Extending the field of view of an adaptively corrected telescope by longitudinal pupil displacement

A simple scheme is proposed to increase the corrected field of view of a telescope equipped with adaptive optics. The optical system's entrance pupil is projected forward into the atmosphere and is slightly reduced in size. The field in any given direction is then imaged through just a portion of the main aperture, while the full aperture is used to collect light from the reference beacons, which may be either natural stars or laser beacons. The enlargement of the field of view is proportional to the reduction in pupil size and therefore comes at some cost in flux and resolution. A numerical simulation shows that the trade-off is modest and may in many cases be advantageous.