Negative Meniscus Lenses

A negative meniscus lens is composed of two curved surfaces with similar radii of curvature (the radius of curvature of the concave surface is smaller than that of the convex surface) and has a negative focal length. It is usually used in applications such as beam expansion, increasing focal length, and reducing numerical aperture. To reduce spherical aberration, when used in beam expansion or diverging collimated light applications, the light beam should be incident on the convex surface of the lens; when used for collimating converging light, the light beam is incident on the concave surface.