Driving at night can be a challenge, even for the best drivers. Statistics show that nighttime driving is two to three times riskier than daytime driving for drivers, passengers, and pedestrians. But as the driver's distance vision increases, so does the level of safety. That simple fact prompted the latest technology from Sweden's Autoliv Inc.
The company joined BMW and other firms to develop a long-distance far-IR (infrared) camera system that lets drivers see some 300 m ahead. Most low-beam car headlights only possess a range of less than 100 m. Less than three months ago, the BMW Night Vision system was introduced on its 7 series cars in Europe (Fig. 1). Due to its long range, the Night Vision system provides car drivers with a time gain of 5 s (at a speed of 100 kph), compared to using a car's high-beam headlights.
Drivers can operate the Night Vision system manually via a switch next to the light switch. Or, the system can be controlled automatically by the car's speedometer and steering wheel. At 80 km/h, the speedometer automatically zooms the display in 1.5:1 increments to 24° and enlarges the objects in view. When the road bends, the steering wheel automatically pans the image 6° to one side. The display is mounted on the car's instrument panel just above the air-conditioning/heating vents.
The system has been six years in the making. Autoliv vice president Jan Carlson says it required the joint efforts of automotive parts suppliers like FLIR's Indigo Systems, Cherry Electrical Products, Umicore, and Dyncast, in addition to BMW's work. The system needs no illumination, and there's no risk of it getting blinded by roadside lights or oncoming headlights. It senses the heat of objects, animals, and humans within its range far enough in advance to enhance driver and pedestrian safety.
This system differs from other night-vision systems, which typically employ near-IR technology. In near-IR systems, an IR light source projects a beam into the area in front of the vehicle. Objects, animals, and humans alike reflect the light. An IR camera then photographs the potential obstacle. In a far-IR system, a thermal imaging camera directly registers the heat radiated from the obstacle, eliminating the need for a separate light source. Both types of IR systems process sensed signals into an image for display on a vehicle's instrument-panel screen.
The superiority of far-IR technology over near-IR technology is further affirmed by a scientific comparison conducted at the University of Michigan's Transportation Research Research Institute (UMTRI), published last December. The study focused on the detection of human beings. A leading research institution in transportation and road traffic, UMTRI partners with numerous leading automotive car and parts manufacturers.
The Night Vision system features a 36° wide-view angle lens, versus 12° to 16° for other available systems. It's also much smaller than existing IR cameras, about the size of two decks of playing cards. Actual measurements are 58 mm high by 55 mm wide by 68 mm thick, and it weighs 400 g.
AN INDUSTRY-WIDE TEAM EFFORT
At the core of the system lies a 320- by 240-pixel vanadium-oxide IR bolometer made by FLIR's Indigo Systems Division. This level of resolution is 400 times greater than the original imaging array developed by Indigo that targeted aerospace applications. The bolometer was one of many components that had to be developed for price-sensitive and demandingenvironment automotive applications (Fig. 2).
Belgium's Umicore came up with a new camera lens material called Gasir that featured better IR transmission properties than existing lens materials.A highly efficient molding process forms the material into a lens. BMW's camera cleaner jet, activated alongside the windshield-washer system, ensures a clear view at all times. The glass cover is heated at outside temperatures below 41°F.
To protect the camera package from condensation and moisture, Tyco Electronics developed hermetic sealing materials made on its Vemech technology. The entire camera assembly is placed in its own housing and mounted on the left side of the BMW's front bumper. Impact-resistant glass and a fine grid protect it. The Night Vision system is Autoliv's first product to go into serial production in a new development area: active safety. Autoliv also is studying radar systems and stereoscopic vision cameras.