HK1137069B - Method to reduce power consumption with electro-optic lenses - Google Patents

Description

Method for reducing power consumption using electro-optic lens

Cross Reference to Related Applications

This application claims priority from U.S. provisional application No. 60/804,494 filed on 12.6.2006.

Background

The invention relates to an electro-optic lens with reduced power consumption.

Electro-optical devices have been developed for use in many applications, including ophthalmic lenses (lenses), optical systems, liquid crystal displays, and other devices. Among other benefits, it is particularly desirable that the power required for driving the device be as low as possible to achieve long device life before recharging and to allow the use of a smaller power source.

Disclosure of Invention

An electro-optical device with reduced power consumption is provided. More specifically, there is provided an electro-optical device comprising: a liquid crystal layer between a pair of opposing transparent substrates; a patterned electrode set located between the liquid crystal layer and an inwardly-facing (inward-facing) surface of the first transparent substrate; a conductive layer between the liquid crystal layer and the inwardly facing surface of the second transparent substrate; and means for applying a voltage to the patterned electrode set and the conductive layer, wherein the voltage applied to the conductive layer is below a threshold voltage (RMS voltage difference, above which the optical transmission of the liquid crystal layer changes). In one particular embodiment, the voltage difference between the voltage applied to the patterned electrode set and the voltage applied to the conductive layer is sufficient to provide a desired amount of change in light transmission in the liquid crystal.

As is known in the art, liquid crystals with a substantially uniform (homogenic) alignment have an interfacial anchoring energy (anchoring energy) and an effective elastic constant (significant elastic constant) which is induced at a threshold level (V)_Th) There is no director redirection at the RMS voltage below. If the RMS voltage applied across the liquid crystal is higher than V_ThThe director is redirected and the light transmission changes until saturation is reached. In previous designs, to redirect the liquid crystal, a voltage was applied across the liquid crystal using the conductive layer as ground. The applied voltage is at least the sum of the threshold voltage and an additional amount of voltage for redirecting the director to the desired degree. In the present invention, the conductive layer (unpatterned electrode) is driven around a threshold voltage. This enables the patterned electrode to be driven at a lower voltage than previously designed.

In one example of the current invention, the threshold voltage is about 1.3V RMS. In this case, a voltage of less than 1.3V RMS is applied to the conductive layer. The voltage applied to the patterned electrodes is sufficient to cause the liquid crystal director to reorient, thereby providing the desired light transmission. This voltage is less than in previous designs.

The apparatus of the invention may be used in a variety of applications known in the art, including lenses for human or animal vision correction or modification. These lenses may be included in eyeglasses, as is known in the art. The eyewear can include one or more lenses. The device may also be used in display applications, as known to those of ordinary skill in the art without undue experimentation. The lenses of the invention can be used with conventional lenses and optics.

The apparatus of the present invention provides a number of advantages over other designs. Previous work has shown that electronic drivers driving liquid crystals consume most of the power supply. The use of the invention reduces the power consumed by the electronics driving the liquid crystal. By using the invention, a lower voltage power supply can be used. Since the device described herein can be used as part of an eyewear (eyewear), where the power supply can be a battery, a lower voltage power supply will enable the use of a smaller battery, and reduced power consumption will extend the time between battery charges.

Brief Description of Drawings

Fig. 1 shows a diagram of a liquid crystal cell.

Figure 2 shows a previous design in which a voltage is applied across the liquid crystal cell.

Fig. 3 shows an example of a patterned electrode set.

Figure 4 illustrates the use of an inverted square wave driver.

Detailed Description

The following description provides non-limiting details of the electro-optic lenses that make up the invention. The present invention provides electro-optic lenses filled with liquid crystal material that can be rearranged in an electric field. The lens is used as a Diffractive Optical Element (DOE). The DOE is the result of applying a voltage across a thin liquid crystal layer that responds by changing the director orientation field and generates a non-uniform refractive index pattern that then causes a non-uniform phase transfer function across the face of the cell. Accurate control of the PTF is achieved by applying an accurately controlled voltage difference across the cell by driving patterned electrode sets and conductive layers to produce the desired DOE.

The electro-optic lens used in the present invention is a diffractive lens that uses a patterned set of electrodes to produce a desired phase retardation profile that allows the lens to function as a band-plate lens. Diffractive lenses are known in the art. The function of the diffractive lens is based on near field diffraction of a Fresnel-zone pattern (Fresnel pattern). Each point emerging from the structure acts as an emitter (emitter) of a spherical wave. The light field at a particular observation point is the sum of the components of the spherical wave that emanates across the structure. Constructive interference of spherical waves from the various points produces a high intensity at the observation point corresponding to a high diffraction efficiency.

Liquid crystal cells are known in the art. All art-known cell configurations and operations of liquid crystal cells are incorporated by reference to the extent that they are not inconsistent with the disclosure herein. As an example, consider an electro-active (electro-active) liquid crystal cell, as shown in fig. 1, in which a liquid crystal material (20) is sandwiched between two substrates (100, 10) having conductive inner surfaces (40, 30). The substrates can 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 conductive layer 30 is patterned (patterrn) with a patterned electrode set to provide a desired diffraction pattern. The patterned electrode comprises an annular array of rings with a radius determined by the desired focal length, as disclosed elsewhere (see, e.g., the references cited herein and U.S. application 2004/0223113). The patterned electrode is fabricated by photolithographic processing or other known techniques of a conductive film deposited on a substrate, as is known in the art. Fig. 3 illustrates a layout of one example of the electrode pattern. Adjacent areas are distinguished by gray and black. Each ring electrode can be addressed independently by adding an electrically insulating layer (indicated by dots) with vias. The conductive layer 40 is not patterned. The conductive material used for the conductive layer can be any suitable material, including those specifically illustrated herein as well as other materials known in the art. Preferably, the conductive material is transparent, such as indium oxide, tin oxide, or Indium Tin Oxide (ITO). The thickness of each conductive layer is typically between 30nm and 200 nm. The layer must be thick enough to provide adequate conduction, but need not be so thick as to provide for the entire lens structureA large thickness. The substrates are held at a desired distance using spacers (60) or other means known in the art. The spacers may be any desired material such as mylar, glass, or quartz, or other material useful for providing the desired spacing. To achieve efficient diffraction, the liquid crystal layer must be thick enough to provide an active retardation wave (d > λ/δ n-2.5 μm, where δ n is the birefringence of the liquid crystal medium), but thicker liquid crystal layers help avoid saturation phenomena. The disadvantages of thicker cells include long switching times (with d)²But changes) and loss of definition of the electro-optic features. In certain embodiments, the transparent substrates are spaced apart by 3-20 microns and all individual values and ranges therein. One presently preferred spacing is 5 microns. The surface of the substrate is coated with an alignment layer (50) such as polyvinyl alcohol (PVA) or nylon 6, 6 and treated by rubbing to give a uniform director orientation. Preferably, the alignment layer on one substrate is rubbed anti-parallel to the alignment layer on the other substrate, as indicated by the arrows in fig. 2. This enables a correct alignment of the liquid crystals, as known in the art.

A voltage is applied to the patterned electrode set and conductive layer using means known in the art. In the previous lens configuration, a voltage was applied to the inner conductive surface of the substrate as shown in FIG. 2. The symbols used in fig. 2 are conventional in the art. In the previous lens configuration, one conductive layer was used as ground. In one embodiment of the present invention, one drive unit is attached to the conductive layer and another drive unit is attached to the patterned electrode set. As is known in the art, electrical contact to the electrodes can be achieved using thin wires or conductive strips at the edge of the lens, or through a set of conductive vias under the lens. As is known in the art, the voltages applied to the conductive layer and patterned electrode set depend on the particular liquid crystal used, the thickness of the liquid crystal in the cell, the desired light transmission, and other factors. The actual voltage used can be determined by one of ordinary skill in the art without undue experimentation using common general knowledge in the art and the disclosure herein. It is known in the art that various methods for controlling all aspects of the voltage applied to the electrodes can be used, including processors, microprocessors, integrated circuits, and computer chips.

Since voltages are not absolute physical quantities, they must be specified with respect to a reference (e.g., local, battery pole, or power terminal). Thus, in practice, the voltage that changes the pressure on and stress in the Liquid Crystal (LC) film is determined by the difference between the voltages at the electrodes on the opposite sides of the film. It is known that the LC film changes (writes) to higher frequencies of these voltage differences<V²>^1/2) The RMS average of (c) slowly (at a low frequency) responds. To control such a membrane, one electrode is usually held at a fixed voltage V₂＝V_ref(e.g., locally). In such a case, if relative to V_refTo represent the voltage, the voltage V is modulated_rmsCompletely by the voltage V on the other electrode₁Is determined by the state of (behavior):

V_rms＝<(V₁-V₂)²>^1/2＝<(V₁-V_ref)²>^1/2＝<(V₁)²>^1/2

however, if V₂Is not maintained at V_refThen can only say

V_rms＝<(V₁-V₂)²>^1/2

In this case, the synchronization of the electrode drive voltages may be such that V_rmsThe values of (b) occur in the following ranges:

V_rms1+V_rms2≥V_rms≥|V_rms1-V_rms2|

as an important example, it is shown in FIG. 4 that an inverted square wave drive is used to provide a large modulation V from two lower voltage drivers_rms. Obviously, V can be converted into₂Is kept constant as amplitude V_SW2And can apply V₁As amplitude V_SW1Can be changed, and V₂Square waves 180 degrees out of phase to achieve the desired control voltage. For this case, as shown in figure 4,

V_rms＝V_rms1+V_rms2＝V_sw1+V_sw2

thus, as referred to herein, if V is to be_rms2＝V_sw2Set close to, but below, the threshold voltage of the LC film, a smaller V may be used_rms1＝V_sw1To control the LC DOE. (alternative: fixing V_sw1And the phase difference between the square waves is varied to achieve a desired V in the following range_rms：

V_sw1+V_sw2≥V_rms≥|V_sw1-V_sw2|

。)

The use of square waves is illustrative, but is merely a simple example. V can be achieved by controlling the amplitude and phase of other drive waveforms (e.g., sine waves, imperfect square waves, and other methods known in the art)_rmsSimilar control of (2).

As used herein, a "layer" does not require a completely uniform film. There may be uneven thickness, cracks or other defects as long as the layer performs its intended purpose as described herein. As used herein, "patterned electrode set" refers to one or more regions of conductive material disposed in a pattern on a substrate, along with one or more regions of insulating material disposed in a pattern complementary to the conductive material regions on the substrate.

The liquid crystal used in the present invention includes those forming a nematic phase, a smectic liquid crystal molecular phase or a cholesteric phase having a long-distance alignment order that can be controlled by an electric field. Preferably, the liquid crystal has a wide nematic temperature range, easy alignment (easy alignment), low threshold voltage, large electro-optic response and fast switching speed, as well as proven stability and reliable commercial availability. In a preferred embodiment, E7 (nematic liquid crystal mixture of cyanobiphenyl and cyanobiphenyl (cyanoterphenyls) sold by Merck) is used. Examples of other nematic liquid crystals that can be used in the present invention are: pentyl-cyano-biphenyl (5CB), (n-benzophenone (octyloxy)) -4-cyanobiphenyl (80 CB). Other examples of liquid crystals that may be used in the present invention are the compounds 4-cyano-4-n-alkylbiphenyl, 4-n-pentyloxy-biphenyl, 4-cyano-4 "-n-alkyl-p-terphenyl, n ═ 3, 4, 5, 6, 7, 8, 9, and commercial mixtures such as the E36, E46 and ZLI series manufactured by BDH (British Drug House) -Merck.

Electroactive polymers may also be used in the present invention. Electroactive Polymers include any transparent optically polymeric material such as those disclosed in "Physical Properties of Polymers Handbook", american society of physics, Woodburry, n.y., 1996, by j.e. mark, which comprise molecules having asymmetrically polarized conjugated p-electrons between donor and recipient groups (called chromophores), such as those disclosed in "Organic Nonlinear Optical Materials", Gordon and berberlacech publications, Amsterdam, 1995, by ch.bosshad et al. Examples of polymers are as follows: polystyrene, polycarbonate, polymethyl methacrylate, polyvinylcarbazole, polyimide, polysilane. Examples of chromophores are: p-nitroaniline (PNA), disperse Red 1(DR 1), 3-methyl-4-methoxy-4' -nitrostilbene (nitrostilbene), Diethylaminonitrostilbene (DANS), diethyl-thio-barbituric acid. As known in the art, electroactive polymers can be made by the following method: a) following the guest/host approach, b) by covalent incorporation of chromophores into the polymer (pendant and backbone), and/or c) by lattice hardening methods such as cross-linking.

Polymer Liquid Crystals (PLC) may also be used in the present invention. Polymeric liquid crystals are sometimes also referred to as liquid crystal polymers, low molecular mass liquid crystals, self-strengthening polymers, in situ composites, and/or molecular composites. PLC is a copolymer containing both relatively rigid and flexible sequences, such as the "Liquid crystal Polymers" edited by w.brostow, a.a.collyer, Elsevier: FromStructures to Applications ", New-York-London, 1992, Chapter 1. Examples of PLCs are: polymethacrylates and other similar compounds that include pendant 4-cyanophenyltoluate groups.

Polymer dispersed liquid crystal (polymer dispersed liquid crystal PDLC) may also be used in the present invention. PDLC consists of a dispersion (dispersion) of liquid crystal droplets in a polymer matrix. As is known in the art, these materials can be manufactured in several ways: (i) phase alignment by Nematic Curves (NCAP), phase separation by Thermal Induced (TIPS), Solvent Induced (SIPS) and Polymerization Induced (PIPS). Examples of PDLCs are: a mixture of liquid crystals E7(BDH-Merck) and NOA65(Norland products, Inc. NJ); a mixture of E44(BDH-Merck) and Polymethylmethacrylate (PMMA); a mixture of E49(BDH-Merck) and PMMA; a mixture of the monomer dipentaerythriol hydroxypentaacrylate, liquid crystal E7, N-vinylpyrrolidone, N-phenylglycine and the dye rose bengal.

Polymer Stabilized Liquid Crystals (PSLCs) can 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% of the liquid crystals by weight. The photopolymerizable monomers are mixed together with the liquid crystal and the UV polymerization initiator. After alignment of the liquid crystals, polymerization of the monomers is initiated, typically by UV exposure, and the resulting polymer forms a network of stable liquid crystals. For an example of PSLC, see, for example: hudson et al, Optical studio and isocyanate Networks in Polymer-Stabilized Liquid Crystals, Journal of Society for Information Display, vol.5/3, 1-5, (1997), Photoreflectance in Polymer-Stabilized neutral Crystals, G.P.Wiederrecht et al, J.of am.Chem.Soc., 1203231-.

Self-assembling nonlinear supramolecular structures may also be used in the present invention. Self-assembled nonlinear supramolecular structures include electroactive asymmetric organic films that can be fabricated using the following methods: langmuir-blodgett films, alternating polyelectrolyte deposition from aqueous solutions (polyanions/polycations), molecular beam epitaxy, timing integration of covalent coupling reactions (e.g., organotrichlorosilane-based self-assembled multilayer deposition). These techniques typically produce thin films having a thickness of less than about 1 μm.

Combinations of components or each device described or illustrated herein can be used to practice the invention unless otherwise claimed. Other components such as drivers for applying the voltages used, controllers for the voltages, and any other required optical elements are known to those of ordinary skill in the art and are included without undue experimentation. The particular names of the compounds are intended to be exemplary, as it is understood that one of ordinary skill in the art may name the same compounds differently.

When a compound is described herein as an isomer or enantiomer of the compound that is not specific, for example, in molecular formula or chemical name, the description is intended to include each isomer or enantiomer of the compound described alone or in combination. It will be appreciated by those of ordinary skill in the art that methods, apparatus elements, starting materials, and methods of manufacture other than those specifically illustrated may be employed in the practice of the present invention without undue experimentation. All functional equivalents, any such methods, apparatus elements, starting materials, and methods of manufacture known in the art are intended to be included herein. Whenever a range is given in this specification, for example, a thickness range or a voltage range, all intermediate ranges and subranges as well as all individual values included in the given range are intended to be included in the disclosure.

As used herein, "comprising" is synonymous with "including," "comprising," or "characterized by," and is inclusive or extensible 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 claim 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. Any recitation herein of the word "comprising", particularly in the context of a description of components of the composition or of elements of the apparatus, is understood to encompass those compositions and methods that consist essentially of, or consist of, the recited components or elements. The invention illustratively described herein suitably may be practiced in the absence of any element(s), limitation(s), or limitations that 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 words used herein have their art-recognized meanings as may be found by reference to standard texts, reference journals, and backgrounds known to those skilled in the art. Specific definitions are provided herein to clarify their use in the context of the present invention. All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled 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 preferred embodiments are exemplary and are not intended as limitations on the scope of the invention. Modifications and other uses of the invention which are encompassed within the spirit of the invention will readily occur to those skilled in the art, as defined by the scope of the claims.

All documents cited herein are hereby incorporated by reference to the extent they are not inconsistent with the disclosure of this specification. Some of the documents provided herein are incorporated herein by reference to provide details regarding other device components, other liquid crystal cell configurations, other patterned electrode patterns, other analytical methods, and other uses of the present invention.

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. The present invention is not limited in use to eyeglasses. Rather, the present invention is useful in other fields such as telecommunications, optical switches and medical devices, as known to those of ordinary skill in the art. As known to those of ordinary skill in the art, any liquid crystal or mixture of liquid crystals that provides a desired phase transfer function at a desired wavelength is useful in the present invention. It is known in the art to determine an appropriate voltage and apply the appropriate voltage to the liquid crystal material to produce the desired phase transfer function.

Reference to the literature

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

Vdovin et al, On the availability of intraocular adaptive optics (investigation of the possibilities of intraocular adaptive optics), opt express 11: 810-817, 2003.

Williams et al, Electrically controllable liquid crystal Fresnel lens, proc. spie 1168: 352-357, 1989.

Patel et al, Electrically controlled polarization-independent liquid crystal Fresnel lens arrays, opt. lett.16: 532-534, 1991.

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

M.c. k.wiltshire, Non-display applications of liquid crystal devices, Geo j.research 10: 119-125, 1993.

Ren et al, mobile Fresnel lens using nanoscopic polymer-dispersed crystals (Tunable Fresnel lenses using nanoscale polymer dispersed liquid crystals), appl. phys. lett.83: 1515-1517, 2003.

Fowler et al, Liquid crystal lens review (Liquid crystal lens ensemble), ophthal. physiol. opt.10: 186-194, 1990.

Futhey, diffraction bifocal intraocular lens (Diffractive bifocal intraocular lens), Proc. SPIE 1052: 142-149, 1989.

Sato et al, Variable-focus liquid crystal Fresnel lenses, jpn.j.appl.phys.24: L626-L628, 1985.

Command et al, Variable focal length microlenses (Variable focal length microlenses), opt, command.177: 157-170, 2000.

S.t. kowel et al, Focusing by electrical modulation of diffraction in an analog crystal cell (Focusing by electrical modulation of refraction in a liquid crystal cell), appl.opt.23: 278-289, 1984.

Nouhi et al, Adaptive spherical lenses, appl. opt.23: 2774-2777, 1984.

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

Loktev et al, Wave front control systems based on modal liquid crystal lenses, rev. sci. instrum.71: 3190-3297, 2000.

Riza et al, Three-terminal adaptive liquid-crystal lens apparatus, opt. Lett.19: 1013-1015, 1994.

Mcowan et al, a switchable liquid crystal binary Gabor lens, opt. 189-193, 1993.

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

Kress et al, Digital diffraction Optics, john wiley & Sons ltd, 2000.

Claims (11)

1. An electro-optical device comprising:

a liquid crystal layer between a pair of opposing transparent substrates;

a patterned electrode set disposed between the liquid crystal layer and the inwardly facing surface of the first transparent substrate;

a conductive layer between the liquid crystal layer and the inwardly facing surface of the second transparent substrate, the conductive layer being electrically connected to the set of patterned electrodes; and

means for applying a voltage to the patterned electrode set and the conductive layer,

wherein the RMS voltage applied to the conductive layer is below and close to a threshold voltage required for light transmission change of the liquid crystal layer, and the RMS voltage difference between the voltage applied to the patterned electrode set and the voltage applied to the conductive layer is sufficient to provide a desired light transmission change amount in the liquid crystal.

2. The device of claim 1, wherein the liquid crystal is E7.

3. The apparatus of claim 1, wherein the transparent substrate is glass.

4. The device of claim 1, wherein the transparent substrate is plastic.

5. The device of claim 1, wherein the electrode and the conductive layer are indium tin oxide.

6. The device of claim 1, further comprising an alignment layer surrounding the liquid crystal layer.

7. The apparatus of claim 6, wherein the alignment layer is polyvinyl alcohol.

8. The device of claim 6, wherein the alignment layer is nylon 6, 6.

9. The device of claim 1, wherein the transparent substrates are spaced apart by 3-20 microns.

10. The device of claim 9, wherein the transparent substrates are spaced apart by 3-8 microns.

11. A method for diffracting light, comprising:

providing a liquid crystal layer between a pair of opposing transparent substrates;

positioning a patterned electrode assembly between the liquid crystal layer and the inwardly facing surface of the first transparent substrate; and

positioning a conductive layer between the liquid crystal layer and the inwardly facing surface of the second transparent substrate, the conductive layer being electrically connected to the set of patterned electrodes;

applying an RMS voltage to the conductive layer, wherein the RMS voltage is below and near a threshold voltage required for light transmission changes of the liquid crystal layer;

a voltage is applied to the patterned electrode set sufficient to provide a desired amount of change in optical transmission in the liquid crystal.