Wfoley2 wrote:

Actually, for a while there were some companies selling molded blanks, but this
was only to save time grinding and polishing. So far as I know, there just
aren't any molding processes yet which can give better than 1/4 wave accuracy
and smoothness. There were also some blanks with the shape roughly ground in
to save the ATM time. I do not know if these are still available or not. I
would think that, in this day and time, our technology would allow extremely
precise molding, but do not know of anyone actually doing it...

It is done for very small glass optics. The process is unworkable for
glass optics of any size. The examples I know of that are molded glass
are aspheric objective lenses for DVD players. These are diffraction
limited.

Chuck
--
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons