Development of light-weight spherical mirrors for RICH detectors

Glass-coated beryllium and carbon-fiber light-weight spherical mirrors, with radii of curvature of $\sim$ 2700mm, have been successfully developed and tested as part of the LHCb RICH experimental programme. The low mass mirror is necessary to minimize the amount of material within the LHCb spectrometer acceptance, with a requirement of less than 2% of a radiation length. Both technologies are suitable for light-weight mirror applications. The R&D and characterization of the mirrors are reported.