Sapphire and Ruby Ball Lenses are both made from Al203. Ruby or Ruby-Doped sapphire owes its red color to traces of chromium oxide (chromium content for ruby balls is typically >0.5%). While their physical and chemical properties are similar, Sapphire has superior optical transmission. Ruby Ball Lenses are easier to see and handle for physical applications. Sapphire and Ruby Ball Lenses are ideal for improving signal coupling between fibers, emitters, and detectors. They are also used in endoscopy, bar code scanning, ball pre-forms for aspheric lenses, and sensor applications. Sapphire and Ruby Half-Ball Lenses are also available.
For general information about ball lens, as well as how to calculate the NA and Focal Length, view Understanding Ball Lenses.