25 September 2008 Toward picometer optical figuring of ultra-precision optical components using multi-aperture deposition techniques
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The process of fabricating optical surfaces has remained relatively unchanged for hundreds of years and only within the last 10-20 years have significant improvements been made to the basic techniques of manual polishing. Various deterministic grinding, etching, and polishing machines are now available that can generate free-form optical surfaces by sub-aperture removal of surface material. This presentation will concentrate on a new technique for deterministic surface correction that is achieved using selective deposition of an index matched material simultaneously over the entire surface of the optic. The technique uses a multi-aperture mask to selectively occlude the plume from a physical vapour deposition system. The mask design has two functions; firstly to remove the inherent variation in the plume itself; and secondly, to create the required spatially varying layer to correct or form the final optical shape. This ability to correct the entire surface of the optic simultaneously has the considerable advantage that the corrections are achieved in a very short space of time and deposition times of 100-300 seconds are typical. A further advantage of this technique is that the surface roughness does not seem to be affected by the deposition process, and so the surface quality of the optic is maintained throughout the correction process. The technique has been successfully applied to both transmissive and reflective optics and has achieved uniformities of λ/1000 rms. During the talk I will present our latest results and progress towards selective etching, full edge correction, and spatially varying thin-film filter deposition.
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John W. Arkwright, John W. Arkwright, Jan Burke, Jan Burke, Mark Gross, Mark Gross, "Toward picometer optical figuring of ultra-precision optical components using multi-aperture deposition techniques", Proc. SPIE 7101, Advances in Optical Thin Films III, 71010M (25 September 2008); doi: 10.1117/12.800402; https://doi.org/10.1117/12.800402

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