- Always wear laser eye protection during this test.
- Project the beam onto a matte black surface at 1m from the aperture of the laser A metal surface painted with flat black paint works well.
- Measure the diameter of the beam in mm excluding the area where the brightness is less than 20%.
- Measure the beam diameter again at 11m from the aperture of the laser, excluding the area where laser power is less than 20% of the beam center.
- Subtract the value measured at 1m from the value measured at 11m. Divide the result by 10. This is approximately the divergence in mRad (milliradians).
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