ION Milling...

Ion-Beam Figuring. Also known as Ion-Milling or Ion-Cannon technology.

"Post figuring is a common procedure in modern glass optics. The Keck telescope mirror segments, for example, were polished to the l/20 (optical) level and then post figured to the l/100 level by ion milling". See:4. Allen, L.N., Keim, R.E., Lewis, T.S. & Ullom, J. "Surface Error Correction Of A Keck 10m Telescope Primary Mirror Segment By Ion Milling", Proc. SPIE 1531, 195-204 (1991) .

Ion Beam Figuring (IBF) was originally developed by the Eastman Kodak Company in 1988 and became operational in 1990. IBF is an excellent complement to conventional figuring. The optics are first polished (ground) conventionally and then final figure is milled by IBF. Ion Beam Figuring works on a molecular (atomic) level.

Without question, Ion Milling is the most important breakthrough ever in optical manufacturing!

RCOS offers the HIGHEST QUALITY and most economical ION MILLED OPTICS possible in the 0.37m to 1.00m sizes. We have supplied hundreds of telescopes with ION Milled Optics.

Ion Milling is available for optics of .37m"- 1.0m" sizes. Please call or e-mail for information on other sizes.

See our discussion on Flotation Mirror Cells for these optics.
View a typical Interferogram of an ION Milled 24RC.


A Ritchey-Chr├ętien 16 inch primary mirror already figured and polished to 1/6 wave P-V is mapped by a special camera. The optics are then inserted into a high-vacuum chamber facing down. The IBF then directs a beam of argon ions upward to the glass. The glass is removed on a molecular level. The beam itself is translated across the optical surface through a computer controlled mask, removing figuring errors and surface roughness leftover from conventional polishing.

When the Ion Beam-Figuring is finished, the chamber is purged and the process is complete. This completed 16 inch Ritchey-Chr├ętien primary mirror required only 3 iterations with the Ion-Beam.