FEATURE AUTOMOTIVE LIDAR g
effort by several vendors will likely make such units available in the next two years or so,’ he said. Then, to enable further adoption, he believes software must reach the threshold of true autonomy; initially in constrained environments, with regulators providing guidance to free fleet operators to offer services subject to appropriate constraints, that ensure safe operation. In this context, Lumotive differentiates itself with an alternative beam-steering approach to the existing ones that rotate mirrors or entire lidar systems. ‘Lumotive’s beam steering system leverages Liquid Crystal Metasurfaces (LCMs), which control the direction of both the transmitted and received laser pulses to scan the system’s field of view,’ Colleran explained. ‘LCM-based beam steering is completely solid state and exhibits several advantages compared to mechanical approaches.’ Among those advantages, he continued, are high performance. This is measured by range, resolution and frame rate. For such high performance, lidar systems require a large optical aperture. ‘Lumotive’s beam steering is very fast while still having large aperture,’ he explained. Like Valeo and Robosense, Lumotive uses time-of-flight (TOF) ranging to help commercial viability. TOF simply
Electro Optics
determines distances to objects by measuring the time it takes laser light to reach the object, then scatter and return to the lidar detectors. ‘This approach is the simplest architecture that can deliver the performance required for autonomous vehicles,’ Colleran said. Another approach, frequency-modulated continuous wave (FMCW), can be up to 100 times more sensitive than TOF approaches. ‘LCM- based beam steering can support any
“It’s a challenge to develop the technology. Another challenge is to build an industry to manufacture the many lidars we need for all of the vehicles”
range-finding method, so as complex approaches like FMCW become more affordable, our system can be upgraded cost-effectively.’ Lumotive uses common 905nm lasers, but exploits less common SPADs, which, Colleran said, ‘provide the highest gain of any available detector technology’. He highlighted that these silicon CMOS-based devices bring manufacturing advantages,
potentially combining the detectors ‘with complex receiver electronics to provide an extremely efficient integrated circuit in terms of cost and power’. Such capabilities mean that lidar systems will improve greatly in performance over the next few years, while decreasing in size and cost, Colleran predicted. ‘All-silicon approaches that benefit from Moore’s Law will improve more rapidly than architectures which use mechanical beam steering or more exotic semiconductors,’ he explained. Yole’s Debray agreed that such
operational matters are among the most important for the next leg of automotive lidar’s transformative journey. ‘It’s a challenge to actually develop the technology, something reliable that works properly,’ he said. ‘Another challenge is to build an industry to actually manufacture the many lidars that we need for all of the vehicles. If everything goes well, this technology will become much cheaper. It was a few thousand dollars, but it will be a few hundred.’ That’s significant, because lidar is still an
emerging technology, Debray added, even if most robotic cars use it. ‘In the next few years we should see lidar working together with cameras to improve the autonomy level and safety of more cars,’ he concluded. EO
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20 Electro Optics Augut/September 2019
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