IMPROVED PERFORMANCE OF ADAPTIVE OPTICS IN THE VISIBLE

A simple tip-tilt adaptive optics system can improve the peak intensity of the corrected image in the infrared by a factor of 2 to 3 compared with that of the uncorrected image. With conventional methods this performance cannot be achieved in the visible unless flexible mirrors are used. A method of improving the peak intensity in the visible by a factor of 8 to 10 compared with that of the uncorrected image by use of a simple tip - tilt mirror is presented. To achieve this improvement, the effective wave aberration, that is, the aberration modulo 2pi, is used to obtain tilt and defocus of the turbulent wave front. It is shown that correcting the effective aberration is the equivalent in Fourier space of shift-and-add in image space, that is, moving the brightest speckle to the image center. Christou [Pub. Astron. Soc. Pac. 103, 1040 (1991)] has demonstrated the potential of a tip-tilt system when using shift-and-add. Operating in Fourier space rather than in image space offers the advantage of being independent of the type of object to be used for the correction. Additionally, this method is applied to the correction of defocus by determination of the brightest speckle in the three-dimensional image space. Thus the full potential of a rigid-mirror adaptive optics system is demonstrated.