noun Date: 1664 a line in a doubly refracting medium that is parallel to the direction in which all components of plane-polarized light travel with the same speed
OPTIC AXIS
Meaning of OPTIC AXIS in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012