how do you work out mrad of a laser

how do you work out the divergence of a laser ? if you started out with a beam at 5x5 mm and the beams 12x12 at 8m whats the divergence for that laser ?
just one of those things i want to learn:)

go back to you trig. from school
I think its the same as calculating scan angles except using smaller values that translate into fractions of degrees.
You should be able to use the formula thats used on the pango scan angle page http://www.pangolin.com/userhelp/scanangles.htm
though you may need to take into account that you are starting from 5mm instead of zero - Im very rusty on this too!

Rob

Beam divergence formula:
http://upload.wikimedia.org/math/8/8...68f157a6e2.png
Where Df and Di are the beam diameter at two separate points and l the distance between them.

In your case I get 0.9 mrad. Remember to have everything in SI units.

Just write it like this in google: http://www.google.se/search?q=2*arct...-0.005)%2F(2*8))

found an easy way to work it out
http://www.pseudonomen.com/lasers/ca...alculator.html

that saves damage to the grey matter:)

there used to be a GREAT calculator floatin around somewhere for this...

wish i remembered:rolleyes:

-Marc

**EDIT**---oops, just saw your post above! lol...there ya go! :)

you put a razor blade on a micrometer stage, you measure the total power of the beam, you insert the razor blade until you are at 82% of origional power. you note the measurement, you then decrease the power to 13%. You PM mixedgas and make him post the %$#$@ approximation equation, you plug and chug some junior high school math. Voila, gaussian beam diameter at one point. Then you do it again 1 meter / 1 yard down the beam. You plug and chug the second set of the numbers into a (*&^ing 9th grade equation. Voila , divergence. Or you buy a system from sphericon, or you send your laser to mixedgas and he uses his sphericon. Sphericon systems use a calibrated CCD camera without a lens on a slidning rail. They do a hell of a lot more then measure divergence.

Steve