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Halos around beam?

RA_pierce

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I've wondered this for a long time... Why is it that when photographing a red laser's beam, a series of fingerprint-like halos are visible around the aperture? This is what I mean:
 

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I personally think it's a lens reflection.I think it raises the chance of getting those if you have a dirty camera lens.You can also see them with blurry eyes.

Or it could be that the beam is HAUNTED :-X
 
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likewhat

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Or the beam is being clipped as it exits the laser so you get a bunch of rings from diffraction.
 

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likewhat said:
Or the beam is being clipped as it exits the laser so you get a bunch of rings from diffraction.
I don't think so.Those rings are not projected on the same background as the dot.They're always perpendicular to your view(or the camera's view). I still think it's a virtual image created on the lens.That or the beam is haunted or posesed, of course.....
 

RA_pierce

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I don't think it is a dirty lens... My greens don't do that no matter how dirty the lens is. If you go on to Laserglow's customer photo gallery, their Orions do the same thing. Maybe red lasers are coherent poltergeists.
 

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RA_pierce said:
I don't think it is a dirty lens... My greens don't do that no matter how dirty the lens is. If you go on to Laserglow's customer photo gallery, their Orions do the same thing. Maybe red lasers are coherent poltergeists.
I was talking about the camera lens.But are you saying that an equally bright green doesn't do the same? Maybe the camera lens coatings favor red reflections...? :-/ If not, the poltergeist explanation is the only one......
 

Tallaxo

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What you are seeing (or rather the camera) is the interference pattern that the laser produces (ie peaks and troughs) this demonstrates the waves of coherent light. where the waves are in phase they combine to broduce a bright ring, and where the waves are out of phase they cancel each other out somewhat to produce a darker ring, this is what makes the concentric circles effect that you often see through a camera.

Jase
 

RA_pierce

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Oooooh.... Interference patterns... I remember a lesson on that while I was half-sleeping in physics class.

So why don't my green lasers do this?
 

Tallaxo

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RA_pierce said:
Oooooh.... Interference patterns... I remember a lesson on that while I was half-sleeping in physics class.

So why don't my green lasers do this?
They do, but as the wavelength is so much shorter, it is very difficult to see, the effect is only apparant with longer wavelengths such as your red , the deeper you go into the red spectrum (660-670 nm) the greater the spacing of the wavefronts and the easier it is to see :)

Jase
 




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