Reducing Cost: Show me the Money

There is no denying that a single aspheric lens is typically more expensive than a single spherical lens, but recent advances in asphere manufacturing technology have allowed high-performing aspheres to be produced at a significantly reduced cost. Previously, spherical full-aperture grinding and polishing could achieve irregularities of λ/4, while aspheric grinding and polishing could only achieve irregularities of 1λ. Magnetorheological finishing (MRF), a deterministic fine finishing process that selectively removes material with high precision and control, was required to produce higher quality aspheres and could achieve irregularities down to λ/20. However, MRF adds a significant amount of cost. Advanced subaperture aspheric grinding and polishing is now approaching the same irregularity capabilities as spherical full-aperture grinding and polishing, producing high quality aspheres at a reduced cost. This drop in asphere cost makes replacing multiple spherical lens elements with fewer aspheric lenses an even more economical solution, leading to an increase in optical designers incorporating aspheres into their designs. While MRF is not required for all asphere manufacturing, MRF is still required for extremely high quality aspheres with irregularities typically only limited by the sensitivity of available metrology.