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Strange optical haze from laser

Phazonx

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Why is it that when you look at a laser dot or a scattered one that you see a mixed black and red pattern?
 

Hemlock_Mike

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That effect can only be seen with laser type light.  What that is amounts to the peaks and dips you see in water if you drop two stones in to the puddle.  
With light, the waves are interfering with peaks and nulls - the nulls appear black.

Mike
 

Angdvl089

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Hemlock Mike said:
That effect can only be seen with laser type light. What that is amounts to the peaks and dips you see in water if you drop two stones in to the puddle.
With light, the waves are interfering with peaks and nulls - the nulls appear black.

Mike
We call that crest and trough over here :)
 

flogged

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Known as 'speckle' it's caused by the coherent nature of laser light. Meaning the beam of light is all in phase. So when you reflect the laser of objects the speckle is caused by interference effects. The same principle that makes holograms possible.
 

Hemlock_Mike

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Yes -- Crest and trough are also descriptive terms I've heard used for this.
Where's "over here" ???

Mike
 

Hemlock_Mike

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I live near the edge of a 3600 acre pond -- Clear Lake, Iowa ;D
No joke -- This pond which they call a lake is about 7 feet deep average :eek:

Mike
 

Benm

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All lasers should do this. The presecense of speckly is a good way to tell the difference between an uncollimated laser diode operating below and above lasing treshold.
 

Skram0

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Aw yea.. http://en.wikipedia.org/wiki/Speckle

"The formation of such a speckle pattern is due to the high coherence of the laser light. Since variations in the surface are greater than the wavelength, coherent light scattered by the individual elements of the surface interferes to form a stationary pattern. The speckle pattern appears to scintillate or sparkle when there is any relative movement of the surface and the observer."

Check out the 'Eye Test' section and see which you are.
 

Thories

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Hemlock Mike said:
I live near the edge of a 3600 acre pond -- Clear Lake, Iowa ;D
No joke -- This pond which they call a lake is about 7 feet deep average :eek:

Mike
little off topic but...

i went to a lake to canoe a few months ago. bout 2 ft deep right the way across.... then we got to the river which dropped off suddenly...... kinda funny to see people walking their canoes into the river and it starts dropping and they suddenly decide to get in .... well it ends with some poor person getting pulled along by a canoe with the other person laughing their ass off :). school trips are fun :).
 




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