Edge-matched segmented mirrors for adaptive optics

The use of segmented mirrors in astronomy and adaptive optics is increasing as the ability to measure and control the position of the individual segments to a fraction of the wavelength of light becomes possible. A novel technique is presented in which the relative piston error of adjacent segments is measured using inductive edge-sensors. This technique alleviates the need to have an absolute piston sensor for each of the segment. Modelling of the performance of such a mirror for the case of correcting atmospheric turbulence is presented. This modelling shows that an edge-matched segmented mirror can correct the piston errors in the wavefront even though it does not sense them directly. In addition to this modelling, an experiment. which demonstrates the utility of this technology for adaptive secondary mirrors is described. The results of this experiment, which demonstrates for the first time that an edge-matched mirror can correct for atmospheric piston errors, are presented.