10 ms·

It will be interesting, to me, if there are any observable effects on nature exposed to 200 meter blasts of IR type wavelength stuff. I mean, maybe it'll scare

It will be interesting, to me, if there are any observable effects on nature exposed to 200 meter blasts of IR type wavelength stuff. I mean, maybe it'll scare off deer, or pull them in closer to see what's up? Any number of species with un-intended consequences. Insects in the desert. Pidgeons in the big city. Gulls on the coast. Maybe it's totally harmless, but I'd like a study that verifies mass adoption would not have ecological consequences.

philipkglass 9y ago
Your comment spurred me to search for information about near-infrared vision systems in animals. NIR vision appears to be entirely absent from vertebrates. (I am not claiming that it is present in invertebrates, only that I found stronger claims about absence from vertebrates.) See "The Verriest Lecture 2009: Recent progress in understanding mammalian color vision" https://pdfs.semanticscholar.org/c9df/0b61e4a45e10577c001513a4fc1432696b3c.pdf https://pdfs.semanticscholar.org/c9df/0b61e4a45e10577c001513... Particularly Figure 1. Vertebrate photopigment sensitivity drops off rapidly toward the near IR (~700 nm). I found this fascinating related (but not peer reviewed) document on arXiv, "Did Evolution get it right? An evaluation of near-infrared imaging in semantic scene segmentation" https://arxiv.org/pdf/1611.08815.pdf https://arxiv.org/pdf/1611.08815.pdf The author performs semantic segmentation with convnets using conventional visual-spectrum images and compares performance with images spectrally extended into the near-infrared. He finds that adding the additional NIR band did not improve task performance -- hence that evolution "got it right" by not expanding vision into a wavelength region that fails to improve semantic segmentation. I'm not sure how good this work is from a professional biologist's perspective, but I found it damn interesting. EDIT: note that this laser operating at 1550 nm is far from the long wave IR (~8000 nm and up) that various animals sense to detect prey body heat.
- prestonbriggs 9y ago
  I believe that I can't see that wavelength, but the energy has to go somewhere (similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest). I think the better question is: Will it blind you/me/animals?
  - goodcanadian 9y ago
    Indeed, I find it mildly painful to look at IR emitters, for example, on a "night vision" security camera. I don't believe it is dangerous or will blind anyone, or anything, but it is plausible to me that there could be an unanticipated effect. EDIT: It appears that this is given a passing mention in the article: . . . it can receive at a wavelength of 1550 nanometers, deep in the infrared part of the spectrum. That makes this wavelength much safer for human eyes than today’s standard wavelength, 905 nm.
  - splawn 9y ago
    It depends on the power density. I have an IR laser that is invisible and it would burn your eyes out of your head.
    - hwillis 9y ago
      ~40 mW peak, ~10 nS pulses
  - hueving 9y ago
    >similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest Yet wireless access points spew microwave radiation at you all day.
    - p1esk 9y ago
      Not at 1,000W.
      - hwillis 9y ago
        However, you do receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight: https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spe...
        9y ago
- stenl 9y ago
  Vampire bats use modified capsaicin (chili pepper) receptors in their nose to detect infrared light: https://www.nature.com/nature/journal/v476/n7358/full/nature10245.html https://www.nature.com/nature/journal/v476/n7358/full/nature... They use this to find their warm-bodied prey, but of course it's only detection, not vision. I learned this today, and now I'm happy I did.
  - hinkley 9y ago
    Pit vipers too. The pits are used to 'see' infrared.
  - radarsat1 9y ago
    Thank you. Definitely the coolest thing I will learn today.
  - vanderZwan 9y ago
    I was about to ask if you work where I do, then I saw your username, then I remembered that you hired me through HN..
    - nsebban 9y ago
      You guys seem to have amazingly interesting jobs. Please hire me, I'm your future-colleague.
  - Kliment 9y ago
    sci-hub link https://sci-hub.ac/https://www.nature.com/nature/journal/v476/n7358/full/nature10245.html https://sci-hub.ac/https://www.nature.com/nature/journal/v47...
- abakker 9y ago
  Pit Vipers can sense IR with a secondary sight organ called a fossa. https://en.wikipedia.org/wiki/Pit_viper https://en.wikipedia.org/wiki/Pit_viper
- phkahler 9y ago
  >> He finds that adding the additional NIR band did not improve task performance But did they try in low light? It seems that seeing in IR should help with detection of predators or prey at night.
  - LeifCarrotson 9y ago
    IR near the visible range is associated with night vision because we use active night vision goggles that use an infrared spotlight at 850 or 940 nm wavelengths (700 nm is red). This is not particularly useful without an illuminator, you're basically just getting visible light amplification then. Passive thermal vision that might pick out a warm object in the dark require sensing of ~10,000 nm/10 um infrared, a very different problem! And one that wouldn't be easy to solve biologically, as it basically requires being colder than the object you are sensing. Edit: but not impossible! https://en.m.wikipedia.org/wiki/Infrared_sensing_in_snakes https://en.m.wikipedia.org/wiki/Infrared_sensing_in_snakes
  - philipkglass 9y ago
    Are you referring to sensing body heat of other animals? That's a long wave IR emission, ~8000 nm and up. Some animals do indeed sense that and it is quite useful at night. This laser, and the paper I linked to, are operating with much shorter IR wavelengths (~800 to 1550 nm). This spectral region overwhelmingly comes from sunlight under natural conditions, and its intensity drops sharply at night like the ordinary visible range.
  - Cybiote 9y ago
    Nocturnal animals function by having a large proportion of rods. This was true of our anthropoid ancestors, resulting in humans having very limited high acuity color vision. We get round this by rapidly scanning and stitching the world together (the inability to do this is a sore problem for visual prosthesis). That the world seems sharp and rich in color is a testament to the feats of predictive inference our brains regularly perform.
- Scarblac 9y ago
  One thing is that water has absorption bands at 970nm, 1200nm, 1450nm, and 1950nm, and eyes have a lot of water in them. So they simply aren't very transparent in the near infrared.
  - ethbro 9y ago
    Also, why would you evolve eyes tuned to wavelengths that don't penetrate water well? That seems maladaptive in an aquatic environment. https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_by_water#/media/File%3AAbsorption_spectrum_of_liquid_water.png https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_b...
    - JshWright 9y ago
      Why would you evolve eyes that could see wavelengths that don't penetrate your environment?
      - linkregister 9y ago
        Yeah, why would you?
        gknoy 9y ago
        I'm not sure if this exchange means that there is no good reason to do that, or if it means that the reason why one would want to do that is blindingly obvious to everyone except me. :)
        tempestn 9y ago
        The reason you want to see wavelengths that don't penetrate your environment is so that you can see your environment.
        edaemon 9y ago
        None of that light would ever reach your eyes for you to see it, though, right? Or am I missing something really obvious?
- kyrra 9y ago
  It's worth pointing out that there are aircraft mounted LiDAR systems that already operate at 1550nm, such as [0]. Another company has an interesting paper about which wavelength is best for their activities[1]. http://www.teledyneoptech.com/index.php/product/titan/ http://www.teledyneoptech.com/index.php/product/titan/ [1] (PDF!) http://www.riegl.com/uploads/tx_pxpriegldownloads/Paper_ILMF_2011_RIEGL_Multiwavelength_ALS.pdf http://www.riegl.com/uploads/tx_pxpriegldownloads/Paper_ILMF...
hwillis 9y ago
This wavelength of light is used for long range telecomms. We would know if it did anything. Animals can't see this wavelength, not even snakes or fish. In addition to that the laser spot is spread rapidly over a very wide area and it won't actually be visible except to extremely fast sensors, which eyes are not.
chillydawg 9y ago
Fish are sensitive to IR, it penetrates water better than visible or UV.
- eric_h 9y ago
  > IR, it penetrates water better than visible or UV. What? IR is lower energy than visible red and that's the first color to go when you get a few feet under water (with no local light source).
  - dheera 9y ago
    Water does absorb infrared well but it's not because it has lower energy. Infrared is absorbed well due to the spectrum of vibrational transitions. Ultraviolet is also absorbed well, due to electronic transitions. There is a "window" in the visible light that is not absorbed well by many transitions.
    - eric_h 9y ago
      > but it's not because it has lower energy...There is a "window" in the visible light fair enough, I got my physics a bit wrong there, but I was under the impression that that window was in the blue/green part of the spectrum since I do know that water is good at blocking UV and even cosmic radiation. I also know that it's good at blocking visible red, because if you go further than about 20-30 feet down on a sunny day and cut yourself, your blood looks green. Is there an additional window in the infrared part of the spectrum that supports GP's point?
- hwillis 9y ago
  some fish see some IR. Carp etc. would be able to see the 900 nm light in normal lidar, but even they can't see 1550 nm.
AndrewKemendo 9y ago
Considering ~55% of the sun's energy that hits the earth is in the form of IR, my guess is IR systems would be marginal. I think it bears testing though to be sure. As you say other creatures are much more sensitive to IR differences.
- function_seven 9y ago
  That's a good point, but also reminds me of moths circling a flame or porch light. The vast majority of light we see in the world comes from the sun, but when the sun is elsewhere, our artificial light triggers changes in how insects behave. I wonder if ground-source lidar at night would have similar effects on animals that are "used to" IR coming from above.
dheera 9y ago
Deer cannot see at 1550 nm. I'm not aware of any mammals that can.
agitator 9y ago
This is a good point. But same goes for other sensors in cars. I always wondered how annoying AF ultra-sonic sensors are for dogs. It looks like most ultrasonic sensors are out of range for dogs, but the ultrasonics for sure mess with bats. I wonder how bat populations will be affected when all of these ultrasonic sensors mess with their ability to hunt.
- fudged71 9y ago
  Cops in my city installed subsonic sirens on their cars to alert people who are playing loud music etc. Its always bothered me a bit about not knowing the potential impact to animals
- hwillis 9y ago
  Ultrasound transducers are not the only producers of ultrasound, nor the loudest. Most things that vibrate create ultrasound, including almost anything that moves. Noise pollution is mostly produced accidentally. Also, nocturnal bats will largely be unaffected by cars in no small part because they don't cohabitate with humans very much.
seanalltogether 9y ago
1500nm is way outside the the range of usable solar radiation in nature. https://upload.wikimedia.org/wikipedia/commons/e/e7/Solar_spectrum_en.svg https://upload.wikimedia.org/wikipedia/commons/e/e7/Solar_sp... Snakes pick back up around 5000nm since that's the temperature other living animals radiate, which is helpful in hunting. https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes
grizzles 9y ago
I don't know about IR but Kestrel's (the bird) are UV sensitive. AFAIK all organics emit IR so it's probably not going to be a problem.
red75prime 9y ago
Can I direct your attention to the street lights? Those death traps, causing millions of insects to fly in circles and possibly die of exhaustion. You will save many more insects, raising awareness to this problem.
- rijoja 9y ago
  Exactly we are blasting so much radiation everywhere, why should we start caring now with the IR radiation.
  - Crespyl 9y ago
    The best way to start fixing a problem is to stop making things worse. LIDAR may or may not have an adverse impact on wildlife, but we should at least find out and see if there are simple ways to mitigate any possible side effects.
simonh 9y ago
Many types of common headlights, and other light sources, emit tons of IR radiation already so we'd probably know.
joshvm 9y ago
What you care about is the maximum permissible exposure at close range - because it's entirely possible that a kid is going to walk up to your car and stick their face up against the glass. The laser beam will already be fairly wide (order of mm) as it exists the system, but it needs to be reasonably low divergence to give you accurate spatial information 200 m away. We should assume to be pessimistic, that you get the full beam into your eye (up to 7 mm). This is really back of the envelope stuff, but there are lots of factors to consider. You could probably get away with even a 100mW laser with the right setup. Obvious disclaimer that you should respect laser safety and not trust someone's internet napkin calculations. According to this you're allowed 1W/m^2 at > 1400nm for an accidental exposure (100 seconds): https://workspace.imperial.ac.uk/physics/Public/physicsdocs/about/safety/files/MPE-tables.pdf https://workspace.imperial.ac.uk/physics/Public/physicsdocs/... Equivalently that's 1 mW/mm^2. So the question is, what power is the laser kicking out? A Faro scanner can put out as much as 20mW/mm^2 at 1m and their systems are thus Class 3R. So far, so bad. However... laser safety ratings are given as "Under normal operating conditions". The laser is being scanned, and very quickly at that, so you'd only be getting very short bursts of light (I don't know if it's truly a pulsed laser). If you stared into the beam continuously you would have problems, but since the beam is only going to hit you for a fraction of a second it's unlikely to do any damage. And indeed Faro say that for practical purposes their system is eye-safe, even though it's got a stonking laser in it. The tables say you can go up to 10^4 J/m^2 for short exposures and suppose we only have the beam in our eye for 10^-3 seconds (additionally the pulse length will be very short), you're allowed a light power of perhaps 1000 times higher. Maybe divide by a factor of 100 or so because you'd get several repeat exposures if you stood in the same place or if you're standing on a street filled with these things. Have a look at Faro's manual, Appendix E for a real example of this kind of analysis: https://doarch332.files.wordpress.com/2013/11/e866_faro_laser_scanner_focus3d_manual_en.pdf https://doarch332.files.wordpress.com/2013/11/e866_faro_lase...

philipkglass 9y ago

Your comment spurred me to search for information about near-infrared vision systems in animals. NIR vision appears to be entirely absent from vertebrates. (I am not claiming that it is present in invertebrates, only that I found stronger claims about absence from vertebrates.) See "The Verriest Lecture 2009: Recent progress in understanding mammalian color vision" https://pdfs.semanticscholar.org/c9df/0b61e4a45e10577c001513a4fc1432696b3c.pdf https://pdfs.semanticscholar.org/c9df/0b61e4a45e10577c001513... Particularly Figure 1. Vertebrate photopigment sensitivity drops off rapidly toward the near IR (~700 nm). I found this fascinating related (but not peer reviewed) document on arXiv, "Did Evolution get it right? An evaluation of near-infrared imaging in semantic scene segmentation" https://arxiv.org/pdf/1611.08815.pdf https://arxiv.org/pdf/1611.08815.pdf The author performs semantic segmentation with convnets using conventional visual-spectrum images and compares performance with images spectrally extended into the near-infrared. He finds that adding the additional NIR band did not improve task performance -- hence that evolution "got it right" by not expanding vision into a wavelength region that fails to improve semantic segmentation. I'm not sure how good this work is from a professional biologist's perspective, but I found it damn interesting. EDIT: note that this laser operating at 1550 nm is far from the long wave IR (~8000 nm and up) that various animals sense to detect prey body heat.

prestonbriggs 9y ago
I believe that I can't see that wavelength, but the energy has to go somewhere (similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest). I think the better question is: Will it blind you/me/animals?
- goodcanadian 9y ago
  Indeed, I find it mildly painful to look at IR emitters, for example, on a "night vision" security camera. I don't believe it is dangerous or will blind anyone, or anything, but it is plausible to me that there could be an unanticipated effect. EDIT: It appears that this is given a passing mention in the article: . . . it can receive at a wavelength of 1550 nanometers, deep in the infrared part of the spectrum. That makes this wavelength much safer for human eyes than today’s standard wavelength, 905 nm.
- splawn 9y ago
  It depends on the power density. I have an IR laser that is invisible and it would burn your eyes out of your head.
  - hwillis 9y ago
    ~40 mW peak, ~10 nS pulses
- hueving 9y ago
  >similarly, I can't see microwave radiation, but don't want to put my head in a running microwave, a la Infinite Jest Yet wireless access points spew microwave radiation at you all day.
  - p1esk 9y ago
    Not at 1,000W.
    - hwillis 9y ago
      However, you do receive a couple hundred watts of near infrared radiation (ie the 1550 nm in the laser) just by being in direct sunlight: https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spe...
      - 9y ago
stenl 9y ago
Vampire bats use modified capsaicin (chili pepper) receptors in their nose to detect infrared light: https://www.nature.com/nature/journal/v476/n7358/full/nature10245.html https://www.nature.com/nature/journal/v476/n7358/full/nature... They use this to find their warm-bodied prey, but of course it's only detection, not vision. I learned this today, and now I'm happy I did.
- hinkley 9y ago
  Pit vipers too. The pits are used to 'see' infrared.
- radarsat1 9y ago
  Thank you. Definitely the coolest thing I will learn today.
- vanderZwan 9y ago
  I was about to ask if you work where I do, then I saw your username, then I remembered that you hired me through HN..
  - nsebban 9y ago
    You guys seem to have amazingly interesting jobs. Please hire me, I'm your future-colleague.
- Kliment 9y ago
  sci-hub link https://sci-hub.ac/https://www.nature.com/nature/journal/v476/n7358/full/nature10245.html https://sci-hub.ac/https://www.nature.com/nature/journal/v47...
abakker 9y ago
Pit Vipers can sense IR with a secondary sight organ called a fossa. https://en.wikipedia.org/wiki/Pit_viper https://en.wikipedia.org/wiki/Pit_viper
phkahler 9y ago
>> He finds that adding the additional NIR band did not improve task performance But did they try in low light? It seems that seeing in IR should help with detection of predators or prey at night.
- LeifCarrotson 9y ago
  IR near the visible range is associated with night vision because we use active night vision goggles that use an infrared spotlight at 850 or 940 nm wavelengths (700 nm is red). This is not particularly useful without an illuminator, you're basically just getting visible light amplification then. Passive thermal vision that might pick out a warm object in the dark require sensing of ~10,000 nm/10 um infrared, a very different problem! And one that wouldn't be easy to solve biologically, as it basically requires being colder than the object you are sensing. Edit: but not impossible! https://en.m.wikipedia.org/wiki/Infrared_sensing_in_snakes https://en.m.wikipedia.org/wiki/Infrared_sensing_in_snakes
- philipkglass 9y ago
  Are you referring to sensing body heat of other animals? That's a long wave IR emission, ~8000 nm and up. Some animals do indeed sense that and it is quite useful at night. This laser, and the paper I linked to, are operating with much shorter IR wavelengths (~800 to 1550 nm). This spectral region overwhelmingly comes from sunlight under natural conditions, and its intensity drops sharply at night like the ordinary visible range.
- Cybiote 9y ago
  Nocturnal animals function by having a large proportion of rods. This was true of our anthropoid ancestors, resulting in humans having very limited high acuity color vision. We get round this by rapidly scanning and stitching the world together (the inability to do this is a sore problem for visual prosthesis). That the world seems sharp and rich in color is a testament to the feats of predictive inference our brains regularly perform.
Scarblac 9y ago
One thing is that water has absorption bands at 970nm, 1200nm, 1450nm, and 1950nm, and eyes have a lot of water in them. So they simply aren't very transparent in the near infrared.
- ethbro 9y ago
  Also, why would you evolve eyes tuned to wavelengths that don't penetrate water well? That seems maladaptive in an aquatic environment. https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_by_water#/media/File%3AAbsorption_spectrum_of_liquid_water.png https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_b...
  - JshWright 9y ago
    Why would you evolve eyes that could see wavelengths that don't penetrate your environment?
    - linkregister 9y ago
      Yeah, why would you?
      - gknoy 9y ago
        I'm not sure if this exchange means that there is no good reason to do that, or if it means that the reason why one would want to do that is blindingly obvious to everyone except me. :)
        tempestn 9y ago
        The reason you want to see wavelengths that don't penetrate your environment is so that you can see your environment.
        edaemon 9y ago
        None of that light would ever reach your eyes for you to see it, though, right? Or am I missing something really obvious?
kyrra 9y ago
It's worth pointing out that there are aircraft mounted LiDAR systems that already operate at 1550nm, such as [0]. Another company has an interesting paper about which wavelength is best for their activities[1]. http://www.teledyneoptech.com/index.php/product/titan/ http://www.teledyneoptech.com/index.php/product/titan/ [1] (PDF!) http://www.riegl.com/uploads/tx_pxpriegldownloads/Paper_ILMF_2011_RIEGL_Multiwavelength_ALS.pdf http://www.riegl.com/uploads/tx_pxpriegldownloads/Paper_ILMF...

hwillis 9y ago

This wavelength of light is used for long range telecomms. We would know if it did anything. Animals can't see this wavelength, not even snakes or fish. In addition to that the laser spot is spread rapidly over a very wide area and it won't actually be visible except to extremely fast sensors, which eyes are not.

chillydawg 9y ago

Fish are sensitive to IR, it penetrates water better than visible or UV.

eric_h 9y ago
> IR, it penetrates water better than visible or UV. What? IR is lower energy than visible red and that's the first color to go when you get a few feet under water (with no local light source).
- dheera 9y ago
  Water does absorb infrared well but it's not because it has lower energy. Infrared is absorbed well due to the spectrum of vibrational transitions. Ultraviolet is also absorbed well, due to electronic transitions. There is a "window" in the visible light that is not absorbed well by many transitions.
  - eric_h 9y ago
    > but it's not because it has lower energy...There is a "window" in the visible light fair enough, I got my physics a bit wrong there, but I was under the impression that that window was in the blue/green part of the spectrum since I do know that water is good at blocking UV and even cosmic radiation. I also know that it's good at blocking visible red, because if you go further than about 20-30 feet down on a sunny day and cut yourself, your blood looks green. Is there an additional window in the infrared part of the spectrum that supports GP's point?
hwillis 9y ago
some fish see some IR. Carp etc. would be able to see the 900 nm light in normal lidar, but even they can't see 1550 nm.

AndrewKemendo 9y ago

Considering ~55% of the sun's energy that hits the earth is in the form of IR, my guess is IR systems would be marginal. I think it bears testing though to be sure. As you say other creatures are much more sensitive to IR differences.

function_seven 9y ago
That's a good point, but also reminds me of moths circling a flame or porch light. The vast majority of light we see in the world comes from the sun, but when the sun is elsewhere, our artificial light triggers changes in how insects behave. I wonder if ground-source lidar at night would have similar effects on animals that are "used to" IR coming from above.

dheera 9y ago

Deer cannot see at 1550 nm. I'm not aware of any mammals that can.

agitator 9y ago

This is a good point. But same goes for other sensors in cars. I always wondered how annoying AF ultra-sonic sensors are for dogs. It looks like most ultrasonic sensors are out of range for dogs, but the ultrasonics for sure mess with bats. I wonder how bat populations will be affected when all of these ultrasonic sensors mess with their ability to hunt.

fudged71 9y ago
Cops in my city installed subsonic sirens on their cars to alert people who are playing loud music etc. Its always bothered me a bit about not knowing the potential impact to animals
hwillis 9y ago
Ultrasound transducers are not the only producers of ultrasound, nor the loudest. Most things that vibrate create ultrasound, including almost anything that moves. Noise pollution is mostly produced accidentally. Also, nocturnal bats will largely be unaffected by cars in no small part because they don't cohabitate with humans very much.

seanalltogether 9y ago

1500nm is way outside the the range of usable solar radiation in nature. https://upload.wikimedia.org/wikipedia/commons/e/e7/Solar_spectrum_en.svg https://upload.wikimedia.org/wikipedia/commons/e/e7/Solar_sp... Snakes pick back up around 5000nm since that's the temperature other living animals radiate, which is helpful in hunting. https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes

grizzles 9y ago

I don't know about IR but Kestrel's (the bird) are UV sensitive. AFAIK all organics emit IR so it's probably not going to be a problem.

red75prime 9y ago

Can I direct your attention to the street lights? Those death traps, causing millions of insects to fly in circles and possibly die of exhaustion. You will save many more insects, raising awareness to this problem.

rijoja 9y ago
Exactly we are blasting so much radiation everywhere, why should we start caring now with the IR radiation.
- Crespyl 9y ago
  The best way to start fixing a problem is to stop making things worse. LIDAR may or may not have an adverse impact on wildlife, but we should at least find out and see if there are simple ways to mitigate any possible side effects.

simonh 9y ago

Many types of common headlights, and other light sources, emit tons of IR radiation already so we'd probably know.

joshvm 9y ago

What you care about is the maximum permissible exposure at close range - because it's entirely possible that a kid is going to walk up to your car and stick their face up against the glass. The laser beam will already be fairly wide (order of mm) as it exists the system, but it needs to be reasonably low divergence to give you accurate spatial information 200 m away. We should assume to be pessimistic, that you get the full beam into your eye (up to 7 mm). This is really back of the envelope stuff, but there are lots of factors to consider. You could probably get away with even a 100mW laser with the right setup. Obvious disclaimer that you should respect laser safety and not trust someone's internet napkin calculations. According to this you're allowed 1W/m^2 at > 1400nm for an accidental exposure (100 seconds): https://workspace.imperial.ac.uk/physics/Public/physicsdocs/about/safety/files/MPE-tables.pdf https://workspace.imperial.ac.uk/physics/Public/physicsdocs/... Equivalently that's 1 mW/mm^2. So the question is, what power is the laser kicking out? A Faro scanner can put out as much as 20mW/mm^2 at 1m and their systems are thus Class 3R. So far, so bad. However... laser safety ratings are given as "Under normal operating conditions". The laser is being scanned, and very quickly at that, so you'd only be getting very short bursts of light (I don't know if it's truly a pulsed laser). If you stared into the beam continuously you would have problems, but since the beam is only going to hit you for a fraction of a second it's unlikely to do any damage. And indeed Faro say that for practical purposes their system is eye-safe, even though it's got a stonking laser in it. The tables say you can go up to 10^4 J/m^2 for short exposures and suppose we only have the beam in our eye for 10^-3 seconds (additionally the pulse length will be very short), you're allowed a light power of perhaps 1000 times higher. Maybe divide by a factor of 100 or so because you'd get several repeat exposures if you stood in the same place or if you're standing on a street filled with these things. Have a look at Faro's manual, Appendix E for a real example of this kind of analysis: https://doarch332.files.wordpress.com/2013/11/e866_faro_laser_scanner_focus3d_manual_en.pdf https://doarch332.files.wordpress.com/2013/11/e866_faro_lase...