Patent Grant
8634137
1. Field of Technology
This disclosure relates to the mitigation of glare from reflective surfaces, for example, mirrored windows in a building.
2. Description of the Related Art
Partially reflective window coatings (e.g., thin films of sputtered metal) and films (e.g., metal-impregnated and Bragg mirror polymer films) have been widely used for decades as a method for reducing solar heat gain and thus improving the energy performance of buildings. The design, composition, and benefits of reflective coatings are well documented and need no further elaboration here, except to note that the reduction in solar heat gain, while clearly beneficial in hot, sunny conditions, may be detrimental in cold weather as it interferes with passive solar heating.
Switchable mirrors also exist which are based on reversible metal hydride and metal lithide chemistry described, for example, in U.S. Pat. No. 7,042,615 to Richardson. These switchable mirrors, which are analogous to rechargeable batteries, may rely on the physical migration of ions across a barrier under the influence of an electric field and, therefore, have limited switching speeds and cycle lifetimes. In addition, electrically operated “light valves” that combine liquid crystals with one or more reflective polarizers are described, for example, in U.S. Pat. No. 6,486,997 to Bruzzone et al. In these devices, a liquid crystal typically serves as an electrotropic depolarizer, i.e., a means of variably altering or rotating the polarity of the light that passes through it under the influence of an electric field. Some of these devices can be thought of as switchable mirrors, although they are rarely described that way, since their primary application is in video displays and advanced optics.
Switchable electric light valves which do not require polarizers but are diffusive forward scatterers or diffusive reflectors also exist. This is because liquid crystals may in fact be Bragg reflectors with different reflection bands in these applications, with a reflective, diffusive, or forward-scattering mode, and a more transmissive mode. These include the polymer-dispersed liquid crystal (PDLC) display, the cholesteric liquid crystal display (Ch-LCD), the Halmeier display, and the Guest-Host display. The PDLC is an electrochromic device where the index of refraction of liquid crystal droplets embedded in another material is changed electrically, resulting in more scattering of the light in one mode than another. The Ch-LCD has two stable states, the reflective planar and focal conic texture. The reflective planar structure reflects light if the Bragg reflection condition is met and thus acts as a Bragg reflector for one circular polarization of light, while the reflective focal conic transmits more of the light. The Guest-host display utilizes dyes dispersed in a liquid crystal, which absorb more light when in one orientation than in another. The orientation of the dyes is dependent on the orientation of the liquid crystal, which can be determined using an electric voltage. Polymer stabilized liquid crystals are created when polymers and liquid crystals are mixed and photopolymerized together to among other things establish the orientation of the liquid crystals.
In addition, U.S. Pat. No. 6,288,840 to Perkins et al., discloses a type of reflective polarizer called a “wire grid polarizer” which consists of a nanoscale array of closely spaced, parallel metal wires on a transparent substrate, such that light of one linear polarity which strikes the wires is reflected while light of opposite linear polarity is transmitted through the substrate. Wire grid polarizers may be a component of some reflective and thermoreflective optical filters. It is additionally possible to construct polarizers using distributed Bragg reflector technology, such as 3M's Dual Brightness Enhancement Film (DBEF). In these polarizers, some layers have different optical indices in one transverse direction than in another, creating a polarizer.
Any surface which presents a mirror finish in the presence of a light source, whether indoors or outdoors, has the potential to create glare, i.e., a condition in which background illumination approaches, equals, or exceeds the illumination of objects in the foreground, which in some case can lead to discomfort or reduced visibility. For this reason, mirrored films are banned or discouraged in some jurisdictions and are the subject of increased scrutiny in others.
Antireflection coatings are widely used to reduce glare from bright light sources on transparent optics such as eyeglass and binocular lenses. Reflection from a transparent surface occurs because the index of refraction of the transparent material does not match that of the surrounding medium (e.g., air, water, or vacuum). The greater the mismatch, the greater the reflection. A standard antireflection coating has an index of refraction approximately halfway between that of the transparent material and the surrounding medium. More sophisticated, nanostructured coatings (e.g., arrays of vertically oriented nanoscale cones) may present an outer surface which is mostly air and thus has an index of refraction close to air, and an inner surface which is mostly solid and has an index of refraction essentially identical to the transparent material on which it sits. In this case, reflection may be reduced virtually to zero.
However the high reflectivity of a polished metal surface, dielectric mirror, distributed Bragg reflector, or other mirror does not rely on an index of refraction mismatch with the surrounding air. Instead, reflection is achieved by photon interaction with conduction electrons (e.g., in a metal) or by constructive and destructive interference between layers of different material (e.g., in a dielectric mirror). Thus, a transparent antireflection coating will have little effect on the reflectivity of such mirrors. However, a diffusive coating will cause the reflected light to be scattered, producing a white surface which may still be highly reflective, but not specular (i.e., mirror-like) and therefore not capable of reflecting or transmitting an intelligible, collimated image.
In addition, there are numerous examples of “metamaterials” or nanostructured materials or devices which interfere with light waves in such a way that the material appears to have a negative index of refraction and thus to violate many of the presumed “laws” of classical optics. The scientific paper “Asymmetric Propagation of Electromagnetic Waves through a Planar Chiral Structure” (V. A. Fedotov, P. L. Mladyonov, S. L. Prosvirnin, A. V. Rogacheva, Y. Chen, and N. I. Zheludev, Physical Review Letters 97, 167401, 17 Oct. 2006) discloses a chiral, planar structure consisting of “fish scale” patterns of aluminum nanowire on a transparent substrate. In essence, the structure is a type of wire grid polarizer, although one that reflects and transmits circularly polarized light rather than linearly polarized light. Because its chiral nature is different depending on which surface of the polarizer is being observed, for light of mixed, random polarity (e.g., sunlight), this structure has an additional property of being asymmetrically transmissive, i.e., it is more transmissive to light passing through it in one direction than in the other.
In addition, there are numerous varieties of optical diffusers, including etched glass and polymer films, which partially randomize the direction of photons passing through them, while exhibiting modest reflection and very low absorption. In the case of “forward scattering” diffusers which affect the direction of most incident light by substantially less than 90 degrees, as much as 80% of the light striking the diffuser is passed through, with less than 20% being absorbed or reflected back. Diffusers are commonly employed in privacy windows, skylights, video displays, and electric lighting.
There are also so-called “one-way mirrors” which are commonly used as privacy windows, particularly in building interiors (e.g., to separate a supervisor's office from the workers being supervised). However, these are not true one-way devices. Rather, they are simply partially mirrored transparent glass, equally reflective in both directions, and the “one-way” effect requires that the area on one side of the glass be more brightly illuminated than the area on the other side. If these lighting conditions are reversed, then the privacy effect is reversed as well (e.g., the supervisor may see his own reflection, whereas the employees may have a clear view of the supervisor).
Finally, various types of prismatic films use etched structures or variable index of refraction structures to bend the light passing through them. Examples include Fresnel concentrating lenses and polymer “privacy filters” that can be applied to laptop screens or video displays to narrow or widen the viewing angle.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded as subject matter by which the scope of the invention is to be bound.
Variable, selective, or asymmetric diffusive optics may be used to mitigate the effects of glare from reflective or thermoreflective surfaces. This technology has particular, but not exclusive, application as a glare reduction method for building surfaces.
The specular reflection from a surface may be disrupted by diffusive optics placed between the surface and the outside world, thus giving the surface a diffusive (i.e., white or metallic gray) finish as opposed to a specular (i.e., mirrored) finish. However, the nature of the diffusive optics may be carefully selected such that the transmission of specular light (i.e., an image) through the exterior surface and interior surface (e.g., through a window and into a building) is minimally disrupted under selected conditions.
In one implementation, a method is provided for reducing glare from partially reflective or thermoreflective surfaces without significantly degrading the energy benefits of reflection. The method involves placing an at least partially diffusive filter between either a partially reflective surface or a thermoreflective surface and an external light source. When light is transmitted through the partially reflective surface or the thermoreflective surface, it is diffused only once. However, when light is reflected from the partially reflective surface or the thermoreflective surface, it is diffused twice, thereby transforming specular reflections from the partially reflective surface or the thermoreflective surface into diffusive reflections.
In another implementation a method is provided for increasing the privacy of transparent, translucent, or partially reflective surfaces. The method involves placing an at least partially diffusive filter between either a transparent surface, a translucent surface, or a partially reflective surface and an external light source. When light is transmitted through the transparent surface, the translucent surface, or the partially reflective surface, it is diffused only once. However, when light is reflected from the transparent, translucent, or partially reflective surface, it is diffused twice, so that the reflected light is approximately twice as diffuse as the transmitted light.
In a further implementation an energy-efficient device is disclosed that reduces glare from reflection of incident radiant energy. The device may be composed of a first diffusively reflective polarizer, a second diffusively reflective polarizer, a depolarizer positioned between the first diffusively reflective polarizer and the second polarizer, and a transparent substrate affixed to the second diffusively reflective polarizer.
In yet another implementation, an energy-efficient device is described that reduces glare from reflection of incident radiant energy. The device may be composed of a first diffusively reflective polarizer, a second diffusively reflective polarizer, a depolarizer positioned between the first diffusively reflective polarizer and the second polarizer, and a transparent substrate affixed to the second diffusively reflective polarizer
In an additional implementation a diffusive polarizing filter is disclosed. The diffusive polarizing filter may be composed of a grid of wires with irregular surfaces placed in parallel at a regular spacing. The surface irregularities are larger than wavelengths of incident light resulting in reflected light from the incident light of a first polarity that is diffuse while transmitted light from the incident light of a second polarity is collimated.
In a further implementation of a diffusive polarizing filter, a grid of wires is placed on the non-planar substrate. The reflection of incident light from the diffusive polarizing filter exhibits a dependency between an incident angle of the incident light and a departure angle of the incident light that varies with a contact location of the incident light on the substrate.
In yet another implementation, a glare-reducing polarizing filter is composed of a grid of metamaterial wires that form chiral structures. The grid is more diffusive to light passing through in a first direction than to light passing through in a second, opposite direction. The grid also passes collimated light in the second direction.
In an alternative implementation, a method to improve the suitability of liquid crystal-based thermotropic, thermochromic, or thermoreflective filters and devices for low glare applications is disclosed. The method involves selecting a mixture of or including liquid crystals with suitable freezing and clearing points for operation in a given climate. Next, additives are selected to affect properties of a transition of the liquid crystals between physical states. Then, the mixture and the additives are combined to adjust or select optical properties of transmission, absorption, and/or reflection of light or energy by the filters and devices.
In another implementation, a thermotropic distributed Bragg reflector device is disclosed. The device may be composed of two or more layers of a first material that is transparent or translucent and that has a first index of refraction, and two or more layers of a second material that is thermotropic, that is transparent or translucent, and that has a variable second index of refraction. Each of the layers of the second material is interleaved with respective layers of the first material. Below a threshold temperature, the first index of refraction is substantially the same as the second index of refraction. Above the threshold temperature, the second index of refraction changes to become substantially different from the first index of refraction.
In a further implementation, a method for producing a thermoreflective effect in a first direction and a thermoabsorptive effect in a second direction is disclosed. The method includes first interleaving layers of an absorptive polarizer film and a reflective polarizer film. Second, a thermotropic depolarizer is interposed between a first set of layers of the absorptive polarizer film and the reflective polarizer film and a second set of layers of the absorptive polarizer film and the reflective polarizer film.
Use of diffusive optical sheets or films as described herein may allow builders, architects, building owners, and vehicle designers to reap the energy benefits of reflective and thermoreflective materials, while minimizing external and/or internal glare from building or vehicle surfaces. It may also provide an aesthetic alternative to mirror finishes for building and vehicle exteriors with little or no harm to energy efficiency and may further reduce reflective window glare for inside and/or outside observers while permitting a clear view of the outside for building or vehicle occupants. Such diffusive optics may provide privacy for building and vehicle interiors, similar to diffusive “privacy glass” but with significantly less effect on the view from inside.
This technology may use both specular and diffusive technologies to create windows for transparent and privacy type models of windows, and prevent the concentration of reflected solar energy in UV, visible, or IR bands in different ways. This technology may also be used to reflect or transmit, diffusively or specularly, various polarizations and frequency ranges of light in different ways at different temperatures to reduce glare.
Other features, details, utilities, and advantages of the present invention may be apparent from the following more particular written description of various embodiments of the invention as further illustrated in the accompanying drawings and defined in the appended claims.
Please note that closely related elements have the same element numbers in all figures.
Variable, selective, or asymmetric diffusive optics may be used to reduce specular reflection from mirrored surfaces, including reflective and thermoreflective building materials. For the purposes of this specification, the term “thermoreflective” shall refer to any object, device, or material having a reflectivity that varies as a function of temperature. Since glare is primarily a function of specular rather than diffusive reflection of a bright light source, this technology may reduce glare from building, vehicle, and other surfaces.
U.S. patent application Ser. No. 12/019,602 to McCarthy et. al. discloses “thermoreflective” window filters that are largely transparent when cold and largely reflective when hot, and which may be used to regulate the temperatures of buildings when incorporated into windows. One possible embodiment based upon the disclosure is a passive temperature-regulating film for use as a construction material, which may comprise an appliqué that can be affixed to glass windows having a single bandblock filter. For example, a thermochromic, distributed Bragg reflector (i.e., a reflector based on periodic changes in index of refraction) may be composed of a liquid crystal formulated to reflect a certain percentage of the incident visible light above a given threshold temperature and can be constructed such that its reflection band occurs in the infrared. Such a filter may offer numerous advantages over a simple mirrored film because the amount of reflectivity—and thus solar heat gain reduction—may vary significantly between hot and cold weather.
Once it has passed through the outer reflective polarizing filter 101, the incoming light may enter the thermotropic depolarizer 102, which is a device or material capable of exhibiting two different polarizing states. In its hot or isotropic or liquid state, the polarized light passing through the thermotropic depolarizer 102 may not be affected. In its cold (e.g., nematic or crystalline) state, the thermotropic depolarizer 102 may rotate the polarization vector of the incoming light by a fixed amount.
Once it has passed through the thermotropic depolarizer 102, the remaining polarized light may strike the inner reflective polarizer 103, also known as the “analyzer,” where it is either reflected or transmitted depending on its polarization state. The inner reflective polarizer 103 may be oriented such that its polarization is perpendicular to that of the outer reflective polarizer 101. Thus, in the hot state of the filter device 100, when the polarization vector of the light has not been rotated, the polarity of the light may be perpendicular to that of the inner reflective polarizer 103 and approximately 100% of it may be reflected. However, in the cold state, when the polarization vector of the light has been rotated by 90 degrees and is parallel to the inner reflective polarizer 103, a small amount of the light may be absorbed by the polarizer material and the rest may be transmitted through.
In
Thus, in its cold state the filter device 100 may transmit slightly less than half the light energy which strikes its outer surface, whereas in its hot state the filter device 100 may in principle transmit substantially less than 1% of the light energy. As a result, the filter device 100 may be used to regulate the flow of light or radiant heat into a structure based on the temperature of the filter device 100.
This embodiment may be modified through the use of specialized reflective polarizers 101 and 103 whose design inherently limits glare. For example, circular polarizers made from cholesteric liquid crystals (CLCs) have the interesting property of being largely specular in transmission (i.e., they transmit a clear, minimally hazy image) but largely diffusive in reflection. Thus, when two reflective CLC circular polarizers of opposite handedness are stacked, the resulting reflection is diffuse, and resembles unpolished metal rather than presenting a mirrored surface.
Alternatively, the polarizers 101 and 103 may be retro-reflective polarizers. A retro-reflector is a device, film, surface, or substance that is reflective in nature, but which may tend to reflect light back in the direction of origin. Retro-reflectors include beaded reflective surfaces, as well as other textured or microtextured reflective surfaces. Retroreflectors are used, for example, in movie screens and in reflective “invisibility cloaks” or optical camouflage materials onto which a background image may be projected. When a reflective polarizer is structured such that its reflections are retro-reflections, the polarizer will tend to reflect light sources back toward their points of origin so that, for example, the light of the sun may be reflected back toward the sun rather than out toward adjacent buildings or down to the street, which may tend to reduce the impression of glare from a building or other object.
In a simple implementation, the diffuser 302 may be a diffuser with properties that do not vary with temperature, wavelength, polarity, incidence angle, electric field, or other similar factors. However, such a diffuser may be less than 100% diffusing. In this case, the light transmitted through the reflective surface (e.g., a partially mirrored window) passes through the diffuser only once, whereas the light reflected from the surface must pass through the diffuser twice. Therefore, the reflected light may be more diffuse than the transmitted light.
In other implementations, the diffusive filter 302 may fall into any of three broad types: 1) a variable diffuser with a light-scattering ability that may be controlled by external factors such as temperature; 2) a selective diffuser that may only diffuse light of particular wavelengths or particular polarity, while having little effect on the transmission of other wavelengths or polarities; and 3) an asymmetric diffuser with a scattering ability that may be direction-dependent, such that light passing through in one direction is more strongly scattered than light passing through in the opposite direction. In all three cases, the underlying objective is the same, i.e., to break up reflected light under certain conditions while allowing transmitted light, under the same or other conditions, to pass through with little distortion or attenuation. An exemplary use of this method is to allow a building to possess highly reflective or thermoreflective windows for energy efficiency in a jurisdiction where mirrored surfaces are banned or discouraged.
It should be noted that for certain types of thermoreflective filters and for certain types of diffusers, the diffuser may be located inside the thermoreflective filter (e.g., between two of the layers in a multilayered device) without altering the essential functions of either the diffuser or the thermoreflective filter.
By choosing the size and relative position of the beads or bubbles 404, the thermodiffusive filter 400 may be tuned such that its optical properties change with temperature. For example, the thermodiffusive filter 400 may be tuned such that it is a thermochromic diffusive Bragg reflector, diffusively reflecting certain frequency ranges of light. In another embodiment, the thermodiffusive filter 400 may be tuned to become a thermochromic diffusive scatterer operating over wide ranges of frequencies of light. In a further embodiment, the thermodiffusive filter 400 may be tuned to act as any of a thermochromic diffraction grating or disperser, thermochromic hologram, or other thermochromic optical device that reduces specularity of the reflected or transmitted light so as to reduce glare. An exemplary diffusive optical effect may be seen in river rapids, where opaque “whitewater” (i.e., water mixed with a large number of small, transparent air bubbles with a lower index of refraction than the water) can be seen alongside normal transparent water (with no air bubbles).
The temperature-dependent change in index or refraction may in principle be achieved by materials with high thermal expansion coefficients. Alternatively, one or both of the transparent materials 402 and 404 may be composed of a mixture of different materials which separate under certain conditions (e.g., above a certain temperature) or otherwise change their state or properties. However, the easiest way to produce this effect may be with materials that undergo a phase change at the desired temperature, such as a transition from liquid to solid or, in the case of a liquid crystal, any transition between nematic, smectic, crystalline, or isotropic states. In general this may produce a significant change in the index of refraction.
Since, in the mesophase (e.g., nematic and smectic states) liquid crystals may be anisotropic, the optical properties of beads or bubbles of liquid crystal suspended in a matrix (as in polymer dispersed liquid crystal devices) may be dependent on the orientation of the liquid crystal molecules. Many different ways to fix the orientation and structure of the liquid crystal in one or more states are known, including for example, using alignment layers or electric fields along with photo-polymerization. The orientation and structure of thermotropic liquid crystals is effected by temperature, and thus the anisotropy may be altered (or eliminated) by changing the temperature of the liquid crystal. One exemplary implementation of this embodiment utilizes a low-clearing point liquid crystal in a matrix structurally similar to polymer stabilized cholesteric or polymer diffusive liquid crystal devices, allowing phase changes due to changes in temperature (rather than electric fields) to effect optical transitions from transmissive to diffusive, or diffusive to transmissive. In another exemplary embodiment, the size and optical indices of the liquid crystal bubbles in a matrix structurally similar to polymer dispersed liquid crystal devices may be chosen such that a temperature-dependent diffusive reflection over one or more desired frequency ranges is achieved.
One exemplary use of this embodiment is to employ it in conjunction with a thermoreflective filter such that the transition temperature of the thermoreflective filter and that of the thermodiffusive filter are approximately the same. Thus, if the thermoreflective filter is 40% reflective in its cold state and 90% reflective in its hot state, and the thermodiffusive filter is 50% diffusive in its cold state and 80% diffusive in its hot state, then the total amount of specular reflection may remain approximately constant at a value of 20%, regardless of the state of the thermoreflective filter. Thus, the energy benefits of thermoreflective windows may be obtainable in a jurisdiction where building surfaces are legally restricted to 20% specular reflectivity. Another exemplary use of this embodiment is as a privacy filter.
A number of reflective, thermochromic implementations of this embodiment, which may change their reflective properties under the influence of temperature, may be practiced. One such device is a thermochromic, distributed Bragg reflector made such that the transmission, absorption, and/or reflection spectra are a function of temperature. Again, in this device liquid crystals may in fact be Bragg reflectors in which the reflection band is temperature-dependent. Distributed Bragg reflectors operate on the principle of mismatched optical indexes and the disclosed device may be considered a thermochromic version of a distributed Bragg reflector. Exemplary forms of thermochromic materials may include zinc oxide, which changes from clear to yellow when heated; liquid crystals, which can be formulated to absorb or reflect a percentage of the incident visible light above a given threshold temperature; and tungsten-doped vanadium oxides, which may reflect light above a threshold temperature determined in part by the percentage of tungsten in the composition of the material.
Differences in reflectivity of various liquid crystal formulations based on temperature depend on the formulation. In one formulation, the reflectivity may be altered with temperature due to a change in the index of refraction with temperature, and which is analogous to the electrochromic device known as polymer dispersed liquid crystal display. In another formulation, the reflectivity may be due to an internal structure which, at one temperature, reflects one circular polarization of light at certain frequencies and transmits the other circular polarization as well as other frequencies, while at other temperatures may transmit (or diffusively transmit) these frequencies. The behavior of such devices with temperature may be complicated, but may be analogous to the electrochromic devices known as cholesteric liquid crystal devices. Other formulations may be analogous to Guest-Host LCD displays, Halmeier displays, or polymer stabilized liquid crystal devices, though this list should not be considered exhaustive.
While each of these formulations may be used as a material in an exemplary thermochromic distributed Bragg reflector as depicted in
The bubbles depicted in
The liquid crystal 504 and its alignment layer or layers (not pictured) may be designed such that at low temperatures the liquid crystal 504 is in an ordered state (whether crystalline, smectic, nematic, discotic, or otherwise) and at high temperatures (i.e., above the clearing point of the liquid crystal) it is in a disordered (i.e., liquid or isotropic) state. Furthermore, the orientation of the liquid crystal molecules may be such that in the ordered state, the minimum energy configuration for the wire segments 502 is to be oriented perpendicular to the plane of the thermodiffusive filter 500 of which they are a part. Thus, light passing through the filter at a normal angle sees a very small cross section for the fibers 502 and is minimally reflected or refracted. Furthermore, because of the ordered state of the material, any visual distortion introduced by the filter may be relatively uniform and may therefore not result in significant scattering.
Conversely, in the hot state the reflective fibers 502 may become disordered and assume random orientations within the liquid crystal 504. In this condition, they may present a larger cross-section to light passing through the filter 500, so that the total amount of reflection or refraction may be increased. However, because the fibers 502 may be small, randomly distributed, and randomly oriented, both reflection from and refraction through the fibers 502 may result in significant scattering of the incident light. Thus, in its hot state the filter 500 may act as an optical diffuser. The composition and design of liquid crystal materials and their alignment layers are well known and need no further elaboration here.
In a slightly different exemplary form of this embodiment, the fibers, flakes, or bubbles 502 may be buoyant, or attached to objects which are buoyant, such that their buoyancy may change with temperature and such that below a threshold temperature they either rise to the top or sink to the bottom of their enclosure and are no longer able to scatter the light passing through said enclosure. A so-called “Galileo thermometer” exhibits such buoyancy effects. Such a device may be configured to act as a thermodiffusive filter for reflective building and vehicle surfaces.
Alternatively, a thermally activated polarizer may be employed for this function. U.S. Pat. No. 6,965,420 to Li et al. describes a narrowband, circular polarizer made from cholesteric liquid crystals (CLCs) that switches to broadband operation when its structure is disrupted by an AC electric field. Such polarizers are capable of diffusive reflection or transmission of certain polarities of light. However, in the present application the polarizer may be switched from narrowband to broadband operation through temperature change, i.e., because of a phase transition in the CLC. The polarizer contains domains or bubbles of liquid crystal in a polymer matrix, and a disorganization of this structure can be achieved, for example, by a transition of the entrapped liquid crystal to an isotropic state above a given threshold temperature, defined by the exact structure and composition of the liquid crystal mixture.
In one exemplary form of this embodiment, a narrowband polarizer with a response in the near infrared is employed, such that its polarizing and possible diffusing effects are not visible to the human eye. However, when the temperature increases beyond a threshold value, the organization of the liquid crystal domains is disrupted, the bandwidth of the polarizer increases to cover some or all of the visible spectrum, and the polarizing and possible diffusing effects become visible. In this hot state, the thermally activated polarizer may serve as a visible light diffuser and may thus be used to mitigate glare as described above. In a further elaboration of this embodiment, a second thermally activated polarizer of opposite circular polarization may be added to enhance the diffusion and attenuation effects.
In still another exemplary form of this embodiment, the variable diffuser is a thermoreflective filter as described in
Myriad other arrangements are possible which have the same effect of scattering small reflective or refractive objects 502 in the line of sight at high temperatures such that they have a diffusive effect. Either removing the objects 502 or reducing their cross-section at low temperatures such may eliminate or reduces their diffusive effects. A wide variety of configurations may meet this description and function as temperature-dependent, variable diffusers, and thus fit the embodiment shown in
However, when irregular wires 604 are used instead, the “surface” of the polarizer (as seen by photons of the appropriate wavelength and polarity) may appear irregular rather than smooth. Since specular reflection may require a microscopically smooth surface, while reflection from irregular surfaces may be diffusive, the reflected light from such a polarizer may have a white or metallic gray appearance, rather than a mirrored one. This effect may be most pronounced when the surface irregularities are larger than the wavelengths of the light being reflected, but too small to be perceived directly by the human eye. Thus, a wire grid polarizer fashioned from irregular wires 604 may act as a selective diffuser which transmits collimated light (i.e., clear images) of one linear polarity while diffusively reflecting light of the orthogonal linear polarity.
The addition of microscopic breaks or gaps 606 within the smooth wires 602 or irregular wires 604 may tend to have a refracting effect for the polarity of light that is transmitted through, and if the size and distribution of these gaps 606 is random or pseudo-random, then this refraction may be diffusive as well.
This implementation of the technology may exploit either or both of these effects to reduce the glare from thermoreflective surfaces, by constructing the thermoreflective filters from diffusive rather than specular wire grid polarizers. For example, a thermoreflective architectural window incorporating such a filter may transmit collimated light from the outside to the inside, allowing a clear view of the outside to building occupants. However, the reflection (aside from ordinary glass reflection caused by the refractive index mismatch between glass and air) from such a window may be diffusive rather than specular. Thus, the building may be able to reap the energy benefits of a thermoreflective window without producing the specular reflection that may lead to glare.
In addition, such a polarizer may be used by itself as a window film or filter, presenting a surface with approximately 50% diffusive reflection and 50% collimated transmission. Thus, the building may be able to reap the energy benefits of a reflective window without the glare effects caused by specular reflection. For the same reasons, such a polarizer could serve as an anti-glare film for a reflective wall or skin or body panels in vehicles or buildings.
In addition, for wavelengths of light dependent on the size and spacing of the wires as described in Fedotov et al., this structure may have the additional property of being asymmetric in its polarizing effects. That is, light coming through from one orthogonal direction (i.e., from outside the page, traveling in) may be more strongly polarized than light coming through from the opposite orthogonal direction (i.e., from inside the page, traveling out). A linear structure may be geometrically equivalent when viewed from either side. However, a chiral structure may not be the same, i.e., the chirality of the structure when viewed from the back may be opposite to the chirality of the same structure when viewed from the front. This is the origin of the polarization asymmetry, such that the degree of polarization asymmetry, like the degree of circularity, may be proportional to the degree of chirality. One hundred percent asymmetry may require infinite chirality, i.e., a structure that likely cannot be physically realized. However, very high degrees of asymmetry have been achieved with manufacturable nanostructures.
When the wires 802 of this metamaterial wire grid polarizer 800 are fashioned to be irregular or are fashioned on an irregular surface such that the light reflected by them may be scattered and thus the polarizer may act as a diffusively reflective circular polarizer, the diffusive reflection effects may combine with the asymmetric polarization effects in an entirely novel way that would unlikely be achievable with classical optics. For non-prepolarized light, i.e., light of mixed random polarity (as with sunlight or artificial light that has not been reflected), the structure may be more diffusive to light passing through it in one direction than to light passing through in the opposite direction. In the extreme case, where the chirality is large, the result is a “one-way diffuser” that may transmit clear, collimated images in one direction with a theoretical transmissivity well in excess of 50% and that may reflect diffuse light in the opposite direction with a theoretical reflectivity approaching 50%.
In one exemplary application of this technology, this one-way diffuser may be laminated to windows as a privacy filter. Existing privacy filters may employ classical diffusive optics that are symmetrically diffusive, i.e., they may obscure the view from the inside looking out just as much as they obscure the view from the outside looking in. By contrast, the one-way diffuser may be oriented such that it may provides a clear view from the inside looking out, and a highly diffusive view from the outside looking in. In addition, this filter may have all the solar heat gain reduction and glare reduction advantages already cited for diffusively reflective polarizing filters. Thus, it may provide a uniquely powerful solution to several different window problems at the same time.
In another exemplary application, the one-way diffuser may be employed in conjunction with a reflective or thermoreflective building surface for glare reduction, i.e., to diffuse the light reflected from this surface without significantly diffusing the light, if any, passing through the surface. In still another exemplary application, a thermoreflective filter of the sort depicted in
In still another exemplary application, the chiral wire grid polarizer (whether specular or diffusive) may be employed in a structure closely resembling the thermoreflective filter depicted in
Many optional enhancements may be made to this chiral metamaterial polarizer 800 without altering its fundamental nature. For example, the chiral wire structures 802 may be formed on the substrate such that they are not completely parallel, or such that the “fish scales” are not all identical in size and orientation. Alternatively, or in addition, the wires 802 may not be continuous, but may instead be composed of multiple segments, each exhibiting one or more of the chiral “fish scale” structures. These segments may generally be longer than ¼ of the wavelength of light they are intended to interact with, while less pronounced effects may be observed with smaller wire segments. Multiple layers of chiral polarizer, with identical or nonidentical properties, may be stacked to enhance their effects or broaden the range of wavelengths or polarities over which they respond.
The exact optical properties of the chiral wire grid polarizer may be tuned by varying the width, height, spacing, and surface roughness of the wires; the spacing, diameter, chirality, and staggering or tesselation of the fish scale structures along the wires 802, and the degree of rippling, warping, or roughness of the underlying substrate. In addition, the optical properties of the chiral polarizer may be strongly affected by the choice of metal from which the wires are made.
In addition, although the roughened, chiral wire grid structure has been described here for exemplary purposes, this is by no means the only structure capable of producing asymmetric polarizing effects and/or asymmetric diffusion effects. This implementation of the technology is not limited to a particular structure, but is rather a method for reducing glare from reflective surfaces using any of a variety of different structures with similar effects.
Another embodiment of a thermotropic DBR may use polymer layers similar in formulation, for example, to 3M DBEF polarizer, which expand thermally and thus exhibit a different spatial frequency and respond to different wavelengths of light. However, in embodiments of
By using multiple layers of materials with different temperature responses, in theory any or all of the properties of the reflector may be affected. A thermotropic DBR may thus additionally be designed as a “disappearing” polarizer, such that the polarization effect appears or disappears as the temperature rises or falls. The thermotropic DBR may also be designed to have other effects, for example, a variable center frequency polarizer, a variable bandwidth polarizer, or a variable efficiency polarizer, or as a hybrid thermochromic DBR (TDBR) and thermochromic polarizer.
Both a thermochromic polarizer and TDBR may be used, among other things, to reduce the amount of glare in optical devices (for example, in a thermoreflective filter as disclosed in U.S. patent application Ser. No. 12/172,156), by configuring the devices to not switch completely “on” at one temperature, thereby reducing glare at “intermediate temperatures” temperatures. Alternatively, the thermochromic polarizer and TDBR may increase or decrease the reflected bandwidth by such devices to reduce glare; adjust a center bandwidth by temperature to reduce glare; operate in frequencies where optical glare does not occur such as IR and UV light; or configure a device which reflects similar amounts of visible light at low and high temperatures, but reflects less or more UV and IR at these temperatures. Since the TDBR may be either specular or diffusive, a thermochromic polarizer using a Bragg reflector may similarly be either specular or diffusive. Additionally, electrochromic “overrides” of the thermochromic embodiments may be employed such as, for example, a distributed Bragg reflector in which electric signals may additionally change the behavior of the device at one or more temperatures.
It may be possible to choose both the sizes of the liquid crystal molecules used in such TDBRs and polarizing TDBR (PTDBRs) in particular configurations such that their action is primarily or wholly in the NIR and IR. This selection may reduce glare by reducing the amount of visible light reflected. The devices may also be designed such that the amount of light reflected in the visible spectrum is below a design limit in the various active temperature ranges. These exemplary devices, including in diffusive, specular, and hybrid embodiments, along with electrochromic “override” versions, are all considered implementations of the invention and are merely exemplary and not exhaustive.
Note that IR TDBR and IR PTDBR devices may redshift the light passing through at off-normal angles, which theoretically means that devices designed for glare reduction by utilizing only NIR or longer visible wavelengths such as red should have less visible light glare at “off-angles” than at normal, which may be desirable in a glare management device.
TDBR and PTDBR devices may be innately diffusive, or can alternatively be put behind a diffuser that operates at one or more frequencies. In one exemplary embodiment, a diffusive, glare-reducing version of a PTDBR uses PDLC technology with a vertical mode device, a high pre-tilt alignment layer (an exemplary device might have a pre-tilt angle above 75 degrees), and a positive mode, where the index of refraction may be matched at low temperatures and where the index transitions from a nematic to isotropic phase change. This may result in a TDBR when the device is at a high temperature, which disappears when at a lower temperature below the clearing point. Similar effects on polarization may be effected using these methods.
PSCT, PDLC, and Guest Host versions of both TDBR and PTDBR devices are possible, as well as hybrid devices. Guest Host embodiments using absorptive or reflective dyes may be aligned such that they do not reflect or absorb until a phase transition occurs or a set-point temperature is reached. These embodiments may reduce glare by choosing which frequencies to reflect in bands, including IR. Guest Host embodiments may be particularly suitable for PTDBR devices. Another embodiment may use diffusive versions of TDBR and PTDBR devices at IR wavelengths in combination with specular versions at visible wavelengths to increase the efficiency while allowing choice of visible reflectivity for aesthetic reasons. Hybrid TDBR and PTDBR devices are also embodiments of this device. This list of embodiments is merely exemplary and devices made from all suitable materials (metal, solids, gases, liquids, liquid crystals, dichroics, photonic crystals, and other materials) are contemplated.
There are many desirable qualities in a thermochromic or thermoreflective liquid crystal filters and devices for use in windows and building materials that can be achieved through mixtures of liquid crystals and mixtures including liquid crystals. These may include designing the freezing and clearing points of the mixture to make them suitable for a particular climate or for controlling the temperature range of the hot and cold state or the entrance and exit of heat through the device. Additionally, these may include mixtures designed to affect the speed, optical clarity, and/or light absorption, reflection, or transmission properties between the hot and cold states or other physical states (e.g. the transition between crystalline and nematic states), as well as mixtures designed to improve the stability of the functional responses of the device (such as optical properties, freezing or clearing points, or transition speed) to environmental conditions (e.g., exposure to UV or other light, humidity, gases, thermal cycling, or temperature extremes). The construction details of these embodiments may be variable while adhering to the spirit of a method for reducing glare from reflective or thermoreflective surfaces.
Once the incoming light passes through the outer reflective polarizing filter 1201, the incoming light then enters an absorptive polarizer 1203 with a polarization vector which may be matched to that of the reflective polarizer 1201. Because the light passing through this absorptive polarizer 1203 has been prepolarized by the reflective polarizer 1201, its polarity matches that of the absorptive polarizer 1203 and thus very little of the light may be absorbed, and a large majority of it may be transmitted through.
Next, the transmitted light encounters a thermotropic depolarizer 1202, which is a device or material capable of exhibiting two different polarizing states. In its hot or isotropic or liquid state, the polarized light passing through the thermotropic depolarizer 1202 may not be affected. In its cold (e.g., nematic or crystalline) state, the thermotropic depolarizer 1202 may rotate the polarization vector of the incoming light by a fixed amount.
Once it has passed through the thermotropic depolarizer 1202, the remaining polarized light strikes an inner reflective polarizer 1201′, also known as the “analyzer,” where it may be either reflected or transmitted, depending on its polarization state. The inner reflective polarizer 1201′ may be oriented such that its polarization is perpendicular to that of the outer reflective polarizer 1201. Thus, in a hot state, when the polarization vector of the light has not been rotated, the polarity of the light is perpendicular to that of the inner reflective polarizer 1201′ and a majority of the light (in theory, up to 100%) may be reflected. However, in the cold state, when the polarization vector of the light has been rotated by 90 degrees and is parallel to the inner reflective polarizer 1201′, a small amount of the light may be absorbed by the polarizer material and the rest may be transmitted through. Finally, the light encounters an inner absorptive polarizer 1203′ of matched polarity and is transmitted through.
Thus, for exterior light passing through into the interior of a building, vehicle, or other structure, the behavior, performance, and appearance of this embodiment may be extremely similar to those of the device described in
When unpolarized light from an interior source strikes the device 1200, it encounters the inner absorptive polarizer 1203′. Of the incoming light, approximately 50% will have polarization perpendicular to that of the inner absorptive polarizer 1203′ and will be absorbed. The remaining light will have matching polarization and will be transmitted through.
Once it has passed through the inner absorptive polarizing filter 1203′, the incoming light then enters the inner reflective polarizer 1201′ with a polarization vector matched to that of the inner absorptive polarizer 1203′. Because the light passing through this inner reflective polarizer 1201′ has been prepolarized by the inner absorptive polarizer 1203′, its polarity matches that of the inner reflective polarizer 1201′ and thus very little of the light may be reflected, and a large majority of it transmitted through.
Next, the transmitted light encounters the thermotropic depolarizer 1202, such that in its hot or isotropic or liquid state, the polarized light passing through the thermotropic depolarizer 1202 may not be affected, whereas in its cold (e.g., nematic or crystalline) state, the thermotropic depolarizer 1202 may rotate the polarization vector of the incoming light by a fixed amount.
Once it has passed through the thermotropic depolarizer 1202, the remaining polarized light strikes the outer absorptive polarizer 1203, where it may be either reflected or transmitted, depending on its polarization state. The outer absorptive polarizer 1203 may be oriented such that its polarization is perpendicular to that of the inner absorptive polarizer 1203′. Thus, in the hot state, when the polarization vector of the light has not been rotated, the polarity of the light is perpendicular to that of the outer absorptive polarizer 1203 and a majority of the light (in theory, up to 100%) is absorbed. However, in the cold state, when the polarization vector of the light has been rotated (e.g., by 90 degrees) and is parallel to the outer absorptive polarizer 1203, a small amount of the light may be absorbed by the polarizer material and the rest is transmitted through. Finally, the light passes through a reflective polarizer 1201 of matched polarity and may be transmitted through.
This arrangement may allow a thermoreflective filter to reflect away radiant energy (e.g., sunlight and/or infrared solar heat) coming from outside a structure, without also presenting a mirrored surface to the inside of the structure. This may mean, for example, that unlike an ordinary mirrored or thermoreflective film which may reflect the building interior at night and thus not allow an exterior view at night, this embodiment may allow a clear (though attenuated) view of the outside, even when the light inside the building or other structure is brighter than the light outside of it. This may be desirable, for example, in residential windows where a nighttime view of the stars or city lights is generally expected. Thus, this embodiment is intended to reduce interior glare, while allowing the exterior appearance of the filter to be that of a specular mirror. However, this arrangement may be combined with any of the other glare reduction methods described above, and may also be turned around to present an absorptive appearance to the structure's exterior and a reflective appearance to the interior (which may be desirable, for example, in solar ovens or other structures designed to absorb and retain large amounts of solar heat).
Additional polarizers or other optical elements may also be added to produce different optical effects without affecting the methods for reducing glare from reflective and thermoreflective surfaces disclosed herein. In addition, the thermotropic depolarizer 1202 may optionally be deleted, resulting in a film, device or, optical stack with optical properties that may not vary with temperature. However, this film or device or stack would have the interesting property of being reflective in one direction and absorptive in the other, and thus function as an alternate structure for reducing glare from reflective surfaces
While several exemplary embodiments are depicted and described herein, it should be understood that the present invention is not limited to these particular configurations. Optional components such as coatings, films, spacers, fillers, or support structures may be added to suit the needs of a particular application or a particular manufacturing method, and degraded forms of some embodiments can be produced by deleting or substituting certain components. For example, the wires of a wire grid polarizer could be fashioned from imperfect conductors or semiconductors, or from materials (e.g., copper) whose reflection spectra include substantial color anomalies.
The exact arrangement of the various layers can be different than is depicted here and, depending on the materials and wavelengths selected, different layers can be combined as single layers, objects, devices, or materials, without altering the essential structure and function of the invention. For example, the wire segments in the thermodiffusive filter of
Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but rather construed as merely providing illustrations of certain exemplary embodiments of this invention. There are various possibilities for making the implementation of different materials and in different configurations.
Although various embodiments of this invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. All directional references e.g., proximal, distal, upper, lower, inner, outer, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, left circular, and right circular are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Connection references, e.g., attached, coupled, connected, and joined are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily imply that two elements are directly connected and in fixed relation to each other. Percentages of reflection, transmission or absorption are illustrative and shall not be limiting. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the following claims.
This application claims priority pursuant to 35 U.S.C. §119(e) to the following: U.S. provisional patent application No. 61/047,400 entitled “Glare management method for reflective and thermoreflective surfaces” filed 23 Apr. 2008; U.S. provisional patent application No. 61/083,138 entitled “Glare management method for reflective and thermoreflective surfaces” filed 23 Jul. 2008; U.S. provisional patent application No. 61/084,940 entitled “Glare management method for reflective and thermoreflective surfaces” filed 30 Jul. 2008; U.S. provisional patent application No. 61/146,207 entitled “Glare management method for reflective and thermoreflective surfaces” filed 21 Jan. 2009; and U.S. provisional patent application No. 61/157,076 entitled “Glare management method for reflective and thermoreflective surfaces” filed 3 Mar. 2009, the disclosures of which are hereby incorporated herein by reference in their entirety. This application is also related to U.S. patent application Ser. No. 12/019,602 entitled “Thermally switched optical downconverting filter” filed 24 Jan. 2008; U.S. patent application Ser. No. 12/172,156 entitled “Thermally switched reflective optical shutter” filed 14 Jul. 2008; and U.S. patent application Ser. No. 12/340,552 entitled “Thermally switched absorptive window shutter” filed 19 Dec. 2008, the disclosures of which are hereby incorporated herein by reference in their entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3990784 | Gelber | Nov 1976 | A |
| 4006730 | Clapham et al. | Feb 1977 | A |
| 4155895 | Rohowetz et al. | May 1979 | A |
| 4268126 | Mumford | May 1981 | A |
| 4456335 | Mumford | Jun 1984 | A |
| 4475031 | Mockovciak, Jr. | Oct 1984 | A |
| 4491390 | Tong-Shen | Jan 1985 | A |
| 4512638 | Sriram et al. | Apr 1985 | A |
| 4579638 | Scherber | Apr 1986 | A |
| 4640583 | Hoshikawa et al. | Feb 1987 | A |
| 4641922 | Jacob | Feb 1987 | A |
| 4688900 | Doane et al. | Aug 1987 | A |
| 4688901 | Albert | Aug 1987 | A |
| 4755673 | Pollack et al. | Jul 1988 | A |
| 4756758 | Lent et al. | Jul 1988 | A |
| 4783150 | Tabony | Nov 1988 | A |
| 4789500 | Morimoto et al. | Dec 1988 | A |
| 4804254 | Doll et al. | Feb 1989 | A |
| 4848875 | Baughman et al. | Jul 1989 | A |
| 4859994 | Zola | Aug 1989 | A |
| 4871220 | Kohin | Oct 1989 | A |
| 4877675 | Falicoff et al. | Oct 1989 | A |
| 4893902 | Baughman et al. | Jan 1990 | A |
| 4899503 | Baughman et al. | Feb 1990 | A |
| 4964251 | Baughman et al. | Oct 1990 | A |
| 5009044 | Baughman et al. | Apr 1991 | A |
| 5013918 | Choi | May 1991 | A |
| 5025602 | Baughman et al. | Jun 1991 | A |
| 5111629 | Baughman et al. | May 1992 | A |
| 5132147 | Takiguchi | Jul 1992 | A |
| 5152111 | Baughman et al. | Oct 1992 | A |
| 5193900 | Yano et al. | Mar 1993 | A |
| 5196705 | Ryan | Mar 1993 | A |
| 5197242 | Baughman et al. | Mar 1993 | A |
| 5212584 | Chung | May 1993 | A |
| 5227115 | Harnischfeger | Jul 1993 | A |
| 5274246 | Hopkins | Dec 1993 | A |
| 5304323 | Arai et al. | Apr 1994 | A |
| 5308706 | Kawaguchi et al. | May 1994 | A |
| 5319478 | Funfschilling et al. | Jun 1994 | A |
| 5347140 | Hirai | Sep 1994 | A |
| 5377042 | Chahroudi | Dec 1994 | A |
| 5481400 | Borden | Jan 1996 | A |
| 5525430 | Chahroudi | Jun 1996 | A |
| 5530263 | DiVincenzo | Jun 1996 | A |
| 5574286 | Huston et al. | Nov 1996 | A |
| 5585640 | Huston | Dec 1996 | A |
| 5757828 | Ouchi | May 1998 | A |
| 5763307 | Wang | Jun 1998 | A |
| 5881200 | Burt | Mar 1999 | A |
| 5889288 | Futatsugi | Mar 1999 | A |
| 5897957 | Goodman | Apr 1999 | A |
| 5937295 | Chen | Aug 1999 | A |
| 5940150 | Faris et al. | Aug 1999 | A |
| 6040859 | Takahashi | Mar 2000 | A |
| 6099758 | Verrall et al. | Aug 2000 | A |
| 6122103 | Perkins et al. | Sep 2000 | A |
| 6208463 | Hansen | Mar 2001 | B1 |
| 6218018 | McKown et al. | Apr 2001 | B1 |
| 6226067 | Nishiguchi et al. | May 2001 | B1 |
| 6240114 | Anselm | May 2001 | B1 |
| 6260414 | Brown et al. | Jul 2001 | B1 |
| 6281519 | Sugiyama et al. | Aug 2001 | B1 |
| 6288840 | Perkins et al. | Sep 2001 | B1 |
| 6294794 | Yoshimura et al. | Sep 2001 | B1 |
| 6304784 | Allee | Oct 2001 | B1 |
| 6320220 | Watanabe | Nov 2001 | B1 |
| 6329668 | Razeghi | Dec 2001 | B1 |
| 6333516 | Katoh | Dec 2001 | B1 |
| 6381068 | Harada et al. | Apr 2002 | B1 |
| 6437361 | Matsuda | Aug 2002 | B1 |
| 6446402 | Byker et al. | Sep 2002 | B1 |
| 6486997 | Bruzzone et al. | Nov 2002 | B1 |
| 6487112 | Wasshuber | Nov 2002 | B1 |
| 6493482 | Al-hemyari et al. | Dec 2002 | B1 |
| 6498354 | Jefferson | Dec 2002 | B1 |
| 6504588 | Kaneko | Jan 2003 | B1 |
| 6512242 | Fan et al. | Jan 2003 | B1 |
| 6559903 | Faris et al. | May 2003 | B2 |
| 6583827 | Faris et al. | Jun 2003 | B2 |
| 6600169 | Stintz | Jul 2003 | B2 |
| 6611640 | LoCasclo | Aug 2003 | B2 |
| 6635898 | Williams et al. | Oct 2003 | B2 |
| 6661022 | Morie | Dec 2003 | B2 |
| 6671008 | Li et al. | Dec 2003 | B1 |
| 6710823 | Faris et al. | Mar 2004 | B2 |
| 6718086 | Ford | Apr 2004 | B1 |
| 6730909 | Butler | May 2004 | B2 |
| 6753273 | Holonyak, Jr. et al. | Jun 2004 | B2 |
| 6770916 | Ohshima | Aug 2004 | B2 |
| 6777718 | Takagi | Aug 2004 | B2 |
| 6816525 | Stintz et al. | Nov 2004 | B2 |
| 6847662 | Bouda et al. | Jan 2005 | B2 |
| 6859114 | Eleftheriades | Feb 2005 | B2 |
| 6912018 | Faris et al. | Jun 2005 | B2 |
| 6926952 | Weber et al. | Aug 2005 | B1 |
| 6933812 | Sarabandi | Aug 2005 | B2 |
| 6946697 | Pietambaram | Sep 2005 | B2 |
| 6963435 | Mallya et al. | Nov 2005 | B2 |
| 6965420 | Li et al. | Nov 2005 | B2 |
| 6978070 | McCarthy et al. | Dec 2005 | B1 |
| 6985291 | Watson et al. | Jan 2006 | B2 |
| 6992822 | Ma et al. | Jan 2006 | B2 |
| 7026641 | Mohseni | Apr 2006 | B2 |
| 7038745 | Weber et al. | May 2006 | B2 |
| 7042615 | Richardson | May 2006 | B2 |
| 7046441 | Huang | May 2006 | B2 |
| 7068234 | Sievenpiper | Jun 2006 | B2 |
| 7099062 | Azens et al. | Aug 2006 | B2 |
| 7113335 | Sales | Sep 2006 | B2 |
| 7154451 | Sievenpiper | Dec 2006 | B1 |
| 7161737 | Umeya | Jan 2007 | B2 |
| 7166797 | Dziendziel et al. | Jan 2007 | B1 |
| 7221827 | Domash et al. | May 2007 | B2 |
| 7245431 | Watson et al. | Jul 2007 | B2 |
| 7276432 | McCarthy et al. | Oct 2007 | B2 |
| 7300167 | Fernando et al. | Nov 2007 | B2 |
| 7318651 | Chua | Jan 2008 | B2 |
| 7351346 | Little | Apr 2008 | B2 |
| 7385659 | Kotchick et al. | Jun 2008 | B2 |
| 7470925 | Tamura | Dec 2008 | B2 |
| 7522124 | Smith | Apr 2009 | B2 |
| 7532397 | Tanaka | May 2009 | B2 |
| 7538946 | Smith | May 2009 | B2 |
| 7561332 | Little et al. | Jul 2009 | B2 |
| 7601946 | Powers | Oct 2009 | B2 |
| 7619816 | Deng | Nov 2009 | B2 |
| 7655942 | McCarthy et al. | Feb 2010 | B2 |
| 7692180 | Snyder | Apr 2010 | B2 |
| 7755829 | Powers et al. | Jul 2010 | B2 |
| 7768693 | McCarthy et al. | Aug 2010 | B2 |
| 7911563 | Hung | Mar 2011 | B2 |
| 7936500 | Powers | May 2011 | B2 |
| 7977621 | McCarthy | Jul 2011 | B2 |
| 8072672 | Powers et al. | Dec 2011 | B2 |
| 8076661 | McCarthy et al. | Dec 2011 | B2 |
| 8169685 | Powers | May 2012 | B2 |
| 8271241 | Akyurtlu | Sep 2012 | B2 |
| 8284336 | Powers | Oct 2012 | B2 |
| 20020079485 | Stintz et al. | Jun 2002 | A1 |
| 20020085151 | Faris et al. | Jul 2002 | A1 |
| 20020114367 | Stintz et al. | Aug 2002 | A1 |
| 20020118328 | Faris et al. | Aug 2002 | A1 |
| 20020141029 | Carlson et al. | Oct 2002 | A1 |
| 20020152191 | Hollenberg | Oct 2002 | A1 |
| 20020180916 | Schadt et al. | Dec 2002 | A1 |
| 20020190249 | Williams | Dec 2002 | A1 |
| 20030052317 | Ohshima | Mar 2003 | A1 |
| 20030059998 | Holonyak, Jr. | Mar 2003 | A1 |
| 20030066998 | Lee | Apr 2003 | A1 |
| 20030107813 | Clabburn et al. | Jun 2003 | A1 |
| 20030107927 | Yerushalmi | Jun 2003 | A1 |
| 20030129247 | Ju et al. | Jul 2003 | A1 |
| 20030138209 | Chan | Jul 2003 | A1 |
| 20030218712 | Kumar et al. | Nov 2003 | A1 |
| 20030227663 | Agrawal | Dec 2003 | A1 |
| 20040005451 | Kretman et al. | Jan 2004 | A1 |
| 20040012749 | Freeman | Jan 2004 | A1 |
| 20040036993 | Tin | Feb 2004 | A1 |
| 20040256612 | Mohseni | Dec 2004 | A1 |
| 20050068629 | Fernando et al. | Mar 2005 | A1 |
| 20050157996 | McCarthy | Jul 2005 | A1 |
| 20050157997 | McCarthy | Jul 2005 | A1 |
| 20050185125 | Miyachi et al. | Aug 2005 | A1 |
| 20050221128 | Kochergin | Oct 2005 | A1 |
| 20050271092 | Ledentsov | Dec 2005 | A1 |
| 20060011904 | Snyder et al. | Jan 2006 | A1 |
| 20060049394 | Snyder et al. | Mar 2006 | A1 |
| 20060147810 | Koch | Jul 2006 | A1 |
| 20060151775 | Hollenberg | Jul 2006 | A1 |
| 20060238867 | Takeda et al. | Oct 2006 | A1 |
| 20060257090 | Podolskiy et al. | Nov 2006 | A1 |
| 20060262398 | Sangu et al. | Nov 2006 | A1 |
| 20060274218 | Xue | Dec 2006 | A1 |
| 20070070276 | Tan et al. | Mar 2007 | A1 |
| 20070121034 | Ourderkirk et al. | May 2007 | A1 |
| 20070215843 | Soukoulis et al. | Sep 2007 | A1 |
| 20070279727 | Ghandi et al. | Dec 2007 | A1 |
| 20080013174 | Allen et al. | Jan 2008 | A1 |
| 20080061222 | Powers et al. | Mar 2008 | A1 |
| 20080117500 | Narendran et al. | May 2008 | A1 |
| 20080138543 | Hoshino et al. | Jun 2008 | A1 |
| 20080160321 | Padiyath et al. | Jul 2008 | A1 |
| 20080204383 | McCarthy et al. | Aug 2008 | A1 |
| 20080210893 | McCarthy et al. | Sep 2008 | A1 |
| 20080246388 | Cheon | Oct 2008 | A1 |
| 20080259254 | Kikuchi et al. | Oct 2008 | A1 |
| 20090015902 | Powers et al. | Jan 2009 | A1 |
| 20090040132 | Sridhar | Feb 2009 | A1 |
| 20090059406 | Powers et al. | Mar 2009 | A1 |
| 20090128893 | McCarthy et al. | May 2009 | A1 |
| 20090128907 | Takahashi et al. | May 2009 | A1 |
| 20090167971 | Powers et al. | Jul 2009 | A1 |
| 20090219603 | Xue | Sep 2009 | A1 |
| 20090268273 | Powers et al. | Oct 2009 | A1 |
| 20090296190 | Anderson et al. | Dec 2009 | A1 |
| 20100001008 | McCarthy et al. | Jan 2010 | A1 |
| 20100015363 | Chiang et al. | Jan 2010 | A1 |
| 20100027099 | McCarthy et al. | Feb 2010 | A1 |
| 20100045924 | Powers et al. | Feb 2010 | A1 |
| 20100051898 | Kim, II | Mar 2010 | A1 |
| 20100060844 | Sawatari et al. | Mar 2010 | A1 |
| 20100118380 | Xue | May 2010 | A1 |
| 20100232017 | McCarthy et al. | Sep 2010 | A1 |
| 20100259698 | Powers et al. | Oct 2010 | A1 |
| 20100271686 | Powers et al. | Oct 2010 | A1 |
| 20100288947 | McCarthy et al. | Nov 2010 | A1 |
| 20110025934 | McCarthy et al. | Feb 2011 | A1 |
| 20110044061 | Santoro et al. | Feb 2011 | A1 |
| 20110102878 | McCarthy et al. | May 2011 | A1 |
| 20110205650 | Powers et al. | Aug 2011 | A1 |
| 20110216254 | McCarthy et al. | Sep 2011 | A1 |
| 20110234944 | Powers et al. | Sep 2011 | A1 |
| 20110292488 | McCarthy | Dec 2011 | A1 |
| 20120140311 | Powers et al. | Jun 2012 | A1 |
| 20120262773 | Powers et al. | Oct 2012 | A1 |
| 20130033738 | Powers et al. | Feb 2013 | A1 |
| Number | Date | Country |
|---|---|---|
| 2620005 | Jul 2008 | CA |
| 1189224 | Jul 1998 | CN |
| 1350648 | May 2002 | CN |
| 1494091 | May 2004 | CN |
| 1162496 | Dec 2001 | EP |
| 2261989 | Jun 1993 | GB |
| 58-10717 | Jan 1983 | JP |
| 58010717 | Jan 1983 | JP |
| 61223719 | Oct 1986 | JP |
| 01178517 | Jul 1989 | JP |
| 02-089426 | Mar 1990 | JP |
| 06-158956 | Jun 1994 | JP |
| 08-015663 | Jan 1996 | JP |
| 10-287449 | Oct 1998 | JP |
| 10-311189 | Nov 1998 | JP |
| 2002-357815 | Dec 2002 | JP |
| 2003-248204 | Sep 2003 | JP |
| 2004-004795 | Jan 2004 | JP |
| 2005-250119 | Sep 2005 | JP |
| 2006-243485 | Sep 2006 | JP |
| 2007-515661 | Jun 2007 | JP |
| 2007-272016 | Oct 2007 | JP |
| 2008-530766 | Aug 2008 | JP |
| 10-2002-0044153 | Feb 2003 | KR |
| 10-2004-0108816 | Dec 2004 | KR |
| 10-2003-0072578 | Apr 2005 | KR |
| 10-2006-0000059 | Jan 2006 | KR |
| 10-2007-0091314 | Sep 2007 | KR |
| 10-2010-0039401 | Apr 2010 | KR |
| 9402313 | Feb 1994 | WO |
| 9701789 | Jan 1997 | WO |
| 0123173 | Apr 2001 | WO |
| 02064937 | Aug 2002 | WO |
| 03029885 | Apr 2003 | WO |
| 03096105 | Nov 2003 | WO |
| 2005031437 | Apr 2005 | WO |
| 2006023195 | Mar 2006 | WO |
| 2006088369 | Aug 2006 | WO |
| 2008092038 | Jul 2008 | WO |
| 2008144217 | Nov 2008 | WO |
| Entry |
|---|
| Author Unknown, “Liquid Crystal Research,” http://chirality.swarthmore.edu, printed Aug. 21, 2009. |
| Barbagallo, S., et al., “Synthesis of novel metamaterials,” Chapter 2 (VDM Verlag 2008). |
| Eleftheriades, G.V., et al. (Editors); Iyers, “Negative-Refraction Metamaterials,” Chapter 1 (Wiley 2005), pp. 4-5, 16-30, 321-330. |
| Padilla, W.J., et al., “Electrically resonant terahertz metamaterials: Theoretical and experimental investigations,” Physical Review B 75, 041102(R) (2007). |
| Rogacheva, A.V., et al., “Giant gyrotropy due to electromagnetic-field coupling in a bilayered chiral structure,” Physical Review Letters 97, 177401 (Oct. 27, 2006). |
| Sarychev, et al., “Negative refraction metamaterials,” Chapter 8 (Wiley 2005). |
| Zhang, W., Giant optical activity in dielectric planar metamaterials with two-dimensional chirality, Journal of Optics A: Pure and Applied Optics, 8, pp. 878-890 (2006). |
| Notice of Allowance, U.S. Appl. No. 12/019,602, dated Jun. 9, 2010. |
| Fedotov, V. A., et al., “Asymmetric Propagation of Electromagnetic Waves through a Planar Chiral Structure,” The American Physical Society, PRL 97, Oct. 20, 2006, pp. 167401-1-167401-4. |
| Ginley, D. S., et al., “Transparent Conducting Oxides,” MRS Bulletin, Aug. 2000, pp. 15-18. |
| Goldhaber-Gordon, David, et al., “Overview of Nanoelectronic Devices,” Proceedings of the IEEE, vol. 85, No. 4 (Apr. 1997), pp. 521-533. |
| Harrison, “Quantum Wells, Wires, and Dots: Theoretical & Computational Physics of Semiconductor Nanostructures” 2nd Edition, John Wiley & Sons, Ltd (2005), 3 pages. |
| Lan, S., et al., “Survey on Roller-type Nanoimprint Lithography (RNIL) Process,” International Conference on Smart Manufacturing Application, Apr. 9-11, 2008, in KINTEX, Gyeonggi-do, Korea, pp. 371-376. |
| Leatherdale, C.A., et al., “Photoconductivity in CdSe Quantum Dot Solids,” Physical Review B, vol. 62, No. 4 (Jul. 15, 2000), pp. 2669-2680. |
| Manea, E., et al., “Optical Characterization of SnO2 thin Films Prepared by Sol Gel Method, for ‘Honeycomb’ Textured Silicon Solar Cells,” International Semiconductor Conference, 2006, vol. 1, Issue, Sep. 2006, pp. 179-182. |
| Manea, E., et al., “SnO2 Thin Films Prepared by Sol Gel Method for ‘Honeycomb’ Textured Silicon Solar Cells,” Romanian Journal of Information Science and Technology, vol. 10, No. 1, 2007, pp. 25-33. |
| Siegel, J. D., “The MSVD Low E ‘Premium Performance’ Myth,” International Glass Review, Issue 1, 2002, pp. 55-58. |
| Korean Intellectual Property Office as International Searching Authority, International Search Report and Written Opinon for International Application No. PCT/US2008/051959, Jun. 3, 2008, 10 pages. |
| Korean Intellectual Property Office as International Searching Authority, International Search Report and Written Opinion for International Application No. PCT/US2008/069881, Sep. 30, 2008, 10 pages. |
| Korean Intellectual Property Office as International Searching Authority, International Search Report and Written Opinion for International Application No. PCT/US2008/087964, Mar. 31, 2009, 10 pages. |
| Korean Intellectual Property Office as International Searching Authority, International Search Report and Written Opinion for International Application No. PCT/US2009/041576, Nov. 25, 2009, 4 pages. |
| Application as Filed, U.S. Appl. No. 13/150,475, filed Jun. 1, 2011, 31 pp. |
| Application as Filed, U.S. Appl. No. 13/100,000, filed May 3, 2011, 33 pp. |
| Application as Filed, U.S. Appl. No. 13/107,626, filed May 13, 2011, 56 pp. |
| Notice of Allowance mailed Aug. 22, 2011, U.S. Appl. No. 12/830,068, filed Jul. 2, 2010, 7 pp. |
| Notice of Allowance, mailed Jul. 22, 2011, U.S. Appl. No. 12/843,218, filed Jul. 26, 2010, 8 pp. |
| Hao, J. et al., “Manipulating Electromagnetic Wave Polarizations by Anisotropic Metamaterials”, Physical Review Letters, 2007, vol. 99, No. 063908, 4 pp. |
| Sarychev, et al., “Negative refraction metamaterials,”, Chapter 8 (Wiley 2005), 313-337. |
| Sung, J. et al., “Dynamics of photochemical phase transition of guest/host liquid crystals with an Azobenzene derivative as a photoresponsive chromophore”, Chemistry of Materials, vol. 14, No. 1, 2002, 385-391. |
| West, J. L. et al., “Characterization of polymer dispersed liquid-crystal shutters by ultraviolet/visible and infrared absorption spectroscopy”, Journal of Applied Physics, vol. 70, No. 7, Oct. 1991, 3785-3790. |
| U.S. Appl. No. 12/903,856, filed Oct. 13, 2010. |
| U.S. Appl. No. 12/916,233, filed Oct. 29, 2010. |
| U.S. Appl. No. 13/074,876, filed Mar. 29, 2011. |
| Fan, et al., “Thin-film conducting microgrids as transparent heat mirrors”, Appl. Phys. Lett., vol. 28, No. 8, Apr. 5, 1976, 440-442. |
| Yamazaki et al., “Polarisation-insensitive parametric wavelength conversion without tunable filters for converted light extraction,” Electronics Letters (Mar. 16, 2006), 42(6):365-367. |
| Extended European Search Report dated Nov. 28, 2011, EP Application No. 09734848.6, 18 pages. |
| First Office Action dated Dec. 23, 2011 (with English summary), CN Application No. 200980123601.9, 7 pages. |
| Response to First Office Action dated Jul. 7, 2012 (with English summary), CN Application No. 200980123601.9, 27 pages. |
| First Office Action dated Jan. 6, 2012 (with English comments), KR Application No. 10-2010-7026103, 7 pages. |
| Response to First Office Action dated Jul. 6, 2012 (with English summary), KR Application No. 10-2010-7026103, 37 pages. |
| U.S. Appl. No. 13/646,907, filed Oct. 8, 2012, 24 pages. |
| First Office Action dated May 10, 2011, AU Application No. 2009240500, 2 pages. |
| First Office Action dated Aug. 1, 2011, AU Application No. 2009240500, 1 page. |
| Notice of Allowance dated Aug. 26, 2011, AU Application No. 2009240500, 3 pages. |
| First Office Action dated Nov. 29, 2011, CA Application No. 2,754,619, 4 pages. |
| Response to First Office Action dated May 29, 2013, CA Application No. 2,754,619, 35 pages. |
| Second Office Action dated Nov. 28, 2012 (with English summary), CN Application No. 200980123601.9, 7 pages. |
| Response to Second Office Action dated Apr. 18, 2013 (with English summary), CN Application No. 200980123601.9, 11 pages. |
| Extended Search Report, dated Nov. 28, 2011, EP Application No. 09734848.6, 18 pages. |
| Communication pursuant to Rules 70(2) and 70(3), dated Dec. 15, 2011, EP Application No. 09734848.6, 1 page. |
| Response to Search Report, filed Jun. 19, 2012, EP Application No. 09734848.6, 10 pages. |
| Second Office Action, dated Nov. 29, 2012 (with English summary), KR Application No. 10-2010-7026103, 4 pages. |
| Response to Second Office Action, dated 29 Mar. 29, 2013 (with English summary), KR Application No. 10-2010-7026103, 17 pages. |
| Notice of Allowance, dated Jun. 3, 2013 (with English summary), KR Application No. 10-2010-7026103, 3 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20090268273 A1 | Oct 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61047400 | Apr 2008 | US | |
| 61083138 | Jul 2008 | US | |
| 61084940 | Jul 2008 | US | |
| 61146207 | Jan 2009 | US | |
| 61157076 | Mar 2009 | US |
