HK1123608B - Adaptive electro-active lens with variable focal length - Google Patents

Description

Adaptive electro-active lens with variable focal length

Cross reference to related applications

This application claims priority to U.S. provisional application No. 60/645839, filed on 21/1/2005, which is incorporated herein by reference in its entirety.

Background

Correction of age-related optical changes of the eye becomes increasingly important as the expected lifetime continues to increase. One optical change of the eye that is age-related is presbyopia, in which it is difficult to focus a near object on the retina due to reduced flexibility of the lens. Presbyopia usually begins to affect people at their forties, and thus, is highly desirable for vision correction. Lenses with fixed focusing properties have been widely used as spectacles and contact lenses for correcting presbyopia and other conditions.

These lenses are most useful if they have adjustable focus power (i.e., the focus power is not fixed). The adjustable focus magnification provides external accommodation to the eye to focus the object of interest at different distances in focus. Adjustable focus power can be achieved with a mechanical zoom lens. However, mechanical methods make the glasses bulky and expensive.

Different optical techniques have been utilized in bifocal lenses to allow both near and distance vision. For example, a user may wear lenses that provide different focal powers to each eye, one lens for near objects and another lens for distant objects. Alternatively, by using zone division of lenses, bifocal diffractive lenses, or other division techniques, near and distant objects are imaged onto the retina simultaneously, and the brain distinguishes these images. The field of view using these optical techniques is small, except for bifocal diffractive lenses. Moreover, these optical techniques do not work well when the pupil is small, since the iris blocks the light beam passing through the annular portion of the lens. Another option for correction is to use monocular vision lenses, where each eye is provided with a different focal power, one for near objects and one for far objects. However, binocular depth perception is affected when using monocular vision lenses.

Lenses that are electrically switchable in optical systems (e.g., lenses having a liquid crystal layer sandwiched between two electrically conductive plates, where the orientation of the liquid crystal changes upon application of an electric field) have been described (see, e.g., Kowel, appl. Opt.23(16), 2774-. In electrically switchable lenses, various configurations have been investigated, including Fresnel zone plate electrode structures (Williams, SPIE Current Developments in Optical engineering and Commercial Optics, 1168, 352-. Variable focal length liquid crystal lenses have been described (Sato, jap.j.appl.phys.24(8), L626-L628 (1985)). However, the use of liquid crystal lenses in ophthalmic lens applications is limited due to a number of factors including low diffraction efficiency when the focal length is changed and slow switching times due to the required thickness of the liquid crystal layer. There is a need for an improved lens having an adjustable focal power.

Disclosure of Invention

A novel lens design and corresponding apparatus and method for adjusting the focal length of a lens are provided. This new design is based on individually addressable electrode patterns. Described herein are two applications of this new design. The first application is to allow the focal length to switch between discrete values. In one embodiment, the focal length is switched between an initial focal length and an integer multiple of the initial focal length. The second application allows for a more general use where the focal length is continuously adjusted from the minimum possible to infinity according to design parameters. This new design overcomes the difficulties described above.

More particularly, an adjustable focus, electrically controllable electro-active lens is provided. Various methods for discretely or continuously adjusting an electrically controllable electro-active lens are also provided. An electrically controllable electro-active lens allows the focal length to be adjusted without cumbersome and inefficient mechanical movements. Electro-active adjusted focus power and the entire aperture has the same focus power in each operating condition compared to simultaneous vision (simultaneousvision) lenses, such as bifocal, trifocal or progressive or contact lenses, where the field of view of each line of sight is limited to a narrow channel and the user faces both images, and monocular vision lenses, where binocular depth perception is affected. Devices made with adjustable focus, electrically controllable lenses provide large fields of view and high image quality for adjustable focus without the need to switch between different physical lenses. Other advantages of such lenses include compactness, lighter weight, lower cost, and easier operation at low voltage and low power consumption.

In one embodiment, there is provided an adjustable focus, electrically controllable electro-active lens comprising: a liquid crystal layer positioned between a pair of transparent substrates; a Fresnel zone patterned electrode (a Fresnel zone patterned electrode) having M zones, each zone having L individually addressable subregions between the liquid crystal layer and the inward-facing surface of the first transparent substrate, wherein M and L are positive integers; and a conductive layer between the liquid crystal layer and an inward facing surface of the second transparent substrate. The individually addressable sub-regions of the fresnel zone patterned electrode may be located on the same horizontal plane, where the sub-regions are separated by an insulator to prevent electrical shorting, or the individually addressable sub-regions of the fresnel zone patterned electrode may be located on two or more horizontal planes, each separated by an insulating layer, or other configurations as known in the art may be used.

There is provided a method of adjusting a focal length of a lens by an integer multiple of an initial focal length F, the method comprising: providing a lens, the lens comprising: a lens sealing the liquid crystal layer between the pair of transparent substrates; a Fresnel zone patterned electrode located between the liquid crystal layer and the inward facing surface of the first transparent substrate, the patterned electrode having M zones, each zone having L sub-zones, the patterned electrode having a total of M.L individually addressable electrodes; a conductive layer between the liquid crystal layer and an inward facing surface of the second transparent substrate; and an electrical control device electrically connected to the electrode region and the conductive layer; the same voltage is applied to every k individually addressable electrodes, so that the focal length is adjusted to kF, where k is an integer from 1 to ML. The focal length may be adjusted discontinuously from F to infinity.

There is provided a method of continuously adjusting a focal length of a lens, the method comprising: (a) providing a lens including a liquid crystal layer sealed between a pair of transparent substrates; a fresnel zone patterned electrode having L diffraction orders located between the liquid crystal layer and the inward-facing surface of the first transparent substrate, said patterned electrode being a circular array of individually addressable rings; a conductive layer between the liquid crystal layer and an inward facing surface of the second transparent substrate; and an electrical control device electrically connected to the electrode region and the conductive layer; (b) determining a desired focal length (f'); (c) using the equation:to calculate the area of the mth zone of the Fresnel zone patterned electrode, where f' is the design focal length, λ is the design wavelength, and r_mIs the radius of the mth sub-region; (d) dividing the calculated area of the mth region by an integer of L or greater to determine the number of individually addressable electrodes forming the design sub-region; (e) the same voltage is applied to these number of individually addressable electrodes in the design sub-area. The method for continuously adjusting the focal length further comprises, before step (a): determining one or more design focal lengths; the maximum ring size in the fresnel zone patterned electrode is calculated, which allows all design focal lengths to be formed in the design sub-area.

In one embodiment, the electrode areas are formed by patterned ITO (indium tin oxide) electrodes. The phase retardation in each region is modulated by reorienting the liquid crystal with an applied electric field, as is known in the art.

The adjustable focus, electrically controllable electro-active lens described herein provides a number of advantages over current approaches. One advantage resides in adjustably varying a focus power of a lens. The focal length of the diffractive lens is determined by the electrode area spacing. In the lens described herein, the electrode pattern is fixed and the focal length can be directly varied by varying the electrical drive connections to the electrodes and the applied voltages. In one embodiment, the individually addressable electrode regions allow correction of vision at different distances, including near (e.g., reading), intermediate (e.g., computer screen), and far vision. The focus magnification may be adjusted directly by the rangefinder or manually by the user. In one embodiment, the miniature electronic circuit is combined with a lens so that the assembly is compact. Also, the electrode structure is not visible, which provides an ornamental advantage over the flat liquid crystal solution. The loss of electrical power does not affect distance vision (the focal power provided when no current is provided). In each operating condition, the entire aperture has the same focal power. The fresnel zone structure described herein in one embodiment allows for a relatively large aperture that is required for lens applications. Other advantages of the invention described herein include a compact design, light weight, low cost, and easier operation at low voltage and low power dissipation.

As is well known in the art, the focal length of the lenses described herein, and the corresponding diopter value, may be positive or negative depending on the applied voltage. Such variations are known to those of ordinary skill in the art without undue experimentation and are included herein.

As used herein, "adjustable focus" means that the focal length of the lens is not fixed at a distance as in conventional optical lenses. The focal length of the adjustable focusing lens is adjusted by varying the voltage applied to the electrodes using means well known in the art. In one embodiment, the user adjusts the focal length to see the object at the desired distance. By "individually addressable" is meant that the same or different voltages can be applied independently to different electrodes. "electrically controllable" means that a voltage is applied to control or change a parameter, such as changing the orientation state of the liquid crystal, as is well known in the art. "continuously adjust" means that the focal length can be adjusted to many different values that are not exactly a multiple of the original focal length, and "continuously adjust" does not necessarily mean that each different focal length is available due to the physical limitations of current patterned electrode fabrication techniques.

As used herein, a "layer" is not required to be a completely uniform film. There may be some thickness non-uniformity, cracking, or other defects as long as the layer achieves its intended purpose, as described herein. As used herein, "vertical" means substantially perpendicular to the surface of the substrate. Note that the optical axis is generally substantially perpendicular to the surface of the substrate. As used herein, "no horizontal gap" between electrodes includes the case where there is no spacing between electrodes when viewed in a vertical direction, and also includes the case where there is spacing between electrodes when viewed in a vertical direction but which does not reduce the diffraction efficiency of the optical instrument by more than 25% from the theoretical maximum, and all of the various values and ranges therein.

The device of the present invention may be used in a variety of applications known in the art, including lenses for vision correction or modification of humans or animals. These lenses can be incorporated into eyeglasses, as is well known in the art. The eyewear may include one lens or more than one lens. These devices may also be used in display applications, as would be known to one of ordinary skill in the art without undue experimentation. The lenses of the invention may also be used with conventional lenses and optical systems. The lenses of the invention may be used as part of a conventional lens, for example inserted into a conventional lens, or a combination of a conventional lens and a lens of the invention may be used in a stacked manner.

The present invention is useful in preparing eyeglasses having lenses that adjust the focus intensity according to the distance from the object being observed. In one embodiment, the ranging mechanism, battery and control circuitry are housed in the eyewear or are part of a separate control system. These components and their use are well known in the art. As one example, a ranging mechanism is used to determine the distance between the glasses and the desired object. This information is supplied to a microprocessor which adjusts the voltages applied to the individually addressable electrodes, which provides the desired phase transfer function to the lens to view the object.

As is well known in the art, various methods of applying a voltage to the electrodes may be used. A battery may be used to supply the voltage, or other methods may be used, as is known in the art. Various methods of controlling all aspects of the voltage applied to the electrodes may be used, including processors, microprocessors, integrated circuits, and computer chips, as is known in the art. The applied voltage is determined by the desired phase transfer function, as is well known in the art.

Drawings

Fig. 1 shows a schematic illustration of a diffractive lens: diagram (a) is a conventional refractive lens; graph (b) is a diffractive lens with a continuous quadratic notch (blaze) profile; graph (c) is a binary diffractive lens; graph (d) is a fourth order approximation of a diffractive lens.

Fig. 2 shows the structure of the diffraction lens.

Fig. 3 shows a liquid crystal cell.

FIG. 4 shows the general structure of an electro-active liquid crystal lens with patterned electrodes.

Fig. 5A shows a structure in which all electrodes are located on the same plane (single-layer structure) with a small gap between adjacent sub-regions.

Fig. 5B shows a structure in which odd-numbered electrodes and even-numbered electrodes are interleaved in two horizontal layers without gaps between adjacent sub-regions (double-layer structure).

Fig. 6 shows an example of a digital variable focus using an individually addressable electrode pattern.

Figure 7 shows the continuous adjustment of the focal length with an individually addressable circular array of electrodes with appropriate resolution.

Detailed Description

For a better understanding of the invention, a brief review of the basic concepts of liquid crystal cells, as well as some of the basic concepts of diffractive lenses and the principles of adaptive lenses is made herein.

Diffractive lens

Diffractive lenses are well known in the art. The function of the diffractive lens is based on near field diffraction of the fresnel zone pattern. Each point emanating from the structure acts as an emitter of spherical waves. The light field at a particular observation point is the sum of the contributions of the emitted spherical waves to the entire structure. Constructive interference of spherical waves from each point produces a high intensity at the observation point, which corresponds to a high diffraction efficiency.

Fig. 1 shows a schematic illustration of a diffractive lens: diagram (a) is a conventional refractive lens; graph (b) is a diffractive lens with a continuous quadratic notch profile; graph (c) is a binary diffractive lens; graph (d) is a fourth order approximation of a diffractive lens.

Graph (a) of fig. 1 shows a portion of a conventional refractive lens. By removing the phase retardation of the refractive lens by a multiple of 2 π, a diffractive lens as shown in graph (b) of FIG. 1 is obtained. Phase jump at each zone boundary for a design wavelength λ₀2 pi and the score profiles in each region form a complete constructive interference at the focal point. Graph (c) of fig. 1 and graph (d) of fig. 1 show different approximations of the desired phase profile of fig. 1(b), where multiple steps in each region are used to approximate the desired phase profile.

Fig. 2 shows the structure of the diffraction lens. Showing the focal length (f) along the optical axis. Showing a radius (r) perpendicular to the optical axis_m). Note that light enters halfDiameter (r)_m) The path travelled by the lens to the focal point F corresponds to the focal length (F) plus an integer number of wavelengths (m λ) in order to have constructive interference.

In other words, the focal length (f) of the diffractive lens is determined by the period of these regions. The optical path length difference is a multiple of the wavelength. For the m-th region, note that f + m λ is the hypotenuse of the right triangle in FIG. 2:

for paraxial approximation, f > m λ, the radius (r) of these regions or region boundaries is given by

Wherein r is_mIs the outer diameter of the M (M1, 2.. M) th region, λ is the wavelength, and f is the focal length. For an L-order diffractive lens, each zone consists of L sub-zones of equal size (area). Note that there are L subregions, and each subregion has a different optical thickness, and therefore, L phase levels.

The outer diameter of the nth sub-region of the mth region (n ═ 1, 2, 3.. L, L being the number of phase levels in each region) is given by

This defines a Fresnel zone pattern which is at r²Is periodic. The period is equal to r₁ ². Note that r₁Is the radius of the first region and each region has the same area. The focal length of the diffractive lens is

The above equation means that the focal length can be changed by selecting the region period. For a lens with a focal length p · f, the size (area) of each region is p · r₁ ²。

The diffraction efficiency of the multiorder diffractive lens (or L-phase order diffractive lens) is given by

Table 1 gives the various parameters of a 1-diopter diffractive lens. As shown in table 1, the diffraction efficiency increases with an increase in the number of phase levels, while the width of the last subregion decreases with an increase in the aperture of the lens.

TABLE 1

Liquid crystal cell

Liquid crystal cells are well known in the art. Many cell configurations and operations of liquid crystal cells are also known in the art.

FIG. 3 shows an illustrative embodiment of an electro-active liquid crystal cell in which a liquid crystal layer is sandwiched between two glass plates having conductive inner surfaces. The surfaces of the two plates are coated with an alignment layer, such as polyvinyl alcohol (PVA) or nylon 6, and thisThese surfaces are treated by rubbing to give a uniform molecular orientation. The alignment layer is polished in the direction indicated by the arrow, as is well known in the art. A voltage is applied to the conductive inner surface of the plate. In electro-active cells using liquid crystals as the electro-optic medium, each region has the same thickness, but when a voltage is applied to the medium, the refractive index of the abnormal beam changes due to the reorientation of the liquid crystal molecules. As shown in fig. 3, the polishing direction determines the initial orientation of the liquid crystal molecules. The long axes (optical axes) of the liquid crystal molecules are aligned vertically. When an appropriate voltage is applied, the molecules rotate. Effective refractive index (n)_e') is given by

Wherein n is_oAnd n_eThe refractive indices of the ordinary and extraordinary beams, respectively, theta being between the optical and vertical axes of the moleculeThe angle of (c). The extraordinary beam initially having a maximum refractive index n_θ. With increasing applied voltage, the effective refractive index n_e' becomes smaller, and when a saturation voltage is applied, the optical axes of the molecules are horizontally aligned, while the effective refractive index n_a' to a minimum, and equal to n_o. The refractive index of the (horizontally polarized) ordinary beam is always the same. The electro-optic effect thus modulates the effective refractive index of the extraordinary beam.

In the liquid crystal cell described herein, the conductive material on one substrate does not form a uniform layer, but rather forms an electrode pattern, as further described herein.

FIG. 4 shows the general structure of an electro-active liquid crystal lens with patterned electrodes. From top to bottom, these layers include:

410 a substrate to be processed, wherein the substrate is,

420 patterned electrodes (individually controllable electrodes),

430 the alignment layer is aligned with the alignment layer,

440 liquid crystal and 450 spacer(s),

430 the alignment layer is aligned with the alignment layer,

460 is connected to ground, and

410 a substrate.

In particular, FIG. 4 shows the general structure of an electro-active liquid crystal lens used herein. The liquid crystal layer 430 is sandwiched between the patterned electrode 420 and the ground electrode 460. The patterned electrode 430 may be fabricated by photolithographic processing of a conductive film deposited on a glass substrate, as is known in the art, and the ground electrode 460 comprises a uniform conductive layer formed in any manner known in the art. The patterned electrodes comprise a circular array of rings whose radii are determined by the desired focal length, as described herein. The electro-optic effect of the liquid crystal 440 results in an electrically controllable birefringence. The phase profile across the lens is changed by applying appropriate voltages to the patterned electrodes, as described further herein.

The conductive material may be any suitable material including those specifically described herein as well as others known in the art. Preferably, the conductive material is transparent, such as indium oxide, tin oxide or Indium Tin Oxide (ITO). The substrate may be any material capable of providing the desired optical transmission and capable of functioning in the apparatus and methods described herein, such as quartz, glass, or plastic, as is known in the art. The thickness of the conductive layer is typically between 30nm and 200 nm. The layer must be thick enough to provide adequate conduction, but not thick enough to provide excessive thickness to the overall lens structure. The patterned electrode 420 may be formed using photolithographic techniques, such as those described herein and known to those of ordinary skill in the art.

Fig. 5A shows a structure in which all electrodes are on the same plane (single-layer structure) with a small gap between adjacent sub-regions. Controller or driver 510 is connected by wires 520 to vias or contacts 530, which vias or contacts 530 are in turn connected to individually controllable electrodes 540. Note that the lead 520 may be electrically insulated from the electrode 540 by an insulating layer (not shown), and then selectively contacted to the electrode by a via (a hole or channel in the insulating layer) or a contact 530. This type of contact fabrication is well known in manufacturing lithography and in integrated circuit fabrication.

More specifically, FIG. 5A shows a concentric, individually addressable (individually controllable) ring-shaped electrode layout in one layer. Ignoring the conductive lines 520 and vias through the insulation, this layout is defined as a "single layer" structure because all electrodes are in a single layer.

Alternatively, the wires 520 may be closely packed in a bus (not shown) that moves radially with respect to the concentric ring electrodes.

Note that other patterned electrode shapes may be utilized. For example, a hexagonal array may contain hexagonal pixels, or a grid array may contain square pixels, or a collection of irregular shapes may correct for asymmetric refractive errors. Irregularly or complexly shaped electrodes can be made to correct for characteristic asymmetric or unconventional or high order refractive errors. In addition, the electrodes may have a variable thickness in the direction of the optical axis in order to form a more complex interaction with the liquid crystal.

Alternatively, an array with a high pixel density can be controlled to approximate the concentric rings of fig. 5A, especially if more than two pixels fit within the width of one ring electrode, to form a diffractive lens. Such high pixel density arrays may also approximate more complex shapes.

Returning to fig. 5A, the innermost ring electrode is defined as the electrode numbered 1, counting outward to the 16 th outermost electrode. Note that the innermost electrode may preferably be a full circle instead of a ring, but fig. 5A shows a symmetrical ring and so that the via or contact 530 is more clearly shown with the innermost ring electrode.

To form a 4-order or 4-phase diffractive lens, the four innermost rings are combined into one zone. The first region includes electrodes 1-4, numbered outwardly from the innermost electrode. Each of these electrodes 1-4 is a sub-area of the first area. The second region includes electrodes 5-8. The third region comprises electrodes 9-12. The fourth region includes electrodes 13-16. This combination of 16 electrodes produces a 4-order (or phase) diffractive lens with 4 zones.

As discussed above, each ring electrode 540 is independently addressable by the conductive lines 520. If all electrodes are distributed in one layer, there must be an electrically insulating gap between adjacent electrodes. The gap between the electrodes may cause phase distortion, and simulations of this design show that this phase distortion may greatly affect diffraction efficiency and other performance measures.

To mitigate distortion caused by the insulating gap between electrodes in a single layer design, other electrode configurations may be used. For example, the ring electrode may be separated into two different layers to form a "bilayer" design.

In particular, the odd numbered rings may be located in one electrode layer, while the even numbered rings may be located in a separate second electrode layer. The two different electrode layers may be formed of, for example, SiO₂Is insulated by the insulating layer.

Fig. 5B shows a structure in which odd-numbered electrodes and even-numbered electrodes are interleaved in two horizontal layers without gaps between adjacent sub-regions (double-layer structure).

A controller or driver 510 is communicated to the electrodes by wires 520 and the electrodes are combined into a layer 542 with even rings and a layer 544 with odd rings. The two electrode layers are made of insulating layer SiO₂544 are isolated. Chromium (Cr) alignment marks 560 are also shown for lithographic fabrication alignment. Also shown are region m 580 and region m + 1590, which correspond to the contiguous regions of FIG. 5A.

In fig. 5B, a cross-section of a double layer electrode pattern is shown, wherein the odd numbered and even numbered rings are distributed in two separate layers when viewed in a perpendicular direction (viewed along the optical axis) and there is no gap between two adjacent electrodes. In particular, it is noted that the region m 580 is from r_mExtend to r_m+1And includes a total of 4 electrodes. 2 of the 4 electrodes in region m 580 are even numbered electrodes and are located in layer 542, while the remaining 2 electrodes in region m 580 are located in layer 544.

In this case, each ring electrode 540 may be individually addressed from an additional layer (not shown in fig. 5B) through vias, as in the single layer case. The wires 520 may be located in any convenient location or layer.

The following is an example of forming a double-layer structure. For substrates to which patterned electrodes are to be applied, alignment marks 560 are deposited on the conductive layer. Any suitable material may be used for the alignment marks, theSuch as chromium (Cr). Alignment marks 560 allow for proper alignment of the various lithographic masks with the substrate, and thus alignment of the patterns formed in the processing steps associated with each mask using a "set of masks" that are fabricated so as to have the desired overall lithographic definition of the electrodes when they are patterned. A portion of the area of the patterned electrode is formed in the conductive layer using methods known in the art and described herein. Such as SiO₂550 a layer of insulator is deposited onto the patterned conductor layer. The second layer of conductor is deposited on the SiO₂And forming a second portion of the patterned electrode region in the second layer of conductors.

An alignment layer (not shown) is placed on the second layer of conductors and over the conductors of the second substrate. The alignment layer is prepared by methods known in the art, such as by one-way rubbing. The alignment layer currently used is spin-coated polyvinyl alcohol or nylon 6, 6. Preferably, the alignment layer on one substrate is rubbed in a direction anti-parallel to the alignment layer on the other substrate. This provides proper alignment of the liquid crystals, as is well known in the art. A layer of liquid crystal is placed between the substrates and the substrates are separated by a desired distance, such as between 3 and 20 microns, with glass spacers, or by other means known in the art. The spacer may be any desired material such as mylar, glass or quartz, or other material useful for providing the desired spacing. To obtain efficient diffraction, the liquid crystal layer must be thick enough to provide an activated retardation of one wavelength (d > λ/δ n-2.5 μm, where δ n is the birefringence of the liquid crystal medium), but a thicker liquid crystal layer helps to avoid saturation phenomena. The disadvantages of thicker cells include long switching times (proportional to d)²) And loss of sharpness of the electrically activated features. The transparent substrates may be separated by any distance, which allows a desired number of patterned electrodes and a desired thickness of the liquid crystal layer. In a particular embodiment, the transparent substrates are separated by between 3 microns and 20 microns, and all individual values and ranges therein. The presently preferred interval is5 microns.

In operation, a voltage required to change the refractive index to a desired degree is applied to the electrodes by a controller. A "controller" may include or be included in a processor, microprocessor, integrated circuit, IC, computer chip, and/or chip as described above. Typically, voltages up to about 2Vrms are applied to the electrodes. A phase-synchronized, waveform-controlled driver is connected to each electrode set in a common ground configuration. Multiple driver amplitudes are optimized simultaneously for maximum focus diffraction efficiency. The voltage function required to bring the refractive index to the desired level is determined by the liquid crystal or liquid crystal mixture used, as is well known in the art.

Fig. 6 shows an example of a digital variable focus using an individually addressable electrode pattern. Graph (a) corresponds to a basic focal length F, which is determined by the area of the initial single electrode (i.e., the period of the initial structure). The focal length can be increased to a multiple of F by increasing the period of the lens without affecting the diffraction efficiency. Graph (b) corresponds to focal length 2F. Each region (sub-region) of fig. 6B is twice as large in area as the corresponding region in fig. 6A. In both cases, the diffraction efficiency is the same.

In one particular embodiment, the voltages applied to the four electrodes of a particular 4-phase class lens are 1.1V, 1.31V, 1.49V, and 1.72V, respectively. In another example, the voltages applied to the eight electrodes of a particular 8-phase class lens are 0.71V, 0.97V, 1.05V, 1.13V, 1.21V, 1.30V, 1.37V, and 1.48V, respectively. The voltage applied to the electrodes can be readily determined by one of ordinary skill in the art without undue experimentation and is a function of the liquid crystal used, the arrangement of the cells, and other factors, as is well known in the art. As mentioned above, these voltages may be positive or negative, as is well known in the art, depending on the desired focal length. In one embodiment, the voltage applied to the electrodes is a positive or negative value between 0.5V and 2V, and all individual values and subranges therein.

The insulating material may be any suitable material including those specifically described herein as well as others known in the art. In one embodiment, the conductive material and the insulating material are arranged in an alternating manner, for example in a plurality of circles of increasing radius. The pattern may be any desired pattern such as circular, semi-circular, square, angular, or any other shape that provides a desired effect, as described herein. The terms "circular, semi-circular, square, angular" and other shapes are not intended to indicate the precise shape formed, but rather the shape is a generally formed shape and may include bus lines or other methods of generating current through a substrate as is known in the art.

Any liquid crystal may be used in the present invention. Preferably, the switching time is fast enough so that the user is unaware of the delay in switching from one focal length to another. In the particular embodiment described herein, nematic liquid crystals are used as the electro-optic medium. In this embodiment, the lens is responsive to one of two orthogonal polarization components of the light. Polarization insensitive cholesteric liquid crystals may also be used, in which case polarizers are not necessary. Liquid crystals used in the present invention include those that form a nematic, smectic, or cholesteric phase possessing a remote alignment order that can be controlled by an electric field. Preferably, the liquid crystal has a wide nematic temperature range, is easily aligned, has a low threshold voltage, a large electric excitation response and a fast switching speed, and has proven stability and reliable industrial applicability. In a preferred embodiment, E7 (nematic liquid crystal mixture of cyanobiphenyl and cyanoterphenyls sold by Merck) is used. Examples of other nematic liquid crystals that can be used in the present invention are: pentylcyanobiphenyl (5CB), (n-octyloxy) -4-cyanobiphenyl (80 CB). Other examples of liquid crystals that can be used in the present invention are: the compounds 4-cyano-4-n-alkylbiphenyl, 4-n-pentoxybiphenyl, 4-cyano-4 "-n-alkyl-p-terphenyl, with n ═ 3, 4, 5, 6, 7, 8, 9, and commercial mixtures such as E36, E46, and the ZLI series manufactured by bdh (british Drug house) -Merck.

Electro-active polymers may also be used in the present invention. Electro-active polymers include any transparent optically polymeric material, such as those disclosed by j.e. mark in Physical Properties of polymers Handbook (Handbook of Physical Properties of polymers), American institute of Physics, Woodburry, n.y., 1996, which comprise molecules with pi electrons that have asymmetric polarization conjugation between donor and acceptor groups (referred to as chromophores), such as disclosed by ch.bossharp et al in organic nonlinear Optical Materials, Gordon and fiber Publishers, Amsterdam, 1995. Examples of polymers are as follows: polystyrene, polycarbonate, polymethyl methacrylate, polyvinylcarbazole, polyimide, polysilane. Examples of chromophores are: p-nitroaniline (PNA), red dispersant 1(DR 1), 4-methoxy-3-methyl-4' -nitrostilbene, Diethylaminonitrostilbene (DANS), and diethylthiobarbituric acid. The electro-active polymer may be produced by the steps of: a) following the client/host approach, b) covalently incorporated into the polymer (pendant and backbone) through chromophores, and/or c) by lattice hardening methods such as cross-linking, as is well known in the art.

Polymer Liquid Crystals (PLC) may also be used in the present invention. Polymeric liquid crystals are also sometimes referred to as liquid crystal polymers, low molecular weight liquid crystals, self-reinforced polymers, in situ composites, and/or molecular composites. The PLC is a copolymer comprising both a relatively fixed and flexible sequence, such as the Liquid crystallline polymers written by w.brostow, edited by a.a.collyer: from Structures to Applications (liquid crystalline polymers: From Structures to Applications) (Elsevier, New York-London, 1992, Chapter 1). Examples of PLCs are: polymethacrylates and other similar compounds that include pendant 4-cyanophenyl benzoate groups.

Polymer Dispersed Liquid Crystals (PDLC) may also be used in the present invention. PDLC consists of liquid crystal droplets dispersed in a polymer matrix. These materials can be made in several ways: (i) phase alignment by Nematic Curves (NCAP), phase separation by Thermal Induced (TIPS), Solvent Induced (SIPS), and Polymerization Induced (PIPS), as is well known in the art. Examples of PDLCs are: mixtures of liquid crystals E7(BDH-Merck) and NOA65(Norland products, NJ); a mixture of E44(BDH-Merck) and Polymethylmethacrylate (PMMA); a mixture of E49(BDH-Merck) and PMMA; a mixture of the monomer di (poly) pentaerythritol hydroxy-amyl acrylate, liquid crystal E7, N-vinyl pyrrolidone, N-phenylglycine and rose bengal.

Polymer Stabilized Liquid Crystals (PSLCs) may also be used in the present invention. PSLC is a material consisting of liquid crystals in a polymer network, where the polymer constitutes less than 10% by weight of the liquid crystals. The photopolymerizable monomers are mixed together with the liquid crystal and the UV polymerization initiator. After aligning the liquid crystals, polymerization of the monomers is typically initiated by UV exposure, and the resulting polymer forms a network that stabilizes the liquid crystals. For examples of PSLCs, see, for example, C.M. Hudson et al, "Optical Studies of Anisotropic Networks in Polymer-Stabilized Liquid Crystals" (Journal of the Society for Information Display, vol.5/3, 1-5, (1997)), and "Photorefractive in Polymer-Stabilized Liquid Crystals" (J.of am.chem.Soc., 120, 3231 (1998)).

Self-assembling nonlinear supramolecular structures may also be used in the present invention. Self-assembled nonlinear supramolecular structures include electrically activated asymmetric organic films that can be fabricated using the following method: Langmuir-Blodgett films, alternating polyelectrolyte deposition from aqueous solutions (polyanions/polycations), molecular beam epitaxy, sequential synthesis by covalent coupling reactions (e.g., multilayer deposition based on self-assembly of organotrichlorosilane). These techniques typically result in thin films having a thickness of less than about 1 μm.

While the non-limiting description herein provides more details of certain exemplary embodiments, different lens and electrode configurations may be used for various applications. For example, the lens may be immersed in a liquid crystal solution, or the liquid crystal may be sandwiched between planar electrode plates having a gradient refractive index change. The latter makes liquid crystal alignment easier and makes the cell thinner, which enables faster switching. In addition, different electrode region configurations may be used in the methods and apparatus of the present invention. These various lens and electrode region configurations as are known in the art are intended to be included in the present disclosure.

New design with individually addressable patterned electrodes

To overcome the limitations of previous designs, each electrode sub-region of the patterned electrode must be addressed individually. Two different exemplary applications are presented herein. An application allows switching between a basic focal length and a multiple of the basic focal length. Another application is more general and allows to continuously adjust the focal length from the minimum possible to infinity.

1: discontinuous adjustment of focal length

Consider the general structure of a liquid crystal lens shown in fig. 3, and consider the electrode pattern shown in fig. 5A or 5B. The phase profile on the lens is adjusted by applying appropriate voltages to the patterned electrodes and determines the diffraction efficiency.

Individually addressing the sub-regions of the patterned electrode increases the region period and thus the focal length without loss of diffraction efficiency. The assumption is that the geometry of the electrode pattern is designed for phase modulation with L phase levels. According to equations (2a), (2b) and (3), if passedCombining every two adjacent subregions into one, i.e. applying the same voltage to two adjacent electrodes, the region period r₁ ²Increase to 2r₁ ²Then the focal length becomes 2F and the diffraction efficiency is not changed (fig. 6). Similarly, with a fixed electrode pattern, by increasing the area period to 3r respectively₁ ²、4r₁ ²The focal length can be changed to 3F, 4F. In general, by increasing the region period to kr₁ ²The focal length can be changed to kF (k is a positive integer).

If the individually addressable electrode patterns are designed for an adaptive lens with a basic focusing power of, for example, 3 diopters (focal length F ═ 33.33cm) and 8-order phase steps, then the lens has a diffraction efficiency of 95%. By increasing the period by a factor of two, the focal length will increase to 2F-66.67 cm (focusing power-1.5 diopters), while the efficiency is still 95%. By tripling the period, the focal length will increase to 3F-100 cm, corresponding to a focusing power of 1 diopter, while the efficiency remains the same. By increasing the period by four times, the focal length will increase to 4F-133.32 cm, corresponding to a focusing power of 0.75 diopters, while the efficiency remains the same. Similarly, a larger focal length (smaller focal magnification) can be achieved with the same efficiency. When the lens is switched off, there is no focusing power. Table 2 shows parameters for various focusing magnifications. The radii for each sub-region of the 3 diopter, 1.5 diopter, and 1 diopter lenses are shown in tables 3-5, respectively. These structural parameters can be calculated according to the equations presented herein. The relationship between the sub-region boundaries of the three focal magnifications can be easily derived.

Table 2 gives examples of some of the focus magnifications that can be obtained with individually addressable patterned electrodes. Assume that the basic focusing power is 3 diopters (F ═ 33.3cm) and the aperture of the lens is 10 mm. Table 2 shows that the diffraction efficiency remains the same when the focal length is changed.

TABLE 2

Focusing magnification	Phase level	Diffraction efficiency	K value F ═ kF	Area of each sub-region	Width of last sub-region
						3 diopter (F ═ 33.33cm)	8	95％	1	1.453×10μm	4.6μm
1.5 diopter (F ═ 66.67cm)	8	95％	2	2.906×10μm	9.2μm
						1 diopter (F ═ 100cm)	8	95％	3	4.359×105μm2	13.8μm
0.75 diopter (F133.32 cm)	8	95％	4	5.812×10μm	18.5μm
						0 diopter (closed lens)	Not applicable to	-	Infinity(s)	-	-

An important advantage of individually addressable patterned electrodes is that they do provide the same diffraction efficiency to the same lens with adaptive capability for different focusing powers.

In this application, the adjustable focal length is the basic focal length F and a multiple of the basic focal length. Therefore, the adjusted resolution is also F. For example, if the electrodes are designed for a basic focal length of 10cm, the adjustable focal length would be 10cm, 20cm, 30cm, etc. up to infinity. A smaller base focal length may be used if other intermediate focal lengths are desired. However, when F is small, the characteristic size of the electrode becomes very small for a large aperture lens, and it is difficult to make it low cost using currently available technology.

2: continuous adjustment of focal length

It is desirable to design the adaptive lens so that it can be utilized by all patients and applications. This requires the ability of the lens to continuously vary the focal length within a desired range. For this purpose, a more general design methodology has been developed that allows the focal length to be continuously adjusted. As described above, the patterned electrode is a circular array of rings of a particular size. Each ring is individually addressable. The appropriate resolution of the ring is determined by the focal range to be adjusted. For each desired focal length, the size of each sub-region in all regions can be calculated using equations (2a) and (2 b). A certain number of rings can be selected to form each sub-region and an appropriate voltage can be applied. If the resolution of the rings is good enough, the lens can always have a high efficiency when the focal length is changed, and there is no significant efficiency variation. The resolution required for the patterned electrodes is determined by the desired size of the sub-regions in the last few regions of the lens, as described herein.

Figure 7 shows that the focal length is continuously adjusted using an individually addressable circular array of electrodes with appropriate resolution. The four examples in fig. 7 show the electrode spacing for a subset of electrodes in μm. The geometric parameters of the 3D, 2.5D, 2D and 1D magnifications are depicted in examples A, B, C and D, respectively. r is the radius of the zone boundary.

Here, an example is described in which the focal length is continuously varied from-30 cm to infinity. Assume that the diameter of the lens is 10mm and 8-level phase modulation is used. To illustrate the principle, the geometrical parameters of the adjustable focus powers of 3D, 2.5D, 2D and 1D are depicted in fig. 7, where the radius of each zone boundary and the width of each sub-zone for the last one or two zones are clearly shown. More detailed parameters of these lenses can be found in tables 3-7. It can be seen that for a particular focus power, the variation in width of each sub-region is very small at the edges of the lenses, and is even smaller as the aperture of the lenses increases. For larger focal magnifications, the width and the area of each sub-region are smaller. Each electrode is assumed to be 1 μm wide in this area. In this example, since the width of each sub-region is greater than 1 μm, several electrodes may be combined together to form one sub-region, and the boundaries of each sub-region are brought closer together to the nearest electrode boundary. Combining these electrodes means that the same voltage is applied thereto.

For example, for the 2D case (example C), 7 electrodes may be combined to form all sub-regions of region 45. All other sub-regions may be similarly formed. Rounding errors cause very small changes in diffraction efficiency. On the other hand, in a region near the lens center, if an approximately fine electrode is used, the phase step may be larger than 8, and thus the diffraction efficiency in this region can be increased. In general, when the focusing magnification is adjusted, the diffraction efficiency will be almost the same. When the focal length increases from 1m (focusing power 1D) to infinity, the width of each sub-region increases, and all the sub-regions can be generated by combining the calculated number of electrodes. Thus, in this example, all focal lengths from 30cm to infinity (focus magnification from 0 to 3D) can be adjusted, and the lens can be used for all subjects needing to correct vision at different distances within this range.

As noted above, because the near-center region has a larger geometry, the electrode density in this region may be smaller than the electrode density in the near-edge region (the near-center electrode size may be larger than those in other regions). If the density of the electrodes remains the same in the region close to the center, a higher phase order can be obtained and the diffraction order will be increased.

Another way to achieve this is to use pixilated spatial light modulators at the locations where small rectangular pixels are used. These pixels can be multi-layered to reduce or eliminate gaps when the substrate is viewed perpendicularly, similar to the 2-layer disk electrode shown in fig. 5B.

While the description herein contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Additional embodiments are also within the scope of the invention. The invention is not limited to use with eyeglasses. The invention may also be used in microscopes, mirrors, binoculars, and any other optical device through which a user may view. In addition, as will be apparent to those of ordinary skill in the art, the present invention is also useful in other fields, such as telecommunications, optical switches, and medical devices. Any liquid crystal or mixture of liquid crystals that provides the desired phase transfer function at the desired wavelength is useful in the present invention, as is well known to those of ordinary skill in the art. Determining the appropriate voltages and applying the appropriate voltages to the liquid crystal material to produce the desired phase transfer function is well known in the art.

Unless otherwise indicated, each and every device or combination of components described or illustrated herein can be used to practice the present invention. Additional components such as drivers to apply the voltages used, controllers of the voltages, and any additional optical components are well known to those of ordinary skill in the art and may be combined without undue experimentation. The specific names of the compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compound by different names. When a compound is described herein such that a particular isomer or enantiomer of the compound is not designated, for example, by a formula or by a chemical name, the description is intended to include each isomer or enantiomer of the compound described individually or in any combination. Those of ordinary skill in the art will understand that methods, apparatus components, starting materials, and fabrication methods other than those specifically illustrated may be employed in the practice of the present invention without undue experimentation. All such methods, apparatus components, starting materials, and functional equivalents of the methods of manufacture that are known in the art are intended to be included herein. When a range, such as a thickness range or a voltage range, is given in the specification, all intermediate ranges and subranges included in the given range and all individual values are intended to be included in the disclosure.

As used herein, "comprising" is synonymous with "including," "containing," or "characterized by" and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of" excludes any element, step, or ingredient not specified in the claimed element. As used herein, "consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claims. In particular in the description of the components of the compositions or in the description of the elements of the devices, any reference herein to the term "comprising" is to be understood as including compositions and methods consisting essentially of, and consisting of, the recited components or elements. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is/are not specifically disclosed herein.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed and described. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention.

Generally, the terms and phrases used herein have their art-recognized meanings that may be obtained by reference to standard texts, journal references, and contexts known to those of ordinary skill in the art. Specific definitions are provided to clarify their specific use in the context of the present invention. All patents and publications mentioned in the specification are indicative of the levels of those of ordinary skill in the art to which the invention pertains.

Those skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The apparatus and methods and accompanying methods described herein as presently representative of the preferred embodiments are exemplary and are not intended as limitations on the scope of the invention. Modifications and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the claims.

All references cited herein are incorporated by reference to the extent not inconsistent with the disclosure of this specification. Some of the references provided herein are incorporated herein by reference to provide details regarding additional device components, additional liquid crystal cell configurations, additional patterns of patterned electrodes, additional methods of analysis, and additional uses of the present invention.

Smith et al, "The eye and visual optical instruments," Cambridge university Press, 1997.

Vdovin et al, "On the availability of intraocular adaptive optics (possibility for intraocular adaptive optics"), Opt.express 11: 810-.

Electrical controllable liquid crystal Fresnel lenses (Electrically controllable liquid crystal Fresnel lenses) by williams et al, proc.spiei 1168: 352 nd 357, 1989.

Electrically controlled polarization-independent Fresnel lens arrays by j.s. patel et al, opt.lett.16: 532- "534", 1991.

Dance, "Liquid crystal used in switchable Fresnel lenses", Laser Focus World 28: 34, 1992.

Non-display applications of liquid crystal devices, m.c. k.wiltshire, geoj.research 10: 119-125, 1993.

Ren et al, "Tunable Fresnel lenses using nanoscopic liquid crystals dispersed with polymers in nanometer scale", appl. phys. lett.83: 1515 + 1517, 2003.

Fowler et al, "Liquid crystal lens review," sight hal, physical, opt.10: 186 and 194, 1990.

Anterior bifocal intraocular lens (Diffractive bifocal intraocular lens), proc. spie 1052: 142 and 149 1989.

Sato et al, "Variable-focus liquid crystal Fresnel lens," Jpn.J. Appl.Phys.24: L626-L628, 1985.

Command et al, "Variable focal length microlenses," opt.Commun.177: 157 and 170, 2000.

Kowel et al, "Focusing by electrical modulation of diffraction in a liquid crystal cell (Focusing by refractive electrical modulation in a liquid crystal cell), appl.opt.23: 278 and 289 in 1984.

Opuhi et al, "Adaptive lenses", appl. opt.23: 2774 in 1984 2777.

Naumov et al Liquid-crystal adaptive lenses with modal control, opt.lett.23: 992 + 994, 1998.

Book front control systems based on modal liquid crystal lenses wavefront control system, rev, sci, instrum, 71: 3190 and 3297 in 2000.

Three-terminal adaptive nematic liquid crystal lens apparatus, rita et al, opt.lett.19: 1013 and 1015, 1994.

C owan et al, "a switchable liquid crystal binary gabortens," opt. commu.103: 189 and 193, 1993.

Masuda et al Liquid-crystal microlenses with a beam-steering function, appl. opt.36: 4772-4778, 1997.

Digital diffraction Optics (Digital diffraction Optics) of Kress et al, John Wiley & Sons Ltd, 2000.

Table 3. outer diameter of each sub-area for 3D, 15mm, 8 order diffractive lens.

Table 4. outer diameter of each sub-area for a 1.5D, 15mm, 8 order diffractive lens. The area of each region is twice the area of the corresponding 3D lens (table 3).

TABLE 5 outer diameter of each sub-zone for a 1D, 15mm, 8 order diffractive lens. The area of each region is three times the area of the corresponding 3D lens (table 3). The area of each region is twice the area of the corresponding 2D lens (table 4).

Zone #

1 372.49 526.78 645.17 744.98 832.92 912.41 985.52 1053.57

2 1117.47 1177.92 1235.41 1290.35 1343.04 1393.74 1442.65 1489.97

3 1535.82 1580.35 1623.65 1665.83 1706.97 1747.14 1786.41 1824.83

4 1862.46 1899.34 1935.52 1971.04 2005.93 2040.22 2073.95 2107.13

5 2139.80 2171.98 2203.69 2234.95 2265.78 2296.19 2326.21 2355.84

6 2385.11 2414.02 2442.59 2470.83 2498.75 2526.36 2553.67 2580.70

7 2607.44 2633.91 2660.12 2686.08 2711.78 2737.24 2762.47 2787.47

8 2812.25 2836.81 2861.16 2885.31 2909.25 2933.00 2956.56 2979.93

9 3003.12 3026.14 3048.98 3071.64 3094.15 3116.49 3138.67 3160.70

10 3182.57 3204.29 3225.87 3247.31 3268.60 3289.76 3310.78 3331.67

11 3352.42 3373.05 3393.56 3413.94 3434.20 3454.35 3474.37 3494.28

12 3514.08 3533.77 3553.34 3572.81 3592.18 3611.44 3630.60 3649.66

13 3668.62 3687.48 3706.24 3724.92 3743.49 3761.98 3780.38 3798.68

14 3816.90 3835.04 3853.08 3871.05 3888.93 3906.72 3924.44 3942.08

15 3959.64 3977.12 3994.53 4011.86 4029.11 4046.29 4063.40 4080.44

16 4097.41 4114.30 4131.13 4147.89 4164.58 4181.21 4197.77 4214.26

17 4230.69 4247.06 4263.36 4279.60 4295.78 4311.90 4327.96 4343.96

18 4359.90 4375.79 4391.61 4407.38 4423.09 4438.75 4454.35 4469.90

19 4485.39 4500.83 4516.22 4531.56 4546.84 4562.07 4577.25 4592.39

20 4607.47 4622.50 4637.48 4652.42 4667.31 4682.15 4696.94 4711.69

21 4726.39 4741.04 4755.65 4770.22 4784.74 4799.22 4813.65 4828.04

22 4842.39 4856.70 4870.96 4885.18 4899.36 4913.50 4927.60 4941.66

23 4955.68 4969.66 4983.60 4997.50 5011.36 5025.19 5038.97 5052.72

24 5066.43 5080.11 5093.75 5107.35 5120.91 5134.44 5147.94 5161.40

25 5174.82 5188.21 5201.56 5214.88 5228.17 5241.42 5254.64 5267.83

26 5280.98 5294.10 5307.19 5320.24 5333.27 5346.26 5359.22 5372.15

27 5385.05 5397.92 5410.75 5423.56 5436.34 5449.08 5461.80 5474.49

28 5487.14 5499.77 5512.37 5524.94 5537.49 5550.00 5562.49 5574.94

29 5587.37 5599.78 5612.15 5624.50 5636.82 5649.11 5661.38 5673.62

30 5685.84 5698.03 5710.19 5722.32 5734.44 5746.52 5758.58 5770.62

31 5782.62 5794.61 5806.57 5818.50 5830.42 5842.30 5854.17 5866.00

32 5877.82 5889.61 5901.38 5913.12 5924.84 5936.54 5948.21 5959.87

33 5971.49 5983.10 5994.69 6006.25 6017.79 6029.30 6040.80 6052.27

34 6063.72 6075.15 6086.56 6097.95 6109.32 6120.66 6131.99 6143.29

35 6154.57 6165.83 6177.07 6188.30 6199.50 6210.68 6221.84 6232.98

36 6244.10 6255.20 6266.28 6277.34 6288.38 6299.40 6310.41 6321.39

37 6332.36 6343.30 6354.23 6365.14 6376.03 6386.90 6397.75 6408.59

38 6419.40 6430.20 6440.98 6451.74 6462.49 6473.21 6483.92 6494.61

39 6505.29 6515.94 6526.58 6537.20 6547.80 6558.39 6568.96 6579.51

40 6590.05 6600.57 6611.07 6621.56 6632.02 6642.48 6652.91 6663.33

41 6673.74 6684.12 6694.49 6704.85 6715.19 6725.51 6735.82 6746.11

42 6756.39 6766.65 6776.89 6787.12 6797.33 6807.53 6817.72 6827.88

43 6838.04 6848.17 6858.30 6868.41 6878.50 6888.58 6898.64 6908.69

44 6918.72 6928.74 6938.75 6948.74 6958.72 6968.68 6978.63 6988.56

45 6998.48 7008.39 7018.28 7028.16 7038.02 7047.87 7057.71 7067.53

46 7077.34 7087.14 7096.92 7106.69 7116.44 7126.18 7135.91 7145.63

47 7155.33 7165.02 7174.70 7184.36 7194.01 7203.64 7213.27 7222.88

48 7232.48 7242.06 7251.64 7261.20 7270.75 7280.28 7289.80 7299.32

49 7308.81 7318.30 7327.77 7337.23 7346.68 7356.12 7365.54 7374.96

50 7384.36 7393.75 7403.12 7412.49 7421.84 7431.18 7440.51 7449.83

51 7459.14 7468.43 7477.72 7486.99 7496.25 7505.50 7514.74 7523.96

Table 6 outer diameter of each sub-area for 2D, 15mm, 8 order diffractive lens.

Table 7. The outer diameter of each sub-area for a 2.5D, 15mm, 8 order diffractive lens.

Claims (25)

1. An adjustable focus, electrically controllable electro-active lens comprising:

a liquid crystal layer between a pair of transparent substrates; a fresnel zone patterned electrode having M zones, each zone having L individually addressable sub-zones between the liquid crystal layer and the inward facing surface of the first transparent substrate, where M and L are positive integers; wherein within each of the M regions, the radial width of each of the L individually addressable subregions decreases as the radial position of the individually addressable subregion increases; and

a conductive layer between the liquid crystal layer and an inward facing surface of the second transparent substrate.

2. The lens of claim 1, wherein the individually addressable sub-regions of the fresnel zone patterned electrode are on the same horizontal plane.

3. The lens of claim 1, wherein the liquid crystal is selected from the group consisting of: nematic, cholesteric, electroactive polymers, polymeric liquid crystals, polymer dispersed liquid crystals, polymer stabilized liquid crystals, and self-assembled nonlinear supramolecular structures.

4. The lens of claim 3, wherein the liquid crystal is nematic.

5. The lens of claim 4, wherein the liquid crystal is a mixture of cyanobiphenyl and cyanobiphenyl.

6. The lens of claim 1, wherein the transparent substrate is glass.

7. The lens of claim 1, wherein the transparent substrate is plastic.

8. The lens of claim 1, further comprising an electrical control device electrically connected to the individually addressable sub-regions and the conductive layer.

9. The lens of claim 8, wherein the electrical control device applies a positive or negative voltage to the individually addressable subregions.

10. The lens of claim 9, wherein the voltage is between negative 3 volts and positive 3 volts.

11. The lens of claim 8, further comprising a distance measuring device electrically connected to the electrical control device.

12. The lens of claim 1, wherein the patterned electrode and the conductive layer are transparent.

13. The lens of claim 12, wherein the patterned electrode and conductive layer are indium tin oxide.

14. The lens of claim 1, further comprising an alignment layer around the liquid crystal layer.

15. The lens of claim 14, wherein the alignment layer is polyvinyl alcohol.

16. The lens of claim 14, wherein the alignment layer is polyamide 6, 6.

17. The lens of claim 1, wherein the transparent substrates are separated by between 3 microns and 20 microns.

18. The lens of claim 1, wherein the focal length is positive.

19. The lens of claim 1, wherein the focal length is negative.

20. A method of adjusting a focal length of a lens to an integer multiple of an initial focal length F, the method comprising:

providing a lens, the lens comprising: a liquid crystal layer sealed between a pair of transparent substrates; a Fresnel zone patterned electrode located between the liquid crystal layer and the inward facing surface of the first transparent substrate, the patterned electrode having M zones, each zone having L sub-zones, the patterned electrode having a total of M.L individually addressable electrodes; wherein M and L are positive integers, wherein within each of the M regions the radial width of each of the L individually addressable subregions decreases with increasing radial position of the individually addressable subregions; a conductive layer between the liquid crystal layer and an inward facing surface of the second transparent substrate; and an electrical control device electrically connected to the electrode region and the electrically conductive layer; the same voltage is applied to every k individually addressable electrodes, thereby adjusting the focal length to k · F, where k is an integer from 1 to M · L.

21. The method of claim 20, wherein the applied voltage is between negative 3 volts and positive 3 volts.

22. A method of continuously adjusting the focal length of a lens, the method comprising:

(a) providing a lens, the lens comprising: a liquid crystal layer sealed between a pair of transparent substrates; a fresnel zone patterned electrode having L diffraction orders located between the liquid crystal layer and the inward-facing surface of the first transparent substrate, said patterned electrode being a circular array of individually addressable rings; a conductive layer between the liquid crystal layer and an inward facing surface of the second transparent substrate; and an electrical control device electrically connected to the electrode region and the electrically conductive layer;

(b) determining a design focal length;

(c) using the equation:calculating the area of the mth area of the fresnel-zone patterned electrode, where f' is the design focal length and λ is the design wavelength;

(d) dividing the calculated area of the mth region by an integer of L or more to determine the number of individually addressable electrodes forming the design sub-region; and

(e) the same voltage is applied to these number of individually addressable electrodes in the design sub-area.

23. The method of claim 22, further comprising, prior to step (a):

determining one or more design focal lengths;

the maximum ring size in the fresnel zone patterned electrode is calculated, which allows all design focal lengths to be formed in the design sub-area.

24. The method of claim 22, further comprising determining a design focal length with a ranging device to determine a distance between the lens and a desired object.

25. The method of claim 22, wherein the applied voltage is between negative 3 volts and positive 3 volts.