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Ouster's new digital Lidar – 128 beams, ultra-wide view

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Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#71

Post by [deleted] »

nullc wrote: post #59
entangledqubit wrote: post #37

Does anyone know whether eye safety is de facto maintained when your eye is being continuously bombarded by the 100+ scanning lasers being emitted from each of the 100 cars in the vicinity of an intersection? I'm on board with the case with a handful of lasers scanning by quickly but the energy may really start to add up in certain plausible future scenarios.

865nm too, presumably it only passes as class 1 eye-safe due to an time x power x aperture exposure calculation... I wonder how much we have to blame ITAR restrictions on >1555nm lasers for things like this not being more eye-safe on a by-wavelength basis.

[deleted]

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#72

Post by [deleted] »

entangledqubit wrote: post #37

Does anyone know whether eye safety is de facto maintained when your eye is being continuously bombarded by the 100+ scanning lasers being emitted from each of the 100 cars in the vicinity of an intersection? I'm on board with the case with a handful of lasers scanning by quickly but the energy may really start to add up in certain plausible future scenarios.

[deleted]

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#73

Post by mattkrause »

mirashii wrote: post #24
OnlineGladiator wrote: post #5

Earlier quoted context omitted.

That's sort of like asking how well cameras would work if 20 of them were looking at the same object. Lidar sensors can interfere with each other, and a certain industry-standard company is famous for having terrible problems with this issue, but there are engineering solutions to this problem. FMCW is a popular choice, and gives the benefit of providing instantaneous velocity readings. Of course, due to the Heisenbe…

> Of course, due to the Heisenberg uncertainty principle, this means you also get worse distance estimation. This isn't how the Heisenberg uncertainty principle works. For macroscopic objects, the effects are completely dwarfed by other phenomenon. Keep in mind that Planck's constant is 10^{-33} meters.

The position/momentum pair is just one (important) case of a more generalized Uncertainty Principle. There's a similar one, due to Gabor (1946), which says that you can't have perfect time-limited and band-limited information, which is presumably what the OP is referring to.

The underlying math is the same, and there's a principle of complementarity that describes other pairs of quantities that need to be traded against one another.

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#74

Post by mattkrause »

kyzyl wrote: post #67
PhaseLockk wrote: post #47

Earlier quoted context omitted.

I'm pretty sure the effect you are discussing has to do with the uncertainty relationship inherent to the Fourier Transform [0]. This is very closely related to the Heisenberg uncertainty principle, and states you cannot simultaneously constrain time and frequency, which are the values you need to measure for position and velocity, respectively. In the context of signal processing applications, I don't think the part…

So your're correct that there is a Fourier Transform analogy for the uncertainty principle, but in the context of FMCW lidars (which brought up the question of velocity vs position uncertainty), the measurement of frequency actually determines both the position and the velocity. It's actually a problem for most FMCW lidars because you just get 1-2 frequency measurements and somehow need to disentangle what the range…

It's not just an analogy--the underlying math is the same. These course notes have a nice little summary + a proof: http://www.its.caltech.edu/~matilde/GaborLocalization.pdf

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#75

Post by lmilcin »

runin2k1 wrote: post #54
toxik wrote: post #50

Earlier quoted context omitted.

IR and UV radiation can very much ruin your sight.

It doesn't matter if it is IR, UV, or visible. Only the power and duration matter. Lidar uses very short pulses and very low power and is very safe even en masse.

This is actually more complex than that.

Due to optical aberration wavelengths outside of visible range don't get focused the same way as visible light. This means that the energy is spread over larger area.

Also, both UV and IR light is absorbed in a different way. UV tends to be absorbed much faster than visible light so that little of it reaches the retina while for IR opposite is true, the eye is more translucent to IR and only a portion of it is absorbed at retina and a lot of it tends to pass through it.

What it means is that, while a source of visible light is very well focused on the retina and absorbed in very small volume of retina cells, UV and IR are spread over larger area and then large part of it is absorbed somewhere else.

Still it doesn't mean IR or UV beams aren't dangerous. It is just that you can't directly compare beams by their power.

The way I understand it the main danger is that, since people may not see the IR or UV beam very well, there might be no involuntary response to close the eye.

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#76

Post by Symmetry »

maxbaines wrote: post #68
DoofusOfDeath wrote: post #11

Anyone have a LIDAR (or similar) product suggestion? I'm getting ready to start a hobby project that involves scanning the interior surfaces of a house. Ideally the accuracy would be at least 1/16" (1.5mm), including any scan-stitching required because the sensor had to be moved around. I've seen a few promising products, but none stands out as a perfect match.

https://store.intelrealsense.com/buy-intel-realsense-lidar-c...

You'll need to do a bunch of averaging to get that sort of precision out of one of those, they tend to have an error proportional to distance that's generally a lot higher than the OP's 1.5mm target. But I agree that that's the right starting place.

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#77

Post by OnlineGladiator »

mattkrause wrote: post #74
kyzyl wrote: post #67

Earlier quoted context omitted.

So your're correct that there is a Fourier Transform analogy for the uncertainty principle, but in the context of FMCW lidars (which brought up the question of velocity vs position uncertainty), the measurement of frequency actually determines both the position and the velocity. It's actually a problem for most FMCW lidars because you just get 1-2 frequency measurements and somehow need to disentangle what the range…

It's not just an analogy--the underlying math is the same. These course notes have a nice little summary + a proof: http://www.its.caltech.edu/~matilde/GaborLocalization.pdf

Thank you for this! This is exactly what I was looking for.

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#78

Post by Animats »

jiofih wrote: post #49
kensai wrote: post #45

Am surprised no one yet cited Elon saying "this is fool's errand" because of price, complexity, etc. I think LIDAR will improve significantly the safety of vehicles (autonomous or not) because it can definitely see better and deeper, even in damning weather conditions (rain, fog, haze). Alas, the price of these devices has to come down at least one order of magnitude. Maybe even two. Still, I am really thankful that…

As far as I’m aware LIDAR cannot see though fog, as the light is dispersed, and even light rain might reduce range significantly. Tesla cars have radar which can see through any weather condition and detect transparent surfaces, invisible to LIDAR.

There are LIDAR units that can see through fog. If you get data from multiple returns, not just the first, you can tell the difference between fog, rain, and solid surfaces. "First and last" is a big win. A solid obstacle in fog looks like a repeatable "last" (furthest) return, while rain and fog look like random disconnected points.

I think Google's own unit has 8 stored returns.

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#79

Post by Reelin »

nullc wrote: post #59
entangledqubit wrote: post #37

Does anyone know whether eye safety is de facto maintained when your eye is being continuously bombarded by the 100+ scanning lasers being emitted from each of the 100 cars in the vicinity of an intersection? I'm on board with the case with a handful of lasers scanning by quickly but the energy may really start to add up in certain plausible future scenarios.

865nm too, presumably it only passes as class 1 eye-safe due to an time x power x aperture exposure calculation... I wonder how much we have to blame ITAR restrictions on >1555nm lasers for things like this not being more eye-safe on a by-wavelength basis.

> I wonder how much we have to blame ITAR restrictions on >1555nm lasers ...

I tried looking up information about this (restriction details, otherwise feasible uses beyond that wavelength, etc) but it's hard for an outsider to quickly make sense of. Any chance you could elaborate?

Re: Ouster's new digital Lidar – 128 beams, ultra-wide view

#80

Post by mattkrause »

OnlineGladiator wrote: post #77
mattkrause wrote: post #74

Earlier quoted context omitted.

It's not just an analogy--the underlying math is the same. These course notes have a nice little summary + a proof: http://www.its.caltech.edu/~matilde/GaborLocalization.pdf

Thank you for this! This is exactly what I was looking for.

It seems to be an extract from "Foundations of Field Computation" by Bruce MacLennan, if you want to read the whole thing: http://web.eecs.utk.edu/~bmaclenn/FFC.pdf

He and Dr. Marcolli have a bunch of interesting stuff on their websites if you like this sort of stuff.

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