Bi-Concave lens

Bi-concave lenses are manufactured with both surfaces concave. These lenses have negative focal lengths and are best used to diverge a converging beam. Bi-concave lenses can diverge a collimated beam to a virtual focus and are commonly used in Galilean-type beam expanders. They are often used to expand light or increase focal lengths in existing systems. Biconcave lens are used in laser beam expanders, optical character readers, viewers, and projection systems.