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FrozenGate by Avery

am I actually seeing IR light?






Did the blue look cyan Crazlaser? If so then very interesting indeed.
 
Okay so I'm not sure if it's really blue, it's more like a shadow of light, possibly white, gray, something like that. Don't know how to describe it. It's so dim your eyes have to be adjusted for a half minute to view it.
 
That does not explain what is actually doing the doubling process though.

The yield is probably very low, but still, these has to be something in the path of the beam that can facilitate frequency doubling.
 
So I'm not actually perceiving IR? I heard IR is visible in high powers when focused by a naval laser safety contact at Carderock Navy base.
 
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I'm not 100% sure, but near-IR light looks red to me, at least when it's something like 808 nm.

Also i'm quite sure i cannot see 1064 nm at any intesity, i've seen these lasers in pulse mode operated to the point they break down air (causing sparks in mid air) without seeing any beam at all.

980 nm would seem too deep IR to actually see, but people vary. If you could see this wavelength, you should also be able to see the IR light from remote controls like the one for your TV and such.

Don't look directly into those though, there can be quite a bit of optical power in those IR leds. Whilst not lasers this could potentially be harmful at very close range.
 
Seems to me that you can see IR, Sean. But as it is in low light conditions - the rods might be dominant in perception and therefore there is a lack of color. However I see IR from remote controls or 808 nm laser as dim red, even in dark.

Human eye is a very complex organ, therefore it is maybe good to look at some of its parts to consider, how this might be explained:

https://en.wikipedia.org/wiki/Retina
 
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So I was bored today and started playing with my 800mw 980nm laser. I noticed in darkness I can see a dark grayish blue dot on the wall at close range if I move the laser slowly. Other than this the laser is not visible. Am I actually seeing the 980nm light? I have been lead to believe only 808nm is possibly visible and 980nm is far to long of a wl to see at all. But after seeing the dot I'm thinking that at these powers, 980nm might be slightly visible after all. It was really dim, by really dim I mean barely visible at all, your eyes have to adjust to the darkness and be really close to the dot.

"They were able to see the laser light, which was outside of the normal visible range, and we really wanted to figure out how they were able to sense light that was supposed to be invisible," said Frans Vinberg, PhD, one of the study's lead authors and a postdoctoral research associate in the Department of Ophthalmology and Visual Sciences at Washington University.
The visible spectrum includes waves of light that are 400-720 nanometers long," explained Kefalov, an associate professor of ophthalmology and visual sciences. "But if a pigment molecule in the retina is hit in rapid succession by a pair of photons that are 1,000 nanometers long, those light particles will deliver the same amount of energy as a single hit from a 500-nanometer photon, which is well within the visible spectrum. That's how we are able to see it. These findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments" ~ from https://phys.org/news/2014-12-human-eye-invisible-infrared.html

Keep in mind:
Color is not a physical property; it is merely the brain’s interpretation of different wavelengths of light. Human vision spans a visual spectrum of approximately 390-720nm. At the short end (390) is what we perceive as blue; at the long end (720) is red. This is nowhere near all light; in fact, it comprises less than an estimated 1% of 1% of the entire electromagnetic spectrum. The narrow range of light we can see is primarily a result of what wavelengths our photopigments are sensitive to; as an engineer would say, the pigments are the bottleneck. Human vision works via a process called phototransduction. In this process, light enters the eye through the pupil, is focused by the lens, and strikes the retina. On the retina are billions of photoreceptive cells called rods and cones, and in these rods and cones are phototransductive compounds called photopigments. These pigments are the target of our project." ~ from: Human NIR Perception - the first project - Science for the Masses
PS good explaination of visual phototransduction is here: https://en.wikipedia.org/wiki/Visual_phototransduction

Yes the 980nm light is stimulating your retina. Here is one report of people seeing 980nm as diffuse gray.

"At these powers, the 980 nm beacon was invisible in the light-adapted retina but was still somewhat visible to most subjects when dark-adapted and displayed in a dark visual field. For example, the required powers were 0.4-0.5 log units above Subject 4's dark-adapted visual threshold for continuous viewing. The beacon generally appeared as a small red spot when fixated, but sometimes appeared as a more diffuse gray spot when off the visual axis. This diffuse gray appearance may possibly reflect the activity of rods, the two-photon/second harmonic generation effect (where light of one half the beacon wavelength is created and potentially seen, Zaidi & Pokorny, 1988), or both. " ~ from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4013550/
 
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I wanted to rep you Encap.
So our eyes in certain circumstances can also use TPA. It is possible that the grey blue is a mix of both what I have observed and this. As when light is so dim, colour nearly is entirely lost leaving grey light which also matches your last point Encap. As the 980nm will be barely stimulating the rods.
 
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Interesting. Very. Thanks for sharing.
I wish the rep limit does not apply as this is second post from you today which deserves rep+, Encap. Adding to bookmarks for read when I have more time.

BTW: Human eye is awesome. And now consider that the eye is kind of "measuring device" even in terms of quantum mechanics - therefore creating the reality somehow. Fascinating.
 
Back when I was young and had one of those cheap 532 pens I could see the IR pumping diode from one of those things when the crystals got knocked loose. Like an idiot I looked into the aperture -_-

Now, if I can see that fine does that mean I can see 808nm just fine? :o

-Alex
 
The human brain is the more fascinating one by far, the amount it has to do in order to get an accurate description of the world around it is simply amazing.
Hap, that was most likely 808nm you was seeing anyway. It may of been possible for you to of detected 1064, but it seems far more probable that is was the 808 pump diode. In other words ... yes! :p
Well you learn from your youth mistakes, well at least some of us do. :D
 
Oliver: I like to ask people what they think the most complex structure in known universe is. I've heard so many good answers, but always when I say them they carry it in their head, they are surprised. Yes, human brain is something "out of this world". I'm very interested in it and my artworks tell the stories bit by bit also about this structure, between lines of course. ;)

Alex: It was likely IR filtered as you can see good now (I assume), so experience gained and let it be warning for the others. Thanks for sharing.

Edit: BTW Does anybody know how much rep have I spread before giving another one to the same member? I do not give reps just for nothing as it is kind of "rep inflation" IMO, but so many people posting valuable stuff deserve it and I cannot rep them because of spreading limit.
 
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"They were able to see the laser light, which was outside of the normal visible range, and we really wanted to figure out how they were able to sense light that was supposed to be invisible," said Frans Vinberg, PhD, one of the study's lead authors and a postdoctoral research associate in the Department of Ophthalmology and Visual Sciences at Washington University.
The visible spectrum includes waves of light that are 400-720 nanometers long," explained Kefalov, an associate professor of ophthalmology and visual sciences. "But if a pigment molecule in the retina is hit in rapid succession by a pair of photons that are 1,000 nanometers long, those light particles will deliver the same amount of energy as a single hit from a 500-nanometer photon, which is well within the visible spectrum. That's how we are able to see it. These findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments" ~ from https://phys.org/news/2014-12-human-eye-invisible-infrared.html

Keep in mind:
Color is not a physical property; it is merely the brain’s interpretation of different wavelengths of light. Human vision spans a visual spectrum of approximately 390-720nm. At the short end (390) is what we perceive as blue; at the long end (720) is red. This is nowhere near all light; in fact, it comprises less than an estimated 1% of 1% of the entire electromagnetic spectrum. The narrow range of light we can see is primarily a result of what wavelengths our photopigments are sensitive to; as an engineer would say, the pigments are the bottleneck. Human vision works via a process called phototransduction. In this process, light enters the eye through the pupil, is focused by the lens, and strikes the retina. On the retina are billions of photoreceptive cells called rods and cones, and in these rods and cones are phototransductive compounds called photopigments. These pigments are the target of our project." ~ from: Human NIR Perception - the first project - Science for the Masses
PS good explaination of visual phototransduction is here: https://en.wikipedia.org/wiki/Visual_phototransduction

Yes the 980nm light is stimulating your retina. Here is one report of people seeing 980nm as diffuse gray.

"At these powers, the 980 nm beacon was invisible in the light-adapted retina but was still somewhat visible to most subjects when dark-adapted and displayed in a dark visual field. For example, the required powers were 0.4-0.5 log units above Subject 4's dark-adapted visual threshold for continuous viewing. The beacon generally appeared as a small red spot when fixated, but sometimes appeared as a more diffuse gray spot when off the visual axis. This diffuse gray appearance may possibly reflect the activity of rods, the two-photon/second harmonic generation effect (where light of one half the beacon wavelength is created and potentially seen, Zaidi & Pokorny, 1988), or both. " ~ from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4013550/

Dang man, squarely answered my question. +rep for sure.

Also thanks Curtis.
 


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