What does Divergence mean could someone explain

[LASERFUTER_1]

Does divergence mean the size of the beam at a given distance ?

 

[Switch]

Re: What does Divergence mean could someone explai

dude seriously....what's with this question? : Look in a dictionary, "divergence" is a pretty common term.

 

[New_Reverie]

Re: What does Divergence mean could someone explai

divergence is a measurement of the rate at which the diameter of the beam changes for fixed focus lasers, or when your laser is set for focus infinity.

Also there are usually two measurements for divergence, X and Y divergence. This is because most laser beams are not perfect circles and so the beam diameter changes at a different rate in both the X and Y direction.

Divergence is a function of beam diameter and focal length. The formula is actually very simple, it is simply D/F Where D is the diameter in either the X or Y direction (like i said above there are actually two measurements for divergence) and F is the effective focal length of the lens for the wavelength of the laser beam is being shot through (note that different wavelengths diverge in different ways, that is why a prism will split white light into a rainbow). This only works when the laser is cast on a surface that is a distance of Fb from the lens, where Fb is the focal length of the lens.

There is one thing to add here and that is some laser setups use more than one lens. The formula and explanation above is designed for a singe lens system.

We can use math (horray!) to create a different formula to measure divergence in this case. First we cast the laser beam on a surface and measure our beam diameter, D1. Next cast the laser on another surface some distance X further from the original surface and measure the diameter again D2. the formula now becomes deltaD/deltaX or (D2-D1)/X where X is the distance between the two surfaces.

Here you can see what divergence really means. It is the change in beam diameter over distance traveled. Also something interesting to note is that this value is actually unitless because all we are doing is dividing one length by another. We measure divergence in radians which is basically the angle at which the laser beam exits the final lens. A divergence of 0 would mean the beam would travel straight forever!

I hope this over explanation of divergence answers all your questions and more!

 

[Switch]

Re: What does Divergence mean could someone explai

You know... "Give a man a fish and he will eat for a day. Teach him how to fish and he will eat for a lifetime."

You just gave him the fish :

You have a very in depth explanation of divergence , in particular when it comes to laser beams.But the basic definition is "the act of moving away from a point in different directions" i guess :-/

 

[New_Reverie]

Re: What does Divergence mean could someone explai

except that is not what divergence is in the case of lasers. Divergence for a laser beam is the angle at which the beam expands away from the direction that it is pointed. Your definition explains what divergence means, not what it is.

 

[john_lawson]

Re: What does Divergence mean could someone explai

Ok before this gets out of hand I suggest we stop this right here in its tracks

we are all friends on here ,lets not get into a rumble if we can avoid it please

its the holidays man ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D

 

[New_Reverie]

Re: What does Divergence mean could someone explai

an update, it turns out that even my full understanding of divergence was wrong, in terms of the calculation, not the fact that it is the angle at which the beam 'diverges' from the center. The correct equation is below

It turns out that divergence should be twice the angle that the beam and the center line make...

http://en.wikipedia.org/wiki/Beam_divergence


And more interesting material!!
http://en.wikipedia.org/wiki/Gaussian_beam

 

[john_lawson]

Re: What does Divergence mean could someone explai

Here it comes :-?

 

[New_Reverie]

Re: What does Divergence mean could someone explai

Here it comes :-?

also Merry Christmas!

 

[john_lawson]

Re: What does Divergence mean could someone explai

Now thats better !!  ;D ;D ;D I feel bad Cause 10 months ago I was asking
all those noob questions too ,I am far from knowing too much in fact now i read like hell just so somone wont say hey look freaking here or look freaking there
we are all here to help each other ..well thats my outlook anyways .............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................



oh and I still dont really know how to measure divergence as long as its not 5mm out of my Rpl I'm one happy camper  ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D

 

[New_Reverie]

Re: What does Divergence mean could someone explai

http://www.pseudonomen.com/lasers/calculators/mRadCalculator.html

 

[john_lawson]

Re: What does Divergence mean could someone explai

Hey thats coooool thanks!!!!!! ;D

my RPL is .93 mrad

 

[Ace82]

Re: What does Divergence mean could someone explai

*post deleted*   :-X


I guarantee you that this information is EASILY acquired here on LPF without starting ANOTHER thread, but who the heck am I to judge and come jumping in speaking my opinion?  :-X  And New Reverie, your information is much more positive and useful then mine or Switch’s, cool.    I personally have just gotten tired of newbies (no offence) expecting to get "spoon fed" their info, but if there's someone out there willing to spend the time to do it, then I guess anybody who isn't, should just  :-X.  So I rest my moral case for the day.  


Happy holidays.  

 

[davidgdg]

Re: What does Divergence mean could someone explai

Let's not forget negative divergence ;-)

 

[Switch]

Re: What does Divergence mean could someone explai

Your definition explains what divergence means, not what it is.

Well i dunno, the definition is supposed to explain what a word means , and what something is. :-/ I find that my definition of divergence fits pretty well with lasers.Though divergence is not an angle.The angle we are measuring is the angle of divergence, and we just call it "divergence" for short.