US 5,760,962 · Granted 1998-06-02
The Smart Mirror That Stops Headlight Glare Before It Blinds You
Imagine a rearview mirror that automatically darkens when a car behind you flashes its bright headlights—so you don't get blinded. This patent covers the sensor and brain that make that happen: a tiny camera chip that watches the light hitting your mirrors and tells them when to dim or brighten, independently for each mirror.
The plain-English version
What it protects
The claim covers a system that uses a photosensor array (a grid of light-detecting pixels) to monitor light levels across multiple zones—one for the rear window, one for each side mirror. The control circuit processes these signals to calculate both background light and peak brightness in each zone, then sends independent dimming commands to the rearview and side mirrors. What's protected is this specific method of dividing the sensor's field of view into zones and controlling each mirror's reflectance separately based on its own zone's light data.
Why it matters
This patent protects a foundational approach to automatic anti-glare mirror technology that became standard in automotive safety systems. By splitting the sensor array into independent zones, the invention allows the system to dim only the mirror receiving harsh light—rather than darkening all mirrors at once—which improves driver visibility and safety during night driving. The integration of the light sensor and control logic into a single VLSI chip also reduced manufacturing cost and complexity, making the technology feasible for mass-market vehicles.
Real-world use
When you're driving at night and headlights from the car behind you flood your rearview mirror, the system's photosensor detects the sudden brightness spike and automatically adjusts the mirror's reflectance to prevent glare—all within a fraction of a second, without you touching anything.
Original USPTO abstract
A system apparatus, structure and method for controlling a plurality of variable reflectance mirrors (or mirror segments), including a rearview mirror and side view mirrors, which change their reflectance level in response to a plurality of drive voltages applied thereto, for an automotive vehicle. The system includes a light sensing device and a control circuit formed as a single VLSI CMOS circuit. The light sensing device comprises a photosensor array having a field of view encompassing a rear window area and at least a portion of at least one side window area of the vehicle. The logic and control circuit determines a background light signal from photosensor element signals generated by the photosensor elements in the photosensor array indicative of light levels incident on the photosensor elements. The circuit also determines a peak light signal in three different zones or sub-arrays of the photosensor array. The zones or sub-arrays may correspond to three mirrors or mirror segments. The peak light signals in each of the zones and a common background light signal are used to determine independent and separate control signals, which are then output to separate mirror drive circuits for independently controlling the reflectance level of the rearview mirror and the left and right side view mirrors, or alternatively the segments of a mirror.
Patent details
- Publication number
- US 5,760,962
- Filing date
- 1996-04-01
- Grant date
- 1998-06-02
- Assignee
- Donnelly Corporation
- Inventor(s)
- SCHOFIELD; KENNETH, LARSON; MARK
- CPC class
- H04N7/181
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