Abstract:
An electro-active spectacle lens is disclosed. The spectacle lens comprises a first substrate having a first outer region and first inner region, a first electrode layer disposed adjacent to the first inner region, the first electrode layer including an outer electrode region having a first conductivity and an inner electrode region having a second conductivity, the first conductivity being greater than the second conductivity, a second substrate having a second outer region and second inner region, a second electrode layer disposed adjacent to the second inner region, the second electrode layer having a third conductivity, and an electro-active cell disposed between the first electrode layer and the second electrode layer, the electro-active cell containing an electro-active material. The first outer region and second outer region are configurable for fitting the spectacle lens within a lens frame without altering the electro-active cell.

Description:
[0001]     The present application claims priority to U.S. Provisional Application No. 60/536,238 filed Jan. 14, 2004. This application is also a continuation-in-part of U.S. patent application Ser. No. 10/664,112 filed Aug. 20, 2003, which claims the benefit of U.S. Provisional Application No. 60/404,657 filed Aug. 20, 2002. U.S. patent application Ser. No. 10/664,112 is also a continuation-in-part of U.S. patent application Ser. No. 10/422,128 filed Apr. 24, 2003, which claims the benefit of U.S. Provisional Application No. 60/375,028, filed Apr. 25, 2002, and which is a continuation-in-part of U.S. patent application Ser. No. 10/387,143, filed Mar. 12, 2003, which claims the benefit of U.S. Provisional Application Nos. 60/363,549, filed Mar. 13, 2002 and 60/401,700, filed Aug. 7, 2002, and which is a continuation-in-part of U.S. patent application Ser. No. 10/281,204, filed Oct. 28, 2002 and Ser. No. 10/046,244, filed Jan. 16, 2002. U.S. patent application Ser. No. 10/281,204 is a continuation of U.S. Pat. No. 6,491,394, filed Jun. 23, 2000. U.S. patent application Ser. No. 10/046,244 claims the benefit of U.S. Provisional Application Nos. 60/261,805, filed Jan. 17, 2001, 60/331,419, filed Nov. 15, 2001, and 60/326,991, filed Oct. 5, 2001, and is a continuation-in-part of U.S. Pat. No. 6,491,391, filed Jun. 23, 2000, U.S. Pat. No. 6,491,394, filed Jun. 23, 2000, and U.S. Pat. No. 6,517,203, filed Jun. 23, 2000, and U.S. Pat. No. 6,619,799, filed Jun. 23, 2000, all of which claim priority to U.S. Provisional Application Nos. 60/142,053, filed Jul. 2, 1999, 60/143,626, filed Jul. 14, 1999, 60/147,813, filed Aug. 10, 1999, 60/150,545, filed Aug. 25, 1999, 60/150,564, filed Aug. 25, 1999, and 60/161,363, filed Oct. 26, 1999. All of the foregoing applications, provisional applications, and patents are herein incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Modal liquid crystal lenses are switchable lenses with a continuous phase variation across the lens. Modal liquid crystal lenses have been described, for example, by A. F. Naumov in a publication entitled Control Optimization Of Spherical Modal Liquid Crystal Lenses, published in Optics Express (26 Apr. 1999 vol. 4, No 9). The basic design of a modal liquid crystal lens, according to Naumov, is illustrated in  FIGS. 1   a  and  1   b.    FIG. 1   a  is a planar view of an illustrative electrode layer used in a modal liquid crystal lens, and  FIG. 1   b  is a side sectional view of an illustrative modal liquid crystal lens. As shown in  FIGS. 1   a  and  1   b,  modal liquid crystal lens  100  includes a control electrode  130 , which consists of a low conductivity, or highly resistive layer of conductive material, such as indium-tin-oxide (“ITO”), for example. Control electrode  130  is surrounded by a highly conductive annular contact electrode  120 , which is made from a conductive metal, such as silver, aluminum, copper, for example.  
         [0003]      FIG. 1   b  illustrates the construction of modal liquid crystal lens  100 . As described by Naumov, control electrode  130  generally has a relatively high resistance with a surface resistance of around a few MΩ/square. Ground electrode  160  is generally a highly conductive ITO layer with a surface resistance of about 50 to 200 Ω/square. The cell  150  containing the liquid crystal material is formed by the spacers  140  placed between the front substrate  110  and rear substrate  170 . The modal liquid crystal lens  100  is operated by applying a voltage to the annular contact electrode  120 . The voltage across the modal liquid crystal lens  100  decreases radially towards the center of the modal liquid crystal lens  100  because of the potential divider that is formed by the high resistance control electrode  130  and the capacitance of the liquid crystal layer  150 . In response to the radially varying potential, the retardance of liquid crystal layer  150  changes. Thus, the optical path length through the liquid crystal layer  150  increases from the edge of the modal liquid crystal lens  100  towards the center thus producing a retarding profile across the modal liquid crystal lens  100 . By controlling the voltage and frequency of the waveform applied to the annular contact electrode  120  the optical power of the modal liquid crystal lens  100  can be continuously adjusted over a range of a few Diopters, depending on the thickness of the liquid crystal layer  150 .  
         [0004]     While such modal liquid crystal lenses offer several advantages in terms of continuous optical power tuning and simplicity of design, they have several limitations that hinder their practical use as spectacle lenses, in particular, a lens for the treatment of presbyopia. For example, such lenses are not completely transparent, and use visible metallic electrodes. In addition, such lenses are not constructed in a manner that allows for them to be cut and shaped so that they may be placed within a frame. Moreover, such lenses do not have a relatively quick response time (for example, less than 30 milliseconds) so that the optical power changes faster than the wearer&#39;s eye can detect, and do not account for a step change in optical power with an adjacent base lens used to provide a distance correction. This leads to discomfort for the wearer, and also detracts from the cosmetic appearance of the lens.  
         [0005]     Accordingly, the present invention provides an electro-active lens and electro-active spectacles useful in the treatment of presbyopia that employ modal liquid crystal lenses, and that overcome the disadvantages of known devices while offering features not present in known devices. Although certain deficiencies in the related art are described in this background discussion and elsewhere, it will be understood that these deficiencies were not necessarily heretofore recognized or known as deficiencies. Furthermore, it will be understood that, to the extent that one or more of the deficiencies described herein may be found in an embodiment of the claimed invention, the presence of such deficiencies does not detract from the novelty or non-obviousness of the invention or remove the embodiment from the scope of the claimed invention.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention, according to one embodiment, relates to an electro-active spectacle lens. The spectacle lens comprises a first substrate having a first outer region and first inner region, a first electrode layer disposed adjacent to the first inner region, the first electrode layer including an outer electrode region having a first conductivity and an inner electrode region having a second conductivity, the first conductivity being greater than the second conductivity, a second substrate having a second outer region and second inner region, a second electrode layer disposed adjacent to the second inner region, the second electrode layer having a third conductivity, and an electro-active cell disposed between the first electrode layer and the second electrode layer, the electro-active cell containing an electro-active material. The first outer region and second outer region are configurable for fitting the spectacle lens within a lens frame without altering the electro-active cell.  
         [0007]     The invention, according to another embodiment, relates to an electro-active spectacle lens. The electro-active spectacle lens comprises a first modal liquid crystal lens assembly having a first substrate having a first outer region and first inner region, a first electrode layer disposed adjacent to the first inner region, the first electrode layer including a first outer electrode region having a first conductivity and a first inner electrode region having a second conductivity, the first conductivity being greater than the second conductivity, a second substrate having a second outer region and second inner region, a second electrode layer disposed adjacent to the second inner region, the second electrode layer having a third conductivity, and a first electro-active cell disposed between the first electrode layer and the second electrode layer, the first electro-active cell containing a first electro-active material. The electro-active spectacle lens further comprises a second modal liquid crystal lens assembly having a third substrate having a third outer region and third inner region, a third electrode layer disposed adjacent to the third inner region, the third electrode layer including a second outer electrode region having a fourth conductivity and a second inner electrode region having a fifth conductivity, the fourth conductivity being greater than the fifth conductivity, a fourth substrate having a fourth outer region and fourth inner region, a fourth electrode layer disposed adjacent to the fourth inner region, the fourth electrode layer having a sixth conductivity, and a second electro-active cell disposed between the third electrode layer and the fourth electrode layer, the second electro-active cell containing a second electro-active material, and a controller for directing application of voltage to the first electrode layer, second electrode layer, third electrode layer and fourth electrode layer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention can be more fully understood by reading the following detailed description of the presently preferred embodiments together with the accompanying drawings, in which like reference indicators are used to designate like elements, and in which:  
         [0009]      FIG. 1   a  is a planar view of an illustrative electrode layer used in a modal liquid crystal lens;  
         [0010]      FIG. 1   b  is a side sectional view of an illustrative modal liquid crystal lens;  
         [0011]      FIGS. 2   a,    2   b,    2   c  and  2   d  illustrate the various components of an illustrative electro-active spectacle lens in accordance with one embodiment of the invention;  
         [0012]      FIGS. 3   a  and  3   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a modal liquid crystal lens assembly in accordance with one embodiment of the invention;  
         [0013]      FIGS. 4   a  and  4   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a modal liquid crystal lens assembly in accordance with one embodiment of the invention;  
         [0014]      FIGS. 5   a,    5   b,    5   c  and  5   d  are perspective views of an illustrate electro-active spectacles lens in further detail demonstrating an illustrative finishing process for placing the electro-active spectacles lens in an eyeglass frame in accordance with an embodiment of the invention;  
         [0015]      FIGS. 6   a  and  6   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a plurality of modal liquid crystal lens assemblies in accordance with one embodiment of the invention;  
         [0016]      FIG. 7  is planar view of an illustrative electro-active spectacle lens that employs an electro-active blending zone through the addition of a blended electrode;  
         [0017]      FIG. 8  is planar view of an illustrative electro-active spectacle lens that employs a series of electro-active blending zones through the addition of blended electrodes; and  
         [0018]      FIGS. 9   a  and  9   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a plurality of modal liquid crystal lens assemblies in accordance with one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]     Various embodiments of electro-active spectacle lenses and spectacles employing modal liquid crystal lens assemblies, and methods of manufacturing such electro-active spectacles lenses are described herein. These lenses may be used to provide vision correction for one or more focal lengths, and may further correct non-conventional refractive error including higher order aberrations.  
         [0020]     To assist with understanding certain embodiments described herein, explanations of various terms are provided. “Attaching” can include bonding, depositing, adhering, and other well-known attachment methods. A “controller” can include or be included in a processor, a microprocessor, an integrated circuit, a computer chip, and/or a chip. A “conductive bus” operates to conduct data in the form of an electrical signal from one place to another place. “Near distance refractive error” can include presbyopia and any other refractive error needed to be corrected for one to see clearly at near distance. “Intermediate distance refractive error” can include the degree of presbyopia needed to be corrected an intermediate distance and any other refractive error needed to be corrected for one to see clearly at intermediate distance. “Far distance refractive error” can include any refractive error needed to be corrected for one to see clearly at far distance. “Conventional refractive error” can include myopia, hyperopia, astigmatism, and/or presbyopia. “Non-conventional refractive error” can include irregular astigmatism, aberrations of the ocular system including coma, chromatic aberrations, and spherical aberrations, as well as any other higher order aberrations or refractive error not included in conventional refractive error. “Optical refractive error” can include any aberrations associated with a lens optic.  
         [0021]     In certain embodiments, a “spectacle” can include one lens. In other embodiments, a “spectacle” can include more than one lens. A “multi-focal” lens can include bifocal, trifocal, quadrafocal, and/or progressive addition lens. A “finished” lens blank can include a lens blank that has finished optical surface on both sides. A “semi-finished” lens blank can include a lens blank that has, on one side only, a finished optical surface, and on the other side, a non-optically finished surface, the lens needing further modifications, such as, for example, grinding and/or polishing, to make it into a useable lens. An “unfinished” lens blank has no finished surface on either side. “Base lens” refers to the non-electro-active portion of a lens blank which has been finished.  
         [0022]     “Surfacing” can include grinding and/or polishing off excess material to finish a non-finished surface of a semi-finished or unfinished lens blank. The lens blank may also be finished using free form machining techniques that have recently been adopted by the ophthalmic lens industry. Free forming techniques allow a completely arbitrary shape to be placed on the lens blank that may be used to complete conventional error correction, but may also be used to correct higher order aberrations to provide for a non-conventional error correction that may lead to vision correction better than 20/20. Further, the lens blank can be fabricated by bonding two or more lens wafers together to form a finished lens or a semi-finished lens blank. It should be appreciated that the lens blank, whether finished, unfinished, or semi-finished, may initially be fabricated using free form techniques to correct for either or both of conventional and non-conventional refractive error.  
         [0023]     Modal liquid crystal lenses are switchable lenses with a continuous phase variation across the lens. Such lenses are operated by applying a voltage to an annular contact electrode. Voltage across the lens decreases radially towards its center because of the potential divider caused by the high resistance control electrode and the capacitance of the liquid crystal layer. This changes the retardance of liquid crystal layer, and increases the optical path length through the liquid crystal layer from the edge of the lens towards the center, thus producing a retarding profile across the lens. However, known modal liquid crystal lenses have several limitations that hinder their practical use as spectacle lenses, i.e., they are not completely transparent, they cannot be cut or shaped, they do not have a relatively quick response time and do not account for a step change in optical power with an adjacent base lens used to provide a distance correction.  
         [0024]      FIGS. 2   a,    2   b,    2   c  and  2   d  illustrate the various components of an illustrative electro-active spectacle lens in accordance with one embodiment of the invention.  FIG. 2   a  is planar view of a front substrate  210  with a first electrode layer including annular contact electrode  220  and control electrode  230 . Front substrate  210  is comprised of glass, optical grade plastic or other suitable material. Control electrode  230  is comprised of a low conductivity, or highly resistive layer, transparent material, and annular contact electrode  220  is formed from a highly conductive, transparent material. In one embodiment, the control electrode  230  and annular contact electrode  220  are formed from ITO, and it should be appreciated that the characteristics of the ITO used for the control electrode  230  and annular contact electrode  220  may be varied to achieve the desired conductivity for in the different electrodes. Bus electrode  222  is also placed on front substrate  210  and coupled to annular contact electrode  220 . In one embodiment, bus electrode  222  is formed from highly conductive, transparent material, such as ITO, for example. As shown in  FIG. 2   a,  bus electrode  222  extends from the edge of front substrate  210  to annular contact electrode  220  so that power can be applied to the annular contact electrode  220  from the edge of front substrate  210 , and eventually, from the edge of the finished lens  200 .  
         [0025]      FIG. 2   b  is planar view of a rear substrate  270  with a second electrode layer including ground electrode  260 . In one embodiment, ground electrode  260  is formed from highly conductive, transparent material, such as ITO, for example. Bus electrode  262  is also placed on rear substrate  270  and coupled to ground electrode  260 . In one embodiment, bus electrode  262  is formed from highly conductive, transparent material, such as ITO, for example. As shown in  FIG. 2   b,  bus electrode  262  extends from the edge of rear substrate  270  to ground electrode  260  so that electrical contact can be made to the ground electrode  260  from the edge of rear substrate  270 , and eventually, from the edge of the finished lens  200 .  
         [0026]      FIG. 2   c  is a planar view of an illustrative spacer ring  240 . In one embodiment, spacer ring  240  is formed from ultra thin plastic, glass sheet or other suitable transparent materials. Spacer ring  240  may be attached to either the front substrate  210  or rear substrate  270 . Spacer ring  240  will generally have a thickness in the range of about 5 to 25 microns. It should be appreciated that, in alternative embodiments, an electro-active spectacles lens may avoid the use of a spacer ring by machining a recess in one or both of the front and rear substrates prior to depositing the electrodes layers. It should further be understood, that if nematic liquid crystals are used, then two cells with mutually orthogonal orientations will be required to deal with birefringence.  
         [0027]      FIG. 2   d  is a side sectional view of an illustrative electro-active spectacle lens assembling the components illustrated in  FIGS. 2   a,    2   b  and  2   c.  As shown in  FIG. 2   d,  electro-active spectacle lens  200  is comprised of front substrate  210 , spacer ring  240 , and rear substrate  270 . As described above, the first electrode layer including annular contact electrode  220  and control electrode  230  is disposed adjacent to front substrate  210 . The second electrode layer including the ground electrode  260  is disposed adjacent to the rear substrate  270 . Spacer ring  240  is disposed between front substrate  210  and rear substrate  270 , and the bore in spacer ring  240  is enclosed. This interior space is filled with electro-active material and forms an electro-active cell  250 .  
         [0028]     It should be appreciated that various electro-active materials may be employed in the electro-active spectacle lenses of the present invention, including those disclosed in commonly assigned U.S. patent application Ser. No. 10/046,244 filed Jan. 16, 2002, Ser. No. 10/387,143 filed Mar. 12, 2003, Ser. No. 10/422,128 filed Apr. 24, 2003, and Ser. No. 10/664,112 filed Aug. 20, 2003, the contents of which all of the foregoing applications are incorporated by reference in their entirety.  
         [0029]     Referring to  FIG. 2   d,  as assembled, annular contact electrode  220 , control electrode  230  and ground electrode  260  are disposed adjacent to the electro-active cell  250 . Alignment layers (not illustrated) are formed over the annular contact electrode  220 , control electrode  230  and ground electrode  260  in the area where the electro-active material will reside within the electro-active cell  250 . It should be appreciated that alignment layers may be formed from Poly Vinyl Alcohol (PVA) or other suitable materials. Other suitable methods and process for utilizing alignment layers formed on electrodes may also be employed, such as those described U.S. patent application Ser. Nos. 10/046,244, Ser. No. 10/387,143, Ser. No. 10/422,128, and Ser. No. 10/664,112, the contents of which are incorporated by reference in their entirety.  
         [0030]      FIGS. 3   a  and  3   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a modal liquid crystal lens assembly in accordance with one embodiment of the invention. As shown in exploded view in  FIG. 3   a,  spectacle lens  300  is comprised of first base lens  310 , modal liquid crystal lens assembly  320 , and second base lens  330 . In this embodiment, modal liquid crystal lens assembly  320  shares the same features and structure of electro-active spectacles lens  200  described above. Modal liquid crystal lens assembly  320  is disposed between first base lens  310  and second base lens  330 , which in this embodiment, are lens wafers that produce the base optical power of the spectacle lens  300 , as shown assembled in  FIG. 3   b.  Modal liquid crystal lens assembly  320  may be bonded between first base lens  310  and second base lens  330  with thermal or optically cured resins or adhesives, or other suitable materials. It should further be appreciated that other suitable methods of attaching the modal liquid crystal lens assembly and base lenses may be employed as desired by the skilled artisan. In one embodiment, the index of refraction of the substrates used in the modal liquid crystal lens assembly, the base lenses, and the adhesives or resins fall within a predetermined range from one another, or differ by no more than a specific tolerance. For example, in some embodiments, these materials may have indices of refraction that differ by no more than about 0.01 to 0.05.  
         [0031]      FIGS. 4   a  and  4   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a modal liquid crystal lens assembly in accordance with one embodiment of the invention. As shown in exploded view in  FIG. 4   a,  spectacle lens  400  is comprised of first base lens  410  and modal liquid crystal lens assembly  420 . In this embodiment, modal liquid crystal lens assembly  420  shares many of the same features and structure of electro-active spectacles lens  200  described above, except that modal liquid crystal lens assembly  420  is formed with curved front and rear substrates, and spacer ring. Modal liquid crystal lens assembly  420  may be bonded or attached to first base lens  410  in any suitable manner, such as that described above with reference to spectacle lens  300 . In an alternate embodiment, the positioning of the base lens and modal liquid crystal lens assembly may be reversed. In addition, although spectacle lens  400  is shown with only first base lens  410 , additional base lenses may be employed in alternate curved spectacle lens embodiments.  
         [0032]      FIGS. 5   a,    5   b,    5   c  and  5   d  are perspective views of an illustrate electro-active spectacles lens in further detail demonstrating an illustrative finishing process for placing the electro-active spectacles lens in an eyeglass frame in accordance with an embodiment of the invention. As shown in  FIG. 5   a,  electro-active spectacle lens  500  is provided. In this embodiment, electro-active spectacle lens  500  shares the same features and structure of electro-active spectacles lens  200  described above, including a bus electrode  522 . As shown in  FIG. 5   b,  electro-active spectacle lens  500  may be rotated to position bus electrode  522  so that electrical contacts can be made in the appropriate eyeglass frame. In some embodiments in which electro-active spectacle lens  500  is a toric lens possessing cylinder power for the correction of astigmatism, then the frame design and the required axis of the cylinder correction for electro-active spectacle lens  500  will need to be taken into account when fabricating the electro-active spectacle lens  500 . As shown in  FIGS. 5   c  and  5   d,  electro-active spectacle lens  500  is edged and shaped so that it may be placed in a particular eyeglass frame  592  and appropriate contact can be made with electrical contacts  590 .  
         [0033]     Further detail on suitable methods and process for edging spectacle lenses, finishing blanks into lenses, machining lenses, and manufacturing the components of said lenses in general is disclosed in commonly assigned U.S. patent application Ser. No. 10/046,244, Ser. No. 10/387,143, Ser. No. 10/422,128, and Ser. No. 10/664,112, the contents of which are incorporated by reference in their entirety.  
         [0034]      FIGS. 6   a  and  6   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a plurality of modal liquid crystal lens assemblies in accordance with one embodiment of the invention. As shown in exploded view in  FIG. 6   a,  spectacle lens  600  is comprised of first base lens  610 , first modal liquid crystal lens assembly  620 , second modal liquid crystal lens assembly  630 , third modal liquid crystal lens assembly  640 , and second base lens  690 . In this embodiment, modal liquid crystal lens assemblies  620 ,  630 ,  640  each share the same features and structure of electro-active spectacles lens  200  described above. Modal liquid crystal lens assemblies  620 ,  630 ,  640  are disposed between first base lens  610  and second base lens  690 , which in this embodiment are lens wafers that produce the base optical power of the spectacle lens  600 , as shown assembled in  FIG. 6   b.  Modal liquid crystal lens assemblies  620 ,  630 ,  640  may be bonded between first base lens  610  and second base lens  690  with thermal or optically cured resins or adhesives, or other suitable materials. It should further be appreciated that other suitable methods of attaching the modal liquid crystal lens assemblies and base lenses may be employed as desired by the skilled artisan.  
         [0035]     In this embodiment employing a plurality of stacked modal liquid crystal lens assemblies, the skilled artisan can achieve a number of objectives. For example, the use of multiple, stacked modal liquid crystal lens assemblies reduces the switching time for the combined electro-active spectacle lens. This may be accomplished by reducing the optical power that each modal liquid crystal lens assembly would need to produce, which in turn reduces the required thickness of the electro-active cell and increases the overall switching speed of the electro-active spectacle lens. For example, three stacked modal liquid crystal lens assemblies (as shown in  FIG. 6   b ) each producing +1.0 Diopters of optical power could replace a modal liquid crystal lens assembly producing +3.0 Diopters of adjustable optical power. The use of stacked modal liquid crystal lens assemblies also allows the user to address birefringence. For example, by cross-orienting the liquid crystal alignment axes of stacked modal liquid crystal lens assemblies, a device can be produced that is polarization insensitive. In alternate embodiments, cholesteric liquid crystals may be employed to address birefringence, as opposed to using additional assemblies.  
         [0036]     Another application of the inventive design in  FIG. 6  would be to provide a single manufacturing design of a bifocal lens for multiple prescriptions. As shown in  FIG. 6   b,  three stacked, modal liquid crystal lens assemblies, each with a adjustable range of from about 0.0 to +1.0 Diopter of optical power, could be used in a “ganged” fashion to continuously provide desired amounts of optical power ranging from about 0.0 to +3.0 Diopters. For example, a patient that requires a +1.0 Diopter presbyope prescription may need only a single modal liquid crystal lens assembly activated to provide a +1.0 Diopter of optical power. Moreover, a +1.5 Diopter presbyope may have two modal liquid crystal lens assemblies activated at +0.75 Diopters each, or one lens at +1.0 Diopter and another at +0.5 Diopter, or other suitable combinations arriving at the desired optical power. Similarly, a +2.5 Diopter presbyope may have two modal liquid crystal lens assemblies activated at +1.0 Diopter and the third at +0.5 Diopter, while a +3.0 Diopter presbyope may have all three modal liquid crystal lens assemblies activated to their maximum power.  
         [0037]     Such an embodiment would allow for a single add power combination of a spectacle design to be manufactured for the vast majority if not all of the presbyopic market, reducing the number of individual stock units that have to be manufactured and stored. Additionally, a presbyope would only need a single pair of spectacles as he/she aged and lost accommodation ability, unless there was a distance correction power change. As one requires more add power, the controller that sets the applied voltage to the electro-active spectacle lenses could be adjusted to provide higher plus power with the same set of spectacles as the wearer aged, for example.  
         [0038]     Further detail on structuring electro-active lenses in a stacked arrangement or fashion is disclosed in commonly assigned U.S. application Ser. No. 10/046,244, Ser. No. 10/387,143, Ser. No. 10/422,128, and Ser. No. 10/664,112, the contents of which are incorporated by reference in their entirety.  
         [0039]     As stated above, a significant change in optical power from one region of the electro-active spectacle lens to another adjacent region can cause wearer discomfort. Image jump and discontinuity between vision correction regions or zones may be lessened through the use of an electro-active blending zone.  FIG. 7  is planar view of an illustrative electro-active spectacle lens  700  that employs an electro-active blending zone through the addition of a blended electrode  722 . Electro-active spectacle lens  700 , as shown in  FIG. 7 , includes front substrate  710  with a first electrode layer including outer annular contact electrode  720 , blended electrode  722 , inner annular contact electrode  724  and control electrode  730 . In some embodiments, outer annular contact electrode  720  and inner annular contact electrode  724  share many of the same features and structure as annular contact electrode  220  described above. Similarly, control electrode  730  share many of the same features and structure as control electrode  230  described above. Blended electrode  722  is formed of graded resistivity, transparent material, such as ITO, for example, that includes a tapered resistance to create a voltage profile that would smooth the optical power from the edges of the blending zone. Alternatively, the blend electrode may be of constant conductivity, but merely driven by the appropriate voltage and frequency to produce a optical power gradient.  
         [0040]     In an alternate embodiment, as shown in  FIG. 8 , a series of alternating concentric ring electrodes, switching between annular contact electrodes  820 ,  822 ,  824 ,  826  and blended electrodes  821 ,  823 ,  825  may be utilized in an electro-active spectacle lens  800  to create an optical power transition that minimizes the abrupt change in power that would be present in the associated electro-active cell. It should be appreciated that in such embodiments, where the number of concentric electrodes is increased, area requirements may demand that the area of the electro-active cell also be extended in diameter so the additional electrodes could act on the electro-active material to produce a power transition. Moreover, since the electro-active spectacle lens is dynamically and continuously adjustable over its allowed range, the transition zone would have to be voltage-tunable as well, to allow for a blended transition that matches the corrective power of the two regions at their boundary.  
         [0041]     In an alternate embodiment, a series of stacked modal liquid crystal lens assemblies having electro-active cells of varying diameter may be employed to achieve a blended transition of optical power.  FIGS. 9   a  and  9   b  are side sectional views (exploded and assembled, respectively) of an illustrative electro-active spectacle lens including a plurality of modal liquid crystal lens assemblies in accordance with one embodiment of the invention. As shown in exploded view in  FIG. 6   a,  spectacle lens  900  is comprised of first base lens  910 , first modal liquid crystal lens assembly  920 , second modal liquid crystal lens assembly  930 , third modal liquid crystal lens assembly  940 , and second base lens  990 . In this embodiment, modal liquid crystal lens assemblies  920 ,  930 ,  940  each share the same features and structure of electro-active spectacles lens  200  described above, except that the diameter of the electro-active cell region varies in each lens assembly. Each lens assembly  920 ,  930 ,  940  may, for example, have up to +1.0 Diopter of optical power such that lens  900  may be capable of providing a total of +3.0 Diopter of power in the region defined by the smallest electro-active cell, i.e., in lens assembly  920 .  
         [0042]     The annular region between the smallest and the middle lens radii would have +2.0 Diopters and the annular region between the middle and largest lens radii would have just +1.0 Diopter of power, providing a graduated power decrease to yield a blending transition of optical power. In addition to providing a cosmetically pleasing blend, a transition zone could also be used to provide intermediate vision focusing in an annular region around the central reading portion of the lens assembly but interior to the distance correction region, thus creating a trifocal effect. It should be appreciated that any suitable number of annular regions or zones and corresponding electrodes may be employed to achieve the desired blending transition or focal change or cosmetic appearance for the electro-active spectacle lens.  
         [0043]     In still other embodiments, the actual optical power profile within in the modal lens may be shaped by applying the appropriate voltage and frequency to the driving electrode such that a slight roll off in optical power will occur near the edge of the modal lens. This can be used alone or in combination with stacking to produce more optical blending of the power zones.  
         [0044]     Further detail on utilizing electro-active blending zones in electro-active lenses is disclosed in commonly assigned U.S. application Ser. No. 10/046,244, Ser. No. 10/387,143, Ser. No. 10/422,128, and Ser. No. 10/664,112, the contents of which are incorporated by reference in their entirety.  
         [0045]     It should further be appreciated that the electro-active spectacle lenses of the present invention may be employed in combination with structural components or vision correction devices disclosed in the foregoing applications, such as the controller or processor for controlling the voltage applied to the various electrodes, memory for storing information for controlling the electro-active lens, power supply or batteries, electrical contacts and switches, rangefinders or view sensor devices, all of which have been incorporated by reference previously herein. Further detail on the control and operation of electro-active spectacle lenses is also found in the foregoing applications.  
         [0046]     While the foregoing description includes details and specificities, it is to be understood that these have been included for purposes of explanation only, and are not to be interpreted as limitations of the present invention. Modifications to the embodiments described above can be made without departing from the spirit and scope of the invention, which is intended to be encompassed by the following claims and their legal equivalents.