Active night vision improves night driving

DaimlerChrysler researchers in Ulm, Germany, have developed an infrared-laser night vision system that significantly increases a driver’s visibility at night.

The system allows drivers to recognize darkly-clothed pedestrians and cyclists even at great distances. It also illuminates the road ahead over a distance of around 500 feet without blinding the drivers of oncoming vehicles.

The night vision system is a big boost for safety and comfort: conventional high-beam headlights provide visibility of only 130 feet.

In operation, two laser headlights on the vehicle’s front end illuminate the road by means of infrared light that is invisible to the human eye. A video camera records the reflected image, which then appears in black and white on a screen located directly in the driver’s field of vision, or else as a so-called head-up display on the windshield.

The researchers in Ulm, who recently won the DaimlerChrysler Research Award for their invention, are currently testing the system in a bus. Further research prototypes will be developed throughout the year. The system will eventually be installed in premium production vehicles and other vehicles such as buses, trucks for transporting hazardous materials, emergency service vehicles and taxis, all of which require highly reliable safety systems.

Driving at night in bad weather is tiring and risky: the German Federal Statistics Office reports that some 40 percent of serious accidents occur at night, despite the fact that night driving accounts for less than 20 percent of total driving time in the country. The main cause of the accidents at night is poor visibility. Conventional high-beam headlights do not provide sufficient visibility, and many drivers therefore have difficulty estimating the correct distance. High-beams also blind the drivers of oncoming vehicles, thereby limiting their ability to react quickly to potentially dangerous situations, particularly on wet roads. Poor visibility also causes drivers to tire very quickly, something which can have fatal results.

DaimlerChrysler’s infrared night vision system can do a lot to reduce these dangers. It is an active system with its own light source and, unlike passive systems, not solely dependent on information resulting from the heat emitted by objects in the field of vision. This means that it can discern objects which display no difference in temperature from their surroundings-like lane markers, for example.

Researchers chose an infrared light source because such light is virtually invisible to the human eye, meaning it cannot blind drivers of oncoming vehicles. Its narrow spectral width also offers substantial benefits: preset optical filters are capable of dampening the blinding effects of oncoming headlights by a factor of 50 to 100, while still allowing the system’s reflected laser light to pass through.

The DaimlerChrysler team even came up with another trick to reduce the blinding effects of oncoming high-beams: the laser headlights send pulsating infrared light onto the road. Since the video camera’s electronic cover is synchronized with the frequency of the laser diode, the camera records all of the reflected infrared light but only a greatly reduced amount of the blinding light from oncoming vehicles.