U.S. patent application number 15/077386 was filed with the patent office on 2016-07-14 for tunable electro-optic liquid crystal lenses and methods for forming the lenses.
The applicant listed for this patent is KENT STATE UNIVERSITY. Invention is credited to Philip Bos, Douglas Bryant, Lei Shi, Bentley Wall.
Application Number | 20160202573 15/077386 |
Document ID | / |
Family ID | 43356671 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160202573 |
Kind Code |
A1 |
Bos; Philip ; et
al. |
July 14, 2016 |
TUNABLE ELECTRO-OPTIC LIQUID CRYSTAL LENSES AND METHODS FOR FORMING
THE LENSES
Abstract
Electro-optic lenses, including liquid crystals, wherein the
power of the lenses can be modified by application of an electric
field. In one embodiment, the liquid crystal-based lenses include
ring electrodes having a resistive bridge located between adjacent
electrodes, and in a preferred embodiment, input connections for
several electrode rings are spaced on the lens. In a further
embodiment, liquid crystal-based lenses are provided that can
increase optical power through the use of phase resets, wherein in
one embodiment, a lens includes ring electrodes on surfaces of the
substrates on opposite sides of the liquid crystal cell such that a
fixed phase term can be added to each set of electrodes that allows
for phase change across each group of electrodes to be the same and
also be matched with respect to a previous group.
Inventors: |
Bos; Philip; (Hudson,
OH) ; Bryant; Douglas; (Aurora, OH) ; Shi;
Lei; (Wexford, PA) ; Wall; Bentley; (Kent,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KENT STATE UNIVERSITY |
Kent |
OH |
US |
|
|
Family ID: |
43356671 |
Appl. No.: |
15/077386 |
Filed: |
March 22, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13900834 |
May 23, 2013 |
9323113 |
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15077386 |
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12802943 |
Jun 17, 2010 |
9280020 |
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13900834 |
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61269110 |
Jun 19, 2009 |
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Current U.S.
Class: |
349/139 |
Current CPC
Class: |
G02F 2001/294 20130101;
G02F 1/134309 20130101; G02F 1/1345 20130101; G02B 3/14 20130101;
G02F 1/29 20130101 |
International
Class: |
G02F 1/1343 20060101
G02F001/1343 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] The U.S. Government has a paid-up license in the inventions
and the right, in limited circumstances, to require the patent
owner to license others on reasonable terms as provided for by
terms of contract number FA 7014-07-C-0013 awarded by the U.S. Air
Force.
Claims
1. An electro-optic lens device comprising: a first substantially
transparent substrate comprising a first substantially transparent
conductive electrode layer operatively connected thereto, the first
electrode layer being patterned and comprising a first plurality of
ring electrodes that form a first resistive divider network,
wherein at least one ring electrode from the first plurality of
ring electrodes is electrically connected to an adjacent ring
electrode from the first plurality of ring electrodes by a first
resistive bridge that electrically bridges a substantially annular
insulating gap that is substantially co-planar with the first
resistive bridge, the first resistive bridge comprising a resistive
path across the insulating gap, the resistive path comprising an
electrically conductive material bordered by a non-conductive
material or an area free from conductive material, each ring
electrode from the first plurality of ring electrodes defining a
corresponding continuous ring; a second substantially transparent
substrate comprising a second substantially transparent conductive
electrode layer operatively connected thereto; and an electroactive
liquid crystal material layer present between the first
substantially transparent substrate and the second substantially
transparent substrate; wherein: a first sub-plurality of continuous
ring electrodes from the first plurality of continuous ring
electrodes is connected to a first input connection, the first
input connection terminating an input line, the input line
extending through a first via that penetrates a first insulating
layer that substantially separates the first electrode layer from
the input line, the electro-optic lens device is tunable from a
first optical power to a second optical power when a first voltage
is applied to the first input connection, the second electrode
layer is patterned and comprises a second plurality of ring
electrodes that form a second resistive divider network, the second
electrode layer is patterned and comprises a second plurality of
ring electrodes that form a second resistive divider network,
wherein at least one ring electrode from the second plurality of
ring electrodes is electrically connected to an adjacent ring
electrode by a second resistive bridge, a second sub-plurality of
ring electrodes from the first plurality of ring electrodes is
connected to a second input connection through a second via that
penetrates the first insulating layer, the first electrode layer
comprises a plurality of sets of ring electrodes, each set
comprising a corresponding plurality of ring electrodes, the first
electrode layer comprises a plurality of sets of ring electrodes,
each set comprising a corresponding plurality of ring electrodes, a
dedicated input connection is provided for each set, and wherein a
dedicated resistive bridge is provided between each adjacent pair
of ring electrodes in each set, at least one ring electrode on the
second substantially transparent substrate completely covers in a
planar direction at least two co-planar ring electrodes of the
first substantially transparent substrate, adjacent ring electrodes
of the same electrode layer of one or more of the first
substantially transparent conductive electrode layer and the second
substantially transparent conductive electrode layer are disposed
in different planes.
Description
CROSS REFERENCE
[0001] This application is continuation application of U.S. patent
application Ser. No. 13/900,834, filed May 23, 2013, which is a
continuation application of U.S. patent application Ser. No.
12/802,943, filed Jun. 17, 2010, now U.S. Pat. No. 9,280,020 for
TUNABLE ELECTRO-OPTIC LIQUID CRYSTAL LENSES HAVING RESISTIVE
BRIDGES AND METHODS FOR FORMING THE LENSES, which claims the
benefit of priority under 35 U.S.C. .sctn.119 of U.S. Provisional
Application Ser. No. 61/269,110, filed on Jun. 19, 2009, herein
fully incorporated by reference.
FIELD OF THE INVENTION
[0003] The present invention relates to electro-optic lenses,
including liquid crystals, wherein the power of the lenses can be
modified by application of an electric field. In one embodiment,
the liquid crystal-based lenses include ring electrodes having a
resistive bridge located between adjacent electrodes, and in a
preferred embodiment, input connections for several electrode rings
are spaced on the lens. In a further embodiment, liquid
crystal-based lenses are provided that can increase optical power
through the use of phase resets, wherein in one embodiment, a lens
includes ring electrodes on surfaces of the substrates on opposite
sides of the liquid crystal cell such that a fixed phase term can
be added to each set of electrodes that allows for phase change
across each group of electrodes to be the same and also be matched
with respect to a previous group.
BACKGROUND OF THE INVENTION
[0004] Electro-optical lenses that utilize birefringent liquid
crystal to alter their optical power are known. They have the
inherent advantage over conventional glass or plastic optical
lenses of being able to alter their optical power by the judicious
application of an electric field. One drawback of existing liquid
crystal electro-optic lenses is that the number of optical powers a
single lens can generate is presently limited.
[0005] One basic structure of electro-optic liquid crystal lenses
is that of a thin layer of liquid crystal sandwiched between two
transparent substrates. Onto the inner surfaces of each substrate,
a transparent metallic electrode structure is formed. An alignment
layer is formed on top of the electrode layers to establish a
specific orientation of the liquid crystal molecules when there is
no electric field present. An electric field is established across
the liquid crystal layer when voltage is applied to one electrode
layer and an electric potential is created between the electrodes.
If the electrode structure is patterned, a gradient in the field is
created that gives rise to a gradient in the index of refraction of
the liquid crystal layer. With proper design of the electrode
structure and the applied voltages, an electro-optic lens can be
fabricated.
[0006] Electro-optic liquid crystal lenses have been designed and
fabricated that utilize electrode structures to generate several
optical powers with a single lens.
[0007] The basic structure of a spherical electro-optic liquid
crystal lens is that of a circular ring electrode design, where the
transparent electrodes on one or both substrates consist of toric
rings, electrically insulated from adjacent neighboring rings.
Previous designs of these lenses are restrictive in the sense that
the ring electrode widths and spacing often determine the optical
power of the lens. However, if a very large number of very narrow
electrodes could be fabricated and addressed individually,
theoretically, a very large number of optical powers could be
generated by such a lens.
[0008] Considering that the optical phase change between each
adjacent electrode should be less than about 1/8 of a wave and that
the total phase change across a lens might be as high as 100 waves,
it first appears that an electrode structure consisting of hundreds
of rings addressed by hundreds of input connections to the device
might be required for continuous tuning. This is not an acceptable
solution, however, since the photolithography needed to create such
an electrode structure would be daunting. Moreover, fabricating the
buss structure to connect and electrically address each electrode
would be an overwhelming task and make the resulting device
extremely complex and unwieldy.
[0009] The use of phase-wrapping can help mitigate the problem of
fabricating hundreds of input connections to the lens. It has been
previously shown in "Liquid Crystal Based Electro-Optic Diffractive
Spectacle Lenses and Low Operating Voltage Nematic Liquid Crystals"
by Joshua Naaman Haddock, a Dissertation submitted to the Faculty
of the College of Optical Sciences in partial fulfillment of the
Requirements for a Degree of Doctor of Philosophy in the Graduate
College of the University of Arizona in 2005, that electrodes can
be grouped in such a way that the phase change over one group is
approximately one wave. Thus, the number of input connections is
limited to the number of rings in each group. However, this scheme
only provides high efficiency if the phase change across each group
of electrodes is very close to a multiple of one wave. Thus, the
phase change across each electrode group cannot be changed in a
continuous manner, and as a result, the lens cannot be continuously
tuned to multiple powers.
[0010] U.S. Publication No. 2008/0212007 relates to an
electro-optic device comprising a liquid crystal layer between a
pair of opposing transparent substrates; a resistive patterned
electrode set positioned between the liquid crystal layer and the
inward-facing surface of the first transparent substrate; and a
conductive layer between the liquid crystal layer and the
inward-facing surface of the second transparent substrate, wherein
the conductive layer and resistive patterned electrode set are
electrically connected, and wherein said resistive patterned
electrode set comprises one or more electrically-separated
electrodes, wherein the desired voltage drop is applied across each
electrode to provide the desired phase retardation profile.
SUMMARY OF THE INVENTION
[0011] It is an object of the invention to provide a tunable liquid
crystal-based lens, wherein the number of input connections for its
ring electrodes are reduced.
[0012] Yet another object of the present invention is to provide a
tunable liquid-crystal-based lens that is free of resets or phase
wrapping.
[0013] Another object of the invention is to provide a lens having
ring electrodes, wherein input connections are spaced, preferably
evenly, on the lens, such as at intervals greater than every 5 and
preferably about every 10 electrode rings.
[0014] A further object of the invention is to provide a lens
comprising ring electrodes, wherein at least two, and preferably
all adjacent electrodes are connected by a resistor.
[0015] Yet another object of the invention is to provide a lens
with a transparent resistive bridge between electrode rings,
wherein the resistive bridge is formed from a conductive coating,
preferably indium tin oxide in one embodiment.
[0016] Still a further object of the invention is to provide a lens
wherein the ring electrodes and resistive bridges are formed
utilizing the same material.
[0017] Still another object of the invention is to provide a lens
formed by a process comprising the step of forming a resistive
bridge between two electrode rings utilizing photolithography to
pattern the rings as well as the resistive bridge.
[0018] Yet another object of the present invention is to provide a
tunable liquid-crystal-based lens that includes resets and utilizes
phase wrapping.
[0019] A further object of the present invention is to provide a
lens having substrates located on opposite sides of a liquid
crystal layer, wherein both substrates include patterned
electrodes.
[0020] Another object of the invention is to provide a tunable lens
including two transparent substrates with patterned electrode
layers located on each substrate, wherein an electro-active liquid
crystal material is located between the substrates wherein one of
the patterned electrode layers provides fine control over the
optical phase retardance and the other layer provides coarse
control of the phase over a group of at least two of the fine
control electrodes.
[0021] Still a further object of the present invention is to
provide a tunable lens wherein an electrode of one substrate layer
overlaps at least two electrodes of an electrode layer of a second
substrate, wherein said overlap is in a direction of the planes of
the substrates.
[0022] Another object of the present invention is to provide
patterned electrodes on two substrate surfaces whereby a fixed
piston phase term is added to each set of electrodes in one section
by a blazed electrode structure that allows for phase change across
each group of electrodes to be the same, and also to be phase
matched with respect to a previous group.
[0023] In one aspect of the invention, a tunable electro-optic lens
device is disclosed, comprising at least two substantially
transparent substrates, a substantially transparent conductive
electrode layer operatively connected to each substrate, wherein at
least one of the electrode layers is patterned and includes a
plurality of ring electrodes, wherein at least one ring electrode
is electrically connected to an adjacent ring electrode by a
resistive bridge, and wherein an electro-active liquid crystal
material layer is present between the at least two substantially
transparent substrates.
[0024] Another aspect of the invention is a process for preparing a
tunable electro-optic lens device, comprising the steps of
providing a substantially transparent substrate forming at least
two conductive electrode rings on the substrate; and a resistive
bridge located between and electrically connecting said electrode
rings.
[0025] Still another aspect of the invention is a tunable
electro-optic lens device, comprising a first substantially
transparent substrate having a substantially transparent conductive
electrode layer operatively connected thereto, said electrode layer
being patterned and having a plurality of ring electrodes; a second
substantially transparent substrate having a substantially
transparent conductive electrode layer operatively connected
thereto, said second electrode layer being patterned and having a
plurality of ring electrodes; and an electro-active liquid crystal
material layer present between the first and second substantially
transparent substrates, wherein at least one ring electrode on the
second substrate covers in a planar direction at least two ring
electrodes of the first substrate.
[0026] Yet another aspect of the invention is a tunable
electro-optic lens device, comprising at least two substantially
transparent substrates, substantially transparent conductive
electrode layer on each substrate, and an electro-active material
disposed between the substrates wherein the electrode layers on
each substrate are patterned and comprise a plurality of ring
electrodes, and wherein the patterned electrode of one layer
provide fine control over the optical phase retardants and the
electrodes of the other layer provide a coarse control of the phase
over the group of at least two of the fine control electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention will be better understood and other features
and advantages will become apparent by reading the detailed
description of the invention, taken together with the drawings,
wherein:
[0028] FIG. 1 is a top view of a substrate utilized to form a
liquid crystal-based optical lens containing ring electrodes,
wherein adjacent electrodes are connected by resistive bridges;
[0029] FIG. 2 illustrates a close-up top view of a portion of the
patterned substrate illustrated in FIG. 1 including area 2-2,
particularly illustrating a resistive bridge;
[0030] FIG. 3 is a top view of one embodiment of a buss line
connected to a ring electrode through a via in the insulator;
[0031] FIG. 4 is a cross-sectional view of one embodiment of a
liquid crystal-based tunable lens of the present invention;
[0032] FIG. 5 is a top view of a further embodiment of an alternate
structure for a resistive bridge located between ring
electrodes;
[0033] FIG. 6 is a top view of one embodiment of a substrate
including an electrode layer comprising ring electrodes
thereon;
[0034] FIG. 7 is a top view of one embodiment of a buss line
connected to a ring electrode through a via in the insulator;
[0035] FIG. 8 is a bottom view of one embodiment of an opposing
substrate containing a plurality of electrode rings thereon;
[0036] FIG. 9 is a cross-sectional view of a two-layered design for
input line connections for a portion of a device of the present
invention; and
[0037] FIG. 10 is a cross-sectional view of a further embodiment of
a liquid crystal-based tunable lens of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0038] The electro-optic devices of the present invention are
lenses that are electrically tunable and comprise a liquid crystal
layer located between transparent substrates, wherein the liquid
crystal material is realignable in the presence of an electric
field. When voltage is applied across the cell containing the
liquid crystal material, the axis of orientation of the liquid
crystal material is changed, wherein the use of a patterned
electrode structure creates a gradient in the field that produces a
gradient in the index of refraction of the liquid crystal layer.
The focal length of the lens is tuned by adjusting the applied
electric field.
[0039] Tunable Lens Without Phase Wrapping
[0040] Referring now to the drawings, FIG. 4 illustrates a
cross-sectional view of a portion of one embodiment of an
electro-optical device 10 of the present invention. Device 10
includes a pair of substrates 20, 22, preferably planar and
disposed parallel to each other in one embodiment. The substrates
are maintained at a desired distance by spacers, not shown. The
spacing range can vary, and in one embodiment is from about 5 to
about 100 microns. An electrode layer 30 is present on lower
substrate 20 and an electrode layer 32 is present on upper
substrate 22, with the lower electrode layer 30 illustrated as a
patterned electrode, as further explained herein. An alignment
layer 50 is present on the substrates 20, 22, preferably on the
electrode layers 30, 32. A liquid crystal layer 60 is present
between the substrates 20, 22 and in contact with alignment layers
50. As utilized herein, the term "layer" does not require a uniform
thickness and imperfections or uneven thicknesses can be present so
long as the layer performs its intended purpose.
[0041] As the device 10 is a lens, the substrates 20, 22 must
provide desired optical transmission and preferably are
transparent. The substrates 20, 22 can be planar or can be curved.
Various materials can be utilized as known in the art, such as
glass, quartz or a polymer, with glass being preferred. The
substrate is preferably a non-birefringent material, or aligned or
compensated to minimize the effect of their birefringence.
[0042] The conductive electrode layers 30, 32 can be deposited on a
substrate by any known method. Preferably, patterned electrode 30
is formed utilizing a photo-lithographic process. The electrode
layer material can be any inorganic, substantially transparent
conductive material. Examples of suitable materials include metal
oxides such as indium oxide, tin oxide and indium tin oxide, and
preferably is indium tin oxide. The thickness of the conductive
electrode layer is generally from about 100 to about 2,000
angstroms. The electrode layer must be sufficiently thick to
provide desired conductivity. Resistivity of the conductive
electrode layer is generally from about 10 to about 1,000 ohms/sq
and is preferably from about 10 to about 200 or 300 ohms/sq.
[0043] The alignment layer 50 is used to induce a particular
directional orientation in the liquid crystal when no voltage is
applied to the device 10. Various materials suitable for use as
alignment layers are known in the art, including, but not limited
to, polyimide and polyvinyl alcohol. The thickness of the alignment
layer 50 should be sufficient to impart the desired directional
orientation to the liquid crystal material, such as about 100 to
about 1,000 angstroms. As known in the art, the alignment layer 50
is treated by rubbing in some embodiments to impart a substantially
homogenous molecular orientation to the liquid crystal material
prior to an electrical field being applied to the material.
[0044] Generally any liquid crystal material that has an
orientational order that can be controlled in the presence of an
electric field can be utilized, including any nematic, smectic or
cholesteric phase forming liquid crystals, or polymer-containing
liquid crystals such as polymer liquid crystals, polymer dispersed
liquid crystals or polymer stabilized liquid crystals. Nematic
liquid crystals are preferred in one embodiment. Desirable
characteristics possessed by suitable liquid crystal materials
include the ability to align the liquid crystal without much
difficulty, rapid switching time, and a low voltage threshold.
[0045] FIG. 1 illustrates one embodiment of a substrate 22 having
an electrode layer 30 present thereon. The electrode layer 30 is
patterned and includes a plurality of electrodes such as in the
shape of rings 34 surrounding a ring in the form of a central disk
35, wherein adjacent rings, and the innermost ring 34 and the disk
35 are electrically separated from each other by an electrically
insulating gap 36, with exception to a resistive bridge 38 as
described further herein. The insulating gap 36 is an open space
located between adjacent electrodes or can be a non-conducting
insulating material such as silicon dioxide. In one preferred
embodiment, the gap 36 is said open space. The rings 34 are
preferably substantially annular and concentric, although they may
not all be formed as a perfect geometric shape due to the material
and processing techniques utilized. That said, the term "ring" as
utilized herein encompasses structures that are ring-like, e.g.
elliptical rings. Likewise, disk 35 is preferably substantially
circular, but can also be ring-like. The electrodes can be in the
same plane or in different planes separated by an insulator,
whereby the resistive bridge 38 would connect electrodes in
different planes.
[0046] The width of the rings is set so that the maximum phase
difference between adjacent electrodes is less than approximately
1/8 wave in one embodiment.
[0047] The number of electrodes present on the substrate, i.e.,
both rings 34 and central disk 35, can vary. In one embodiment,
generally from about 20 to about 2,000 and preferably from about 50
to about 200 total electrodes are present on a substrate.
[0048] According to the present invention, at least one group of
electrodes, i.e., two or more electrodes, and preferably all or
substantially all of the electrodes present are part of a resistive
divider network. The electrode structure is designed so that a
series of substantially linear changes in phase retardation between
adjacent electrodes can be established that will yield the
parabolic r.sup.2 phase profile required to generate a focusing
optic. The resistive divider network comprises a resistive bridge
38 having a desired resistance that connects adjacent electrode
rings 34 or a ring 34 and disk 35, such as shown in FIGS. 1, 2 and
5. Depending on the design of the device, the resistive divider or
bridge 38 can have a resistance generally from about 100 to about
2,000 ohms and preferably from about 800 to about 1,200 ohms.
Resistive bridge 38 comprises a resistance path comprising an
electrically conductive material, preferably bordered by a
non-conductive material or an area free from conductive material
that aids in creating the desired resistance between each adjacent
electrode 34, 35.
[0049] The conductive material of the electrode bridge can be any
material as defined for the conductive electrode layer 30. The
material of the conductive electrode layer 30 can be different from
the conductive material of the resistive bridge, but preferably is
the same material. In one embodiment, indium tin oxide is the
preferred conductive material of the resistive bridge. As an
important benefit of the present invention, the method utilized to
create the desired electrode layer 30, for example
photolithography, is utilized to create the pattern of each
resistive bridge 38. Thus, patterned electrode layer and resistive
bridges are created utilizing photo-lithography in a single process
step. Thus, no additional materials or process steps are required
to form the resistive network.
[0050] In addition, if it is the case that the liquid crystal phase
change with voltage is also linear, than a continuously tunable
lens can be fabricated with only two input connections, one at the
innermost ring, i.e., disk 35, and one connection at an outermost
electrode ring, thereby eliminating the need for multiple buss
lines. This embodiment is especially useful when only a small
portion of the available phase change of the liquid crystal device
is utilized.
[0051] In an embodiment wherein the voltage vs. phase relation of
the liquid crystal device is considered linear over a small portion
of the total possible parabolic phase change, it is preferable to
connect each electrode by a fixed resistive bridge and then provide
an input connection for several electrode rings evenly spaced on
the lens. In one embodiment, an input connection is connected every
n.sup.th electrode ring, wherein n is 2 or more. Therefore, in one
embodiment, it is desirable to provide an input connection
connected at the innermost ring or disk 35 and provide further
input connections based on the number of rings, for example, from
about 10 to about 100 electrode rings and preferably from about 10
to about 20 electrode rings. For example, in an embodiment where
the substrate 22 includes 100 ring electrodes, wherein one of the
ring electrodes is an innermost disk electrode, electrodes 1, 10,
20, 30, 40, 50, 60, 70, 80, 90 and 100 are provided with input
connections. Thus, in this embodiment, it is only required that the
phase vs. voltage relation for the liquid crystal material is
linear over 1/10 of the range of the previous approach wherein no
resistive bridges were utilized. Similarly, in an embodiment
wherein 20 input connections are employed, linearity is only
required over 1/20 of the full range, or every fifth electrode.
FIG. 1 illustrates an input connection 70 each connected to the
first electrode and the tenth electrode of electrode layer 30.
[0052] The input connections 70 to the desired electrodes can be
placed on the side of the electrode closest to the substrate or the
opposite side of the electrode, away from the substrate. The input
connections are preferably formed by depositing an insulating
material, such as silicon dioxide between the electrode layer and
the input connection. Each input connection is connected to the
appropriate electrode through a via in the insulator, such as shown
in FIG. 3. In an embodiment wherein an input connection is located
on the side of an electrode away from the substrate, the input
connection can be fabricated by depositing a thin layer of
insulator over the electrode layer, and then growing an input
connection line over the insulating layer for each input
connection.
[0053] In an example embodiment, a liquid crystal layer, for
example comprising liquid crystal 18349 available from Merck,
having a thickness of about 25 .mu.m will give an optical power of
about 0.5 diopters for a lens diameter of approximately 1 cm. More
optical power can be achieved by increasing the liquid crystal
layer thickness, but eventually non-linearity in the fields will
degrade the optical performance; the switching relaxation time
between the various powers will also increase with liquid crystal
thickness. Additional optical power can also be achieved by
stacking multiple electro-optic devices 10.
[0054] An appropriate voltage is applied to the device 10, namely
the electrode layer 30 through the input connections 70 as known to
those of ordinary skill in the art. The unpatterned electrode layer
32 serves as a ground. The voltage is applied to the device 10
based on a number of factors, including, but not limited to, the
liquid crystal material utilized and the thickness of the liquid
crystal material between electrodes. Various methods are known in
the art for controlling the voltage applied to the electrode, for
example, a circuit, a processor or micro-processor.
[0055] Tunable Lens With Phase Wrapping
[0056] A further embodiment of the present invention relates to a
tunable electro-optic device that utilizes phase wrapping. The
device has the advantage of achieving higher optical power through
the use of phase resets.
[0057] In contrast to the phase wrapping method described in the
Background, the embodiment of the present invention does not
require each electrode ring to have an individual output
connection, but at the same time allows for a phase-wrapped lens
that is tunable.
[0058] In this embodiment, patterned electrodes are provided on
both substrate surfaces, on either side of the liquid crystal
material, and thus a fixed "piston" phase term can be added to each
set of electrodes in one section of the blazed electrode structure.
This allows for the phase change across each group of electrodes to
be the same, and then also to be phase matched with respect to the
previous group.
[0059] FIG. 10 illustrates a cross-sectional view of one portion of
one embodiment of an electro-optical device 110 of the present
invention. Device 110 includes a pair of substrates 120, 122
generally both parallel to each other. That said, the substrates
may be planar and/or curved, etc. An electrode layer 130 is present
on lower substrate 120 and an electrode layer 132 is present on
upper substrate 122, with both electrode layers being patterned
electrodes, as further explained herein. An alignment layer 150 is
present on each substrate 120, 122, preferably on the electrode
layers 130, 132 and disposed adjacent liquid crystal layer 160,
wherein the materials, specifications and configurations, etc.
described hereinabove for each of the respective components are
herein incorporated by reference.
[0060] FIG. 6 illustrates a top view of one embodiment of substrate
120 including a plurality of electrodes, each having a respective
input connection 170. Electrodes generally comprise a ring-like
circular or disk electrode 135 and a plurality of ring electrodes
134, such as described herein. In a preferred embodiment, the
electrode layer 130 comprises adjacent electrodes disposed in
different planes, see FIG. 9 for example. Insulating material 140
separates the different planes of the ring electrodes 134. The
input connection/electrode ring connection is formed through a via,
such as shown in FIG. 7.
[0061] FIG. 8 illustrates one embodiment of substrate 122, adapted
to be disposed on an opposing side of the liquid crystal layer 160
as compared to substrate 120 as illustrated in FIG. 10, including
an electrode layer 132, in this case a counter electrode layer,
including a plurality of electrode rings 134 surrounding a central
ring-like circular electrode or disk electrode 135. According to
the invention, a single ring or disk structure on the counter
electrode layer 132 has a wider or greater area than an electrode
ring of the lower substrate 120 and covers or overlaps at least one
group of two or more rings. The area determination is made for
electrodes dispersed directly across the liquid crystal material
layer from each other, generally perpendicular or normal to the
plane of the substrate where the particular electrodes are
disposed. In particular, FIG. 8 illustrates the design for a coarse
counter electrode layer that provides the piston-like phase change
over several groups e.g. 4 fine-ring electrodes 134 of lower
electrode layer 130 on substrate 120. Input connections 170 are
provided for each of the electrodes of the upper electrode layer
132.
[0062] As illustrated in FIG. 10, a liquid crystal material 160 is
located between substrates 120, 122 and electrode layers 130,
132.
[0063] One example of the approach of the embodiment of the
invention including a tunable lens with phase wrapping is as
follows.
[0064] As an example of the technique, it is assured that a device
is desired that is optically tunable over a range of 1.5 diopters
in 0.25 diopter steps or less. To achieve this tunable
electro-optic lens, a fine-ring structure is fabricated that, in
this example, has all electrodes in groups of 4 rings (i.e.,
electrode ring n has the same voltage has ring n+4). A
counter-electrode ring structure is present on the other substrate
where each electrode ring of the counter electrode ring has a much
wider area and covers one group of rings of the opposing electrode,
i.e. 4 fine rings, generally in a direction substantially
perpendicular or normal to the plane of the substrate. FIG. 8
illustrates the design for the coarse counter-electrode layer that
provides the piston-like phase change over several groups of 4
fine-ring electrodes that are illustrated in FIG. 6. The wide
rings, m, are grouped into 12 rings (ring m has the same voltage as
ring m+12). Thus, there are 16 input connections needed to
electrically drive the lens: 12 for the wide rings of the
counter-electrode and 4 for the fine rings of the first electrode.
With this design, one is able to select how many groups of fine
electrodes are used to get to one wave of phase retardation,
realizing that the minimum number of fine rings or voltages per
retardation wave for an accurate phase representation is 8.
Therefore, one can select to have 2, 3, 4, 6 or 12 groups of 4 fine
electrode rings per wave of phase retardation, with 12 groups per 1
wave of retardation yielding the greatest efficiency but smallest
optical power, and 2 groups per wave yielding the least efficiency
but greatest optical power.
[0065] For this example, the range of the required change is 1.5
diopters, so a variable lens that has a power range from -0.75 to
+0.75 diopters is needed. By the choice of how the electrodes are
grouped, if the highest power of the lens needs to be +0.75
diopters, then the power of the lens with 2, 3, 4, 6 or 12 groups
of electrodes will be: +0.75, +0.5, +0.375, +0.25 or +0.125
diopters. Because the device works with the opposite electrical
polarity, it will also generate the identical negative optical
powers, as well.
[0066] Thus, this embodiment of phase-wrapped electronic lens is
tunable over 11 levels of optical power. Of course, this power
range can be offset by adding a fixed power lens. For example, by
combining the device in the example above with a -2.25 diopter
conventional lens, one can tune from -1.5 to -3.0 diopters in 11
steps. Alternatively, by combining it with a +1.75 diopter
conventional lens, one can tune from +1.0 to +2.5 diopters.
[0067] To more clearly illustrate the voltages applied to the
electrodes, a LC device is needed where the phase retardation is a
linear function of the voltage applied, and rather than specify
voltages, one can say that each electrode has a voltage that yields
particular phase retardation relative to the center electrode.
[0068] With that definition, for the case of a negative lens, the
voltages applied to the four fine electrodes in each group are:
[0069] Fine electrode #1=0 [0070] Fine electrode #2=2 .pi./(4*j)
[0071] Fine electrode #3=4 .pi./(4*j) [0072] Fine electrode #4=6
.pi./(4*j)
[0073] where j in this example is 2, 3, 4, 6 or 12, corresponding
to the relative lens powers.
[0074] The voltages for the counter-electrodes in this example
would correspond to the phases:
Phase ( radians ) = 0 , 2 .pi. j , 2 * 2 .pi. j , 3 * 2 .pi. j ( j
- 1 ) * 2 .pi. j ##EQU00001##
[0075] As a particular example, consider tuning this lens to be
-0.5 diopters (j=3). The voltage applied to the fine electrodes
will correspond to a phase of: [0076] 1. 0 (by definition) [0077]
2. 2 .pi.*(1/12) [0078] 3. 2 .pi.*(2/12) [0079] 4. 2
.pi.*(3/12)
[0080] The voltage applied to the counter electrodes will give a
phase of: [0081] 1. 0 (by definition) [0082] 2. 2 .pi.*(1/3) [0083]
3. 2 .pi.*(2/3) [0084] 4. 0 [0085] 5. 2 .pi.*(1/3) [0086] 6. 2
.pi.*(2/3) [0087] 7. 0 [0088] 8. 2 .pi.*(1/3) [0089] 9. 2
.pi.*(2/3) [0090] 10. 0 [0091] 11. 2 .pi.*(1/3) [0092] 12. 2
.pi.*(2/3)
[0093] Then counting from the center electrode and going out, the
relative phase at the location of each fine ring will be:
TABLE-US-00001 1. 0 = 0 2. 2 .pi.* (1/12) =2 .pi. *(1/12) 3. 2 .pi.
* (2/12) =2 .pi. *(2/12) 4. 2 .pi. * (3/12) =2 .pi. *(3/12) 5. 0 +
2 .pi. *(1/3) =2 .pi. *(4/12) 6. 2 .pi. * (1/12) + 2 .pi. *(1/3) =2
.pi. *(5/12) 7. 2 .pi. * (2/12) + 2 .pi. *(1/3) =2 .pi. *(6/12) 8.
2 .pi. * (3/12) + 2 .pi. *(1/3) =2 .pi. *(7/12) 9. 0 + 2 .pi.
*(2/3) =2 .pi. *(8/12) 10. 2 .pi. * (1/12) + 2 .pi. *(2/3) =2 .pi.
*(9/12) 11. 2 .pi. * (2/12) + 2 .pi. *(2/3) =2 .pi. *(10/12) 12. 2
.pi. * (3/12) + 2 .pi. *(2/3) =2 .pi. *(11/12) 13. 0 =0 14. 2 .pi.
* (1/12) =2 .pi. *(1/12) 15. 2 .pi. * (2/12) =2 .pi. *(2/12) 16. 2
.pi. * (3/12) =2 .pi. *(3/12) 17. .etc. 18. . . . 19. . . . 20. . .
.
[0094] The voltages addressed to the fine electrodes and counter
electrodes, corresponding to each of the optical powers as
illustrated above, can be stored in a memory chip that communicates
with a power supply and the lens. The chip is programmed to provide
the required optical power on demand.
[0095] Tunable lens devices for example devices 10, 110 illustrated
in the drawings, of the present invention can be utilized in
numerous different applications, including, but not limited to,
lenses, for example glasses or spectacles, cameras, various
displays, telescopes, zoom lenses, wavefront correctors and
equipment used to diagnose imperfections in the human eye. The
tunable lenses of the invention can be utilized wherever
conventional lenses and optics are utilized.
[0096] While in accordance with the patent statutes the best mode
and preferred embodiment have been set forth, the scope of the
invention is not limited thereto, but rather by the scope of the
attached claims.
* * * * *