[yaantc]

Disclaimer: I'm not involved in AV, but I have a telecommunication background that let me do some (hopefully) not too stupid guesses on how a LIDAR can behave here. If some expert in the field can give more authoritative feedback that's be even better.

Looking at [1], a typical LIDAR uses 10 ns pulses, at 140 kHz for pulse rate. So one LIDAR uses only 0.14% of air time. A LIDAR is also a rotating device, looking at reflections only from a narrow angle at any give time (how large this angle? TBD). That also reduces the risk of looking at another reflection in the right direction at the right time. Raw collisions should be rare, even in a crowded environment (you're 1000s of cars is extreme, 100s will already be very crowded).

Then if it's using the usual techniques for signal detection, each pulse is encoded with a randomized pattern, so that a LIDAR can recognize its own pulses reflections using correlation. So a given LIDAR will only consider reflections using the right coded sequence. That will further reduce the risk of wrong interpretation, depending on how many bits in the synchronization sequence.

Lastly, at 140 kHz you can do quite a lot of filtering and still have a fast update. If by extraordinary bad luck another reflection comes from the right direction in the right time window with the same sync pattern, this would create an odd input that's unlikely to fit with one's own echo pattern, so could be filtered out. And it's not likely to last long considering all that has to align.

That's my armchair analysis based on a quick search and a single set of slides ;) But it's enough to see that interference is not likely to be a problem. And I would expect this question to have been considered by AV LIDAR experts in much more detail.

[1] http://web.pdx.edu/~jduh/courses/Archive/geog481w07/Students...

[davrosthedalek]

I think the problem is more the analog side: If your sensor is saturated by too much light, it might not be able to pick up on your signal anymore. Direct LOS to another high-powered source is probably a lot brighter than what LIDAR normally detects. Then, all the reduction from sync pattern etc don't apply, and the sensor might be blinded considerably longer than the actual signal length if driven to saturation.

[yaantc]

Possibly yes. I was assuming an RF-like behavior where there is indeed saturation of the A/D converter but the blinding doesn't last more than the interfering signal (or negligibly so). But these are for timescales in multiple of us not ns. For ns level time scales maybe it's a bit different, but if it's not too different the low air time usage would avoid problems here too. The blinding pulse would mean an angle between two circles in space (angle from the interfering direction, circles corresponding to distances associated to the blinding pulse start/stop with respect to the last interfered LIDAR own previous pulse transmission) would loose any echo and become blind. With the vehicles moving such a "lost patch" would not be fixed either, and interpolation based on past and surrounding data is possible.