Abstract

Adaptative optics can improve the imaging of ground based telescopes near the diffraction limit in spite of atmospheric turbulence. Laser excitation of the mesospheric sodium layer have been proposed and experimentally investigated as a synthetic beacon for wavefront correction.^1,2 However, this technique suffers from a major drawback: tip-tilt induced by the atmospheric refraction cannot be measured because of the principle of the inverse return of light. A polychromatic guidestar has thus recently been proposed to measure this tip-tilt effect.³

© 1999 Optical Society of America