Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
The invention relates to electro-optical lenses
whose electromagnetic radiation absorption characteristics
can be selectively altered by influence of a suitably
controlled electric field. In particular, the invention
relates to electro-optical ophthalmic lenses whose light
transmissive pxoperties can be varied by application of
electricity.
In U.S. patent Nos. 3,521,941, 3,578,843,
3,704,057, 3,708,220 and 3,829,196, electro-optical devices
are disclosed which exhibit a phenomenon termed in the art
as persistent electrochromism. This phenomenon is
characterized by the alteration of the electromagnetic
radiation absorption characteristics of the persistent
electrochromic material by the influence of an electric
field. Such devices commonly are employed in sandwich
arrangement, with a persistent electrochromic material
layer and an ion-conducting layer sandwiched between two
electrodes. Coloration is induced by charging the electro-
chromic layer negative with respect to the counter-electrode,
employing an external potential. The counter-electrode can
be the same as the persistent electrochromic material or
different. By reversing the original polarity of the field
or by applying a new field, the visible coloratlon can be
erased. This procedure of color induction and erasure is
defined as cycling.
Prior methods for reducing light transmission
through optical lenses employed as eyeglasses are capable
of achieving desirable degrees of light reduction~ However,
these sunglass lenses generally are not adjustable or
variable with regard to their light transmissive properties.
Recent developments have produced what is known as a photo-
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chromic lens which is self adJustable. A layer w~ithin the lens s-tructure
is induced by electromagnetic radiation to alter its light absorption
properties. An increasing degree of ambient brightness results in
darker coloration o~ the lens, thereby reducing light transmission -
through the lens. However, such a system suffers from several inherent
disadvantages. Photochromic systems with fast switching speeds tend to be
unstable, whereas the most stable systems tend to have slow switching
speeds. In particular, erasure upon removing a photochromic ophthalmic
lens from brlght light to relative darkness is quite slow. Application of
photochromic lenses in eyewear specifically could prove hazardous if the -
wearer suddenly passes from bright to dim light. A person stepping from
bright sunlight into a building or a driver passing into a tunnel while
wearing photochromic glasses would remain "in the dark" for many critical
seconds. Also, since colorless photochromic systems can be activated only
by a change in electromagnetic radiation in the W portion of the spectrum,
the system is largely inoperative when the wearer is screened by a W
filter such as a glass window. The ligh-t-induced coloration of the lenses
is entirely outside the control of the wearer. ~he degree of light trans-
mission cannot be adjusted and depends solely on the degree of ambient
electromagnetic radiation.
Hence, for safety, convenience and efficiency, an optical
lens is needed which can control the light transmissive properties of
the lens either automatically or independently, with ~uick cycling speed,
and with selective adjustment of the degree of light transmission.
In accordance with this invention there is provided an
electro-optical lens device comprising an optical lens coated with a layer
of solid persistent electrochromic material, an ion-conducting layer,
a pair of electrodes in contac~ wi-th these layers, and means for applying
direct current voltage to said pair of electrodes to create an electric ~ -
field across said layers, said electric field being of such a polarity to
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alter light abs~rption characteristics of said mate~ial~ ~hereb~ said .
absorption may be varied ~rom substantially no absorptl~n to a desired
degree o~ absorption~ so as to vary the amount o~ light transmitted
throu~h said lens. :
The variable light transmissive optical lens
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structure of the present invention is formed by coating a
layer of solid persistent electrochromic material and an
ion-conducting layer on an optical lens. A pair of elec-
trodes connected to a dc power source is placed in contact
with the electrochromic and ion-conducting layers, so that
an electric field may be applied across the material. ,
Accordingly, the electrochromic material can be selectively
colored or erased to a desired degree of light absorptivity.
This novel lens can be incorporated into an eyeglass struc-
ture with appropriate connections to a source of electrical
power to effect the desired change in transmission.
Detailed Description of the Invention
As used herein, a "persistent electrochromic
material" is defined as a material responsive to the appli-
cation of an electric field of a given polarity to change
from a first persistent state in which it i5 essentially
non-absorptive of electromagnetic radiation in a given
wavelength region, to a second persistent state in which it
is absorptive of electromagnetic radiation in the given
wavelength region, and once in said second state, is
responsive to the application of an electric field of the
opposite polarity to return to its first state. Certain of
such materials can also be responsive to a short circuiting
condition, in the absence o~ an electric field, so as to
return to the initial state.
By "persistent" is meant the ability of the
material to remain in the absorptive state to which it is
changed, ater removal of the electric field, as distin-
guished from a substantially instantaneous reversion to
the initial state, as in the case of the Franz-Keldysh
effect.
The invention may be further understood from the
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following more particular description of a preferred
embodiment of the invention, as illustrated in the accom-
panying drawings in which like reference characters refer
to the same parts throughout the different views. The
drawings are not necessarily to scale, emphasis instead
being placed on illustrating principles of the invention.
~ig. 1 is a pictorial view of a pair of eyeglasses
including the variable light transmissive lenses according
to the invention.
Fig. 2 illustrates, in partial cross section, a
lens structure as described and claimed.
Referring to elements of the invention as embodied
in the drawings, numeral 36 in Fig. 1 generally represents
a pair of electrochromic eyeglasses which comprises a
standard assembly with temple support arms 48 hingedly
attached to a lens frame unit 54. The basic appearance of
the eyeglasses corresponds to standard commercial eye wear. `
However, in place of a simple optical lens, the electro-
optical lens of the present invention is inserted. The
operation of the variable light transmissive lenses requires
the application of an electric field across the electro-
chromic layer coated on the lens. Miniature batter~v 34 in
the temple support arm provides dc voltage, preferably
about 1 - 5 volts. The battery i5 connected through con-
ducting wires 42 and 44 to the lens units to control the
light absorption thereof. Pushbutton switches 30 and 32
and 50 and 52 are included in the circuit to allow selective
operator control of cycling - lens coloration and erasure.
Individual sets of pushbutton control switches are provided
for each o~ lenses 38 and 40, so that separate control of
each lens is possible. An operator, by depressing the
respective coloration or erasure button can readily adjust
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the light transmission of each lens as desired. Separate
controls adapt the glasses to multiple specialized uses. ~ !
For example, selective darkening of one lens while main-
taining maximum transmission to the other eye would prove
convenient and beneficial to such as microscopists, photo-
graphers and sharpshooters etc., who are normally required
to close or block one eye during operation.
Coloration and erasure also can be accomplished
automatically according to ambient light levels by utili-
zation of photocell 46 which is built into the lens frame
and integrated into the switching circuitry.
Fig. 2 shows a cross section of the layered lens
structure of the invention. Numeral 18 represents the
actual optical lens substrate which is coated with light
modulating layers. The layers, successively deposited
comprise a transparent conductive material 16 such as SnO2,
a persistent electrochromic material 14 such as WO3 or
MoO3, an ion conducting layer 12 such as SiOx or ~-alumina,
and transparent counter-electrode 10 of conductive material
such as Au or a transparent oxide. The layers may be ~ -
deposited by known vacuum deposition techniques. A source
; of dc potential 22 is coupled to electrodes 16 and 10 ;
through a reversing switch indicated by 20. As shown, with
the switch arm in the position to produce coloration, the
positive terminal of the source is connected to the outer
or gold electrode while the negative terminal is connected
to the tin oxide layer on the optical lens substrate.
Once complete coloration is induced, typically in a matter
of seconds, switch 20 may be opened/ disconnecting the
battery from the device entirely, and the device will
remain in its darkened state without further application ^
of power. To erase a previously darkened surface, the
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switch arm is thrown to the erase contacts, across which
is connected a potentiometer 24. As shown, the potentio-
meter contact or slider is movable from a point at which
the electrodes 16 and 10 are short circuited to a point at
which full battery voltage, of polarity opposite to the
coloration condition, is applied between them. Any number
of reverse voltage values may be obtained between the two
extremes.
In the position illustrated in the drawing, a ;
"bleach" voltage of a value less than battery voltage is
applied across the electrodes, setting up a corresponding
electric field. Under the influence of this field, the
device returns to its initial uncolored state. The rapidity
with which the bleaching occurs is determined by the
magnitude of the voltage; the higher the voltage, the
faster the bleaching process is completed. At the higher
bleaching voltages, it has been found that the bleaching
process is even faster than the coloring operation. Once ~ -
th`e bleaching is completed, the switch may be opened to
2a disconnect the battery from the device and minimize power
drain.
It has also been found that, notwithstanding the
- absence of an electric field, when the potentiometer is in
its short circuiting position, certain of the pexsistent
electrochromic materials nevertheless will return completel~
and positively from the colored to the bleached state. The
rate at which the bleaching occurs, however, is somewhat
slower than when the material is subjected to an electric
field.
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The materials which form the electrochromic
materials of the device in general are electrical insulators
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or semiconductors. Thus are excluded those metals, metal
alloys, and other metal-containing compounds which are -
relatively good electrical conductors. Suitable materials
are as described in U.S. Patent 3,521,941. These include
S materials aontaining a transition metal element ~including
Lanthanide and Actinide series elements), and materials
containing non-alkali metal elements such as copper.
Preferred materials of this class are films of transition
metal compounds in which the transition metal may exist
in any oxidation state from ~2 to +8. Examples of these
are: transition metal oxides, transition metal oxysulfides,
transition metal halides, selenides, tellurides, chromates, -
molybdates, tungstates, vanadates, niobates, tantalates,
titanates, stannates, and the like. ;
When the persistent electrochromic materials are -
employed as films, thickness desirably will be in the range
of from about 0.1-100 microns. However, since a small
potential will provide an enormous field strength across
very thin films, the latter, i.e., 0.1-10 microns, are
preferred over thicker ones. Optimum thickness will also
be determined by the nature of the particular compound being
laid down as a film and by the film-forming method since
the particular compound and film-forming method may place
physical (e.g., non-uniform film surface) and economic
limitations on manufacture of the devices.
When tungsten oxide is employed as the electro-
chromic imaging material and an electric field is applied
~ between the electrodes, a blue coloration of the previously
; transparent electrochromic layer occurs, i.e., the per-
sistent electrochromic layer becomes absorptive of electro-
magnetic radiation over a band encompassing the red end of
the visible spectrum, thereby rendering the imaging layer
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blue in appearance. Prior to the application of the electric field, the
electrochromic imaging layer was essentially non-absorbent and thus
transparent .
Ion-Conducting Layer
The layer should be substan-tially -transparent.
One embodiment employs a solution of ~2S04 in glycerin.
Other suitable ion-conductors are as disclosed in U.S. Patent ~os. 3,704,057
and 3,708,220.
~n a preferred embodiment the ion-conducting layer is an
inorganic or other solid material, e.g. silicon oxide, calcium fluoride,
magnesium fluoride, or the like, metal oxides and sulfides, synthetic
resin films, or the like, as disclosed in U.S. Patent No. 3,521,941.
Electrodes
Virtually any material exhibiting elec-trical conductivity
may be used for an electrode. The same material may be used for both
electrodes or each electrode may be of a different material, or mixtures
or alloys of different materials. Typical electrode materials are the
metals, e.g., gold, silver, aluminum, and conducting non-metals such as
carbon, suitably doped tin or indium oxide, and the like. As already
indicated, both of the electrodes should be of an optical quality effective
for transmission of the electrochromic change. ;
The negative and positive electrodes need only be in
electrical contact with the film. Any type and arrangement of electrodes
~; and film effective to impose an electric field on the film when the
; electrodes are connected to a voltage source, will be suitable. Thus, the
electrodes may be spaced conducting strips deposited on or imbedded in
the film at the lens periphery or they may be conducting layers between
which the film is inserted.
While the invention has been particularly shown and described
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thereof, it will be understood by those skilled in the art
that various alterations in form and detail may be made
therein without departing from the spirit and scope of the
invention. For example the circuitry and switching arrange-
ments can be changed to suit ease of operation or cosmeticdesign. Also, since power application is needed only to
color and bleach the devlce, a source of continuous power
within the eyeglass structure is not a necessity. A remote
power supply can be utilized to accomplish desired cycl~ng.
Such can be portable and, for example, be conveniently ,
incorporated-into an eyeglass case. The glasses may take
various forms such as ~elding goggles, laser protective
goggles, eyeglasses, sunglasses or special glasses for
microscopists~ photographers or sharpshooters. `
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