optic axis meaning and definition

OPTIC AXIS noun

Definition of optic axis (noun)

1. in a doubly refracting crystal, the line in the direction of which no double refraction occurs
   • "a crystal may have either one or two optic axes"
2. a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted
   • "in a normal eye the optic axis is the direction in which objects are seen most distinctly"
   • synonyms: principal axis