US 5,877,897 · Granted 1999-03-02

The Smart Mirror Patent That Sees Inside Your Car

Imagine a rearview mirror that automatically darkens when headlights from a car behind you are too bright, while also watching the inside of your car for intruders. This patent describes a single smart chip with built-in cameras and sensors that controls multiple mirrors and lights in your vehicle, making driving safer and less annoying.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers a combined system that uses a photosensor array (essentially a tiny camera chip) to measure light coming from inside and outside a vehicle, then automatically adjusts the reflectance (brightness/darkness) of rearview and side mirrors independently based on those measurements. What's protected is the architecture of combining mirror control, headlight management, and interior motion detection into one integrated CMOS circuit, along with the specific logic that divides the sensor view into zones to control separate mirrors.

Why it matters

This patent represents a major shift in automotive safety and comfort. Before this, mirrors were either always reflective or required manual adjustment. By automating mirror dimming based on actual light levels and adding interior monitoring capability, Donnelly Corporation created the foundation for what became a standard feature in luxury and mainstream vehicles. The integration of multiple vehicle functions into a single smart chip also pioneered the kind of centralized sensor-based vehicle control that modern cars now rely on.

Real-world use

Every time you drive at night and the rearview mirror automatically darkens to prevent glare from the car behind you, you're using this patented technology in action.

Original USPTO abstract

A system apparatus, 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 controlling the vehicle lighting system and for monitoring a vehicle interior 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 vehicle interior. 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. The logic and control circuit uses the background light signal to control the vehicle lighting system. The logic and control circuit also determines a vehicle intrusion condition if there is movement within the vehicle in a vehicle intrusion detection mode of the vehicle interior monitoring system. The logic and control circuit also stores image data in memory in the compartment image data storage mode of the vehicle interior monitoring system.

Patent details

Publication number: US 5,877,897
Filing date: 1995-06-07
Grant date: 1999-03-02
Assignee: Donnelly Corporation
Inventor(s): SCHOFIELD; KENNETH, LARSON; MARK
CPC class: B60Q1/143

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