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03-01-2011, 08:11 PM #1
 Class 1 Laser Join Date: Sep 2010 Location: Athens, Greece Posts: 54 Rep Power: 7
Fivos
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Laser Divergence Info

Laser Divergence Calculator
Example of an almost accurate aligned laser. A 473nm 50mw laser..

Hope you liked my project...
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Last edited by Fivos; 03-01-2011 at 08:14 PM.

03-01-2011, 08:49 PM #2
 Class 4 Laser Join Date: Sep 2007 Location: Wisconsin Posts: 8,854 Rep Power: 1363
Cyparagon
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Re: Laser Divergence Info

I like working with ones better. Here's something a little more simple. If a laser diverges 1mm in 1m, the tangent of the angle would be equal to 1/1000:

tan θ = 1/1000
θ = arctan(0.001)

Follow the steps backward to see that 2mrad just means it diverges 2mm for every meter.
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03-01-2011, 09:34 PM #3
 Class 3R Laser Join Date: Jul 2010 Location: Olomouc, Czech Republic Posts: 1,517 Rep Power: 81
DrSid
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Re: Laser Divergence Info

Doing arctan of angles bellow 1 degree is redundant. It results in almost the same number.
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03-01-2011, 10:15 PM #4
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chipdouglas
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Re: Laser Divergence Info

Quote:
 Originally Posted by DrSid Doing arctan of angles bellow 1 degree is redundant. It results in almost the same number.

I am probably the worst person at math here but if the numbers are "almost" the same, how is it redundant?
i'm not being a smart ass. just looking for an explanation.
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03-01-2011, 11:35 PM #5
 Class 3R Laser Join Date: Jul 2010 Location: Olomouc, Czech Republic Posts: 1,517 Rep Power: 81
DrSid
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Re: Laser Divergence Info

Quote:
 Originally Posted by chipdouglas I am probably the worst person at math here but if the numbers are "almost" the same, how is it redundant? i'm not being a smart ass. just looking for an explanation.
It's redundant for most uses .. the difference is too small. For laser divergence for example it's irrelevant if it is 0.001 or 0.00997.
So if you make one measurement of beam diameter at large distance, all you need for divergence is size/distance (both in same units, result in radians).
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03-02-2011, 12:35 PM #6
 Class 1 Laser Join Date: Sep 2010 Location: Athens, Greece Posts: 54 Rep Power: 7
Fivos
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Re: Laser Divergence Info

I didn't know. I'll do some more tests....Thanks...

03-02-2011, 08:55 PM #7
 Class 4 Laser Join Date: Sep 2007 Location: Wisconsin Posts: 8,854 Rep Power: 1363
Cyparagon
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Re: Laser Divergence Info

Good point, Dr. Sid. I was going to add that, but I forgot.

You'll see that for values close to zero, the graph of tangent is virtually linear. That is to say y ≈ x.
tan θ ≈ θ

The same is true of sine.
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Last edited by Cyparagon; 03-02-2011 at 08:57 PM.

03-02-2011, 09:22 PM #8
 Class 3R Laser Join Date: Jul 2010 Location: Olomouc, Czech Republic Posts: 1,517 Rep Power: 81
DrSid
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Re: Laser Divergence Info

I use different explanation. And that is: what does radian actually mean ? Well .. it measures the 'arc'. If you take pie section of radius 1, its curved side will be of the same length as the angle of the pie in radians. Full circle will be 2*pi.
Now imagine very thin pie section .. it's clear that the curvature has little effect on the length of the side opposite to the angle. Also as the central angle gets small, the other two angles are getting close to 90 degrees. So all height of the triangle, length of the arc, and length of the side opposing the central angle are becoming very similar .. and equal to angle in radians itself.
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