In the race to develop a technology that, at its root, is about teaching robots how to understand their surroundings, Aurora just bought itself a fresh set of eyeballs.

The developer of self-driving car technology announced Thursday it’s acquiring lidar maker Blackmore, whose laser scanning tech offers the unusual and very helpful ability not just to detect nearby objects but to discern their velocity.

It also explains why Blackmore’s technology stands out among the scores of lidar makers vying for the business of Aurora and its competitors.

The Bozeman, Montana–based outfit, which started up a decade ago to do work for the defense industry, uses a “frequency modulated continuous wave” system, also known as a Doppler lidar.

When the infrared light hits an object and bounces back, the system determines both how far away it is (based on how long the round trip takes, like any lidar system) and its velocity.

It means that if your lidar doesn’t find that object again a millisecond later—hard to guarantee when you’re cruising down the highway and tracking things 250 meters away or more—it can still make a good guess about where it is and where it’s going.

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