Can you give some examples of the definitions
you're referring to?
I'm just going by what I hear around the lab, i.e. the usage
of people who do optics for a living, i.e. people who build
their own home-brew scanning confocal microscopes from scratch.
There's not AFAIK parallel rays anywhere within such an
instrument, yet everybody refers to the "focal point" the same
way they would refer to the "focal plane" of a non-confocal
instrument.
There's logic in this. As I said before, the "one-f" focal
point emerges as a corollary in the less-than-general case
where the object is at infinity. Special case ... often an
interesting special case ... not the definition.
_______________________________________________
Phys-L mailing list
Phys-L@electron.physics.buffalo.edu https://www.physics.buffalo.edu/mailman/listinfo/phys-l