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Laser Spirograph Color Shifting

awlego

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Oct 9, 2009
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So today I was playing with my 2 mirror spirograph using both a single green module (unknown power est. 50mW) and my adjustable RGV when I noticed something odd. When I used the spirograph to make shapes with the laser, not only did the design change, but the color appeared to change too. Compared to a normal dot of the same 532nm green DPSS, the shape made with the dot was much more yellow. Not completely yellow, but enough to notice with the naked eye. Then I tried using other green lasers of similar brightness to the shape being generated by the 50mW green and indeed the shape appeared more yellow than the single dot of green.

Anyone else ever experience this? Can anyone explain why it appears to be more yellow when spinning?

I know they are all EXACTLY 532nm and temperature/diode can't be a factor because they are DPSS. So differences between the lasers cannot be a factor. Nor is power a factor since I tested the same laser with and without spinning as well as 2 lasers next to each other with matched perceived brightness. My only idea is that somehow because the dot is moving along a white wall very quickly some of the white wall comes out and my brain interprets the two as a more yellowish color since it is moving so quickly, where as the single dot is there all the time and I can't see the wall behind it...

I'm just throwing ideas out :can:

-Awlego
 





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Jun 9, 2009
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Could this be Doppler Shift? -

Redshift - Wikipedia, the free encyclopedia

- Seems unlikely you'd notice it at the relatively low speed but it's the first thing that springs to mind.

M
:)

most likely not. redshift is caused by something headed away from you over longer distances, even then, it would be a shift of something extremely miniscule, yet the effect greatens over distances of light years.
 

LSRFAQ

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See it before with very bright green lasers and watching bright scanned images too long.

Shows up as short pulses of orange, and its a eye chemistry thing.

I do not know the exact mechanism, but no, your not nuts.

Steve
 
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Apr 12, 2010
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whatever mirror you are using im sure is causing this, that or optics.

i.e. aluminized FS mirrors EAT red.
 
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Aug 12, 2009
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Don't doubt it. The wavelength is not changing.
IMHO for sure is a optical, eye-related effect that has something to do with POV (Persistence Of Vision) or perhaps with iris opening. I mean, If you look at the single dot, all the luminance is going through you iris making it to close for compensation. If you look at very quick moving beam your iris will be less closed, thus taking into your eye more light and besides the environment colors making it to you more brilliant.
 
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Apr 12, 2010
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Don't doubt it. The wavelength is not changing.
IMHO for sure is a optical, eye-related effect that has something to do with POV (Persistence Of Vision) or perhaps with iris opening. I mean, If you look at the single dot, all the luminance is going through you iris making it to close for compensation. If you look at very quick moving beam your iris will be less closed, thus taking into your eye more light and besides the environment colors making it to you more brilliant.

boom! a nice logical answer (who cares if its correct) lol that can sum up what i was trying to say, without needing to employ any effort.

i am also saying that different optics, mirrors, materials, coatings, will have different effects, as well as continuing effects on the entire beam, no matter where it goes.

just... dont look into it to see why its a brighter yellow.
lol
 




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