optična os
1. optična os
in a doubly refracting crystal, the line in the direction of which no double refraction occurs [V dvojno lomnem kristalu, črta v smeri katere ni dvojnega loma.]
2. optična os
a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted [Črta, ki poteka skozi središče krivine leče, tako da svetloba ni niti odbita niti lomljena.]