- In the case of a refractive or reflective optical element, the optical axis is the straight line that
is coincident with the axis of symmetry of the surfaces. Note: The optical
axis of a system is often coincident with its mechanical axis, but it
need not be, e.g., in the case of an off-axis parabolic reflector used
to transmit signals to, or receive signals from, a geosynchronous satellite.
- In the case of a lens element, the optical axis is the straight line which passes through the centers
of curvature of the lens surfaces.
- In the case of an optical system, the optical axis is the line formed by the coinciding principal
axes of the series of optical elements.
AND OPTICAL PHENOMENA