The mechanical stiffness of sandwich type structures are unmatched compared to other light weight methods. Hextek structured blanks have been analyzed for optical performance using sophisticated finite element analysis to accurately predict the optical surface deformation of a mirror under a variety of orientations. Customers who have convinced themselves through FEA analysis that our substrates (beyond one meter in diameter) can hold tight optical specifications and include; the Astronomical Research Consortium, Hofstadter Analytical Services, ITT Geospatial Systems, Large Binocular Telescope, Lawrence Livermore National Labs, Los Alamos National Labs, Lowell Observatory, Northrup Grumman, Ohio State University, Subaru Telescope, University of Chicago, University of Arizona, University of Oxford and University of Washington among others. The essential conclusion is that Hextek substrates offer the best stiffness to weight ratio when compared to any other light weight mirror design. Some examples of a simple 16″ diameter mirror deflection (with a center hub support only) results appear below courtesy of Hofstadter Analytical Services:
 Tapered Mirror 52nm deflection (12.2 kg) |
 Ribbed Mirror 41nm deflection (9.9 kg) |
 Ribs with Taper 62nm deflection |
 Hextek mirror 50nm deflection |
The deflection of the Hextek model is very respectable compared to the other configurations with a hub only type of mounting profile at 50nm. For Hextek substrates a whiffle-tree type mounting system provides optimal support. Using this common support method the optical surface deflections reduce to below 10nm for our mirrors. This subject is treated rigorously and verifies the above conclusions in a book by Ahmad, Anees, ed. “Lightweight Mirror Design.” Handbook of Optomechanical Engineering New York 1997: 125 – 148. Given a mirror design, Hextek Corporation can provide a first order finite element data that predicts mirror deflections and help optimize mirror support locations as part of the design process.
