A lens geometry where both the front and back optical surfaces curve inward toward the center, making the lens thinner in the middle than at the edges. This shape causes collimated light rays to diverge and is typically used to expand beams or increase the focal length of an existing optical system.
Heard on the job
Put a biconcave lens before the objective to expand the beam enough to fill the aperture.
Also heard as
- double concave
Related terms
Beam expander
A pair of lenses arranged as a telescope that enlarges a collimated beam's diameter and cuts its divergence.
Planoconcave
A lens shape featuring one flat surface and one inwardly curved surface.
Divergence
How fast a laser beam spreads with distance far from its waist, given as an angle in milliradians.