One of the most promising approaches has been honed by Canesta Inc. (Sunnyvale, Calif.) over the last seven years since its founding in 1999. Canesta's CMOS image chip detects the distance to every object in a scene simultaneously, as opposed to ultrasonic which only senses distance to the nearest objects, by virtue of its time-of-flight calculations performed in hardware for every pixel on its imaging chip.
"Canesta's approach looks promising, because it uses only a single camera and is based on CMOS technology which is critical to keeping costs low," said Alexander. "Plus its use of the time-of-flight method of calculating distance enables all types of automotive applications."
Time-of-flight refers to Canesta's use of an infrared light source to illuminate scenes with invisible light, then measure the time it takes that light to fly from the emitter, which is beside the imager, out to the object, then back to the CMOS detector. By using hardware on the CMOS chip to calculate distance for every pixel in a scene, machine vision algorithms can easily group elements into objects, essentially perceiving rather than just sensing.
"We use a standard .18 micron CMOS process that any foundry can provide," said Jim Spare, president and chief executive officer at Canesta. "Also our SunShield technology enables us to perceive depth regardless of the lighting conditions rather than wait for an adaptive algorithm to kick in."
SunShield adds circuitry at every pixel which senses the difference between the ambient light every 100 microsecondsvirtually instantaneouslycompared to adaptive software algorithms, which can take milliseconds to adapt to changing light conditions.
"One of the things that distinguishes Canesta is its Sunshield technology that solves one of the hardest problems of using a camerathat is it must be able to work in varying light situations to be safe enough to deploy in consumer automobiles," said Alexander. "I think Canesta is really on to something there, but they still have a ways to go to crack all these different automotive applications. I believe that it will be the 2008 and 2009 models in which we will see the first Canesta's 3D camera in consumer vehicles."
Canesta's first deployed automotive application will likely appear in new Hondas that use its 3D camera in the cockpit headliner to sense the size of a passenger and appropriately meter air bag deployment. Today this function is performed by pressure pads in the seats, but using a single CMOS camera may be just as cheap as pressure pads, while enabling other applications to share the camera, such as a "drowsy" alarm that can perceive the difference between blinking and when a driver's eyes are beginning to shut from lack of sleep.
Other companies are also experimenting with making CMOS image chips that detect depth on a pixel-by-pixel basis, notably International Electronics & Engineering S.A. (Luxemburg, Germany). Another company, Mobileye Inc. (Southfield, Mich.), is sidestepping the 3D imagers, opting instead to use a normal 2D camera with their CMOS hardware accelerator chip that analyzes perspective to calculate distance.