Masashi UESHIMA, Kenji AMAYA^*, and Kosei KATAOKA¹

Department of Mechanical and Environmental Informatics, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550, Japan
¹Katsura Opto Systems Co., Ltd., 1-1-1 Manpukuji, Kawasaki 215-0004, Japan

(Received July 14, 2008; Accepted November 14, 2008)

A ``practically applicable'' spot images based aberration retrieval method was developed. The method was systemized with the following techniques. 1) The real part and imaginary part of the spatial spectrum of the focal plane were expanded with the finite lower Zernike polynomials, respectively, and the method was reduced to the nonlinear least squares problem which calculates these coefficients. This technique will identify both the aberration and the intensity distribution of the spatial spectrum. 2) The intensity distributions of spot images were calculated using the Nijboer–Zernike polynomials in order to avoid a long calculation time and the numerical errors caused by Fourier transform or convolution. 3) Two noise reduction methods were applied to the present method, and some numerical and practical experiments were performed to demonstrate the technique's effectiveness. Four kinds of practical experiment based on theories were performed, and all of them showed good agreement with the theories.

Key words: aberration retrieval method, spot images, Nijboer–Zernike polynomial, noise reduction, optical pickup, inverse analysis

^*E-mail address: kamaya@a.mei.titech.ac.jp