Self-sweeping lasers could make LIDAR systems cheaper

September 04, 2015 // By Christoph Hammerschmidt
A team of researchers at the University of Berkeley has developed a novel concept to automate the way a light source changes its wavelength as it sweeps the surrounding landscape. The approach could be use for the design of cheaper LIDAR systems for vehicles.

Laser scanners deliver high-quality, high-resolution images of the surroundings of a car. Therefore, they are widely regarded as an indispensable ingredient to automated driving. The downside: They are very expensive; some carry a price tag one would expect at a compact car. This however could change: A team of researchers of the UC Berkeley led by professor Connie Chang-Hasnain has found a way to reduce power consumption, weight, size and cost of LIDAR system; likewise optical coherence tomography (OCT) systems could benefit from the development.

In automotive LIDAR applications, a laser beam is shining at a target; the amount of time it takes to come back is used to measure the distance to this target. The laser beam is then moved across a certain angular range or even by 360 degrees, much like a radar system for air traffic control purposes. Thus, the LIDAR system or laser scanner generates a rather detailed image, at a quality that is clearly superior to radar images due to the shorter wavelength of laser. As the laser moves along, it must continuously change its wavelength to enable the processing circuitry to differentiate between the reflected and the outgoing light. This requires a precise movement of mirrors within the laser cavity. The mechanisms controlling this movement are the reason why today’s LIDAR systems are so bulky and expensive, says Weijan Yang, one of the members of the Berkeley research team.

To avoid this problem, the researchers have integrated the semiconductor laser with the mirror. This leads to a drastic reduction of the size – the laser source can be shrunk to a few hundred square micrometres. At the same time, power consumption drops so far that the device can be powered by an AA battery, the authors say. The coupling of the laser with an ultra-thing, high-contrast grating mirror allowed the researchers to harness the physical force of the light to move the mirror. The