Opt Lasers 6X Cylindrical Testing

I still think you must be focusing that beam to a tiny spot 50 feet away, amazing you can do that with your setup, but if focused to a point, then the beam isn't at infinity focus. If so, the measurements you are making has nothing to do with the lasers divergence at infinity focus, because it isn't. I can't see how it is possible to get less than 1 mRad out of a NUBM44 laser diode unless the beam is expanded more than 40 mm.

So the beam must be infinity focused to do mRad cal ?

You may have 18X on one axis but the other axis is diverging, you could do a mRad on the other axis.

Divergence > CLICK ME

RedCowboy said:

You may have 18X on one axis but the other axis is diverging, you could do a mRad on the other axis.

Divergence > CLICK ME

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The G-2 lens has that axis and I did, This is that axis......



And this is the 18X axis......

Jeeeezzz...I just could NOT resist :san::san:

See attached pic !!! hahahahaha

BUT....one cannot physically achieve 0 mRad divergence ! That much I know.

One could focus so the "Convergence Point" would be 50 feet out !!

Hey...how about we incorporate some IR range finder...feed that telemetry into a auto focus mechanism......and....at whatever distance the Target / Far Field is...THAT is where the Auto Focus sets the Convergence Point ??? Naaauu...dARPA has already done it !!!

CDBEAM

CDBEAM777 said:

Jeeeezzz...I just could NOT resist :san::san:

See attached pic !!! hahahahaha

BUT....one cannot physically achieve 0 mRad divergence ! That much I know.

One could focus so the "Convergence Point" would be 50 feet out !!

Hey...how about we incorporate some IR range finder...feed that telemetry into a auto focus mechanism......and....at whatever distance the Target / Far Field is...THAT is where the Auto Focus sets the Convergence Point ??? Naaauu...dARPA has already done it !!!

CDBEAM

Click to expand...

Who claimed 0 mRad divergence ??? Was it you ???

You are hilarious, CDBEAM. Zippy! I love it. Keep on truckin'!

I can't imagine he was saying you were making the statement your results show you have zero divergence, but if the beam is focused to a point you can be much closer to zero divergence, as you have now. What you should do is measure the divergence of both axis, but I still believe the beam is focused to a point instead of set to infinity focus.

Alaskan said:

I can't imagine he was saying you were making the statement your results show you have zero divergence, but if the beam is focused to a point you can be much closer to zero divergence, as you have now. What you should do is measure the divergence of both axis, but I still believe the beam is focused to a point instead of set to infinity focus.

Click to expand...

None of my results shows zero divergence ???

This is the fast axis...



And this is the slow axis....



The slow axis is always set to infinity focus and never changes.........

How much total expansion do you have with your optical setup? Edit: I'm talking about actual expansion of the beam itself after collimation, not lens powers multiplied by lens powers, most of those claimed 6X etc. cylinder pairs are wrong, i.e. some expander sets claiming to be 3X are closer to 2X etc.

I'm thinking this is where we are going down the wrong track, it is the beam diameter itself at the output of the pointer, within a few inches of the output I need to know to give you the expected divergence for your optics with that diode. This will tell me if your mRad numbers are correct for a beam at infinity focus which is not converging to a point.

Can't use lens powers, or claimed lens powers, to determine the expansion, it's how much wider your optics makes the beam which will reduce the divergence. For example, if you had a diode which when collimated with a 6mm diameter lens produces a beam which is, for example, 5 mm wide when collimated, and has a mRad of 10, the beam would need to be ten times wider to reduce the divergence by 10 down to 1 mRad. It's the beam diameter increase itself, as a ratio, which will determine the reduction of divergence, up to an amount.

Yikes....You's guys maka my head spin !! I just stated the Optical " Captain Obvious " about Zero Divergence !!! HMMMmmmm !! Hey Paul....Dunno...MAYBE Zippy thinks one can achieve Zero Divergence....so...again...optical speaking..." Lighten Up"......
Beam Out

This is one reason I went with the straight forward 6X pair, from where I grabbed the beam out of the G2 ( Very Close to the G2 ) with the cyl concave and caught its funnel shaped output with the cyl convex about 35mm away it expanded about a 1mm wide beam into a 6mm wide beam on the aggressive axis. So the beam is basically a ribbon that gets thicker and wider over distance. ( note: This is without any BE )

So how can 18X not produce a very wide beam? Why is it not 18mm wide at the aperture?

RedCowboy said:

This is one reason I went with the straight forward 6X pair, from where I grabbed the beam out of the G2 ( Very Close to the G2 ) with the cyl concave and caught its funnel shaped output with the cyl convex about 35mm away it expanded about a 1mm wide beam into a 6mm wide beam on the aggressive axis. So the beam is basically a ribbon that gets thicker and wider over distance. ( note: This is without any BE )

So how can 18X not produce a very wide beam? Why is it not 18mm wide at the aperture?

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Remember the beam coming out of the G-2 is very small so 18X that very small beam ends up being 8mm after the last lens......

This is the lens arrangement I'm using, The beam after both of those is 3 feet wide on the wall across the room, Now how it's doing what it's doing ? I don't know, I only know it is and I'm very happy with the results !

So the input beam on one axis was 0.44mm?
Divergence must always be carried out at infinity.
I collimate my lasers at multiple points to make sure I haven't focused the laser to one point only as it is easy to do in your defence.
I start with a close field, then far field and then check the mid field. I also run along the beam checking the spot throughout the distance allowing me to check for negative divergence. The far field hasn't particularly got to be that far away, as sometimes I'm limited to 3-4m to check the divergence.
If you values are correct, then they are very low and I applaud you. But I also believe you may of just focused the beam at 50ft. 50ft is a long distance to check. But every 5ft you should get an object to stop the beam and just check the dot size. If you notice the dot size going down then you know that you haven't collimated the beam properly.

So the input beam on one axis was 0.44mm?

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??? I have no idea......


The slow axis is focused to infinity but the fast axis probably was not but it was close, I'll redo the fast axis divergence test......

Ok. Let us know what you find.