The importance of proper phasing to segmented telescopes can scarcely be overstated. Even for imaging through the turbulent atmosphere, phasing can have an enormous impact. While phasing makes little difference at a wavelength of 0.5 m, even a phase error of 100 nm begins to have an effect at a wavelength of 2 m. 20 cm, for a variety of wavelengths and piston errors of the primary mirror segments. The profiles have been averaged over an ensemble of configurations which are consistent with the given RMS piston error.
All plots are to the same scale.
Note the devastating effects of phase errors at the longer wavelengths. This paper is organized as follows. In Section 2 we describe the three techniques qualitatively. In Section 3 we present a brief overview of the theory underlying each technique. In Section 4 we summarize the experimental results obtained with the three techniques and give a quantitative comparison.