Replacing a thin lens by a thick lens

This paper deals with the problem of replacing a thin lens by a thick lens with approximately the same properties as the thin lens. Equations enabling the calculation of the parameters of a thick lens that has the same focal length and the same value for one of the Seidel aberration coefficients (either the Seidel aberration coefficient of spherical aberration or the Seidel aberration coefficient of coma) as the thin lens are derived. A comparison of the proposed method for calculating the parameters of the thick lens with existing methods is given in examples. Further, the problem of replacing a thick lens made of optical glass with a given refractive index by another thick lens with a different refractive index but with the same focal length and the same Seidel aberration coefficient of spherical aberration is investigated.