The University of Rochester has developed a machine that can produce
positive aspheric lenses to 1/20th wave in minutes. The machine,
called
something like Magnetohydrodynamic, uses a moving belt with a special
liquid layer. The liquid has a marked surface tension. The lens
blank
is held on a spindle and pressed to the liquid on the belt. The
liquid
depth is about 2mm and the submersion of the lens in the liquid (depth
controlled submersion) produces specific pressures and material
removal.
This method avoids many problems associated with other forms of lens
"grinding." The process has been commercialized and could have a
marked
effect on the cost of implementing aspherics in eyepiece designs.
Now I'm waiting for the distortionless, Plossl-sized eyepieces with
100 deg. fields for $200!!