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in the most basic of terms, divergence is the amount the beam expands over distance. mrad is the calculation of millimeters of divergence per meter.

if a 1mm beam expands to 10mm over a distance of 10M, the mrad value is .9. 10(far field size in mm) - 1(near field size in mm) / 10 (distance in meters).

if a 1mm beam expands to 10mm over a distance of 1M, the mrad value is 9.

this assumes a reasonably gaussian (round) beam.

Originally Posted by

**skot**
Was wondering if someone could explain what is actually being measured in divergence.

In simple terms, I'm understand divergence is an increase in the beam width, so a 3mm beam at apperture compared to a 4mm beam at a point of 10m has X mRad divergence, thus the lower the divergence the more 'true' the beam stays for longer. (think thats correct at least)

I've been reading wikipedia for Radian and assume the measurement is effectively the increase in the radius of the beam width, but I'm not certain thats right, mainly due to measurements indicating angles within a circle.

Not really trying to get to complicated, but just looking for a clearer understanding of how it is measured and what measurements are taken.

Thx

suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.