When you see the acronym ADAS (advanced driver assistance systems), you may automatically think of conventional and frequently discussed embedded vision implementations such as:
- Adaptive cruise control
- Lane departure warning systems
- Collision avoidance systems
- Pedestrian protection systems
- Automatic parking
- Traffic sign recognition
- Blind spot detection, and
- Driver drowsiness detection
However, a prototype system recently developed by Carnegie Mellon computer science professor Srinivasa Narasimhan, along with several other researchers, implements a lesser known ADAS variant known as adaptive light control. Covered by MIT Technology Review, and subsequently also picked up by Slashdot and Wired, the system automatically detects and compensates for incoming raindrops and snowflakes, reacting within 13 msec to dial down the intensity of affected portions of the headlight bank in order to reduce the reflective glare perceived by the driver.
Quoting from the MIT Technology Review writeup:
The system uses a digital projector to illuminate raindrops for several milliseconds while a camera mounted on the side of the projector captures each raindrop's location; software predicts where those raindrops will fall within the driver's field of view. Light rays from the headlight that would normally hit the raindrop are automatically switched off, reducing glare and leaving only the beams of light which travel uninterrupted in between the falling drops.
The system's operating range is three to four meters in front of the projector—the "critical range" at which glare is most distracting, according to tests conducted using a Toyota Prius.
The researchers simulated different car speeds and rainfall intensity in the laboratory by varying the speed at which simulated rain streaks—using actual water propagated in front of the projector—shot past the screen. The system could reliably make rain streaks invisible at low speeds and still increase visibility at higher speeds by dimming some of the rain.
In severe thunderstorm rain, the accuracy is 70 percent at 30 kilometers per hour and 15 to 20 percent at 100 kilometers an hour; that's how much of the rain is removed from view. Because water in a heavy rain is only 2 to 3 percent of the air volume, the rain can be filtered by dimming the headlights by just a few percent.
Substituting the hardware for a bigger and better camera would improve the system but increase its size and cost. However, making the system fast enough to reduce even more rain glare at highway speeds is important, because that's where there's greater risk for a catastrophic crash.
