Scientists have developed a new 3-D imaging system that can remotely sense objects across distances as long as 30 feet, 10 times farther than what could be done with current low-power laser systems.
The system could one day enable a self-driving car to spot a child in the street half a block away, let people answer their smartphone from across the room with a wave of hand, or play “virtual tennis” on their driveway.
The new system relies on LIDAR (“light radar”), a 3-D imaging technology that uses light to provide feedback about the world around it.
LIDAR systems of this type emit laser light that hits an object, and then can tell how far away that object is by measuring changes in the light frequency that is reflected back.
It can be used to help self-driving cars avoid obstacles halfway down the street, or to help video games tell when you are jumping, pumping your fists or swinging a “racket” at an imaginary tennis ball across an imaginary court.
In contrast, current lasers used in high-resolution LIDAR imaging can be large, power-hungry and expensive.
“While meter-level operating distance is adequate for many traditional metrology instruments, the sweet spot for emerging consumer and robotics applications is around 10 meters,” said Behnam Behroozpour from the University of California, Berkeley.
Gaming systems require big, bulky boxes of equipment, and you have to stand within a few feet of the system for them to work properly, Behroozpour said.
Bulkiness is also a problem for driverless cars such as Google’s, which must carry a large 3-D camera on its roof.
The researchers sought to shrink the size and power consumption of the LIDAR systems without compromising their performance in terms of distance.
The team used a type of LIDAR called frequency-modulated continuous-wave (FMCW) LIDAR, which they felt would ensure their imager had good resolution with lower power consumption, Behroozpour said.
This type of system emits “frequency-chirped” laser light (that is, whose frequency is either increasing or decreasing) on an object and then measures changes in the light frequency that is reflected back.
To avoid the drawbacks of size, power and cost, the team exploited a class of lasers called MEMS tunable VCSELs.
MEMS (micro-electrical-mechanical system) parts are tiny micro-scale machines that, in this case, can help to change the frequency of the laser light for the chirping, while VCSELs (vertical-cavity surface-emitting lasers) are a type of inexpensive integrable semiconductor lasers with low power consumption.