asphericon News

One of the products to be unveiled by asphericon at Optatec 2010 is the new ION Finish™ technology. Could you briefly explain to us the ION-Beam process that is used, please?

Mr. Bräutigam (B): Behind the name ION-Finish™ lies a sputtering process which alters solid particles by targeting them with accelerated Argon ions. From the static removal profile of the ion beam and the total area of the surface form deviation on the surface, a dwell time matrix is calculated for the ion beam to remove the form deviation and to give it the desired form accuracy.

Mr. Kiontke (K): This technology has been used successfully in the semi-conductor and solar power industries on plane surfaces for some years now. At asphericon we are using this process for the first time in the field of end-finishing of aspherical surfaces.

What are the distinctive features of finishing aspherical surfaces, in comparison with spherical ones?

K: In comparison to spherical surfaces, aspherical surfaces are finished using smaller mechanical tools. For this reason, in addition to the long wavelength portions, they also have very short wavelength variations from the required shape. To reduce these short wavelength portions, thinner etch profiles must also be used in the final correction of the shape. In order to keep the costs in terms of time and therefore money for finishing as low as possible, the short wavelength and long wavelength variations are separated from each other and are finished successively.

Which materials can be finished using this technique?

B: The process can be used with concave or convex surfaces of any shape and causes no mechanical damage of any kind to the surfaces. Depending on the physical sputter removal, the process can be used on any type of glass, and also on mechanically hard substrates (Si, SiC) and crystalline optical components (MgF2, CaF2, Si, ZnS, WC).

Let's take a look at the levels of accuracy that can be reached: what can be achieved with ION-Finish™?

K: Using asphericon control technology, even at the pre-polishing stage the PV-ratio can be kept small and in the long wavelength range. With ION-Finish™ correction polishing, the PV-ratio can then be corrected in an extremely time-efficient way and the highest levels of accuracy, up to small values of lambda/20 (PV), can be achieved.

What are the key advantages in comparison to conventional technologies?

K: With asphericon ION-Finish™, we are combining innovations in systems technology with a sophisticated process flow. The use of a double gate and a special aperture system for in-situ selection of the finishing diameter makes it possible for the first time not only to achieve first-class finishing of various materials and contoured surfaces, but also to keep the finishing costs in the same range as traditional technologies, such as magnetorheological polishing.

Mr. Kiontke, Mr. Bräutigam – thank you very much!