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Humans can see Near Infrared?--second try


Damon

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Came across this in my PopSci magazine. If this has already been posted then D'oh!

 

Also linked is the the rebuttal from a Retinal Neuroscientist--which is intriguing as is the experimenters replies to the rebuttal.

 

http://www.blastr.com/2014-9-12/biohackers-trying-modify-human-eye-see-infrared-spectrums

 

http://www.popsci.com/article/diy/can-we-hack-our-vision-see-infrared-naked-eye

 

-And the neuro's take along with comment from the original authors:

http://petapixel.com/2014/08/25/retinal-neuroscientists-rebuttal-humans-cant-see-infrared-matter-eat/

 

The actual crowd sourced experiment site:

https://experiment.com/projects/can-we-biologically-extend-the-range-of-human-vision-into-the-near-infrared/updates

 

Alright that's enough links.

 

-D

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I believe they did try this awhile ago in the military (of course) as one poster said. So it may not be entirely new but still interesting.

 

-D

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enricosavazzi

I checked the literature on NIR vision in mammals a few years ago, and did not find any clearly documented cases of NIR vision in this group, and in general among vertebrates. There are explanations of this in the literature, for example that it would not be very useful, since most tissues and organic structures are reflective, so there would not be much to see in terms of contrast.

 

I have a discussion of these points and literature references in:

Savazzi, E. & Sasaki, T. 2013: Observations on land snail shells in near-ultraviolet, visible and near-infrared radiation. Journal of Molluscan Studies 79: 95-111; Oxford. doi: 10.1093/mollus/eys039

(available for example on researchgate.net if you are a member, membership is free).

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  • 10 months later...
I have heard it's possible to "see" infrared in the form of two photon capture. If a light source is strong enough and the sensor is sensitive two photons can be captured as if a single photon of the same energy in a similar manner to that if a doubling crystal in a green laser pointer. The human eye is very sensitive in the green which is perfect for doubling NIR photons. Not sure how well this would work for the other "channels" as they are less sensitive.
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One thing needing emphasis is that frequency doubling and two-photon excitation are two separate things, even if they would in principle produce the same effect. In the former, two photons combine inside a specially engineered crystal to produce an actual photon of doubled frequency. In the second, two photons are absorbed nearly simultaneously by a target producing the same excitation that would have been produced with a single photon of doubled frequency. The first mechanism is frankly unlikely in a retina, as crystal parameters and beam alignment are fairly critical. The second mechanism is most likely in vivo.
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One thing needing emphasis is that frequency doubling and two-photon excitation are two separate things, even if they would in principle produce the same effect. In the former, two photons combine inside a specially engineered crystal to produce an actual photon of doubled frequency. In the second, two photons are absorbed nearly simultaneously by a target producing the same excitation that would have been produced with a single photon of doubled frequency. The first mechanism is frankly unlikely in a retina, as crystal parameters and beam alignment are fairly critical. The second mechanism is most likely in vivo.

 

Of course. I was simply trying to use a similar "real world" example of nonlinear absorption that would be familiar to people who havent spent much time in a laser lab. In the former the two photons are absorbed and the sum of the energy is released as a single photon. In the latter the two photons are absorbed and the energy used to trigger a nerve impulse.

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