Opt Lasers 6X Cylindrical Testing

[Accutronitis]

It's 50 feet easy, measured it myself.....

I just had to say that's not looking like 6 1/4 sheets of plywood

I don't understand what your saying here ?

 

[Alaskan]

Can you take that laser pointer and adjust it so when beaming out into the night sky the beam is adjusted so it neither converges or diverges, as strait a line as you can adjust it to be? That would be infinity focus. As it is, I believe the beam is focused to converge to a point 50 feet away, beyond that the beam spreading out again.

Since the NUBM44 has such a large divergence, unless expanded to close to 3 inches diameter, you can try to adjust it all night long and will never get it to stop diverging into a fan at the end of the beam, but once set to infinity focus, the beam is as tight as you can make it without being focused down to a point in space before crossing over to spread out again.

 

[RedCowboy]

Thanks for the words on safety Alaskan :beer:

Safety is our life blood and although I like to share my testing I am always very safety conscious and that's why I built my cinder block fire pit, so I can safely keep the smoke outside, as for the high up green leaves I only ever do that after a big rain, we have had 3 days of it and the ground is saturated.

People reading should know that a hollow tree or dried out brush under green brush can smolder for hours, so know your backstop and don't let an accident happen, as lasers get stronger we must spread the word to be extra cautious.

----EDIT----

@ Accutronitis: Yea I always judge short on distance, my back corner of my yard I guessed at 75 feet from my window, it's actually 105 feet and I have lit bags there with my moped muffler build, one thing you can do is soak down an area if you are going to be testing there, it's a lot better than running out the door yelling OH CRUD, not that I have done that, I haven't....well not with lasers, but I fear ever letting something get out of hand so I play it extra safe, it's worth the effort.

 

[Alaskan]

I didn't mean to lecture or advise, just sharing my thoughts after you had remarked everything was wet, I don't ever want to come off as trying to tell you something, I know you are well aware and take great care.

 

[RedCowboy]

Not at all my friend, and when we repeat safety protocols in a veterans thread it's not for the veteran but the thousands of visitors who it could make a difference with, I really don't want to inspire anyone to do anything dangerous, I would rather hear it repeated again and again than let a reader mimic a test I posted assuming everyone knows the dangers, we must always point out the pitfalls even though we know them, some readers may not, and I don't want anyone to have to learn the hard way.
I don't mind hearing it at all, it's good to point these things out for all readers.

 

[Alaskan]

Now to get Acc. to understand he is focused to a point and that doing so has nothing to do with mRad when at infinity

Brother Acc., not meaning to talk down, but I don't think you are catching on to the idea yet, mRad for laser pointers only applies to a beam which has been collimated to "infinity" focus, not what you are doing. I suppose you could say your laser is not diverging, or specify an amount of beam divergence when hitting a target 50 feet away and in a different way be correct, but the mRad figure we use with laser pointers is in regard to the optical divergence when set to infinity focus which is as close as you can get to neither converging, or diverging. Only thing left then is the divergence caused by the relationship of the size of the "point" source to the amount the beam has been expanded and then collimated.

 

[RedCowboy]

It's in the 2nd sentence of the definition.

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

 

[Alaskan]

Yea, that's better, I have a hard time explaining it and am half fearful the master will come and show me how wrong I am, but I suppose that is really a favor.

 

[RedCowboy]

I think it depends on how wrong you are and where you rate on the Douche scale, maybe it depends on if you take your lumps or backchat the Master, I have heard people get a Douche rank upgrade on the fly.....it's a battle between ego and He know

 

[Accutronitis]

Can you take that laser pointer and adjust it so when beaming out into the night sky the beam is adjusted so it neither converges or diverges, as strait a line as you can adjust it to be? That would be infinity focus. As it is, I believe the beam is focused to converge to a point 50 feet away, beyond that the beam spreading out again.

Since the NUBM44 has such a large divergence, unless expanded to close to 3 inches diameter, you can try to adjust it all night long and will never get it to stop diverging into a fan at the end of the beam, but once set to infinity focus, the beam is as tight as you can make it without being focused down to a point in space before crossing over to spread out again.

That's not correct, I can adjust the beam so it neither converges or diverges and is wide to converging at 50 feet and past that to converging at 1 foot and then the beam spreading out again, And everything in between, That's because I'm using 18X Cylindrical Lens on the large divergence Fast Axis Which is a 6X plus a 3X Cylindrical Lens together........

With it adjustable now I can have a small spot at 50 feet OR adjust it for a great looking beam shot out into the night sky and that beam neither converges or diverges......

As far as I can tell I'm the first person to do this and it gives the best of all worlds......

Now to get Acc. to understand he is focused to a point and that doing so has nothing to do with mRad when at infinity

Brother Acc., not meaning to talk down, but I don't think you are catching on to the idea yet, mRad for laser pointers only applies to a beam which has been collimated to "infinity" focus, not what you are doing. I suppose you could say your laser is not diverging, or specify an amount of beam divergence when hitting a target 50 feet away and in a different way be correct, but the mRad figure we use with laser pointers is in regard to the optical divergence when set to infinity focus which is as close as you can get to neither converging, or diverging. Only thing left then is the divergence caused by the relationship of the size of the "point" source to the amount the beam has been expanded and then collimated.

Yes I know that, I only added the mRad cal because it was my latest one, that's all......

 

[diachi]

That's not correct, I can adjust the beam so it neither converges or diverges and is wide to converging at 50 feet and past that to converging at 1 foot and then the beam spreading out again....

You might need to clarify...

You can't have a laser beam that neither converges nor diverges, as that would require a divergence of 0°, which is physically not possible.

 

[Accutronitis]

You might need to clarify...

You can't have a laser beam that neither converges nor diverges, as that would require a divergence of 0°, which is physically not possible.

I was just using what Alaskan had said, By "neither converges nor diverges" what I really mean is the beam is slowly diverges BUT you can't really tell because it just looks like a nice straight parallel beam going up into the night sky.....

I still don't understand how Acc. is getting such a low divergence with such a small aperture when using the NUBM44, expansion is expansion whether one or both axis, the same thing. Surely the pointer must be focused to that small of a spot instead of at infinity, if so, you cannot use the spot size to calculate divergence. To get under 1 mRad would require a lens which is close to 2.75 inches diameter with that diode. IDK, maybe larger, what is the divergence using a 6 mm diameter collimating lens, 11 mRad?

18X Cylindrical Three Lens Fast Axis Correction is how, The beam at the last lens is 4mm x 8mm and at 50 feet the beam dot is 8mm x 16mm........

 

[Alaskan]

Yea, I was trying to explain neither converges or diverges, except for the unavoidable divergence of the beam due to the size of the point source (not really a point source) and the amount of expansion. The way I calculate the total beam expansion is based on the mRad you would get from a 6 mm "G2" lens. For example, if you had 10 mRad with a beam 4 mm wide, no matter how you cut it, to get 1 mRad, the beam would need to be 40 mm wide.

 

[Accutronitis]

Yea, I was trying to explain neither converges or diverges, except for the unavoidable divergence of the beam due to the size of the point source (not really a point source) and the amount of expansion. The way I calculate the total beam expansion is based on the mRad you would get from a 6 mm "G2" lens. For example, if you had 10 mRad with a beam 4 mm wide, no matter how you cut it, to get 1 mRad, the beam would need to be 40 mm wide.

I don't know about all of that, All I did was put the numbers from my measurements into the mRad calculator and pressed the calculate button......

 

[paul1598419]

Even though the beam looks like it is straight and not diverging as it goes up into the night sky, you really can't see the divergence because as the distance of the beam increases from your eyes, it is also becoming larger in diameter, but being farther away looks smaller to you. So, if you saw the beam's diameter at 5000 feet, it might be 5 meters across, but would still look the same to you as your perspective hasn't changed. You would need to be at the 5000 foot mark of the beam to see its actual diameter.

 

[Accutronitis]

Even though the beam looks like it is straight and not diverging as it goes up into the night sky, you really can't see the divergence because as the distance of the beam increases from your eyes, it is also becoming larger in diameter, but being farther away looks smaller to you. So, if you saw the beam's diameter at 5000 feet, it might be 5 meters across, but would still look the same to you as your perspective hasn't changed. You would need to be at the 5000 foot mark of the beam to see its actual diameter.

Yes, I know that, That's why I said "just looks like a nice straight parallel beam going up into the night sky", Like you said it just "looks" as if.....