Abstract:
An artificial compound eye formed of three layers of membrane bonded to one another in a stacked relationship. A field chamber is located intermediate the two bottommost membranes. A plurality of focus chambers is located intermediate the two topmost membranes, and an image sensor is located below each focus chamber. The field chamber and each focus chamber contain a pressurized fluid medium. The ceilings of the focus chambers function as lenses though which light must pass to reach the sensors. The fluid pressure in the field chamber can be varied to expand or contract the eye between a planer and a domed configuration, thereby allowing the field of view of the eye to be varied. The fluid pressure in each focus chamber can be varied to expand or contract each lens between a planar and a domed configuration for independently varying the focal length of each lens.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Optical lenses have become ubiquitous over the past several decades and are now used in a wide range of applications in a variety of fields, including consumer products (e.g. cameras, camcorders, cellular telephones, telescopes, etc), civilian and military surveillance, optical microsurgery, and endoscopic visualization. A conventional optical lens is typically made of transparent material and has a concave or convex shape that is tailored to suit a specific application. Particularly, a conventional lens is designed with a “focal length” that is generally determined by the curvature of the lens. “Focal length” is the distance over which initially colineated rays of light passing through a lens are brought to a focus (i.e. converged). 
         [0002]    Shortcomings of conventional optical lenses include that the focal length of such a lens is fixed after fabrication. Focusing on objects that are positioned at varying distances from the lens therefore requires physical movement of the lens toward and away from the objects. Furthermore, the field-of-view of the lens is limited and is coupled to the focal length. That is, it is difficult to simultaneously obtain a long working distance and a wide field-of-view. Still further, a single lens component can only focus on a single viewing field at a certain distance from the lens at a given time. As a result, the lens cannot be used to acquire three-dimensional imaging with depth perception in real-time. 
         [0003]    Looking to the natural world, one can find examples of optical lenses that overcome some of the limitations discussed above incorporated into the physiology of various animals. For example, predatory mammalian animals typically have a pair of forward-looking camera eyes, each having a single lens with an adaptively adjustable focal length for obtaining a clear image of objects at various distances. Numerous ocular nerves in the eyes of such animals provide relatively high definition images. However, due to their position and orientation, mammalian camera eyes cannot provide a wide field-of-view. 
         [0004]    In contrast to the camera eyes of mammals, flying insects have compound eyes that are composed of hundreds, and in some cases thousands or millions, of small eyes (ommatidia) that are arranged on a generally spherical underlying structure. In these species, each small eye (ommatidium) has a fixed focal length and is responsible for providing a view of a certain field ahead of it. A single nerve corresponds to each ommatidium and delivers one pixel to the vision process center in the brain of the insect where a complete, unified image is created. Compared to a camera eye, the compound eye usually has poor resolution, which is generally attributable to the poor image processing capability of an insect&#39;s small brain. However, because of the spherical configuration of the compound eye and the resulting orientations of the numerous ommatidia distributed thereon, the eye provides a much wider field-of-view compared to a camera eye. 
         [0005]    The need exists for an optical lens system that overcomes the disadvantages of the prior art and would be suitable for a variety of commercial and non-commercial applications. Specifically, it would be advantageous to provide an optical lens system that features a wide field of view, variably adjustable focal length, high definition images, and is relatively small in size and inexpensive to produce. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    In accordance with the present invention, there is provided an artificial compound eye having a plurality of independently-focusable micro-lenses. The eye is formed of three layers of silicone membrane that are covalently bonded to one another in a stacked, flatly-abutting relationship. The bottom layer of membrane, hereinafter referred to as the substrate membrane, has a circular depression formed in its top surface. A narrow groove is also formed in the top surface of the substrate membrane and intersects and extends away from the circular depression to a fluid inlet that is preferably located adjacent an edge of the membrane. 
         [0007]    The middle layer of membrane, hereinafter referred to as the intermediate membrane, is sealed over both the circular depression and the narrow groove in the top surface of the substrate membrane, thus forming an enclosed, circular fluid chamber, hereinafter referred to as the field chamber, and a microfluidic channel that is in fluid communication with the field chamber. The field chamber and the microfluidic channel contain a fluid medium that is generally kept under pressure by a microfluidic pump that is operatively connected to the fluid inlet. 
         [0008]    A flexible circuit having a plurality of image sensors arranged in a predefined pattern is embedded in the top surface of the intermediate membrane in a substantially parallel relationship therewith. Image data that is captured by the image sensors is transmitted to a central processing unit, preferably by wireless communication means, where the data is used to generate and display a single, cohesive image that represents the total field of view of all of the image sensors. 
         [0009]    The top layer of membrane, hereinafter referred to as the outer membrane, has a plurality of circular depressions formed in its bottom surface in a configuration that is substantially identical to the configuration of the image sensors in the intermediate layer. A plurality of narrow grooves is also formed in the bottom surface of the outer membrane with each groove intersecting and extending away from one of the circular depressions to a fluid inlet that is preferably located adjacent an edge of the membrane. The outer membrane is sealed over the image sensors with each circular depression in the outer membrane aligned with an image sensor in the intermediate membrane, thereby forming a circular fluid chamber, hereinafter referred to as a focus chamber, between each image sensor and the outer membrane. The recessed areas of the outer membrane that form the ceilings of the focus chambers thereby form lenses through which light must pass to reach the image sensors. 
         [0010]    Each narrow groove in the bottom surface of the outer membrane forms a microfluidic channel that is in fluid communication with a corresponding focus chamber. The focus chambers and the microfluidic channels contain a refractive fluid medium that is generally kept under pressure by a plurality of microfluidic pumps that are each operatively connected to the fluid inlet of a channel. 
         [0011]    During operation of the eye, a user can manipulate the microfluidic pump that is connected to the field chamber to increase or decrease the amount of fluid pressure within the chamber, thereby causing the eye to expand or contract between a substantially planar configuration and a convex, domed configuration. When the eye is in a planar configuration, the lenses in the outer membrane and the image sensors in the intermediate membrane are oriented in a generally parallel, forward-looking configuration. When the eye is expanded, the convexity of the eye increases and the lenses and image sensors are moved into an offset, omni-directional configuration. Thus, by varying the fluid pressure in the field chamber, the overall field of view of the eye can be increased or decreased. 
         [0012]    Similarly, a user can manipulate the microfluidic pumps that are connected to the focus chambers to increase or decrease the amount of fluid pressure within each chamber, thereby causing the flexible lenses to expand or contract between a substantially planar configuration and a convex, domed configuration. Thus, by varying the fluid pressure in each focus chamber, the focal length of each lens can be varied for allowing each image sensor to independently focus on objects that are positioned at varying distances from the eye. 
         [0013]    The above-described eye structure therefore allows the field of view of the eye to be tuned independently of the focal length of any of the eye&#39;s lenses. Moreover, because the image sensors of the eye are always oriented perpendicular relative to the axis of the lenses, the eye facilitates a wide field of view without the image distortion that is associated with traditional wide angle lenses. The eye therefore provides the advantages of both camera eyes and compound eyes without the disadvantages associated with either. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view illustrating a preferred embodiment of the present invention. 
           [0015]      FIG. 2  is an exploded view illustrating the preferred embodiment of the present invention shown in  FIG. 1 . 
           [0016]      FIG. 3  is a view in section illustrating the preferred embodiment of the present invention shown in  FIG. 1  with the eye in a planar configuration. 
           [0017]      FIG. 4  is a view in section illustrating the preferred embodiment of the present invention shown in  FIG. 1  with the eye in a domed configuration. 
           [0018]      FIG. 5  is a view in section illustrating the preferred embodiment of the present invention shown in  FIG. 1  with the eye in a domed configuration and several lenses of the eye in various domed configurations. 
           [0019]      FIG. 6  is a top view illustrating a first alternative configuration of the focus chambers and microfluidic channels of the eye. 
           [0020]      FIG. 7  is a top view illustrating a second alternative configuration of the focus chambers and microfluidic channels of the eye. 
           [0021]      FIG. 8  is a top view illustrating a third alternative configuration of the focus chambers and microfluidic channels of the eye that incorporates valves. 
           [0022]      FIG. 9  is a top view illustrating a fourth alternative configuration of the focus chambers and microfluidic channels of the eye that incorporates valves. 
           [0023]      FIG. 10  is a top view illustrating a first alternative embodiment of the flexible circuit of the eye. 
           [0024]      FIG. 11  is a top view illustrating a second alternative embodiment of the flexible circuit of the eye. 
           [0025]      FIG. 12  is a schematic view illustrating a first display image facilitated by the eye. 
           [0026]      FIG. 13  is a schematic view illustrating a second display image facilitated by the eye. 
           [0027]      FIG. 14  is a chart illustrating the convergence of light passing through a lens of the eye when expanded by various fluid pressures. 
           [0028]      FIG. 15  is a graph illustrating a relationship of the focal length of a lens of the eye and fluid pressure that is applied to the lens. 
           [0029]      FIG. 16  is a schematic view illustrating the use of the eye as a means for facilitating real-time, 3D imaging. 
       
    
    
       [0030]    In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific term so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Referring to  FIG. 1 , an artificial compound eye with adaptive microlenses (hereinafter referred to as “the eye”) is indicated generally at  10 . The eye  10  generally includes a substrate membrane  12 , an intermediate membrane  14  bonded to the substrate membrane  12 , and an outer membrane  16  bonded to the intermediate membrane. For the sake of convenience and clarity, terms such as “top,” “bottom,” “up,” “down,” “inwardly,” and “outwardly” will be used herein to describe the relative placement and orientation of various components of the eye  10 , all with respect to the geometry and orientation of the eye  10  as it appears in  FIG. 1 . 
         [0032]    Referring to  FIG. 2 , the substrate membrane  12  is preferably formed of silicone polymer and has an overall thickness of 1000 μm. It is contemplated that substrate membrane  12  can alternatively be formed of any other suitable material, such as glass, plastic, metal, or elastic or resilient polymer, and that the thickness of the substrate membrane  12  can be varied to suit a particular application without departing from the present invention. During fabrication, the substrate membrane  12  is preferably subjected to an etching or casting process whereby a circular depression  18  is formed in the top surface of the substrate membrane  12 . The circular depression  18  is 100 μm deep and has a diameter of 10 mm, although it is contemplated that the dimensions of the depression  18  can be varied. It is further contemplated that the depression  18  can have a shape other than circular, such as oval, rectangular, triangular, or irregular. 
         [0033]    A narrow groove  20  that is preferably shallower than the circular depression  18  is also formed in the top surface of the substrate membrane  12  using an etching or casting process. The groove  20  intersects and extends away from the circular depression  18  to a fluid inlet  22  that is preferably located intermediate the circular depression  18  and an edge of the substrate membrane  12 , although the particular location of the fluid inlet  22  is not critical. While an etching or casting process is preferred for forming the circular depression  18  and the groove  20  in the substrate membrane  12 , it is contemplated that any other suitable method, including, but not limited to, soft lithography, injection molding, hot embossing, and other cutting, molding, or casting methods, can additionally or alternatively be employed. 
         [0034]    Still referring to  FIG. 2 , the intermediate membrane  14  is formed of a layer of polydimethylsiloxane (PDMS) or other suitable material, such as polyurethane, clear acrylic, or parylene. The intermediate membrane  14  has a preferred thickness of 50 μm, although it is contemplated that the thickness of the membrane  14  can be varied. The intermediate membrane  14  has a substantially flat, featureless bottom surface that is adhered to the top surface of the substrate membrane  12  in a flatly abutting relationship therewith. The two parts  12  and  14  are preferably bonded to one another using a conventional covalent bonding process that will be familiar to those of ordinary skill in the art. With the flat bottom surface of the intermediate membrane  14  bonded to the top surface of the substrate membrane  12  thusly, the circular depression  18  in the substrate membrane  12  (described above) forms an enclosed, circular fluid chamber  24  (see  FIGS. 3-5 ), hereinafter referred to as the “field chamber  24 ” (so-called for reasons that will become apparent below), between the membranes  12  and  14 , wherein the intermediate membrane  14  forms a ceiling of the field chamber  24 . Similarly, the groove  20  in the substrate  12  (discussed above) forms an enclosed, microfluidic channel  26  (see  FIG. 1 ) between the parts  12  and  14  that is in fluid communication with the field chamber  24 . 
         [0035]    The field chamber  24  and the microfluidic channel  26  contain a fluid medium that is kept under pressure by a computer controlled, microfluidic pump (not shown) that is operatively connected to the fluid inlet  22 . The fluid medium is preferably mineral oil having a refractive index n=1.4, although it is contemplated that any other liquid medium having a suitable refractive index and viscosity can alternatively be used. It is further contemplated that the fluid medium can alternatively be a pressurized gas. The purpose and operation of the field chamber  24  and the pressurized fluid medium will be described in greater detail below. 
         [0036]    An alternative embodiment of the eye  10  is contemplated in which the circular field chamber  24  and the microfluidic channel  26  are defined by forming a circular depression and a groove in the bottom surface of the intermediate membrane  14  instead of in the top surface of the substrate membrane  12 . In such an embodiment, the top surface of the substrate membrane  12  would be substantially flat and featureless for sealing over the circular depression and the groove in the intermediate membrane  14 . 
         [0037]    Referring to FIGS.  1  and  3 - 5 , a flexible circuit  28  comprising an array of interconnected image sensors  30  is embedded in the intermediate membrane  14  in a substantially coplanar relationship therewith. The image sensors  30  are preferably CMOS or CCD sensors connected by flexible electrical wires, although it is contemplated that various other types of sensors can alternatively be used, including, but not limited to silicon transistors and polythiophene/fullerene sensors. The top surfaces of the sensors  30  (i.e. the surfaces of the sensors  30  that capture images) are preferably coplanar with, and are therefore not covered by, the top surface of the intermediate membrane  14 . It is contemplated that the top surfaces of the sensors  30  can alternatively be recessed from the top surface of the intermediate membrane  14  and, positioned thusly, can optionally be covered by a thin, top layer of the intermediate membrane  14  if the membrane is sufficiently transparent. 
         [0038]    The exemplary embodiment of the eye shown in  FIG. 1  incorporates a total of nine image sensors  30  arranged in a square, 3×3 configuration. However, it is contemplated that the number and configuration of the sensors  30  can be varied without departing from the invention. For example, referring to  FIGS. 10 and 11 , the eye  10  can alternatively include 16 image sensors in a square configuration or 21 image sensors in a concentric, circular configuration. Various other sensor configurations, such as triangular, oval, and irregular configurations, are also contemplated. 
         [0039]    The image sensors  30  are operatively connected to a central processing unit (CPU), such as the general purpose computer  32  shown in  FIG. 16 , by conductors, such as a series of wires  34  that are embedded in, and extend through, the intermediate membrane  14 . The wires  34  transmit image data from the image sensors  30  to the CPU  32  to be processed and displayed (described in greater detail below). Alternatively, it is contemplated that the image data can be transmitted wirelessly between the image sensors  30  and the CPU  32 , such as through a Bluetooth transmitter or other wireless data communication means that is integrated into the flexible circuit  28 . It is further contemplated that the image sensors  30  can communicate the image data to an external wireless communication means through a wired connection, and that the wireless communication means can then wirelessly transmit the image data to a CPU at a remote location. 
         [0040]    Upon being received by the CPU  32 , the image data captured by the several image sensors  30  in the sensor array are digitally “stitched together” using conventional software algorithms that are well known to those of ordinary skill in the art. The resulting output is a contiguous, preferably seamless image that is presented to a viewer, such as on a conventional computer monitor. 
         [0041]    Referring again to  FIG. 2 , the outer membrane  16  is formed of a layer of PDMS or other suitable material, such as those discussed above in the description of the substrate membrane  12 . The outer membrane  16  is 500 μm thick, although it is contemplated that the thickness of the membrane  16  can be varied. Like the substrate membrane  12  described above, the outer membrane  16  is subjected to an etching or casting process during fabrication whereby an array of circular depressions  36  is formed in the bottom surface of the membrane  16 . Each circular depression  36  defines a relatively thin, circular lens  38  in the transparent outer membrane  16 . Each depression  36  is 450 μm deep and has a diameter of 1.5 mm, although it is contemplated that the dimensions of the depressions  36  can be varied depending on the desired size and thickness of the lenses  38 . It is further contemplated that the depressions  36  can have shapes other than circular, such as oval, rectangular, triangular, or irregular. 
         [0042]    The configuration of the lens array, including the spacing between the circular depressions  36 , corresponds to the configuration and spacing of the image sensor array in the intermediate membrane  14  below. Narrow grooves  40  that are preferably shallower than the circular depressions  36  are also formed in the bottom surface of the outer membrane  16  during the lithography process. The grooves  40  intersect, and extend away from, the circular depressions  36  to at least one fluid inlet  42  that is preferably located intermediate the lens array and an edge of the membrane  16 , although the particular location of the fluid inlet  42  is not critical. The configuration of the grooves  40  and the fluid inlet  42  will be described in greater detail below. 
         [0043]    The outer membrane  16  is bonded to the top surface of the intermediate membrane  14  in a flatly abutting relationship therewith using a conventional covalent bonding process. The lens array in the outer membrane  16  is aligned with the image sensor array in the intermediate membrane  14 , with each lens  38  positioned directly above an image sensor  30  as shown in  FIG. 3 . With the bottom surface of the outer membrane  16  bonded to the flat top surface of the intermediate membrane  14  thusly, the circular depressions  36  in the outer membrane  16  (described above) form substantially enclosed, circular fluid chambers  44 , hereinafter referred to as “focus chambers  44 ,” between the lenses  38  and the image sensors  30 . Similarly, the grooves  40  in the outer membrane  16  form enclosed, microfluidic channels  46  (see  FIG. 1 ) between the membranes  14  and  16  that are in fluid communication with the focus chambers  44  to which they extend. 
         [0044]    The focus chambers  44  and the microfluidic channels  46  contain a refractive fluid medium that is kept under pressure by a series of computer controlled, microfluidic pumps (not shown) that are operatively connected to the microfluidic channels  46  at the fluid inlet  42 . The refractive medium is preferably mineral oil (refractive index n=1.4), although it is contemplated that any suitable fluid medium with a refractive index greater than 1.00 can alternatively be used. The purpose and operation of the circular focus  44  chambers and the pressurized refractive medium will be described in greater detail below. 
         [0045]    During normal operation of the eye  10  (described in greater detail below), incoming light passes through each of the lenses  38  in the lens array, as well as through the refractive fluid media contained in the focus chambers  44  between the lenses  38  and the image sensors  30 . The light is then received by the image sensors  30 , where it is converted to an electrical output signal and transmitted to a processing unit in the manner described above. 
         [0046]    The mechanical operation of the artificial compound eye  10  includes two general functions: 1) manipulation of the eye&#39;s total field of view; and 2) manipulation of the focal length of each individual lens  38 . These functions and their respective applications will now be described in detail. 
         [0047]    Manipulation of Field of View (FOV) 
         [0048]    Referring to  FIG. 3 , the artificial compound eye  10  is shown in an unpressurized, planar configuration, wherein the fluid in the circular field chamber  24  is not pressurized, or is only nominally pressurized, by the computer-controlled, microfluidic pump (described above) that is connected thereto. In this configuration, the portion of the intermediate membrane  14  that forms the ceiling of the field chamber  24  and that houses the image sensor array is substantially flat. The image sensors  30  are therefore aligned in a substantially parallel configuration with each sensor  30  pointing directly forward (i.e. perpendicular to the plane of the substrate membrane  12 , or directly up in  FIG. 3 ). The FOV of the compound eye  10  in this configuration is indicated at X, and extends from the leftmost boundary of the FOV of the leftmost image sensor  30  to the rightmost boundary of the FOV of the rightmost image sensor  30 . 
         [0049]    Referring to  FIGS. 4 and 5 , the artificial compound eye  10  is shown in a convex, pressurized configuration, wherein, relative to the planar configuration of the eye  10  shown in  FIG. 3 , a quantity of fluid has been introduced into the field chamber  24  by its corresponding microfludic pump. The introduction of fluid into the field chamber  24  causes the flexible ceiling of the chamber  24  to expand outwardly under pressure, causing the intermediate membrane  14  and the outer membrane  16  to form substantially hemispherical, adjoining domes. In this configuration, the flexible circuit  28  of the image sensor array is also flexed outwardly into a convex shape, resulting in the image sensors  30  pointing in directions that are angularly offset relative to one another, with the degree of offset of each sensor  30  relative to perpendicular (i.e. perpendicular to the plane of the substrate membrane  12 ) increasing as the distance of the sensor  30  from the apex of the domed eye  10  increases. The FOV of the compound eye  10  in this configuration is indicated at Y, and extends from the leftmost boundary of the FOV of the leftmost image sensor  30  to the rightmost boundary of the FOV of the rightmost image sensor  30 . 
         [0050]    Looking at  FIGS. 3 and 4 , it is readily apparent that the FOV Y of the convex, domed configuration of the compound eye  10  is significantly greater than the FOV X of the planar configuration of the eye  10 . This increase is attributable to the outward deflection of the image sensors  30  relative to their orientation in the planar configuration of the eye  10 . A user can thus manipulate the FOV of the artificial compound eye  10  by varying the fluid pressure that is applied to the field chamber  24  by the computer-controlled, microfluidic pump, such as by operating an input means (e.g. buttons, joystick, alphanumeric input, etc) that is provided for accepting such user input. For example, a user may decrease the fluid pressure applied by the microfluidic pump and minimize the FOV of the eye  10  in order to limit his or her view to a particular object or structure captured by the eye  10  while omitting distracting surrounding objects and structures.  FIG. 12  illustrates such a scenario, wherein the user has decreased the convexity (FOV) of the eye  10  in order to limit his view, as presented on the computer monitor  50 , to the building  52 . Alternatively, the user may wish to increase the fluid pressure applied by the microfluidic pump and maximize the FOV of the eye  10  in order to view an object or structure in the context of its surrounding environment. For example, referring to  FIG. 13 , the user has increased the convexity of the eye  10  relative to the scenario illustrated in  FIG. 12  to expand the FOV of the eye  10  in order to view the building  52  as well its surrounding environment. It is contemplated that the manipulation of the FOV of the eye  10  can be partially or fully automated. For example, the operation of the microfluidic pump can be coupled to a motion detection means wherein the microfluidic pump will expand the FOV of the eye  10  (i.e. if further expansion is possible) if the motion detection means detects motion outside of the eye&#39;s then-current FOV. 
         [0051]    Manipulation of Focal Length (FL) 
         [0052]    Referring again to  FIGS. 3 and 4 , each of the lenses  38  of the artificial compound eye  10  is shown in a planar configuration, wherein the fluid in each of the circular focus chambers  44  is not pressurized, or is only nominally pressurized, by the computer-controlled, microfluidic pump (described above) that is connected thereto. In this configuration, the lenses  38  are substantially flat (as in the planar configuration of the eye  10  shown in  FIG. 3 ) or are subtly curved (as in the domed configuration of the eye shown in  FIG. 4 ). When the lenses  38  are substantially flat, the focal length of each lens  38  is infinite or near infinite. That is, initially colineated rays of light that enter each lens  38  are not converged or focused by the lens  38 . The rays of light simply continue through the lens  38  in a generally straight, unaltered path, through the refractive medium and onto the underlying image sensor  30 . 
         [0053]    Referring to  FIG. 5 , the lenses  38  are shown in a variety of convex, pressurized configurations wherein, relative to the substantially planar configuration of the lenses  38  shown in  FIGS. 3 and 4 , a quantity of refractive fluid has been introduced into each of the focus chambers  44  by its respective, microfludic pump, or by a valve (described below). As with the field chamber  24  described above, the introduction of refractive fluid into the focus chambers  44  causes the lenses  38  to expand outwardly under pressure. The convexity of each lens  38  increases as the fluid pressure inside each lens&#39;s respective focus chamber  44  is increased. For example, with regard to the lenses  38  shown in  FIG. 5 , the leftmost lens  38  is subject to the least amount of fluid pressure and therefore exhibits the least convexity. The rightmost lens  38  is subject to a greater amount of fluid pressure than the leftmost lens  38  and therefore exhibits greater convexity. The middle lens  38  is subject to the greatest amount of fluid pressure and therefore exhibits the greatest convexity. As will be appreciated by those skilled in the art, an increase in the convexity of a lens  38  results in a decrease of the lens&#39;s focal length. That is, as the convexity of a lens  38  increases, the distance over which initially colineated rays of light entering the lens  38  are converged decreases. This is illustrated in  FIG. 5 , wherein rays of light  56  entering the most convex, middle lens  38  are completely converged when they reach the image sensor  30 . By contrast, the rays of light  58  entering the less convex, rightmost lens  38  are less converged when they reach the image sensor  30 , and the rays of light  60  entering the least convex, leftmost lens  38  are less converged still when they reach the image sensor  30 . 
         [0054]    This relationship between fluid pressure and focal length is further illustrated in  FIG. 14 , wherein a ray trace method has been employed to show the degree of convergence of a laser beam with a wavelength of 540 nm as it passes through a lens  38  of the eye  10 . It can be seen that as the fluid pressure of the refractive medium in the lens&#39;s focus chamber  44  is increased from zero to a limited value, the focal length can be tuned from +∞ to less than 1 mm. This relationship is further illustrated in the graph shown in  FIG. 15 . It is contemplated that the relationship between the focal length and the fluid pressure can vary with the dimensions of the lens  38 , the focus chamber  44 , and the microfluidic channel  46 , as well as with the particular the refractive medium used. 
         [0055]    A user can thus independently manipulate the focal length of each of the lenses  38  of the eye  10  by varying the fluid pressure that is applied to a lens&#39;s focus chamber  44  by its respective, computer-controlled, microfluidic pump, such as by operating an input means (e.g. buttons, joystick, alphanumeric input, etc) that is provided for accepting such user input. Each lens  38  is connected to its respective microfluidic pump through the microfluidic channel  46 . Two typical arrangements of microfluidic channels for two alternative lens configurations are shown in  FIGS. 6 and 7 . Alternatively, it is contemplated that all of the focus chambers  44  can be connected to a single microfluidic pump, with the pressure in each focus chamber  44  regulated by a valve that is driven by piezoelectric method. Two typical arrangements of such valves are shown in  FIGS. 8 and 9  (the valves are indicated by pairs of opposing arrows). It is contemplated that other suitable arrangements of microfluidic channels and valves can be implemented without departing from the present invention. It is also contemplated that the valves can alternatively be driven by any other physical or chemical actuation methods, such as through the use of using electroactive polymers and bi-morph structures. 
         [0056]    In the preferred embodiment of the invention, the microfluidic pumps of the eye  10  are controlled automatically by digital processing means that employ well known auto-focus techniques. Such processing means can be integrated into the structure of the eye  10  or can be located in close proximity to the eye  10 , or can be located remotely and operatively connected to the eye  10  through wired or wireless communication means. The ability to independently tune the focal length of each individual lens  38  allows the compound eye  10  to simultaneously focus on a plurality of objects at various distances from the eye  10  without moving the eye  10  nearer to or further from the objects. This eliminates the need for cumbersome mechanical structures that are typically employed in traditional camera lenses for enabling physical movement of a lens. 
         [0057]    Advantages of Variable FOV 
         [0058]    The above-described structure and operation of the eye  10  provide distinct advantages over the capability of traditional camera lenses. A first such advantage is that the FOV of the eye  10  is not coupled to any particular focal length. That is, in order to obtain a wide FOV with a conventional, fixed-configuration lens, the lens must be significantly convex with a relatively short focal length. The working distance of the lens is therefore restricted to relatively short distances. By contrast, the FOV of the eye  10  is realized by the arrangement and orientation of the lenses  38  on the variably-domed, intermediate membrane  14  of the eye  10 , and is not substantially affected by variations in the focal lengths of the individual lenses  38 . The eye  10  can therefore provide a wide FOV while one or more of the eye&#39;s lenses  38  are tuned to have long focal lengths and long working distances. 
         [0059]    A second advantage of the eye  10 , and a corollary to the first advantage described above, is an absence of image distortion when the eye  10  is in a wide FOV configuration. That is, traditional wide-angle and fisheye lenses are highly convex and therefore significantly bend incoming light. Light that enters such a lens at points further from the lens&#39;s apex is bent to a greater degree than light that enters the lens at points nearer the lens&#39;s apex. Images produced by such lenses therefore exhibit distortion in the form of severe bowing near the periphery of the image. By contrast, the curvature and corresponding FOV of the eye  10  bear no relationship to the curvature of each of the eyes lenses  38 . Each individual lens  38  is only responsible for capturing the viewable field ahead of it. Incoming light therefore does not have to be bent to an extreme degree in order for the eye  10  to produce wide angle images, thereby facilitating high quality images that do not exhibit distortion. 
         [0060]    Three Dimensional Imaging 
         [0061]    In addition to the benefits described above, the multiple, independently-tunable lenses of the eye  10  facilitate real-time, 3D imaging of objects with accurate depth information. Referring to  FIG. 16 , this is accomplished by bringing a plurality of the eye&#39;s lenses  38  to focus on different areas of an object&#39;s surface by simultaneously tuning the fluid pressure in a plurality of the eye&#39;s focus chambers  44 . After each of the lenses  38  has been brought to focus on a designated area of the object, the measured amount of fluid pressure that is applied to each lens  38  is used to determine the distance between the lenses  38  and the captured areas of the object. The relationship between working distance and fluid pressure is an inverse one, with the fluid pressure in a lens&#39;s focus chamber  44  increasing as the distance between the lens and an object that is brought into focus decreases. The distances between the lenses  38  and the captured areas of the object are thereby computed in real-time by the CPU  32  to which the eye  10  is connected (as described above). The calculated distances are then used to construct a digital, 3D representation of the captured object which is then presented to a viewer as shown in  FIG. 16 . 
         [0062]    Applications 
         [0063]    It is contemplated that the advanced artificial compound eye  10  of the present invention can be applied in many areas where a broad field of view with high resolution is critical. For example, in the biomedical field, this device can be integrated into medical devices such as endoscopes to examine the 3D shape and morphology of target tissues or organs inside human bodies, such as for facilitating diagnoses and surgical processes. It is further contemplated that the inventive eye  10  can be employed in military applications, wherein the eye  10  can be used as a surveillance instrument for wide-field monitoring. Additionally, when used in conjunction with image reconstruction technologies, the motion of target objects can be captured by analyzing image series acquired by the individual lenses  38  of the eye  10 . Such motion capture can be utilized in situations where motion detection plays an important role, such as in determining the real-time positions of missiles or fighter planes. In the consumer products industry, it is contemplated that the inventive eye  10  can be integrated into digital cameras and cellular telephones to enhance the functionality and size/weight characteristics of current products. 
         [0064]    This detailed description in connection with the drawings is intended principally as a description of the presently preferred embodiments of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the designs, functions, means, and methods of implementing the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and features may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention and that various modifications may be adopted without departing from the invention or scope of the following claims.