Thermally switched optical filter incorporating a refractive optical structure
First Claim
1. A thermoreflective or thermoabsorptive filter comprisinga diffractive-type polarizer having a first index of refraction;
- a thermotropic material adjacent to the diffractive-type polarizer;
whereinthe thermotropic material is configured such that below a threshold temperature the thermotropic material has a second index of refraction that is substantially similar to the first index of refraction such that incident light is not substantially refracted at an interface between the diffractive-type polarizer and the thermotropic material and thus the filter is largely transparent; and
the thermotropic material is configured such that above the threshold temperature the thermotropic material has a third index of refraction that is substantially different from the first index of refraction such that incident light is substantially refracted at the interface between the diffractive-type polarizer and the thermotropic material and thus the filter is attenuating to the incident light.
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Accused Products
Abstract
A thermochromic, thermotropic, or thermoreflective filter relies on a mismatch between the index of refraction of a thermotropic material (e.g., a liquid crystal) and a substrate material that includes refractive or diffractive features. At colder operating temperatures, the refraction mismatches are eliminated or minimized such that the filter becomes transparent, whereas at high operating temperatures the refraction mismatches are increased such that for light at appropriate incidence angles, the structure becomes highly reflective. This filter has particular but not exclusive application as a temperature-controlled “smart mirror” for use in windows, walls, roofing, and other building materials.
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Citations
18 Claims
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1. A thermoreflective or thermoabsorptive filter comprising
a diffractive-type polarizer having a first index of refraction; -
a thermotropic material adjacent to the diffractive-type polarizer;
whereinthe thermotropic material is configured such that below a threshold temperature the thermotropic material has a second index of refraction that is substantially similar to the first index of refraction such that incident light is not substantially refracted at an interface between the diffractive-type polarizer and the thermotropic material and thus the filter is largely transparent; and the thermotropic material is configured such that above the threshold temperature the thermotropic material has a third index of refraction that is substantially different from the first index of refraction such that incident light is substantially refracted at the interface between the diffractive-type polarizer and the thermotropic material and thus the filter is attenuating to the incident light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A thermoreflective filter comprising
a thermotropic, birefringent material having axial indices of refraction no and ne in a first temperature state and a single index of refraction ni in a second temperature state, and a single layer of one or more refractive structures positioned adjacent the thermotropic, birefringent material and capable of altering a path of an incoming photon; - wherein
no and ne and the axial indices of reflection of the refractive structures are selected such that interfaces between the thermotropic, birefringent material and the refractive structures have indices of refraction whereby in the first temperature state photons of a certain polarization and incidence angle beyond a critical angle are reflected upon striking the interfaces, while in the second temperature state photons of a same polarization and incidence angle are transmitted through the interfaces. - View Dependent Claims (12, 17)
- wherein
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13. A thermoreflective filter comprising
a thermotropic, birefringent material having axial indices of refraction no and ne in a first temperature state and a single index of refraction ni in a second temperature state, and a simile layer of one or more birefringent, refractive structures positioned adjacent the thermotropic, birefringent material, capable of altering the path of an incoming photon, and having axial indices of refraction close to no and ne; - wherein
no and ne and the axial indices of reflection of the birefringent, refractive structures are selected such that interfaces between the thermotropic, birefringent material and the birefringent refractive structures have indices of refraction whereby in the first temperature state photons of a certain polarization and incidence angle beyond a critical angle are strongly or totally reflected upon striking the interfaces, while in the second temperature state photons of a same polarization and incidence angle are transmitted through the interfaces. - View Dependent Claims (14, 15, 16, 18)
- wherein
Specification