of FIG. 6A). The curved reflective surfaces (148, 150,
152, 154, 156, 158) may be various curved configurations selected
to both reflect and impart angular change, such as parabolic or
elliptical curved surfaces. With a parabolic shape, a parallel set
of incoming rays will be collected into a single output point; with
an elliptical configuration, a set of rays diverging from a single
point of origin are collected to a single output point. As with the
configuration of FIG. 6A, the curved reflective surfaces (148, 150,
152, 154, 156, 158) preferably are configured to partially reflect
and partially transmit so that the incoming light is shared across
the length of the waveguide (146). The curved reflective surfaces
(148, 150, 152, 154, 156, 158) may comprise wavelength-selective
notch reflectors, half silvered mirrors, or other reflective
configurations. In another embodiment, the curved reflective
surfaces (148, 150, 152, 154, 156, 158) may be replaced with
diffractive reflectors configured to reflect and also deflect.
[0064] Referring to FIG. 7A, perceptions of Z-axis difference
(i.e., distance straight out from the eye along the optical axis)
may be facilitated by using a waveguide in conjunction with a
variable focus optical element configuration. As shown in FIG. 7A,
image information from a display (160) may be collimated and
injected into a waveguide (164) and distributed in a large exit
pupil manner using, e.g., configurations such as those described in
reference to FIGS. 6A and 6B, or other substrate-guided optics
methods known to those skilled in the art--and then variable focus
optical element capability may be utilized to change the focus of
the wavefront of light emerging from the waveguide and provide the
eye with the perception that the light coming from the waveguide
(164) is from a particular focal distance. In other words, since
the incoming light has been collimated to avoid challenges in total
internal reflection waveguide configurations, it will exit in
collimated fashion, requiring a viewer's eye to accommodate to the
far point to bring it into focus on the retina, and naturally be
interpreted as being from optical infinity--unless some other
intervention causes the light to be refocused and perceived as from
a different viewing distance; one suitable such intervention is a
variable focus lens.
[0065] In the embodiment of FIG. 7A, collimated image information
is injected into a piece of glass (162) or other material at an
angle such that it totally internally reflects and is passed into
the adjacent waveguide (164). The waveguide (164) may be configured
akin to the waveguides of FIGS. 6A or 6B (124, 146, respectively)
so that the collimated light from the display is distributed to
exit somewhat uniformly across the distribution of reflectors or
diffractive features along the length of the waveguide. Upon exit
toward the eye (58), in the depicted configuration the exiting
light is passed through a variable focus lens element (166)
wherein, depending upon the controlled focus of the variable focus
lens element (166), the light exiting the variable focus lens
element (166) and entering the eye (58) will have various levels of
focus (a collimated flat wavefront to represent optical infinity,
more and more beam divergence/wavefront curvature to represent
closer viewing distance relative to the eye 58).
[0066] To compensate for the variable focus lens element (166)
between the eye (58) and the waveguide (164), another similar
variable focus lens element (167) is placed on the opposite side of
the waveguide (164) to cancel out the optical effects of the lenses
(166) for light coming from the world (144) for augmented reality
(i.e., as described above, one lens compensates for the other,
producing the functional equivalent of a zero-magnification
telescope).
[0067] The variable focus lens element (166) may be a refractive
element, such as a liquid crystal lens, an electro-active lens, a
conventional refractive lens with moving elements, a
mechanical-deformation-based lens (such as a fluid-filled membrane
lens, or a lens akin to the human crystalline lens wherein a
flexible element is flexed and relaxed by actuators), an
electrowetting lens, or a plurality of fluids with different
refractive indices. The variable focus lens element (166) may also
comprise a switchable diffractive optical element (such as one
featuring a polymer dispersed liquid crystal approach wherein a
host medium, such as a polymeric material, has microdroplets of
liquid crystal dispersed within the material; when a voltage is
applied, the molecules reorient so that their refractive indices no
longer match that of the host medium, thereby creating a
high-frequency switchable diffraction pattern).
[0068] One embodiment includes a host medium in which microdroplets
of a Kerr effect-based electro-active material, such as lithium
niobate, is dispersed within the host medium, enabling refocusing
of image information on a pixel-by-pixel or line-by-line basis,
when coupled with a scanning light display, such as a fiber-scanned
display or scanning-mirror-based display. In a variable focus lens
element (166) configuration wherein liquid crystal, lithium
niobate, or other technology is utilized to present a pattern, the
pattern spacing may be modulated to not only change the focal power
of the variable focus lens element (166), but also to change the
focal power of the overall optical system--for a zoom lens type of
functionality.
[0069] In one embodiment, the lenses (166) could be telecentric, in
that focus of the display imagery can be altered while keeping
magnification constant--in the same way that a photography zoom
lens may be configured to decouple focus from zoom position. In
another embodiment, the lenses (166) may be non-telecentric, so
that focus changes will also slave zoom changes. With such a
configuration, such magnification changes may be compensated for in
software with dynamic scaling of the output from the graphics
system in sync with focus changes).
[0070] Referring back to the projector or other video display unit
(160) and the issue of how to feed images into the optical display
system, in a "frame sequential" configuration, a stack of
sequential two-dimensional images may be fed to the display
sequentially to produce three-dimensional perception over time; in
a manner akin to the manner in which a computed tomography system
uses stacked image slices to represent a three-dimensional
structure. A series of two-dimensional image slices may be
presented to the eye, each at a different focal distance to the
eye, and the eye/brain would integrate such a stack into a
perception of a coherent three-dimensional volume. Depending upon
the display type, line-by-line, or even pixel-by-pixel sequencing
may be conducted to produce the perception of three-dimensional
viewing. For example, with a scanned light display (such as a
scanning fiber display or scanning mirror display), then the
display is presenting the waveguide (164) with one line or one
pixel at a time in a sequential fashion.
[0071] If the variable focus lens element (166) is able to keep up
with the high-frequency of pixel-by-pixel or line-by-line
presentation, then each line or pixel may be presented and
dynamically focused through the variable focus lens element (166)
to be perceived at a different focal distance from the eye (58).
Pixel-by-pixel focus modulation generally requires an extremely
fast/high-frequency variable focus lens element (166). For example,
a 1080P resolution display with an overall frame rate of 60 frames
per second typically presents around 125 million pixels per second.
Such a configuration also may be constructed using a solid state
switchable lens, such as one using an electro-active material,
e.g., lithium niobate or an electro-active polymer. In addition to
its compatibility with the system illustrated in FIG. 7A, a frame
sequential multi-focal display driving approach may be used in
conjunction with a number of the display system and optics
embodiments described in this disclosure.
[0072] Referring to FIG. 7B, with an electro-active layer (172)
(such as one comprising liquid crystal or lithium niobate)
surrounded by functional electrodes (170, 174) which may be made of
indium tin oxide, a waveguide (168) with a conventional
transmissive substrate (176, such as one made from glass or plastic
with known total internal reflection characteristics and an index
of refraction that matches the on or off state of the
electro-active layer 172) may be controlled such that the paths of
entering beams may be dynamically altered to essentially create a
time-varying light field.
[0073] Referring to FIG. 8A, a stacked waveguide assembly (178) may
be utilized to provide three-dimensional perception to the
eye/brain by having a plurality of waveguides (182, 184, 186, 188,
190) and a plurality of weak lenses (198, 196, 194, 192) configured
together to send image information to the eye with various levels
of wavefront curvature for each waveguide level indicative of focal
distance to be perceived for that waveguide level. A plurality of
displays (200, 202, 204, 206, 208), or in another embodiment a
single multiplexed display, may be utilized to inject collimated
image information into the waveguides (182, 184, 186, 188, 190),
each of which may be configured, as described above, to distribute
incoming light substantially equally across the length of each
waveguide, for exit down toward the eye.
[0074] The waveguide (182) nearest the eye is configured to deliver
collimated light, as injected into such waveguide (182), to the
eye, which may be representative of the optical infinity focal
plane. The next waveguide up (184) is configured to send out
collimated light which passes through the first weak lens (192;
e.g., a weak negative lens) before it can reach the eye (58); such
first weak lens (192) may be configured to create a slight convex
wavefront curvature so that the eye/brain interprets light coming
from that next waveguide up (184) as coming from a first focal
plane closer inward toward the person from optical infinity.
Similarly, the third up waveguide (186) passes its output light
through both the first (192) and second (194) lenses before
reaching the eye (58); the combined optical power of the first
(192) and second (194) lenses may be configured to create another
incremental amount of wavefront divergence so that the eye/brain
interprets light coming from that third waveguide up (186) as
coming from a second focal plane even closer inward toward the
person from optical infinity than was light from the next waveguide
up (184).
[0075] The other waveguide layers (188, 190) and weak lenses (196,
198) are similarly configured, with the highest waveguide (190) in
the stack sending its output through all of the weak lenses between
it and the eye for an aggregate focal power representative of the
closest focal plane to the person. To compensate for the stack of
lenses (198, 196, 194, 192) when viewing/interpreting light coming
from the world (144) on the other side of the stacked waveguide
assembly (178), a compensating lens layer (180) is disposed at the
top of the stack to compensate for the aggregate power of the lens
stack (198, 196, 194, 192) below. Such a configuration provides as
many perceived focal planes as there are available waveguide/lens
pairings, again with a relatively large exit pupil configuration as
described above. Both the reflective aspects of the waveguides and
the focusing aspects of the lenses may be static (i.e., not dynamic
or electro-active). In an alternative embodiment they may be
dynamic using electro-active features as described above, enabling
a small number of waveguides to be multiplexed in a time sequential
fashion to produce a larger number of effective focal planes.
[0076] Referring to FIGS. 8B-8N, various aspects of diffraction
configurations for focusing and/or redirecting collimated beams are
depicted. Other aspects of diffraction systems for such purposes
are disclosed in U.S. Patent Application Ser. No. 61/845,907 (U.S.
patent application Ser. No. 14/331,218), which is incorporated by
reference herein in its entirety. Referring to FIG. 8B, passing a
collimated beam through a linear diffraction pattern (210), such as
a Bragg grating, will deflect, or "steer", the beam. Passing a
collimated beam through a radially symmetric diffraction pattern
(212), or "Fresnel zone plate", will change the focal point of the
beam. FIG. 8C illustrates the deflection effect of passing a
collimated beam through a linear diffraction pattern (210); FIG. 8D
illustrates the focusing effect of passing a collimated beam
through a radially symmetric diffraction pattern (212).
[0077] Referring to FIGS. 8E and 8F, a combination diffraction
pattern that has both linear and radial elements (214) produces
both deflection and focusing of a collimated input beam. These
deflection and focusing effects can be produced in a reflective as
well as transmissive mode. These principles may be applied with
waveguide configurations to allow for additional optical system
control, as shown in FIGS. 8G-8N, for example. As shown in FIGS.
8G-8N, a diffraction pattern (220), or "diffractive optical
element" (or "DOE") has been embedded within a planar waveguide
(216) such that as a collimated beam is totally internally
reflected along the planar waveguide (216), it intersects the
diffraction pattern (220) at a multiplicity of locations.
[0078] Preferably, the DOE (220) has a relatively low diffraction
efficiency so that only a portion of the light of the beam is
deflected away toward the eye (58) with each intersection of the
DOE (220) while the rest continues to move through the planar
waveguide (216) via total internal reflection; the light carrying
the image information is thus divided into a number of related
light beams that exit the waveguide at a multiplicity of locations
and the result is a fairly uniform pattern of exit emission toward
the eye (58) for this particular collimated beam bouncing around
within the planar waveguide (216), as shown in FIG. 8H. The exit
beams toward the eye (58) are shown in FIG. 8H as substantially
parallel, because, in this case, the DOE (220) has only a linear
diffraction pattern. As shown in the comparison between FIGS. 8L,
8M, and 8N, changes to this linear diffraction pattern pitch may be
utilized to controllably deflect the exiting parallel beams,
thereby producing a scanning or tiling functionality.
[0079] Referring back to FIG. 8I, with changes in the radially
symmetric diffraction pattern component of the embedded DOE (220),
the exit beam pattern is more divergent, which would require the
eye to accommodation to a closer distance to bring it into focus on
the retina and would be interpreted by the brain as light from a
viewing distance closer to the eye than optical infinity. Referring
to FIG. 8J, with the addition of another waveguide (218) into which
the beam may be injected (by a projector or display, for example),
a DOE (221) embedded in this other waveguide (218), such as a
linear diffraction pattern, may function to spread the light across
the entire larger planar waveguide (216), which functions to
provide the eye (58) with a very large incoming field of incoming
light that exits from the larger planar waveguide (216), i.e., a
large eye box, in accordance with the particular DOE configurations
at work.
[0080] The DOEs (220, 221) are depicted bisecting the associated
waveguides (216, 218) but this need not be the case; they could be
placed closer to, or upon, either side of either of the waveguides
(216, 218) to have the same functionality. Thus, as shown in FIG.
8K, with the injection of a single collimated beam, an entire field
of cloned collimated beams may be directed toward the eye (58). In
addition, with a combined linear diffraction pattern/radially
symmetric diffraction pattern scenario such as that depicted in
FIGS. 8F (214) and 8I (220), a beam distribution waveguide optic
(for functionality such as exit pupil functional expansion; with a
configuration such as that of FIG. 8K, the exit pupil can be as
large as the optical element itself, which can be a very
significant advantage for user comfort and ergonomics) with Z-axis
focusing capability is presented, in which both the divergence
angle of the cloned beams and the wavefront curvature of each beam
represent light coming from a point closer than optical
infinity.
[0081] In one embodiment, one or more DOEs are switchable between
"on" states in which they actively diffract, and "off" states in
which they do not significantly diffract. For instance, a
switchable DOE may comprise a layer of polymer dispersed liquid
crystal, in which microdroplets comprise a diffraction pattern in a
host medium, and the refractive index of the microdroplets can be
switched to substantially match the refractive index of the host
material (in which case the pattern does not appreciably diffract
incident light) or the microdroplet can be switched to an index
that does not match that of the host medium (in which case the
pattern actively diffracts incident light). Further, with dynamic
changes to the diffraction terms, such as the linear diffraction
pitch term as in FIGS. 8L-8N, a beam scanning or tiling
functionality may be achieved. As noted above, it is desirable to
have a relatively low diffraction grating efficiency in each of the
DOEs (220, 221) because it facilitates distribution of the light,
and also because light coming through the waveguides that is
desirably transmitted (for example, light coming from the world 144
toward the eye 58 in an augmented reality configuration) is less
affected when the diffraction efficiency of the DOE that it crosses
(220) is lower--so a better view of the real world through such a
configuration is achieved.
[0082] Configurations such as those illustrated in FIG. 8K
preferably are driven with injection of image information in a time
sequential approach, with frame sequential driving being the most
straightforward to implement. For example, an image of the sky at
optical infinity may be injected at time1 and the diffraction
grating retaining collimation of light may be utilized; then an
image of a closer tree branch may be injected at time2 while a DOE
controllably imparts a focal change, say one diopter or 1 meter
away, to provide the eye/brain with the perception that the branch
light information is coming from the closer focal range. This kind
of paradigm can be repeated in rapid time sequential fashion such
that the eye/brain perceives the input to be all part of the same
image. This is just a two focal plane example; preferably the
system will be configured to have more focal planes to provide a
smoother transition between objects and their focal distances. This
kind of configuration generally assumes that the DOE is switched at
a relatively low speed (i.e., in sync with the frame-rate of the
display that is injecting the images--in the range of tens to
hundreds of cycles/second).
[0083] The opposite extreme may be a configuration wherein DOE
elements can shift focus at tens to hundreds of MHz or greater,
which facilitates switching of the focus state of the DOE elements
on a pixel-by-pixel basis as the pixels are scanned into the eye
(58) using a scanned light display type of approach. This is
desirable because it means that the overall display frame-rate can
be kept quite low; just low enough to make sure that "flicker" is
not a problem (in the range of about 60-120 frames/sec).
[0084] In between these ranges, if the DOEs can be switched at KHz
rates, then on a line-by-line basis the focus on each scan line may
be adjusted, which may afford the user with a visible benefit in
terms of temporal artifacts during an eye motion relative to the
display, for example. For instance, the different focal planes in a
scene may, in this manner, be interleaved, to minimize visible
artifacts in response to a head motion (as is discussed in greater
detail later in this disclosure). A line-by-line focus modulator
may be operatively coupled to a line scan display, such as a
grating light valve display, in which a linear array of pixels is
swept to form an image; and may be operatively coupled to scanned
light displays, such as fiber-scanned displays and mirror-scanned
light displays.
[0085] A stacked configuration, similar to those of FIG. 8A, may
use dynamic DOEs (rather than the static waveguides and lenses of
the embodiment of FIG. 8A) to provide multi-planar focusing
simultaneously. For example, with three simultaneous focal planes,
a primary focus plane (based upon measured eye accommodation, for
example) could be presented to the user, and a +margin and -margin
(i.e., one focal plane closer, one farther out) could be utilized
to provide a large focal range in which the user can accommodate
before the planes need be updated. This increased focal range can
provide a temporal advantage if the user switches to a closer or
farther focus (i.e., as determined by accommodation measurement);
then the new plane of focus could be made to be the middle depth of
focus, with the + and - margins again ready for a fast switchover
to either one while the system catches up.
[0086] Referring to FIG. 8O, a stack (222) of planar waveguides
(244, 246, 248, 250, 252) is shown, each having a reflector (254,
256, 258, 260, 262) at the end and being configured such that
collimated image information injected in one end by a display (224,
226, 228, 230, 232) bounces by total internal reflection down to
the reflector, at which point some or all of the light is reflected
out toward an eye or other target. Each of the reflectors may have
slightly different angles so that they all reflect exiting light
toward a common destination such as a pupil. Such a configuration
is somewhat similar to that of FIG. 5B, with the exception that
each different angled reflector in the embodiment of FIG. 8O has
its own waveguide for less interference when projected light is
travelling to the targeted reflector. Lenses (234, 236, 238, 240,
242) may be interposed between the displays and waveguides for beam
steering and/or focusing.
[0087] FIG. 8P illustrates a geometrically staggered version
wherein reflectors (276, 278, 280, 282, 284) are positioned at
staggered lengths in the waveguides (266, 268, 270, 272, 274) so
that exiting beams may be relatively easily aligned with objects
such as an anatomical pupil. With knowledge of how far the stack
(264) is going to be from the eye (such as 28 mm between the cornea
of the eye and an eyeglasses lens, a typical comfortable geometry),
the geometries of the reflectors (276, 278, 280, 282, 284) and
waveguides (266, 268, 270, 272, 274) may be set up to fill the eye
pupil (typically about 8 mm across or less) with exiting light. By
directing light to an eye box larger than the diameter of the eye
pupil, the viewer may make eye movements while retaining the
ability to see the displayed imagery. Referring back to the
discussion related to FIGS. 5A and 5B about field of view expansion
and reflector size, an expanded field of view is presented by the
configuration of FIG. 8P as well, and it does not involve the
complexity of the switchable reflective elements of the embodiment
of FIG. 5B.
[0088] FIG. 8Q illustrates a version wherein many reflectors (298)
form a relatively continuous curved reflection surface in the
aggregate or discrete flat facets that are oriented to align with
an overall curve. The curve could a parabolic or elliptical curve
and is shown cutting across a plurality of waveguides (288, 290,
292, 294, 296) to minimize any crosstalk issues, although it also
could be utilized with a monolithic waveguide configuration.
[0089] In one implementation, a high-frame-rate and lower
persistence display may be combined with a lower-frame-rate and
higher persistence display and a variable focus element to comprise
a relatively high-frequency frame sequential volumetric display. In
one embodiment, the high-frame-rate display has a lower bit depth
and the lower-frame-rate display has a higher bit depth, and are
combined to comprise an effective high-frame-rate and high bit
depth display, that is well suited to presenting image slices in a
frame sequential fashion. With such an approach, a
three-dimensional volume that is desirably represented is
functionally divided into a series of two-dimensional slices. Each
of those two-dimensional slices is projected to the eye frame
sequentially, and in sync with this presentation, the focus of a
variable focus element is changed.
[0090] In one embodiment, to get enough frame rate to support such
a configuration, two display elements may be integrated: a
full-color, high-resolution liquid crystal display ("LCD"; a
backlighted ferroelectric panel display also may be utilized in
another embodiment; in a further embodiment a scanning fiber
display may be utilized) operating at 60 frames per second, and
aspects of a higher-frequency DLP system. Instead of illuminating
the back of the LCD panel in a conventional manner (i.e., with a
full size fluorescent lamp or LED array), the conventional lighting
configuration may be removed to accommodate using the DLP projector
to project a mask pattern on the back of the LCD (in one
embodiment, the mask pattern may be binary in that the DLP either
projects illumination, or not-illumination; in another embodiment
described below, the DLP may be utilized to project a grayscale
mask image).
[0091] DLP projection systems can operate at very high frame rates;
in one embodiment for 6 depth planes at 60 frames per second, a DLP
projection system can be operated against the back of the LCD
display at 360 frames/second. Then the DLP projector is utilized to
selectively illuminate portions of the LCD panel in sync with a
high-frequency variable focus element (such as a deformable
membrane mirror) that is disposed between the viewing side of the
LCD panel and the eye of the user, the variable focus element being
used to change the global display focus on a frame by frame basis
at 360 frames/second. In one embodiment, the variable focus element
is positioned to be optically conjugate to the exit pupil, to
enable adjustments of focus without simultaneously affecting image
magnification or "zoom." In another embodiment, the variable focus
element is not conjugate to the exit pupil, such that image
magnification changes accompany focus adjustments, and software is
used to compensate for these optical magnification changes and any
distortions by pre-scaling or warping the images to be
presented.
[0092] Operationally, it's useful to consider an example again
wherein a three-dimensional scene is to be presented to a user
wherein the sky in the background is to be at a viewing distance of
optical infinity, and wherein a branch coupled to a tree located at
a certain location closer to the user than optical infinity extends
from the tree trunk in a direction toward the user, so that the tip
of the branch is closer to the user than is the proximal portion of
the branch that joins the tree trunk.
[0093] In one embodiment, for a given global frame, the system may
be configured to present on an LCD a full-color, all in-focus image
of the tree branch in front the sky. Then at subframe1, within the
global frame, the DLP projector in a binary masking configuration
(i.e., illumination or absence of illumination) may be used to only
illuminate the portion of the LCD that represents the cloudy sky
while functionally black-masking (i.e., failing to illuminate) the
portion of the LCD that represents the tree branch and other
elements that are not to be perceived at the same focal distance as
the sky, and the variable focus element (such as a deformable
membrane mirror) may be utilized to position the focal plane at
optical infinity so that the eye sees a sub-image at subframe1 as
being clouds that are infinitely far away.
[0094] Then at subframe2, the variable focus element may be
switched to focusing on a point about 1 meter away from the user's
eyes (or whatever distance is required; here 1 meter for the branch
location is used for illustrative purposes), the pattern of
illumination from the DLP can be switched so that the system only
illuminates the portion of the LCD that represents the tree branch
while functionally black-masking (i.e., failing to illuminate) the
portion of the LCD that represents the sky and other elements that
are not to be perceived at the same focal distance as the tree
branch. Thus the eye gets a quick flash of cloud at optical
infinity followed by a quick flash of tree at 1 meter, and the
sequence is integrated by the eye/brain to form a three-dimensional
perception. The branch may be positioned diagonally relative to the
viewer, such that it extends through a range of viewing distances,
e.g., it may join with the trunk at around 2 meters viewing
distance while the tips of the branch are at the closer position of
1 meter.
[0095] In this case, the display system can divide the 3-D volume
of the tree branch into multiple slices, rather than a single slice
at 1 meter. For instance, one focus slice may be used to represent
the sky (using the DLP to mask all areas of the tree during
presentation of this slice), while the tree branch is divided
across 5 focus slices (using the DLP to mask the sky and all
portions of the tree except one, for each part of the tree branch
to be presented). Preferably, the depth slices are positioned with
a spacing equal to or smaller than the depth of focus of the eye,
such that the viewer will be unlikely to notice the transition
between slices, and instead perceive a smooth and continuous flow
of the branch through the focus range.
[0096] In another embodiment, rather than utilizing the DLP in a
binary (illumination or darkfield only) mode, it may be utilized to
project a grayscale (for example, 256 shades of grayscale) mask
onto the back of the LCD panel to enhance three-dimensional
perception. The grayscale shades may be utilized to impart to the
eye/brain a perception that something resides in between adjacent
depth or focal planes. Back to the branch and clouds scenario, if
the leading edge of the branch closest to the user is to be in
focalplane1, then at subframe1, that portion branch on the LCD may
be lit up with full intensity white from the DLP system with the
variable focus element at focalplane1.
[0097] Then at subframe2, with the variable focus element at
focalplane2 right behind the part that was lit up, there would be
no illumination. These are similar steps to the binary DLP masking
configuration above. However, if there is a portion of the branch
that is to be perceived at a position between focalplane1 and
focalplane1, e.g., halfway, grayscale masking can be utilized. The
DLP can project an illumination mask to that portion during both
subframe1 and subframe2, but at half-illumination (such as at level
128 out of 256 grayscale) for each subframe. This provides the
perception of a blending of depth of focus layers, with the
perceived focal distance being proportional to the illuminance
ratio between subframe1 and subframe2. For instance, for a portion
of the tree branch that should lie 3/4ths of the way between
focalplane1 and focalplane2, an about 25% intensity grayscale mask
can be used to illuminate that portion of the LCD at subframe1 and
an about 75% grayscale mask can be used to illuminate the same
portion of the LCD at subframe2.
[0098] In one embodiment, the bit depths of both the low-frame-rate
display and the high-frame-rate display can be combined for image
modulation, to create a high dynamic range display. The high
dynamic range driving may be conducted in tandem with the focus
plane addressing function described above, to comprise a high
dynamic range multi-focal 3-D display.
[0099] In another embodiment that may be more efficient on
computation resources, only a certain portion of the display (i.e.,
LCD) output may be mask-illuminated by the DMD and variably focused
en route to the user's eye. For example, the middle portion of the
display may be mask illuminated, with the periphery of the display
not providing varying accommodation cues to the user (i.e. the
periphery could be uniformly illuminated by the DLP DMD, while a
central portion is actively masked and variably focused en route to
the eye).
[0100] In the above described embodiment, a refresh rate of about
360 Hz allows for 6 depth planes at about 60 frames/second each. In
another embodiment, even higher refresh rates may be achieved by
increasing the operating frequency of the DLP. A standard DLP
configuration uses a MEMS device and an array of micro-mirrors that
toggle between a mode of reflecting light toward the display or
user to a mode of reflecting light away from the display or user,
such as into a light trap--thus they are inherently binary. DLPs
typically create grayscale images using a pulse width modulation
schema wherein the mirror is left in the "on" state for a variable
amount of time for a variable duty cycle in order to create a
brighter pixel, or pixel of interim brightness. Thus, to create
grayscale images at moderate frame rate, they are running at a much
higher binary rate.
[0101] In the above described configurations, such setup works well
for creating grayscale masking. However, if the DLP drive scheme is
adapted so that it is flashing subimages in a binary pattern, then
the frame rate may be increased significantly--by thousands of
frames per second, which allows for hundreds to thousands of depth
planes being refreshed at 60 frames/second, which may be utilized
to obviate the between-depth-plane grayscale interpolating as
described above. A typical pulse width modulation scheme for a
Texas Instruments DLP system has an 8-bit command signal (first bit
is the first long pulse of the mirror; second bit is a pulse that
is half as long as the first; third bit is half as long again; and
so on)--so that the configuration can create 2 to the 8th power
different illumination levels. In one embodiment, the backlighting
from the DLP may have its intensity varied in sync with the
different pulses of the DMD to equalize the brightness of the
subimages that are created, which is a practical workaround to get
existing DMD drive electronics to produce significantly higher
frame rates.
[0102] In another embodiment, direct control changes to the DMD
drive electronics and software may be utilized to have the mirrors
always have an equal on-time instead of the variable on-time
configuration that is conventional, which would facilitate higher
frame rates. In another embodiment, the DMD drive electronics may
be configured to present low bit depth images at a frame rate above
that of high bit depth images but lower than the binary frame rate,
enabling some grayscale blending between focus planes, while
moderately increasing the number of focus planes.
[0103] In another embodiment, when limited to a finite number of
depth planes, such as 6 in the example above, it is desirable to
functionally move these 6 depth planes around to be maximally
useful in the scene that is being presented to the user. For
example, if a user is standing in a room and a virtual monster is
to be placed into his augmented reality view, the virtual monster
being about 2 feet deep in the Z axis straight away from the user's
eyes, then it makes sense to cluster all 6 depth planes around the
center of the monster's current location (and dynamically move them
with him as he moves relative to the user)--so that more rich
accommodation cues may be provided for the user, with all six depth
planes in the direct region of the monster (for example, 3 in front
of the center of the monster, 3 in back of the center of the
monster). Such allocation of depth planes is content dependent.
[0104] For example, in the scene above the same monster is to be
presented in the same room, but also to be presented to the user is
a virtual window frame element, and then a virtual view to optical
infinity out of the virtual window frame, it will be useful to
spend at least one depth plane on optical infinity, one on the
depth of the wall that is to house the virtual window frame, and
then perhaps the remaining four depth planes on the monster in the
room. If the content causes the virtual window to disappear, then
the two depth planes may be dynamically reallocated to the region
around the monster, and so on--content-based dynamic allocation of
focal plane resources to provide the most rich experience to the
user given the computing and presentation resources.
[0105] In another embodiment, phase delays in a multicore fiber or
an array of single-core fibers may be utilized to create variable
focus light wavefronts. Referring to FIG. 9A, a multicore fiber
(300) may comprise the aggregation of multiple individual fibers
(302); FIG. 9B shows a close-up view of a multicore assembly, which
emits light from each core in the form of a spherical wavefront
(304) from each. If the cores are transmitting coherent light,
e.g., from a shared laser light source, these small spherical
wavefronts ultimately constructively and destructively interfere
with each other, and if they were emitted from the multicore fiber
in phase, they will develop an approximately planar wavefront (306)
in the aggregate, as shown. However, if phase delays are induced
between the cores (using a conventional phase modulator such as one
using lithium niobate, for example, to slow the path of some cores
relative to others), then a curved or spherical wavefront may be
created in the aggregate, to represent at the eyes/brain an object
coming from a point closer than optical infinity, which presents
another option that may be used in place of the variable focus
elements described above. In other words, such a phased multicore
configuration, or phased array, may be utilized to create multiple
optical focus levels from a light source.
[0106] In another embodiment related to the use of optical fibers,
a known Fourier transform aspect of multi-mode optical fiber or
light guiding rods or pipes may be utilized for control of the
wavefronts that are output from such fiber. Optical fibers
typically are available in two categories: single mode and
multi-mode. Multi-mode optical fiber typically has larger core
diameters and allows light to propagate along multiple angular
paths, rather than just the one of single mode optical fiber. It is
known that if an image is injected into one end of a multi-mode
fiber, that angular differences that are encoded into that image
will be retained to some degree as it propagates through the
multi-mode fiber, and for some configurations the output from the
fiber will be significantly similar to a Fourier transform of the
image that was input.
[0107] Thus in one embodiment, the inverse Fourier transform of a
wavefront (such as a diverging spherical wavefront to represent a
focal plane nearer to the user than optical infinity) may be input
so that, after passing through the fiber that optically imparts a
Fourier transform, the output is the desired shaped, or focused,
wavefront. Such output end may be scanned about to be used as a
scanned fiber display, or may be used as a light source for a
scanning mirror to form an image, for instance. Thus such a
configuration may be utilized as yet another focus modulation
subsystem. Other kinds of light patterns and wavefronts may be
injected into a multi-mode fiber, such that on the output end, a
certain spatial pattern is emitted. This may be utilized to have
the equivalent of a wavelet pattern (in optics, an optical system
may be analyzed in terms of what are called the Zernicke
coefficients; images may be similarly characterized and decomposed
into smaller principal components, or a weighted combination of
comparatively simpler image components). Thus if light is scanned
into the eye using the principal components on the input side, a
higher resolution image may be recovered at the output end of the
multi-mode fiber.
[0108] In another embodiment, the Fourier transform of a hologram
may be injected into the input end of a multi-mode fiber to output
a wavefront that may be used for three-dimensional focus modulation
and/or resolution enhancement. Certain single fiber core,
multi-core fibers, or concentric core+cladding configurations also
may be utilized in the aforementioned inverse Fourier transform
configurations.
[0109] In another embodiment, rather than physically manipulating
the wavefronts approaching the eye of the user at a high frame rate
without regard to the user's particular state of accommodation or
eye gaze, a system may be configured to monitor the user's
accommodation and rather than presenting a set of multiple
different light wavefronts, present a single wavefront at a time
that corresponds to the accommodation state of the eye.
Accommodation may be measured directly (such as by infrared
autorefractor or eccentric photorefraction) or indirectly (such as
by measuring the convergence level of the two eyes of the user; as
described above, vergence and accommodation are strongly linked
neurologically, so an estimate of accommodation can be made based
upon vergence geometry). Thus with a determined accommodation of,
say, 1 meter from the user, then the wavefront presentations at the
eye may be configured for a 1 meter focal distance using any of the
above variable focus configurations. If an accommodation change to
focus at 2 meters is detected, the wavefront presentation at the
eye may be reconfigured for a 2 meter focal distance, and so
on.
[0110] Thus in one embodiment incorporating accommodation tracking,
a variable focus element may be placed in the optical path between
an outputting combiner (e.g., a waveguide or beamsplitter) and the
eye of the user, so that the focus may be changed along with (i.e.,
preferably at the same rate as) accommodation changes of the eye.
Software effects may be utilized to produce variable amounts blur
(e.g., Gaussian) to objects which should not be in focus to
simulate the dioptric blur expected at the retina if an object were
at that viewing distance and enhance the three-dimensional
perception by the eyes/brain.
[0111] A simple embodiment is a single plane whose focus level is
slaved to the viewer's accommodation level, however the performance
demands on the accommodation tracking system can be relaxed if even
a low number of multiple planes are used. Referring to FIG. 10, in
another embodiment, a stack (328) of about 3 waveguides (318, 320,
322) may be utilized to create three focal planes worth of
wavefronts simultaneously. In one embodiment, the weak lenses (324,
326) may have static focal distances, and a variable focal lens
(316) may be slaved to the accommodation tracking of the eyes such
that one of the three waveguides (say the middle waveguide 320)
outputs what is deemed to be the in-focus wavefront, while the
other two waveguides (322, 318) output a +margin wavefront and a
-margin wavefront (i.e., a little farther than detected focal
distance, a little closer than detected focal distance) which may
improve the three-dimensional perception and also provide enough
difference for the brain/eye accommodation control system to sense
some blur as negative feedback, which enhances the perception of
reality, and allows a range of accommodation before an physical
adjustment of the focus levels is necessary.
[0112] A variable focus compensating lens (314) is also shown to
ensure that light coming in from the real world (144) in an
augmented reality configuration is not refocused or magnified by
the assembly of the stack (328) and output lens (316). The variable
focus in the lenses (316, 314) may be achieved, as discussed above,
with refractive, diffractive, or reflective techniques.
[0113] In another embodiment, each of the waveguides in a stack may
contain their own capability for changing focus (such as by having
an included electronically switchable DOE) so that the variable
focus element need not be centralized as in the stack (328) of the
configuration of FIG. 10.
[0114] In another embodiment, variable focus elements may be
interleaved between the waveguides of a stack (i.e., rather than
fixed focus weak lenses as in the embodiment of FIG. 10) to obviate
the need for a combination of fixed focus weak lenses plus
whole-stack-refocusing variable focus element.
[0115] Such stacking configurations may be used in accommodation
tracked variations as described herein, and also in a
frame-sequential multi-focal display approach.
[0116] In a configuration wherein light enters the pupil with a
small exit pupil, such as 1/2 mm diameter or less, one has the
equivalent of a pinhole lens configuration wherein the beam is
always interpreted as in-focus by the eyes/brain--e.g., a scanned
light display using a 0.5 mm diameter beam to scan images to the
eye. Such a configuration is known as a Maxwellian view
configuration, and in one embodiment, accommodation tracking input
may be utilized to induce blur using software to image information
that is to be perceived as at a focal plane behind or in front of
the focal plane determined from the accommodation tracking. In
other words, if one starts with a display presenting a Maxwellian
view, then everything theoretically can be in focus, and to provide
a rich and natural three-dimensional perception, simulated dioptric
blur may be induced with software, and may be slaved to the
accommodation tracking status.
[0117] In one embodiment a scanning fiber display is well suited to
such configuration because it may be configured to only output
small-diameter beams in a Maxwellian form. In another embodiment,
an array of small exit pupils may be created to increase the
functional eye box of the system (and also to reduce the impact of
a light-blocking particle which may reside in the vitreous or
cornea of the eye), such as by one or more scanning fiber displays,
or by a DOE configuration such as that described in reference to
FIG. 8K, with a pitch in the array of presented exit pupils that
ensure that only one will hit the anatomical pupil of the user at
any given time (for example, if the average anatomical pupil
diameter is 4 mm, one configuration may comprise 1/2 mm exit pupils
spaced at intervals of approximate 4 mm apart). Such exit pupils
may also be switchable in response to eye position, such that only
the eye always receives one, and only one, active small exit pupil
at a time; allowing a denser array of exit pupils. Such user will
have a large depth of focus to which software-based blur techniques
may be added to enhance perceived depth perception.
[0118] As discussed above, an object at optical infinity creates a
substantially planar wavefront; an object closer, such as 1 m away
from the eye, creates a curved wavefront (with about 1 m convex
radius of curvature). The eye's optical system needs to have enough
optical power to bend the incoming rays of light so that they end
up focused on the retina (convex wavefront gets turned into
concave, and then down to a focal point on the retina). These are
basic functions of the eye.
[0119] In many of the embodiments described above, light directed
to the eye has been treated as being part of one continuous
wavefront, some subset of which would hit the pupil of the
particular eye. In another approach, light directed to the eye may
be effectively discretized or broken down into a plurality of
beamlets or individual rays, each of which has a diameter less than
about 0.5 mm and a unique propagation pathway as part of a greater
aggregated wavefront that may be functionally created with the an
aggregation of the beamlets or rays. For example, a curved
wavefront may be approximated by aggregating a plurality of
discrete neighboring collimated beams, each of which is approaching
the eye from an appropriate angle to represent a point of origin
that matches the center of the radius of curvature of the desired
aggregate wavefront.
[0120] When the beamlets have a diameter of about 0.5 mm or less,
it is as though it is coming through a pinhole lens configuration,
which means that each individual beamlet is always in relative
focus on the retina, independent of the accommodation state of the
eye--however the trajectory of each beamlet will be affected by the
accommodation state. For instance, if the beamlets approach the eye
in parallel, representing a discretized collimated aggregate
wavefront, then an eye that is correctly accommodated to infinity
will deflect the beamlets to all converge upon the same shared spot
on the retina, and will appear in focus. If the eye accommodates
to, say, 1 m, the beams will be converged to a spot in front of the
retina, cross paths, and fall on multiple neighboring or partially
overlapping spots on the retina--appearing blurred.
[0121] If the beamlets approach the eye in a diverging
configuration, with a shared point of origin 1 meter from the
viewer, then an accommodation of 1 m will steer the beams to a
single spot on the retina, and will appear in focus; if the viewer
accommodates to infinity, the beamlets will converge to a spot
behind the retina, and produce multiple neighboring or partially
overlapping spots on the retina, producing a blurred image. Stated
more generally, the accommodation of the eye determines the degree
of overlap of the spots on the retina, and a given pixel is "in
focus" when all of the spots are directed to the same spot on the
retina and "defocused" when the spots are offset from one another.
This notion that all of the 0.5 mm diameter or less beamlets are
always in focus, and that they may be aggregated to be perceived by
the eyes/brain as though they are substantially the same as
coherent wavefronts, may be utilized in producing configurations
for comfortable three-dimensional virtual or augmented reality
perception.
[0122] In other words, a set of multiple narrow beams may be used
to emulate what is going on with a larger diameter variable focus
beam, and if the beamlet diameters are kept to a maximum of about
0.5 mm, then they maintain a relatively static focus level, and to
produce the perception of out-of-focus when desired, the beamlet
angular trajectories may be selected to create an effect much like
a larger out-of-focus beam (such a defocussing treatment may not be
the same as a Gaussian blur treatment as for the larger beam, but
will create a multimodal point spread function that may be
interpreted in a similar fashion to a Gaussian blur).
[0123] In a preferred embodiment, the beamlets are not mechanically
deflected to form this aggregate focus effect, but rather the eye
receives a superset of many beamlets that includes both a
multiplicity of incident angles and a multiplicity of locations at
which the beamlets intersect the pupil; to represent a given pixel
from a particular viewing distance, a subset of beamlets from the
superset that comprise the appropriate angles of incidence and
points of intersection with the pupil (as if they were being
emitted from the same shared point of origin in space) are turned
on with matching color and intensity, to represent that aggregate
wavefront, while beamlets in the superset that are inconsistent
with the shared point of origin are not turned on with that color
and intensity (but some of them may be turned on with some other
color and intensity level to represent, e.g., a different
pixel).
[0124] Referring to FIG. 11A, each of a multiplicity of incoming
beamlets (332) is passing through a small exit pupil (330) relative
to the eye (58) in a discretized wavefront display configuration.
Referring to FIG. 11B, a subset (334) of the group of beamlets
(332) may be driven with matching color and intensity levels to be
perceived as though they are part of the same larger-sized ray (the
bolded subgroup 334 may be deemed an "aggregated beam"). In this
case, the subset of beamlets are parallel to one another,
representing a collimated aggregate beam from optical infinity
(such as light coming from a distant mountain). The eye is
accommodated to infinity, so the subset of beamlets are deflected
by the eye's cornea and lens to all fall substantially upon the
same location of the retina and are perceived to comprise a single
in focus pixel.
[0125] FIG. 11C shows another subset of beamlets representing an
aggregated collimated beam (336) coming in from the right side of
the field of view of the user's eye (58) if the eye (58) is viewed
in a coronal-style planar view from above. Again, the eye is shown
accommodated to infinity, so the beamlets fall on the same spot of
the retina, and the pixel is perceived to be in focus. If, in
contrast, a different subset of beamlets were chosen that were
reaching the eye as a diverging fan of rays, those beamlets would
not fall on the same location of the retina (and be perceived as in
focus) until the eye were to shift accommodation to a near point
that matches the geometrical point of origin of that fan of
rays.
[0126] As regards patterns of points of intersection of beamlets
with the anatomical pupil of the eye (i.e., the pattern of exit
pupils), they may be organized in configurations such as a
cross-sectionally efficient hex-lattice (for example, as shown in
FIG. 12A) or a square lattice or other two-dimensional array.
Further, a three-dimensional array of exit pupils could be created,
as well as time-varying arrays of exit pupils.
[0127] Discretized aggregate wavefronts may be created using
several configurations, such as an array of microdisplays or
microprojectors placed optically conjugate with the exit pupil of
viewing optics, microdisplay or microprojector arrays coupled to a
direct field of view substrate (such as an eyeglasses lens) such
that they project light to the eye directly, without additional
intermediate viewing optics, successive spatial light modulation
array techniques, or waveguide techniques such as those described
in relation to FIG. 8K.
[0128] Referring to FIG. 12A, in one embodiment, a lightfield may
be created by bundling a group of small projectors or display units
(such as scanned fiber displays). FIG. 12A depicts a hexagonal
lattice projection bundle (338) which may, for example, create a 7
mm-diameter hex array with each fiber display outputting a
sub-image (340). If such an array has an optical system, such as a
lens, placed in front of it such that the array is placed optically
conjugate with the eye's entrance pupil, this will create an image
of the array at the eye's pupil, as shown in FIG. 12B, which
essentially provides the same optical arrangement as the embodiment
of FIG. 11A.
[0129] Each of the small exit pupils of the configuration is
created by a dedicated small display in the bundle (338), such as a
scanning fiber display. Optically, it's as though the entire hex
array (338) is positioned right into the anatomical pupil (45).
Such embodiments are means for driving different subimages to
different small exit pupils within the larger anatomical entrance
pupil (45) of the eye, comprising a superset of beamlets with a
multiplicity of incident angles and points of intersection with the
eye pupil. Each of the separate projectors or displays may be
driven with a slightly different image, such that subimages may be
created that pull out different sets of rays to be driven at
different light intensities and colors.
[0130] In one variation, a strict image conjugate may be created,
as in the embodiment of FIG. 12B, wherein there is direct 1-to-1
mapping of the array (338) with the pupil (45). In another
variation, the spacing may be changed between displays in the array
and the optical system (lens 342, in FIG. 12B) so that instead of
getting a conjugate mapping of the array to the eye pupil, the eye
pupil may be catching the rays from the array at some other
distance. With such a configuration, one would still get an angular
diversity of beams through which one could create a discretized
aggregate wavefront representation, but the mathematics regarding
how to drive which ray and at which power and intensity may become
more complex (although, on the other hand, such a configuration may
be considered simpler from a viewing optics perspective). The
mathematics involved with light field image capture may be
leveraged for these calculations.
[0131] Referring to FIG. 13A, another lightfield creating
embodiment is depicted wherein an array of microdisplays or
microprojectors (346) may be coupled to a frame (344; such as an
eyeglasses frame) to be positioned in front of the eye (58). The
depicted configuration is a nonconjugate arrangement wherein there
are no large-scale optical elements interposed between the displays
(for example, scanning fiber displays) of the array (346) and the
eye (58). One can imagine a pair of glasses, and coupled to those
glasses are a plurality of displays, such as scanning fiber
engines, positioned orthogonal to the eyeglasses surface, and all
angled inward so they are pointing at the pupil of the user. Each
display may be configured to create a set of rays representing
different elements of the beamlet superset.
[0132] With such a configuration, at the anatomical pupil (45) the
user is going to receive a similar result as received in the
embodiments discussed in reference to FIG. 11A, in which every
point at the user's pupil is receiving rays with a multiplicity of
angles of incidence and points of intersection that are being
contributed from the different displays. FIG. 13B illustrates a
nonconjugate configuration similar to that of FIG. 13A, with the
exception that the embodiment of FIG. 13B features a reflecting
surface (348) to facilitate moving the display array (346) away
from the eye's (58) field of view, while also allowing views of the
real world (144) through the reflective surface (348).
[0133] Thus another configuration for creating the angular
diversity necessary for a discretized aggregate wavefront display
is presented. To optimize such a configuration, the sizes of the
displays may be decreased to the maximum. Scanning fiber displays
which may be utilized as displays may have baseline diameters in
the range of 1 mm, but reduction in enclosure and projection lens
hardware may decrease the diameters of such displays to about 0.5
mm or less, which is less disturbing for a user. Another downsizing
geometric refinement may be achieved by directly coupling a
collimating lens (which may, for example, comprise a gradient
refractive index, or "GRIN", lens, a conventional curved lens, or a
diffractive lens) to the tip of the scanning fiber itself in a case
of a fiber scanning display array. For example, referring to FIG.
13D, a GRIN lens (354) is shown fused to the end of a single mode
optical fiber. An actuator (350; such as a piezoelectric actuator)
is coupled to the fiber (352) and may be used to scan the fiber
tip.
[0134] In another embodiment the end of the fiber may be shaped
into a hemispherical shape using a curved polishing treatment of an
optical fiber to create a lensing effect. In another embodiment a
standard refractive lens may be coupled to the end of each optical
fiber using an adhesive. In another embodiment a lens may be built
from a dab of transmissive polymeric material or glass, such as
epoxy. In another embodiment the end of an optical fiber may be
melted to create a curved surface for a lensing effect.
[0135] FIG. 13C-2 shows an embodiment wherein display
configurations (i.e., scanning fiber displays with GRIN lenses;
shown in close-up view of FIG. 13C-1) such as that shown in FIG.
13D may be coupled together through a single transparent substrate
(356) preferably having a refractive index that closely matches the
cladding of the optical fibers (352) so that the fibers themselves
are not very visible for viewing of the outside world across the
depicted assembly (if the index matching of the cladding is done
precisely, then the larger cladding/housing becomes transparent and
only the tiny cores, which preferably are about 3 microns in
diameter, will be obstructing the view. In one embodiment the
matrix (358) of displays may all be angled inward so they are
directed toward the anatomic pupil of the user (in another
embodiment, they may stay parallel to each other, but such a
configuration is less efficient).
[0136] Referring to FIG. 13E, another embodiment is depicted
wherein rather than using circular fibers to move cyclically, a
thin series of planar waveguides (358) are configured to be
cantilevered relative to a larger substrate structure (356). In one
variation, the substrate (356) may be moved to produce cyclic
motion (i.e., at the resonant frequency of the cantilevered members
358) of the planar waveguides relative to the substrate structure.
In another variation, the cantilevered waveguide portions (358) may
be actuated with piezoelectric or other actuators relative to the
substrate. Image illumination information may be injected, for
example, from the right side (360) of the substrate structure to be
coupled into the cantilevered waveguide portions (358). In one
embodiment the substrate (356) may comprise a waveguide configured
(such as with an integrated DOE configuration as described above)
to totally internally reflect incoming light (360) along its length
and then redirect it to the cantilevered waveguide portions (358).
As a person gazes toward the cantilevered waveguide portions (358)
and through to the real world (144) behind, the planar waveguides
are configured to minimize any dispersion and/or focus changes with
their planar shape factors.
[0137] In the context of discussing discretized aggregate wavefront
displays, there is value placed in having some angular diversity
created for every point in the exit pupil of the eye. In other
words, it is desirable to have multiple incoming beams to represent
each pixel in a displayed image. Referring to FIGS. 13F-1 and
13F-2, one way to gain further angular and spatial diversity is to
use a multicore fiber and place a lens at the exit point, such as a
GRIN lens, so that the exit beams are deflected through a single
nodal point (366); that nodal point may then be scanned back and
forth in a scanned fiber type of arrangement (such as by a
piezoelectric actuator 368). If a retinal conjugate is placed at
the plane defined at the end of the GRIN lens, a display may be
created that is functionally equivalent to the general case
discretized aggregate wavefront configuration described above.
[0138] Referring to FIG. 13G, a similar effect may be achieved not
by using a lens, but by scanning the face of a multicore system at
the correct conjugate of an optical system (372), the goal being to
create a higher angular and spatial diversity of beams. In other
words, rather than having a bunch of separately scanned fiber
displays as in the bundled example of FIG. 12A described above,
some of this requisite angular and spatial diversity may be created
through the use of multiple cores to create a plane which may be
relayed by a waveguide. Referring to FIG. 13H, a multicore fiber
(362) may be scanned (such as by a piezoelectric actuator 368) to
create a set of beamlets with a multiplicity of angles of incidence
and points of intersection which may be relayed to the eye (58) by
a waveguide (370). Thus in one embodiment a collimated lightfield
image may be injected into a waveguide, and without any additional
refocusing elements, that lightfield display may be translated
directly to the human eye.
[0139] FIGS. 131-13L depict certain commercially available
multicore fiber (362) configurations (from vendors such as
Mitsubishi Cable Industries, Ltd. of Japan), including one
variation (363) with a rectangular cross section, as well as
variations with flat exit faces (372) and angled exit faces
(374).
[0140] Referring to FIG. 13M, some additional angular diversity may
be created by having a waveguide (376) fed with a linear array of
displays (378), such as scanning fiber displays.
[0141] Referring to FIGS. 14A-14F, another group of configurations
for creating a fixed viewpoint lightfield display is described.
Referring back to FIG. 11A, if a two-dimensional plane was created
that was intersecting all of the tiny beams coming in from the
left, each beamlet would have a certain point of intersection with
that plane. If another plane was created at a different distance to
the left, then all of the beamlets would intersect that plane at a
different location. Then going back to FIG. 14A, if various
positions on each of two or more planes can be allowed to
selectively transmit or block the light radiation directed through
it, such a multi-planar configuration may be utilized to
selectively create a lightfield by independently modulating
individual beamlets.
[0142] The basic embodiment of FIG. 14A shows two spatial light
modulators, such as liquid crystal display panels (380, 382; in
other embodiments they may be MEMS shutter displays or DLP DMD
arrays) which may be independently controlled to block or transmit
different rays on a high-resolution basis. For example, referring
to FIG. 14A, if the second panel (382) blocks or attenuates
transmission of rays at point "a" (384), all of the depicted rays
will be blocked; but if only the first panel (380) blocks or
attenuates transmission of rays at point "b" (386), then only the
lower incoming ray (388) will be blocked/attenuated, while the rest
will be transmitted toward the pupil (45). Each of the controllable
panels or planes may be deemed a "spatial light modulator" or
"fatte". The intensity of each transmitted beam passed through a
series of SLMs will be a function of the combination of the
transparency of the various pixels in the various SLM arrays. Thus
without any sort of lens elements, a set of beamlets with a
multiplicity of angles and points of intersection (or a
"lightfield") may be created using a plurality of stacked SLMs.
Additional numbers of SLMs beyond two provides more opportunities
to control which beams are selectively attenuated.
[0143] As noted briefly above, in addition to using stacked liquid
crystal displays as SLMs, planes of DMD devices from DLP systems
may be stacked to function as SLMs, and may be preferred over
liquid crystal systems as SLMs due to their ability to more
efficiently pass light (with a mirror element in a first state,
reflectivity to the next element on the way to the eye may be quite
efficient; with a mirror element in a second state, the mirror
angle may be moved by an angle such as 12 degrees to direct the
light away from the path to the eye). Referring to FIG. 14B, in one
DMD embodiment, two DMDs (390, 390) may be utilized in series with
a pair of lenses (394, 396) in a periscope type of configuration to
maintain a high amount of transmission of light from the real world
(144) to the eye (58) of the user. The embodiment of FIG. 14C
provides six different DMD (402, 404, 406, 408, 410, 412) plane
opportunities to intercede from an SLM functionality as beams are
routed to the eye (58), along with two lenses (398, 400) for beam
control.
[0144] FIG. 14D illustrates a more complicated periscope type
arrangement with up to four DMDs (422, 424, 426, 428) for SLM
functionality and four lenses (414, 420, 416, 418); this
configuration is designed to ensure that the image does not become
flipped upside down as it travels through to the eye (58). FIG. 14E
illustrates in embodiment wherein light may be reflected between
two different DMD devices (430, 432) without any intervening lenses
(the lenses in the above designs are useful in such configurations
for incorporating image information from the real world), in a
hall-of-mirrors type of arrangement wherein the display may be
viewed through the "hall of mirrors" and operates in a mode
substantially similar to that illustrated in FIG. 14A. FIG. 14F
illustrates an embodiment wherein a the non-display portions of two
facing DMD chips (434, 436) may be covered with a reflective layer
to propagate light to and from active display regions (438, 440) of
the DMD chips. In other embodiments, in place of DMDs for SLM
functionality, arrays of sliding MEMS shutters (such as those
available from vendors such as Pixtronics, a division of Qualcomm,
Inc.) may be utilized to either pass or block light. In another
embodiment, arrays of small louvers that move out of place to
present light-transmitting apertures may similarly be aggregated
for SLM functionality.
[0145] A lightfield of many small beamlets (say, less than about
0.5 mm in diameter) may be injected into and propagated through a
waveguide or other optical system. For example, a conventional
"birdbath" type of optical system may be suitable for transferring
the light of a lightfield input, or a freeform optics design, as
described below, or any number of waveguide configurations. FIGS.
15A-15C illustrate the use of a wedge type waveguide (442) along
with a plurality of light sources as another configuration useful
in creating a lightfield. Referring to FIG. 15A, light may be
injected into the wedge-shaped waveguide (442) from two different
locations/displays (444, 446), and will emerge according to the
total internal reflection properties of the wedge-shaped waveguide
at different angles (448) based upon the points of injection into
the waveguide.
[0146] Referring to FIG. 15B, if one creates a linear array (450)
of displays (such as scanning fiber displays) projecting into the
end of the waveguide as shown, then a large angular diversity of
beams (452) will be exiting the waveguide in one dimension, as
shown in FIG. 15C. Indeed, if one contemplates adding yet another
linear array of displays injecting into the end of the waveguide
but at a slightly different angle, then an angular diversity of
beams may be created that exits similarly to the fanned out exit
pattern shown in FIG. 15C, but at an orthogonal axis; together
these may be utilized to create a two-dimensional fan of rays
exiting each location of the waveguide. Thus another configuration
is presented for creating angular diversity to form a lightfield
display using one or more scanning fiber display arrays (or
alternatively using other displays which will meet the space
requirements, such as miniaturized DLP projection
configurations).
[0147] Alternatively, as an input to the wedge-shaped waveguides
shown herein, a stack of SLM devices may be utilized, in which case
rather than the direct view of SLM output as described above, the
lightfield output from the SLM configuration may be used as an
input to a configuration such as that shown in FIG. 15C. One of the
key concepts here is that while a conventional waveguide is best
suited to relay beams of collimated light successfully, with a
lightfield of small-diameter collimated beams, conventional
waveguide technology may be utilized to further manipulate the
output of such a lightfield system as injected into the side of a
waveguide, such as a wedge-shaped waveguide, due to the beam
size/collimation.
[0148] In another related embodiment, rather than projecting with
multiple separate displays, a multicore fiber may be used to
generate a lightfield and inject it into the waveguide. Further, a
time-varying lightfield may be utilized as an input, such that
rather than creating a static distribution of beamlets coming out
of a lightfield, one may have some dynamic elements that are
methodically changing the path of the set of beams. They may be
done using components such as waveguides with embedded DOEs (e.g.,
such as those described above in reference to FIGS. 8B-8N, or
liquid crystal layers, as described in reference to FIG. 7B),
wherein two optical paths are created (one smaller total internal
reflection path wherein a liquid crystal layer is placed in a first
voltage state to have a refractive index mismatch with the other
substrate material that causes total internal reflection down just
the other substrate material's waveguide; one larger total internal
reflection optical path wherein the liquid crystal layer is placed
in a second voltage state to have a matching refractive index with
the other substrate material, so that the light totally internally
reflects through the composite waveguide which includes both the
liquid crystal portion and the other substrate portion). Similarly
a wedge-shaped waveguide may be configured to have a bi-modal total
internal reflection paradigm (for example, in one variation,
wedge-shaped elements may be configured such that when a liquid
crystal portion is activated, not only is the spacing changed, but
also the angle at which the beams are reflected).
[0149] One embodiment of a scanning light display may be
characterized simply as a scanning fiber display with a lens at the
end of the scanned fiber. Many lens varieties are suitable, such as
a GRIN lens, which may be used to collimate the light or to focus
the light down to a spot smaller than the fiber's mode field
diameter providing the advantage of producing a numerical aperture
(or "NA") increase and circumventing the optical invariant, which
is correlated inversely with spot size. Smaller spot size generally
facilitates a higher resolution opportunity from a display
perspective, which generally is preferred. In one embodiment, a
GRIN lens may be long enough relative to the fiber that it may
comprise the vibrating element (i.e., rather than the usual distal
fiber tip vibration with a scanned fiber display)--a configuration
which may be deemed a "scanned GRIN lens display".
[0150] In another embodiment, a diffractive lens may be utilized at
the exit end of a scanning fiber display (i.e., patterned onto the
fiber). In another embodiment, a curved mirror may be positioned on
the end of the fiber that operates in a reflecting configuration.
Essentially any of the configurations known to collimate and focus
a beam may be used at the end of a scanning fiber to produce a
suitable scanned light display.
[0151] Two significant utilities to having a lens coupled to or
comprising the end of a scanned fiber (i.e., as compared to
configurations wherein an uncoupled lens may be utilized to direct
light after it exits a fiber) are a) the light exiting may be
collimated to obviate the need to use other external optics to do
so; b) the NA, or the angle of the cone at which light sprays out
the end of the single-mode fiber core, may be increased, thereby
decreasing the associated spot size for the fiber and increasing
the available resolution for the display.
[0152] As described above, a lens such as a GRIN lens may be fused
to or otherwise coupled to the end of an optical fiber or formed
from a portion of the end of the fiber using techniques such as
polishing. In one embodiment, a typical optical fiber with an NA of
about 0.13 or 0.14 may have a spot size (also known as the "mode
field diameter" for the optical fiber given the NA) of about 3
microns. This provides for relatively high resolution display
possibilities given the industry standard display resolution
paradigms (for example, a typical microdisplay technology such as
LCD or organic light emitting diode, or "OLED" has a spot size of
about 5 microns). Thus the aforementioned scanning light display
may have 3/5 of the smallest pixel pitch available with a
conventional display; further, using a lens at the end of the
fiber, the aforementioned configuration may produce a spot size in
the range of 1-2 microns.
[0153] In another embodiment, rather than using a scanned
cylindrical fiber, a cantilevered portion of a waveguide (such as a
waveguide created using microfabrication processes such as masking
and etching, rather than drawn microfiber techniques) may be placed
into scanning oscillatory motion, and may be fitted with lensing at
the exit ends.
[0154] In another embodiment, an increased numerical aperture for a
fiber to be scanned may be created using a diffuser (i.e., one
configured to scatter light and create a larger NA) covering the
exit end of the fiber. In one variation, the diffuser may be
created by etching the end of the fiber to create small bits of
terrain that scatter light; in another variation a bead or
sandblasting technique, or direct sanding/scuffing technique may be
utilized to create scattering terrain. In another variation, an
engineered diffuser, similar to a diffractive element, may be
created to maintain a clean spot size with desirable NA, which ties
into the notion of using a diffractive lens, as noted above.
[0155] Referring to FIG. 16A, an array of optical fibers (454) is
shown coupled in to a coupler (456) configured to hold them in
parallel together so that their ends may be ground and polished to
have an output edge at a critical angle (458; 42 degrees for most
glass, for example) to the longitudinal axes of the input fibers,
such that the light exiting the angled faces will exit as though it
had been passing through a prism, and will bend and become nearly
parallel to the surfaces of the polished faces. The beams exiting
the fibers (454) in the bundle will become superimposed, but will
be out of phase longitudinally due to the different path lengths
(referring to FIG. 16B, for example, the difference in path lengths
from angled exit face to focusing lens for the different cores is
visible).
[0156] What was an X axis type of separation in the bundle before
exit from the angled faces, will become a Z axis separation, a fact
that is helpful in creating a multifocal light source from such a
configuration. In another embodiment, rather than using a
bundled/coupled plurality of single mode fibers, a multicore fiber,
such as those available from Mitsubishi Cable Industries, Ltd. of
Japan, may be angle polished.
[0157] In one embodiment, if a 45 degree angle is polished into a
fiber and then covered with a reflective element, such as a mirror
coating, the exiting light may be reflected from the polished
surface and emerge from the side of the fiber (in one embodiment at
a location wherein a flat-polished exit window has been created in
the side of the fiber) such that as the fiber is scanned in what
would normally be an X-Y Cartesian coordinate system axis, that
fiber would now be functionally performing the equivalent of an X-Z
scan, with the distance changing during the course of the scan.
Such a configuration may be beneficially utilized to change the
focus of the display as well.
[0158] Multicore fibers may be configured to play a role in display
resolution enhancement (i.e., higher resolution). For example, in
one embodiment, if separate pixel data is sent down a tight bundle
of 19 cores in a multicore fiber, and that cluster is scanned
around in a sparse spiral pattern with the pitch of the spiral
being approximately equal to the diameter of the multicore, then
sweeping around will effectively create a display resolution that
is approximately 19.times. the resolution of a single core fiber
being similarly scanned around. Indeed, it may be more practical to
have the fibers more sparsely positioned relative to each other, as
in the configuration of FIG. 16C, which has 7 clusters (464; 7 is
used for illustrative purposes because it is an efficient
tiling/hex pattern; other patterns or numbers may be utilized; for
example, a cluster of 19; the configuration is scalable up or down)
of 3 fibers each housed within a conduit (462).
[0159] With a sparse configuration as shown in FIG. 16C, scanning
of the multicore scans each of the cores through its own local
region, as opposed to a configuration wherein the cores are all
packed tightly together and scanned (wherein cores end up
overlapping with scanning; if the cores are too close to each
other, the NA of the core is not large enough and the very closely
packed cores end up blurring together somewhat and not creating as
discriminable a spot for display). Thus, for resolution increases,
it is preferable to have sparse tiling rather than highly dense
tiling, although both will work.
[0160] The notion that densely packed scanned cores can create
blurring at the display may be utilized as an advantage in one
embodiment wherein a plurality (say a triad or cores to carry red,
green, and blue light) of cores may be intentionally packed
together densely so that each triad forms a triad of overlapped
spots featuring red, green, and blue light. With such a
configuration, one is able to have an RGB display without having to
combine red, green, and blue into a single-mode core, which is an
advantage, because conventional mechanisms for combining a
plurality (such as three) wavelets of light into a single core are
subject to significant losses in optical energy. Referring to FIG.
16C, in one embodiment each tight cluster of 3 fiber cores contains
one core that relays red light, one core that relays green light,
and one core that relays blue light, with the 3 fiber cores close
enough together that their positional differences are not
resolvable by the subsequent relay optics, forming an effectively
superimposed RGB pixel; thus, the sparse tiling of 7 clusters
produces resolution enhancement while the tight packing of 3 cores
within the clusters facilitates seamless color blending without the
need to utilize glossy RGB fiber combiners (e.g., those using
wavelength division multiplexing or evanescent coupling
techniques).
[0161] Referring to FIG. 16D, in another more simple variation, one
may have just one cluster (464) housed in a conduit (468) for, say,
red/green/blue (and in another embodiment, another core may be
added for infrared for uses such as eye tracking). In another
embodiment, additional cores may be placed in the tight cluster to
carrying additional wavelengths of light to comprise a
multi-primary display for increased color gamut. Referring to FIG.
16E, in another embodiment, a sparse array of single cores (470);
in one variation with red, green, and blue combined down each of
them) within a conduit (466) may be utilized; such a configuration
is workable albeit somewhat less efficient for resolution increase,
but not optimum for red/green/blue combining.
[0162] Multicore fibers also may be utilized for creating
lightfield displays. Indeed, rather than keeping the cores
separated enough from each other so that the cores do not scan on
each other's local area at the display panel, as described above in
the context of creating a scanning light display, with a lightfield
display, it is desirable to scan around a densely packed plurality
of fibers because each of the beams produced represents a specific
part of the lightfield. The light exiting from the bundled fiber
tips can be relatively narrow if the fibers have a small NA;
lightfield configurations may take advantage of this and have an
arrangement in which at the anatomic pupil, a plurality of slightly
different beams are being received from the array. Thus there are
optical configurations with scanning a multicore that are
functionally equivalent to an array of single scanning fiber
modules, and thus a lightfield may be created by scanning a
multicore rather than scanning a group of single mode fibers.
[0163] In one embodiment, a multi-core phased array approach may be
used to create a large exit pupil variable wavefront configuration
to facilitate three-dimensional perception. A single laser
configuration with phase modulators is described above. In a
multicore embodiment, phase delays may be induced into different
channels of a multicore fiber, such that a single laser's light is
injected into all of the cores of the multicore configuration so
that there is mutual coherence.
[0164] In one embodiment, a multi-core fiber may be combined with a
lens, such as a GRIN lens. Such lens may be, for example, a
refractive lens, diffractive lens, or a polished edge functioning
as a lens. The lens may be a single optical surface, or may
comprise multiple optical surfaces stacked up. Indeed, in addition
to having a single lens that extends the diameter of the multicore,
a smaller lenslet array may be desirable at the exit point of light
from the cores of the multicore, for example. FIG. 16F shows an
embodiment wherein a multicore fiber (470) is emitting multiple
beams into a lens (472), such as a GRIN lens. The lens collects the
beams down to a focal point (474) in space in front of the lens. In
many conventional configurations, the beams would exit the
multicore fiber as diverging. The GRIN or other lens is configured
to function to direct them down to a single point and collimate
them, such that the collimated result may be scanned around for a
lightfield display, for instance.
[0165] Referring to FIG. 16G, smaller lenses (478) may be placed in
front of each of the cores of a multicore (476) configuration, and
these lenses may be utilized to collimate; then a shared lens (480)
may be configured to focus the collimated beams down to a
diffraction limited spot (482) that is aligned for all of the three
spots. The net result of such a configuration: by combining three
collimated, narrow beams with narrow NA together as shown, one
effectively combines all three into a much larger angle of emission
which translates to a smaller spot size in, for example, a head
mounted optical display system which may be next in the chain of
light delivery to the user.
[0166] Referring to FIG. 16H, one embodiment features a multicore
fiber (476) with a lenslet (478) array feeding the light to a small
prism array (484) that deflects the beams generated by the
individual cores to a common point. Alternatively one may have the
small lenslet array shifted relative to the cores such that the
light is being deflected and focused down to a single point. Such a
configuration may be utilized to increase the numerical
aperture.
[0167] Referring to FIG. 16I, a two-step configuration is shown
with a small lenslet (478) array capturing light from the multicore
fiber (476), followed sequentially by a shared lens (486) to focus
the beams to a single point (488). Such a configuration may be
utilized to increase the numerical aperture. As discussed above, a
larger NA corresponds to a smaller pixel size and higher possible
display resolution.
[0168] Referring to FIG. 16J, a beveled fiber array which may be
held together with a coupler (456), such as those described above,
may be scanned with a reflecting device (494; such as a DMD module
of a DLP system). With multiple single fibers (454) coupled into
the array, or a multicore instead, the superimposed light can be
directed through one or more focusing lenses (490, 492) to create a
multifocal beam; with the superimposing and angulation of the
array, the different sources are different distances from the
focusing lens, which creates different focus levels in the beams as
they emerge from the lens (492) and are directed toward the retina
(54) of the eye (58) of the user. For example, the farthest optical
route/beam may be set up to be a collimated beam representative of
optical infinity focal positions. Closer routes/beams may be
associated with diverging spherical wavefronts of closer focal
locations.
[0169] The multifocal beam may be passed into a scanning mirror
which may be configured to create a raster scan (or, for example, a
Lissajous curve scan pattern or a spiral scan pattern) of the
multifocal beam which may be passed through a series of focusing
lenses and then to the cornea and crystalline lens of the eye. The
various beams emerging from the lenses are creating different
pixels or voxels of varying focal distances that are
superimposed.
[0170] In one embodiment, one may write different data to each of
the light modulation channels at the front end, thereby creating an
image that is projected to the eye with one or more focus elements.
By changing the focal distance of the crystalline lens (i.e., by
accommodating), the user can bring different incoming pixels into
and out of focus, as shown in FIGS. 16K and 16L wherein the
crystalline lens is in different Z axis positions. In another
embodiment, the fiber array may be actuated/moved around by a
piezoelectric actuator. In another embodiment, a relatively thin
ribbon array may be resonated in cantilevered form along the axis
perpendicular to the arrangement of the array fibers (i.e., in the
thin direction of the ribbon) when a piezoelectric actuator is
activated. In one variation, a separate piezoelectric actuator may
be utilized to create a vibratory scan in the orthogonal long axis.
In another embodiment, a single mirror axis scan may be employed
for a slow scan along the long axis while the fiber ribbon is
vibrated resonantly.
[0171] Referring to FIG. 16M, an array (496) of scanning fiber
displays (498) may be beneficially bundled/tiled for an effective
resolution increase, the notion being that with such as
configuration, each scanning fiber of the bundle is configured to
write to a different portion of the image plane (500), as shown,
for example, in FIG. 16N, wherein each portion of the image plane
is addressed by the emissions from a least one bundle. In other
embodiments, optical configurations may be utilized that allow for
slight magnification of the beams as they exit the optical fiber so
that there is some overlap in the hexagonal, or other lattice
pattern, that hits the display plane, so there is a better fill
factor while also maintaining an adequately small spot size in the
image plane and understanding that there is a subtle magnification
in that image plane.
[0172] Rather than having individual lenses at the end of each
scanned fiber enclosure housing, in one embodiment a monolithic
lenslet array may be utilized, so that the lenses can be as closely
packed as possible, which allows for even smaller spot sizes in the
image plane because one may use a lower amount of magnification in
the optical system. Thus arrays of fiber scan displays may be used
to increase the resolution of the display, or in other words, they
may be used to increase the field of view of the display, because
each engine is being used to scan a different portion of the field
of view.
[0173] For a lightfield configuration, the emissions may be more
desirably overlapped at the image plane. In one embodiment, a
lightfield display may be created using a plurality of small
diameter fibers scanned around in space. For example, instead of
having all of the fibers address a different part of an image plane
as described above, have more overlapping, more fibers angled
inward, etc., or change the focal power of the lenses so that the
small spot sizes are not conjugate with a tiled image plane
configuration. Such a configuration may be used to create a
lightfield display to scan lots of smaller diameter rays around
that become intercepted in the same physical space.
[0174] Referring back to FIG. 12B, it was discussed that one way of
creating a lightfield display involves making the output of the
elements on the left collimated with narrow beams, and then making
the projecting array conjugate with the eye pupil on the right.
[0175] Referring to FIG. 16O, with a common substrate block (502),
a single actuator may be utilized to actuate a plurality of fibers
(506) in unison together. A similar configuration is discussed
above in reference to FIGS. 13-C-1 and 13-C-2. It may be
practically difficult to have all of the fibers retain the same
resonant frequency, vibrate in a desirable phase relationship to
each other, or have the same dimensions of cantilevering from the
substrate block. To address this challenge, the tips of the fibers
may be mechanically coupled with a lattice or sheet (504), such as
a graphene sheet that is very thin, rigid, and light in weight.
With such a coupling, the entire array may vibrate similarly and
have the same phase relationship. In another embodiment a matrix of
carbon nanotubes may be utilized to couple the fibers, or a piece
of very thin planar glass (such as the kind used in creating liquid
crystal display panels) may be coupled to the fiber ends. Further,
a laser or other precision cutting device may be utilized to cut
all associated fibers to the same cantilevered length.
[0176] Referring to FIG. 17, in one embodiment it may be desirable
to have a contact lens directly interfaced with the cornea, and
configured to facilitate the eye focusing on a display that is
quite close (such as the typical distance between a cornea and an
eyeglasses lens). Rather than placing an optical lens as a contact
lens, in one variation the lens may comprise a selective filter.
FIG. 17 depicts a plot (508) what may be deemed a "notch filter",
due to its design to block only certain wavelength bands, such as
450 nm (peak blue), 530 nm (green), and 650 nm, and generally pass
or transmit other wavelengths. In one embodiment several layers of
dielectric coatings may be aggregated to provide the notch
filtering functionality.
[0177] Such a filtering configuration may be coupled with a
scanning fiber display that is producing a very narrow band
illumination for red, green, and blue, and the contact lens with
the notch filtering will block out all of the light coming from the
display (such as a minidisplay, such as an OLED display, mounted in
a position normally occupied by an eyeglasses lens) except for the
transmissive wavelengths. A narrow pinhole may be created in the
middle of the contact lens filtering layers/film such that the
small aperture (i.e., less than about 1.5 mm diameter) does allow
passage of the otherwise blocked wavelengths. Thus a pinhole lens
configuration is created that functions in a pinhole manner for
red, green, and blue only to intake images from the minidisplay,
while light from the real world, which generally is broadband
illumination, will pass through the contact lens relatively
unimpeded. Thus a large depth of focus virtual display
configuration may be assembled and operated. In another embodiment,
a collimated image exiting from a waveguide would be visible at the
retina because of the pinhole large-depth-of-focus
configuration.
[0178] It may be useful to create a display that can vary its depth
of focus over time. For example, in one embodiment, a display may
be configured to have different display modes that may be selected
(preferably rapidly toggling between the two at the command of the
operator) by an operator, such as a first mode combining a very
large depth of focus with a small exit pupil diameter (i.e., so
that everything is in focus all of the time), and a second mode
featuring a larger exit pupil and a more narrow depth of focus. In
operation, if a user is to play a three-dimensional video game with
objects to be perceived at many depths of field, the operator may
select the first mode; alternatively, if a user is to type in a
long essay (i.e., for a relatively long period of time) using a
two-dimensional word processing display configuration, it may be
more desirable to switch to the second mode to have the convenience
of a larger exit pupil, and a sharper image.
[0179] In another embodiment, it may be desirable to have a
multi-depth of focus display configuration wherein some subimages
are presented with a large depth of focus while other subimages are
presented with small depth of focus. For example, one configuration
may have red wavelength and blue wavelength channels presented with
a very small exit pupil so that they are always in focus. Then, a
green channel only may be presented with a large exit pupil
configuration with multiple depth planes (i.e., because the human
accommodation system tends to preferentially target green
wavelengths for optimizing focus level). Thus, in order to cut
costs associated with having too many elements to represent with
full depth planes in red, green, and blue, the green wavelength may
be prioritized and represented with various different wavefront
levels. Red and blue may be relegated to being represented with a
more Maxwellian approach (and, as described above in reference to
Maxwellian displays, software may be utilized to induce Gaussian
levels of blur). Such a display would simultaneously present
multiple depths of focus.
[0180] As described above, there are portions of the retina which
have a higher density of light sensors. The fovea portion, for
example, generally is populated with approximately 120 cones per
visual degree. Display systems have been created in the past that
use eye or gaze tracking as an input, and to save computation
resources by only creating really high resolution rendering for
where the person is gazing at the time, while lower resolution
rendering is presented to the rest of the retina; the locations of
the high versus low resolution portions may be dynamically slaved
to the tracked gaze location in such a configuration, which may be
termed a "foveated display".
[0181] An improvement on such configurations may comprise a
scanning fiber display with pattern spacing that may be dynamically
slaved to tracked eye gaze. For example, with a typical scanning
fiber display operating in a spiral pattern, as shown in FIG. 18
(the leftmost portion 510 of the image in FIG. 18 illustrates a
spiral motion pattern of a scanned multicore fiber 514; the
rightmost portion 512 of the image in FIG. 18 illustrates a spiral
motion pattern of a scanned single fiber 516 for comparison), a
constant pattern pitch provides for a uniform display
resolution.
[0182] In a foveated display configuration, a non-uniform scanning
pitch may be utilized, with smaller/tighter pitch (and therefore
higher resolution) dynamically slaved to the detected gaze
location. For example, if the user's gaze was detected as moving
toward the edge of the display screen, the spirals may be clustered
more densely in such location, which would create a toroid-type
scanning pattern for the high-resolution portions, and the rest of
the display being in a lower-resolution mode. In a configuration
wherein gaps may be created in the portions of the display in a
lower-resolution mode, blur could be intentionally dynamically
created to smooth out the transitions between scans, as well as
between transitions from high-resolution to lower-resolution scan
pitch.
[0183] The term lightfield may be used to describe a volumetric 3-D
representation of light traveling from an object to a viewer's eye.
However, an optical see-through display can only reflect light to
the eye, not the absence of light, and ambient light from the real
world will add to any light representing a virtual object. That is,
if a virtual object presented to the eye contains a black or very
dark portion, the ambient light from the real world may pass
through that dark portion and obscure that it was intended to be
dark.
[0184] It is nonetheless desirable to be able to present a dark
virtual object over a bright real background, and for that dark
virtual object to appear to occupy a volume at a desired viewing
distance; i.e., it is useful to create a "darkfield" representation
of that dark virtual object, in which the absence of light is
perceived to be located at a particular point in space. With regard
to occlusion elements and the presentation of information to the
eye of the user so that he or she can perceive darkfield aspects of
virtual objects, even in well lighted actual environments, certain
aspects of the aforementioned spatial light modulator, or "SLM",
configurations are pertinent. As described above, with a
light-sensing system such as the eye, one way to get selective
perception of dark field to selectively attenuate light from such
portions of the display, because the subject display systems are
about manipulation and presentation of light; in other words,
darkfield cannot be specifically projected--it's the lack of
illumination that may be perceived as darkfield, and thus,
configurations for selective attenuation of illumination have been
developed.
[0185] Referring back to the discussion of SLM configurations, one
way to selectively attenuate for a darkfield perception is to block
all of the light coming from one angle, while allowing light from
other angles to be transmitted. This may be accomplished with a
plurality of SLM planes comprising elements such as liquid crystal
(which may not be the most optimal due to its relatively low
transparency when in the transmitting state), DMD elements of DLP
systems (which have relative high transmission/reflection ratios
when in such mode), and MEMS arrays or shutters that are configured
to controllably shutter or pass light radiation, as described
above.
[0186] With regard to suitable liquid crystal display ("LCD")
configurations, a cholesteric LCD array may be utilized for a
controlled occlusion/blocking array. As opposed to the conventional
LCD paradigm wherein a polarization state is changed as a function
of voltage, with a cholesteric LCD configuration, a pigment is
being bound to the liquid crystal molecule, and then the molecule
is physically tilted in response to an applied voltage. Such a
configuration may be designed to achieve greater transparency when
in a transmissive mode than conventional LCD, and a stack of
polarizing films is not needed as it is with conventional LCD.
[0187] In another embodiment, a plurality of layers of controllably
interrupted patterns may be utilized to controllably block selected
presentation of light using moire effects. For example, in one
configuration, two arrays of attenuation patterns, each of which
may comprise, for example, fine-pitched sine waves printed or
painted upon a transparent planar material such as a glass
substrate, may be presented to the eye of a user at a distance
close enough that when the viewer looks through either of the
patterns alone, the view is essentially transparent, but if the
viewer looks through both patterns lined up in sequence, the viewer
will see a spatial beat frequency moire attenuation pattern, even
when the two attenuation patterns are placed in sequence relatively
close to the eye of the user.
[0188] The beat frequency is dependent upon the pitch of the
patterns on the two attenuation planes, so in one embodiment, an
attenuation pattern for selectively blocking certain light
transmission for darkfield perception may be created using two
sequential patterns, each of which otherwise would be transparent
to the user, but which together in series create a spatial beat
frequency moire attenuation pattern selected to attenuate in
accordance with the darkfield perception desired in the augmented
reality system.
[0189] In another embodiment a controlled occlusion paradigm for
darkfield effect may be created using a multi-view display style
occluder. For example, one configuration may comprise one pin-holed
layer that fully occludes with the exception of small apertures or
pinholes, along with a selective attenuation layer in series, which
may comprise an LCD, DLP system, or other selective attenuation
layer configuration, such as those described above. In one
scenario, with the pinhole array placed at a typical eyeglasses
lens distance from the cornea (about 30 mm), and with a selective
attenuation panel located opposite the pinhole array from the eye,
a perception of a sharp mechanical edge out in space may be
created. In essence, if the configuration will allow certain angles
of light to pass, and others to be blocked or occluded, than a
perception of a very sharp pattern, such as a sharp edge
projection, may be created. In another related embodiment, the
pinhole array layer may be replaced with a second dynamic
attenuation layer to provide a somewhat similar configuration, but
with more controls than the static pinhole array layer (the static
pinhole layer could be simulated, but need not be).
[0190] In another related embodiment, the pinholes may be replaced
with cylindrical lenses. The same pattern of occlusion as in the
pinhole array layer configuration may be achieved, but with
cylindrical lenses, the array is not restricted to the very tiny
pinhole geometries. To prevent the eye from being presented with
distortions due to the lenses when viewing through to the real
world, a second lens array may be added on the side of the aperture
or lens array opposite of the side nearest the eye to compensate
and provide the view-through illumination with basically a zero
power telescope configuration.
[0191] In another embodiment, rather than physically blocking light
for occlusion and creation of darkfield perception, the light may
be bent or bounced, or a polarization of the light may be changed
if a liquid crystal layer is utilized. For example, in one
variation, each liquid crystal layer may act as a polarization
rotator such that if a patterned polarizing material is
incorporated on one face of a panel, then the polarization of
individual rays coming from the real world may be selectively
manipulated so they catch a portion of the patterned polarizer.
There are polarizers known in the art that have checkerboard
patterns wherein half of the "checker boxes" have vertical
polarization and the other half have horizontal polarization. In
addition, if a material such as liquid crystal is used in which
polarization may be selectively manipulated, light may be
selectively attenuated with this.
[0192] As described above, selective reflectors may provide greater
transmission efficiency than LCD. In one embodiment, if a lens
system is placed such that it takes light coming in from the real
world and focuses a plane from the real world onto an image plane,
and if a DMD (i.e., DLP technology) is placed at that image plane
to reflect light when in an "on" state towards another set of
lenses that pass the light to the eye, and those lenses also have
the DMD at their focal length, the one may create an attenuation
pattern that is in focus for the eye. In other words, DMDs may be
used in a selective reflector plane in a zero magnification
telescope configuration, such as is shown in FIG. 19A, to
controllably occlude and facilitate creating darkfield
perception.
[0193] As shown in FIG. 19A, a lens (518) is taking light from the
real world (144) and focusing it down to an image plane (520); if a
DMD (or other spatial attenuation device) (522) is placed at the
focal length of the lens (i.e., at the image plane 520), the lens
(518) is going to take whatever light is coming from optical
infinity and focus that onto the image plane (520). Then the
spatial attenuator (522) may be utilized to selectively block out
things that are to be attenuated. FIG. 19A shows the attenuator
DMDs in the transmissive mode wherein they pass the beams shown
crossing the device. The image is then placed at the focal length
of the second lens (524). Preferably the two lenses (518, 524) have
the same focal power so they end up being a zero-power telescope,
or a "relay", that does not magnify views to the real world (144).
Such a configuration may be used to present unmagnified views of
the world while also allowing selective blocking/attenuation of
certain pixels.
[0194] In another embodiment, as shown in FIGS. 19B and 19C,
additional DMDs may be added such that light reflects from each of
four DMDs (526, 528, 530, 532) before passing to the eye. FIG. 19B
shows an embodiment with two lenses preferably with the same focal
power (focal length "F") placed at a 2F relationship from one
another (the focal length of the first being conjugate to the focal
length of the second) to have the zero-power telescope effect; FIG.
19C shows an embodiment without lenses. The angles of orientation
of the four reflective panels (526, 528, 530, 532) in the depicted
embodiments of FIGS. 19B and 19C are shown to be around 45 degrees
for simple illustration purposes, but specific relative orientation
is required (for example, a typical DMD reflect at about a 12
degree angle).
[0195] In another embodiment, the panels may also be ferroelectric,
or may be any other kind of reflective or selective attenuator
panel or array. In one embodiment similar to those depicted in
FIGS. 19B and 19C, one of the three reflector arrays may be a
simple mirror, such that the other 3 are selective attenuators,
thus still providing three independent planes to controllably
occlude portions of the incoming illumination in furtherance of
darkfield perception. By having multiple dynamic reflective
attenuators in series, masks at different optical distances
relative to the real world may be created.
[0196] Alternatively, referring back to FIG. 19C, one may create a
configuration wherein one or more DMDs are placed in a reflective
periscope configuration without any lenses. Such a configuration
may be driven in lightfield algorithms to selectively attenuate
certain rays while others are passed.
[0197] In another embodiment, a DMD or similar matrix of
controllably movable devices may be created upon a transparent
substrate as opposed to a generally opaque substrate, for use in a
transmissive configuration such as virtual reality.
[0198] In another embodiment, two LCD panels may be utilized as
lightfield occluders. In one variation, they may be thought of as
attenuators due to their attenuating capability as described above;
alternatively they may be considered polarization rotators with a
shared polarizer stack. Suitable LCDs may comprise components such
as blue phase liquid crystal, cholesteric liquid crystal,
ferroelectric liquid crystal, and/or twisted nematic liquid
crystal.
[0199] One embodiment may comprise an array of
directionally-selective occlusion elements, such as a MEMS device
featuring a set of louvers that can change rotation such that they
pass the majority of light that is coming from a particular angle,
but are presenting more of a broad face to light that is coming
from a different angle (somewhat akin to the manner in which
plantation shutters may be utilized with a typical human scale
window). The MEMS/louvers configuration may be placed upon an
optically transparent substrate, with the louvers substantially
opaque. Ideally such a configuration would have a louver pitch fine
enough to selectably occlude light on a pixel-by-pixel basis. In
another embodiment, two or more layers or stacks of louvers may be
combined to provide yet further controls. In another embodiment,
rather than selectively blocking light, the louvers may be
polarizers configured to change the polarization state of light on
a controllably variable basis.
[0200] As described above, another embodiment for selective
occlusion may comprise an array of sliding panels in a MEMS device
such that the sliding panels may be controllably opened (i.e., by
sliding in a planar fashion from a first position to a second
position; or by rotating from a first orientation to a second
orientation; or, for example, combined rotational reorientation and
displacement) to transmit light through a small frame or aperture,
and controllably closed to occlude the frame or aperture and
prevent transmission. The array may be configured to open or
occlude the various frames or apertures such that they maximally
attenuate the rays that are to be attenuated, and only minimally
attenuate the rays to be transmitted.
[0201] In an embodiment wherein a fixed number of sliding panels
can either occupy a first position occluding a first aperture and
opening a second aperture, or a second position occluding the
second aperture and opening the first aperture, there will always
be the same amount of light transmitted overall (because 50% of the
apertures are occluded, and the other 50% are open, with such a
configuration), but the local position changes of the shutters or
doors may create targeted moire or other effects for darkfield
perception with the dynamic positioning of the various sliding
panels. In one embodiment, the sliding panels may comprise sliding
polarizers, and if placed in a stacked configuration with other
polarizing elements that are either static or dynamic, may be
utilized to selectively attenuate.
[0202] Referring to FIG. 19D, another configuration providing an
opportunity for selective reflection, such as via a DMD style
reflector array (534), is shown, such that a stacked set of two
waveguides (536, 538) along with a pair of focus elements (540,
542) and a reflector (534; such as a DMD) may be used to capture a
portion of incoming light with an entrance reflector (544). The
reflected light may be totally internally reflected down the length
of the first waveguide (536), into a focusing element (540) to
bring the light into focus on a reflector (534) such as a DMD
array, after which the DMD may selectively attenuate and reflect a
portion of the light back through a focusing lens (542; the lens
configured to facilitate injection of the light back into the
second waveguide) and into the second waveguide (538) for total
internal reflection down to an exit reflector (546) configured to
exit the light out of the waveguide and toward the eye (58).
[0203] Such a configuration may have a relatively thin shape
factor, and is designed to allow light from the real world (144) to
be selectively attenuated. As waveguides work most cleanly with
collimated light, such a configuration may be well suited for
virtual reality configurations wherein focal lengths are in the
range of optical infinity. For closer focal lengths, a lightfield
display may be used as a layer on top of the silhouette created by
the aforementioned selective attenuation/darkfield configuration to
provide other cues to the eye of the user that light is coming from
another focal distance. An occlusion mask may be out of focus, even
nondesirably so, and then in one embodiment, a lightfield on top of
the masking layer may be used to hide the fact that the darkfield
may be at the wrong focal distance.
[0204] Referring to FIG. 19E, an embodiment is shown featuring two
waveguides (552, 554) each having two angled reflectors (558, 544;
556, 546) for illustrative purposes shown at approximately 45
degrees; in actual configurations the angle may differ depending
upon the reflective surface, reflective/refractive properties of
the waveguides, etc.) directing a portion of light incoming from
the real world down each side of a first waveguide (or down two
separate waveguides if the top layer is not monolithic) such that
it hits a reflector (548, 550) at each end, such as a DMD which may
be used for selective attenuation, after which the reflected light
may be injected back into the second waveguide (or into two
separate waveguides if the bottom layer is not monolithic) and back
toward two angled reflectors (again, they need not be at 45 degrees
as shown) for exit out toward the eye (58).
[0205] Focusing lenses may also be placed between the reflectors at
each end and the waveguides. In another embodiment the reflectors
(548, 550) at each end may comprise standard mirrors (such as
alumized mirrors). Further, the reflectors may be wavelength
selective reflectors, such as dichroic mirrors or film interference
filters. Further, the reflectors may be diffractive elements
configured to reflect incoming light.
[0206] FIG. 19F illustrates a configuration wherein four reflective
surfaces in a pyramid type configuration are utilized to direct
light through two waveguides (560, 562), in which incoming light
from the real world may be divided up and reflected to four
difference axes. The pyramid-shaped reflector (564) may have more
than four facets, and may be resident within the substrate prism,
as with the reflectors of the configuration of FIG. 19E. The
configuration of FIG. 19F is an extension of that of FIG. 19E.
[0207] Referring to FIG. 19G, a single waveguide (566) may be
utilized to capture light from the world (144) with one or more
reflective surfaces (574, 576, 578, 580, 582), relay it (570) to a
selective attenuator (568; such as a DMD array), and recouple it
back into the same waveguide so that it propagates (572) and
encounters one or more other reflective surfaces (584, 586, 588,
590, 592) that cause it to at least partially exit (594) the
waveguide on a path toward the eye (58) of the user. Preferably the
waveguide comprises selective reflectors such that one group (574,
576, 578, 580, 582) may be switched on to capture incoming light
and direct it down to the selective attenuator, while separate
another group (584, 586, 588, 590, 592) may be switched on to exit
light returning from the selective attenuator out toward the eye
(58).
[0208] For simplicity the selective attenuator is shown oriented
substantially perpendicularly to the waveguide; in other
embodiments, various optics components, such as refractive or
reflective optics, may be utilized to have the selective attenuator
at a different and more compact orientation relative to the
waveguide.
[0209] Referring to FIG. 19H, a variation on the configuration
described in reference to FIG. 19D is illustrated. This
configuration is somewhat analogous to that discussed above in
reference to FIG. 5B, wherein a switchable array of reflectors may
be embedded within each of a pair of waveguides (602, 604).
Referring to FIG. 19H, a controller may be configured to turn the
reflectors (598, 600) on and off in sequence, such that multiple
reflectors may be operated on a frame sequential basis; then the
DMD or other selective attenuator (594) may also be sequentially
driven in sync with the different mirrors being turned on and
off.
[0210] Referring to FIG. 19I, a pair of wedge-shaped waveguides
similar to those described above (for example, in reference to
FIGS. 15A-15C) are shown in side or sectional view to illustrate
that the two long surfaces of each wedge-shaped waveguide (610,
612) are not co-planar. A "turning film" (606, 608; such as that
available from 3M corporation under the trade name, "TRAF", which
in essence comprises a microprism array), may be utilized on one or
more surfaces of the wedge-shaped waveguides to either turn
incoming rays at an angle so that they will be captured by total
internal reflection, or to turn outgoing rays as they are exiting
the waveguide toward an eye or other target. Incoming rays are
directed down the first wedge and toward the selective attenuator
(614) such as a DMD, LCD (such as a ferroelectric LCD), or an LCD
stack to act as a mask).
[0211] After the selective attenuator (614), reflected light is
coupled back into the second wedge-shaped waveguide which then
relays the light by total internal reflection along the wedge. The
properties of the wedge-shaped waveguide are intentionally such
that each bounce of light causes an angle change; the point at
which the angle has changed enough to be the critical angle to
escape total internal reflection becomes the exit point from the
wedge-shaped waveguide. Typically the exit will be at an oblique
angle, so another layer of turning film may be used to "turn" the
exiting light toward a targeted object such as the eye (58).
[0212] Referring to FIG. 19J, several arcuate lenslet arrays (616,
620, 622) are positioned relative to an eye and configured such
that a spatial attenuator array (618) is positioned at a
focal/image plane so that it may be in focus with the eye (58). The
first (616) and second (620) arrays are configured such that in the
aggregate, light passing from the real world to the eye is
essentially passed through a zero power telescope. The embodiment
of FIG. 19J shows a third array (622) of lenslets which may be
utilized for improved optical compensation, but the general case
does not require such a third layer. As discussed above, having
telescopic lenses that are the diameter of the viewing optic may
create an undesirably large form factor (somewhat akin to having a
bunch of small sets of binoculars in front of the eyes).
[0213] One way to optimize the overall geometry is to reduce the
diameter of the lenses by splitting them out into smaller lenslets,
as shown in FIG. 19J (i.e., an array of lenses rather than one
single large lens). The lenslet arrays (616, 620, 622) are shown
wrapped radially or arcuately around the eye (58) to ensure that
beams incoming to the pupil are aligned through the appropriate
lenslets (else the system may suffer from optical problems such as
dispersion, aliasing, and/or lack of focus). Thus all of the
lenslets are oriented "toed in" and pointed at the pupil of the eye
(58), and the system facilitates avoidance of scenarios wherein
rays are propagated through unintended sets of lenses en route to
the pupil.
[0214] Referring to FIGS. 19K-19N, various software approaches may
be utilized to assist in the presentation of darkfield in a virtual
or augmented reality displace scenario. Referring to FIG. 19K, a
typical challenging scenario for augmented reality is depicted
(632), with a textured carpet (624) and non-uniform background
architectural features (626), both of which are lightly-colored.
The black box (628) depicted indicates the region of the display in
which one or more augmented reality features are to be presented to
the user for three-dimensional perception, and in the black box a
robot creature (630) is being presented that may, for example, be
part of an augmented reality game in which the user is engaged. In
the depicted example, the robot character (630) is darkly-colored,
which makes for a challenging presentation in three-dimensional
perception, particularly with the background selected for this
example scenario.
[0215] As discussed briefly above, one of the main challenges for a
presenting darkfield augmented reality object is that the system
generally cannot add or paint in "darkness"; generally the display
is configured to add light. Thus, referring to FIG. 19L, without
any specialized software treatments to enhance darkfield
perception, presentation of the robot character in the augmented
reality view results in a scene wherein portions of the robot
character that are to be essentially flat black in presentation are
not visible, and portions of the robot character that are to have
some lighting (such as the lightly-pigmented cover of the shoulder
gun of the robot character) are only barely visible (634)--they
appear almost like a light grayscale disruption to the otherwise
normal background image.
[0216] Referring to FIG. 19M, using a software-based global
attenuation treatment (akin to digitally putting on a pair of
sunglasses) provides enhanced visibility to the robot character
because the brightness of the nearly black robot character is
effective increased relative to the rest of the space, which now
appears more dark (640). Also shown in FIG. 19M is a
digitally-added light halo (636) which may be added to enhance and
distinguish the now-more-visible robot character shapes (638) from
the background. With the halo treatment, even the portions of the
robot character that are to be presented as flat black become
visible with the contrast to the white halo, or "aura" presented
around the robot character.
[0217] Preferably the halo may be presented to the user with a
perceived focal distance that is behind the focal distance of the
robot character in three-dimensional space. In a configuration
wherein single panel occlusion techniques such as those described
above is being utilized to present darkfield, the light halo may be
presented with an intensity gradient to match the dark halo that
may accompany the occlusion, minimizing the visibility of either
darkfield effect. Further, the halo may be presented with blurring
to the background behind the presented halo illumination for
further distinguishing effect. A more subtle aura or halo effect
may be created by matching, at least in part, the color and/or
brightness of a relatively light-colored background.
[0218] Referring to FIG. 19N, some or all of the black intonations
of the robot character may be changed to dark, cool blue colors to
provide a further distinguishing effect relative to the background,
and relatively good visualization of the robot (642).
[0219] Wedge-shaped waveguides have been described above, such as
in reference to FIGS. 15A-15D and FIG. 19I. With a wedge-shaped
waveguide, every time a ray bounces off of one of the non-coplanar
surfaces, it gets an angle change, which ultimately results in the
ray exiting total internal reflection when its approach angle to
one of the surfaces goes past the critical angle. Turning films may
be used to redirect exiting light so that exiting beams leave with
a trajectory that is more or less perpendicular to the exit
surface, depending upon the geometric and ergonomic issues at
play.
[0220] With a series or array of displays injecting image
information into a wedge-shaped waveguide, as shown in FIG. 15C,
for example, the wedge-shaped waveguide may be configured to create
a fine-pitched array of angle-biased rays emerging from the wedge.
Somewhat similarly, it has been discussed above that a lightfield
display, or a variable wavefront creating waveguide, both may
produce a multiplicity of beamlets or beams to represent a single
pixel in space such that wherever the eye is positioned, the eye is
hit by a plurality of different beamlets or beams that are unique
to that particular eye position in front of the display panel.
[0221] As was further discussed above in the context of lightfield
displays, a plurality of viewing zones may be created within a
given pupil, and each may be used for a different focal distance,
with the aggregate producing a perception similar to that of a
variable wavefront creating waveguide, or similar to the actual
optical physics of reality of the objects viewed were real. Thus a
wedge-shaped waveguide with multiple displays may be utilized to
generate a lightfield. In an embodiment similar to that of FIG. 15C
with a linear array of displays injecting image information, a fan
of exiting rays is created for each pixel. This concept may be
extended in an embodiment wherein multiple linear arrays are
stacked to all inject image information into the wedge-shaped
waveguide (in one variation, one array may inject at one angle
relative to the wedge-shaped waveguide face, while the second array
may inject at a second angle relative to the wedge-shaped waveguide
face), in which case exit beams fan out at two different axes from
the wedge.
[0222] Thus such a configuration may be utilized to produce
pluralities of beams spraying out at lots of different angles, and
each beam may be driven separately due to the fact that under such
configuration, each beam is driven using a separate display. In
another embodiment, one or more arrays or displays may be
configured to inject image information into wedge-shaped waveguide
through sides or faces of the wedge-shaped waveguide other than
that shown in FIG. 15C, such as by using a diffractive optic to
bend injected image information into total an internal reflection
configuration relative to the wedge-shaped waveguide.
[0223] Various reflectors or reflecting surfaces may also be
utilized in concert with such a wedge-shaped waveguide embodiment
to outcouple and manage light from the wedge-shaped waveguide. In
one embodiment, an entrance aperture to a wedge-shaped waveguide,
or injection of image information through a different face other
than shown in FIG. 15C, may be utilized to facilitate staggering
(geometric and/or temporal) of different displays and arrays such
that a Z-axis delta may also be developed as a means for injecting
three-dimensional information into the wedge-shaped waveguide. For
a greater than three-dimensions array configuration, various
displays may be configured to enter a wedge-shaped waveguide at
multiple edges in multiple stacks with staggering to get higher
dimensional configurations.
[0224] Referring to FIG. 20A, a configuration similar to that
depicted in FIG. 8H is shown wherein a waveguide (646) has a
diffractive optical element (648; or "DOE", as noted above)
sandwiched in the middle (alternatively, as described above, the
diffractive optical element may reside on the front or back face of
the depicted waveguide). A ray may enter the waveguide (646) from
the projector or display (644). Once in the waveguide (646), each
time the ray intersects the DOE (648), part of it is exited out of
the waveguide (646). As described above, the DOE may be designed
such that the exit illuminance across the length of the waveguide
(646) is somewhat uniform (for example, the first such DOE
intersection may be configured to exit about 10% of the light; then
the second DOE intersection may be configured to exit about 10% of
the remaining light so that 81% is passed on, and so on; in another
embodied a DOE may be designed to have a variable diffraction
efficiency, such as linearly-decreasing diffraction efficiency,
along its length to map out a more uniform exit illuminance across
the length of the waveguide).
[0225] To further distribute remaining light that reaches an end
(and in one embodiment to allow for selection of a relatively low
diffraction efficiency DOE which would be favorable from a
view-to-the-world transparency perspective), a reflective element
(650) at one or both ends may be included. Further, referring to
the embodiment of FIG. 20B, additional distribution and
preservation may be achieved by including an elongate reflector
(652) across the length of the waveguide as shown (comprising, for
example, a thin film dichroic coating that is
wavelength-selective); preferably such reflector would be blocking
light that accidentally is reflected upward (back toward the real
world 144 for exit in a way that it would not be utilized by the
viewer). In some embodiments, such an elongate reflector may
contribute to a "ghosting" effect perception by the user.
[0226] In one embodiment, this ghosting effect may be eliminated by
having a dual-waveguide (646, 654) circulating reflection
configuration, such as that shown in FIG. 20C, which is designed to
keep the light moving around until it has been exited toward the
eye (58) in a preferably substantially equally distributed manner
across the length of the waveguide assembly. Referring to FIG. 20C,
light may be injected with a projector or display (644), and as it
travels across the DOE (656) of the first waveguide (654), it
ejects a preferably substantially uniform pattern of light out
toward the eye (58); light that remains in the first waveguide is
reflected by a first reflector assembly (660) into the second
waveguide (646). In one embodiment, the second waveguide (646) may
be configured to not have a DOE, such that it merely transports or
recycles the remaining light back to the first waveguide, using the
second reflector assembly.
[0227] In another embodiment (as shown in FIG. 20C) the second
waveguide (646) may also have a DOE (648) configured to uniformly
eject fractions of travelling light to provide a second plane of
focus for three-dimensional perception. Unlike the configurations
of FIGS. 20A and 20B, the configuration of FIG. 20C is designed for
light to travel the waveguide in one direction, which avoids the
aforementioned ghosting problem that is related to passing light
backwards through a waveguide with a DOE. Referring to FIG. 20D,
rather than having a mirror or box style reflector assembly (660)
at the ends of a waveguide for recycling the light, an array of
smaller retroreflectors (662), or a retroreflective material, may
be utilized.
[0228] Referring to FIG. 20E, an embodiment is shown that utilizes
some of the light recycling configurations of the embodiment of
FIG. 20C to "snake" the light down through a waveguide (646) having
a sandwiched DOE (648) after it has been injected with a display or
projector (644) so that it crosses the waveguide (646) many times
back and forth before reaching the bottom, at which point it may be
recycled back up to the top level for further recycling. Such a
configuration not only recycles the light and facilitates use of
relatively low diffraction efficiency DOE elements for exiting
light toward the eye (58), but also distributes the light, to
provide for a large exit pupil configuration akin to that described
in reference to FIG. 8K.
[0229] Referring to FIG. 20F, an illustrative configuration similar
to that of FIG. 5A is shown, with incoming light injected along a
conventional prism or beamsplitter substrate (104) to a reflector
(102) without total internal reflection (i.e., without the prism
being considered a waveguide) because the input projection (106),
scanning or otherwise, is kept within the bounds of the
prism--which means that the geometry of such prism becomes a
significant constraint. In another embodiment, a waveguide may be
utilized in place of the simple prism of FIG. 20F, which
facilitates the use of total internal reflection to provide more
geometric flexibility.
[0230] Other configurations describe above are configured to profit
from the inclusion of waveguides for similar manipulations and
light. For example, referring back to FIG. 7A, the general concept
illustrated therein is that a collimated image injected into a
waveguide may be refocused before transfer out toward an eye, in a
configuration also designed to facilitate viewing light from the
real world. In place of the refractive lens shown in FIG. 7A, a
diffractive optical element may be used as a variable focus
element.
[0231] Referring back to FIG. 7B, another waveguide configuration
is illustrated in the context of having multiple layers stacked
upon each other with controllable access toggling between a smaller
path (total internal reflection through a waveguide) and a larger
path (total internal reflection through a hybrid waveguide
comprising the original waveguide and a liquid crystal isolated
region with the liquid crystal switched to a mode wherein the
refractive indices are substantially matched between the main
waveguide and the auxiliary waveguide), so that the controller can
tune on a frame-by-frame basis which path is being taken.
High-speed switching electro-active materials, such as lithium
niobate, facilitate path changes with such a configuration at
gigahertz rates, which allows one to change the path of light on a
pixel-by-pixel basis.
[0232] Referring back to FIG. 8A, a stack of waveguides paired with
weak lenses is illustrated to demonstrate a multifocal
configuration wherein the lens and waveguide elements may be
static. Each pair of waveguide and lens may be functionally
replaced with waveguide having an embedded DOE element (which may
be static, in a closer analogy to the configuration of FIG. 8A, or
dynamic), such as that described in reference to FIG. 8I.
[0233] Referring to FIG. 20G, if a transparent prism or block (104;
i.e., not a waveguide) is utilized to hold a mirror or reflector
(102) in a periscope type of configuration to receive light from
other components, such as a lens (662) and projector or display
(644), the field of view is limited by the size of that reflector
(102; the bigger the reflector, the wider the field of view). Thus
to have a larger field of view with such configuration, a thicker
substrate may be needed to hold a larger reflector; otherwise, the
functionality of an aggregated plurality of reflectors may be
utilized to increase the functional field of view, as described in
reference to FIGS. 8O, 8P, and 8Q. Referring to FIG. 20H, a stack
(664) of planar waveguides (666), each fed with a display or
projector (644; or in another embodiment a multiplexing of a single
display) and having an exit reflector (668), may be utilized to
aggregate toward the function of a larger single reflector. The
exit reflectors may be at the same angle in some cases, or not the
same angle in other cases, depending upon the positioning of the
eye (58) relative to the assembly.
[0234] FIG. 20I illustrates a related configuration, wherein the
reflectors (680, 682, 684, 686, 688) in each of the planar
waveguides (670, 672, 674, 676, 678) have been offset from each
other, and wherein each takes in light from a projector or display
(644) which may be sent through a lens (690) to ultimately
contribute exiting light to the pupil (45) of the eye (58) by
virtue of the reflectors (680, 682, 684, 686, 688) in each of the
planar waveguides (670, 672, 674, 676, 678). If one can create a
total range of all of the angles that would be expected to be seen
in the scene (i.e., preferably without blind spots in the key field
of view), then a useful field of view has been achieved. As
described above, the eye (58) functions based at least on what
angle light rays enter the eye, and this can be simulated. The rays
need not pass through the exact same point in space at the
pupil--rather the light rays just need to get through the pupil and
be sensed by the retina. FIG. 20K illustrates a variation wherein
the shaded portion of the optical assembly may be utilized as a
compensating lens to functionally pass light from the real world
(144) through the assembly as though it has been passed through a
zero power telescope.
[0235] Referring to FIG. 20J, each of the aforementioned rays may
also be a relative wide beam that is being reflected through the
pertinent waveguide (670, 672) by total internal reflection. The
reflector (680, 682) facet size will determine what the exiting
beam width can be.
[0236] Referring to FIG. 20L, a further discretization of the
reflector is shown, wherein a plurality of small straight angular
reflectors may form a roughly parabolic reflecting surface (694) in
the aggregate through a waveguide or stack thereof (696). Light
coming in from the displays (644; or single MUXed display, for
example), such as through a lens (690), is all directed toward the
same shared focal point at the pupil (45) of the eye (58).
[0237] Referring back to FIG. 13M, a linear array of displays (378)
injects light into a shared waveguide (376). In another embodiment
a single display may be multiplexed to a series of entry lenses to
provide similar functionality as the embodiment of FIG. 13M, with
the entry lenses creating parallel paths of rays running through
the waveguide.
[0238] In a conventional waveguide approach wherein total internal
reflection is relied upon for light propagation, the field of view
is restricted because there is only a certain angular range of rays
propagating through the waveguide (others may escape out). In one
embodiment, if a red/green/blue (or "RGB") laserline reflector is
placed at one or both ends of the planar surfaces, akin to a thin
film interference filter that is highly reflective for only certain
wavelengths and poorly reflective for other wavelengths, than one
can functionally increase the range of angles of light propagation.
Windows (without the coating) may be provided for allowing light to
exit in predetermined locations. Further, the coating may be
selected to have a directional selectivity (somewhat like
reflective elements that are only highly reflective for certain
angles of incidence). Such a coating may be most relevant for the
larger planes/sides of a waveguide.
[0239] Referring back to FIG. 13E, a variation on a scanning fiber
display was discussed, which may be deemed a scanning thin
waveguide configuration, such that a plurality of very thin planar
waveguides (358) may be oscillated or vibrated such that if a
variety of injected beams is coming through with total internal
reflection, the configuration functionally would provide a linear
array of beams escaping out of the edges of the vibrating elements
(358). The depicted configuration has approximately five
externally-projecting planar waveguide portions (358) in a host
medium or substrate (356) that is transparent, but which preferably
has a different refractive index so that the light will stay in
total internal reflection within each of the substrate-bound
smaller waveguides that ultimately feed (in the depicted embodiment
there is a 90 degree turn in each path at which point a planar,
curved, or other reflector may be utilized to bounce the light
outward) the externally-projecting planar waveguide portions
(358).
[0240] The externally-projecting planar waveguide portions (358)
may be vibrated individually, or as a group along with oscillatory
motion of the substrate (356). Such scanning motion may provide
horizontal scanning, and for vertical scanning, the input (360)
aspect of the assembly (i.e., such as one or more scanning fiber
displays scanning in the vertical axis) may be utilized. Thus a
variation of the scanning fiber display is presented.
[0241] Referring back to FIG. 13H, a waveguide (370) may be
utilized to create a lightfield. With waveguides working best with
collimated beams that may be associated with optical infinity from
a perception perspective, all beams staying in focus may cause
perception discomfort (i.e., the eye will not make a discernible
difference in dioptric blur as a function of accommodation; in
other words, the narrow diameter, such as 0.5 mm or less,
collimated beamlets may open loop the eye's accommodation/vergence
system, causing discomfort).
[0242] In one embodiment, a single beam may be fed in with a number
of cone beamlets coming out, but if the introduction vector of the
entering beam is changed (i.e., laterally shift the beam injection
location for the projector/display relative to the waveguide), one
may control where the beam exits from the waveguide as it is
directed toward the eye. Thus one may use a waveguide to create a
lightfield by creating a bunch of narrow diameter collimated beams,
and such a configuration is not reliant upon a true variation in a
light wavefront to be associated with the desired perception at the
eye.
[0243] If a set of angularly and laterally diverse beamlets is
injected into a waveguide (for example, by using a multicore fiber
and driving each core separately; another configuration may utilize
a plurality of fiber scanners coming from different angles; another
configuration may utilize a high-resolution panel display with a
lenslet array on top of it), a number of exiting beamlets can be
created at different exit angles and exit locations. Since the
waveguide may scramble the lightfield, the decoding is preferably
predetermined.
[0244] Referring to FIGS. 20M and 20N, a waveguide (646) assembly
(696) is shown that comprises stacked waveguide components in the
vertical or horizontal axis. Rather than having one monolithic
planar waveguide, the notion with these embodiments is to stack a
plurality of smaller waveguides (646) immediately adjacent each
other such that light introduced into one waveguide, in addition to
propagating down (i.e., propagating along a Z axis with total
internal reflection in +X,-X) such waveguide by total internal
reflection, also totally internally reflects in the perpendicular
axis (+y, -Y) as well, such that it is not spilling into other
areas. In other words, if total internal reflection is from left to
right and back during Z axis propagation, the configuration will be
set up to totally internally reflect any light that hits the top or
bottom sides as well; each layer may be driven separately without
interference from other layers. Each waveguide may have a DOE (648)
embedded and configured to eject out light with a predetermined
distribution along the length of the waveguide, as described above,
with a predetermined focal length configuration (shown in FIG. 20M
as ranging from 0.5 meters to optical infinity).
[0245] In another variation, a very dense stack of waveguides with
embedded DOEs may be produced such that it spans the size of the
anatomical pupil of the eye (i.e., such that multiple layers 698 of
the composite waveguide are required to cross the exit pupil, as
illustrated in FIG. 20N). With such a configuration, one may feed a
collimated image for one wavelength, and then the portion located
the next millimeter down producing a diverging wavefront that
represents an object coming from a focal distance of, say, 15
meters away, and so on, with the notion being that an exit pupil is
coming from a number of different waveguides as a result of the
DOEs and total internal reflection through the waveguides and
across the DOEs. Thus rather than creating one uniform exit pupil,
such a configuration creates a plurality of stripes that, in the
aggregate, facilitate the perception of different focal depths with
the eye/brain.
[0246] Such a concept may be extended to configurations comprising
a waveguide with a switchable/controllable embedded DOE (i.e. that
is switchable to different focal distances), such as those
described in relation to FIGS. 8B-8N, which allows more efficient
light trapping in the axis across each waveguide. Multiple displays
may be coupled into each of the layers, and each waveguide with DOE
would emit rays along its own length. In another embodiment, rather
than relying on total internal reflection, a laserline reflector
may be used to increase angular range. In between layers of the
composite waveguide, a completely reflective metallized coating may
be utilized, such as aluminum, to ensure total reflection, or
alternatively dichroic style or narrow band reflectors may be
utilized.
[0247] Referring to FIG. 20O, the whole composite waveguide
assembly (696) may be curved concavely toward the eye (58) such
that each of the individual waveguides is directed toward the
pupil. In other words, the configuration may be designed to more
efficiently direct the light toward the location where the pupil is
likely to be present. Such a configuration also may be utilized to
increase the field of view.
[0248] As was discussed above in relation to FIGS. 8L, 8M, and 8N,
a changeable diffraction configuration allows for scanning in one
axis, somewhat akin to a scanning light display. FIG. 21A
illustrates a waveguide (698) having an embedded (i.e., sandwiched
within) DOE (700) with a linear grating term that may be changed to
alter the exit angle of exiting light (702) from the waveguide, as
shown. A high-frequency switching DOE material such as lithium
niobate may be utilized. In one embodiment, such a scanning
configuration may be used as the sole mechanism for scanning a beam
in one axis; in another embodiment, the scanning configuration may
be combined with other scanning axes, and may be used to create a
larger field of view (i.e., if a normal field of view is 40
degrees, and by changing the linear diffraction pitch one can steer
over another 40 degrees, the effective usable field of view for the
system is 80 degrees).
[0249] Referring to FIG. 21B, in a conventional configuration, a
waveguide (708) may be placed perpendicular to a panel display
(704), such as an LCD or OLED panel, such that beams may be
injected from the waveguide (708), through a lens (706), and into
the panel (704) in a scanning configuration to provide a viewable
display for television or other purposes. Thus the waveguide may be
utilized in such configuration as a scanning image source, in
contrast to the configurations described in reference to FIG. 21A,
wherein a single beam of light may be manipulated by a scanning
fiber or other element to sweep through different angular
locations, and in addition, another direction may be scanned using
the high-frequency diffractive optical element.
[0250] In another embodiment, a uniaxial scanning fiber display
(say scanning the fast line scan, as the scanning fiber is
relatively high frequency) may be used to inject the fast line scan
into the waveguide, and then the relatively slow DOE switching
(i.e., in the range of 100 Hz) may be used to scan lines in the
other axis to form an image.
[0251] In another embodiment, a DOE with a grating of fixed pitch
may be combined with an adjacent layer of electro-active material
having a dynamic refractive index (such as liquid crystal), so that
light may be redirected into the grating at different angles. This
is an application of the basic multipath configuration described
above in reference to FIG. 7B, in which an electro-active layer
comprising an electro-active material such as liquid crystal or
lithium niobate may change its refractive index such that it
changes the angle at which a ray emerges from the waveguide. A
linear diffraction grating may be added to the configuration of
FIG. 7B (in one embodiment, sandwiched within the glass or other
material comprising the larger lower waveguide) such that the
diffraction grating may remain at a fixed pitch, but the light is
biased before it hits the grating.
[0252] FIG. 21C shows another embodiment featuring two wedge-like
waveguide elements (710, 712), wherein one or more of them may be
electro-active so that the related refractive index may be changed.
The elements may be configured such that when the wedges have
matching refractive indices, the light totally internally reflects
through the pair (which in the aggregate performs akin to a planar
waveguide with both wedges matching) while the wedge interfaces
have no effect. Then if one of the refractive indices is changed to
create a mismatch, a beam deflection at the wedge interface (714)
is caused, and there is total internal reflection from that surface
back into the associated wedge. Then a controllable DOE (716) with
a linear grating may be coupled along one of the long edges of the
wedge to allow light to exit out and reach the eye at a desirable
exit angle.
[0253] In another embodiment, a DOE such as a Bragg grating, may be
configured to change pitch versus time, such as by a mechanical
stretching of the grating (for example, if the grating resides on
or comprises an elastic material), a moire beat pattern between two
gratings on two different planes (the gratings may be the same or
different pitches), Z-axis motion (i.e., closer to the eye, or
farther away from the eye) of the grating, which functionally is
similar in effect to stretching of the grating, or electro-active
gratings that may be switched on or off, such as one created using
a polymer dispersed liquid crystal approach wherein liquid crystal
droplets may be controllably activated to change the refractive
index to become an active grating, versus turning the voltage off
and allowing a switch back to a refractive index that matches that
of the host medium.
[0254] In another embodiment, a time-varying grating may be
utilized for field of view expansion by creating a tiled display
configuration. Further, a time-varying grating may be utilized to
address chromatic aberration (failure to focus all
colors/wavelengths at the same focal point). One property of
diffraction gratings is that they will deflect a beam as a function
of its angle of incidence and wavelength (i.e., a DOE will deflect
different wavelengths by different angles: somewhat akin to the
manner in which a simple prism will divide out a beam into its
wavelength components).
[0255] One may use time-varying grating control to compensate for
chromatic aberration in addition to field of view expansion. Thus,
for example, in a waveguide with embedded DOE type of configuration
as described above, the DOE may be configured to drive the red
wavelength to a slightly different place than the green and blue to
address unwanted chromatic aberration. The DOE may be time-varied
by having a stack of elements that switch on and off (i.e. to get
red, green, and blue to be diffracted outbound similarly).
[0256] In another embodiment, a time-varying grating may be
utilized for exit pupil expansion. For example, referring to FIG.
21D, it is possible that a waveguide (718) with embedded DOE (720)
may be positioned relative to a target pupil such that none of the
beams exiting in a baseline mode actually enter the target pupil
(45)--such that the pertinent pixel would be missed by the user. A
time-varying configuration may be utilized to fill in the gaps in
the outbound exit pattern by shifting the exit pattern laterally
(shown in dashed/dotted lines) to effectively scan each of the 5
exiting beams to better ensure that one of them hits the pupil of
the eye. In other words, the functional exit pupil of the display
system is expanded.
[0257] In another embodiment, a time-varying grating may be
utilized with a waveguide for one, two, or three axis light
scanning. In a manner akin to that described in reference to FIG.
21A, one may use a term in a grating that is scanning a beam in the
vertical axis, as well as a grating that is scanning in the
horizontal axis. Further, if radial elements of a grating are
incorporated, as is discussed above in relation to FIGS. 8B-8N, one
may have scanning of the beam in the Z axis (i.e., toward/away from
the eye), all of which may be time sequential scanning.
[0258] Notwithstanding the discussions herein regarding specialized
treatments and uses of DOEs generally in connection with
waveguides, many of these uses of DOE are usable whether or not the
DOE is embedded in a waveguide. For example, the output of a
waveguide may be separately manipulated using a DOE; or a beam may
be manipulated by a DOE before it is injected into a waveguide;
further, one or more DOEs, such as a time-varying DOE, may be
utilized as an input for freeform optics configurations, as
discussed below.
[0259] As discussed above in reference to FIGS. 8B-8N, an element
of a DOE may have a circularly-symmetric term, which may be summed
with a linear term to create a controlled exit pattern (i.e., as
described above, the same DOE that outcouples light may also focus
it). In another embodiment, the circular term of the DOE
diffraction grating may be varied such that the focus of the beams
representing those pertinent pixels is modulated. In addition, one
configuration may have a second/separate circular DOE, obviating
the need to have a linear term in the DOE.
[0260] Referring to FIG. 21E, one may have a waveguide (722)
outputting collimated light with no DOE element embedded, and a
second waveguide that has a circularly-symmetric DOE that can be
switched between multiple configurations--in one embodiment by
having a stack (724) of such DOE elements (FIG. 21F shows another
configuration wherein a functional stack 728 of DOE elements may
comprise a stack of polymer dispersed liquid crystal elements 726,
as described above, wherein without a voltage applied, a host
medium refraction index matches that of a dispersed molecules of
liquid crystal; in another embodiment, molecules of lithium niobate
may be dispersed for faster response times; with voltage applied,
such as through transparent indium tin oxide layers on either side
of the host medium, the dispersed molecules change index of
refraction and functionally form a diffraction pattern within the
host medium) that can be switched on/off.
[0261] In another embodiment, a circular DOE may be layered in
front of a waveguide for focus modulation. Referring to FIG. 21G,
the waveguide (722) is outputting collimated light, which will be
perceived as associated with a focal depth of optical infinity
unless otherwise modified. The collimated light from the waveguide
may be input into a diffractive optical element (730) which may be
used for dynamic focus modulation (i.e., one may switch on and off
different circular DOE patterns to impart various different focuses
to the exiting light). In a related embodiment, a static DOE may be
used to focus collimated light exiting from a waveguide to a single
depth of focus that may be useful for a particular user
application.
[0262] In another embodiment, multiple stacked circular DOEs may be
used for additive power and many focus levels--from a relatively
small number of switchable DOE layers. In other words, three
different DOE layers may be switched on in various combinations
relative to each other; the optical powers of the DOEs that are
switched on may be added. In one embodiment wherein a range of up
to 4 diopters is desired, for example, a first DOE may be
configured to provide half of the total diopter range desired (in
this example, 2 diopters of change in focus); a second DOE may be
configured to induce a 1 diopter change in focus; then a third DOE
may be configured to induce a 1/2 diopter change in focus. These
three DOEs may be mixed and matched to provide 1/2, 1, 1.5, 2, 2.5,
3, and 3.5 diopters of change in focus. Thus a super large number
of DOEs would not be required to get a relatively broad range of
control.
[0263] In one embodiment, a matrix of switchable DOE elements may
be utilized for scanning, field of view expansion, and/or exit
pupil expansion. Generally in the above discussions of DOEs, it has
been assume that a typical DOE is either all on or all off. In one
variation, a DOE (732) may be subdivided into a plurality of
functional subsections (such as the one labeled as element 734 in
FIG. 21H), each of which preferably is uniquely controllable to be
on or off (for example, referring to FIG. 21H, each subsection may
be operated by its own set of indium tin oxide, or other control
lead material, voltage application leads 736 back to a central
controller). Given this level of control over a DOE paradigm,
additional configurations are facilitated.
[0264] Referring to FIG. 21I, a waveguide (738) with embedded DOE
(740) is viewed from the top down, with the user's eye positioned
in front of the waveguide. A given pixel may be represented as a
beam coming into the waveguide and totally internally reflecting
along until it may be exited by a diffraction pattern to come out
of the waveguide as a set of beams. Depending upon the diffraction
configuration, the beams may come out parallel/collimated (as shown
in FIG. 21I for convenience), or in a diverging fan configuration
if representing a focal distance closer than optical infinity.
[0265] The depicted set of parallel exiting beams may represent,
for example, the farthest left pixel of what the user is seeing in
the real world as viewed through the waveguide, and light off to
the rightmost extreme will be a different group of parallel exiting
beams. Indeed, with modular control of the DOE subsections as
described above, one may spend more computing resource or time
creating and manipulating the small subset of beams that is likely
to be actively addressing the user's pupil (i.e., because the other
beams never reach the user's eye and are effectively wasted). Thus,
referring to FIG. 21J, a waveguide (738) configuration is shown
wherein only the two subsections (740, 742) of the DOE (744) are
deemed to be likely to address the user's pupil (45) are activated.
Preferably one subsection may be configured to direct light in one
direction simultaneously as another subsection is directing light
in a different direction.
[0266] FIG. 21K shows an orthogonal view of two independently
controlled subsections (734, 746) of a DOE (732). Referring to the
top view of FIG. 21L, such independent control may be used for
scanning or focusing light. In the configuration depicted in FIG.
21K, an assembly (748) of three independently controlled
DOE/waveguide subsections (750, 752, 754) may be used to scan,
increase the field of view, and/or increase the exit pupil region.
Such functionality may arise from a single waveguide with such
independently controllable DOE subsections, or a vertical stack of
these for additional complexity.
[0267] In one embodiment, if a circular DOE may be controllably
stretched radially-symmetrically, the diffraction pitch may be
modulated, and the DOE may be utilized as a tunable lens with an
analog type of control. In another embodiment, a single axis of
stretch (for example, to adjust an angle of a linear DOE term) may
be utilized for DOE control. Further, in another embodiment a
membrane, akin to a drum head, may be vibrated, with oscillatory
motion in the Z-axis (i.e., toward/away from the eye) providing
Z-axis control and focus change over time.
[0268] Referring to FIG. 21M, a stack of several DOEs (756) is
shown receiving collimated light from a waveguide (722) and
refocusing it based upon the additive powers of the activated DOEs.
Linear and/or radial terms of DOEs may be modulated over time, such
as on a frame sequential basis, to produce a variety of treatments
(such as tiled display configurations or expanded field of view)
for the light coming from the waveguide and exiting, preferably
toward the user's eye. In configurations wherein the DOE or DOEs
are embedded within the waveguide, a low diffraction efficiency is
desired to maximize transparency for light passed from the real
world; in configurations wherein the DOE or DOEs are not embedded,
a high diffraction efficiency may be desired, as described above.
In one embodiment, both linear and radial DOE terms may be combined
outside of the waveguide, in which case high diffraction efficiency
would be desired.
[0269] Referring to FIG. 21N, a segmented or parabolic reflector,
such as those discussed above in FIG. 8Q, is shown. Rather than
executing a segmented reflector by combining a plurality of smaller
reflectors, in one embodiment the same functionality may result
from a single waveguide with a DOE having different phase profiles
for each section of it, such that it is controllable by subsection.
In other words, while the entire segmented reflector functionality
may be turned on or off together, generally the DOE may be
configured to direct light toward the same region in space (i.e.,
the pupil of the user).
[0270] Referring to FIGS. 22A-22Z, optical configurations known as
"freeform optics" may be utilized certain of the aforementioned
challenges. The term "freeform" generally is used in reference to
arbitrarily curved surfaces that may be utilized in situations
wherein a spherical, parabolic, or cylindrical lens does not meet a
design complexity such as a geometric constraint. For example,
referring to FIG. 22A, one of the common challenges with display
(762) configurations when a user is looking through a mirror (and
also sometimes a lens 760) is that the field of view is limited by
the area subtended by the final lens (760) of the system.
[0271] Referring to FIG. 22B, in more simple terms, if one has a
display (762), which may include some lens elements, there is a
straightforward geometric relationship such that the field of view
cannot be larger than the angle subtended by the display (762).
Referring to FIG. 22C, this challenge is exacerbated if the user is
trying to have an augmented reality experience wherein light from
the real world is also be to passed through the optical system,
because in such case, there often is a reflector (764) that leads
to a lens (760); by interposing a reflector, the overall path
length to get to the lens from the eye is increased, which tightens
the angle and reduces the field of view.
[0272] Given this, if one wants to increase the field of view, he
must increase the size of the lens, but that might mean pushing a
physical lens toward the forehead of the user from an ergonomic
perspective. Further, the reflector may not catch all of the light
from the larger lens. Thus, there is a practical limitation imposed
by human head geometry, and it generally is a challenge to get more
than a 40-degree field of view using conventional see-through
displays and lenses.
[0273] With freeform lenses, rather than having a standard planar
reflector as described above, one has a combined reflector and lens
with power (i.e., a curved reflector 766), which means that the
curved lens geometry determines the field of view. Referring to
FIG. 22D, without the circuitous path length of a conventional
paradigm as described above in reference to FIG. 22C, it is
possible for a freeform arrangement to realize a significantly
larger field of view for a given set of optical requirements.
[0274] Referring to FIG. 22E, a typical freeform optic has three
active surfaces. Referring to FIG. 22E, in one typical freeform
optic (770) configuration, light may be directed toward the
freeform optic from an image plane, such as a flat panel display
(768), into the first active surface (772), which typically is a
primarily transmissive freeform surface that refracts transmitted
light and imparts a focal change (such as an added stigmatism,
because the final bounce from the third surface will add a
matching/opposite stigmatism and these are desirably canceled). The
incoming light may be directed from the first surface to a second
surface (774), wherein it may strike with an angle shallow enough
to cause the light to be reflected under total internal reflection
toward the third surface (776).
[0275] The third surface may comprise a half-silvered,
arbitrarily-curved surface configured to bounce the light out
through the second surface toward the eye, as shown in FIG. 22E.
Thus in the depicted typical freeform configuration, the light
enters through the first surface, bounces from the second surface,
bounces from the third surface, and is directed out of the second
surface. Due to the optimization of the second surface to have the
requisite reflective properties on the first pass, as well as
refractive properties on the second pass as the light is exited
toward the eye, a variety of curved surfaces with higher-order
shapes than a simple sphere or parabola are formed into the
freeform optic.
[0276] Referring to FIG. 22F, a compensating lens (780) may be
added to the freeform optic (770) such that the total thickness of
the optic assembly is substantially uniform in thickness, and
preferably without magnification, to light incoming from the real
world (144) in an augmented reality configuration.
[0277] Referring to FIG. 22G, a freeform optic (770) may be
combined with a waveguide (778) configured to facilitate total
internal reflection of captured light within certain constraints.
For example, as shown in FIG. 22G, light may be directed into the
freeform/waveguide assembly from an image plane, such as a flat
panel display, and totally internally reflected within the
waveguide until it hits the curved freeform surface and escapes
toward the eye of the user. Thus the light bounces several times in
total internal reflection until it reaches the freeform wedge
portion.
[0278] One of the main objectives with such an assembly is to try
to lengthen the optic assembly while retaining as uniform a
thickness as possible (to facilitate transport by total internal
reflection, and also viewing of the world through the assembly
without further compensation) for a larger field of view. FIG. 22H
depicts a configuration similar to that of FIG. 22G, with the
exception that the configuration of FIG. 22H also features a
compensating lens portion to further extend the thickness
uniformity and assist with viewing the world through the assembly
without further compensation.
[0279] Referring to FIG. 22I, in another embodiment, a freeform
optic (782) is shown with a small flat surface, or fourth face
(784), at the lower left corner that is configured to facilitate
injection of image information at a different location than is
typically used with freeform optics. The input device (786) may
comprise, for example, a scanning fiber display, which may be
designed to have a very small output geometry. The fourth face may
comprise various geometries itself and have its own refractive
power, such as by use planar or freeform surface geometries.
[0280] Referring to FIG. 22J, in practice, such a configuration may
also feature a reflective coating (788) along the first surface
such that it directs light back to the second surface, which then
bounces the light to the third surface, which directs the light out
across the second surface and to the eye (58). The addition of the
fourth small surface for injection of the image information
facilitates a more compact configuration. In an embodiment wherein
a classical freeform input configuration and a scanning fiber
display (790) are utilized, some lenses (792, 794) may be required
in order to appropriately form an image plane (796) using the
output from the scanning fiber display; these hardware components
add extra bulk that may not be desired.
[0281] Referring to FIG. 22K, an embodiment is shown wherein light
from a scanning fiber display (790) is passed through an input
optics assembly (792, 794) to an image plane (796), and then
directed across the first surface of the freeform optic (770) to a
total internal reflection bounce off of the second surface, then
another total internal reflection bounce from the third surface
results in the light exiting across the second surface and being
directed toward the eye (58).
[0282] An all-total-internal-reflection freeform waveguide may be
created such that there are no reflective coatings (i.e., such that
total-internal-reflection is being relied upon for propagation of
light until a critical angle of incidence with a surface is met, at
which point the light exits in a manner akin to the wedge-shaped
optics described above). In other words, rather than having two
planar surfaces, one may have a surface comprising one or more
sub-surfaces from a set of conical curves, such as parabolas,
spheres, ellipses, etc.).
[0283] Such a configuration still may produce a shallow-enough
angles for total internal reflection within the optic; thus an
approach that is somewhat a hybrid between a conventional freeform
optic and a wedge-shaped waveguide is presented. One motivation to
have such a configuration is to get away from the use of reflective
coatings, which do help product reflection, but also are known to
prevent transmission of a relatively large portion (such as 50%) of
the light transmitting through from the real world (144). Further,
such coatings also may block an equivalent amount of the light
coming into the freeform optic from the input device. Thus there
are reasons to develop designs that do not have reflective
coatings.
[0284] As described above, one of the surfaces of a conventional
freeform optic may comprise a half-silvered reflective surface.
Generally such a reflective surface will be of "neutral density",
meaning that it will generally reflect all wavelengths similarly.
In another embodiment, such as one wherein a scanning fiber display
is utilized as an input, the conventional reflector paradigm may be
replaced with a narrow band reflector that is wavelength sensitive,
such as a thin film laserline reflector. Thus in one embodiment, a
configuration may reflect particular red/green/blue wavelength
ranges and remain passive to other wavelengths, which generally
will increase transparency of the optic and therefore be preferred
for augmented reality configurations wherein transmission of image
information from the real world (144) across the optic also is
valued.
[0285] Referring to FIG. 22L, an embodiment is depicted wherein
multiple freeform optics (770) may be stacked in the Z axis (i.e.,
along an axis substantially aligned with the optical axis of the
eye). In one variation, each of the three depicted freeform optics
may have a wavelength-selective coating (for example, one highly
selective for blue, the next for green, the next for red) so that
images may be injected into each to have blue reflected from one
surface, green from another, and red from a third surface. Such a
configuration may be utilized, for example, to address chromatic
aberration issues, to create a lightfield, or to increase the
functional exit pupil size.
[0286] Referring to FIG. 22M, an embodiment is shown wherein a
single freeform optic (798) has multiple reflective surfaces (800,
802, 804), each of which may be wavelength or polarization
selective so that their reflective properties may be individually
controlled.
[0287] Referring to FIG. 22N, in one embodiment, multiple
microdisplays, such as scanning light displays, (786) may be
injected into a single freeform optic to tile images (thereby
providing an increased field of view), increase the functional
pupil size, or address challenges such as chromatic aberration
(i.e., by reflecting one wavelength per display). Each of the
depicted displays would inject light that would take a different
path through the freeform optic due to the different positioning of
the displays relative to the freeform optic, which would provide a
larger functional exit pupil output.
[0288] In one embodiment, a packet or bundle of scanning fiber
displays may be utilized as an input to overcome one of the
challenges in operatively coupling a scanning fiber display to a
freeform optic. One such challenge with a scanning fiber display
configuration is that the output of an individual fiber is emitted
with a certain numerical aperture, or "NA", which is like the
projectional angle of light from the fiber; ultimately this angle
determines the diameter of the beam that passes through various
optics, and ultimately determines the exit functional exit pupil
size; thus in order to maximize exit pupil size with a freeform
optic configuration, one may either increase the NA of the fiber
using optimized refractive relationships, such as between core and
cladding, or one may place a lens (i.e., a refractive lens, such as
a gradient refractive index lens, or "GRIN" lens) at the end of the
fiber or build one into the end of the fiber as described above, or
create an array of fibers that is feeding into the freeform optic,
in which case all of those NAs in the bundle remain small, and at
the exit pupil an array of small exit pupils is produced that in
the aggregate forms the functional equivalent of a large exit
pupil.
[0289] Alternatively, in another embodiment a more sparse array
(i.e., not bundled tightly as a packet) of scanning fiber displays
or other displays may be utilized to functionally increase the
field of view of the virtual image through the freeform optic.
Referring to FIG. 22O, in another embodiment, a plurality of
displays or displays (786) may be injected through the top of a
freeform optic (770), as well as another plurality (786) through
the lower corner; the display arrays may be two or three
dimensional arrays. Referring to FIG. 22P, in another related
embodiment, image information also may be injected in from the side
(806) of the freeform optic (770) as well.
[0290] In an embodiment wherein a plurality of smaller exit pupils
is to be aggregated into a functionally larger exit pupil, one may
elect to have each of the scanning fibers monochromatic, such that
within a given bundle or plurality of projectors or displays, one
may have a subgroup of solely red fibers, a subgroup of solely blue
fibers, and a subgroup of solely green fibers. Such a configuration
facilitates more efficiency in output coupling for bringing light
into the optical fibers; for instance, there would be no need in
such an embodiment to superimpose red, green, and blue into the
same band.
[0291] Referring to FIGS. 22Q-22V, various freeform optic tiling
configurations are depicted. Referring to FIG. 22Q, an embodiment
is depicted wherein two freeform optics are tiled side-by-side and
a microdisplay, such as a scanning light display, (786) on each
side is configured to inject image information from each side, such
that one freeform optic wedge represents each half of the field of
view.
[0292] Referring to FIG. 22R, a compensator lens (808) may be
included to facilitate views of the real world through the optics
assembly. FIG. 22S illustrates a configuration wherein freeform
optics wedges are tiled side by side to increase the functional
field of view while keeping the thickness of such optical assembly
relatively uniform.
[0293] Referring to FIG. 22T, a star-shaped assembly comprises a
plurality of freeform optics wedges (also shown with a plurality of
displays for inputting image information) in a configuration that
may provide a larger field of view expansion while also maintaining
a relatively thin overall optics assembly thickness.
[0294] With a tiled freeform optics assembly, the optics elements
may be aggregated to produce a larger field of view; the tiling
configurations described above have addressed this notion. For
example, in a configuration wherein two freeform waveguides are
aimed at the eye such as that depicted in FIG. 22R, there are
several ways to increase the field of view. One option is to "toe
in" the freeform waveguides such that their outputs share, or are
superimposed in, the space of the pupil (for example, the user may
see the left half of the visual field through the left freeform
waveguide, and the right half of the visual field through the right
freeform waveguide).
[0295] With such a configuration, the field of view has been
increased with the tiled freeform waveguides, but the exit pupil
has not grown in size. Alternatively, the freeform waveguides may
be oriented such that they do not toe in as much--so they create
exit pupils that are side-by-side at the eye's anatomical pupil. In
one example, the anatomical pupil may be 8 mm wide, and each of the
side-by-side exit pupils may be 8 mm, such that the functional exit
pupil is expanded by about two times. Thus such a configuration
provides an enlarged exit pupil, but if the eye is moved around in
the "eyebox" defined by that exit pupil, that eye may lose parts of
the visual field (i.e., lose either a portion of the left or right
incoming light because of the side-by-side nature of such
configuration).
[0296] In one embodiment using such an approach for tiling freeform
optics, especially in the Z-axis relative to the eye of the user,
red wavelengths may be driven through one freeform optic, green
through another, and blue through another, such red/green/blue
chromatic aberration may be addressed. Multiple freeform optics
also may be provided to such a configuration that are stacked up,
each of which is configured to address a particular wavelength.
[0297] Referring to FIG. 22U, two oppositely-oriented freeform
optics are shown stacked in the Z-axis (i.e., they are upside down
relative to each other). With such a configuration, a compensating
lens may not be required to facilitate accurate views of the world
through the assembly; in other words, rather than having a
compensating lens such as in the embodiment of FIG. 22F or FIG.
22R, an additional freeform optic may be utilized, which may
further assist in routing light to the eye. FIG. 22V shows another
similar configuration wherein the assembly of two freeform optics
is presented as a vertical stack.
[0298] To ensure that one surface is not interfering with another
surface in the freeform optics, one may use wavelength or
polarization selective reflector surfaces. For example, referring
to FIG. 22V, red, green, and blue wavelengths in the form of 650
nm, 530 nm, and 450 nm may be injected, as well as red, green, and
blue wavelengths in the form of 620 nm, 550 nm, and 470 nm;
different selective reflectors may be utilized in each of the
freeform optics so that they do not interfere with each other. In a
configuration wherein polarization filtering is used for a similar
purpose, the reflection/transmission selectivity for light that is
polarized in a particular axis may be varied (i.e., the images may
be pre-polarized before they are sent to each freeform waveguide,
to work with reflector selectivity).
[0299] Referring to FIGS. 22W and 22X, configurations are
illustrated wherein a plurality of freeform waveguides may be
utilized together in series. Referring to FIG. 22W, light may enter
from the real world and be directed sequentially through a first
freeform optic (770), through an optional lens (812) which may be
configured to relay light to a reflector (810) such as a DMD from a
DLP system, which may be configured to reflect the light that has
been filtered on a pixel by pixel basis (i.e., an occlusion mask
may be utilized to block out certain elements of the real world,
such as for darkfield perception, as described above; suitable
spatial light modulators may be used which comprise DMDs, LCDs,
ferroelectric LCOSs, MEMS shutter arrays, and the like, as
described above) to another freeform optic (770) that is relaying
light to the eye (28) of the user. Such a configuration may be more
compact than one using conventional lenses for spatial light
modulation.
[0300] Referring to FIG. 22X, in a scenario wherein it is very
important to keep overall thickness minimized, a configuration may
be utilized that has one surface that is highly-reflective so that
it may bounce light straight into another compactly positioned
freeform optic. In one embodiment a selective attenuator (814) may
be interposed between the two freeform optics (770).
[0301] Referring to FIG. 22Y, an embodiment is depicted wherein a
freeform optic (770) may comprise one aspect of a contact lens
system. A miniaturized freeform optic is shown engaged against the
cornea of a user's eye (58) with a miniaturized compensator lens
portion (780), akin to that described in reference to FIG. 22F.
Signals may be injected into the miniaturized freeform assembly
using a tethered scanning fiber display which may, for example, be
coupled between the freeform optic and a tear duct area of the
user, or between the freeform optic and another head-mounted
display configuration.
[0302] Various example embodiments of the invention are described
herein. Reference is made to these examples in a non-limiting
sense. They are provided to illustrate more broadly applicable
aspects of the invention. Various changes may be made to the
invention described and equivalents may be substituted without
departing from the true spirit and scope of the invention. In
addition, many modifications may be made to adapt a particular
situation, material, composition of matter, process, process act(s)
or step(s) to the objective(s), spirit or scope of the present
invention. Further, as will be appreciated by those with skill in
the art that each of the individual variations described and
illustrated herein has discrete components and features which may
be readily separated from or combined with the features of any of
the other several embodiments without departing from the scope or
spirit of the present inventions. All such modifications are
intended to be within the scope of claims associated with this
disclosure.
[0303] The invention includes methods that may be performed using
the subject devices. The methods may comprise the act of providing
such a suitable device. Such provision may be performed by the end
user. In other words, the "providing" act merely requires the end
user obtain, access, approach, position, set-up, activate, power-up
or otherwise act to provide the requisite device in the subject
method. Methods recited herein may be carried out in any order of
the recited events which is logically possible, as well as in the
recited order of events.
[0304] Example aspects of the invention, together with details
regarding material selection and manufacture have been set forth
above. As for other details of the present invention, these may be
appreciated in connection with the above-referenced patents and
publications as well as generally known or appreciated by those
with skill in the art. The same may hold true with respect to
method-based aspects of the invention in terms of additional acts
as commonly or logically employed.
[0305] In addition, though the invention has been described in
reference to several examples optionally incorporating various
features, the invention is not to be limited to that which is
described or indicated as contemplated with respect to each
variation of the invention. Various changes may be made to the
invention described and equivalents (whether recited herein or not
included for the sake of some brevity) may be substituted without
departing from the true spirit and scope of the invention. In
addition, where a range of values is provided, it is understood
that every intervening value, between the upper and lower limit of
that range and any other stated or intervening value in that stated
range, is encompassed within the invention.
[0306] Also, it is contemplated that any optional feature of the
inventive variations described may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Reference to a singular item, includes
the possibility that there are plural of the same items present.
More specifically, as used herein and in claims associated hereto,
the singular forms "a," "an," "said," and "the" include plural
referents unless the specifically stated otherwise. In other words,
use of the articles allow for "at least one" of the subject item in
the description above as well as claims associated with this
disclosure. It is further noted that such claims may be drafted to
exclude any optional element. As such, this statement is intended
to serve as antecedent basis for use of such exclusive terminology
as "solely," "only" and the like in connection with the recitation
of claim elements, or use of a "negative" limitation.
[0307] Without the use of such exclusive terminology, the term
"comprising" in claims associated with this disclosure shall allow
for the inclusion of any additional element--irrespective of
whether a given number of elements are enumerated in such claims,
or the addition of a feature could be regarded as transforming the
nature of an element set forth in such claims. Except as
specifically defined herein, all technical and scientific terms
used herein are to be given as broad a commonly understood meaning
as possible while maintaining claim validity.
[0308] The breadth of the present invention is not to be limited to
the examples provided and/or the subject specification, but rather
only by the scope of claim language associated with this
disclosure.
* * * * *