Beam color difference between DX and CNI 532nm

[zerafiel]

I noticed a difference in beam color between my NL X-85 and my DX200 laser.
Under NL's sport elite goggles, the x85 dot appears green whereas the DX dot has a slight orange/yellow tinge to it.

Is this indicative of IR leakage from the DX laser? Any thoughts will be welcome. Or if anyone has a cni pen and a powerful enough DX laser, you can try to corroborate this observation. Or trying this out with a WL Fusion would be interesting as well.

 

[Chris.]

I'd guess it's the lower quantity of green light emitted by the DX(due to higher IR, like you said) causing a difference in colour perception, somewhat like changing the opacity of a single colour in Photoshop.. It is in theory exactly the same colour, there is just less of it.

 

[Rhith]

Hmm, my guesses are because of the lower GREEN LIGHT (Not talking about IR Leaking at all) at when you look at the light it blends with the shade of red you see over everything giving the illusion that it is truning a tint of orange. When I get home I'll check this out too both with laser shades, sport elite goggles and between my True 5mW, True 30mw and ~115mW CNI.

 

[zerafiel]

Both laser are >100mW so I can't say if it is more green output coming from the CNI. If anything, I think the DX200 puts out more power than my 100mW X-85 burning wise. Noticed this awhile back but never got around to posting it.

So I don't really think the less green from DX argument makes sense. Perhaps the DX laser operates at a higher frequency than 532nm(unlikely) or there is some NIR leakage which at 808nm can have a faint red glow iirc.

Interested to know if you will get the same effect as me with dx30/50, dx200, cni100mw.
But I think through WL lasershades, the beams should all look green since they do let more green through than the nova shades.

 

[Rhith]

Ah, I didn't realise that it was a DX 200mW.

Hmmm, not to sure what to guess with this one then. IR shouldn't effect the dot color like that though I would think sicne at a distance it would diverge so much that it wouldn't be focused enough at the projection point. Could be a slight shade variation in the IR filters of both units or imperfection in the crystals. I am sure there are slight variations in the shades of lasers no matter what, two CNI's produced one after another would even have completely different characteristics so you can never be too sure.

 

[Benm]

I've tried with a DX30, and there is some IR light leaking out, but in a wider pattern than the green. Up really close (shining onto a paper 1 inch away) this red light -is- visible on the paper.

However, i could only see it with a lowpass filter that blocks the green to a great degree (a factor of 100 or so). Even after the filter the green was still brighter than the ifrared, but since the infrared dot is much wider i could still see it.

Notice that i'm looking at reflected light off a piece of paper here - i'm sure the infrared light would be very well visible looking into the laser through the lowpass filter, but i'm not gonna try for obvious reasons.

 

[zerafiel]

My color difference was noted on a black background. I don't remember there being an observable difference on a white background but I didn't check that explicitly.

Anybody knows how different 532nm can look +- 10nm? Or maybe +-5nm is sufficient to produce a visible color difference.

Alright a picture tells it all...
X-85 vs DX200 taken through Nova sport shades from 3" away on a black plastic board
Notice how the dx200 dot appears a faint pink/red on camera almost like the color of NIR.
But to my eye, this pinkness is not so apparent. Actually, both dots look about the same except the dx200 dot has a very very slight red-pink tinge. Hard to notice unless I think about it.

I am taking this to mean the dx200 leaks quite a significant amount of IR compared to a CNI-pen. At least sufficient to overpower the <1mW green going through the NovaShades.

Disappointing really if all that great burning power from the DX200 was mostly from the IR leakage.

 

[Benm]

Anybody knows how different 532nm can look +- 10nm? Or maybe +-5nm is sufficient to produce a visible color difference.

A 5 nm difference would probably be observable when compared side by side. This is however not a possible cause for what you describe: 532 is the product of exactly doubling the 1064 nm line from a Nd:YVO solid state laser. The gain bandwidth of the Nd 1064 nm line is under 1 nm.

I'd say it's just IR leakage, though i'm surprised it's such a small dot compared to what i've seen from similar lasers.

 

[Aseras]

IR to a camera though isn't equal to what IR to the eye looks like. the IR leakage is almost imperceptible. I think it's more to do with fluorescence than ir leakage. with goggles on it's very easy to see things light up. depending on th quality of the surface you could see more or less. try hitting diffrent surfaces around your house with the lasers and compare them all to each other.

 

[zerafiel]

IR to a camera though isn't equal to what IR to the eye looks like. the IR leakage is almost imperceptible. I think it's more to do with fluorescence than ir leakage. with goggles on it's very easy to see things light up. depending on th quality of the surface you could see more or less. try hitting diffrent surfaces around your house with the lasers and compare them all to each other.

My camera was on auto mode and not night mode or anything. The two spots are hitting the same black surface. So if that isn't IR I am not sure what it could be because both lasers are supposed to be 532nm.

The color difference is also perceptible on other dark surfaces when looking through my nova shades.

 

[TheMonk]

Xarylx, can you place an IR filter in front of the DX beam just to see if the color change.

 

[zerafiel]

After placing an ir filter pilfered from a webcam the red/pink tint is gone. I don't really have the right equipment to test this but the reddishness pretty much disappears and now the dot color is the same for both the x-85 and dx200+filter view through nova shades by my camera on auto mode.

This dx200 is not the tested 179mw one but another one I bought because I couldn't resist it when my x-85 was in warranty repair

But visually it is has a much brighter and more visible beam than my x-85 which nova recently measured to average 104.7mW. Burns better as well. I'd estimate the power to be over 150mW maybe slightly less after filtering and maybe less after more runtime. I quite love playing with this over my x-85 simply because it has such a nice beam and I don't mind accidentally spoiling it.

Still the IR is rather worrying. I will probably make the webcam filter a permanent fixture.

There is a lens after the filter which i hadn't removed so the beam is expanded

 

[zerafiel]

Nova X-85 with the same filter.
Note that more flaring is captured for this beam then for the previous pic. might just be the camera or that the dx200 is inherently brighter after both beams are filtered

 

[zerafiel]

Another pic of dx 200 through filter+lens.
Note the green leaking through the edges of the nova shades.

 

[zerafiel]

Anybody knows how different 532nm can look +- 10nm? Or maybe +-5nm is sufficient to produce a visible color difference.

A 5 nm difference would probably be observable when compared side by side. This is however not a possible cause for what you describe: 532 is the product of exactly doubling the 1064 nm line from a Nd:YVO solid state laser. The gain bandwidth of the Nd 1064 nm line is under 1 nm.

I'd say it's just IR leakage, though i'm surprised it's such a small dot compared to what i've seen from similar lasers.

Thanks for the input. Interesting that a 5nm difference is readily observable to the human eye. Also good to know that the frequency doubling is quite precise for dpss lasers. so technically all filtered DPSS greens should have the same color.

Picture was taken at 3" from aperture and the dot is larger then the X-85. So the divergence is probably larger and at distance the beam width would be pretty big to negligible. So at close range the IR would probably contribute significantly to burning power.

Furthermore, that picture is not taken in night mode and there might be more IR leakage not captured by the camera or filtered by the nova shades.

Another explanation I've been considering is color mixing between 532nm and the NIR lines of 808nm and/or 1064nm. Usually people ask of color mixing of visible wavelengths but I read a thread here debating on the visibility of NIR. So after having most of the 532 filtered out by the novashades, it combines with the NIR lines to produce the slight red/pink tinge.

Someone mentioned that it is easier for colorblind ppl to see NIR. Well I am partial color blind(red-green) so maybe it helps me notice this color difference although I would think it might have the opposite effect instead.

 

[Benm]

Thanks for the input. Interesting that a 5nm difference is readily observable to the human eye. Also good to know that the frequency doubling is quite precise for dpss lasers. so technically all filtered DPSS greens should have the same color.

Mind that this is highly dependant on wavelength... but 532 is in the optimum range of human vision, where slight differences in color are visible because they are around the optima of both the M and L cones, and also on the edge of the S cones range. If you had 527, 532 and 537 nm light sources they'd all appear perfectly green on their own, but side-by-side you would (just) be able to tell them apart.

This does not work around the entire spectrum though, telling 640 and 670 nm apart is impossible depsite the 30 nm difference. At equal power 640 nm would appear much brighter, but identical color.

Your colorblindness could be a major factor in your observations however. The most common cause of partial color blindness is a modification in the M cone, which results in a different response for that cone. This will also affect the M/L ratios for all colors, and could allow you to see color differences that other people cannot.