bi-concave spherical lens

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, and are the best choice when the object and image are at absolute conjugate ratios closer to 1:1 with a converging input beam. N-BK7 lenses are a great choice for most general purpose visible and NIR applications, featuring high homogeneity and low bubble and inclusion content. UV Fused Silica lenses are ideal for UV or higher energy applications, combining a very low thermal expansion coefficient and excellent transmittance down to 195 nm.