Mirror surface figure evaluation based on power spectral density

Firstly,Power Spectral Density( PSD) is proposed for mirror surface figure evaluation in the large aperture telescope system as for some difficulties for Root Mean Square( RMS) in the evaluation of large scale variety and disadvantage of robust for rigid body displacement. Then,the decomposition arithmetic of PSD is analyzed with Zernike polynomial,and Zernike polynomial spectrum energy distribution is analyzed in some order. The algorithm has been used in the surface figure evaluation of a Φ 500 mm mirror,and energy distribution in the frequency domain of the actual mirror surface has been obtained. The experimental results indicate that the evaluation of PSD is more practical when used in large aperture mirror for their manufacture and testing and for the error budget allocation in telescope system. Finally,a kind of noncorrelative sub-aperture stitching method for evaluation of reflective mirror shape based on PSD is proposed which can be used in the large aperture telescope.