- Thread starter IsaacT
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If that is the case then .098mRad stands as the measurement I received...

I measure divergence up to 30 feet. On my reds, the best I can get is about ~0.5mRad.

The goal is not to measure it

If the beam is converging at some point, you will need to check at a much greater distance.

What you could be measuring is a beam with negative divergence, meaning your measurement could be skewed and artificially decreased because it is measured near the beam waist.

The goal is to minimize the diameter of the beam in the far field, away from the focus of the laser, and then take that measurement.

Typical divergence will be around 0.5mRad, which is good.

hmm....so maybe focus it at 60 feet or something and then measure at 1 foot and 35 feet? Does that sound resonable?

What you are trying to achieve is lowest divergence. That does

It is pretty self explanatory... you want the beam to not diverge (or converge). You want the beam to remain as parallel as possible so that the beam diameter is minimal at all distances.

If you have 60 feet available, use it. The more distance the better. I don't know why you would set it up at 60' though, and then only measure it at 35'?

I have no problem using ~30-40' for measurements, don't know why you are having problems.

I will reiterate: Do not measure the beam at or near the waist!

Okay....I think I understand now....I could set it up for ~35 feet, but try to get both measurements the same....yes? so if I have 5mm at a set point close to the laser, I go for having 5mm on the wall?

But since a zero divergence beam is impossible, you should be getting a beam a little wider than 5mm.

And you want to make sure that the beam does not converge.

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