Variable Reflectance Mirrors and Windows

• US 20090002822A1
• Filed: 08/14/2008
• Published: 01/01/2009
• Est. Priority Date: 07/12/2004
• Status: Active Grant

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Tonar, William L., Bauer, Frederick T., Watson, Alan R.
• Granted Patent: US 7,679,809 B2
• Time in Patent Office: Days
• US Class Current: 359/493
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors

Abstract

Various structures for variable reflectance rearview mirrors and variable transmittance windows are disclosed. One embodiment pertains to the provision of a polarized reflector in a rearview mirror. Another embodiment pertains to the provision of a switchable cholesteric liquid crystal element in a window. Yet another embodiment pertains to the provision of a plurality of apertures in a reflector layer of a rearview mirror where the apertures are sized and positioned in alignment with light emitting areas of a display positioned behind the reflector layer. In another embodiment, a moveable display or mirror element is attached to a rearview mirror housing.

Claims

1. An automotive rearview mirror, comprising:

a. a substantially transparent substrate having a first and a second surface;

b. a polarization discriminating reflector optically coupled to the substrate, such that substantially all light incident on the second surface is transmitted through the substantially transparent substrate substantially unattenuated, while light characterized by a first polarization that is incident on the first surface is reflected back through the first surface in preference to light characterized by a second polarization, the second polarization being orthogonal to the first polarization,

wherein overall reflection, by the rearview mirror, of light incident on the first surface exceeds 52 percent.

2. An automotive rearview mirror according to claim 1, wherein the polarization discriminating reflector is electrically conductive.

3. An automotive rearview mirror according to claim 1, wherein the polarization discriminating reflector is a wire grid polarizer.

4. An automotive rearview mirror according to claim 1, further comprising:

an electronic device, optically coupled to the substantially transparent substrate through the polarization discriminating reflector, for transmitting or receiving light through the polarization discriminating reflector.

5. An automotive rearview mirror according to claim 4, wherein the electronic device is a light sensor.

6. An automotive rearview mirror according to claim 5, wherein said light sensor is positioned to sense glare light levels from the rear of the vehicle.

7. An automotive rearview mirror according to claim 4, wherein the electronic device is a display.

8. An automotive rearview mirror according to claim 7, wherein the electronic device is a liquid crystal display.

9. An automotive rearview mirror according to claim 1, further comprising:

a layer of electrically conductive material disposed adjacent to the polarization discriminating reflector.

10. An automotive rearview mirror according to claim 9, wherein the layer of conductive material is disposed between the polarization discriminating reflector and the substantially transparent substrate.

11. An automotive rearview mirror according to claim 9, wherein said conductive material is transparent and is chosen from a group consisting of fluorine-doped tin oxide, dopes zinc oxide, indium zinc oxide, indium tin oxide, and metal.

12. An automotive rearview mirror according to claim 9, wherein the layer of conductive material is reflective.

13. An automotive rearview mirror according to claim 1, further comprising a reflective layer disposed adjacent to the polarization discriminating reflector and causing reflection, by the rearview mirror, of light incident on the first surface to exceed 60 percent.

14. An automotive rearview mirror according to claim 13, wherein the reflective layer comprises at least one material chosen from a group consisting of silver, gold, and aluminum.

15. An automotive rearview mirror according to claim 13, wherein the reflective layer comprises a dichroic film stack

16. An automotive rearview mirror according to any of claims 1 or 13, wherein the rearview mirror is a prismatic mirror.

17. An automotive rearview mirror, comprising:

a. a substantially transparent substrate moveable between a non-tilted position and a tilted position, the substrate having first and second surfaces, the first surface corresponding to a field of view outside the mirror;

b. a polarizing reflector having an axis, the polarizing reflector optically coupled to the second surface such that substantially all light incident on the second surface is transmitted through the substrate to the field of view, while ambient light incident on the first surface from the field of view is reflected back to the field of view being preferentially polarized in a direction perpendicular to the axis,

wherein overall reflection, by the rearview mirror, of light incident on the first surface is at least 52 percent.

18. A mirror according to claim 17, further comprising:

an electronic device, optically coupled to the substrate through the polarizing reflector, for transmitting or receiving light from the electronic device through the substrate to the field of view.

19. A mirror according to claim 18, wherein, when the substrate is in the tilted position, the light transmitted from the electronic device to the field of view does not compete with the ambient light that is incident on the first surface from the field of view and reflected back to the field of view.

20. A mirror according to claim 17, wherein the first surface and the second surface form a dihedral angle.

21. An automotive rearview mirror according to claim 17, further comprising:

a reflective layer disposed proximate to the polarizing reflector, wherein the reflective layer causes the overall reflection, by the rearview mirror, of light incident on the first surface to exceed 60 percent.

22. A method for operating a rearview mirror assembly, the method comprising:

transmitting light, from a light source within the assembly, through an optical system to a field of view outside the assembly, wherein the optical system includes a substrate having first and second surfaces; and

reflecting ambient light, that is incident on the first surface and characterized by a firsts polarization, back through the first surface in preference to ambient light that is incident on the first surface and characterized by a second polarization, the second polarization being orthogonal to the first polarization,

wherein overall reflection, by the rearview mirror, of light incident on the first surface exceeds 52 percent.

23. A method according to claim 22, further comprising:

transmitting light incident upon the second surface is such a manner as to provide for substantially unattenuated transmittance through the optical system of the light incident upon the second surface.