Beam Divergence Calculator

Formula

The formula to calculate the beam divergence is:

\[ \theta = 2 \times \arctan \left( \frac{D_f - D_i}{2L} \right) \]

Where:

\(\theta\) is the angle of divergence
\(D_f\) is the beam diameter at point f
\(D_i\) is the beam diameter at point i
\(L\) is the distance between point f and point i

What is Laser Divergence?

Laser divergence is the measure of the angle of a laser beam’s spread. A laser beam that has low divergence could be said to be “collimated”, which means it will maintain a narrow beam as opposed to spreading out. If you’re using an optical instrument, such as an optical collimator, that requires a collimated beam of light, you have to make sure that the laser beam has low divergence.

Example Calculation

Example:

Beam Diameter at Point f: 5 mm
Beam Diameter at Point i: 3 mm
Distance Between Points: 1000 mm

Calculation:

\[ \theta = 2 \times \arctan \left( \frac{5 - 3}{2 \times 1000} \right) = 0.11 \text{ degrees} \]