Correction of secondary intensity maxima in a multidither, hill-climbing, adaptive optical system

A method for correcting the intensities of secondary maxima dependent on phase errors in a multidither, hill-climbing adaptive optical system for improving the focused power characteristics of laser systems is presented. The method involved the sampling and focusing of the beam containing secondary maxima varying with a period of 2 pi relative to the phase error onto a variable aperture which changes the sign of the error signal when it is of sufficient size to transmit a spatially averaged diffraction pattern to the photovoltaic detector of the servo. The system has been applied to a nine-zone local-loop adaptive optical system, which has demonstrated the convergence of the technique. A simple one-dimensional model shows that the error components in certain regions of the diffraction pattern are shifted in phase by -pi from the axial components, allowing the correction of the 2 pi state near the first side-lobe maximum.