null  null
US008837050B2
(12) United States Patent
(10) Patent N0.:
(45) Date of Patent:
Hudman
(54)
OPTICAL WEDGE REDIRECTION
APPARATUS AND OPTICAL DEVICES USING
SAME
(56)
(*)
Notice:
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
Sep. 16, 2014
References Cited
U.S. PATENT DOCUMENTS
5,675,368 A *
(75) Inventor: Joshua M. Hudman, Issaquah, WA (US)
(73) Assignee: Microvision, Inc., Redmond, WA (US)
US 8,837,050 B2
5,801,374 A *
2009/0231719 A1*
2010/0079861 A1*
10/1997
Turner ........................ .. 347/164
9/1998 Campbell et a1. ..
9/2009
4/2010
250/2082
Powell .................... .. 359/630
Powell ........................ .. 359/449
* cited by examiner
Primary Examiner * William Choi
U.S.C. 154(b) by 338 days.
Assistant Examiner * Sharrief Broome
(21) Appl. N0.: 13/079,974
(22) Filed:
Apr. 5, 2011
(65)
Oct. 11, 2012
Int. Cl.
G023 27/10
G023 27/01
G023 5/04
G023 27/00
G023 3/00
(52)
(57)
(2006.01)
(2006.01)
(2006.01)
(2006.01)
(2006.01)
form a principal beam (953) of a received scan cone (952) to
be substantially orthogonal with an output of the exit pupil
expander (904) or major surface of the microlens array (910).
Further, the varied thickness optical element (900) can be
con?gured to cause the received scan cone (952) to exit the
US. Cl.
CPC ...... .. G023 27/0025 (2013.01); G023 27/0172
(2013.01); G023 3/0006 (2013.01); G023 5/04
(2013.01); G023 2027/015 (2013.01); G023
2027/01] (2013.01); G023 27/0081 (2013.01)
USPC
(58)
........................................................ ..
359/619
Field of Classi?cation Search
USPC
ABSTRACT
An exit pupil expander (904), operable as a numerical aper
ture expander and suitable for use with high angle of inci
dence scanned laser projection systems, includes a microlens
array (910) and a varied thickness optical element (900). The
varied thickness optical element can be con?gured to trans
Prior Publication Data
US 2012/0257282 A1
(51)
(74) Attorney, Agent, or Firm * Kevin D. Wills
varied thickness optical element (900) substantially sym
metrically about the principal beam (953). The varied thick
ness optical element (900) can also be con?gured to introduce
a controlled amount of spread to the received scan cone (952).
The varied thickness optical element (900) is useful in cor
recting distortion, such as keystone distortion introduced by
high angle of incidence feed.
................................................ .. 359/6194630
See application ?le for complete search history.
20 Claims, 11 Drawing Sheets
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Sep. 16, 2014
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US 8,837,050 B2
1
2
OPTICAL WEDGE REDIRECTION
APPARATUS AND OPTICAL DEVICES USING
SAME
associated alignment method, con?gured in accordance with
one or more embodiments of the invention.
FIG. 13 illustrates another optical redirection device con
?gured in accordance with one or more embodiments of the
invention.
FIG. 14 illustrates a single-sided optical redirection device
BACKGROUND
1. Technical Field
con?gured in accordance with one or more embodiments of
This invention relates generally to optical devices, and
the invention.
Skilled artisans will appreciate that elements in the ?gures
more particularly to optical redirection devices.
are illustrated for simplicity and clarity and have not neces
2. Background Art
Scanned laser projection devices facilitate the production
of brilliant images created with vibrant colors. Scanned sys
sarily been drawn to scale. For example, the dimensions of
some of the elements in the ?gures may be exaggerated rela
tive to other elements to help to improve understanding of
embodiments of the present invention.
tems, such as those manufactured by Microvision, Inc., are
capable of creating bright, sharp images with a large depth of
focus. Additionally, these scanned laser projection systems
DETAILED DESCRIPTION OF EMBODIMENTS
OF THE INVENTION
can be designed with compact form factors at a reasonable
cost. These systems consume small amounts of power yet
deliver vivid, complex images.
Scanned laser projection devices are frequently used in
Before describing in detail embodiments that are in accor
20
dance with the present invention, it should be observed that
the embodiments reside primarily in combinations of method
steps and apparatus components related to an optical redirec
tion device and an associated projection surface, imaging
25
components and method steps have been represented where
sophisticated projection systems such as head-up displays
and near-to-eye displays. In such applications, lasers present
information to a user, either by presenting the information on
system, and applications thereof. Accordingly, the apparatus
a projection surface or by delivering the information directly
to the user’s eye.
appropriate by conventional symbols in the drawings, show
One challenge associated with these systems is size reduc
tion. It can be desirable to make the systems smaller, so that
ing only those speci?c details that are pertinent to understand
the projection systems can be used in compact applications,
ing the embodiments of the present invention so as not to
such as with eyeglasses or goggles. However, as the optical
components become smaller, issues can arise. Distortion of
images can be introduced. Similarly, optical artifacts can
become a problem.
It would be advantageous to have a compact projection
system that does not introduce distortion into projected
images.
30
obscure the disclosure with details that will be readily appar
ent to those of ordinary skill in the art having the bene?t of the
description herein.
It will be appreciated that embodiments of the invention
described herein may be comprised of one or more conven
tional processors and unique stored program instructions that
35
control the one or more processors to implement, in conjunc
tion with certain non-processor circuits, some, most, or all of
BRIEF DESCRIPTION OF THE DRAWINGS
the functions of the systems and applications set forth below.
FIG. 1 illustrates a general block-diagram of a projection
system used with embodiments of the invention.
FIG. 2 illustrates one embodiment of a scanning engine
con?gured in accordance with embodiments of the invention.
FIG. 3 illustrates an illustrative near-to-eye application for
to, microprocessors, scanning mirrors, image spatial modu
The non-processor circuits may include, but are not limited
40
cuits, and so forth. As such, the functions and operative states
shown herein may be interpreted as steps of a method. Alter
natively, some or all functions employed by the one or more
processors to control the various elements herein, including
use with embodiments of the invention.
FIG. 4 illustrates one near-to-eye application con?gured in
accordance with embodiments of the invention.
FIG. 5 illustrates a scanning engine having a low angle of
incidence between light source and scanning engine.
45
lation element, could be implemented by a state machine that
cation speci?c integrated circuits, in which each function or
50
skill, notwithstanding possibly signi?cant effort and many
design choices motivated by, for example, available time,
dance with one or more embodiments of the invention.
FIG. 8 illustrates a projection cone associated with a high
55
FIG. 9 illustrates an optical redirection device and corre
sponding microlens array, operable as an exit pupil expander,
con?gured in accordance with embodiments of the invention.
FIG. 10 illustrates an optical redirection device con?gured
in accordance with embodiments of the invention in use with
60
FIG. 11 illustrates another embodiment of an optical redi
rection device and corresponding microlens array, and an
Referring to the drawings, like numbers indicate like parts
throughout the views. As used in the description herein and
throughout the claims, the following terms take the meanings
explicitly associated herein, unless the context clearly dic
tates otherwise: the meaning of “a ” “an,” and “the” includes
associated alignment method, con?gured in accordance with
FIG. 12 illustrates another embodiment of an optical redi
rection device and corresponding microlens array, and an
current technology, and economic considerations, when
guided by the concepts and principles disclosed herein will be
readily capable of generating such programs and circuits with
minimal experimentation.
Embodiments of the invention are now described in detail.
a high angle of incidence projection system.
one or more embodiments of the invention.
some combinations of certain of the functions are imple
mented as custom logic. Of course, a combination of the two
approaches could be used. It is expected that one of ordinary
FIG. 7 illustrates a scanned laser projection system con?g
ured with a high light-to-scanner angle of incidence in accor
angle of incidence scanned projection system.
the spatial light modulator, beam translator, and light trans
has no stored program instructions, or in one or more appli
FIG. 6 illustrates a projection cone associated with a low
angle of incidence scanned projection system.
lation devices, memory devices, clock circuits, power cir
plural reference, the meaning of “in” includes “in” and “on.”
65
Relational terms such as ?rst and second, top and bottom, and
the like may be used solely to distinguish one entity or action
from another entity or action without necessarily requiring or
US 8,837,050 B2
3
4
implying any actual such relationship or order between such
entities or actions. Also, reference designators shown herein
in parenthesis indicate components shown in a ?gure other
than the one in discussion. For example, talking about a
device (10) while discussing ?gure A would refer to an ele
able range of head or eye positions over which they are able to
receive light from the system 100. The eye focuses the light
received from the system 100 and the user 106 sees a “virtual”
image.
In one embodiment, the exit pupil expander 104 is disposed
ment, 10, shown in ?gure other than ?gure A.
FIG. 1 illustrates a block diagram generally setting forth
at an intermediate image plane of the system 100. In one
embodiment, the exit pupil expander 104 comprises an
the elements of a head-up or near-to-eye projection system
100. While embodiments of the invention described herein
ordered array of microstructures or a randomized light dif
fuser. For example, as will be described in more detail below,
in one embodiment the exit pupil expander 104 can be con
?gured as a micro lens array. The exit pupil expander 104 can
be manufactured from a molded liquid polymer, or may be
are suitable for use in any number of different applications,
for ease of discussion a near-to-eye proj ection system will be
described to illustrate the operation of the various elements.
While the elements may change in size or form, their opera
formed via other methods. The exit pupil expander 104 may
comprise single or complementary glass or plastic beads, or
microspheres or nanospheres, or similarly shaped objects
tion will generally be the same in head-up display systems.
Those of ordinary skill in the art having the bene?t of this
disclosure will readily recognize the scanning engines, beam
capable of functioning as an optical diffuser or lens. The exit
redirecting devices, and microlens arrays described below
pupil expander 104 may have optical properties resulting
may be used in any number of other applications as well.
Accordingly, the scope of the claims is not intended to be
limited by the illustrative application used for description
from a selected pitch, radius, or spacing of its constituent
20
purposes.
The system 100 includes a laser projection source 101, a
scanner 102, a control circuit 103, an exit pupil expander 104,
and relay optics 105. The system 100 uses these elements to
present information to a user 106. In a near-to-eye applica
which can comprise one or more devices, are optical transfer
25
tion, the information will be delivered directly to the user’s
eye. In a head-up display, a transparent projection surface
may be employed upon which information can be presented.
30
or an integrated multicolor laser device. In one embodiment,
optics 105 uses a combination of elements with optical power,
which may be lenses of curved re?ectors, and a transfer
medium, which may be free-space or may be a high-index
medium surrounded by a low index medium, to transfer the
image from the exit pupil expander 104 intermediate image
the laser projection source 101 includes a red laser, a blue
laser, and a green laser. These lasers can be of various types.
For example, for compact designs, semiconductor-based
lasers can be used, including edge emitting lasers or vertical
devices that direct light from a relay input to a relay output.
For example, the relay optics 105 can include a light-guiding
substrate that de?nes the optical transfer properties of the
overall relay. Regardless of application, in general the relay
While the laser projection source 101 can be a simple
monocolor laser, it can alternatively comprise multiple lasers
parts to expand incident light.
The relay optics 105 then transfer light received from the
exit pupil expander 104 to the user 106. The relay optics 105,
35
plane to the viewing space where the observer is able to see
the virtual or real image with their eyes.
In many cases, one element of the relay optics 105 is a
cavity surface emitting lasers. In other applications, larger,
combiner, which both re?ects light from the display towards
more powerful lasers can be used, alone or in combination.
Where multiple lasers are used as the laser projection source
the users eyes and transmits light from the world around so
that the users sees his normal view of the world overlaid with
101, one or more optical alignment devices (not shown in
FIG. 1) may be used to orient the plurality of light beams into
a single combined light beam. The alignment devices can
further blend the output of each laser to form a coherent,
multicolored beam of light. In one embodiment, dichroic
mirrors can be used to orient the light beams into the com
bined light beam. Dichroic mirrors are partially re?ective
information from the display. In the case of a head-up display,
40
the combiner element may be the car windshield or some
other partial re?ector. In the case of near-to-eye systems, the
combiner may be a series of partially re?ective surfaces, an
example of which is described in FIG. 4 below.
FIG. 2 illustrates a more detailed view of the scanning
mirrors that include dichroic ?lters that selectively pass light
engine 200, which includes the laser projection source 101
and the scanner 102. The illustrative scanning engine 200 of
in a narrow bandwidth while re?ecting others.
The control circuit 103, which may be a microprocessor or
ning engine. Examples of MEMS scanning light sources,
other programmable device, executes embedded instructions
to control the scanner 102, and optionally the laser projection
45
FIG. 2 is a Microelectromechanical System (MEMS) scan
50
Appln. No. 2007/0159673, entitled, “Substrate-guided Dis
play with Improved Image Quality,” which is incorporated by
source 101 as well. For example, in one embodiment the
control circuit 103 is programmed to control the scanning of
the light 108 received from the laser projection source 101 to
form a desired image on the exit pupil expander 104 for
delivery to the user 106.
reference herein.
In FIG. 4, the MEMS scanning engine 200 employs three
55
output of light sources 201,202,203 to produce a combined
modulated beam. A variable collimation or variable focusing
optical element 205 produces a variably shaped beam that is
60
across in a raster sweep pattern and delivers scanned light in
the form of a scan cone 109 to the exit pupil expander 104.
The exit pupil expander 104 serves as a “numerical aper
ture” expander that provides the user 106 with an expanded
eye box 110 within which information may be seen. The
expanded eye box 110 allows the user 106 to have a comfort
light sources 201,202,203 . A beam combiner 204, which may
employ the dichroic mirrors described above, combines the
The laser projection source 101 delivers light 107 to the
scanner 102 at an angle of incidence 108 determined by the
physical geometry of the scanner 102 relative to the light
projection source 101 (and any intermediate optical ele
ments). In one embodiment, the scanner 102 is con?gured as
a two-axis raster laser scanner capable of scanning the light
such as those suitable foruse with embodiments of the present
invention, are set forth in commonly assigned US Pub. Pat.
scanned by the MEMS scanning mirror 206 as a scanned light
cone 207. Examples of MEMS scanning mirrors, such as
those suitable for use with embodiments of the present inven
tion, are set forth in commonly assigned, copending US.
patent application Ser. No. 11/775,511, ?led Jul. 10, 2007,
65
entitled “Substrate-Guided Relays for Use with Scanned
Beam Light Sources,” which is incorporated herein by refer
ence, and in US Pub. Pat. Appln. No. 2007/0159673, refer
US 8,837,050 B2
5
6
enced above. The scanned light beam 807 can then be directed
552 is said to be substantially proportional in area because a
?rst side 681 of the scan cone 552 is substantially the same
shape and/or length as a second side 682 of the scan cone 552.
Similarly, a top side 683 of the scan cone 552 is substantially
the same shape and/or length as the bottom side 684 of the
to the buried numerical aperture expander (105).
FIG. 3 illustrates the scanning engine 200 of FIG. 2 deliv
ering light to a relay 300 and corresponding optics in a near
to-eye application. Speci?cally, the MEMS scanning engine
200 launches the scan cone 207 into the relay optics, which
include an exit pupil expander 304, a lens 305, and an input
coupler 302. The scan cone 207 ?rst arrives at the exit pupil
scan cone 552.
The scan cone 552 is also substantially symmetrical about
the principal beam 553. The principal beam 553 is substan
expander 304. The exit pupil expander 304 delivers an
tially disposed in the center of the scan cone 552, with a ?rst
half 685 of the scan cone 552 disposed to the left of the
principal beam 553 appearing to be similar in area with a
second half 686 of the scan cone 552 disposed to the right of
expanded scan cone 301 through a lens 305 to an input cou
pler 302 of the optical relay 300, which in this illustrative
embodiment is a substrate-guided relay. Light then propa
gates through the optical relay 300 in accordance with the
optical properties of the substrate to an output coupler 303. In
the principal beam 553. (Note that the halves are shown to the
left and right, but could also be shown as being de?ned above
and below the principal beam 553.)
this embodiment, the light then is redirected from one or more
partially re?ective layers 304 to the user’s eye 306.
FIG. 4 illustrates the system of FIG. 3 in operation. An
eyewear device 400 using an optical relay 300 presents infor
mation directly into than eye 401 of a user 402. The optical
relay 300 receives light from an exit pupil expander 304. A
Substantially symmetrical scan cones facilitate clear pre
sentation of information without signi?cant distortion. Tum
ing brie?y back to FIG. 5, the substantially symmetrical scan
cone 552, makes the information 550 projected on the exit
20
MEMS scanning engine 200 delivers light to the exit pupil
expander 304. The eyewear device 400 includes lens assem
blies 403 that are coupled to a frame 404. In this illustrative
embodiment, the optical relay 300 is integrated into the lens
assembly 403. In one embodiment, the eyewear device 400
and optical relay 3 00 are con?gured such that the user 402 can
see images beyond the lens assemblies 403 at the same time
25
pupil expander 705 having a combination of pincushion,
coma, and keystone distortion. This combined distortion
30
the system works well and delivers nearly distortion free
images to the user 106. Experimental testing has shown that,
in some cases, the overall size of the scanning engine can be
reduced if the angle of incidence 107 is increased. However,
testing has shown that when the angle of incidence increases
35
beyond a design threshold, which can be about fourteen or
?fteen degrees, noticeable distortion is introduced due to
asymmetry in the scan cone 109. The asymmetry results from
the large angle of incidence 107.
For example, FIG. 5 illustrates a scanning engine 500
where the angle of incidence 508 is below the design thresh
old. The laser projection source 501 delivers light 554 to the
scanner 502. The light 554 comprises a feed beam that is
delivered to the re?ective surface of the scanner. The scanning
action of the re?ective surface redirects the light 554 in a
sweep pattern to present an image 550 on the exit pupil
40
incidence scanner feed. This creates a “tilted scan object
FIG. 8 illustrates the scan cone 752 of FIG. 7 in more detail.
The scan cone 752 is said to be substantially non-proportional
45
because a ?rst side 881 of the scan cone 752 appears substan
tially different in shape and/or length relative to a second side
882 of the scan cone 752 due to the tilted scan object plane
relative to the principal beam 753. Similarly, a top side 883 of
the scan cone 752 substantially appears different in alignment
50
the scan cone 552, and represents the direction of a feed beam
re?ected from the scanner 502 when the scan mirror is at its
and direction relative to the bottom side 884 of the scan cone
7 52.
The scan cone 752 also appears as being substantially
asymmetrical. The principal beam 753 is shown in the center
central rest position. The principal beam 553 also indicates
incidence 508 that is less than the design threshold. In this
illustrative embodiment, the design threshold is about four
teen or ?fteen degrees. Accordingly, the angle of incidence
508 may be nine or ten or eleven degrees. Since the angle of
incidence 508 is below the design threshold, the scan cone
cone 752 being “tilted” about the principal beam 753. Since
the keystone distortion dominates, the result is an apparent
image shape 770 resembling a keystone of an arch
While the principal beam 753 still de?nes the general
pointing direction, the scan cone 752 disposed about the
principal beam 753 is neither substantially symmetrical nor
substantially proportional because planar surfaces are effec
tively being projected on a “tilted” plane due to high angle of
keystone distortion.
principal beam 553 generally de?nes a pointing direction of
the direction that the scan cone 552 propagates.
The light 554 is delivered to the scanner 502 at an angle of
manifests as the image 750 appearing to have a ?rst side 781
that is “pinched” relative to the other side 782 due to the scan
plane” relative to the principal beam 753, which appears as
expander 505. The sweeping action of the re?ective surface
creates the scan cone 552. A substantially center beam of the
scan cone 552 is referred to as the “principal beam” 553. The
By contrast, FIG. 7 illustrates a scanning engine 700 where
the angle of incidence 708 is above the design threshold. In
this illustrative embodiment, the angle of incidence 708 is
about twenty-seven or twenty-eight degrees, far more than the
threshold of fourteen to ?fteen degrees mentioned above.
This large angle of incidence 708 introduces asymmetry in
the scan cone 752, which results in the image 750 on the exit
the MEMS scanning engine 200 is delivering information.
Referring brie?y back to FIG. 1, in such projection sys
tems, so long as the angle of incidence 107 de?ned between
the laser projection source 101 and the scanner 102 is small,
pupil expander 505 clear and legible.
of the scan cone 752, with a ?rst half 885 of the scan cone 752
55
disposed to the left of the principal beam 753, and a second
half 886 of the scan cone 752 shown to the right of the
60
principal beam 753. In this illustrative embodiment, the ?rst
half 885 and the second half 886 appear to have substantially
different areas as viewed on the exit pupil expander 705.
Substantially asymmetrical scan cones hinder clear presen
tation of information without signi?cant distortion. Turning
552 is substantially symmetrical about the principal beam
back to FIG. 7, the high angle of incidence 708 causes a
553. Accordingly, the image 550 appears normal and is sub
stantially free from distortion.
substantially asymmetrical scan cone 752, makes the image
750 projected on the exit pupil expander 705 appear distorted.
FIG. 6 illustrates the scan cone 552 of FIG. 5 in more detail. 65 While keystone error can sometimes be corrected in the pro
As shown in FIG. 6, the scan cone 552 is substantially pro
portional in area about the principal beam 553. The scan cone
jection system, it is not always desirable due to tight tolerance
requirements and other distortion issues that can arise.
US 8,837,050 B2
8
7
One may also note that the scanning engine 700 of FIG. 7
astigmatism distortion, it does so at the intermediate image
plane of the system rather than at the point of projection.
is oriented horizontally, while the scanning engine (500) of
Accordingly, any distortion is occurring at the plane of focus,
FIG. 5 was oriented vertically. The scanning engine 700 is
shown as a horizontally fed system because experimental
testing has shown that con?guring MEMS scanners horizon
tally relative to the laser projection source allows the scanning
thereby signi?cantly reducing its impact. Accordingly,
focused spots on the exit pupil expander 904 appear tighter
than when using a conventional projection surface and a
projection level correction technique.
engine to be manufactured in a more compact form factor.
More compact form factors lend themselves better in many
The illustrative exit pupil expander 904 of FIG. 9 includes
a numerical aperture expander 905 suitable for use with relay
optics in a head-up or near-to-eye application. The numerical
aperture expander 905 includes a ?rst layer 912 and a second
layer 924, with a microlens array 910 disposed therebetween.
The microlens array 910 of FIG. 9 is a complementary micro
lens array, as it includes microlens pairs that work in tandem.
For example, microlens 920 and microlens 921 work
applications, including the near-to-eye application shown in
FIG. 4 above. However, horizontal alignment frequently
requires an angle of incidence that is greater than the design
threshold. Consequently, horizontally aligned systems fre
quently suffer from keystone distortion. It should be noted,
however, that vertically aligned systems can also suffer from
keystone distortion if the angle of incidence is beyond the
design threshold.
together, with light exiting microlens 920 and entering micro
lens 921 while passing through the exit pupil expander 904.
A varied thickness optical element 900 is disposed adjacent
Embodiments of the present invention provide a solution to
the keystone distortion introduced in high angle of incidence
systems, regardless of alignment. Embodiments of the inven
tion are particularly useful in applications where an exit pupil
20
expander and relay optics are employed. Such applications
include the virtual image head-up displays and near-to-eye
displays described above because both employ exit pupil
expanders to create a large exit pupil or “eye boxes” at the
user’s eye.
While one can somewhat correct keystone distortion by
wedge and is attached to the second layer 924 of the exit pupil
expander 904. The varied thickness optical element 900 is
con?gured to transform a principal beam 953 of a scan cone
952 received from the scanner 902 to be substantially
25
orthogonal with the output of the exit pupil expander 904. The
term “substantially” is used to refer to an angle that is gener
tilting the scanning engine relative to the exit pupil expander
(or other projection surface), this option is less than desirable.
ally orthogonal, but may not be exactly orthogonal due to
manufacturing and design tolerances associated with compo
Tilting causes the principal beam to no longer be in the center
of a displayed image. Additionally, the direction of propaga
to microlens array 910. In the illustrative embodiment of FIG.
9, the varied thickness optical element 900 is con?gured as a
30
nents and the overall system.
Recall from above that the scanner 902 in a high angle of
tion of the scan cone is no longer orthogonal to the exit pupil
incidence system creates a scan cone 952 that is asymmetri
expander. This greatly complicates the relay optics. Said dif
ferently, the design of relay optics can be greatly simpli?ed
cally oriented about the principal beam 1053. Additionally, in
the illustrative embodiment of FIG. 9, the scanner 902 is
when the direction of propagation is normal to the exit pupil
task: redirection of a scan cone from a high angle of incidence
oriented in a non-orthogonal relationship with the microlens
array 910. Accordingly, the varied thickness optical element
900 is con?gured to do two things: First, it steers the received
scanning engine such that the scan cone is symmetrical about
the principal beam and travels in a direction substantially
normal to the exit pupil expander.
microlens array 910 at an angle that is substantially orthogo
nal with the ?rst layer 912 and the second layer 924. Second,
expander. Embodiments described below accomplish this
Turning now to FIG. 9, illustrated therein is an alternate
35
scan cone 952 such that the principal beam 953 enters the
40
exit pupil expander 904 suitable for use with high angle of
952 exits the varied thickness optical element substantially
symmetrically about the principal beam 953. This is shown
incidence laser projection sources in accordance with one or
more embodiments of the invention. “High angle of inci
dence” refers to systems where the angle of incidence
between scanner 902 and light projection source 901 is
greater than the design threshold.
The exit pupil expander 904 of FIG. 9 corrects for keystone
distortion in high angle of incidence scanned laser systems
without the problems associated with correction techniques
applied at the projector level. For example, systems employ
ing the exit pupil expander 904 can be manufactured less
expensively than systems correcting keystone distortion at
the projector level. Additionally, the tolerances associated
with the manufacture of the exit pupil expander 904 are not as
tight as those associated with projector level correction sys
45
display, near-to-eye display, and other optical systems, down
50
55
Anytime keystone error is corrected, astigmatism distor
corrected in the projection system, the astigmatism distortion
60
limits. The exit pupil expander 904 of FIG. 9 prevents this
problem because any astigmatism that is generated does not
have an opportunity to cause beam growth at the exit pupil
pupil expander 904 of FIG. 9 may introduce some minor
stream components such as relay optics look to receive beams
having a predetermined amount of spread. In one embodi
ment, the relay optics are con?gured to perform more opti
mally when the received light has a predetermined spread
associated therewith. For example, in some systems, relay
tion can be introduced. In prior art systems, where keystone is
expander 904. Some growth may occur beyond the exit pupil
expander 904, but this is generally inconsequential in a head
up or near-to-eye application. Said differently, while the exit
illustratively in FIG. 9 with a ?rst half 985 of the output cone
928 having substantially the same area as a second half 986 of
the output cone 928.
In one embodiment, the varied thickness optical element
900 is con?gured to perform a third task. In certain head-up
tems.
causes the beam spot resolution to grow beyond desirable
it steers the remaining beams such that the received scan cone
optics are con?gured to perform better when the output cone
928 is an output expansion cone having a predetermined
spread of between ten and ?fteen degrees. Accordingly, in one
embodiment the varied thickness optical element 900 is fur
ther con?gured to cause beams 922,923 of the received scan
cone 952 to exit the varied thickness optical element 1000
with a predetermined spread relative to the principal beam
953.
In the illustrative embodiment of FIG. 9, the microlens
elements are arranged in accordance with the predetermined
spread. For example, microlens element 920 and microlens
65
element 921 are arranged with a pitch that corresponds to the
predetermined spread. (Note that the lens elements through
which the principal beam 953 passes have no pitch associated
US 8,837,050 B2
9
10
therewith. However, in one embodiment all other lens ele
ments are arranged with pitch.)
The exit pupil expander 904 of FIG. 9 is well suited for use
(910) and the ?rst layer (912), while the second half may
include the remainder of the microlens array (910), the sec
ond layer (924), and the varied thickness optical element
(900). To make alignment easier, in one embodiment these
in head-up and near-to-eye displays. As noted above, relay
optics are simpli?ed when the received scan cone is substan
halves can be con?gured with alignment indicators. FIGS. 11
and 12 illustrate two examples of alignment indicators suit
tially symmetrical about the principal beam. Further, as
described in the preceding paragraph, head-up optics often
able for use with one or more embodiments of the invention.
perform better when the received scan cone includes a pre
In FIG. 11, the projection surface 1104 employs mechani
cal engagement devices 1110,1111 as alignment indicators.
The projection surface 1104 of FIG. 11 comprises two halves.
determined amount of spread. By varying the thickness of the
varied thickness optical element across the width of the ele
ment, i.e., by varying the thickness of the wedge in this
A ?rst half includes a ?rst substrate 1112. The ?rst substrate
1112 has a ?rst set 1114 of microlenses either disposed
thereon or integrated therewith. The second half includes a
embodiment, a designer can optimize the varied thickness
optical element for a particular system geometry and a par
ticular amount of keystone distortion introduced by the high
angle of incidence scanning engine. Thus, in a scanned laser
second substrate 1124 and the varied thickness optical ele
ment 1100, which is integrated with the second substrate
projection system employing the exit pupil expander 904 of
1124 in this illustrative embodiment. A second set 1123 of
microlenses is either disposed on or integrated with the sec
ond substrate 1124.
FIG. 9, the varied thickness optical element 900 not only
effectively eliminates keystone distortion, but also prepares
the output expansion cone 928 to optimize the performance of
subsequent optical components in a system.
The exit pupil expander 904 of FIG. 9 can be manufactured
from a variety of materials. Additionally, the numerical aper
20
To make alignment of the two halves easier during manu
facture, the ?rst half includes a ?rst mechanical engagement
device 1110, while the second half includes a second
mechanical engagement device 1111. In this illustrative
embodiment, the ?rst mechanical engagement device 1110 is
25
a male engagement device mounted on a ?ange 1116 extend
ture expander 905 can be manufactured from a variety of
materials. Illustrative materials include glass and plastic. In
one embodiment, the numerical aperture expander 905 and
varied thickness optical element 900 are manufactured from
the same material. In another embodiment, they are manufac
tured from different materials. The varied thickness optical
element 900 can be attached to the numerical aperture
expander 1005, or alternatively may be integrated into one of
30
the ?rst layer 912 or second layer 924. For example, where
both the varied thickness optical element 900 and numerical
aperture expander 905 are both manufactured from glass,
they can be attached to each other using conventional glass
bonding techniques or by using an optical adhesive.
ing from the ?rst substrate 1112. The second mechanical
engagement device 1111 is a female engagement device
mounted on another ?ange 1115 extending from the second
substrate 1124. The male and female engagement devices can
be nestled to make alignment of the ?rst half and second half
easier.
Turning to FIG. 12, illustrated therein is an alternate align
35
In one embodiment, to simplify manufacture and reduce
ment indicator. In FIG. 12, each half 1201,1202 of the pro
jection surface includes an indicator 1203,1204 that is con
?gured to be read by a machine vision alignment device 1205.
In the illustrative embodiment of FIG. 12, the indicators 1203,
cost, the varied thickness optical element 900 is integrated
1204 are con?gured as small plus or cross marks that are
with one of the ?rst layer 912 or second layer 924 of the
either etched or tooled into each half 1201,1202. During
manufacture, the machine vision alignment device 1205 takes
visual pictures of the halves 1201,1202 as they are moved
relative to each other. When the indicators 1203,1204 coin
numerical aperture expander 905. For instance, a portion of
the microlens array 910, the second layer 924, and the varied
40
thickness optical element can be manufactured as an inte
grated plastic assembly by way of an injection molding pro
cide, such that the picture seen by the machine vision align
cess. This assembly can then be aligned with the remaining
portion of the microlens array 910 and ?rst layer 912 to
ment device 1205 appears as a single indicator, the two halves
complete the assembly. Another advantage of using plastic
1201,1202 are aligned. Accordingly, they can then be bonded
45
To this point, embodiments of the varied thickness optical
element have been exclusively shown as wedges. However, it
will be clear to those of ordinary skill in the art having the
bene?t of this disclosure that embodiments of the varied
and injection molding for the components is that it is easier to
achieve the necessary tolerances used to de?ne the function of
the varied thickness optical element 900.
By placing the varied thickness optical element 900 adja
cent to the microlens array 910, the varied thickness optical
50
element 900 is disposed essentially at the intermediate image
plane of the overall system shown in FIG. 9. Thus, when the
scan cone 952 is presenting pixilated information along the
projection surface, the effect applied by the varied thickness
optical element 900 is applied “spot by spot.” This is another
55
advantage of the exit pupil expander 904 of FIG. 9 over
projector level keystone distortion correction where correc
tion is applied while each beam is going in a different direc
tion and traversing a large portion of the correction device.
The result of using the exit pupil expander 904 of FIG. 9 is
60
shown in FIG. 10, where information 1008 delivered from a
high angle of incidence scanning engine 1000 no longer suf
fers from keystone distortion. Instead, the information 1008 is
clear and legible for delivery to subsequent relay optics.
In one embodiment the projection surface (904) of FIG. 9
is manufactured from two halves that must be aligned during
assembly. A ?rst half may include half of the microlens array
together as described above with reference to FIGS. 2 and 3.
65
thickness optical element are not so limited. Turning now to
FIG. 13, illustrated therein is just one of the many possible
variants that can be constructed without departing from the
spirit and scope of the invention.
As shown in FIG. 13, the varied thickness optical element
1304 is a varied thickness device, in that its thickness varies
across its width. However, the varied thickness optical ele
ment 1304 of FIG. 13 is not con?gured as a wedge. Instead,
the varied thickness optical element 1304 has a major face
1301 that is non-linear. In this illustrative embodiment, the
major face is shown as a convex surface. However, it will be
clear to those of ordinary skill in the art having the bene?t of
this disclosure that other shapes and contours can be applied
to achieve different results in the output cone 1328. For
example, one application may call for a telecentric output
cone 1328. By varying the contour of the major face 1301 of
the varied thickness optical element, this effectior other
effects4can be easily achieved.
US 8,837,050 B2
11
12
It should also be noted that the “expander” portion of
embodiments of the invention need not be complementary.
For example, the microlens array (910) of FIG. 9 included
two halves.As shown in FIG. 14, the “expander” can be single
sided as well. For example, the exit pupil expander surface
set of microlenses disposed along the ?rst substrate and a
second set of microlenses disposed along the second sub
strate.
10. The optical device of claim 8, wherein a ?rst alignment
indicator of the ?rst substrate comprises a ?rst mechanical
engagement device, and a second alignment indicator of the
second substrate comprises a second mechanical engagement
device.
1401 can be either an optical diffuser or single sided micro
lens array, either of which is single sided.
In the foregoing speci?cation, speci?c embodiments of the
11. The optical device of claim 8, wherein the alignment
present invention have been described. However, one of ordi
nary skill in the art appreciates that various modi?cations and
changes can be made without departing from the scope of the
present invention as set forth in the claims below. Thus, while
preferred embodiments of the invention have been illustrated
and described, it is clear that the invention is not so limited.
indicator is con?gured to be readable by a machine vision
alignment device.
12. The optical device of claim 8, wherein the varied thick
ness optical element is integrated with one of the ?rst sub
strate or the second substrate.
13. The optical device of claim 1, wherein the exit pupil
expander comprises a diffuser disposed at intermediate image
plane of the optical device.
14. A scanned laser projection system, comprising:
Numerous modi?cations, changes, variations, substitutions,
and equivalents will occur to those skilled in the art without
departing from the spirit and scope of the present invention as
de?ned by the following claims. Accordingly, the speci?ca
tion and ?gures are to be regarded in an illustrative rather than
a restrictive sense, and all such modi?cations are intended to 20
be included within the scope of present invention. The ben
a numerical aperture expander comprising a microlens
array;
a laser scanning engine con?gured to scan light in a raster
e?ts, advantages, solutions to problems, and any element(s)
sweep pattern to form a scan cone, with a traveling
that may cause any bene?t, advantage, or solution to occur or
become more pronounced are not to be construed as a critical,
required, or essential features or elements of any or all the 25
direction of the scan cone being de?ned by a principal
laser scanning engine and the numerical aperture
claims.
What is claimed is:
expander;
wherein the varied thickness optical element is con?gured
1. An optical device, comprising:
an exit pupil expander; and
a varied thickness optical element coupled to an input of
to redirect the scan cone prior to entering the numerical
30
the exit pupil expander, the varied thickness optical ele
ment con?gured to receive a scan cone, and to transform
wherein the varied thickness optical element is further con
exit pupil expander to be substantially orthogonal with
35
beam.
16. The scanned laser projection system of claim 14,
wherein the varied thickness optical element is further con
substantially symmetrically about the principal beam.
3. The optical device of claim 2, wherein the varied thick
ness optical element comprises an optical wedge.
4. The optical device of claim 2, wherein a major face of the
varied thickness optical element is non-linear.
5. The optical device of claim 2, wherein the varied thick
40
ness optical element is further con?gured to cause beams of
the received scan cone to exit the varied thickness optical
45
spread.
17. The scanned laser projection system of claim 14,
wherein the varied thickness optical element is one of dis
expander.
substrate having at least one alignment device and a second
50
substrate having at least another alignment device, wherein
the ?rst substrate and the second substrate are by the at least
one alignment device and the at least another alignment
device.
55
8. The optical device of claim 6, wherein the microlens
19. The scanned laser projection system of claim 14,
wherein the laser scanning engine comprises MEMS scan
ning engine fed at an angle of incidence greater than a design
threshold.
array comprises a ?rst substrate and a second substrate,
wherein each of the ?rst substrate and the second substrate
array comprises a complementary microlens array, with a ?rst
posed adjacent to or integrated with the numerical aperture
18. The scanned laser projection system of claim 14,
wherein the numerical aperture expander comprises a ?rst
microlens array are arranged in accordance with a predeter
comprises an alignment indicator.
9. The optical device of claim 8, wherein the microlens
?gured to cause the scan cone to enter the numerical aperture
expander with substantially a predetermined amount of
element with a predetermined spread relative to the principal
beam.
mined spread.
?gured to cause the scan cone to enter the numerical aperture
expander substantially symmetrically about the principal
ness optical element is further con?gured to cause the
received scan cone to exit the varied thickness optical element
6. The optical device of claim 1, wherein the exit pupil
expander comprises a microlens array.
7. The optical device of claim 6, wherein the microlens
array comprises a complementary microlens array, wherein
complementary microlens elements of the complementary
aperture expander such that the principal beam, when
entering the microlens array, is substantially orthogonal
with an output of the numerical aperture expander.
15. The scanned laser projection system of claim 14,
a principal beam of the scan cone prior to entering the
an output of the exit pupil expander.
2. The optical device of claim 1, wherein the varied thick
beam; and
a varied thickness optical element disposed between the
60
20. The scanned laser projection system of claim 14,
wherein the scanned laser proj ection system comprises one of
a near-to-eye or head-up display.
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