Patent ID: 7826329

Claim:
An apparatus comprising: a first compensation lens comprising a plurality of electrodes interleaved with a plurality of compensation planes comprising a material having a variable index of refraction; each compensation plane of the plurality of compensation planes having a refractive index that varies according to compensation voltages applied to electrodes adjacent to the compensation plane; a voltage source configured to provide a plurality of compensation voltages to the first compensation lens; wherein the compensation voltages are a function of a compensation plane index i (where i=1 to N) and wherein the compensation voltages substantially conform to an N th order compensation equation comprising coefficients corresponding to even powers of the compensation plane index i in the compensation equation and wherein all coefficients that correspond to odd powers of the compensation index i are substantially equal to zero, the compensation voltages corresponding to the coefficients of the even powers of the compensation plane index i; a second compensation lens comprising a plurality of electrodes interleaved with a plurality of compensation planes, the second compensation lens substantially coaxial to the first compensation lens, wherein the compensation planes of the second compensation lens are substantially perpendicular to the compensation planes of the first compensation lens; an optimization module configured to optimize coefficients of the Nth order compensation equation to determine the compensation voltages for the first compensation lens by initializing the coefficients, executing the coefficients, testing for data errors, perturbing the coefficients, and identifying optimum coefficients, each coefficient perturbed based on a search matrix corresponding to the coefficient, each search matrix comprising a coefficient and a plurality of possible offsets from the coefficient; and a displaceable focus lens that is positioned a distance Dm from a data layer m in an optical media.