A new chip will help the car to see

Even if it was not quite enough to win the german future prize 2002, the nomination alone is just another sign for rudolf schwarte that the development of his team will be groundbreaking. In the coming years, three-dimensional perception of the environment is expected to enable completely new applications in industry, in the consumer sector, and especially in the automotive industry, which were previously impossible to realize due to the cost and coarseness of previous solutions, or which only provided images in 2d.

The most important element here is the photonic mixer device (pmd for short), an optoelectronic semiconductor chip developed by schwarte, who has been researching in the field of optoelectronics at the center for sensor systems at the university of goettingen for twenty years, together with bernd buxbaum and torsten gollewski.

The principle is the same as that of the bat: it obtains an impression of its surroundings by emitting sounds into space and interpreting the distance to objects based on the echo propagation time. "But our pmd works optically", explains buxbaum. A photodiode emits specially modulated light signals, such as infrared light, for this purpose. The light particles (photons) are reflected by the illuminated objects, hit the pixel elements in the pmd sensor and generate electrons there, the number of which correlates with the distance between object and pixel.

In principle, this is a simple comparison process, because the chip knows to the millimeter how long the light signal has to travel for a certain distance to the camera, "by correlating the electronic reference signal with the optical input signal ". Irritations caused by unwanted background light or sunlight no longer occur here. The pmd camera does not have to work with a resolution in the megapixel range as digital cameras do.

"We don’t need information to display the image, we just need a few thousand pixels to get three-dimensional information about the environment", explains buxbaum. Moreover, the whole process takes place in real time, which is not possible with conventional mechanical scanners, which are not only a million times coarser than the semiconductor chip, but also cost tens of thousands of euros.

The first rough area of application for pmd technology will be so-called driver assistance systems, which do not take away the driver’s responsibility for controlling his car, but are intended to relieve him and intervene in emergency situations. According to a study by the market research company j.D. Power could be equipped in the next years up to twelve million vehicles worldwide per year with such systems. Audi is one of the first car companies to actively engage in pmd development and in may this year established pmd technologies as a joint venture with schwarte’s team.

"For us in the automotive sector, real-time three-dimensional vision is a very critical component", explains torsten gollewski of audi electronics venture and already sees a revolution in the next few years, "namely, the seeing car, which will be able to do a lot, especially in the area of safety".

Even a simple lane change assistant would bring more safety for drivers and other road users in everyday life. "A small pmd camera integrated in the rear-view mirror monitors the blind spot and gives the driver a haptic warning as soon as he starts to overtake, such as a vibration on the steering wheel, if a vehicle is approaching dangerously in the left lane or if a cyclist is still between the curb and the car when turning right", buxbaum, who now works at pdm technologies, explains the principle.

Other applications included parking assistance or automatic acceleration and braking in stop-and-go traffic in the city or in traffic jams at walking pace. At "pre-crash" in addition to the rearward-looking camera in the exterior mirror, a forward-looking camera also captures the airspace in front of the vehicle. "Potential accident situations such as rear-end collisions or head-on collisions can be detected by the camera in time and lead to automatic emergency braking", explains buxbaum. In addition, this allows the airbags to be focused milliseconds earlier. A camera unobtrusively integrated in the roof area additionally monitors the seating position of the occupants in order to decide whether the deployment of the airbag and the full inflation could not seriously injure the person.

"For such things, previous solutions are simply too slow, too crude, too expensive and not robust enough for use in vehicles", explains buxbaum the decisive advantage of the pmd technology. Since almost all of the important technology is housed on a single chip, which can be manufactured inexpensively using the standard cmos semiconductor production process, a pmd camera of this type is said to cost only about 100 euros.

Audi plans to install the first pmd chips in its cars by 2004/2005 at the earliest. By then, the first pmd solutions in industry were allowed to monitor manufacturing processes and, for example, to control vacuum cleaners on their own through the apartment.

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