Technical Field of the Invention
The present invention relates to a membrane-less liquid lens whose focal
length can be varied by manual actuation. More particularly the present invention
relates to an imaging device housing the membrane-less liquid lens wherein the focal
length of liquid lens can be varied by manual actuation5 .
Background of Invention
Lenses ranging from diverging to converging type are ubiquitous in optical
devices such as cameras, telescopes, and microscopes. Typically, lenses used in
optical devices are of fixed shape and therefore, their focal length is fixed.
10 Consequently, optical devices require relative movement between fixed-focal length
lenses to focus upon the desired object. Such an arrangement results in bulky lens
assemblies, which precludes their application for miniaturized optical systems such
as those used in mobile phones and surveillance systems. This drawback of
conventional lenses can be overcome using deformable liquid (or fluidic) lenses.
15 Liquid lenses use liquids as the refracting media. The focal length of liquid lenses
can be varied by varying the curvature of the lens. Unlike conventional optical
systems which require varying distance between fixed-focal length lenses, liquid
lenses give same functionality by varying the curvature and eliminating relative
movement between the lenses.
20 Various types of liquid lenses are known in the art of, which can be classified
into two broad categories:
(i) those consisting of a transparent, elastic membrane, and
(ii) membrane-less designs.
In liquid lenses consisting of a membrane, liquid is kept in a transparent
25 chamber having, at least, one optically clear elastic membrane as the chamber
3
boundary. The curvature of the membrane is changed either by pumping liquid in or
out of the chamber or by increasing the pressure inside the chamber which deforms
the elastic membrane. When the liquid is injected into the chamber, the increase in
pressure causes the elastic membrane to attain a convex shape. Whereas, when liquid
is removed from the chamber, the membrane attains a concave shape. Consequently5 ,
liquid lenses with membranes can be used for different lens configurations, including
biconvex, biconcave, plano-convex, and plano-concave type. Moreover, these lenses
have large tuning range. Several patents and devices are known in the art that
provide liquid membrane lenses. A few such devices and lenses are described in US
10 7672059, US7948683 US8064142 and US 9030751.
However, the disadvantage of membrane-type liquid lenses is that the lens
profile is determined only by the mechanical properties of the elastic membrane.
Further use of elastic membrane limits the reliability of the membrane due to
physical imperfections and degradation over time. Moreover, membrane-type lenses
15 are sensitive to the orientation as gravity effects can cause the lens to acquire
asymmetric shape, which deteriorates the optical performance.
As opposed to this the membrane-less liquid lenses do not employ an elastic
membrane to contain the liquid. These types of liquid lenses employ at least two
immiscible, optically clear liquids. The curvature of the interface between the
20 immiscible liquids is varied to change the focal length of the lens. In such liquidliquid
lenses, the adverse effects of gravity can be eliminated by choosing two
liquids with equal densities. This makes membrane-less liquid lenses robust to the
orientation, compared with membrane-type lenses. A few such lenses are described
in WO2006027522, EP2085796, US20070002455 and WO2008062067
25 Different actuation mechanisms are taught in the prior art for affecting a
change in the curvature of liquid-liquid interface in membrane-less liquid lenses such
as electrowetting or mechanical actuation. Electrowetting phenomenon enables
4
variation of contact angle of liquids on a non-conductive surface by applying a
potential difference between the liquid and the surface. The drawback of
electrowetting lens is that it typically requires a relatively high voltage of order
100 V and also electrowetting lenses often suffer from electrolysis, joule heating,
and bubble formation due to applied electric fields5 .
To eliminate the drawbacks of electrowetting lenses, mechanical actuation of
membrane-less liquid lenses has been proposed. The fundamental principle of a
membrane-less liquid lens based on mechanical actuation is that the interface
between two immiscible fluids is pinned at a point where geometry and/or
10 wettability changes abruptly. Such membrane-less liquid lenses retain the benefits of
ultra-smooth liquid-liquid interface and negligible gravity effects. Unlike
electrowetting lenses, the interface between two immiscible liquids is held by a
capillary barrier created by an abrupt area-variation and/or change in surface
wettability. The three-phase contact line between the two liquids and the solid
15 surface pins at the sharp edge of the solid substrate and/or at the point of change in
surface wettability. Variation of pressure or volume of the liquids leads to a change
in the curvature of liquid-liquid interface, and hence the focal length. The pinning of
the interface also ensures that the lens is self-centered on the optical axis, which is
not the case in electrowetting lenses. Certain membrane-less liquid lenses are
20 described in US7436598, US 20080259463, US7898742 and Oku, H., & Ishikawa,
M. (Applied Physics Letters, Vol 94, 221108, 2009).
The existing designs and actuation mechanisms of membrane-less liquidliquid
lenses involve either deformable lens walls, piezoelectric transducers,
ferrofluids actuated by a magnetic field, or thermoresponsive hydrogels to apply
25 pressure on the liquids. Consequently, these lens designs are relatively complex and
expensive in construction. Moreover, the additional complexity associated with
deformable lens walls, piezoelectric transducers, ferrofluids, or thermoresponsive
5
hydrogels makes membrane-less liquid-liquid lenses less robust. These issues can
limit the application of such lenses in low-cost camera devices including webcams
and low-end camera phones. Therefore to overcome the above said problems in the
prior art there is a need in the art for a membrane-less liquid lens which is simple in
construction and can be operated manually5 .
The present invention overcomes the above-mentioned problems associated
with the existing membrane-less liquid lens and provides a membrane-less liquid
lens which is simple in construction, non-expensive and can be actuated manually.
Objects of the Invention
10 An object of the present invention is to overcome the problems in the art.
Another object of the present invention is to provide a membrane-less,
variable focal length, fluid/liquid lens which can be actuated manually.
Yet another object of the present invention is to provide a membrane-less,
variable focal length, liquid lens which can be actuated manually by altering the
15 curvature of liquid-liquid interface by pinning the contact line at the edge of a solid
substrate and manually varying the pressure on one side of the interface.
Yet another object of the present invention is to provide a simple variable
focal length liquid lens which can be actuated manually using a linear actuator such
as a screw or a piston.
20 Yet another objective of the invention is to vary the focal length of a
membrane-less, variable focal length, liquid lens without varying the aperture.
Another object of the present invention is to provide a low-cost and robust
variable focal length liquid lens.
6
Yet another object of the present invention is to provide an imaging device
housing a membrane-less, variable focal length, liquid lens which can be actuated
manually.
These and other objects of the present invention are achieved in the preferred
embodiments disclosed below by providing a membrane-less liquid lens which ca5 n
be actuated manually.
Summary of the Invention
According to an embodiment the present invention provides a membrane-less
variable focus liquid lens (100) comprising, a top chamber (001); a bottom chamber
10 (002); an opening between the said chambers being a lens aperture (003); an air
cavity (004); a linear mechanical actuator (005); the said chambers containing
immiscible liquids having different refractive indices, and encased in a chamber wall
(006) parallel to the optical axis; an optically clear top window (007) perpendicular
to the optical axis; an optically clear bottom window (008) perpendicular to the
15 optical axis; wherein the said linear mechanical actuator alters the curvature of
interface (0017) of the said liquids pinned at the aperture.
In another embodiment the present invention relates to process of imaging
using membrane-less variable focus liquid lens comprising: top chamber (001); a
20 bottom chamber (002); an opening between the said chambers being a lens aperture
(003); an air cavity (004); a linear mechanical actuator (005); the said chambers
containing immiscible liquids having different refractive indices, and encased in a
chamber wall (006) parallel to the optical axis; an optically clear top window (007)
perpendicular to the optical axis; an optically clear bottom window (008)
25 perpendicular to the optical axis; wherein the process involves the steps of causing
the light rays to be incident on the said aperture and controlling motion of the said
7
linear mechanical actuator for altering the curvature of interface (0017) of the said
liquids pinned at the aperture resulting in the actuation of the focal length of the lens
to obtain an image.
In an embodiment the present invention relates to an imaging devic5 e
comprising of an image sensor (0016) and a membrane-less variable focus liquid
lens (100) comprising: a top chamber (001); a bottom chamber (002); an opening
between the said chambers being a lens aperture (003); an air cavity (004); a linear
mechanical actuator (005); the said chambers containing immiscible liquids having
10 different refractive indices, and encased in a chamber wall (006) parallel to the
optical axis; an optically clear top window (007) perpendicular to the optical axis; an
optically clear bottom window (008) perpendicular to the optical axis; wherein the
process involves controlling motion of the said linear mechanical actuator for
altering the curvature of interface (0017) of the said liquids pinned at the aperture
15
Brief description of the accompanying drawings:
Some of the objects of the invention have been set forth above. These and
other objects, features, aspects and advantages of the present invention will become
better understood with regard to the following description, appended claims and
20 accompanying drawings where:
Figure 1 illustrates a sectional view of the membrane-less liquid lens.
Figure 2 illustrates sectional three-dimensional view of the membrane-less
liquid lens
Figure 3 illustrates sectional view of the membrane-less liquid lens with a
25 screw as the linear mechanical actuator which can be used for manual actuation of
the membrane-less liquid lens.
8
Figure 4 illustrates sectional view of the membrane-less liquid lens with a
piston cylinder as the linear mechanical actuator which can be used for manual
actuation of the membrane-less liquid lens.
Figure 5 illustrates sectional view of the membrane-less liquid lens with a
piston cylinder with crankshaft as the linear mechanical actuator which can be use5 d
for manual actuation of the membrane-less liquid lens.
Figure 6 illustrates the operation of the membrane-less liquid lens as a
converging lens using ray diagram wherein the linear actuator is moved into the
bottom chamber and the top fluid has lower refractive index than the bottom fluid
10 Figure7 illustrates the operation of the membrane-less liquid lens as a
converging lens using ray diagram when the linear actuator is moved out of the
bottom chamber and the top fluid has lower refractive index than the bottom fluid
Figure 8 illustrates operation of the membrane-less liquid lens as a diverging
lens using ray diagram wherein the linear actuator is moved into the bottom chamber
15 and the top fluid has higher refractive index than the bottom fluid
Figure 9 illustrates operation of the membrane-less liquid lens as a diverging
lens using ray diagram wherein the linear actuator is moved out of the bottom
chamber and the top fluid has higher refractive index than the bottom fluid.
Figure10 illustrates an imaging device housing membrane-less liquid lens.
20 Detailed Description of the Invention and accompanying drawings:
The present invention will be described with respect to preferred
embodiments. The invention is not limited thereto but only by the claims.
9
In one embodiment the present invention relates to a membrane-less liquid
lens (100).Figure 1 illustrates a front cross-sectional view of the membrane-less
liquid lens and Figure 2 illustrates sectional three-dimensional view of the
membrane-less liquid lens. As illustrated in Figures 1 and 2, the assembly of the
liquid lens consists of plurality of chambers, essentially a top chamber (001) and 5 a
bottom chamber (002) the said chambers are encased in a chamber wall (006) with
plurality of windows at top and bottom lateral walls of the chamber. Essentially the
top chamber (001) consists of an optically clear top window (007) at the lateral
chamber wall (009) and bottom chamber (002) consists of an optically clear bottom
10 window (008) at the distal chamber wall (0010).The chambers contain immiscible
liquids having different indices of refraction and are encased in a chamber wall (006)
parallel to the optical axis. The said chambers are separated by a partition with an
aperture (003).The aperture between the chamber containing liquids may possibly be
of multiple shapes, i.e. circular to make a spherical lens, a rectangular slit to make a
15 cylindrical lens. The assembly also comprises of an air cavity (004) and linear
mechanical actuator (005) for manual actuation of the aperture.
The top window (007) and the bottom window (008) of the lens module are
perpendicular to the optical axis and are made of optically clear material. The lens
20 chambers are filled with two immiscible liquids having different indices of
refraction. The volume of the said two immiscible liquids is chosen such that the
interface (0017) between these two immiscible liquids gets pinned to the sharp edge
of the aperture.
25 Pinning here refers to the fixed interface at the sharp geometrical edge. When
the three-phase contact line formed between the two liquids and the surface touches a
sharp edge, it does not move upon change in pressure on one or both sides of the
liquid-liquid interface. Instead, the curvature of the liquid-liquid interface changes
10
upon change in pressure on one or both sides of the interface while the three-phase
contact line remains attached to the sharp edge. The phenomenon is known as
pinning.
In one embodiment for manual actuation of the said assembly, a linea5 r
mechanical actuator (005) is provided in the bottom chamber (002) which can be
manually moved in or out of the chamber. When the linear mechanical actuator is
moved in or out the pressure of the bottom a liquid/gas changes which changes the
curvature of interface (0017) pinned at the aperture. This changes the focal length of
10 the lens. Further the lens assembly also comprises of a narrow air cavity (004) that
compensates for the change (increase or decrease) in the volume of the top chamber
when the liquid-liquid moves (downwards or upwards).
The present invention also teaches that the thickness of the air cavity (004) is
15 significantly smaller than the capillary length of the top liquid. This eliminates the
effect of gravity on the interface between air and top liquid.
The linear mechanical actuator (005) in the present lens design can be
selected from the known linear actuators in the prior art which can move in or out of
20 the lens cavity by manual actuation. Figures 3-5 illustrate various embodiments of
linear mechanical actuators which can be used in the present invention. Figure 3
illustrates the bottom lens cavity (002) in which a screw is employed as a linear
actuator. The screw can be moved in or out of the lens cavity by turning it manually.
Figure 4 illustrates another embodiment of actuating the lens by employing a piston25
cylinder arrangement. The piston is moved inside the cylinder which changes the
pressure in bottom chamber of the lens. In another embodiment, shown in Figure 5,
illustrates yet another embodiment wherein the linear mechanical actuators is a
11
piston attached to a crankshaft for converting rotational motion to linear motion of
the piston.
The said assembly and the chambers can be made of any material selected
from metals, alloys, glass or polymers provided that the chamber material does no5 t
react with the lens liquids. The top and bottom windows can be made from any
optically clear material selected from glass or polymers.
The requirements for choosing the two liquids in the top and bottom
10 chambers of the said lens are:
(i) the liquids should be immiscible,
(ii) their refractive indices should be different, and
(iii) the densities of the two liquids should be close to each other, preferably
equal.
15
In one embodiment of the present invention one of the liquids in the chamber
can be selected from the group containing paraffin oil, silicone oil, glycerol, 1-
bromododecane, and 1-chloronapthalene, Santolight™ SL-526 (refractive index
1.67), Cargille BK7 Matching Fluid(refractive index 1.52) while the liquid in the
20 other chamber can be water (refractive index 1.33) with or without dissolved salt.
Another pair of liquids employed in the chambers is hydrocarbon oil and fluorinated
oil. The immiscibility of the liquids in the two chambers is necessary to have a sharp
interface. The difference between refractive indices of the liquids should preferably
be large to get a large variation in focal length upon moving the linear mechanical
25 actuator.
12
Further it is essential that the gas in the air cavity should be such that it does
not react with the top liquid. For example, the air cavity can be filled with air and the
top liquid can be paraffin oil.
In an embodiment the present invention also relates to imaging devic5 e
comprising of an image sensor (0016) and membrane-less variable focus liquid lens
(100) comprising a top chamber (001), a bottom chamber (002), an opening between
the said chambers being a lens aperture (003), an air cavity (004), a linear
mechanical actuator (005); the said chambers containing immiscible liquids having
10 different refractive indices, and encased in a chamber wall (006) parallel to the
optical axis; an optically clear top window (007) perpendicular to the optical axis; an
optically clear bottom window (008) perpendicular to the optical axis; wherein the
process involves the steps of causing the light rays to be incident on the said aperture
and controlling motion of the said linear mechanical actuator for altering the
15 curvature of interface (0017) of the said liquids pinned at the aperture resulting in the
actuation of the focal length of the lens to obtain an image.
The light rays enter the lens from either top or bottom window and leave
from the other side. Figures 6-9 illustrate the working of liquid lens, wherein the lens
20 can be employed as a lens as a converging lens or as a diverging lens.
In one embodiment the present invention relates to the lens as a converging
lens as illustrated in Figure 6 and 7. Figure 6 illustrates the linear mechanical
actuator moved into the lens chamber and Figure 7 illustrates the linear mechanical
25 actuator moved out of the lens chamber. The lens acts as a converging lens when the
liquid in the top chamber has lower refractive index compared with the liquid in the
bottom and the interface (0017) shape is convex upwards. The process of imaging
involves the step of causing light rays (0011) to be incident on the aperture (003) and
13
controlling motion of the said linear mechanical actuator (005) for altering the
curvature of interface (0017) of the said liquids pinned at the aperture resulting in the
actuation of the focal length of the lens to obtain an image.
In one embodiment the present invention teaches imaging with the said len5 s
wherein the linear mechanical actuator (005) is moved into the lens chamber (Figure
6) resulting in the curvature of the liquid-liquid interface (0017) being convex
upwards. Therefore, the parallel light rays entering from below converge to a focal
point (0012) above the interface (0017) to obtain an image.
10
In another embodiment the present invention teaches imaging with the said
lens (100) wherein the linear mechanical actuator (005) is moved out of the lens
chamber (Figure 7) resulting in the reduction of curvature of the interface (0017)
resulting the increase in the focal length, therefore converging to a focal point (0013)
15 further above the interface (0017) to obtain an image.
In another embodiment the present invention relates to the lens as a diverging
lens as illustrated in Figure 8 and 9. Figure 8 illustrates the linear mechanical
actuator (005) moved into the lens chamber and Figure 9 illustrates the linear
20 mechanical actuator moved out of the lens chamber. The lens acts as a diverging lens
when the liquid in the top chamber has higher refractive index compared with the
liquid in the bottom and the interface (0017) shape is convex upwards. The process
of imaging involves the step of causing light rays (0011) to be incident on the
aperture (003)and controlling motion of the said linear mechanical actuator for
25 altering the curvature of interface (0017) of the said liquids pinned at the aperture
resulting in the actuation of the focal length of the lens to obtain an image.
14
In one embodiment the present invention teaches imaging with the said lens
(100) wherein the linear mechanical actuator (005) is moved into the lens chamber
(Figure 8) resulting in the curvature of the liquid-liquid interface (0017) being
convex upwards. Therefore, the parallel light rays entering from below diverge from
a focal point (0014) below the interface (0017) to obtain an image5 .
In another embodiment the present invention teaches imaging with the said
lens (100) wherein the linear mechanical actuator is moved out of the lens chamber
(Figure 9) resulting in the reduction of curvature of the interface (0017) resulting in
10 the increase in the focal length, therefore diverging to a focal point (0015) further
below the interface (0017) to obtain an image.
In another embodiment the lens (100) can acts as a converging lens when the
interface (0017) shape is concave upwards and the refractive index of the top liquid
15 is higher than the refractive index of the bottom liquid.
In another embodiment the lens (100) can acts as a diverging lens when the
interface (0017) shape is concave upwards and the refractive index of the top liquid
is lower than the refractive index of the bottom liquid.
20
In an embodiment the present invention relates to an imaging device as
illustrated in Figure 10, housing the membrane-less liquid lens (100) comprising a
top chamber (001), a bottom chamber (002), an opening between the said chambers
being a lens aperture (003), an air cavity (004), a linear mechanical actuator (005);
25 the said chambers containing immiscible liquids having different refractive indices,
and encased in a chamber wall (006) parallel to the optical axis; an optically clear top
window (007) perpendicular to the optical axis; an optically clear bottom window
(008) perpendicular to the optical axis; wherein the process involves controlling
15
motion of the linear mechanical actuator for altering the curvature of
interface(0017)of the said liquids pinned at the aperture resulting in the actuation of
the focal length of the lens to obtain an image. The said device as illustrated in
Figure 10 comprises an image sensor (0016), such as charge coupled device (CCD)or
complementary metal-oxide-semiconductor (CMOS), and an assembly of at least on5 e
membrane-less liquid lens.
In another embodiment the present invention also relates to a compound lens
wherein a plurality of fixed-focal length lenses is used along with at least one
10 assembly of the membrane-less liquid lens to form a compound lens. Such a
compound lens consisting of at least one membrane-less liquid lens is placed in front
of the image sensor to form an image on the image sensor. The focal length of the
membrane-less liquid lens is varied by moving the linear mechanical actuator,
leading to a change in the object range.
15
For liquids with identical densities, the interface between the two liquids does
not deform due to gravity or any other acceleration. Otherwise, the size of the
aperture should be smaller than the capillary length corresponding to the two liquids,
defined as:
20
1/ 2
2 1 (g / ((r − r )g )) .
Here, g is the interfacial tension, 2 r is the density of denser of the two
liquids, 1 r is the density of the less dense liquid, and g is the acceleration due to
25 gravity.
16
This requirement is invariably satisfied if the present invention is used for
making a miniature lens. The aperture diameter of the lens should be smaller than the
capillary length. In case both the liquids have same density, then the capillary length
is infinite and hence any aperture diameter can be used. The screw diameter can also
be chosen as per size requirements5 .
Wetting properties of two chambers may be similar or different, by
controlling the wetting properties of two chambers independently; the range of focal
length can be increased. For imaging with the lens wherein the bottom chamber has
10 water and the top chamber has oil, hydrophobic properties of top chamber and
hydrophilic properties of bottom chamber facilitate an enhanced pinning of the
interface, allowing the curvature of the interface to be deformed more. The chamber
walls will have contact angle of 1 with the liquid in bottom chamber, interface
deforming until the contact angle between bottom liquid and top chamber reaches1
+ 90o. Similarly if the contact angle is 1and 15 2 with the bottom and top chambers
respectively, the interface remains pinned until the contact angle becomes 2 + 90o.
In another embodiment, the linear actuator can be driven by an electric
motor. The said motor assists in increasing the temporal rate at which lens focal
20 length can be varied.
The invention is now being further explained by way of non-limiting examples:
Example 1: The lens chamber was machined out of acrylic and the top and
25 bottom windows were also made of acrylic. These layers were assembled with the
help of three nut and bolts. The diameter of the aperture was 4 mm and the screw
diameter was 3 mm. The bottom liquid (on the side of the screw) was deionized
17
water (refractive index 1.33) and the top liquid was paraffin oil (refractive index
1.486).
Example 2: The size of the aperture was kept smaller than the capillary
length, defined as5 :
1/ 2
2 1 (g / ((r − r )g )) .
where, g is the interfacial tension, 2 r is the density of denser of the two
liquids, 1 r is the density of the less dense liquid, and g is the acceleration due to
gravity.
10
When, 3 g 50 10
−
= × N/m, 2 1 r −r =100 kg/m3, and g = 9.8 m/s2the capillary
length as defined by the equation above was approximately 7 mm. The miniature
lenses with aperture of order 1 mm, the capillary length was significantly larger. For
miniature lenses, the interface between the two liquids does not deform even when
15 the densities of liquids do not match exactly.
Example 3: A lens chamber was machined out as illustrated in example 1
and example 2,for imaging with the lens the bottom chamber was filled with water
and the top chamber was filled with oil, wherein the contact angle formed was 10o
with bottom chamber and 70o 20 with top chamber, range of change in contact angle
was 10o to 160o. Thus the interfacial shape was varied from concave to convex to
provide change in the focal length of the lens. The diameter of aperture was 4 mm,
the radius of curvature of interface changed from -11.3 mm to 1.23 mm, the negative
sign represents the concave-upwards shape of the interface.
25
The present invention provides following listed advantages over the prior art:
18
1) The lens design is simple in construction and can be operated manually.
2) The present invention is low-cost and robust compared with other
membrane-less liquid lenses as it avoids relatively complex and
expensive actuation mechanisms based on deformable lens walls,
electrowetting, ferrofluids, piezoelectric actuators, electricity operate5 d
pumps, and thermosensitive hydrogel. The lens of the present invention
can, therefore, give the performance of membrane-less liquid lenses with
relatively simple construction and manual actuation. This makes the
present invention more suitable for low-cost optical devices, such as
10 webcams and low-end camera phones.
3) The deformable boundary between the two liquids in the present
invention is smooth and devoid of any physical imperfections compared
with elastic membranes used in membrane-type liquid lenses. Moreover,
by choosing liquids with identical densities, lens of the present invention
15 becomes completely insensitive to the orientation.
4) Compared with electrowetting lens, the present invention has no
limitations regarding the electrical conductivity of the liquids. Therefore,
a wider choice of liquids is available for making the lens.
A membrane-less variable focus liquid lens as described above. The
20 invention is capable of other embodiments and of being practiced and carried out in
other ways without departing from its scope. The phrases and terminology used
herein are for the purpose of description and may not be construed as being limiting.
Furthermore, the foregoing description of the embodiments and the best mode of
practicing are provided for the purpose of illustration only and not for the purpose of
25 limitation, the invention being identified in the claims.

We Claim:
1. A membrane-less variable focus liquid lens (100) comprising
a top chamber (001);
a bottom chamber (002);
an opening between the said chambers being a lens aperture (003)5 ;
an air cavity (004);
a linear mechanical actuator (005);
the said chambers containing immiscible liquids having different refractive
indices, and encased in a chamber wall (006) parallel to the optical axis;
10 an optically clear top window (007) perpendicular to the optical axis;
an optically clear bottom window (008) perpendicular to the optical axis;
wherein the said linear mechanical actuator alters the curvature of
interface(0017) of the said liquids pinned at the aperture.
2. 15 The membrane-less variable focus liquid lens as claimed in claim 1, wherein
the thickness of the said air cavity (004) is smaller than the capillary length of
the top liquid.
3. The membrane-less variable focus liquid lens as claimed in claim 1, wherein
20 the said linear mechanical actuator is selected from the group of screw, piston
cylinder and piston cylinder with crankshaft and the like.
4. The membrane-less variable focus liquid lens as claimed in claim 1, wherein
the lens is converging or diverging type.
25
5. The membrane-less variable focus liquid lens as claimed in claim 1, wherein
the liquids filling the top chamber (001) and bottom chamber (002) have
substantially similar density.
20
6. The membrane-less variable focus liquid lens as claimed in claim 1, wherein
the inner surfaces of top chamber (001) and bottom chamber (002) have
different wettability.
7. The membrane-less variable focus liquid lens as claimed in claim 1, wherei5 n
the said immiscible liquids in the chambers have refractive indices in the
range of about 1.33 to 1.67.
8. The membrane-less variable focus liquid lens as claimed in claim 1, wherein
10 the said air cavity (004) is filled with a gas or a mixture of gases which does
not react with the fluid filled in the top chamber (001).
9. A process of imaging using membrane-less variable focus liquid lens
comprising:
a. 15 a top chamber (001);
b. a bottom chamber (002);
c. an opening between the said chambers being a lens aperture (003);
d. an air cavity (004);
e. a linear mechanical actuator (005);
f. 20 the said chambers containing immiscible liquids having different refractive
indices, and encased in a chamber wall (006) parallel to the optical axis;
g. an optically clear top window (007) perpendicular to the optical axis;
h. an optically clear bottom window (008) perpendicular to the optical axis;
wherein the process involves the steps of causing the light rays to be incident
25 on the said aperture and controlling motion of the said linear mechanical
actuator for altering the curvature of interface (0017) of the said liquids
pinned at the aperture resulting in the actuation of the focal length of the lens
to obtain an image.
21
10. An imaging device comprising of an image sensor (0016) and a membraneless
variable focus liquid lens (100) comprising:
a. a top chamber (001);
b. a bottom chamber (002)5 ;
c. an opening between the said chambers being a lens aperture (003);
d. an air cavity (004);
e. a linear mechanical actuator (005);
f. the said chambers containing immiscible liquids having different refractive
10 indices, and encased in a chamber wall (006) parallel to the optical axis;
g. an optically clear top window (007) perpendicular to the optical axis;
h. an optically clear bottom window (008) perpendicular to the optical axis;
wherein the process involves controlling motion of the said linear mechanical
actuator for altering the curvature of interface (0017) of the said liquids
15 pinned at the aperture
11. The imaging device as claimed in claim 10, wherein the membrane-less
variable focus lens is used along with an assembly of other lenses with fixed
or variable focal length to form a compound lens.