Vacuum Ultraviolet (VUV-UV) Bi-Convex & Bi-Concave Spherical Lenses are available in select VUV Grade Calcium Fluoride (CaF2) for a wide range of VUV to UV optical applications including VUV to UV instrumentation or VUV to UV lasers.  VUV to UV CaF2 Bi-Convex & Bi-Concave Spherical Lenses have two spherical surfaces with the same Radius of Curvature either curved outward (Bi-Convex) or curved inward (Bi-Concave).  

VUV CaF2 Bi-Convex Spherical Lenses have positive Effective Focal Lengths (EFL) and are popular for many finite imaging applications. Both spherical convex surfaces are designed to minimize aberrations in lens applications where the object and image distances are equal or nearly equal. As a example, VUV CaF2 Bi-Convex Spherical Lenses are the best choice for minimizing aberrations if the conjugate ratio (object distance : image distance) is between 5:1 and 1:5. Outside this range, VUV CaF2 or MgF2 Plano-Convex Spherical Lenses are typically used.

VUV CaF2 Bi-Concave Spherical Lenses have negative Effective Focal Lengths (EFL) and cause incident VUV-UV light to diverge, which is useful in a wide range of VUV to UV applications.  VUV CaF2 Bi-Concave Spherical Lenses are typically used to increase the divergance of a converging beam.  In VUV to UV optical system applications, VUV CaF2 Bi-Concave Spherical Lenses are often used in pairs to increase the effective focal length of a converging lens. It is also common to use both Bi-Convex and Bi-Concave lenses in the same application so that the aberrations introduced by the positive and negative focal length lenses approximately cancel.

As VUV CaF2 Bi-Concave Spherical Lenses cause incident VUV-UV light to diverge, it is usually preferrable to choose a VUV CaF2 Bi-Concave Lens if the absolute conjugate ratio (object distance divided by image distance) is close to 1.  When deciding between a VUV CaF2 Bi-Concave and VUV CaF2 Plano-Concave Lens, typically a VUV CaF2 Plano-Concave Lens is used when the desired absolute magnification is either less than 0.2 or greater than 5. 

Also see our VUV Grade CaF2 Plano-Concave Spherical Lenses , VUV Grade MgF2 & CaF2 Plano-Convex Spherical Lenses & VUV to UV CaF2 Positive & Negative Meniscus Lenses
 

VUV Grade Calcium Fluoride (CaF2): CaF2 exhibits good transmission properties from ~ 145nm Vacuum UV (VUV) to ~ 8.0um in the Infrared.  CaF2 is a relatively soft crystalline material and care should be taken as CaF2 is sensitive to mechanical and thermal shock.  CaF2 is a cubic single crystal optical material.
 

More information can be found on our Material Properties Page.   For more information about Spherical Lenses, refer to our Optics Tutorial page. 
                               

                                                                                  CaF2 Refractive Index