Sapphire and ruby balls have use in drone vision systems
Ultra-miniature sapphire and ruby balls, unaffected by fast-moving dirt and impervious to most chemicals, are used as lens systems in micro-air vehicles. Available in 42 metric and English sizes from 0.1 mm to 0.5 in. diameters with antireflective coatings, the balls have Mohs 9 hardness and 80-20 scratch-dig surface finishes.
Meller Optics
Providence, RI