noun
1. : principal visual ray
2. : the one ray of the rays entering an optical instrument from any given point of the object that passes through the exact center of the aperture stop
noun
1. : principal visual ray
2. : the one ray of the rays entering an optical instrument from any given point of the object that passes through the exact center of the aperture stop
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012