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Halo Around Dot?

Wolfman29

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Hey everyone.

Been wondering this for a while... for all of my lasers, there is a wide-angle halo around the dot. It can really only be seen when you point the laser at something close by (that way the halo is the smallest it can be), but it's certainly there, and there is certainly a power reduction because of it. Does anyone know what this halo is, where it comes from, and how to get rid of it?
 

Wolfman29

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Acetone, rubbing alcohol, etc.

I think it's more due to the shape of the lens or something than being dirty, because it's a PERFECT circle. Lemme take a picture of it.

EDIT:



Here ya go. It's not the camera's artifact (the upper left circle), but the really bright one near the dot.
 
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Trevor

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Has it always been present?

There's always going to be some scatter. ><

-Trevor
 

Wolfman29

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As far as I am aware, it has been. if this is normal for lasers, then I guess I will live with it, but it just doesn't seem normal.

EDIT: By the way, it's about 30 degrees off axis all the way around.
 
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Trevor

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Seems like just imperfect optics. Better AR coatings and higher end optical glass go a long way to fix that, but it comes with a really high price.

...and often says "Coherent" on the side. :p

-Trevor
 
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To me it looks like a reflection from inside the host.
Try painting it with flat black paint
Or a reflection off the edge of the lens.
 
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JBTexas

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Dunno... I see this with itty bitty laserpointers too.

I think Trevor hit on it... SOME scatter, perhaps from the clear epoxy or whatever the diode thingy is made off (It CAN't have an IOR of 0.0, CAN'T be "perfect")... and the other optics can't be ABSOLUTELY perfect either.
 




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