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How Multi-Beam Flash Lidar Works
- Animats 8y agoNice. Not really here yet, but the semiconductor physics sounds promising. The device they're actually selling is yet another spinning scanner, not a true flash unit.
- Judgmentality 8y agoWhat are your thoughts on Geiger LIDAR, ie Princeton Lightwave (which was acquired by Ford/Argo)?
- deepnotderp 8y agoPrinceton lightwave is also reportedly doing scanning flash even with 1550nm GmAPDs. Note that spads in InGaAs have much higher dark count rates (i think due to poorer crystal growth technology?)
- DoctorOetker 8y agoSPADs (single photon avalanche photodiodes) are APD's operated in Geiger mode...
- dllu 8y agoIt's often easier to make a small chip and spin it around on a rotating platform than to make a big chip. For a similar reason, rotating line cameras are a thing for panoramic imaging [1]. As the technology matures and become cheaper, we will see more solid state technology, just as bundles of regular area scan cameras with fisheye lenses have displaced rotating line cameras. [1] https://en.wikipedia.org/wiki/Rotating_line_camera https://en.wikipedia.org/wiki/Rotating_line_camera
- amelius 8y agoWhat happens when multiple lidar devices start shooting laser beams at a scene? Will there be interference?
- Symmetry 8y agoI've never had a problem with a bunch of robots in the same room all using horizontal planar lidars. Mostly due to low duty cycles, I suppose, but no sensor is perfect and you've got to have some sort of noise rejection in any event. 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.
- mtreiber 8y agoThe interference will most likely show up as noise. Its SPAD detectors have high noise compared to APD so the increased noise due to interference with other lidars would be minimal.
- DoctorOetker 8y agothe article is a bit light on real details, but all the affordable LIDAR technology I have seen used Linear-Feedback Shift Registers, such that different devices operating at the same frequency are still on different channels. It's unclear if this product works in the time-domain or in the frequency domain...
- dllu 8y ago> light on real details 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-discusses-its-lidar-principles.html http://image-sensors-world.blogspot.com/2018/11/ouster-discu...
- DoctorOetker 8y agothanks, that is helpful!
- mtreiber 8y agoShorter range lidars (<10m) tend to work in the frequency domain because you can get pretty good ranging accuracy. 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.
- bobbygoodlatte 8y agoI'm curious how these systems would function against a malicious entity. For example, if someone flooded the sensor with laser light. 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
- deepnotderp 8y agoThey could be using coding techniques like a Barker code or something
- dogma1138 8y agoHow do drivers currently handle things if someone blinds them with a laser?
- choot 8y agoI think dynamic patterns can be added to laser beams (similar to what cryptography), which randomly change that will make flooding difficult if not impossible.
- dogma1138 8y agoThose patterns and various frequency shifts are often used to prevent secondary reflections and to be able to operate in a saturated environment. 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.
- 21 8y agoHow dangerous are these lasers? If hundreds of cars will have them, your eyes will be scanned multiple times per day.
- dllu 8y agoNot very dangerous. 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.
- Symmetry 8y ago"lasers we use are well under the eye safety limit and have been certified as Class 1 eye-safe lasers by third party labs." 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.
- dllu 8y ago905 nm can also go through the water in your eye (the eye safety limit for 905 nm is maybe 2 times higher than for 850 nm), but Velodyne and many other lidar companies have been using 905 nm for years with no problems. The 2x higher sensitivity of silicon CMOS detectors to 850 nm in comparison to 905 nm makes up for the lower power.
- deleted 8y ago[deleted]
- snops 8y agoLaser safety is a well known issue, IEC60825 offers mathematical models to calculate the safety category (e.g class 1/2) of a laser device, which are based on physics models of the eye from first principles and empirical data. There is nothing particularly special about LIDAR lasers that makes these models not valid as far as I know. Generally, there is a tradeoff between exposure time and intensity, so LIDAR systems have redundant hardware methods to ensure the pulse time is not exceeded. 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.
- jpm_sd 8y agoThis is a pretty incredible achievement. Be sure to follow the #3 "High quality ambient imagery" link too, if you haven't seen it before: https://www.ouster.io/blog-posts/2018/8/31/the-camera-is-in-the-lidar https://www.ouster.io/blog-posts/2018/8/31/the-camera-is-in-...
- dllu 8y agoRelevant HN discussion about that post: https://news.ycombinator.com/item?id=17896942 https://news.ycombinator.com/item?id=17896942
- dev_dull 8y ago> And since we’re asked about it occasionally, the lasers we use are well under the eye safety limit and have been certified as Class 1 eye-safe lasers by third party labs. Oh geeze. I’ve never even considered the fact that there’s a possibility looking at these cars might cause vision issues!
- edoo 8y agoIt might be fun to come up with the probability of a worse case scenario, like parked on the crest of a hill in bumper to bumper traffic. 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.
- tzs 8y ago> 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.
- DenisM 8y agoThere are wavelength that are invisible to human eye, those are pretty safe unless the energy levels are high enough to burn a hole in your retina. 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.
- salty_biscuits 8y agoActually, some non visible wavelengths are dangerous because they don't make you blink.
- hobolord 8y agosuper neat stuff, I visited their offices recently and was really impressed by what they were doing. From what I can tell, everything was done in house
- randyrand 8y agoA big accuracy problem with flash approaches is multi path interference. https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/chr_mpi_cvpr_15.pdf 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.
- rsp1984 8y agoThis. 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.
- randyrand 8y agoIt should be a smaller problem than with the Kinect. The Kinect is not true time of flight like you said, whereas ouster is. If you know when photons actually arrived you know the first light pulse you receive is the one you care about, and the later longer paths you can ignore. The Kinect conflates these. So, I don't think it will be a problem for them but it is something they need to consider when designing their DSP.
- nomel 8y agoThis makes me wonder how any of these systems handle the reflective surfaces of cars. So you hit a chrome bumper or maybe a glossy black point. The later pulses could arrive at a much higher amplitude.
- CamperBob2 8y agoThey don't care about the amplitude, just the timing.
- karmicthreat 8y agoReally wish 3d lidar costs would come down. Everyone is designing for car performance and price points it seems. I have a ton of applications I could throw one of these on at 1k$.
- derek_frome 8y agoCosts are definitely coming down. The OS-1 sensor is 1/6 the price of Velodyne's 64 channel sensor. Ouster has been pretty explicit about our intent to keep driving down prices, and we have significant structural advantages covered in the article that will allow us to do so in the coming months and years.
- karmicthreat 8y agoYea, my space is mostly industrial so its a more cost sensitive area. Out of curiosity, this artifact with the van in the below picture common with flash lidars? https://imgur.com/a/OI4UZt9 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?
- derek_frome 8y agoYeah - we're actually exploring how to address the industrial market more effectively right now. There's a lot of interest in moving from 2D to 3D lidar. 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
- bmc7505 8y agoIf you don't need 3D, 2D LIDAR is pretty cheap right now: https://www.adafruit.com/product/4010 https://www.adafruit.com/product/4010
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- exabrial 8y agoIs something like phased array lidar useful? The wavelength is so small I could see how the interference patterns might not be useful
- mmmBacon 8y agoI don’t think 850nm is a good choice for LIDAR for several reasons. Firstly, the article talks about absorption but that’s not the only phenomenon that they need to be concerned about. The other is scattering and 850nm will scatter from particulate matter in the air (like water vapor in fog) and suffer reduced range. 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.
- rsp1984 8y agoAs far as I know detection SNR goes way down with longer wavelengths. I think luminartech.com claims that they have specific IP to make this work, but apparently it's a hard problem, otherwise everybody would be doing it already.