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ArcticMyst Security by Avery

What is the highest wavelength that is visible?

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Just received few days ago this IR 808nm 220mW laser torch /adjustable/burning from O-like.


To my surprise, the dot is quite visible while focused at a short range. At a range of one meter it is barely visible and further more it's invisible.

My quesion is, can anyone here who owns an IR laser, report what its wavelengh and if it is visible?

For instance, is 980nm visible? 1064nm? etc.

I want to know, from people's experience, what is the highest wavelength that is visible?

TIA
 





Trevor

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Even 900nm is probably a stretch. By the time you get to 1064nm, it's completely invisible.

This will vary person to person.

-Trevor
 
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I've heard elsewhere that the limits of our vision is something along the lines of 820nm or so, and that's looking at a bright source really up close (stupid idea).
 
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See:

Color vision - Wikipedia, the free encyclopedia

Skip down to "Physiology of color perception" (close to the top of the page). Look at the graph on the right.

Also, as a matter of interest:

Cool Cosmos

A normal human (or "average" human) should not be able to see 808nm.

There are some exceptions. A given persons retina might have slightly deviant characteristics. I've heard of EXTREMELY RARE cases where a human could see a bit more than "average people" into the IR or UV areas. I've also heard of certain rare conditions (pathologies, eye diseases) that can temporarily "shift" the color response of the human retina.

So...
(1) Most likely what you are seeing is an artifact... a little WEE bit of dim red light spilling out of the diode. I've experimented heavily in B.E.A.M. robotics, using IR LEDs for robot collision avoidance... and SOMETIMES these IR LEDs emit extremely dim, extremely "deep" red light... can only see it in a dark room, looking into the LED.

(2) You are a mutant. Maybe you are one of the X-men!

(3) Do you have two little depressions on either side of your nose? Maybe you are a pit viper. Talk to your parents.

(hehehe .... sorry... I've been up ALL night agonizing over DIY laser tutorials, and I have caffiene poisoning).
 
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Unfortunately, JBTexas, 1) is probably not correct. Diodes have a very small emission band, about 2nm either way. That means that the shortest-wavelength light emitted possible is around 806nm or so.

Regarding 3)... HOW DID YOU KNOW?
 

anselm

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I can see 808nm just fine.
Well, not "just fine" actually, it is very dim, but I can certainly see it.....
 
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I stand corrected then. Or rather sit/slump corrected. I was going by what the graphs indicated. There might be a *definitive* source somewhere that states what the human spectral cutoffs are.

I was sure hoping that I actually talked to an X-Man or human pit viper hybrid.
 
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It's not like our spectrum exactly has a *cut-off*. It's more than our eyes have diminishing sensitivity, and at a certain point, the light entering your eyes necessary to activate some reaction will be powerful enough to damage your eyes. That's where I consider the "cut-off" to be.
 

anselm

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what the human spectral cutoffs are.
I believe it's more like a slope than a sharp cutoff.
It will also vary a little bit for each individual.

there must be an echo in here!:D
 
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Thats what I meant. Semantics. Caffiene poisoning. I didn't mean *exact cutoff points*. "Cutoff" = easier to type than "zone of diminishing sensitivity".

Cutoffs are also what you might end up with when you have an old pair of blue-jeans that you just can't throw away.
 
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Well...

Either I didn't get a 808nm laser from O-like (so what did I actually get?) or that I am a snake.

Fact is that I can see the dot, as I desribed above.
 
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I'd rather go with X-man (possibility of other powers besides seeing IR, slithering quietly, eating rodents).

Sorry. Thread was kind of hijacked. No offense was intended.

Trying to gather ALL of the info to decide whether a DIY laser is a good idea is driving me nutz. My caffiene/hemoglobin ratio must be awful strange now. This is the way I get sometimes with hobbies like this.
 

Trevor

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Generally a large amount of 808nm looks like less than a milliwatt of 660nm. That is to say, it is quite bright.

Hurl enough near-IR photons at your eyes and you'll see red.

-Trevor
 
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Reading this thread, I can already count at least 3 vipers/X-men here in the forum (including me).

If I were a moderator in this forum, I would already begun to worry with such amount of vipers/X-men, LOL.
 
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@Snoutke:
Escher is one of my FAVORITE artists! Definitely one of my biggest influences. I'm working on a project at the moment inspired by some of his illusions. ;)

Sorry for the off topic. :)
 




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