The meniscus lens includes a positive meniscus lens and a negative meniscus lens. The positive meniscus lens is used to reduce the focal length of another lens while maintaining the angular resolution of the optical components. Its materials include K9, UV fused quartz, CaF2, and ZnSe. These lenses are usually paired with another positive lens to obtain better focusing effect.
The negative meniscus lens is designed to minimize the spherical aberration. The negative meniscus lens consists of a convex surface and a concave surface, and the concave surface has a larger radius of curvature. The combination of negative meniscus lens and another lens will reduce the numerical aperture of the system. Negative meniscus lens is a common component in beam expansion applications.