How the LIDAR tech GM just bought probably works

Re:How the LIDAR tech GM just bought probably works by joshvm on Tuesday October 24, 2017 @03:27PM (#15544484)

The Mesa Imaging SwissRanger is an amplitude modulated system, not frequency modulated. It's also not really LIDAR, as it uses LED illumination, but AMCW LIDAR is more or less the same principle. A better comparison might be laser tape measures - these often use phase modulated LIDAR rather than direct ToF. You can also buy phase shift scanning systems from people like Leica Geosystems.

In a ToF camera (at least some of them - see lock-in pixels), each pixel is sampled four times per cycle to detect the phase offset from the outgoing illumination. The SwissRanger was one of the first time of flight cameras. The reason it suffers short range is because of phase ambiguity - the lasers are modulated at around 30MHz which gives a wavelength of 10 m or so. The ambiguity distance is half this (5 m). LIDAR systems historically got round this by using multiple modulation frequencies for different distance scales.

This tech is now everywhere thanks to Microsoft buying Canesta.

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Re:How the LIDAR tech GM just bought probably works by mikeha on Tuesday October 24, 2017 @05:19PM (#15545332)

Leica Geosystems used to sell phase-based scanners. These units were actually rebadged Zoller+Frohlich scanners. But the partnership ended a few years ago when Leica introduced the Pxx series. Today the company only makes time-of-flight scanners.

source: I work at Leica Geosystems.

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