US 6,396,397 · Granted 2002-05-28

The Patent Behind Your Car's Smart Headlight Dimmer

Imagine your car has two eyes that work together like human vision to judge how far away oncoming headlights are. When another car approaches, this system automatically dims your high beams so you don't blind the other driver. It's stereo vision—the same trick your brain uses to know how far away things are.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers a stereo imaging system mounted on a vehicle that uses two camera sensors to detect light sources and calculate their distance. What's protected is the specific method of comparing images captured by both sensors, measuring where a light source appears on each camera's sensor array, and then using the geometry between the two cameras (their separation distance and focal lengths) to compute the exact distance to that light source. The patent also covers using that distance calculation to automatically control vehicle systems like headlamps, wipers, brakes, or warning displays.

Why it matters

This patent represents an early application of stereo vision technology to automotive safety, specifically addressing the common road hazard of oncoming high-beam glare. By automating the decision to dim headlamps based on calculated distance rather than simple light-level thresholds, the invention reduces driver distraction and potential accidents. Donnelly Corporation, a major automotive supplier, secured protection for this approach during the late 1990s when active safety features were becoming a competitive differentiator in the industry.

Real-world use

When you're driving at night and an oncoming car approaches, modern vehicles with adaptive high-beam systems use stereo cameras to detect that vehicle's headlights and automatically switch to low beams—this patent describes the foundational technology making that happen.

Original USPTO abstract

A vehicular stereoscopic imaging system provides a calculation of a distance between one or more sensors on a vehicle and a light source or object in a target scene remote from the vehicle. The imaging system may be useful in a headlamp dimmer control system, such that the headlamps, are modulated between their low and high beams in response to the calculated distance and intensities and/or colors of the light sources sensed by the sensors. The stereoscopic imaging system determines the distance to the object by comparing similarly classified signals received by each of two imaging array sensors in order to determine a relative position of an image representing the light source on each sensor. The distance to the object or light source may then be calculated as a function of the respective positions on the sensors, the focal lengths of focusing optics associated with each sensor and a predetermined separation distance between the axes of the two sensors. An associated accessory, such as a display, headlamps, windshield wipers, a warning indicator or signaling device and/or the brake system of the vehicle may be adjusted or activated in response to an output of the imaging system.

Patent details

Publication number: US 6,396,397
Filing date: 1999-08-12
Grant date: 2002-05-28
Assignee: Donnelly Corporation
Inventor(s): BOS BRENT J., SCHOFIELD KENNETH
CPC class: B60R21/01538

View original record on Google Patents →

Want to file your own patent?

If you're thinking about a camera-based safety feature for vehicles, use our patent scanner to see what's already locked down in automotive imaging before you invest in prototyping.

Free patentability scan