US 5,715,093 · Granted 1998-02-03
The Smart Mirror That Dims Itself and Turns On Your Headlights
Imagine a rearview mirror that gets darker when bright headlights shine behind you at night, so you're not blinded. This patent covers a mirror that uses special light-sensitive glass and automatically adjusts its reflectivity while also flipping on your headlights when it gets dark. Two sensors watch the light coming from both directions — ahead and behind — to make smart decisions about what your car needs.
The plain-English version
What it protects
The claim covers an electrochromic rearview mirror system that automatically adjusts its reflectivity based on light levels detected by two directionally sensitive sensors, one pointing forward and one pointing backward. What's protected here is the specific combination of the mirror-dimming circuit, the headlight activation control, and the dual-sensor setup that works together. Someone copying this would infringe if they made a rearview mirror that darkens itself and controls headlights using the same two-sensor approach.
Why it matters
This patent locks down a convenient safety feature that became standard in modern vehicles. By automating the dimming of glare from oncoming headlights and automatically engaging your own headlights in low-light conditions, the system reduces driver distraction and improves visibility at night. Donnelly Corporation, a major automotive supplier, patented this innovation in the mid-1990s just as automakers were beginning to invest heavily in active safety systems. The dual-sensor design is clever because it lets the mirror respond intelligently to real-world driving conditions without requiring the driver to do anything.
Real-world use
Every time you drive on a dark highway and your headlights pop on automatically, or when you're stopped at a red light and your rearview mirror dims to block glaring headlights behind you, you're experiencing technology protected by this patent.
Original USPTO abstract
A vehicle automatic rearview mirror system with headlight activation control for establishing a reflectivity level of an electrochromic rearview mirror element and for controlling the activated state of a vehicle's headlights includes two light sensors, an electrochromic mirror element drive circuit that is responsive to light to which the two light sensors are exposed for establishing a partial reflectivity level for the vehicle's electrochromic rearview mirror element, and a headlight activation control that is responsive to light to which the two light sensors are exposed for activating the vehicle's headlights under low light conditions and deactivating the vehicle's headlights under high light conditions. The two light sensors are preferably directionally sensitive and aimed in different directions, one aimed forward of the vehicle and the other aimed rearward of the vehicle. The headlights are preferably activated as a function of the lowest light level to which either of the light sensors is exposed.
Patent details
- Publication number
- US 5,715,093
- Filing date
- 1996-12-17
- Grant date
- 1998-02-03
- Assignee
- Donnelly Corporation
- Inventor(s)
- SCHIERBEEK; KENNETH L., LYNAM; NIALL R.
- CPC class
- B60R1/088
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