Development of active/adaptive lightweight optics for the next generation of telescopes

M. Ghigo; S. Basso; O. Citterio; F. Mazzoleni; D. Vernani

doi:10.1117/12.674055

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30 May 2006 Development of active/adaptive lightweight optics for the next generation of telescopes

M. Ghigo, S. Basso, O. Citterio, F. Mazzoleni, D. Vernani

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Proceedings Volume 6148, 2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes; 61480E (2006) https://doi.org/10.1117/12.674055
Event: 2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies, 2005, Xian, China

Abstract

The future large optical telescopes will have such large dimensions to require innovative technical solutions either in the engineering and optical fields. Their optics will have dimensions ranging from 30 to 100 m. and will be segmented. It is necessary to develop a cost effective industrial process, fast and efficient, to create the thousands of segments neeededs to assemble the mirrors of these instruments. INAF-OAB (Astronomical Observatory of Brera) is developing with INAF-Arcetri (Florence Astronomical Observatory) a method of production of lightweight glass optics that is suitable for the manufacturing of these segments. These optics will be also probably active and therefore the segments have to be thin, light and relatively flexible. The same requirements are valid also for the secondary adaptive mirrors foreseen for these telescopes and that therefore will benefit from the same technology. The technique under investigation foresees the thermal slumping of thin glass segments using a high quality ceramic mold (master). The sheet of glass is placed onto the mold and then, by means of a suitable thermal cycle, the glass is softened and its shape is changed copying the master shape. At the end of the slumping the correction of the remaining errors will be performed using the Ion Beam Figuring technique, a non-contact deterministic technique. To reduce the time spent for the correction it will be necessary to have shape errors on the segments as small as possible. A very preliminary series of experiments already performed on reduced size segments have shown that it is possible to copy a master shape with high accuracy (few microns PV) and it is very likely that copy accuracies of 1 micron or less are possible. The paper presents in detail the concepts of the proposed process and describes our current efforts that are aimed at the production of a scaled demonstrative adaptive segment of 50 cm of diameter.

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M. Ghigo, S. Basso, O. Citterio, F. Mazzoleni, and D. Vernani "Development of active/adaptive lightweight optics for the next generation of telescopes", Proc. SPIE 6148, 2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 61480E (30 May 2006); https://doi.org/10.1117/12.674055

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