50 ms·

Open Source Time-of-Flight DIY Lidar

181 points by iliasam 7y ago

iliasam 7y ago
I'm surprised that there is absolutely no comments. Does that mean that this project is really not interesting?
- beagle3 7y ago
  I think it's very interesting, but I suspect too few people have anything to contribute. I know I don't have anything smart to say about this specific subject, and I usually try to follow the old german saying "Selig sind die, sie nicht zu sagen haben und trotzdem schweigen" (hope I got it right - I don't actually speak german), which means "Blessed be those, who have nothing to say and nevertheless remain silent..."
  - iliasam 7y ago
    Discussion about my previous project: https://news.ycombinator.com/item?id=16756901 https://news.ycombinator.com/item?id=16756901 was much bigger in comparison with this project - this is surprising me.
    - AYBABTME 7y ago
      Probably just timing. I find it pretty cool, but I have nothing to say. I'm impressed with the work and would like to do the same myself, but I'm not sure immediately where I'd use this and when I'll have time. I've put it in the section of my brain where I keep things for "when I'll need it, go look this crazy ambitious project". If I can provide more feedback, while looking at your project, I had the following thoughts: - This is super impressive. - I'm thankful that people spend time making technology opensource. - I'm sure this will grow over time and more "complex" technology will become open this way. - I'm curious in which context the author decided to dedicate that much time to this cause (probably in academia? or someone with access to a lab and a lot of experience in all the fields involved in this project).
      - iliasam 7y ago
        Thank you for reply!
  - atoav 7y ago
    German native speaker here, you just got two letters wrong: Selig sind die, die nichts zu sagen haben und trotzdem schweigen
    - beagle3 7y ago
      Thanks. I was under the impression that it a well known saying when I first heard it, but google doesn't come up with many hits for me (and some with wrong spelling) - likely because of my google bubble / history. Is this a common/well-known saying?
      - atoav 7y ago
        I heard it before, but it is not very commonly used. It is a bit more like a literaric aphorism than something people would use in any everyday conversation.
- prashnts 7y ago
  Honestly, I didn't open comments and simply added it to my "come back later" list, because it looks very very interesting to me, and would need to read it in detail. Great work, btw!
- neumann 7y ago
  On the contrary - it's super interesting! I definitely want to come back to it and study this and thinking of projects I can use it on for fun and no profit, but also know that though I have analysed lidar data, I have very superficial understanding of the technical details of implementation. For me this is not just great as a cheap lidar implementation but a great working example to learn on.
- gruturo 7y ago
  I find it super interesting - but it's beyond my capability to contribute so I keep quiet for the moment. I imagine many people would be doing the same.
- jsjohnst 7y ago
  Thank you so much for releasing this. I have several personal projects were this can be useful. One variation I’m thinking about and want your opinion on. I’m building a circuit that VERY precisely (think <1ms accuracy) marks the start and end of when a high speed object passes the field of view. The exact scenario is a bit hard to describe if you aren’t familiar with the subject area, but an analogy that works well is imagine having two sets of cones laid out on the ground with 10 meters between the groups. Then imagine a car doing 100mph between the two sets of cones. What I need to be able to answer is: - did the car go between the first set of two cones? - what’s the exact time it went between them? - did the car go between the second set of two cones? - what’s the precise time it went through the second set? - what’s the calculated speed between the two sets? The real scenario isn’t touching the ground, so anything pressure sensitive doesn’t work. I’ve been currently experimenting with using lasers on both the start and end gates and an fpga doing the calculations, but I’d love if I could do this with a single laser setup using a scanning setup like yours. Can you speak to how hard it would be to use something like this to precisely (1ms or better accuracy) measure a low flying object between a starting and ending point?
  - OnACoffeeBreak 7y ago
    I am not the OP. Seems like you should be able to set up two break beam detectors: one per set of cones. Process detector output into digital form where you get a pulse when the detector is broken. Connect them to a microcontroller input and use a fast counter in input capture/compare mode to measure time between pulses. A counter running at 1 MHz (1 us) should do.
dchichkov 7y ago
The original article (in Russian) is very well written. And the author feels like a true "full stack" engineer: high frequency and power electronics, optics, mechanical engineering, micro-controller software development, real time, simultaneous localization and mapping, visualization.
- ragebol 7y ago
  These are the folks that give me impostor syndrome. Given enough time and a project like this, I think I can learn all of that stuff.
  - carlmr 7y ago
    The thing is, with Google at your fingertips, you can build almost anything. You don't need to deep dive on all these technologies, but you can probably gather just enough information in a short time. However it still takes a lot of effort and most of your free time. You have to be extremely driven to complete such a complex project.
    - iliasam 7y ago
      In fact there is still many kinds of information that could not be found in Google.
    - myself248 7y ago
      Free time in large chunks, was the revelation for me. I took a serious "staycation" back in December, and wrote about it here: https://www.reddit.com/r/Coronavirus/comments/fgvbsv/staythefuckhome_a_movement_to_stop_the_covid19/fk8xemy/ https://www.reddit.com/r/Coronavirus/comments/fgvbsv/staythe... During those few weeks, I made what seems like a year worth of progress on several projects. Being able to dive in and focus, for hours at a time without worrying that I had other stuff I should be doing, made all the difference in the world. Rearranging your week to have one "no-chores no-email" evening, when you just use a single large block of time to immerse yourself in a leisure activity, is worth a try.
    - 7y ago
beagle3 7y ago
Actually I do have a question - how safe is this for eyes (human or animal?) and what changes are needed to make it safer? How about measuring through translucent or transparent surfaces? Should work as is if there is no reflection (e.g. measurement at Brewster’s angle for this wavelength) but is it possible to TOF multiple reflections from? Or multiple depth slices (e.g. by gating TOF to specific depth ranges? 1ns=~1ft=~30cm
- dllu 7y ago
  He discusses this both in his very detailed Russian post as well as on GitHub: https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety
- iliasam 7y ago
  As it was answered, you could read about safety here: https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety Measuring through translucent or transparent surfaces is theoretically possible (TDC is supporting multiple measurements), but received pulse width is too high now - it could be > 30ns after amplifier.
  - beagle3 7y ago
    Thanks! Really an awesome project and great documentation.
osamagirl69 7y ago
This is a very neat project, I really wish I could read Russian to understand some of the details in his writeup. The overall architecture is pretty standard for a LIDAR setup. For the source they are using an osram SPL PL90_3 laser diode which provides 75W peak output at 900nm, with pulse duration roughly 10ns and costs $10. For the detector they are using a MTAPD-07-013 avalanche photodiode, which has a quantum efficiency of about 80% and an internal avalanche gain of 100 and 0.6ns rise time. Also costs about $10. For the time measurement they are using a TDC-GP21 time to digital converter with 22ps resolution, although the author has it configured for 90ps counts. Costs a bit over $5. It is really a testament to the amount of development work that has gone into the lidar and related field, that for under $100 you can build a full lidar system out of parts from digikey including custom pcb's and scan mirror. When I was in grad school we paid $7500 for our avalanche photodiode, $25k for our pulsed laser, and used a $50k oscilloscope to read it out.
- iliasam 7y ago
  Here is a link to the video: https://youtu.be/lTPH_Xa9yCk https://youtu.be/lTPH_Xa9yCk with short Lidar description. What kind of details do you want to know? Why did you write "they are using"? Thre was no team, it's my own project.
  - regularfry 7y ago
    "They" can be singular.
    - iliasam 7y ago
      Thanks, I have never heard about it.
      - regularfry 7y ago
        Not a problem. Every so often this otherwise unremarkable grammatical point becomes somewhat contentious, but it's easy to see how it can be confusing if English isn't your first language. There's more here: http://itre.cis.upenn.edu/~myl/languagelog/archives/002748.html http://itre.cis.upenn.edu/~myl/languagelog/archives/002748.h...
salty_biscuits 7y ago
This is fantastic! I want to make one. Is it possible to get a cheap polygonal mirror? Then you can get more scans per revolution.
- iliasam 7y ago
  I think that it is possible to make own polygonal mirror (cut polygonal mirror holder at CNC, attach flat mirrors and balance it). Also it may be found in stationary barcode reader. But you will lose field of view with polygonal mirror.

181 points by iliasam 7y ago

iliasam 7y ago

I'm surprised that there is absolutely no comments. Does that mean that this project is really not interesting?

beagle3 7y ago
I think it's very interesting, but I suspect too few people have anything to contribute. I know I don't have anything smart to say about this specific subject, and I usually try to follow the old german saying "Selig sind die, sie nicht zu sagen haben und trotzdem schweigen" (hope I got it right - I don't actually speak german), which means "Blessed be those, who have nothing to say and nevertheless remain silent..."
- iliasam 7y ago
  Discussion about my previous project: https://news.ycombinator.com/item?id=16756901 https://news.ycombinator.com/item?id=16756901 was much bigger in comparison with this project - this is surprising me.
  - AYBABTME 7y ago
    Probably just timing. I find it pretty cool, but I have nothing to say. I'm impressed with the work and would like to do the same myself, but I'm not sure immediately where I'd use this and when I'll have time. I've put it in the section of my brain where I keep things for "when I'll need it, go look this crazy ambitious project". If I can provide more feedback, while looking at your project, I had the following thoughts: - This is super impressive. - I'm thankful that people spend time making technology opensource. - I'm sure this will grow over time and more "complex" technology will become open this way. - I'm curious in which context the author decided to dedicate that much time to this cause (probably in academia? or someone with access to a lab and a lot of experience in all the fields involved in this project).
    - iliasam 7y ago
      Thank you for reply!
- atoav 7y ago
  German native speaker here, you just got two letters wrong: Selig sind die, die nichts zu sagen haben und trotzdem schweigen
  - beagle3 7y ago
    Thanks. I was under the impression that it a well known saying when I first heard it, but google doesn't come up with many hits for me (and some with wrong spelling) - likely because of my google bubble / history. Is this a common/well-known saying?
    - atoav 7y ago
      I heard it before, but it is not very commonly used. It is a bit more like a literaric aphorism than something people would use in any everyday conversation.
prashnts 7y ago
Honestly, I didn't open comments and simply added it to my "come back later" list, because it looks very very interesting to me, and would need to read it in detail. Great work, btw!
neumann 7y ago
On the contrary - it's super interesting! I definitely want to come back to it and study this and thinking of projects I can use it on for fun and no profit, but also know that though I have analysed lidar data, I have very superficial understanding of the technical details of implementation. For me this is not just great as a cheap lidar implementation but a great working example to learn on.
gruturo 7y ago
I find it super interesting - but it's beyond my capability to contribute so I keep quiet for the moment. I imagine many people would be doing the same.
jsjohnst 7y ago
Thank you so much for releasing this. I have several personal projects were this can be useful. One variation I’m thinking about and want your opinion on. I’m building a circuit that VERY precisely (think <1ms accuracy) marks the start and end of when a high speed object passes the field of view. The exact scenario is a bit hard to describe if you aren’t familiar with the subject area, but an analogy that works well is imagine having two sets of cones laid out on the ground with 10 meters between the groups. Then imagine a car doing 100mph between the two sets of cones. What I need to be able to answer is: - did the car go between the first set of two cones? - what’s the exact time it went between them? - did the car go between the second set of two cones? - what’s the precise time it went through the second set? - what’s the calculated speed between the two sets? The real scenario isn’t touching the ground, so anything pressure sensitive doesn’t work. I’ve been currently experimenting with using lasers on both the start and end gates and an fpga doing the calculations, but I’d love if I could do this with a single laser setup using a scanning setup like yours. Can you speak to how hard it would be to use something like this to precisely (1ms or better accuracy) measure a low flying object between a starting and ending point?
- OnACoffeeBreak 7y ago
  I am not the OP. Seems like you should be able to set up two break beam detectors: one per set of cones. Process detector output into digital form where you get a pulse when the detector is broken. Connect them to a microcontroller input and use a fast counter in input capture/compare mode to measure time between pulses. A counter running at 1 MHz (1 us) should do.

dchichkov 7y ago

The original article (in Russian) is very well written. And the author feels like a true "full stack" engineer: high frequency and power electronics, optics, mechanical engineering, micro-controller software development, real time, simultaneous localization and mapping, visualization.

ragebol 7y ago
These are the folks that give me impostor syndrome. Given enough time and a project like this, I think I can learn all of that stuff.
- carlmr 7y ago
  The thing is, with Google at your fingertips, you can build almost anything. You don't need to deep dive on all these technologies, but you can probably gather just enough information in a short time. However it still takes a lot of effort and most of your free time. You have to be extremely driven to complete such a complex project.
  - iliasam 7y ago
    In fact there is still many kinds of information that could not be found in Google.
  - myself248 7y ago
    Free time in large chunks, was the revelation for me. I took a serious "staycation" back in December, and wrote about it here: https://www.reddit.com/r/Coronavirus/comments/fgvbsv/staythefuckhome_a_movement_to_stop_the_covid19/fk8xemy/ https://www.reddit.com/r/Coronavirus/comments/fgvbsv/staythe... During those few weeks, I made what seems like a year worth of progress on several projects. Being able to dive in and focus, for hours at a time without worrying that I had other stuff I should be doing, made all the difference in the world. Rearranging your week to have one "no-chores no-email" evening, when you just use a single large block of time to immerse yourself in a leisure activity, is worth a try.
  - 7y ago

beagle3 7y ago

Actually I do have a question - how safe is this for eyes (human or animal?) and what changes are needed to make it safer? How about measuring through translucent or transparent surfaces? Should work as is if there is no reflection (e.g. measurement at Brewster’s angle for this wavelength) but is it possible to TOF multiple reflections from? Or multiple depth slices (e.g. by gating TOF to specific depth ranges? 1ns=~1ft=~30cm

dllu 7y ago
He discusses this both in his very detailed Russian post as well as on GitHub: https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety
iliasam 7y ago
As it was answered, you could read about safety here: https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety https://github.com/iliasam/OpenTOFLidar/wiki/Laser-Safety Measuring through translucent or transparent surfaces is theoretically possible (TDC is supporting multiple measurements), but received pulse width is too high now - it could be > 30ns after amplifier.
- beagle3 7y ago
  Thanks! Really an awesome project and great documentation.

osamagirl69 7y ago

This is a very neat project, I really wish I could read Russian to understand some of the details in his writeup. The overall architecture is pretty standard for a LIDAR setup. For the source they are using an osram SPL PL90_3 laser diode which provides 75W peak output at 900nm, with pulse duration roughly 10ns and costs $10. For the detector they are using a MTAPD-07-013 avalanche photodiode, which has a quantum efficiency of about 80% and an internal avalanche gain of 100 and 0.6ns rise time. Also costs about $10. For the time measurement they are using a TDC-GP21 time to digital converter with 22ps resolution, although the author has it configured for 90ps counts. Costs a bit over $5. It is really a testament to the amount of development work that has gone into the lidar and related field, that for under $100 you can build a full lidar system out of parts from digikey including custom pcb's and scan mirror. When I was in grad school we paid $7500 for our avalanche photodiode, $25k for our pulsed laser, and used a $50k oscilloscope to read it out.

iliasam 7y ago
Here is a link to the video: https://youtu.be/lTPH_Xa9yCk https://youtu.be/lTPH_Xa9yCk with short Lidar description. What kind of details do you want to know? Why did you write "they are using"? Thre was no team, it's my own project.
- regularfry 7y ago
  "They" can be singular.
  - iliasam 7y ago
    Thanks, I have never heard about it.
    - regularfry 7y ago
      Not a problem. Every so often this otherwise unremarkable grammatical point becomes somewhat contentious, but it's easy to see how it can be confusing if English isn't your first language. There's more here: http://itre.cis.upenn.edu/~myl/languagelog/archives/002748.html http://itre.cis.upenn.edu/~myl/languagelog/archives/002748.h...

salty_biscuits 7y ago

This is fantastic! I want to make one. Is it possible to get a cheap polygonal mirror? Then you can get more scans per revolution.

iliasam 7y ago
I think that it is possible to make own polygonal mirror (cut polygonal mirror holder at CNC, attach flat mirrors and balance it). Also it may be found in stationary barcode reader. But you will lose field of view with polygonal mirror.