Old 12-05-2016, 08:24 AM #1
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Default Visiblity help!

Hello folks,

I've recently completed most rainbow(at least good enough for me) so I was thinking about venturing out into the Near-IR range of lasers just so I can have one in my possession, as every hobbyist should!

Now, laserbtb has some pretty neat 808nm pen styled lasers for pretty good prices. The one I am eyeing is their 5mW version(most likely more) for $26.57! I do have a few questions though, and yes, I did look in the search bar but most the questions regarding visibility for this wavelength weren't as such low powers, mostly around 100mW-300mW.

-Would 5mW of 808 be visible? At all? I don't need anything stunning but I've seen 4mW's of 405 in mid-day and could barely see the dot across my room. I've read that the human eye can actually see past the "general" 780nm end limit range of what you can see. I am not very interested in going into their next power level, 100mW as this stats entering dangerous territory, plus I'd most likely not use it other then to look at!

Thank you!

-Alex


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Old 12-05-2016, 08:48 AM #2
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Default Re: Visiblity help!

I would not expect to see 5mw of 808nm as a beam set to infinity focus, but might be possible to see a very tiny dim red dot if focused into a very fine point on black paper or something. If there is enough power, you can see 808nm as a dim red color but that much power is dangerous if you are too close to it, or get a direct reflection, according to all of the advise I've seen here. I can clearly see a tiny red dot from the output of a 200mw laser pointer on black paper, when focused to a point, so maybe you will. Turn off the lights and try it at 5mw.

I would be interested in knowing if a 5mw pointer can be viewed as a tiny red dot or not because I am doubtful you will see anything that way.
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Old 12-05-2016, 08:51 AM #3
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Default Re: Visiblity help!

Quote:
Originally Posted by Alaskan View Post
I would not expect to see 5mw of 808nm as a beam set to infinity focus, but might be possible to see a very tiny dim red dot if focused into a very fine point on black paper or something. If there is enough power, you can see 808nm as a dim red color but that much power is dangerous if you are too close to it, or get a direct reflection, according to all of the advise I've seen here. I can clearly see a tiny red dot from the output of a 200mw laser pointer on black paper, when focused to a point, so maybe you will. Turn off the lights and try it at 5mw.

I would be interested in knowing if a 5mw pointer can be viewed as a tiny red dot or not because I am doubtful you will see anything that way.
Hello Alaskan,

Thanks! Yeah, 5mW of 808nm is definitely pushing what our eyes can see. I'll wait until a couple more posts come in and I'll make my decision then. It's not a very expensive laser so it wouldn't be a huge loss

-Alex
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Old 12-05-2016, 12:12 PM #4
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Default Re: Visiblity help!

For a 808nm to have the same brightness as a 1mW 650nm pointer, you would need 50W with an output of ~0.07 lumens between them.
5mW of 808 is 7.216 μLm and would be as bright as 0.1μW of 650nm.
I hope that clears things up.
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Old 12-05-2016, 03:29 PM #5
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Default Re: Visiblity help!

I have a 250 mW 790 nm build and the light is not visible unless focused through a lens. Even still, when focused, it appears as a very dim dark reddish dot...

All our eyes are different anyway and some people can see better toward each end of the visible spectrum - visible is considered 400 - 800 nm.

So I wouldnt really expect a 5 mW 808 to be very useful unless you are using some sort of detector to pick it up, or camera lcd to view it. As Im sure you know IR is also dangerous, because you cant see where the beam is going. This means you could quite easily and inadvertently pick up a specular reflection.
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Old 12-05-2016, 05:15 PM #6
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Default Re: Visiblity help!

Quote:
Originally Posted by Hap View Post
Hello folks,

I've recently completed most rainbow(at least good enough for me) so I was thinking about venturing out into the Near-IR range of lasers just so I can have one in my possession, as every hobbyist should!

Now, laserbtb has some pretty neat 808nm pen styled lasers for pretty good prices. The one I am eyeing is their 5mW version(most likely more) for $26.57! I do have a few questions though, and yes, I did look in the search bar but most the questions regarding visibility for this wavelength weren't as such low powers, mostly around 100mW-300mW.

-Would 5mW of 808 be visible? At all? I don't need anything stunning but I've seen 4mW's of 405 in mid-day and could barely see the dot across my room. I've read that the human eye can actually see past the "general" 780nm end limit range of what you can see. I am not very interested in going into their next power level, 100mW as this stats entering dangerous territory, plus I'd most likely not use it other then to look at!

Thank you!

-Alex
It depends upon your particualr eyes as to whether or not you can detect light outside the visible range considered "normal" human spectral sensitivity.

Have a look here: Human infrared vision is triggered by two-photon chromophore isomerization
Abstract from above paper- "Vision relies on photoactivation of visual pigments in rod and cone photoreceptor cells of the retina. The human eye structure and the absorption spectra of pigments limit our visual perception of light. Our visual perception is most responsive to stimulating light in the 400- to 720-nm (visible) range. First, we demonstrate by psychophysical experiments that humans can perceive infrared laser emission as visible light. Moreover, we show that mammalian photoreceptors can be directly activated by near infrared light with a sensitivity that paradoxically increases at wavelengths above 900 nm, and display quadratic dependence on laser power, indicating a nonlinear optical process. Biochemical experiments with rhodopsin, cone visual pigments, and a chromophore model compound 11-cis-retinyl-propylamine Schiff base demonstrate the direct isomerization of visual chromophore by a two-photon chromophore isomerization. Indeed, quantum mechanics modeling indicates the feasibility of this mechanism. Together, these findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments. "

See also interesting article on this subject here: https://source.wustl.edu/2014/12/the...nfrared-light/
From above article:
“The visible spectrum includes waves of light that are 400-720 nm long,” said co-author Dr Vladimir Kefalov of Washington University School of Medicine in St. Louis. But if a pigment molecule in the retina is hit in rapid succession by a pair of photons that are 1,000 nm long, those light particles will deliver the same amount of energy as a single hit from a 500-nm photon, which is well within the visible spectrum. That’s how we are able to see it.”

Another avenue of research--a very interesting one ---these guys are trying to "hack" eye senstivity to nIR by changing nutrition---they hope to extend the eyes sensitivity to IR by about 20nm by brute biological force. See: http://scienceforthemasses.org/infrared-project/
From above article:
"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.

Our pigments (photopsin in the cones, rhodopsin in the rods) are comprised of a protein complex called opsin, which is native to the eye, and retinal, a derivative of retinol, or vitamin A (A1). Not all animals with a visual pathway like ours use vitamin A in their pigments, however. Of interest to us, freshwater fish (along with some crustaceans & amphibians) use the pigment porphyropsin, which is composed of 3,4-dehydroretinol, also called vitamin A2, in conjunction with opsin. This photopigment has been shown to be sensitive to light of wavelengths up to 1400nm in some species, which is well into the near infrared range.

Our research has indicated that human beings are fully capable of using vitamin A2 to form our pigments; however, vitamin A1 has a 3-4x greater bioactivity as compared to A2. We believe this to be as a result of both cellular transport mechanisms having a greater affinity for A1, and competitive inhibition (for the layperson, “first come, first serve”).

The aim of the NIR visual perception pilot study is to exploit this opening in the human visual pathway in a brute force metabolic hack. The members of Science for the Masses and a handful of our collaborators will completely eliminate all retinoids and caretinoids (vitamin A and its provitamins) from our diets by switching to a special vitamin A deficient (VAD) blend of Soylent provided to us by special request. We will then supplement with two compounds: 3,4-dehydroretinol (A2) and retinoic acid (RA). Retinoic acid is a derivative of vitamin A which plays a critical role in gene transcription and a host of other systemic processes, and without which we would quickly fall ill and be forced to discontinue the pilot study. Unfortunately, RA has not been shown to synthesize from vitamin A2 in mammals; luckily, however, it appears that there is severely limited intraconvertibility between RA and vitamin A, if any, and so we don’t expect this additional supplementation to sabotage our attempts to hack the visual pathway."

Pretty cool Idea---no?

Why are you interested in attempting to "see", if it can be called that, or detect photon wavelengths outside the visible spectrum?
It is an interesting subject for sure. In any case good luck to you.

Last edited by Encap; 12-05-2016 at 06:20 PM.
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Old 12-05-2016, 06:44 PM #7
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Default Re: Visiblity help!

Okay folks, it's going to be a no-go

-Alex
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