How Multi-Beam Flash Lidar Works
ouster.io
ouster.io
https://www.ouster.io/blog-posts/2018/8/31/the-camera-is-in-...
Oh geeze. I’ve never even considered the fact that there’s a possibility looking at these cars might cause vision issues!
Although probably not practical to worry about in reality, there is some probability that all 200 cars you could see shine their lasers directly into your eyes at the exact same time. There is some probability of accidentally receiving a momentary higher than safe combined pulse from multiple vehicles.
Would that actually matter? Each of those would be coming from a different direction, and be focused on a different spot on the retina. No particular spot on the retina would receive an unsafe exposure.
Then there are wavelength that aren’t focuse by the eyes, the only way to get hurt with these if the energy reaches weapon-grade levels.
Perhaps a fisheye mirror on a big truck.
https://www.microsoft.com/en-us/research/wp-content/uploads/...
I wonder if Ouster is susceptible to this. There's no mention of it, but I imagine it will be a bigger problem as they add more lines of resolution.
Through my work (shameless plug: www.dotproduct3d.com) I've assessed a fair number of "Time of Flight" 3D sensors (which also use flashes of IR light -- but aren't really time-of-flight but that's another story) and, while generally pretty cool, all of them so far have suffered more or less severe multi-path effects. Which is why stereo / structured light or single-point LiDAR are still better for a lot of use cases. I can't wait for these MPI problems to be finally solved.
So, I don't think it will be a problem for them but it is something they need to consider when designing their DSP.
So you hit a chrome bumper or maybe a glossy black point. The later pulses could arrive at a much higher amplitude.
Hard to explain in a few words, but the principle of the lock-in amplifier is a good place to start.
I don't see how there is no threshold.
* it only takes 1 microsecond to make a ranging measurement up to 150 m, so your detector is on for a short time
* lasers only illuminate a small spot, and the detector is also looking at a similarly small spot, so it is unlikely for two lidars to point in the same spot
Now, even if it does interfere, you may see a stream of random points pointed towards the interference source. This may happen if, say, you point a lidar directly at the sun, or if you have multiple lidars mounted on the same vehicle. Such random points are easily rejected as outliers and do not affect the vast majority of the scene. Most self driving cars (I hope) should have outlier rejection schemes that deal with outliers caused by this and other sources, such as snow, smoke, and so on.
For this reason we see many self driving cars bristling with a bunch of lidars next to each other with no problems. For example the Cruise/GM ones have five Velodynes on top.
Active systems like radars have a "burn-through" short range - at some short distance, the sensing system overpowers a jammer. So if you're seeing junk at distance, but good signal at short range, you know you're being jammed and have to slow down.
Active jamming is not that effective against things that receive directionally, as people using car "radar jammers" near military bases sometimes discover. They show up on military radars as hostile targets. That's even filtering down to police LIDAR guns.
Just another of the many edgecases to figure out before autonomous vehicles become mainstream.
https://www.theverge.com/2017/10/9/16448306/gm-cruise-strobe...
(Disclaimer, I work for GM, but not on any of this)
When they talk about rejecting solar interference I'd presume, but can't be sure, that whatever they do would also help a lot with lidar on lidar interference.
It's unclear if this product works in the time-domain or in the frequency domain...
If you want more details, Image Sensors World [1] has coverage with more details and links to two patents.
> It's unclear if this product works in the time-domain
It is a pulsed time of flight direct detection lidar, not a modulated continuous wave lidar.
[1] http://image-sensors-world.blogspot.com/2018/11/ouster-discu...
Longer range lidars work in the time domain. The SPAD detectors used by Ouster create a pulse when a single photon is detected and so you're measuring the time of flight of the photon being emitted by the vscel and then being detected by the SPAD array.
The 2nd reason why 850nm sources are not a good choice are VCSELs themselves. VCSELs are low power devices and always will be due to the narrow current aperture in their construction, you simply can’t send much current through it because even at low currents the current density is already very high. The 850nm wavelength is also limited in how much output power you can get and still have an eye safe device. Additionally, VCSELs do not work well at high temperatures. Their LIV curve bends over meaning that the combination of reduced slope efficiency and self heating of the junction cause the output power to decrease as you increase current beyond a certain point.
Lastly, VCSELs are relatively noisy devices. VCSELs are not single spatial mode devices and there is mode partition noise caused by the sloshing around of power between the various modes. When combined with RIN, this places an Upper bound on the SNR of the system. Finally, if you are already doing photon counting, you’re pretty much at the limit of this tech already.
To my mind, longer wavelength tech is more promising because it can use higher powers and still be eye safe, has better immunity to scattering in various atmospheric conditions which gives it longer range. Longer wavelengths can leverage technologies like silicon photonics to produce more advanced detectors (coherent detectors which will be more sensitive and improve range). Generally the lasers at these wavelengths are less noisy as they’ve been optimized for decades for use in long distance communication.
Out of curiosity, this artifact with the van in the below picture common with flash lidars? https://imgur.com/a/OI4UZt9
I am guessing the van is painted with something that strongly absorbs your laser frequencies (black paint). Is this something that your lidar is working to get around?
Part of that is probably just the resolution you're seeing on the point cloud (i.e. if it were up on a 4k OLED you'd see it a lot better than you do on that screenshot) and part of it is definitely that lidar as a broad category has a comparatively harder time with this type of surface than other surfaces. That's why it's super important when comparing lidar units to see what reflectivity they're quoting. 80% vs 10% reflectivity typically reduces range significantly.
PS if you want to get in touch directly, my email is derek.frome at ouster dot io
That sort of behavior might be made illegal (if it isn't already), but I'd be curious to know if self-driving systems have ways of dealing with it, or if they just shut down
California Penal Code Section 417.27
(c) No person shall direct the beam from a laser pointer directly or indirectly into the eye or eyes of another person or into a moving vehicle with the intent to harass or annoy the other person or the occupants of the moving vehicle.
There is already established case law around this, where larger hobby lasers intended for popping balloons and theatrical lasers are exempt.
You could build a large array of laser emitters intended to obstruct self driving vehicles (say you wanted to create a fake wall to prevent a car from driving the wrong way), and safely ignore these laws.
No the law in question defines the term, it doesn't defer to the FDA; Cal. Penal Code § 417.27(f): «As used in this section, “laser pointer” has the same meaning as set forth in subdivision (c) of Section 417.25»
Cal. Penal Code § 417.25(c): «As used in this section, “laser pointer” means any hand held laser beam device or demonstration laser product that emits a single point of light amplified by the stimulated emission of radiation that is visible to the human eye.»
Any device that emits more than a single point of light, or is not hand held is not covered.
A powerful commercial laser can easily damage the CCD but again it’s not an issue drivers can be blinded by lasers already and are constantly blinded by other things like high beams and highway camera flashes the closest I came to being night blinded twice is when a red light camera was triggered on an intersection in both cases I got honked for not seeing the light turn green because I couldn’t see shit for like 5 seconds.
Not every system needs to be resilient to adversaries we don’t drive in armored cars or have active protection systems against ATGMs put on our SUVs.
If an asshole wants to jam cars they’ll be able to they’ll get caught and go to jail that’s more than enough for these systems to be reliable.
If you think about it we already have systems which we rely on everyday that can be jammed with $50 worth of gear like cell phones and GPS these aren’t adversary resistant but we don’t cry about it because it’s not an issue.
A high speed collision is not comparable.
A human has tons of options being blinded by a laser. Obscuring it for one.
Also the ease of which an attack can be performed is of immense importance. It is quite the barrier to pick up a rifle and start to shoot at vehicles. A handheld laser is something people do just for shits and giggles.
This is something that helicopter pilots are quite aware of.
Really? get a 500mw laser into your eyes at highway speeds and I can guarantee you it's a crash, the pain and the shock from being blinded you aren't going to react rationally you going to twitch uncontrollably.
GPS and Cellphones are constantly used for life critical services and can be jammed easily but no one is doing that.
>This is something that helicopter pilots are quite aware of.
Helicopter pilots being blinded by lasers isn't the same thing as drivers at those altitudes the laser beam has spread sufficiently to while remain dangerous at least not being painful.
Helicopters also often come with some sort of auto hover mode these days and you can maintain attitude without sight landing would be hard but you aren't at risk of crashing into anything immediately.
Yes.
> GPS and Cellphones are constantly used for life critical services and can be jammed easily but no one is doing that.
They are being jammed. Not as often as idiots playing with lasers though. But for silly things like "my employer put a tracking device on my truck, if I jam signals I can do whatever I want".
> Helicopter pilots being blinded by lasers isn't the same thing as drivers at those altitudes the laser beam has spread sufficiently to while remain dangerous at least not being painful.
Can apparently break havoc on sensors though. And this happens over densely populated areas.
> Helicopters also often come with some sort of auto hover mode these days and you can maintain attitude without sight landing would be hard but you aren't at risk of crashing into anything immediately.
Good luck doing that downtown.
If hundreds of cars will have them, your eyes will be scanned multiple times per day.
Any laser product generally has to be tested to IEC60825 to check which category it fits within, under the safety rules of the jurisdiction (e.g. CE for EU, FDA for USA). This LIDAR system would have to pass that too, and it should be reasonably easy for them to check if it would when developing it.
1) Does it offer the eye models themselves or only some results of the eye models? If it is only based on eye models, where can I learn more about the eye models/empirical data themselves?
2) Does IEC60825 only pertain to laser safety, or does it also treat LED safety?
The Ouster OS-1 in the article, as well as all other automotive lidars that I know of, are class 1 laser eye-safe, meaning that it is safe even if you put your eye right up to it for hours.
The power also decreases dramatically once you get far away from it, since the laser beams spend most of their time pointed in different directions, and the collimation is not perfect.
Besides, infrared security cameras put out just as much, if not more 850 nm - 940 nm light.
I'm a bit surprised by that since IIRC 850 nm can go through the water in your eye to reach your retina but won't trigger a blink reflex. So it has to be pretty low power to get that rating.