wrote:
Protagonist wrote:

While back I heard optics and first surface mirrors are single point
diamond turned on special CNC lathes, than hand figured.
Last few months I've been working for an optics company, told my boss
about it, but he said it's imposable.
Single point diamond can't cut glass, not accurately.
I even showed him these web-sites here.


Single point diamond optical lathes are accurate enough to put a good
surface on IR optics (about 2.5 waves of yellow light) up to several
meters in size. These surfaces can then be smoothed with normal
(computer controlled) polishing techniques, and then figured in ion
mills to very high surface accuracies (20 nm).

Eye glasses can be directly turned on these lathes to accepatable
accuracies (because eye glasses do not need to be good optical
surfaces).


Typical as machined tolerances for diamond turned optics are under 100
nm form, and 1-2 nm RMS finish. BTW, Ophthalmics are fussier than you
may think as structured surface errors are very visible even though the
errors themselves are below the diffraction limit. It is an issue more
with cosmetics rather than function.

--
jeff