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Campus engineers create self-sweeping laser with wide range of applications

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SEPTEMBER 07, 2015

A team of UC Berkeley engineers invented a 3-D imaging technique that could make self-driving cars, remote sensors and a host of other technologies much more accessible to consumers.

The team, led by campus electrical engineering and computer sciences professor Connie Chang-Hasnain, published its findings Thursday. The new technique has the potential to dramatically decrease the size, cost and energy input of 3-D imaging devices, which create maps of the environment by measuring distances.

The new approach relies on photons from a laser to direct a lightweight mirror in an oscillating pattern, which, in turn, changes the frequency of that laser.

“This is the first example of a laser that has mechanical oscillation, where the system is driven by the laser itself,” said Eli Yablonovitch, a campus EECS professor. “And because it sweeps mechanically, it covers a large frequency (range), which makes it fantastic to use for LIDAR.”

Chris Chase/Bandwidth10 Inc.
Bandwidth10 Inc./Courtesy

LIDAR, or light detection and ranging, is a type of photography that measures precise distances by shining a laser on an object and then analyzing the light that is reflected back.
One prominent application of LIDAR is in self-driving cars, which currently have systems that are bulky and expensive, according to Chang-Hasnain.

“Self-driving cars use four to six huge LIDAR systems that are on top of the car,” Chang-Hasnain said. “But our system could be the size of a cellphone.”

The new 3-D mapping technology can be so small because it essentially powers itself, aside from the minimal energy — possibly just one AA battery — required to illuminate the laser. Energy from the photons of this laser can move the mirror, in part, because the mirror is only 100 picograms — about 10 billion times lighter than a standard bulk mirror in current LIDAR systems — and, in part, because the photons exert force at exact moments.

“A good analogy is a child on a swing,” Chang-Hasnain said. “Even a small child is able to get very high on the swing because the child applies force in the right direction at the right time, and that’s what the laser is doing to the mirror.”

The new system could correspond to a drastic decrease in the technology’s cost, which Chang-Hasnain said is affected only by the price of materials. She added that lasers themselves are not particularly expensive, as evidenced by the widespread availability of laser pointers.

In addition to their lower cost, the self-sweeping effect of the lasers allows them to fluctuate between a broad range of frequencies and thus take very precise measurements.

“It’s like the difference between seeing in color versus just black and white,” Yablonovitch said.

Contact Logan Goldberg at 

LAST UPDATED

SEPTEMBER 08, 2015


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