U.S. patent application number 12/370938 was filed with the patent office on 2010-08-19 for variable focus liquid filled lens apparatus.
Invention is credited to Amitava GUPTA, Karim HAROUD, Urban SCHNELL.
Application Number | 20100208194 12/370938 |
Document ID | / |
Family ID | 42559610 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100208194 |
Kind Code |
A1 |
GUPTA; Amitava ; et
al. |
August 19, 2010 |
VARIABLE FOCUS LIQUID FILLED LENS APPARATUS
Abstract
A variable focus lens apparatus includes at least one rigid
optical disc, at least one flexible optical membrane and at least
one layer of a transparent fluid that is in communication with a
fluid channel and a reservoir. When incorporated in a spectacle
lens, the lens system enables wearers to adjust the power of each
lens individually, so as to achieve the preferred binocular visual
performance, consistent with maximum stereopsis and binocular
fusion at any desired object plane.
Inventors: |
GUPTA; Amitava; (Roanoke,
VA) ; HAROUD; Karim; (Chavannes-sur-Moudon/VD,
CH) ; SCHNELL; Urban; (Munchenbuchsee/BE,
CH) |
Correspondence
Address: |
STERNE, KESSLER, GOLDSTEIN & FOX P.L.L.C.
1100 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Family ID: |
42559610 |
Appl. No.: |
12/370938 |
Filed: |
February 13, 2009 |
Current U.S.
Class: |
351/159.68 ;
359/666 |
Current CPC
Class: |
G02B 1/14 20150115; G02B
3/14 20130101; G02C 2202/16 20130101; G02B 3/02 20130101; G02C
7/085 20130101; G02B 1/11 20130101 |
Class at
Publication: |
351/159 ;
359/666 |
International
Class: |
G02C 7/02 20060101
G02C007/02; G02B 3/14 20060101 G02B003/14 |
Claims
1. A variable focus optical apparatus, comprising: a rigid, curved,
transparent optical component, at least one transparent,
distensible membrane attached to a periphery of said rigid optical
component to define a cavity therebetween, a variable amount of
fluid filling said cavity, and a reservoir containing additional
fluid and in fluid communication with said cavity, said reservoir
being operable to provide injection of fluid into said cavity or
withdrawal of fluid out of said cavity in response to a force or an
impulse.
2. The variable focus optical apparatus of claim 1 further
comprising a communication channel providing fluid communication
between said reservoir and said cavity.
3. The variable focus optical apparatus of claim 2 wherein said
cavity, said reservoir and said communication channel comprise a
sealed system.
4. The variable focus optical apparatus of claim 1 wherein said
membrane is attached to the periphery of said rigid optical
component at least in part by adhesive seal or laser welding.
5. The variable focus optical apparatus of claim 1 wherein said
membrane is at least in part bonded to a support element that is in
turn bonded to the periphery of said rigid optical component.
6. The variable focus optical apparatus of claim 1 wherein said
membrane is at least in part seated with the periphery of said
rigid optical component within a ring to provide attachment
thereto.
7. The variable focus optical apparatus of claim 6 wherein said
ring comprises a communication channel providing fluid
communication between said reservoir and said cavity.
8. The variable focus optical apparatus of claim 1 wherein said
rigid optical component is curved into a meniscus shape.
9. The variable focus optical apparatus of claim 8 wherein the
anterior surface of said rigid optical component has an aspheric
geometry.
10. The variable focus optical apparatus of claim 8 wherein said
rigid optical component has an optical power that is at or below a
minimum of the power range designed to be provided by the variable
focus optical apparatus.
11. The variable focus optical apparatus of claim 1 comprising: two
transparent, distensible membranes attached to a periphery of said
rigid optical component to define two cavities, a first cavity
between said rigid optical component and a first membrane and a
second cavity between said first membrane and a second membrane,
and a variable amount of fluid filling each of said cavities,
wherein said reservoir is in fluid communication with one of said
cavities.
12. A set of eyeglasses designed for ophthalmic applications
comprising at least one variable focus optical apparatus of claim
1, an actuator and a frame.
13. The set of eyeglasses of claim 12 wherein the optical power of
at least one of the lenses thereof is separately adjustable by the
wearer.
14. The set of eyeglasses of claim 12 wherein said reservoir is
situated in said frame and is operable by said actuator.
15. The set of eyeglasses of claim 14 wherein the optical power of
at least one of the lenses is adjustable by the actuator dispenser
and thereafter altered to prevent further adjustment.
16. The set of eyeglasses of claim 14 further comprising a
communication channel within said frame providing fluid
communication between said reservoir and said cavity.
17. The variable focus optical apparatus of claim 1 wherein said
rigid optical component is made of an impact resistant polymer, a
scratch resistant coating, or an antireflective coating.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of variable focus
lenses, and more particularly to consumer ophthalmic lenses that
are at least in part fluid- or liquid-filled.
BACKGROUND OF THE INVENTION
[0002] It is known that the ability of the human eye to
accommodate, i.e., to alter the focal length of the natural lens in
the eye, is gradually diminished with increased age. Accommodation
in human beings is reduced to 3D (diopters) or less at an age range
of 35-45 years. At that point, reading glasses or some other form
of near vision correction becomes necessary for the human eye to be
able to bring near objects (such as lines of text in a book or a
magazine) to focus. With further aging, accommodation drops below
2D, and at that point visual correction when working on a computer
or when performing some visual task at intermediate distances is
needed.
[0003] For best results and for best visual comfort, it is
necessary to bring each eye to focus on the same viewing target,
e.g., a computer screen. A large segment of population requires a
different visual correction for each eye. These people, known as
anisometropes, require different visual correction for each eye in
order to achieve maximum visual comfort while reading or working on
a computer. It is known that, if each of the two eyes of
anisometropes is not brought to focus at the same viewing plane,
the resulting anisometropic image blur causes a loss of stereopsis
(depth perception). Loss of stereopsis is one of the best
indications of loss of binocular function. Loss of binocularity at
the reading plane may cause a drop in reading speed and rate of
comprehension, and may hasten the onset of fatigue upon sustained
reading or working on a computer. Reading glasses fitted with
individually adjustable liquid lenses are therefore uniquely suited
for the visual need of individuals with loss of binocular
function.
[0004] Variable focus lenses can take the form of a volume of
liquid enclosed between flexible, transparent sheets. Typically,
two such sheets, one forming the lens front surface and one forming
the lens back surface, are attached to one another at their edges,
either directly or to a carrier between the sheets, to form a
sealed chamber containing the fluid. Both sheets can be flexible,
or one can be flexible and one rigid. Fluid can be introduced into
or removed from the chamber to vary its volume, and, as the volume
of liquid changes, so does the curvature of the sheet(s), and thus
the power of the lens. Liquid lenses are, therefore, especially
well suited for use in reading glasses, that is, eye glasses used
by presbyopes for reading.
[0005] Variable focus liquid lenses have been known at least since
1958 (see, e.g., U.S. Pat. No. 2,836,101, to de Swart). More recent
examples may be found in Tang et al, "Dynamically Reconfigurable
Liquid Core Liquid Cladding Lens in a Microfluidic Channel", LAB ON
A CHIP, Vol. 8; No. 3, pp. 395-401 (2008), and in International
Patent Application Publication No. WO 2008/063442, entitled "Liquid
Lenses with Polycyclic Alkanes". These liquid lenses are typically
directed towards photonics, digital phone and camera technology,
and microelectronics.
[0006] Liquid lenses have also been proposed for consumer
ophthalmic applications. See for example, U.S. Pat. Nos. 5,684,637
and No. 6,715,876 to Floyd, and U.S. Pat. No. 7,085,065, to Silver.
These references teach pumping of liquid in or out the lens chamber
to change the curvature of an elastic membrane surface, thus tuning
the focus of the liquid lens. For example, U.S. Pat. No. 7,085,065,
entitled "Variable Focus Optical Apparatus", teaches a variable
focus lens formed from a fluid envelope comprising two sheets, at
least one of which is flexible. The flexible sheet is retained in
place between two rings, which are directly secured together, such
as by adhesive, ultrasonic welding or any similar process, and the
other, rigid sheet may be directly secured to one of the rings. A
hole is drilled through the assembled lens to allow the cavity
between the flexible membrane and the rigid sheet to be filled with
transparent fluid.
[0007] Liquid lenses have many advantages, including a wide dynamic
range, the ability to provide adaptive correction, robustness and
low cost. However, in all cases, the advantages of liquid lenses
must be balanced against its disadvantages, such as limitations in
aperture size, possibility of leakage and inconsistency in
performance. In particular, Silver has disclosed several
improvements and embodiments directed towards effective containment
of the fluid in the liquid lens to be used in ophthalmic
applications, although not limited to them (e.g., U.S. Pat. No.
6,618,208 to Silver, and references therein). Power adjustment in
liquid lenses has been effected by injecting additional fluid into
a lens cavity, by electrowetting, by application of ultrasonic
impulse and by utilizing swelling forces in a cross linked polymer
upon introduction of a swelling agent such as water.
[0008] Commercialization of liquid lenses is expected to occur in
the near future, provided that some of the limitations noted above
can be remedied. Even so, the structure of prior art liquid lenses
is bulky and not aesthetically suitable for consumers, who desire
spectacles having thinner lenses and spectacles without bulky
frames. For the lenses that operate by injection or pumping of
liquid into the body of the lens, a complicated control system is
usually needed, making such lenses bulky, expensive and sensitive
to vibration.
[0009] In addition, to date, none of the prior art liquid lenses
provides the consumer with the ability to introduce the liquid into
or remove it from the lens chamber so as to himself change its
volume in order to vary the power of the lens.
SUMMARY OF THE INVENTION
[0010] In accordance with the objects of the invention, a
liquid-filled lens for consumer, ophthalmic applications is
provided. The lens has a front member that is rigid provided by an
optic made of glass or plastic, a back surface comprising a
flexible membrane stretched over the edge of the rigid optic, and a
fluid filling the cavity formed between the front optic and the
flexible membrane. The liquid-filled lens may comprise one or more
liquid filled cavities, contained by a corresponding number of
membranes. Each liquid filled cavity is sealed, and is under a
positive pressure in order to maintain the membrane in a stretched
state. The front optic may have an aspheric surface geometry and
may have a meniscus shape.
[0011] In certain embodiments, the invention provides a variable
focus optical apparatus comprising a rigid, curved, transparent
optical component, at least one transparent, distensible membrane
attached to a periphery of the rigid optical component to define a
cavity therebetween, a variable amount of fluid filling the cavity,
and a reservoir containing additional fluid and in fluid
communication with the cavity and being operable to provide
injection of fluid into the cavity or withdrawal of fluid out of
the cavity in response to a force or an impulse.
[0012] A communication channel could provide fluid communication
between the reservoir and the cavity, forming a sealed system. The
communication channel providing fluid communication between the
reservoir and the cavity can be within a ring, within which the
membrane and the periphery of the rigid optical component are at
least in part to provide attachment thereto.
[0013] In other embodiments, the invention could provide a variable
focus optical apparatus having two membranes attached to a
periphery of said rigid optical component to define two cavities, a
variable amount of fluid filling each of the cavities, and a
reservoir is in fluid communication with at least one of the
cavities.
[0014] In other embodiments, the invention could provide a set of
eyeglasses for ophthalmic applications having comprising at least
one variable focus lens, a reservoir actuator and a frame, wherein
the optical power of at least one of the lenses is separately
adjustable by the wearer. In certain embodiments of the eyeglasses,
the reservoir could be situated in the frame and be operable by the
actuator to adjust the optical power of at least one of the lenses.
In certain embodiments of the eyeglasses, the communication channel
could be situated within said frame providing fluid communication
between said reservoir and said cavity.
[0015] A liquid filled lens is capable of providing variation of
optical power over a range of up to 4.00 D.
[0016] The present invention will be better understood by reference
to the following detailed discussion of specific embodiments and
the attached figures, which illustrate and exemplify such
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Embodiments of the invention will be understood and
appreciated more fully from the following detailed description in
conjunction with the figures, which are not to scale, in which like
reference numerals indicate corresponding, analogous or similar
elements, and in which:
[0018] FIG. 1A is a schematic cross-sectional view of a first
embodiment of a liquid filled lens for use in spectacles or the
like;
[0019] FIG. 1B is a schematic cross-sectional view of a second
embodiment of a liquid filled lens for use in spectacles or the
like;
[0020] FIG. 2 is an exploded schematic cross-sectional view of an
embodiment of the spectacles apparatus utilizing the liquid filled
lens;
[0021] FIGS. 3A and 3B are graphical software analyses of the
performance of the liquid filled lens; and
[0022] FIGS. 4A and 4B are graphical software analyses of the
performance of the liquid filled lens.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The following preferred embodiments as exemplified by the
drawings are illustrative of the invention and are not intended to
limit the invention as encompassed by the claims of this
application.
[0024] FIG. 1A shows a cross-sectional view of a first preferred
embodiment of the optical apparatus, in the form of a variable
focus lens 10, through which a wearer peers in the direction of
arrow A. Lens 10 is a composite of two optic components, an
anterior (i.e., front, with respect to the wearer) optic 11 that is
substantially rigid and a posterior (i.e., back, with respect to
the wearer) optic 15 that is a liquid.
[0025] Anterior optic 11 is a substantially rigid lens preferably
made of a rigid, transparent substrate, such as a clear plastic or
poly carbonate, glass plate, transparent crystal plate, or a
transparent rigid polymer, for example, Polycarbonate of Bisphenol
A or CR-39 (Diethylene glycol bisallyl carbonate). Anterior optic
11 may be made of an impact resistant polymer and may have a
scratch resistant coating or an antireflective coating.
[0026] In a preferred embodiment, anterior optic 11 has a meniscus
shape, i.e., convex at its front side and concave at its back side.
Thus, both the front and the back surfaces of anterior optic 11 are
curved in the same direction. However, as in all lenses that
correct presbyopia (inability to accommodate), anterior optic 11 is
thicker in the center and thinner at the edge, i.e., the radius of
curvature of the front surface of anterior optic 11 is smaller than
the radius of curvature of the back surface of anterior optic 11,
such that the respective radii of curvature of the front and the
back surfaces of anterior optic 11, and hence the front and the
back surfaces themselves, intersect. The intersection of the front
and the back surfaces of anterior optic 11 is the circumferential
edge 16 of anterior optic 11.
[0027] In certain embodiments, the front surface of anterior optic
11 is spherical, meaning it has the same curve across its entire
surface, as in conventional eyeglasses lenses. In a preferred
embodiment, anterior optic 11 is aspheric and has a more complex
front surface curvature that gradually changes from the center of
the lens out to the edge, so as to provide a slimmer profile and a
desired power profile as a function of the gaze angle, the gaze
angle being defined herein as the angle formed between the actual
line of sight and the principal axis of the lens.
[0028] Posterior optic 15 is a liquid lens composed of a fluid 14.
Fluid 14 is confined within a cavity formed between the back
surface of the anterior optic 11 and a membrane 13 that is attached
to the edges of anterior optic 11. Membrane 13 is preferably made
of a flexible, transparent, water impermeable material, such as
clear and elastic polyolefins, polycycloaliphatics, polyethers,
polyesters, polyimides and polyurethanes, for example,
polyvinylidene chloride films, including commercially available
films, such as those manufactured as Mylar.RTM. or Saran.RTM.. It
has been found that a proprietary clear transparent film made of
Polyethylene terephthalate is one preferred choice for the
membrane.
[0029] The cavity between the back surface of the anterior optic 11
and a membrane 13 in FIG. 1A is formed by sealing membrane 13 to
the periphery or circumferential edge 16 of the anterior optic 11.
Membrane 13 may be sealed to anterior optic 11 by any known method,
such as heat sealing, adhesive sealing or laser welding. Membrane
13 can be is at least in part bonded to a support element that is
in turn bonded to the periphery of anterior optic 11. Membrane 13
is preferably flat when sealed but may be thermoformed to a
specific curvature or spherical geometry.
[0030] Fluid 14 encapsulated between membrane 13 and the back
surface of the anterior optic 11 is preferably colorless. However,
fluid 14 can be tinted, depending on the application, such as if
the intended application is for sunglasses. Fluid 14 having an
appropriate index of refraction and viscosity suitable for use in
fluid filled lenses, such as, for example, degassed water, mineral
oil, glycerin and silicone products, among others that are commonly
known or used for fluid filled lenses. One preferred fluid 14 is
manufactured by Dow Corning.RTM. under the name 704 diffusion pump
oil, also generally referred to as silicone oil.
[0031] In certain embodiments, membrane 13 by itself has no
constraints in its optical properties. In other embodiments,
membrane 13 has constraints in its optical properties, e.g., an
index of refraction, that match the optical properties of fluid
14.
[0032] In use, at least one lens 10 is fit within a set of eyeglass
or spectacle frames for use by a wearer. As shown in FIG. 1A, in
profile, lens 10 allows the user to see through both anterior optic
11 and posterior optic 15, which together provide a thicker profile
at the center of lens 10, and stronger presbyopic visual
correction, than just anterior optic 11. The wearer is provided
with the ability to adjust the amount of fluid 14 within posterior
optic 15 and thereby adjust the refractive power of lens 10. In
certain embodiments, as will be discussed below, the frame is
equipped with a reservoir of excess fluid 14 and a fluid line
communicating the reservoir to the posterior optic 15 of lens 10.
The spectacles frame also preferably has an adjustment mechanism to
allow the wearer to personally adjust the amount of fluid 14 within
posterior optic 15 so that fluid 14 that can be moved into or
expelled from the reservoir into the posterior optic 15 to thereby
adjust the refractive power of lens 10 as needed.
[0033] FIG. 1B shows a cross-sectional view of a second preferred
embodiment of the optical apparatus, in the form of a variable
focus lens 20, through which a wearer gazes in the direction of
arrow A. As opposed to lens 10 in FIG. 1A, which is a composite of
two optic components, lens 20 in FIG. 1B is a composite of three
optic components, namely, an anterior optic 21 that is
substantially rigid, an intermediate optic 25 that is a liquid and
a posterior optic 35 that is a liquid.
[0034] Anterior optic 21 is a substantially rigid lens, similar in
structure and design to that of anterior optic 11 of the embodiment
shown in FIG. 1A. As in anterior optic 11 of FIG. 1A, anterior
optic 21 also has a meniscus shape, i.e., both the front and the
back surfaces of anterior optic 11 are curved in the same
direction, and the radius of curvature of the front surface of
anterior optic 21 is smaller than the radius of curvature of the
back surface of anterior optic 21, such that the intersection of
the front and the back surfaces of anterior optic 21 is the
circumferential edge 26 of anterior optic 21. However, the radius
of curvature of the back surface of anterior optic 21 is larger
than the radius of curvature of the back surface of anterior optic
11 of FIG. 1A. Similarly, as compared to anterior optic 11 of FIG.
1A, anterior optic 21 may be somewhat thinner than anterior optic
11 of FIG. 1A, so as to maintain the same general overall thickness
of lens 20 as compared to lens 10 of FIG. 1A.
[0035] Intermediate optic 25 is a liquid lens composed of a fluid
24, similar to fluid 13 as described with respect to FIG. 1A, that
is confined within a cavity formed between the back surface of the
anterior optic 21 and a membrane 23 that is attached to the edges
26 of anterior optic 21 and is similar in structure and design to
that of membrane 13 of the embodiment shown in FIG. 1A. Fluid 24
has a selected refractive index (n.sub.23).
[0036] It is preferred that intermediate optic 25 also have a
meniscus shape, such that both its front and back surfaces are
curved in the same direction. Naturally, the back surface of rigid
anterior optic 21 may be formed with a curvature during
manufacture. However, the concave curvature of membrane 23 may be
accomplished by thermoforming it to a specific curvature or
spherical geometry when it is being sealed to the edges 26 of
anterior optic 21. This may be accomplished by a reducing the
pressure within the sealed cavity formed between membrane 23 and
the back surface of anterior optic 21. Thus, the radius of
curvature of the back surface of anterior optic 21 is smaller than
the radius of curvature of the membrane 23, and the intersection of
the back surface of anterior optic 21 and membrane 23 is the
circumferential edge 26 of anterior optic 21.
[0037] Posterior optic 35 is a liquid lens composed of a fluid 34,
similar to fluid 13 as described with respect to FIG. 1A, that is
confined within a cavity formed between membrane 23 and a membrane
33. Fluid 34 has a selected refractive index (n.sub.34).
[0038] Membrane 33 has similar in structure and design to that of
membrane 13 described regarding the embodiment shown in FIG. 1A.
Membrane 33 may also be attached to the edges 26 of anterior optic
21 but posterior to, or over the edges of, the attached membrane
23. Alternatively, one or more rings, or half-rings, may be used to
provide a seat for sealing membrane 23 and membrane 33.
[0039] Membrane 33 is preferably flat when sealed but may be
thermoformed to a specific curvature or spherical geometry. In
preferred embodiments, the positive pressure within intermediate
optic 25 is lower than the positive pressure within posterior optic
35. The greater positive pressure within posterior optic 35
controls the shape of membrane 23 and the respective refractive
powers of intermediate optic 25 within the cavity between the back
surface of anterior optic 21 and membrane 23 and of posterior optic
35 within the cavity between membrane 23 and membrane 33.
[0040] In use, at least one lens 20 is fit within a set of eyeglass
or spectacle frames designed for ophthalmic applications for use by
a wearer. As shown in FIG. 1B, in profile, lens 20 allows the user
to see through all of anterior optic 21, intermediate optic 25 and
posterior optic 35, which together provide a thicker profile at the
center of lens 20, and stronger presbyopic visual correction, than
just anterior optic 21. In certain embodiments, the wearer is
provided with the ability to adjust the amount of fluid 24 within
intermediate optic 25 or the amount of fluid 34 within posterior
optic 35, or within both, and thereby adjust the refractive power
of lens 20. In certain embodiments, as will be discussed below, the
frame is equipped with a reservoir of fluid 24 or a reservoir of
fluid 34, or both, and a fluid line connecting the respective
reservoir to the intermediate optic 25 or the posterior optic 35 of
lens 20. The spectacles frame also preferably has one or more
actuators or adjustment mechanisms to allow the wearer to
personally adjust the amount of fluid 24 and fluid 34 within
intermediate optic 25 and posterior optic 35, respectively, so that
fluid 24 and fluid 34 that can be moved into or expelled from the
respective reservoir into the intermediate optic 25 and the
posterior optic 35, and thereby adjust the refractive power of lens
20 as needed.
[0041] Other embodiments of the optical apparatus having even more
optical components are also possible. In addition to lens 10 in
FIG. 1A, which is a composite of one rigid optic and one liquid
optic, and lens 20 in FIG. 1B, which is a composite of one rigid
optic and two liquid optics, the optical apparatus can also be a
composite of one rigid optic and more than two liquid optics. Such
embodiments, which are not shown here, may provide advantages to
the user and may allow more refined and sophisticated ophthalmic
adjustment than the embodiments described in FIGS. 1A and 1B.
[0042] Accordingly, in preferred embodiments, lens 10 or 20 may be
used for applications in eyeglasses. Preferably, the lenses 10 or
20 for the left and the right eye are designed independently and
are capable of adjustment of each eyeglass lens separately by the
wearer. In such a case, it is preferred that a separate liquid
reservoir be in fluid communication with each lens, i.e., connected
to it by its own liquid line. In its most preferred embodiment, the
liquid lens assembly, comprising the liquid lens, the reservoir and
said liquid together constitute a sealed system, thus minimizing
incursion of water or evaporation or leakage of the liquid. The
fluid is driven by some force generated by a user when an
adjustment in power is desired, and is thus be moved into or
expelled from the respective reservoir into the fluid optic. The
mechanism of adjustment of power of the liquid lens is by means of
liquid transfer between the cavity and a reservoir.
[0043] FIG. 2 shows an exploded schematic cross-sectional view of
an embodiment of a set of eyeglasses or spectacles 1 utilizing the
liquid filled lens. Spectacles 1 has a frame or support 5, within
which the variable focus lens is seated. For simplicity, FIG. 2
shows only one (the left) side of a set of spectacles having two
eyeglasses, i.e., one for each eye. In addition, FIG. 2 shows a
variable focus lens having only one fluid optic, e.g., as in lens
10 of FIG. 1A.
[0044] Anterior optic 1 and membrane 13 are seen in the exploded
view of FIG. 2, and reservoir 6, which in fluid communication with
the cavity formed between anterior optic 1 and membrane 13, is
shown. For simplicity, FIG. 2 is described herein with respect to
the embodiment of lens 10 having one fluid optic. In other
embodiments, were spectacles 1 to have more than one fluid optic,
such as in lens 20 of FIG. 1B, more than one reservoir would be
required, each in fluid communication with a respective cavity.
[0045] Reservoir 6, situated in some embodiments attached to or in
frame 5, has a hollow cavity containing extra fluid 14 that can be
injected into lens 10. The extra fluid 14 within reservoir 14
preferably does not completely fill reservoir 6 so as to allow
fluid 14 to be expelled from lens 10 into reservoir 6. Reservoir 6
has a mechanism or actuator to move fluid into or out of expelled
it from the liquid lens optic. In one embodiment, reservoir 6 is
made of a rigid material, and is fitted with a piston that is
mechanically coupled to an adjustment mechanism or actuator, such
as a thumb wheel, a barrel, a clamp or a lever, that may be
attached to the rim or the lens holder, or to a frame attached to
the lens holder. The actuator that provides movement of fluid 14
into or out of reservoir 5 into the cavity is not shown in FIG. 2.
In certain embodiments, once the optical power of lens 10 is
adjusted by the actuator, the actuator may be altered to prevent
further adjustment of the optical properties of lens 10 by the
wearer.
[0046] Reservoir 6 may be connected to a hollow ring (not shown),
previously described, that performs several functions. This ring,
as the seat of the sealed flexible membrane, provides a platform of
defined width and tilt to which membrane 13 is bonded. The ring may
also define the fluid channel, in the form of a hollow space inside
the ring. In one embodiment, the ring, which ring may be set within
the frame or lens support 5, may be provided with a series of
radially placed holes or openings through which the fluid enters
the liquid lens cavity. This series of holes may be placed at
regular angular intervals to deliver the fluid into the cavity at a
controlled rate.
[0047] In the embodiments of spectacles 1 having more than one
fluid optic, such as in lens 20 of FIG. 1B, each liquid lens cavity
is preferably provided with a unique reservoir, and each liquid
lens cavity is preferably provided with a unique ring, so that the
liquid channels remain separate for each cavity.
[0048] The optical and mechanical design of the liquid lens enables
its main function, to provide capability to adjust optical power
over as broad a range as possible without significantly impacting
cosmetic appearance, durability or image quality. A goal of the
design effort is to minimize the volume of the liquid lens,
preferably by reducing its thickness. The thickness of the liquid
lens depends on the radius of curvature of the back surface of the
anterior optic 11 and the diameter of the anterior optic 11.
Therefore, the curve of the back surface of the anterior optic 11
needs to be as large as possible (such that the back surface of the
anterior optic 11 is as flat as possible), consistent with the
specification of optical power to be provided by the anterior optic
11. The specification of the optical power of anterior optic 11 is
based on the range of optical powers for which the liquid lens is
being designed.
[0049] For the range 1.0 D to 5.0 D, for example, the preferred
design configuration is to use a front optic in the power range of
-1.0 D to +0.75 D, more preferably between -0.5 D to +0.5 D, most
preferably 0.0 D with a radius of curvature that is consistent with
optical performance and cosmetics in this range. It is known that
the front curve (radius of curvature) of the rigid anterior optic
11 is related to the range of vision corrections to be provided in
order to achieve optimal field curvature at the far point. For
example, steeper curvatures are used to provide hyperopic
corrections, while flatter curves are used for myopic
corrections.
[0050] The optical principles of selection of base curves are well
known (see for example, M. Jalie, "The Principles of Ophthalmic
Lenses," 4th Edition, Chapter 18, The Association of British
Dispensing Opticians, London, 1988, and I. M. Borish, "Clinical
Refraction," 3rd Edition, Chapter 26, The Professional Press, Inc.,
New York, 1970).
[0051] For refractive corrections in the range of 1.0 D to 5.0 D,
the preferred range of the radius of curvature of the anterior
optic 11 is between 100 to 700 mm depending on the refractive index
of the material used to fabricate anterior optic 11, more
preferably between 500 and 550 mm, the preferred range of thickness
is 0.7 to 2.5 mm, more preferably between 1.0 and 1.5 mm. It is
well known that spherical aberration that affects the effective
power provided by an optic away from its center depends on the
angle of gaze and the power at the center. For a maximum gaze angle
of 20 deg, an optic of 30-40 mm in diameter and for a paraxial
power range of 1.0 D to 5.0 D, the off axis deviation in power is
expected to be about 0.25-0.50 D.
[0052] The preferred embodiment of lens 10 consists of an anterior
optic 11 of zero power, whose thickness is equal to 1.2 mm. The
front surface of anterior optic 11 is preferably aspheric, such
that the power of anterior optic 11 drops by 0.25 D continuously
over a radius of 10 mm. The whole lens 10 has a power equal to 1.21
D at the center, the posterior optic 15, i.e., the liquid layer,
having a thickness of 0.32 mm at the center, the lens diameter of
35 mm, while the radius of curvature of membrane 13 is infinity,
since membrane 13 is bonded flat.
[0053] The power of lens 10 increases when the pressure of the
liquid 14 is increased by injecting more liquid into the cavity
from the reservoir 6. The radius of curvature of membrane 13 is 274
mm when the lens power reaches 3.25 D. 300 microliters of fluid is
required to reach the level of positive pressure required to cause
the required level of deformation (bulging) of membrane 13.
[0054] ZEMAX is a widely-used optical design program sold by Zemax
Development Corporation of Bellevue, Wash. that is used for the
design and analysis of optical systems. Using ZEMAX software, the
inventors were able to test the performance of lens 10 at baseline
as well as over 2.0 D of increased power. FIGS. 3A and 3B show a
ZEMAX software analysis of on-axis (FIG. 3A) and 20 degree off-axis
(FIG. 3B) performance of lens 10 (anterior optic 11 and posterior
liquid optic 15) at baseline. FIGS. 4A and 4B show a ZEMAX analysis
of on-axis ((FIG. 4A) and 20 degree off-axis (FIG. 4B) performance
of lens 10 (anterior optic 11 and posterior liquid optic 15) over
2.0 D of power enhancement. As FIGS. 3 and 4 show, the optical
performance is quite good both on axis and off axis, the difference
between the sagittal and the tangential power being less than 0.1 D
at a gaze angle of 20 deg.
[0055] Thus, a liquid filled lens has been provided. One skilled in
the art will appreciate that the present invention can be practiced
by other than the described embodiments, which are presented for
purposes of illustration and not limitation, and that the invention
is limited only by the claims that follow.
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