Optical design of the Dragonfly interferometric imager

Dragonfly is designed to overcome the blurring effects of the Earth's atmosphere and achieve high dynamic range observations of bright objects close to the diffraction limit of a large ground-based telescope. Injection of the sub-pupil images into single-mode fibres will provide both spatial filtering and reformatting of the redundant pupil array into a non-redundant output suitable for interferometry. We describe the optical system which includes (i) interface with an Adaptive Optics system (ii) pupil fragmentation and injection into 36 single-mode fibres (iii) fibre path-length matching (iv) a beam combiner with spectral dispersion and output to a Low Light Level CCD detector.