Apple has been evaluating at least four companies as possible suppliers of next-generation lidar sensors in self-driving cars while continuing to work on its own lidar unit, Reuters sources have said.

The news agency's exclusive report said talks were focused on next-generation lidar.

Its sources said Apple wants lidar units smaller, cheaper and more easily mass produced than current technology and reportedly has demanded a "revolutionary design".

Possible suppliers were not named.

Reuters said the development suggested Apple wanted to develop the entire chain of hardware to guide autonomous vehicles and had joined automakers and investors in the contest to find winning technology.

It noted current lidar systems, including Velodyne units mounted on Apple's fleet of self-driving test vehicles, use laser light pulses to provide precise images of the environment around the car. But the systems can cost US$100,000 and use mechanical parts to sweep the laser scanners across the road.

That makes them too bulky and prone to failure for use in mass-produced vehicles, Reuters said. The shortcomings have encouraged a $1bn investment at dozens of companies to make lidar smaller, cheaper and more robust.