Bi-Concave (Double-Concave) lenses have equal radius of curvature on both sides of the lens and function similarly to plano-concave lenses by causing collimated incident light to diverge. Bi-Concave lenses are generally used to expand light or increase focal length in existing systems, such as beam expanders and projection systems.

Bi-Concave (Double-Concave) lenses have equal radius of curvature on both sides of the lens and function similarly to plano-concave lenses by causing collimated incident light to diverge. Bi-Concave lenses are generally used to expand light or increase focal length in existing systems, such as beam expanders and projection systems.