The central line of symmetry in a luminaire or lens system. Light rays traveling exactly along the optical axis pass through the system without being refracted or deviated. It serves as the reference line for measuring beam angles, aberrations, and alignment of reflectors and light sources.
Heard on the job
If the LED chip isn't perfectly centered on the optical axis, the beam will throw a nasty crescent shadow on the wall.
Also heard as
- principal axis