Generating curved deformable facesheets via free form slumping

Philip M. Hinz; Matt Radovan; Daren Dillon

doi:10.1117/12.2630714

29 August 2022 Generating curved deformable facesheets via free form slumping

Philip M. Hinz, Matt Radovan, Daren Dillon

Proceedings Volume 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V; 121880T (2022) https://doi.org/10.1117/12.2630714
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

Adaptive Secondary Mirrors (ASM’s) provide telescope-integrated adaptive optics (AO) correction, potentially broadening the use of AO on the facility. However, unlike post-focal plane AO systems, ASM’s require large, curved, aspheric membranes to replicate the standard telescope secondary mirror that it replaces. Electromagnetic actuator technology has been developed to implement ASM’s, but the devices require 200-1500 mm diameter curved facesheets. We describe an approach for fabrication of these facesheets that uses a hot thermal forming process, or slumping. This technique traditionally relies on an accurate negative form to slump the glass into. We take a different approach of letting the glass slump freely within a support ring that is outside the final required optical diameter of the shell. Such an approach allows for creation of shells over a variety of radii of curvature, simply by changing details of the heating process. However, to create an approximately parabolic shape, an additional force is required. We model the expected deformation, showing that a top weight with a given force just outside the optical diameter creates close to the desired shape. Experimental verification of this has been carried out for shells 120 mm in diameter. We are exploring optimum forming fixtures for this approach and scaling this process to larger facesheets needed for upcoming ASM’s.

Conference Presentation

Citation Download Citation

Philip M. Hinz, Matt Radovan, and Daren Dillon "Generating curved deformable facesheets via free form slumping", Proc. SPIE 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V, 121880T (29 August 2022); https://doi.org/10.1117/12.2630714

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