Zernike modal compensation analysis for an adaptive optics system using direct-gradient wavefront reconstruction algorithm.

Power spectra function was used usually to describe the time domain characteristic of atmosphere disturbed wavefront. Power spectra reject function, which defines as the ratio of the power spectra function of the close-loop compensated wavefront to the open-loop disturbed wavefront, was used to describe the control effect of an adaptive optical system. in this paper the control effect of the Zernike wavefront medals for an adaptive optical system using direct-gradient wavefront reconstruction algorithm was analyzed by using the power spectra reject function of Zernike model coefficients. The dynamic models of Zernike modal compensation for the direct-gradient algorithm were established. The power spectra reject functions were calculated from the theoretic model and compared with those gotten from experimental data. It is showed that there is coupling between some Zernike medals while using the direct-gradient algorithm. Although the control bandwidth was affected slightly, the power spectra reject function of the coupled Zernike modals become worse at low frequency range, this causes the wavefront compensation effect descended to some degree.