Gentex's SmartBeam will debut on unnamed Lincoln Mercury vehicles in the 2004 model year. Industry analysts said the introduction could prove significant, especially if it leads to greater adoption of CMOS imagers in the auto industry.

"There's going to be a bunch of potential applications for this technology," said Paul Hansen, publisher of The Hansen Report on Automotive Electronics. "It makes sense to use the technology in backup applications, as well as for lane-change detection and adaptive cruise control."

Some engineers believe cameras-on-chip could also find applications in airbag deployment systems and complex intelligent-vehicle systems.

Gentex (Zeeland, Mich.), a maker of automatic-dimming rearview mirrors, will use CMOS imaging technology from Photobit Corp. (Pasadena, Calif.). Gentex engineers, who spent several years developing SmartBeam, said they chose CMOS imagers over charge-coupled devices mainly for cost reasons. In selecting camera-on-chip technology, however, Gentex said it had to search for a CMOS imager that would provide higher sensitivity.

Automakers hope the new technology will be an improvement on preceding automatic high-beam systems, which were phased out in 1994. Those systems, which typically used single photosensors to measure the total luminance of the surrounding scene, were often compromised by an inability to recognize bright reflections and automotive tail lamps. As a result, they occasionally turned the high beams on and off at the wrong times.

"Several years ago, we recognized that to do this right, you need more information than a single photodiode can give you," said Joe Stam, an electronics research engineer for Gentex. "We decided that an image sensor would be the ideal technology."

Stam said Gentex chose Photobit's technology because it offered greater sensitivity than other CMOS imagers. "Photobit's pixel architecture gives us that," he said.

The system works by breaking the surrounding scene into discrete segments and mapping each piece of the scene to an individual pixel. It then sends information from the pixels to a microprocessor that uses proprietary algorithms to determine the brightness, color, size, position and movement of objects.

Pixel scaling

Photobit, which was started by researchers from NASA's Jet Propulsion Laboratory, employs a scheme that allows a CMOS imager to gain sensitivity by scaling the pixel size. In essence, the system uses larger pixels to collect more light. But it does so without a corresponding rise in capacitance, which would ordinarily diminish the output signal.

That scheme, in tandem with the imager's "windowing" capability, enables the SmartBeam system to focus on a 3 x 3-pixel area and then read out pictures from that window at a rate of 480 frames per second. As a result, SmartBeam can use image-processing techniques to examine a point of light and then determine, for example, whether that point is a headlight or a street lamp. In the past, automatic high beams had difficulty making such determinations.

Gentex engineers said they also worked with Photobit on color recognition. By employing a proprietary optics design, the SmartBeam system is said to be capable of a recognizing red taillights. "When you're looking for tail lamps, you can't just go by brightness, because tail lamps are about one-thousandth as bright as headlights," Stam said. "So we need another piece of information, and that's color."

Although the application is a first for the automotive industry, it is one of many applications in other industries for Photobit's CMOS imaging technology. The company's systems are also being used in PC video cameras, machine vision and even cameras-in-a-pill, for medical imaging.