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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 a
by 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I found this fascinating related (but not peer reviewed) document on arXiv, "Did Evolution get it right?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 agoI 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 agoIndeed, 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 agoIt 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 agoNot at 1,000W.
- hwillis 9y agoHowever, 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...
- p1esk 9y agoBut even though I can't see it, I can definitely feel it.
- hwillis 9y agoThe premise of the parent comment is that even invisible lasers could be harmful. You pointed out that microwaves may not be as harmful at lower levels of power. I pointed out that the output of a lidar beam is far below the level that you get from sunlight, which doesn't even cause cancer and certainly doesn't blind people. Just because I like running numbers, here's the comparison: the laser in this lidar has a power of ~40 mW, ~1000x less than sunlight. Lidar pulses are on the order of 10 nanoseconds, 100,000,000x less than a second. The energy on your eyes is less than 100 billion times less than a second in bright sunlight. There is certainly no mechanism for thermal damage to occur.
- deleted 9y ago[deleted]
- hwillis 9y agoThe laser in the article is on the order of tens of milliwatts. Even directly into your eye would not damage it. It would be painful, especially if it was in a visible wavelength, but the laser spot from a lidar is in one location for less than a microsecond. In terms of direct heating, tens of milliwatts isn't even enough to really make a human-detectable rise.
- kwhitefoot 9y ago> is in one location for less than a microsecond When it is working properly.
- jhall1468 9y agoAnd self-diagnostics will know when it isn't.
- hwillis 9y agoSame with elevators, microwaves, airbags, and in fact literally anything that plugs into the wall. 120 volts can kill you if you contact it. The laser is eye-safe, meaning you can look directly at it continuously and be fine. Though, if you did, you would deserve injury. Kind of like sticking your hand in a blender. The device will not manage to malfunction and miraculously shoot you in the eye from meters away.
- jhall1468 9y agoWould it even be painful at that wavelength?
- hwillis 9y agoNo, although lasers can sometimes be dangerous without being painful. Even if they aren't, by the time it hurts it is too late.
- stenl 9y agoVampire 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 agoPit vipers too. The pits are used to 'see' infrared.
- radarsat1 9y agoThank you. Definitely the coolest thing I will learn today.
- vanderZwan 9y agoI 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 agoYou guys seem to have amazingly interesting jobs. Please hire me, I'm your future-colleague.
- Kliment 9y agosci-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 agoPit 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 agoIR 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 agoAre 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 agoNocturnal 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 agoOne 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 agoAlso, 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 agoWhy would you evolve eyes that could see wavelengths that don't penetrate your environment?
- linkregister 9y agoYeah, why would you?
- gknoy 9y agoI'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. :)
- kyrra 9y agoIt'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...