title: Design of an interferometric system for the measurement of phasing errors in segmented mirrors.
abstract: One of the new problems that has to be solved for segmented mirrors is related to periodic phasing, because for such mirrors to exhibit diffraction-limited performance the segments have to be positioned with an accuracy of a fraction of a wavelength. We describe the optical design of an instrument that measures the phasing errors (i.e., tip, tilt, and piston) between two segments under daylight conditions. Its design is based on a high-aperture white-light Michelson interferometer. It was developed at the Center for Sensors, Instruments and Systems Development (CD6) of the Technical University of Catalunya, Spain, and its final testing was carried out on the Gran Telescopio Canarias test workbench.
authors.affiliation: Center for Sensors, Instruments and Systems Development, Technial University of Catalunya, Terrassa, Spain. pizarro@oo.upc.es
authors.forename: Caries
authors.initials: C
authors.lastname: Pizarro
authors.forename: Josep
authors.initials: J
authors.lastname: Arasa
authors.forename: Ferran
authors.initials: F
authors.lastname: Laguarta
authors.forename: Núria
authors.initials: N
authors.lastname: Tomàs
authors.forename: Agustí
authors.initials: A
authors.lastname: Pintó