Laser vision cuts through the night
STUTTGART - DaimlerChrysler researchers in Ulm, Germany, have developed an infra-red/laser night vision system that significantly increases a driver's ability to see clearly at night.
The system allows drivers to recognise darkly-clothed pedestrians and cyclists even at great distances. It also illuminates the road ahead over a distance of around 150m 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 about 100m.
Two laser headlights on the vehicle's nose illuminate the road by means of infra-red 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 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% of serious accidents occur at night, despite the fact that night driving accounts for less than 20% of total driving time in the country.
The main cause of accidents at night is poor visibility.
Conventional high-beam headlights do not provide sufficient illumination and many drivers have difficulty estimating correct distances. High-beams also blind the drivers of oncoming vehicles, limiting their ability to react quickly to potentially dangerous situations, particularly on wet roads. Poor visibility also causes drivers to tire very quickly with possibly fatal results.
DaimlerChrysler's infrared night vision system can do a lot to reduce these dangers, the company says. It is an active system with its own light source and, unlike passive systems, does not only depend 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 - lane markers, for example.
Researchers chose an infra-red 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 on to 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 infra-red light but only a greatly reduced amount of the blinding light from oncoming vehicles.