US 6,356,376 · Granted 2002-03-12
The Mirror That Dims Itself and Shows You the Weather
Imagine a rearview mirror that automatically darkens when headlights behind you are too bright, but has a transparent spot where information like temperature or compass direction can glow through. This patent describes how to build a smart mirror using electrochromic material—a substance that changes how much light it lets through when you apply electricity to it.
The plain-English version
What it protects
The claim covers a rearview mirror assembly where an electrochromic layer (material that darkens electronically) sits between two glass panes, with a reflective metal coating on the back layer that has a transparent window built into it. What's protected is the specific sandwich structure: the way the conductive materials are arranged, how the reflective layer includes both opaque and see-through regions, and the ability for a light source behind the mirror to project information (like a compass or temperature reading) through the transparent zone while the rest of the mirror can still dim to reduce glare.
Why it matters
This patent, assigned to Gentex Corporation, represents a key innovation in electrochromic automotive mirrors—a category that became standard on higher-end vehicles. By combining automatic anti-glare darkening with an embedded display capability, the patent solved a real problem: drivers needed glare reduction without losing the ability to see useful information. The technology allowed aftermarket and OEM manufacturers to offer single-component smart mirrors instead of layering separate displays and dimming systems, making the solution more elegant and manufacturable.
Real-world use
When you're driving at night and a car behind you flashes its high beams, the mirror automatically darkens to protect your eyes, while still displaying the outside temperature or compass bearing through a small clear window in the center of the glass.
Original USPTO abstract
An electrochromic mirror is disclosed for use in a vehicle rearview mirror assembly having a light source positioned behind the electrochromic mirror for selectively projecting light through the mirror. The electrochromic mirror includes front and rear spaced elements each having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber, a layer of transparent conductive material disposed on the rear surface of the front element, at least one solution-phase electrochromic material contained within the chamber, and a second electrode overlying the front surface of the rear element in contact with the electrochromic material. The second electrode includes a layer of reflective material and a coating of electrically conductive material that is at least partially transmissive and is disposed over substantially all of the front surface of the rear element. The second electrode further includes a region in front of the light source that is at least partially transmissive. The electrically conductive coating may include a single transparent layer or a plurality of partially reflective and transmissive layers, or an electrically conductive dichroic coating. The light source may be an information display, such as a compass/temperature display as used in an inside rearview mirror, or may be a signal light as used in an outside rearview mirror.
Patent details
- Publication number
- US 6,356,376
- Filing date
- 1999-05-14
- Grant date
- 2002-03-12
- Assignee
- Gentex Corporation
- Inventor(s)
- TONAR WILLIAM L., FORGETTE JEFFREY A., ANDERSON JOHN S., BECHTEL JON H., CARTER JOHN W., STAM JOSEPH S.
- CPC class
- B60Q1/2665
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