TWI475278B - Adaptive electro-active lens with variable focal length - Google Patents

Description

Adaptive electroactive lens with variable focal length

The present invention relates to an electrically controllable electroactive lens with adjustable focus.

As life expectancy continues to increase, the correction of age-related optical changes in the eye becomes more and more important. One of the eye-related optical changes in the eye is hyperopia, where it is difficult to focus the near object on the retina due to the reduced elasticity of the lens. Hyperopia usually begins to affect people when they are in their 40s, so there is a great need for this visual correction. Ophthalmic lenses with fixed focus performance have been widely used as glasses and contact lenses to correct for hyperopia and other situations.

It is most useful if the ophthalmic lens has an adjustable focus power (ie, the focus power is not stationary). The adjustable focus power provides external adaptive adjustment of the eye to focus the objects of interest at different distances to focus. Adjustable focus power is achieved using a mechanical zoom lens. However, mechanical methods can make the glasses bulky and expensive.

Different optical techniques have been used in bifocal lenses to allow for near vision and long range vision. For example, a user may wear a lens that provides different focus power for each eye, one for a near object and the other for a far object. Alternatively, near and far objects can be simultaneously imaged onto the retina by using a lens, region segmentation of a bifocal diffractive lens, or other segmentation techniques and the brain distinguishes such images. Except for the dual focus diffractive lens, the viewing area using these optical techniques is small. In addition, when the pupil is small, these optical techniques do not work well because the iris blocks the light beam that passes through the annular portion of the lens. Another option for correction is the use of a single vision lens in which different focus powers are provided to each eye, one for a near object and the other for a far object. However, when a single vision lens is used, binocular depth perception is affected.

An electrically switchable lens has been described (for example, a lens having a liquid crystal layer sandwiched between two conductive plates, wherein the orientation of the liquid crystal changes depending on the application of an electric field) for use in an optical system (see, for example, Kowel Appl. Opt .23(16), 2774-2777 (1984); Dance Focus World 28, 34 (1992). Among the electrically switchable lenses, various electrode configurations have been investigated, including Fresnel strip electrode structures (SPIE Current Developments in Optical Engineering and Commercial Optics, 1168, 352-357 (1989); McOwan Optics Communications 103, 189-193 (1993)). A variable focal length liquid crystal lens has 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 as the focal length changes and low switching times due to the desired thickness of the liquid crystal layer. There is a need for an improved lens with adjustable focus power.

A novel lens design and corresponding apparatus and method for adjusting the focal length of the lens are provided. The novel design is based on individual addressable electrode patterns. Two applications of the novel design are described herein. The first application allows 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 in which the focal length is continuously adjusted from the smallest possible value to infinity based on design parameters. The novel design overcomes the above difficulties.

More specifically, an electrically controllable electroactive lens with adjustable focus is provided. A method for discretely or continuously adjusting the focal length of an electrically controllable electroactive lens is also provided. The electrically controllable electroactive lens allows the focal length to be adjusted without cumbersome and inefficient mechanical movement. A simultaneous vision lens with a narrow channel and a user facing two images, such as bifocal, trifocal or progressive glasses or contact lenses, and a single vision in which binocular depth perception is affected In contrast to the lens, the electrical activity adjusts the focus power and the entire aperture has the same focus power under each operating condition. A device made of an electrically controllable lens with adjustable focus provides adjustable focus with a large viewing area and high image quality while switching between different physical lenses. Other advantages of this lens include compactness, light weight, low cost, and ease of operation with low voltage and low power consumption.

In one embodiment, an electrically controllable electroactive lens having an adjustable focus is provided, comprising: a liquid crystal layer disposed between a pair of transparent substrates; and a Fresnel region patterned electrode having M regions each having L individual addressable sub-regions between the liquid crystal layer and the inwardly facing surface of the first transparent substrate, wherein M and L are positive integers; and a conductive layer Located between the liquid crystal layer and the inwardly facing surface of the second transparent substrate. The individually addressable sub-regions of the Fresnel zone patterned electrode are on the same horizontal plane, wherein the sub-regions are separated by an insulator to prevent electrical shorting, or the Fresnel zone patterned electrodes can be individually The addressed sub-regions are placed on two or more horizontal planes, each separated by an insulating layer, or other configurations known in the art can be used.

A method of adjusting a focal length of a lens to an integral multiple of an initial focal length F, comprising: providing a lens comprising a liquid crystal layer enclosed between a pair of transparent substrates; a Fresnel zone patterning An electrode disposed between the liquid crystal layer and an inwardly facing surface of the first transparent substrate, the patterned electrode having M regions, each region having L sub-regions, the patterned electrode having a total of ML An individually addressable electrode; a conductive layer between the surface of the liquid crystal layer and the inward facing surface of the second transparent substrate; and an electrical control electrically connected to the electrode regions and the conductive layer; A voltage is applied to each of the k individual addressable electrodes to adjust the focal length to kF, where k is an integer from 1 to ML. The focal length can be discretely adjusted from F to infinity.

A method of continuously adjusting a focal length of a lens, comprising: (a) providing a lens comprising a liquid crystal layer enclosed between a pair of transparent substrates; and a Fresnel having L diffraction levels a patterned electrode disposed between the liquid crystal layer and an inwardly facing surface of the first transparent substrate, the patterned electrodes being a circular array of individual addressable rings; a conductive layer located in the liquid crystal a layer between the inwardly facing surface of the second transparent substrate; and an electrical control electrically connected to the electrode regions and the conductive layer; (b) determining the desired focal length (f'); (c) using The following equation calculates the area of the mth region of the Fresnel zone patterned electrode: + f ' ² =( f '+ m λ) ² , where f' is the design focal length and λ is the design wavelength; (d) dividing the calculated area of the mth region by L or a larger integer To determine a number of individual addressable electrodes that form a design sub-region; (e) apply the same voltage to the plurality of individually addressable electrodes in a design sub-region. The method for continuously adjusting the focal length may further include: determining one or more design focal lengths before the step (a); calculating that the design focal lengths are allowed to be formed in the Fresnel zone patterned electrodes in a design sub-region Maximum ring size.

In one embodiment, the electrode region is formed from a patterned ITO (indium tin oxide) electrode. As is known in the art, the phase retardation in each zone is modulated by redirection of the liquid crystal using the applied electric field.

The electrically focustable electro-active lens of the adjustable focus described herein provides many advantages over current methods. One advantage is the ability to adjustably adjust the focus power of the lens. The focal length of the diffractive lens is determined by the spacing of the electrode regions. In the lenses described herein, the electrode pattern is fixed and the focal length can be directly changed by changing the electronic drive connection to the electrodes and the applied voltage. In one embodiment, the individually addressable electrode regions allow for correction of different distance visions, including near (eg, read), intermediate (eg, computer screen), and farther vision. The focus power can be manually adjusted directly by a range finder or by a user. In one embodiment, the microelectronic circuit can be integrated with the lens so the assembly is tight. Again, the electrode structure is invisible, which provides a decorative advantage over the laminated liquid crystal method. The loss of electrical power will not affect far vision (the focus power is provided when no current is supplied). The entire aperture has the same focus power under each operating condition. The Fresnel zone structure described herein in one embodiment allows for a relatively large aperture that is desirable for ophthalmic lens applications. Other advantages of the invention described herein include compact design, light weight, low cost, ease of operation with low voltage and low power consumption.

As is known in the art, the focal length and corresponding diopter values of the lenses described herein can be positive or negative depending on the applied voltage. Such changes are known to the average skilled artisan without undue experimentation and such modifications are included herein.

As used herein, "adjustable focus" means that the focal length of the lens is not fixed at a distance as is conventional optical lenses. The focus of the adjustable focus lens is adjusted by varying the voltage applied to the electrodes by means known in the art. In one embodiment, the focus of the target at the desired distance is provided by the user adjusting the focal length. "Individually addressable" means that the same or different voltages can be applied to the electrodes independently. "Electrically controllable" means applying a voltage to control or change a parameter, such as the orientation state of a liquid crystal known in the art. "Continuously adjusted" means that the adjustable focal length is a number of different values that are not limited to a multiple of the original focal length and do not necessarily mean that each different focal length can be achieved, due to the physical limitations of current patterned electrode fabrication techniques. .

As used herein, a "layer" does not require an absolutely uniform film. As described herein, certain non-uniform thicknesses, cracks, or other deficiencies may occur as long as the layer performs its intended purpose. As used herein, "vertical" means approximately perpendicular to the surface of the substrate. Note that the general optical axis is approximately perpendicular to the surface of the substrate. As used herein, "no horizontal gap" between electrodes includes a case where there is no space between the electrodes when viewed in the vertical direction, and also includes a gap between the electrodes when viewed in the vertical direction, and At the theoretical maximum, this interval does not reduce the optical diffraction efficiency by more than 25% and all of the individual values and ranges.

The device of the present invention can be used in a variety of applications known in the art, including lenses for human or animal vision correction or correction. Lenses can be incorporated into the spectacles as is known in the art. The glasses may include one lens or more than one lens. As is known to those skilled in the art, the device can be used in display applications without undue experimentation. The lenses of the present invention can be used with conventional lenses and optical devices. The lens of the present invention can be used as part of a conventional lens, for example as an insert for a conventional lens, or a combination of a conventional lens and a lens of the present invention can be used in a stacked manner.

The invention is useful in preparing lenses having a focus intensity adjusted based on the observed target. In an embodiment, the ranging mechanism, battery, and control circuitry can be housed in the glasses or part of a separate control system. These components and their uses are known in the art. As an example, a ranging mechanism is used to determine the distance between the glasses and the desired target. This information can be fed to a microprocessor that adjusts the voltage applied to the individual addressable electrodes, which gives the lens the desired phase transfer function to view the target.

As is known in the art, a variety of methods of applying a voltage to an electrode can be used. A battery or other method can be used to provide the voltage as is known in the art. Various methods of controlling all aspects of the voltage applied to the electrodes, including processors, microprocessors, integrated circuits, and computer chips, are known in the art. As is known in the art, the applied voltage is determined by the desired phase transfer function.

For a better understanding of the present invention, a brief review of the basic concepts of liquid crystal lattices, as well as some of the basic concepts of diffractive lenses and the principles of adaptive lenses will be reviewed herein.

Diffractive lens

Diffractive lenses are known in the art. The function of the diffractive lens is based on a near-field diffraction of a Fresnel zone pattern. Each point from the appearance of the structure acts as a transmitter for a spherical wave. The light field at a particular viewing point is the sum of the components of the spherical wave emitted by the entire structure. The constructive interference of spherical waves from different points produces a high intensity at the observation point, corresponding to a high diffraction efficiency.

Figure 1 shows an illustration of a diffractive lens: graph (a) is a conventional refractive lens; graph (b) is a diffractive lens having a continuous secondary flame profile; and graph (c) is a binary diffractive lens; And the graph (d) is a four-level approximate diffractive lens.

Graph (a) of Figure 1 shows a portion of a conventional refractive lens. A diffraction lens as shown in the graph (b) of Fig. 1 is obtained by removing a plurality of 2π phase delays from the refractive lens. For the design wavelength λ ₀ , the phase jump at the boundary of each zone becomes 2π, and the flame profile in each zone forms a fully constructive interference at the focus. The graph (c) of Figure 1 and the graph (d) of Figure 1 show different approximations of the desired phase profiles in Figure 1(b), where multiple steps in each zone are used to approximate the desired phase profile.

Figure 2 shows the construction of a diffractive lens. The focal length (f) is displayed along the optical axis. The radius (r _m ) is displayed perpendicular to the optical axis. Note: In order to have constructive interference, the path through which the light entering the lens at the radius (r _m ) reaches the focal point F is equal to the focal length (f) plus an integer number of wavelengths (mλ).

In other words, the focal length (f) of the diffractive lens is determined by the period of the zone. The difference in optical path length is a multiple of the wavelength. For the mth zone, note that f+mλ is the hypotenuse of the right triangle in Figure 2:

For a paraxial approximation, f>>mλ, the radius of the zone or zone boundary (r) is given by: Where r _m is the outer diameter of the mth zone (m = 1, 2, 3...M), λ is the wavelength and f is the focal length. For L-level diffractive lenses, each zone consists of L sub-zones of the same size (area). Note that there are L sub-regions and each of the sub-regions has a different optical thickness, so there are L phase levels.

The nth (n=1, 2, 3...L, L is the number of phase levels in each zone) of the mth zone is given by the following equation:

This determines the Fresnel zone pattern, which has a period of γ ² . The period is equal to γ ₁ ² . Note: γ ₁ is the radius of the first zone, and each zone has the same area. The focal length of the diffractive lens is:

The above equation indicates that the focal length can be changed by selecting the zone period. For having a focal length of p. For the lens of f, the size (area) of each zone is p. γ ₁ ² . The diffraction efficiency of a multi-level diffractive lens (or L-phase diffractive lens) is given by

Table 1 gives the different parameters of the 1-diopter diffractive lens. As seen in Table 1, the diffraction efficiency increases as the number of phase levels increases and the width of the last sub-region decreases as the aperture of the lens increases.

Liquid crystal lattice

Liquid crystal lattices are known in the art. Many lattice configurations and operations of liquid crystal lattices are also known in the art.

3 shows an illustrative embodiment of an electroactive liquid crystal lattice in which a liquid crystal layer is sandwiched between two glass sheets having electrically conductive inner surfaces. The surfaces of the panels are coated with an alignment layer such as polyvinyl alcohol (PVA) or nylon 6,6 and treated by rubbing to give the same molecular orientation. As is known in the art, the alignment layer is polished in the direction indicated by the arrows. A voltage is applied to the conductive surfaces within the plates. In an electroactive lattice using a liquid crystal such as an electro-optical medium, each zone has the same thickness, but when a voltage is applied to the medium, the refractive index of the extraordinary beam changes due to redirection of the liquid crystal molecules. As shown in FIG. 3, the initial orientation of the liquid crystal molecules is determined by the polishing direction. The long axes (optical axes) of the liquid crystal molecules are vertically aligned. When an appropriate voltage is applied, the molecules rotate. The effective refractive index (n _e ') is given by: Where n _o and n _e are the refractive indices of the ordinary and anomalous beams, respectively, and θ is the angle between the optical axis of the molecule and the vertical axis. The anomalous beam initially has a maximum refractive index n _e . As the applied voltage increases, the effective refractive index n _e ' becomes smaller, and when a saturation voltage is applied, the optical axes of the molecules are aligned horizontally and the effective refractive index n _e ' reaches a minimum value equal to n _o . For ordinary beams (horizontal polarization), the refractive index is always the same. Therefore, the electro-optic effect modulates the effective refractive index of the abnormal beam.

In the liquid crystal lattice described herein, the conductive material on a substrate does not form a homogeneous layer, but an electrode pattern is formed as described further below.

4 illustrates the general structure of an electroactive liquid crystal lens having patterned electrodes, from top to bottom, the layers comprising: 410 substrates, 420 patterned electrodes (individual controllable electrodes), 430 alignment layers, 440 liquid crystals and 450 Spacers (or spacers), 430 alignment layers, 460 ground, and 410 substrates.

In particular, Figure 4 illustrates the general structure of an electroactive liquid crystal lens as used herein. A liquid crystal layer 430 is sandwiched between the patterned electrode 420 and the ground electrode 460. As is known in the art, patterned electrode 430 can be fabricated by photolithographic processing of a conductive film deposited on a glass substrate, and ground electrode 460 contains a uniform conductive layer formed in any manner known in the art. . As described herein, the patterned electrode comprises a circular array of rings whose radius is determined by the desired focal length. The electro-optic effect of liquid crystal 440 results in electrically controllable birefringence. As further described herein, the phase profile across the lens is tailored by applying an appropriate voltage to the patterned electrode.

The electrically conductive material can be any suitable material, including materials specifically described herein, as well as other materials known in the art. Preferably the electrically conductive material is transparent, such as indium oxide, tin oxide or indium tin oxide (ITO). The substrate can be any material that provides the desired optical propagation and can function in the devices and methods described herein, such as quartz, glass or plastic as is known in the art. The thickness of the conductive layer is usually between 30 nm and 200 nm. The layer must be thick enough to provide sufficient conduction, but not thick enough to provide excessive thickness for the entire lens structure. Patterned electrode 420 can be formed using photolithography techniques, such as the techniques described herein and techniques known to those skilled in the art.

Figure 5A illustrates a structure (a layer structure) in which all of the electrodes are in the same plane with a small gap between adjacent sub-regions. Controller or driver 510 is coupled to channel or junction 530 by wire 520, which in turn is coupled to individual controllable electrode 540. Note that the wires 520 can be electrically insulated from the electrodes 540 by an insulating layer (not shown), and then the wires can selectively contact the electrodes via vias (holes or paths in the insulating layer) or contacts 530. The manufacture of this type of contact is well known in the lithography of manufacturing and in the manufacture of integrated circuits.

More specifically, Figure 5A illustrates the layout of concentric, individually addressable (individually controllable) ring electrodes in a layer. The wires 520 and the channels that pass through the insulator are ignored, since all of the electrodes are in a single layer, this layout is defined as a "layer" structure.

Alternatively, the wires 520 can be tightly reinforced together in a busbar about the radial direction of the concentric ring electrodes.

Note: Other patterned electrode shapes can be used. For example, a hexagonal array may contain hexagonal pixels, or a grid array may contain square pixels, or a set of irregular shapes may correct asymmetric refractive errors. Irregular or complex shaped electrodes can be fabricated to correct a particular asymmetrical or non-conventional or high order refractive error. Further, in order to generate a more complicated interaction with the liquid crystal, the electrode may have a variable thickness in the optical axis direction.

Alternatively, an array having a high pixel density can be controlled to approximate the concentric ring of Figure 5A to produce a diffractive lens, in particular if more than two pixels are mounted within the width of a ring electrode. These high pixel density arrays can also approximate more complex shapes.

Returning to Figure 5A, let us define the innermost ring electrode as the first electrode and count it outward to the 16th, the outermost electrode. Note that the innermost electrode may preferably be a full circle rather than a ring, but Figure 5A is symmetrical to illustrate a ring and the innermost ring electrode is used to more clearly illustrate the channel or contact 530.

To create a 4-level or 4-phase diffractive lens, the innermost four rings can be combined into one zone. This first zone contains electrodes 1 to 4 (counted outward from the innermost electrode). Each of the electrodes 1 to 4 is a sub-region of the first region. The second zone consists of an electrode 5 to an electrode 8. The third zone consists of an electrode 9 to an electrode 12. The fourth zone is composed of the electrode 13 to the electrode 16. This tissue of the 16 electrodes produces a 4-level (or phase) diffractive lens with 4 zones.

As discussed above, each ring electrode 540 is independently addressable by wire 520. If all of the electrodes are distributed in one layer, there must be an electrically insulating gap between adjacent electrodes. The gap between the electrodes can cause phase distortion, and the simulation of this design shows that this phase distortion can greatly affect the diffraction efficiency and other energy measurements.

To alleviate the distortion caused by the insulation gap between the electrodes in a layer of design, other electrode configurations can be used. For example, the ring electrode can be split into two separate layers to create a "two layer" design.

Specifically, an odd number of rings can be placed in an electrode layer, and an even number of rings can be placed in a spaced second electrode layer. The two separate electrode layers can be separated by an insulating layer such as SiO ₂ .

Fig. 5B illustrates a structure (two-layer structure) in which odd-numbered electrodes and even-numbered electrodes are staggered in two horizontal layers and there is no gap between adjacent sub-areas.

The controller or driver 510 is in communication with the electrodes via wires 520 and combines the electrodes into a layer having an even ring 542 and a layer having an odd ring 544. The two electrode layers are separated by an insulating layer SiO ₂ 544. A Cr alignment mark 560 is also shown for photolithographic fabrication alignment. Corresponding to the adjacent area from Fig. 5A, the area m 580 and the area m+1 590 are also displayed.

In FIG. 5B, a cross section of the two-layer electrode pattern is shown, in which odd and even rings are distributed in two separate layers and two adjacent electrodes are observed when viewed in the vertical direction (as viewed along the optical axis). There is no gap between them. Specific, Note: Area m 580 extends from r _m r _{m + 1} and to comprise a total of four electrodes. Both of the four electrodes in region m 580 are even numbered and reside in layer 542, and the remaining two electrodes in region m 580 reside in layer 544.

In this case, each ring electrode 540 can be individually addressed from an additional layer (not shown in Figure 5B) of the channel as in one layer. The wire 520 can be positioned in any convenient location or layer.

Next, an example of the formation of a two-layer structure will be described. For the substrate on which the patterned electrode is applied, the alignment mark 560 can be deposited on the conductive layer. Any suitable material, such as Cr, can be used for the alignment marks. Alignment marks 560 allow for proper alignment of the various photolithographic masks with the substrate, and thus allow for "masking" in the processing steps when patterning the electrodes and from the definition of the desired total photolithography for the electrodes. Each mask of the mask set is properly aligned using the associated pattern. A portion of the region of the patterned electrode is formed in the conductive layer using methods known in the art and described herein. An insulator layer 550, such as SiO ₂ , is deposited over the patterned conductive layer. A second layer of conductor is deposited on the SiO ₂ and a second portion of the patterned electrode region is formed in the second layer of conductor.

An alignment layer (not shown) is placed over the second layer conductor and over the conductor of the second substrate. The alignment layer is prepared by methods known in the art such as one-way rubbing. The alignment layer currently used is spin-coated with polyvinyl alcohol or nylon 6,6. Preferably, the alignment layer on one of the substrates rubs anti-parallel to the alignment layer on the other substrate. This allows for proper alignment of the liquid crystal as is known in the art. A liquid crystal layer is placed between the substrates and the substrates are maintained at a desired distance from the glass spacer (such as a distance between 3 and 20 microns), or other methods known in the art. . The spacer may be, for example, Mylar, glass or quartz or any other desired material for providing the desired spacing. In order to achieve effective diffraction, the liquid crystal layer must be thick enough to provide one of the triggered delays (d > λ / δn ~ 2.5 μm, where δ n is the birefringence of the liquid crystal medium), while a thicker liquid crystal layer helps prevent Saturated phenomenon. Disadvantages of thicker crystal lattices include longer switching times (as a function of d ² ) and loss of defined electrical activity characteristics. The transparent substrate can be separated by any distance that allows the desired number of patterned electrodes and the desired thickness of the liquid crystal layer. In a particular embodiment, the transparent substrates are separated by a distance between 3 microns and 20 microns, and all individual values and ranges are located therein. A currently preferred spacing is 5 microns.

In operation, a voltage required to change the refractive index to a desired level is applied to the electrodes by a controller. The "controller" may include a processor, a microprocessor, an integrated circuit, an IC, a computer chip and/or a chip or a processor, a microprocessor, an integrated circuit, an IC. , a computer chip and / or a wafer. Typically, a voltage of up to about 2 Vrm is applied to the electrodes. Connect the phase-synchronized waveform control driver to each of the electrode groups in the common ground configuration. The driver amplitude is optimized synchronously to achieve maximum focus diffraction efficiency. As is known in the art, the voltage function required to change the refractive index to a desired level is determined by the liquid crystal or liquid crystal mixture used.

Figure 6 shows an example of a digital zoom using individual addressable electrode patterns. The graph (a) corresponds to the basic focal length F, which is determined by the area of the initial single electrode (i.e., the period of the initial structure). The period of the structure is the area of the initial single electrode. The focal length can be increased to a multiple of F by increasing the period of the lens without affecting the diffraction efficiency. The graph (b) corresponds to a focal length of 2F. The area of each zone (sub-zone) of Figure 6B is twice the area of each zone (sub-zone) of Figure 6A. The diffraction efficiency is the same for both cases.

In a specific example, the voltages applied to the four electrodes of a particular 4-phase grade lens are 1.1 V, 1.31 V, 1.49 V, and 1.72 V, respectively. In another example, the voltages applied to the eight electrodes of a particular 8-phase grade lens are 0.71 V, 0.97 V, 1.05 V, 1.13 V, 1.21 V, 1.30 V, 1.37 V, and 1.48 V, respectively. As is known in the art, those skilled in the art can readily determine the voltage applied to the electrodes without undue experimentation and which is a function of the liquid crystal, lattice configuration, and other factors used. As noted above, the voltages can be positive or negative, as is 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 0.5 V and 2 V, and all individual values and sub-ranges are located therein.

The insulating material can be any suitable material, including materials specifically described herein and other materials known in the art. In one embodiment, the electrically conductive material and the insulative material are arranged in an alternating pattern, such as a circle having an increasing radius. As described herein, the patterns can be any desired pattern such as circular, semi-circular, square, angular, or any other shape that provides the desired effect. The term "circular, semi-circular, square, angular" or other shape does not mean to form a perfect shape, as the case is, the shape is generally formed and may include (as is known in the art) Busbars or other methods of transferring current through a substrate.

Any liquid crystal can be used in the present invention. Preferably, the switching time is fast enough so that the user does not notice the delay in switching from one focal length to another. In a particular embodiment described herein, nematic liquid crystals are used as electro-optic media. In this embodiment, the lens has an optical response of one of a pair of two vertically polarized components of light. It is also possible to use a polarization-insensitive cholesteric liquid crystal, in which case a polarizer is unnecessary. The liquid crystal used in the present invention includes liquid crystals forming a nematic, dish or cholesteric phase having a long-range orientation order controllable by an electric field. Preferably, the liquid crystal has a wider nematic temperature range, easier alignment capability, lower threshold voltage, greater electrical activity response and faster switching speed, and proven stability and reliable business. Availability. In a preferred embodiment, E7 (a nematic liquid crystal mixture of cyanobiphenyl and cyano terphenyl sold by Merck) is used. Examples of other nematic liquid crystals which can be used in the present invention are: pentyl-cyano-biphenyl (5CB), (n-octylhydroxyoxy)-4-cyanobiphenyl (80CB). Examples of other nematic liquid crystals which can be used in the present invention are compounds of n = 3, 4, 5, 6, 7, 8, 9 4-cyano-4-n-hydrocarbylbiphenyl, 4-n-pentyloxy Biphenyl, 4-cyano-4"-n-hydrocarbyl-p-terphenyl and commercial mixtures such as E36, E46 and ZLI-series manufactured by BDH (British Drug House)-Merck.

Electroactive polymers can also be used in the present invention. Electroactive polymers include any of the transparent optical polymeric materials disclosed in "Physical Properties of Polymers Handbook" by JEMark, American Institute of Physics, NY Woodburry, 1996, which contain conjugated π-electrons with asymmetric polarization. Molecules, such as those between the donor and acceptor groups (referred to as chromophores) as disclosed in "Organic Nonlinear Optical Materials" by Ch. Bosshard et al., published by Gordon and Breach, Amsterdam, 1995. . Examples of polymers are as follows: polystyrene, polycarbonate, polymethyl methacrylate, polyvinyl carbazole, polyimide, polydecane. Examples of chromophores are: p-nitroaniline (PNA), disperse red 1 (DR1), 3-methyl-4-methoxy-4'-nitrostilbene, diethylamino nitroguanidine (DANS), diethyl-thio-barbituric acid. As is known in the art, electroactive polymers can be produced by: a) following a host/guest method, b) covalently combining chromophores into polymers (side and backbone) and/or c) By a lattice quenching method such as cross-linking.

Polymer liquid crystal (PLC) can also be used in the present invention. Polymeric liquid crystals may also be 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 relatively rigid and entangled sequence as disclosed in "Liquid Crystal line Polymers: From Structures to Applications" by W. Brostow (1992, New-York-London, Elsevier, AA Collyer, eds.). Copolymer. An example of a PLC is a polymethacrylate containing a pendant group of 4-cyanophenyl benzoate and other similar compounds.

Polymer dispersed liquid crystal (PDLC) can also be used in the present invention. The PDLC consists of a dispersion of liquid crystal droplets in a polymer matrix. As is known in the art, these materials are made by (i) phase alignment by nematic (NCAP); by thermally induced phase separation (TIPS); solvent evaporation induced Phase separation method (SIPS); and polymerization induced phase separation (PIPS). Examples of PDLC are: a mixture of liquid crystal E7 (BDH-Merch) and NOA65 (Norland products, Inc. NJ); a mixture of E44 (BDH-Merch) and polymethyl methacrylate (PMMA); E49 (BDH-Merch) Mixture with PMMA; a mixture of monomeric diisopentyl alcohol hydroxypentaacrylate, liquid crystal E7, N-vinylpyrrolidone, N-phenylglycine, and Rose Bengal.

Polymer stabilized liquid crystal (PSLC) can also be used in the present invention. PSLC is a material consisting of liquid crystals in a polymer network in which the polymer composition is less than 10% by weight. The photopolymerizable monomer is mixed with a liquid crystal and a UV (ultraviolet) polymerization initiator. After alignment of the liquid crystals, polymerization of the monomers is typically initiated by UV exposure and the resulting polymer produces a network that stabilizes the liquid crystals. For examples of PSLC, see, for example, CM Hudson et al., Journal of the Society for Information Display, vol. 5/3, 1-5, (1997), Optical Studies of Anisotropic Networks in Polymer-Stabilized Liquid Crystals; GP Wiederrecht et al., J. Am. Chem. Soc., 120, 3231-3236 (1998) "Photorefractivity in Polymer-Stabilized Nematic Liquid Crystals" .

Self-organizing nonlinear supramolecular structures can also be used in the present invention. The self-organizing nonlinear supramolecular structure comprises an electroactive asymmetric organic film which is prepared by using the following method: Langmuir-Blodgett film; alternating polyelectrolyte deposition with aqueous solution (polyanion/polycation); molecular beam epitaxy; Continuous synthesis by covalent coupling reactions (eg, self-assembled multilayer deposition based on organotrichlorosilane). Such techniques typically result in a film having a thickness of less than about 1 μm.

Although the non-limiting description herein provides further details of a particular illustrative embodiment, different lens and electrode configurations are effective for a variety of applications. For example, a lens can be immersed in a liquid crystal solution, or a liquid crystal can be sandwiched between flat electrode plates having a gradient of refractive index change. The latter makes liquid crystal alignment easier and makes the crystal lattice thinner, which allows for faster switching. In addition, different electrode zone configurations can be used in the methods and apparatus of the present invention. It is intended that such different lens and electrode zone configurations and other configurations known in the art are included in the present disclosure.

Novel design using individually addressable patterned electrodes

To overcome the limitations of previous designs, each electrode sub-region of the patterned electrode must be individually addressed. Two different illustrative applications are presented here. One allows switching between a basic focal length and a multiple of the basic focal length. The other is a more general continuous adjustment that allows the focal length to be from the smallest possible value to infinity.

1: discrete adjustment of focal length

Consider the general structure of the liquid crystal lens shown in Fig. 3 and the electrode pattern shown in Fig. 5A or 5B. The phase profile across the lens is adjusted and the phase profile determines the diffraction efficiency by applying an appropriate voltage to the patterned electrode.

Individually addressing the sub-regions of the patterned electrodes allows for increased zone periods and thus increased focal length without sacrificing diffraction efficiency. The geometry of the electrode pattern is assumed to be the focal length F with phase modulation of the L phase. Based on equations (2a), (2b), and (3), if the two adjacent sub-regions are combined into one (ie, the same voltage is applied to two adjacent electrodes), the region period r ₁ ² Increasing to 2 r ₁ ² , the focal length becomes 2F without changing the diffraction efficiency (Fig. 6). Similarly, by using a fixed electrode pattern, by increasing the period of the region to 3 r ₁ ² , 4 r ₁ ² , ..., the focal length can be changed to 3F, 4F, ..., respectively. In general, by increasing the zone period to The focal length can be changed to kF (k is a positive integer).

If the individual addressable electrode pattern is designed for an adaptive lens having a basic focus power of, for example, 3 diopters (focal length F = 33.33 cm) and 8 levels of phase steps, the lens has a diffraction efficiency of 95%. By increasing the period by a factor of two, the focal length can be increased to 2F = 66.67 cm (focus power = 1.5 diopters) and the diffraction efficiency is still 95%. By increasing the period by a factor of three, the focal length can be increased to 3F = 100 cm, corresponding to the power of focus of 1 diopter, while the efficiency remains the same. By increasing the period by a factor of four, the focal length can be increased to 4F = 133.32 cm, which corresponds to a focus power of 0.75 diopters, while the efficiency remains the same. Probably, a larger focal length (smaller focus power) can be achieved using the same efficiency. When the lens is turned off, no focus power is present. Table 2 shows the parameters of various focus powers. Tables 3 through 5 show the radii for each of the 3 diopter, 1.5 diopter, and 1 diopter lenses, respectively. These structural parameters are calculated from the equations presented herein. The relationship between the sub-area boundaries for the three focus powers can be easily seen.

Table 2 gives examples of certain focus powers that can be achieved using individual addressable patterned electrodes. It is assumed that the basic focusing power is 3 diopters (F = 33.3 cm) and the aperture of the lens is 10 mm. Table 2 shows that the diffraction efficiency remains the same when the focal length changes.

A significant advantage of the individually addressable patterned electrodes is that they truly provide the same lens with adaptability for different focusing powers of the same diffraction efficiency.

In this application, the focal length can be adjusted to be a multiple of the basic focal length F and the basic focal length. Therefore, the resolution of the adjustment is also F. For example, if the electrode is designed for a basic focal length of 10 cm, the adjustable focal length will be 10 cm, 20 cm, 30 cm, etc., up to infinity. For other intermediate focal lengths, a smaller basic focal length can be used. However, for larger aperture lenses, the feature size of the electrodes becomes very small and it is difficult to make the electrodes low cost in the current available technology.

2: Continuous adjustment of focal length

It is desirable to design an adaptive lens for use in all patients and applications. This requires the lens to have the ability to continuously change the focal length within the desired range. To achieve this, a more general design method has been developed to allow continuous adjustment of the focal length. As noted above, the patterned electrode is a circular array of rings of a particular size. Each ring is individually addressable. The appropriate resolution of the loop is determined by the range of focal lengths to be adjusted. For each desired focal length, the dimensions of each sub-region of all zones can be calculated using equations (2a) and (2b). 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 ring is good enough, the lens can always have a significant change in efficiency and inefficiency as the focal length changes. As described herein, for a desired lens, the resolution necessary to pattern the electrodes is determined by the size of the sub-regions in the last few regions.

Figure 7 shows the continuous adjustment of the focal length using an individually addressable circular array of electrodes of appropriate resolution. The four examples in Figure 7 show the electrode spacing (expressed in μm) for a subset of electrodes. Geometric parameters for the focused power of 3D, 2.5D, 2D, and 1D are depicted in Examples A, B, C, and D, respectively. r is the radius of the zone boundary.

Here is an example of continuously changing the focal length from ~30 cm to infinity. The diameter of the lens is assumed to be 10 mm and an 8-level phase modulation is used. To illustrate this principle, geometric parameters for adjustable focus power for 3D, 2.5D, 2D, and 1D are depicted in Figure 7, where the radius of each zone boundary and each of the last or two zones are clearly shown. The width of the area. More detailed parameters for these lenses can be seen in Tables 3 through 7. It can be seen that for a particular focus power, the variation in the width of each sub-region at the edges of such lenses is small and the change is even smaller as the aperture of the lens increases. For higher focus power, each sub-area has a smaller width and area. It is assumed that each electrode in this area is 1 μm wide. In this example, since the width of each sub-region is greater than 1 μm, several electrodes can be combined to form a sub-region and the boundaries of each sub-region can be rounded to the nearest electrode boundary. Combining the electrodes means applying the same voltage thereto.

For example, for a 2D case (Example C), seven electrodes can be combined to form all of the sub-regions of region 45. All other sub-regions can be similarly generated. Rounding errors cause small changes in diffraction efficiency. On the other hand, in a region adjacent to the center of the lens, if a similar precision electrode is used, the phase step can be higher than 8 and thus the diffraction efficiency can be increased in this region. In general, when adjusting the focus power, the diffraction efficiency will be almost the same. As the focal length increases from 1 m (focus power 1D) to infinity, the width of each sub-region increases, and all sub-regions can be generated by combining a countable number of electrodes. Thus in this example, all focal lengths can be adjusted from ~30 cm to infinity (focus power from 0 to 3D) and the lens can be used for all patients whose corrections need to be corrected over a range of distance visions.

As noted above, since the region adjacent the center has a larger geometry, the density of the electrodes in this region is smaller than the density of the electrodes in the region adjacent to the edge (the size of the electrode adjacent the center is larger than in the other The size of the electrode in the area). If the same density of electrodes is maintained in the vicinity of the center, a higher phase level can be obtained and the diffraction efficiency can be increased.

Another way to achieve this is to use a pixelated spatial light modulator in which small rectangular pixels are used. Similar to the two-layer circular electrode illustrated in Figure 5B, such pixels may be in multiple layers to reduce or eliminate gaps when viewed perpendicular to the substrate.

While the description herein contains many specifics, the invention is not to be construed as limiting the scope of the invention. Other embodiments are within the scope of the invention. The invention has not been limited to use in glasses. The invention can also be used in microscopes, mirrors, binoculars, and other optical devices that are viewable by its users. Moreover, it will be apparent to those skilled in the art that the present invention is useful in other fields such as telecommunications, optical switches, and medical devices. As is known to those skilled in the art, in the present invention, it is useful to provide a mixture of liquid crystals or liquid crystals of any desired phase transfer function at a desired wavelength. It is known in the art to determine the appropriate voltage and apply an appropriate voltage to the liquid crystal material to produce a desired phase transfer function.

The invention may be practiced using a combination of each of the devices or components described or exemplified, unless otherwise stated. A general driver such as a driver for applying the voltage used, a controller for voltage and other components of any additional optical components are known and incorporated without undue experimentation. The specific names of the compounds are intended to be exemplary since it is known to those skilled in the art that the same compounds may be named differently. When a compound is described herein such that a particular isomer or enantiomer of a compound is not specified (eg, by molecular formula or by chemical name), this description is intended to include each of the compounds described in individual or any combination. Isomers and enantiomers. One of ordinary skill in the art will appreciate that methods, device components, starting materials, and methods of manufacture other than the specific embodiments may be employed without departing from the practice. All of the functional equivalents known in the art to which such methods, device components, starting materials and methods of manufacture are intended are included in the present invention. All of the intermediate ranges and sub-ranges, as well as all individual values included in the ranges, are intended to be included in the present disclosure as long as a range (e.g., thickness range or voltage range) is given in the specification.

"Inclusion" as used herein, is synonymous with "including," or "characterized," and is inclusive or open-ended and does not exclude other unillustrated elements or method steps. As used herein, "consisting of" does not include any element, step, or component that is not described in the claims. As used herein, "consisting essentially of" does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claimed invention. Any reference herein to the term "comprising", particularly in the description of the components of the composition or the description of the elements of a device, is understood to include compositions and methods consisting essentially of or consisting of the recited components or components. . The invention as suitably described herein may be practiced without any element or elements, limitations or limitations that are not specifically disclosed herein.

The use of terms and expressions are used to describe terms, and are not intended to be limiting, and the use of such terms and expressions does not have the purpose of excluding any equivalents of the features shown or described. It should be understood that various modifications are possible within the scope of the invention as claimed and described. Therefore, it is to be understood that the invention may be <Desc/Clms Page number>> </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; Within the scope of the invention.

In general, the terms and phrases used herein have the recognized meaning of the art and can be found by reference to standard texts, journal references, and contexts known to those skilled 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 technical skill of those skilled in the art.

Those skilled in the art will readily appreciate that the present invention is preferably adapted to carry out the objects and the results and advantages and the nature of the invention. The presently described apparatus and methods and associated methods of the present invention are described as illustrative and not intended to limit the scope of the invention. Such changes and other uses are contemplated by those skilled in the art, and such modifications and other uses are encompassed within the spirit of the invention as defined by the scope of the claims.

All references cited herein are hereby incorporated by reference in their entirety to the extent that the disclosure of the present disclosure. Certain references provided herein are incorporated herein by reference to provide details of additional device components, additional liquid crystal lattice configurations, additional patterns for patterning electrodes, additional analytical methods, and additional uses in accordance with the present invention. .

The eye and visual optical instruments of G. Smith et al., published by Cambridge University Press, 1997.

On the possibility of intraocular adaptive optics of G. vdovin et al., Opt. Express 11: 810-817, 2003.

1989, Proc. SPIE 1168: 352-357, G. Williams et al., Electrically controlledlable liquid crystal Fresnel lens.

Electrostatically controlled polarization-independent liquid-crystal Fresnel lens arrays of J.S. Patel et al., Opt. Lett. 16: 532-534, 1991.

Liquid Crystal used in switchable Fresnel len of 1992. Laser Focus World 28:34 B.Dance.

Non-display applications of liquid crystal devices of M.C.K. Wiltshire, 1993, Geo J. Research 10: 119-125.

Tunable Fresnel lens using nanoscale polymer-dispersed liquid crystals by H. Ren et al., Appl. Phys. Lett. 83: 1515-1517.

1990, Ophthal. Physiol. Opt. 10: 186-194, Liquid crystal lens review by C. W. Fowler et al.

Diffractive bifocal intraocular lens of J.A. Futhey, Proc. SPIE 1052: 142-149, 1989.

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

2000. Opt. Commun. 177: 157-170, Variable focal length microlenses of L. G. Commander et al.

Fos by electrical modulation of refraction in a liquid crystal cell of S. T. Kowel et al., Appl. Opt. 23: 278-289.

1984, Appl. Opt. 23: 2774-2777, Nouhi et al., Adaptive spherical lens.

Liquid-crystal adaptive lenses with modal control by F. Naumov et al., Opt. Lett. 23: 992-994, 1998.

Wave front control systems based on modal liquid crystal lenses of M. Y. Loktev et al., Rev. Sci. Instrum. 71: 3190-3297.

The Three-terminal adaptive nematic liquid-crystal lens device of N. A. Riza et al., 1994, Opt. Lett. 19: 1013-1015.

1993. Opt. Commun. 103: 189-193, P. W. McOwan et al., A switchable liquid crystal binary Gabor lens.

Liquid-crystal microlens with a beam-steering function of S. Masuda et al., Appl. Opt. 36: 4772-4778.

Digital Diffractive Optics of Kress et al., John Wiley & Sons Ltd., 2000.

410. . . Substrate

420. . . Patterned electrode

430. . . Alignment layer / liquid crystal layer / patterned electrode

440. . . liquid crystal

450. . . Spacer

460. . . Ground electrode

510. . . Controller or driver

520. . . wire

530. . . Channel or contact

540. . . electrode

542. . . Even ring/layer

544. . . Odd ring/layer

550. . . Insulating layer SiO ₂

560. . . Cr alignment mark

580. . . Area m

590. . . Area m+1

Figure 1 shows an illustration of a diffractive lens: graph (a) is a conventional refractive lens; graph (b) is a diffractive lens having a continuous secondary flame profile; and graph (c) is a binary diffractive lens; And the graph (d) is a four-level approximate diffractive lens.

Figure 2 shows the construction of a diffractive lens.

Figure 3 shows a liquid crystal lattice.

Figure 4 shows the general structure of an electroactive liquid crystal lens having patterned electrodes.

Figure 5A illustrates a structure (a layer structure) in which all of the electrodes are in the same plane with a small gap between adjacent sub-regions.

Fig. 5B illustrates a structure (two-layer structure) in which odd and even electrodes are staggered in two horizontal layers and there is no gap between adjacent sub-regions.

Figure 6 shows an example of a digital zoom using individual addressable electrode patterns.

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

410. . . Substrate

420. . . Patterned electrode

430. . . Alignment layer

440. . . liquid crystal

450. . . Spacer

460. . . Ground electrode

Claims (28)

An electrically controllable electroactive lens with adjustable focus, comprising: a liquid crystal layer disposed between a pair of transparent substrates; a Fresnel region patterned electrode having M regions, each region Having L individual addressable sub-regions between the liquid crystal layer and the inwardly facing surface of the first transparent substrate, wherein both M and L are positive integers greater than or equal to 2, wherein each of the M regions In a region, when the radial position of the individual addressable sub-regions is increased, then each of the L individual addressable sub-regions has a reduced radial width; and a conductive layer is located at the liquid crystal layer and the first Between the surfaces of the two transparent substrates facing inward. The lens of claim 1, wherein the individual addressable sub-regions of the Fresnel zone patterned electrode are on the same horizontal plane. The lens of claim 1, wherein the liquid crystal is selected from the group consisting of nematic, cholesteric, electroactive polymers, polymer liquid crystals, polymer dispersed liquid crystals, and polymer stabilized groups. Polymer-stabilized liquid crystal and self-organizing nonlinear supramolecular structure. The lens of claim 3, wherein the liquid crystal is a nematic type. The lens of claim 4, wherein the liquid crystal is E7. The lens of claim 1, wherein the transparent substrate is glass. The lens of claim 1, wherein the transparent substrates are plastic. The lens of claim 1 further comprising an electrical control electrically coupled to the individually addressable sub-regions and the conductive layer. The lens of claim 8, wherein the electrical control applies a positive or negative voltage to the individually addressable sub-regions. The lens of claim 9, wherein the voltage is between minus 3 volts and plus 3 volts. The lens of claim 8 further comprising a distance measuring device electrically coupled to the electrical control. The lens of claim 1, wherein the patterned electrode and the conductive layer are transparent. The lens of claim 12, wherein the patterned electrode and the conductive layer are indium tin oxide. The lens of claim 1 further comprising an alignment layer surrounding the liquid crystal layer. The lens of claim 14, wherein the alignment layer is polyvinyl alcohol. The lens of claim 14, wherein the alignment layer is nylon 6,6. The lens of claim 1 wherein the transparent substrates are separated by a distance of between about 3 microns and about 20 microns. The lens of claim 1, wherein the focal length is positive. The lens of claim 1, wherein the focal length is negative. A method of adjusting a focal length of a lens to an integral multiple of an initial focal length F, comprising: providing a lens comprising a liquid crystal layer enclosed between a pair of transparent substrates; a Fresnel zone patterned electrode Between the liquid crystal layer and the inwardly facing surface of the first transparent substrate, the patterned electrode has M regions, each region has L sub-regions, and the patterned electrode has a The total number is M. L individual addressable electrodes, wherein M and L are positive integers greater than or equal to 2, wherein in each of the M regions, when the radial position of the individual addressable sub-region increases, then Each of the L individual addressable sub-regions has a reduced radial extent; a conductive layer between the liquid crystal layer and an inwardly facing surface of the second transparent substrate; and an electrical control electrically coupled to the An electrode region and the conductive layer; and applying the same voltage to each of the K individual addressable electrodes to adjust the focal length to k. F, where k is a from 1 to M. An integer of L. The method of claim 20, wherein the applied voltage is between minus 3 volts and plus 3 volts. A method for continuously adjusting a focal length of a lens, comprising: (a) providing a lens, the lens comprising a liquid crystal layer enclosed between a pair of transparent substrates; and having M regions and L diffraction levels a Fresnel zone patterned electrode disposed between the liquid crystal layer and an inwardly facing surface of the first transparent substrate, wherein M is a positive integer greater than or equal to 2, and the patterned electrodes are individually addressable rings a circular array; a conductive layer between the surface of the liquid crystal layer and the inward facing surface of the second transparent substrate; and an electrical control electrically connected to the electrode regions and the conductive layer; Determining the design focal length; (c) calculating the area of the mth region of the Fresnel zone patterned electrode using the following equation: Where f is the design focal length and λ is the design wavelength; (d) dividing the calculated area of the mth region by L or a larger integer to determine a plurality of individually addressable electrodes forming a design sub-region; (e) applying the same voltage to the plurality of individually addressable electrodes in a design sub-region, wherein each region is comprised of L sub-regions of the same area, wherein L is a positive integer greater than or equal to two. The method of claim 22, further comprising, prior to step (a), determining one or more design focal lengths; calculating a maximum of the Fresnel zone patterned electrodes that allows all of the design focal lengths to be formed in a design sub-region size. The method of claim 22, further comprising determining the design focal length using a ranging device to determine a distance between the lens and a desired target. The method of claim 22, wherein the applied voltage is between minus 3 volts and plus 3 volts. The method of claim 22, wherein an outer diameter of the nth sub-region of the m-th zone is given by: The method of claim 26, wherein the focal length p. f, the area of each zone is p. r ₁ ² , where p is a positive integer. The method of claim 22, wherein the Fresnel zone pattern is in a period of r ² .