Rainbow Research Optics Offers complete optical data design. They provide the following charts and information to help you determine your specific needs. Lens Terminology, Focal Length Formulas for Singlet Lenses & Mirrors, Effective Focal Length of Two Thin Lenses, F-Number (F/#), Numerical Aperture (N/A), Sagitta (Sag), Using Wedged Windows, Selecting a Prism, and Waveplates are all available through Rainbow Research Optics. For more information on these services visit www.rainbowoptics.com today!