Conformal window manufacturing process development and demonstration for polycrystalline materials

Nathan E. Smith; Alan R. Gould; Tom Hordin; Kate Medicus; Mark Walters; Matthew Brophy; Jessica DeGroote Nelson

doi:10.1117/12.2027735

15 October 2013 Conformal window manufacturing process development and demonstration for polycrystalline materials

Nathan E. Smith, Alan R. Gould, Tom Hordin, Kate Medicus, Mark Walters, Matthew Brophy, Jessica DeGroote Nelson

Proceedings Volume 8884, Optifab 2013; 88840R (2013) https://doi.org/10.1117/12.2027735
Event: SPIE Optifab, 2013, Rochester, New York, United States

Abstract

Conformal windows pose new and unique challenges to manufacturing due to the shape, measurement of, and requested hard polycrystalline materials. Their non-rotationally symmetric shape and high departure surfaces do not lend themselves to traditional optical fabrication processes. The hard crystalline materials are another challenge due to increased processing time and possibility of grain decoration. We have developed and demonstrated a process for manufacturing various conformal windows out of fused silica, glass, zinc-sulfide multispectral, and spinel. The current process involves CNC generation/grinding, VIBE polishing, and sub-aperture figure correction. The CNC generation step incorporates an ultrasonic assisted grinding machine; the machine settings and tool are being continuously optimized for minimal sub-surface damage and surface form error. In VIBE, polishing to less than 5 nm rms surface roughness while maintaining overall form error is accomplished with a full aperture conformal polishing tool and with rapid removal rates. The final sub-aperture polishing step corrects the overall form error. Currently we utilize our CMM for surface form measurement and have shown that we can produce spinel conformal windows with form error within ±10 micrometers of the nominal shape, without grain decoration. This conformal window manufacturing process is continuously optimized for cost reduction and precision of the final optic.

Citation Download Citation

Nathan E. Smith, Alan R. Gould, Tom Hordin, Kate Medicus, Mark Walters, Matthew Brophy, and Jessica DeGroote Nelson "Conformal window manufacturing process development and demonstration for polycrystalline materials", Proc. SPIE 8884, Optifab 2013, 88840R (15 October 2013); https://doi.org/10.1117/12.2027735

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