Glare Management of Reflective and Thermoreflective Surfaces

• US 20090268273A1
• Filed: 04/23/2009
• Published: 10/29/2009
• Est. Priority Date: 04/23/2008
• Status: Active Grant

• Current Assignee: Ravenbrick, LLC
• Original Assignee: Ravenbrick, LLC
• Inventors: Powers, Richard M., McCarthy, Wil
• Granted Patent: US 8,634,137 B2
• Time in Patent Office: Days
• US Class Current: 359/288
• CPC Class Codes: B32B 2307/42 Polarizing, birefringent, filtering
• CPC Class Codes: B32B 2551/00 Optical elements
• CPC Class Codes: B32B 37/18 involving the assembly of discrete sheets or panels only
• CPC Class Codes: B32B 38/1808 characterised by the laying up of the layers
• CPC Class Codes: G02B 27/281 used for attenuating light intensity, e.g. comprising rotatable polarising elements
• CPC Class Codes: G02B 5/0231 the surface having microprismatic or micropyramidal shape macroscopic prism arrays G02B5/045
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0247 by means of voids or pores
• CPC Class Codes: G02B 5/0252 using holographic or diffractive means
• CPC Class Codes: G02B 5/0268 characterized by the fabrication or manufacturing method
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/0284 used in reflection
• CPC Class Codes: G02B 5/0289 used as a transflector
• CPC Class Codes: G02B 5/0294 adapted to provide an additional optical effect, e.g. anti-reflection or filter
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133548 Wire-grid polarisers
• CPC Class Codes: G02F 2201/346 distributed (Bragg) reflector
• CPC Class Codes: G02F 2201/38 Anti-reflection arrangements

Abstract

The reflectivity and transmissivity of building and vehicle surfaces is maintained while employing partial, variable, selective, or asymmetric diffusers between a surface and an external light source such that the reflected light is diffused to produce a reduction in glare, while minimally effecting the specular or collimated transmission (if any) of light through the surface. Glare is also reduced by utilizing diffuser devices that reflect light in a temperature dependent manner.

Claims

1. A method for reducing glare from partially reflective or thermoreflective surfaces without significantly degrading the energy benefits of reflection comprising

placing an at least partially diffusive filter between either a partially reflective surface or a thermoreflective surface and an external light source, wherein

light transmitted through the partially reflective surface or the thermoreflective surface is diffused only once, and

light reflected from the partially reflective surface or the thermoreflective surface is diffused twice, thereby transforming specular reflections from the partially reflective surface or the thermoreflective surface into diffusive reflections.

2. The method of claim 1, wherein

the at least partially diffusive filter comprises a variable diffusive filter;

and

light transmitted through and reflected from the partially reflective surface or the thermoreflective surface is highly diffused under a first condition of an external variable, and is not diffused or is diffused to a lesser extent under a second condition of the external variable.

3. The method of claim 2, wherein the external variable comprises one or more of an environmental temperature or an electric field.

4. The method of claim 2, wherein the variable diffusive filter comprises a thermodiffusive filter that is mostly transparent within a first temperature range and that is mostly diffusive within a second temperature range.

5. The method claim 1, wherein

the at least partially diffusive filter comprises a selectively diffusive filter;

and

light is diffusively reflected from the partially reflective surface or the thermoreflective surface for certain polarities or wavelengths, while light of other polarities or wavelengths is transmitted through the selectively diffusive filter in a substantially collimated or non-diffuse manner.

6. The method of claim 5, wherein

the at least partially diffusive filter comprises an asymmetrically diffusive filter;

and

incident light from a first direction or first range of directions is diffused more than incident light from a second direction or second range of directions.

7. The method of claim 6, wherein

light reflected from the partially reflective surface or the thermoreflective surface is diffused significantly more than light transmitted through the partially reflective or thermoreflective surface.

8. The method of claim 6, wherein the asymmetrically diffusive filter incorporates irregularly fashioned metamaterials.

9. The method of claim 1, wherein the at least partially diffusive filter comprises a thermochromic distributed Bragg reflector device.

10. The method of claim 1, wherein the at least partially diffusive filter comprises a polarizing thermochromic distributed Bragg reflector device.

11. A method for increasing the privacy of transparent, translucent, or partially reflective surfaces comprising

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, wherein

light transmitted through the transparent surface, the translucent surface, or the partially reflective surface is diffused only once, and

light reflected from the transparent, translucent, or partially reflective surface is diffused twice, so that the reflected light is approximately twice as diffuse as the transmitted light.

12. The method of claim 11, wherein

the at least partially diffusive filter comprises a variably diffusive filter;

and

light transmitted through and reflected from either the transparent surface, the translucent surface, or the partially reflective surface is diffused under a first condition of an external variable, and is not diffused or is diffused to a lesser extent under a second condition of the external variable.

13. The method of claim 12, wherein the external variable comprises one or more of an environmental temperature or an electric field.

14. The method of claim 12, wherein the variable diffusive filter comprises a thermodiffusive filter that is mostly transparent within a first temperature range and that is mostly diffusive within a second temperature range.

15. The method of claim 11, wherein

the at least partially diffusive filter comprises a selectively diffusive filter;

and

light is diffusively reflected from the transparent surface, the translucent surface, or the partially reflective surface for certain polarities or wavelengths, while light of other polarities or wavelengths is transmitted through the selectively diffusive filter in a substantially collimated or non-diffuse manner.

16. The method of claim 11, wherein

the at least partially diffusive filter comprises an asymmetrically diffusive filter;

and

incident light from a first direction or a first range of directions is diffused more than incident light from a second direction or a second range of directions, and

a view from the first direction or a first range of directions is significantly more obscured than the view from the second direction or a second range of directions.

17. The method of claim 16, wherein the asymmetrically diffusive filter incorporates irregularly fashioned metamaterials.

18. The method of claim 11, wherein

any of the transparent surface, the translucent surface, or the partially reflective surface comprises a window unit;

and

reflected light as seen by an outside observer is substantially diffusive whereas transmitted light as seen by an inside observer is substantially non-diffusive or collimated, thereby increasing interior privacy.

19. An energy-efficient device that reduces glare from reflection of incident light comprising

a first reflective polarizer;

a second reflective polarizer;

a depolarizer positioned between the first reflective polarizer and the second polarizer;

a transparent substrate affixed to the second reflective polarizer; and

an at least partially diffusive filter affixed to the first reflective polarizer.

20. The energy-efficient device of claim 19, wherein the depolarizer is a thermochromic depolarizer.

21. The energy-efficient device of claim 19, wherein the depolarizer is an electrochromic depolarizer.

22. The energy-efficient device of claim 19, wherein the at least partially diffusive filter is a variable diffuser with a light scattering ability controllable by one or more external conditions.

23. The energy-efficient device of claim 22, wherein the one or more external conditions comprise a temperature and/or an applied electric field.

24. The energy-efficient device of claim 22, wherein the variable diffuser further comprises a thermodiffusive filter that is mostly transparent within a first temperature range and that is mostly diffusive within a second temperature range.

25. The energy efficient device of claim 24, wherein the thermodiffusive filter comprises

a first transparent material;

and

beads or bubbles of a second transparent material, wherein

within a first temperature range, an index of refraction of the first transparent material is substantially the same as an index of refraction of the second transparent material; and

within a second temperature range, one or both of the index of refraction of the first transparent material and the index of refraction of the second transparent material change such that there is a substantial mismatch between the index of refraction of the first transparent material and the index of refraction of the second transparent material.

26. The energy efficient device of claim 25, wherein the first transparent material and the second transparent material are selected such that the thermodiffusive filter functions as a thermochromic diffusive Bragg reflector.

27. The energy-efficient device of claim 19, wherein the partially diffusive filter is a selective diffuser that only diffuses light of particular wavelengths or particular polarities.

28. The energy-efficient device of claim 19, wherein the partially diffusive filter is an asymmetric diffuser that scatters light passing through the device in a first direction more strongly than light passing through the device in a second direction.

29. An energy-efficient device that reduces glare from reflection of incident radiant energy comprising

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.

30. The energy-efficient device of claim 29, wherein each of the first diffusively reflective polarizer and the second diffusively reflective polarizer comprises a cholesteric liquid crystal circular polarizer.

31. The energy-efficient device of claim 29, wherein each of the first diffusively reflective polarizer and the second diffusively reflective polarizer comprises a retro-reflective polarizer.

32. The energy-efficient device of claim 29, either the first diffusively reflective polarizer, the second diffusively reflective polarizer, or both comprise a chiral wire grid polarizer.

33-58. -58. (canceled)