Adaptive optics (AO) is a technology that corrects in real time for the blurring e †ects of atmospheric turbulence, in principle allowing Earth-bound telescopes to achieve their di †raction limit and to "" see ÏÏ as clearly as if they were in space. The power of AO using natural guide stars has been amply demonstrated in recent years on telescopes up to 3È4 m in diameter. The next breakthrough in astronomical resolution was expected to occur with the implementation of AO on the new generation of large, 8È10 m diameter telescopes. In this paper we report the initial results from the Ðrst of these AO systems, now coming on line on the 10 m diameter Keck II Telescope. The results include the highest angular resolution images ever obtained from a single telescope and at 0.85 and 1.65 km wavelengths, respectively), as well (0A .022 0A .040 as tests of system performance on three astronomical targets.
A diffractive Alvarez lens is demonstrated that consists of two separate phase plates, each having complementary 16-level surface-relief profiles that contain cubic phase delays. Translation of these two components in the plane of the phase plates is shown to produce a variable astigmatic focus. Both spherical and cylindrical phase profiles are demonstrated with good accuracy, and the discrete surface-relief features are shown to cause less than lambda/10 wave-front aberration in the transmitted wave front over a 40 mm x 80 mm region.
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