Absolute Instruments as Laser Guide Star Adaptive Optics relays

Laser Guide Star Adaptive Optics (LGSAO) systems require an optical relay to produce images of both the telescope focal surface, and of laser guide stars. Laser guide stars imaged by the telescope lie at a range of axial distances from the telescope focal surface. Further, such relays are required to produce sharp metapupils and exit pupil. "Absolute Instruments" are optical systems which provide an image of the entire 3-dimensional object-space of the system that is free of distortion, curvature and point-blurring aberrations. Such systems are well-matched to the requirements of LGSAO systems. In this paper it will be shown that such systems can provide excellent image quality for the science field as well as for any practical range of LGS objects. Further, by splitting the correcting plate that transforms an ordinary relay into an absolute instrument, simultaneous near-perfect correction of metapupils and exit pupil can be achieved with no compromise to the relays' imaging properties.