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Optoelectronics Headlight control through eye-tracking By Christoph Hammerschmidt Controlling your headlamp with a move of your eyes: What sounds like Sci-Fi can soon be reality. Carmaker Opel is developing a technology that controls direction and brightness of the vehicle’s headlights by tracking the driver’s eyes. Engineers at General Motors’ German subsidiary had the idea to control the light by the direction of the driver’s look already two years ago. In the beginning, they used a simple webcam to track distinctive features like nose and eyes to determine the viewing direction. These data were turned into instructions for the actuators. Though this approach yielded quite promising results, it turned out that the huge amounts of The beam of the AFL+ Xenon headlamp automatically adapts to various traffic situations and weather conditions. data could not be processed fast enough, and the webcam’s frame rate was too low to meet real-time traffic requirements. In the meantime, the engineering team successfully optimized the camera parameters and they adapted the eye-tracking algorithm for better real-time behaviour. In twilight and darkness, a fast camera now scans the eyes of the driver more than 50 times per second, using infrared sensors at the margins and with photo diodes in the centre of the image field. Thanks to much faster data forwarding and processing the headlight actuators now react virtually in real-time, horizontally as well as vertically. However, one problem remains: the human eye unknowingly “jumps” around all the time. Would the system reflect these movements, the cone of light would move hectically. “For this reason, we developed sophisticated delay algorithms that cause the cone of light to move smoothly”, says Ingolf Schneider, manager lighting technology for Opel. There is no need to constantly re-calibrate the eye tracker, also the body height of the driver is not relevant. The eye-tracking technology however will only be introduced in the future. Current-generation vehicles are equipped with the AFL+ adaptive headlight system, which already offers up to ten lighting functions controlled by a frontal camera. For example, the light cone of a xenon headlamp is automatically adapted to different traffic situations as well as road and weather conditions - with variable light distribution within urban areas and country roads. The system has different light settings for streets, motorways and bad weather, and adjusts the settings automatically, controlled by the camera. Additional functions include dynamic cornering light and turning light. Direction and intensity of the light beam are controlled according to the angle of lock and vehicle speed. In parallel to the continuing improvement of AFL+ and the development of the eye-tracking lighting generation of the future, Opel’s International Technical Design Centre in Rüsselsheim is preparing final validation tests for the LED matrix lighting system. Nanolaser enables on-chip photonics By R. Colin Johnson Sending communications signals around chips, and between chips and boards is an area of intense research worldwide. Now University of Washington (Seattle) and Stanford University (Calif.) have created an on-chip laser that can be electro-modulated for easy optical communications. Most materials from which on-chip lasers can be built are not compatible with silicon substrates, but these researchers has high hopes for their atomically thin (just 0.7 nanometers thick) laser can be integrated onto standard silicon chips. “Today we are using a tungsten photonics cavity sandwiched between layers of selenium, but we hope to achieve the same results with silicon nitride in the future,” said EE professor Arka Majumdar, who did the work with fellow professor Xiaodong Xum and his doctoral candidate assistant, Sanfeng Wu. As the thinnest semiconductor today, according to Majumdar An ultra-thin semiconductor using just three atom thick material stretches across a photonic cavity to emit light. (Source: U of Washington). and Wu, it is super energy efficient and can be electromodulated with a signal of only 27 nanowatts, making it ideal for on-chip communications. The new material has also excited other groups who are busy building light-emitting diodes (LEDs), solar cells and even transistors using this new semiconductor. Creating a nano laser out from it required building an optical confinement cavity to intensify the light, fashioned from a single layer of the tungsten-based material. The gain of the material can be carefully tuned and it uses the standard frequencies for on-chip, between chip and between board communications. Next the group will carefully characterize the material as well as experiment possibly improving it further by using silicon nitride. Other researchers contributing to the work include John Schaibley of the University of Washington and Liefeng Feng of the University of Washington and Tianjin University in China, Sonia Buckley and Jelena Vuckovic of Stanford, Jiaqiang Yan and David G. Mandrus of Oak Ridge National Laboratory and the University of Tennessee, Fariba Hatami of Humboldt University in Berlin and Wang Yao of the University of Hong Kong. 22 Electronic Engineering Times Europe April 2015 www.electronics-eetimes.com


EETE APR 2015
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