Unless the lenses have bits that 'overhang' it would seem possible to simply CNC mill the whole thing?
A lens needs accuracy to ~the wavelength, so 400nm. That seems doable with not so specialist CNC tech.
A lens needs accuracy to ~the wavelength, so 400nm. That seems doable with not so specialist CNC tech.
Commercial aspheres are polished with special CNC grinders, but achieve nowhere near the quality of spherical lenses. Only recently magnetorheological finishing became available which allows getting a bit closer in quality.
In most applications, it makes more sense to stack a few spherical lenses instead of manufacturing a super expensive custom asphere which cannot even compensate for chromatic aberrations.