Core's divergence?

hi all, i just wanted to know if anyone has tested the cores divergence, as i had a go at pseudo's calculator, and i got about 0.2Mrad? is this good?
thanks

it's not .2 mrad..

My core is ~.8 mrad that's about as good as most pointers will get.

well that's what pseudo's calculator said???maybe i should try again?

I believe it is somewhere around .2 mRad, my old leadlight had amazing divergence (Right now it doesn't work for some reason, I hope I can fix it) it was something like .3 mRad on Pseudo's calculator, I wish my CNI had divergence like my leadlight.

so is higher Mrad better, or lower? hmmm i'm still not sure how accurate the result was???

You want lower. Divergence refers to how fast the beam expands over a distance. To get a good idea, I think if your lasers divergence is "x," you can multiply x times the distance in meters to get the approx. added diameter of the beam in mm.

Ex.
Divergence: 1.2mRad
Initial Beam Diameter: 2mm
Distance: 100m

1.2 * 100 = 120mm

Add the initial beam diameter in and you get a dot size of 122mm ~ 12.2cm

You want the mRad number to be as close to zero as possible for beam to stay tight over distance. The higher the number the more it diverges, meaning spreads out over distance. If it is a negative number ( such as WL Pulsar's beam) it will converge first and than continue to spread out.

If divergence, (or better say collimation in this case) is 0mRad (which is physically impossible) the diameter of the beam at the source would be the same over infinite distance.

My two Cores have 0.7mRad which is quite good.

RASEL Ur correct
A good LASER will spec. at  near .8 mRAD which =  A  .8 meter spot size at 1000 meters distance (.0008X1000)

KEYWORD: milliradians ,1/1000 of 57.xx degrees

A collimeter at the LASER output will reduce beam spread by several times.

See member Stevetexas. He has one that cost $550, a M/G. Wish I had one too!

Coll. should have AR coatings(anti reflection) on 1st lens concave and 2nd convex(spread beam then collimate)

LASER beam>----[)--=(]======TARGET

If the beam is polarized circular at first, all the better

:-?QUES::: 1. Does anybody know the best way to convert a beam to circular polarization?

I read to pass the LASER through a 1/4 wave plate w/side or inline ......... "I don't understand" I think most Greenies are randomly polarized.
:-?Ques.: 2. Agree?

Cheers ---->*<
[smiley=beer.gif]

FACT: A focused beam that's circ. pol. won't reflect back to the source w/harm.

Laserrod said:

RASEL Ur correct
A good LASER will spec. at near .8 mRAD which = A .8 meter spot size at 1000 meters distance (.0008X1000)

KEYWORD: milliradians ,1/1000 of 57.xx degrees

A collimeter at the LASER output will reduce beam spread by several times.

See member Stevetexas. He has one that cost $550, a M/G. Wish I had one too!

Coll. should have AR coatings(anti reflection) on 1st lens concave and 2nd convex(spread beam then collimate)

LASER beam>----[)--=(]======TARGET

If the beam is polarized circular at first, all the better

:-?QUES::: 1. Does anybody know the best way to convert a beam to circular polarization?

I read to pass the LASER through a 1/4 wave plate w/side or inline ......... "I don't understand" I think most Greenies are randomly polarized.
:-?Ques.: 2. Agree?

Cheers ---->*<
[smiley=beer.gif]

FACT: A focused beam that's circ. pol. won't reflect back to the source w/harm.

Click to expand...

Laserrod, I always thought this was what a collimator did:

LASER beam>====(]==[)---------TARGET

Doesn't that seem more logical? Wouldn't you want the beam to be more concentrated for burning?

In your diagram the beam would collimate with the first lens and spread with the second one.

Gazoo said:

In your diagram the beam would collimate with the first lens and spread with the second one.

Click to expand...

Oh yeah :-[

So I guess a collimator can collimate to a bigger and smaller diameter beam?

collimators first widen the source for easier collimation. Then the lens collimetes it to the better degree.

here is pic of couple pretty big collimators in my stash. White one I build and it outputs about 8mm of Core's beam. Black one is a simple scope finder for telescope and it outputs as low as 0.2mrad of green but the diameter of the beam is close to 10mm.
The more collimator widens the beam first, the better it can collimate it.

Milos,
Well said.

The point I was tring to convey is; if you 1st lens the beam to spead out for a short distance(@lens focal lenth) and then lens it back to parallel, you will acheve a beam that spreads out much less over distance!

I was using my $30 Russian made 20x50 telescope outside this morning with a 100 mW greenie and it seemed to make a real bright sparkly spot on a garage door 4 houses away.

Now to get (this set up) the Coll. beam to light a match at 100 meters!

Member Stevetexas has pioneered this act. Search forum for "match at 300 feet" or somthing.

Good pics., thanks Milos, looks like a homebrew collimater.

[smiley=beer.gif]

Here's a thread I started a few months ago. Your divergence figure will be more accurate if you use long distances.

http://www.laserpointerforums.com/forums/YaBB.pl?num=1184011673/all-0

Here is the bottom line on collimaters:

You use them to reduce your spot size at a distance. otherwise; the spot size would be bigger at a distance.

But we here at LPF want to focus the beam for highest power density!!!
Yes, we need more power density at distance!!
So if we make the beam spot bigger from the get-go, it will end up smaller at the distant target than otherwise. Hope you all are still with me here.
But
Even after expanding the beautiful raw parallel beam with a coll./telescope to a bigger paralel beam to any diameter, then try to focus at target at the coll./telescope we will not be able to get a higher power to area density ratio (burning power) .
So we either:
1. focus the raw laser beam(w/no coll./telescope) at the target location with a lens diam. same as beam waist.( I think this would give highest power but the beam is real big) Thats more volume of air the beam must penitrate??

Or
focus the LASER through a telescope/collimator (will resultin a beam spot smaller than the raw laser beam at distance)with a lens right at the target location.

Remember that we want the higest power density at distance.

Does anyone think this can be done (highest power density)without using a third lens at the distant target?

[smiley=evil.gif]

Collimators.

It is really just a telescope with 2 lenses.

You spread the laser beam then you make it parallel again to make the spot smaller at a distant target. Simple right?

Cons. reflected light from the lenses is wasted because it won't hit target. But the result is beam with more circular polarized power.(we want light waves that are perpenticular to the beam axis)
The beam waist is enlarged by the device and the beam won't be as visable as is passes by our field of view. A bigger beam waist means less power density.

Pros;
The device makes the beam behave and more parallel.
The distant target will recieve a higher power density.
You get a brighter spot at target just because it will be smaller than otherwise.

Clear as mudd right? [smiley=lolk.gif]