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FrozenGate by Avery

What is the longest wavelength of laser light you have seen?

I'm definitely going to want a monrochomator or a spectroscope, preferably something very inexpensive. A laser may have a narrow bandwidth, but you can never be sure where the peak is, and it usually has a long, dirty tail. If a portion of the tail is at a wavelength to which our eyes are far more sensitive than the peak, then we may mistake the tail for the dog.

By the way, pages 93-94 of this book (below), especially the chart at the top of page 94, is pretty interesting. It says that above 600nm the sensitivity of the blue-cone is so weak that our vision is essentially dichromatic, i.e., red-green. However, since red and green sensitivity taper off at different rates, there are places where we see the exact same color at two different wavelengths. For example, 800nm looks exactly the same as 663nm, since at both wavelengths the R/G ratio is 12. (That might explain why my 808nm laser pointer looks like what I imagine 670nm ought to look like.)

Color Vision: From Genes to Perception - Google Books
 





The way our brains perceive so many colors from three wide-band sensors is quite amazing.
 
I could see the dot on my 808nm IR pen I had and it was only 350mW
 
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I finally got my 300mW 808nm laser pointer. The dot is clearly visible in a dark room. I also got a 5W 940nm flashlight. The light is visible in a dark room only when shined directly into the eyes, or when viewed in a mirror, or reflected off polished metal. When shined on anything else, even brushed metal, nothing is visible.

The color of the 940 is more orange than the 808, even more orange than 650. According to infrared color reversal theory, 808 should look like about 661-62, 940 should look about like 645. In order to test the validity of this theory I will need more light sources for comparison.

First I'd like to get a 1mW 670nm laser (once ubiquitous, now impossible to find at any price). If the 808 looks halfway between 650 and 670, that will be a good sign.

Next, I will a need a source of 640nm light. If the 940 looks halfway between 640 and 650, that should clinch it.

Until I conduct further experiments, I will have no way of being sure that I am actually seeing the peak wavelength, as opposed to the long dirty tail of the curve on the down side.

And finally, I got a 1W 365nm flashlight. The visible light looks just as it should: dim, a mixture of about 95% gray, 4.5% blue, and 0.5% violet. According to the theory of uv color reversal, that's just what pure 365nm should look like. I tested the flashlight on a Canadian $5 bill, a British £10 banknote, my drivers license, and a credit card. Even though the banknotes have certain security features that are visible under all kinds uv, all four items have certain other security features that only clearly visible at 365nm ±5nm.
 
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635nm is fairly close to 640nm in color and is readily available. Aixiz may still have a 670nm, I can't remember but it is worth a look.
 
I can see a faint dot from a 820nm labeled 25mw.

I think above 800ish to about 850 (maybe higher), visable is relative to power output and collamination.
 
I see 808nm, I have no longer. I think possible to see some longer nm. May be 900 or so..
 
Does anyone have both an 808nm and also a 670nm or 671nm DPSS? I've already tested the theory of infrared color reversal by comparing 940nm with 650nm. The theory predicts that 940nm should look approximately like 644nm, and it certainly looks more orange than 650nm to me. This same theory predicts that 808nm should look more red than 650nm but more orange than 670nm.

I suppose I should really be doing this experiment myself. Sigurthr mentions that AixiZ may have a 670nm, and sure enough they do: a 5mW 670nm laser module for $6.50 (670nm 5mW laser module 3VDC adj. lens 670 nm 8 X 13 mm, AixiZ) I've never built a laser before and have been putting off acquiring this valuable skill. This unit takes 2.8-5VDC and seem to have the driver already built in, so I really have no excuse.
 
Here is a pic of me seeing 10nm lasers.
ltly.jpg


Just kidding
 
zyxwv99 said:
Does anyone have both an 808nm and also a 670nm or 671nm DPSS? I've already tested the theory of infrared color reversal by comparing 940nm with 650nm. The theory predicts that 940nm should look approximately like 644nm, and it certainly looks more orange than 650nm to me. This same theory predicts that 808nm should look more red than 650nm but more orange than 670nm.

I suppose I should really be doing this experiment myself. Sigurthr mentions that AixiZ may have a 670nm, and sure enough they do: a 5mW 670nm laser module for $6.50 (670nm 5mW laser module 3VDC adj. lens 670 nm 8 X 13 mm, AixiZ) I've never built a laser before and have been putting off acquiring this valuable skill. This unit takes 2.8-5VDC and seem to have the driver already built in, so I really have no excuse.
Click to expand...

Tried to buy that one and 3 other red/ir modules and after checking out on paypal it got back to an empty cart page. Purchase doesn't show up on PP either... WTF?
 
I've had that experience with a number of budget Chinese places, especially if it's anything to do with lasers. I read in some discussion forum that PayPal doesn't like lasers. All of my orders eventually went through. Usually you get an email 12 hours later from some Chinese company you never heard of, asking you to confirm a PayPal order for "goods" or "gift." It's for the exact same amount as what you ordered in the first place. If you OK that, about 12 hours after that you get an email telling you that the product has shipped. When you get the package, the return address is some other Chinese place. In the end, everything works out just fine. Mysteriously, but just fine.
 
I can see 500mw 808nm in the room (overcast skies) with no problems....
Looks like dark red.
 
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300mw of 830nm in daylight small dull dark red spot but enough to focus on just to get it to burn
 
I just found this:

The foveal sensitivity to several near-infrared laser wavelengths was measured. It was found that the eye could respond to radiation at wavelengths at least as far as 1064 nm. A continuous 1064 nm laser source appeared red, but a 1060 nm pulsed laser source appeared green, which suggests the presence of second harmonic generation in the retina.

Visual sensitivity of the eye to infrared laser radiation
David H. Sliney, Robert T. Wangemann, James K. Franks, and Myron L. Wolbarsht »View Author Affiliations
JOSA, Vol. 66, Issue 4, pp. 339-341 (1976)
Optics InfoBase: Journal of the Optical Society of America - Visual sensitivity of the eye to infrared laser radiation
 
Medical infrared YAG 1320nm totally invisible. (not mine)
 
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