CaF2 Fused Silica is commonly used for applications requiring high transmission in the infrared and ultraviolet spectral ranges. Its extremely high laser damage threshold makes it useful for use with excimer lasers. CaF2 exhibits a low refractive index, varying from 1.35 to 1.51 within its usage range of 180 nm to 8.0 μm. Calcium fluoride is also fairly chemically inert and offers superior hardness compared to its barium fluoride, magnesium fluoride, and lithium fluoride cousins.
Double Concave Optical LensesSpecifications | |
Wavelength Range (Uncoated) | 0.18 – 8.0 μm |
AR Coating Range (-E Versions) | 3 – 5 μm |
Reflectance over Coating Range (Avg.) | <2.0% |
Surface Quality | 40-20 Scratch-Dig |
Bi-convex lenses are popular for many finite imaging applications. Both surfaces are spherical and have the same radius of curvature, minimizing aberrations in situations where the object and image distances are equal or nearly equal. As a guideline, bi-convex 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, plano-convex lenses are usually preferred.