A telescope of two lenses that increases beam diameter by the ratio of their focal lengths and reduces divergence by the same factor. Galilean designs use a negative and a positive lens and have no internal focus, making them preferred for high-power pulsed beams. Keplerian designs use two positive lenses with an internal focus where a pinhole can clean up the beam. Expanding before a focusing lens gives a smaller focused spot.
Put the 3x beam expander in before the scan head, we need the smaller spot and the mirrors are big enough.
Also heard as
- telescope
Related terms
Divergence
How fast a laser beam spreads with distance far from its waist, given as an angle in milliradians.
Beam waist
The narrowest point of a focused or propagating laser beam, where its wavefront is flat.
Rayleigh range
The distance from a beam's waist to where its cross-sectional area has doubled, a measure of depth of focus.
Clipping
A beam partly cut off by an aperture, mount or edge, causing power loss, diffraction rings and hot spots.