US 6,313,454 · Granted 2001-11-06
The Smart Rain Sensor That Taught Cars to See
Imagine a tiny camera on your windshield that watches for raindrops and automatically turns on your wipers without you touching anything. This patent describes how a sensor uses image recognition to spot actual rain, ignore smudges and dust, and even detect foggy windows so your car can turn on the defroster.
The plain-English version
What it protects
The claim covers a rain detection system that uses an imaging sensor mounted separately from the window glass to capture images of the windshield surface. What's protected is the method of analyzing those images with edge detection—finding the sharp outlines of water droplets—and using a smoothing filter to ignore surface dirt and irregularities. The system also covers using a polarizing filter and light source to distinguish between interior fog and exterior rain, then automatically triggering windshield wipers or ventilation based on what it detects.
Why it matters
This patent represents a shift toward automatic, camera-based vehicle sensing rather than simple moisture switches. By combining image analysis with smart filtering algorithms, it enabled truly reliable rain-sensing wipers that don't false-trigger on dust or condensation. This type of technology became standard in premium vehicles and paved the way for modern driver-assistance systems that rely on windshield-mounted cameras to understand the environment around a car.
Real-world use
When you're driving a newer car in a light drizzle and the wipers start moving on their own at just the right speed, that intelligent behavior traces back to technologies like this patent's edge-detection approach.
Original USPTO abstract
A vehicular rain sensor system for detecting precipitation on an exterior surface of a window including a illumination sensor that is decoupled from the window. The illumination sensor is preferably an imaging array sensor which communicates a signal to a control which further determines whether rain is present on the window. The control preferably includes an edge detection function for detecting edges of precipitation droplets on the window and activating the windshield wipers of the vehicle when the number of edges detected exceeds a predetermined threshold value. A smoothing algorithm or filter is provided to account for surface irregularities on the window, thereby substantially precluding such irregularities from being erroneously detected as rain droplets by the edge detection function. The rain sensor system may further include a polarizing filter and an illumination source, such that the rain sensor system may not only prevent false signals of rain when only fog is present on an interior surface of the window, but also allows the rain sensor system to actually detect fog particles on an interior surface of the window, thereby allowing the control to further be connected to a ventilation blower within the vehicle for the purpose of activating the blower to eliminate the fog.
Patent details
- Publication number
- US 6,313,454
- Filing date
- 1999-07-02
- Grant date
- 2001-11-06
- Assignee
- Donnelly Corporation
- Inventor(s)
- BOS BRENT J., SCHOFIELD KENNETH, LARSON MARK L., LYNAM NIALL R.
- CPC class
- B60N2/002
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