Research progress of co-phasing inductance edge sensor for Chinese extremely large telescope

Edge sensor is one of the most important technologies for the extremely large segmented primary telescopes like Keck, Thirty Meter Telescope (TMT), European Extremely Large Telescope (E-ELT) and Chinese Future Giant Telescope (CFGT) for control of out-of-plane degrees of freedom. Different from the capacity edge sensor from Keck and TMT, one kind of an inductance edge sensor is proposed and applied with the similar principle and configuration, fine aligned and tested in this paper to try to realize the same co-focusing or co-phasing maintenance purpose and high accuracy of relative piston and tip/tilt degrees of freedom of the segments. The sensor is also considered and modified to much more sensitive to dihedral angle between the neighboring segments. Finally some preliminary conclusions are reached.