Self-driving cars have advanced a lot in recent years—going from test track prototypes to fixtures on the roads of select cities. And while they still require human supervision on public roads, it’s predicted that in the not-so-distant future driverless cars will not only take over the road, they’ll do a much better job than we’ve been doing. No more drunk driving, texting while driving, falling asleep at the wheel, or other human errors will mean dramatically fewer accidents and fatalities.

All this is possible thanks in part to lidars, the sensors driverless cars use to “see” the road and guide themselves. To date, however, lidars are not only expensive, they’re really big. If you’ve ever seen a picture of Google’s self-driving cars, the lidar is that sizable spinning thing on top of the roof.

As self-driving cars approach commercial viability, smaller, cheaper sensors would be better. Luckily, sensors have been getting more miniature and affordable for decades, and lidars are no exception.

California startup Quanergy is making a lidar they say will cut the size of a typical lidar in half, and dramatically reduce the cost at the same time.

But first, what exactly are lidars, and how do they work?

Lidars use lasers to sense a car’s surroundings. They’re similar to radars, but rather than using radio waves, they use light in or near the visible spectrum to illuminate a target then analyze the reflection.

Though the technology’s been around for over 30 years, it’s only recently become usable in commercial applications thanks to advances in laser technology and computational speed. Lidar’s narrow laser beam can map objects in high resolution.

Current self-driving cars are topped with a clunky black dome slightly smaller than a basketball, or an awkwardly-mounted system of rotating, blinking parts. Existing lidars use spinning mirrors to direct the laser beams they bounce off the objects around them.

Quanergy recently announced a game-changing advance in lidar technology. Rather than using mirrors to direct and analyze laser beams, Quanergy’s lidars are steered with a chip that contains a million tiny antennas. Called the S3, it’s the first-ever solid-state lidar with no moving parts.

Quanergy describes the S3 as “more compact than a small point-and-shoot camera, weighing less than 11 ounces, and having low power consumption.” It can scan objects and areas in higher resolution and with greater range (200 meters compared to 120) than existing lidars, and its lack of moving parts means it’s less likely to break down and require repairs.

Through the interaction of its laser, receiver, and signal processor, the S3 generates half a million point-cloud data points per second.

The sensors are slated to be used on prototype vehicles in 2017 and commercial vehicles in 2018. Instead of the awkward contraptions that currently sit atop driverless cars, the smaller sensors can be concealed in different spots around the car, like inside its side mirrors or bumper.

As tends to happen with miniaturization, the technology is getting cheaper as it gets smaller.

Quanergy competitor Velodyne’s most advanced sensor, the PUCK VLP-16, is currently priced at $7,999. Quanergy plans to sell the S3 for $250. It will take three S3s for a car to get an all-around view, but that’s still well under a grand. Velodyne is also developing the VLP-32, which will sell for under $500 and will be powerful enough for autonomous driving.

Image credit: Steve Jurvetson/Wikimedia Commons