Overview of High-End-Finishing processes

Depending on the production requirements, materials or required accuracy, each of the High-End-Finishing processes represented can convince with outstanding results....

High-End-Finishing Correction Processes Part 4

A comparison of the three High-End-Finishing processes discussed above, shows each polishing process can be attributed special advantages. Depending on the production requirements, materials or required accuracy, each of the High-End-Finishing processes represented can convince with outstanding results.

The following table briefly summarizes the three correction procedures presented.

ProceedingsIon beam etching using spot ion bombardment locally corrects the shape errorAbrasive magnetorheological suspension locally corrects the shape errorOptimized CNC polishing process corrects roughness in the short-wave spatial frequency range to a minimum
AdvantagesMachining is free of chemical influences, therefore fragile materials can also be machinedHigh repeatability and determinismVery low surface roughness values, minimal residual scattering
Correction    Long-wave errorsShort and long wavelength errors    Short-wave errors
(medium to high spatial frequencies)
Application    Smaller quantitiesMedium to high quantitiesSmall to large quantities
(scale of 3)


The ION-Finishing is particularly advantageous for polishing materials that don’t allow for chemical influences (e.g. compound with H2O). MRF technology is characterized by a broad correction spectrum in the short and long wavelength range and is therefore considered to be a kind of "allrounder of polishing processes". The Ångström-Polish convinces with particularly low residual scatter and minimal roughness values.

The following figure (Fig. 1) illustrates the effectiveness of the procedures more clearly. Lateral frequencies like short- to long-wave defects of the optical surfaces are represented for each High-End-Finishing process. Compared is the correction efficiency, i.e. the effectiveness of the polish correction on the optical surface. The grey curved lines clearly represent the transition from short to long wavelengths. It shows that the curve of the MRF method (light blue line) can be used for polishing both, shorter and longer wavelength ranges, but not for the medium wavelengths. The curve of the Ångström-Polish (dark blue line) is in the short to medium wavelength range. It is noticeable that the curve shows a higher and longer efficiency in the short-wave range compared to the MRF method. This also explains why the Ångström-Polishing process can generate particularly good roughness values in the short-wave range. The ION-Finish (orange line) is most effective in the long-wave range and achieves very good roughness results.

The decision which High-End-Finishing method is chosen depends on various factors. Specific customer requirements are particularly important, and asphericon will find the most efficient solution to achieve these requirements. Depending on the material and the required accuracy, the various High-End-Finishing processes generate optimized solutions for the best surface qualities in a variety of optics.

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