Optical Axis
The imaginary central straight line passing through the centers of curvature of all optical elements in a rotationally symmetric system.
Governing formula
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SI unit
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In depth
Light rays traveling along the optical axis pass through without angular deflection. Serves as the reference baseline for paraxial ray tracing and sign conventions.
Examples in the real world
The central axis passing through the centers of an objective lens, eyepiece, and human eye pupil in a telescope.