Shaping of thin glass foils for the fabrication of mirrors with pronounced asphericity

We present a method developed by INAF (Italian National Institute for Astrophysics) for the manufacturing of mirrors by using commercial of-the-shelf materials. It is based on the shaping of thin glass foils by means of forced bending; then a sandwich structure is assembled for retaining the imposed shape. These mirrors are intended for optical systems with few arcmin in angular resolution working in extreme environments, being their principal mechanical features the very low weight and high rigidity. The cost and production time also turns to be very competitive. In this paper we report the main achievements of the R&D performed. We recall the investigation of the theoretical limits with finite element analyses and the process implementation. Finally, the case of the mirrors for IACT (Imaging Atmospheric Cherenkov Telescope) is presented with respect to the ASTRI project (Astrofisica con Specchi a Tecnologia Replicante Italiana).