The chromatic aberration of magnetic lenses with the field distribution in the form B(Z)˛Zn, for all integer
n, have been studied as objective and projector lenses. These aberrations can be expressed in terms of
Bessel function of the first and second type of the order 1/2n(n + 1). For this reason we resort to digital
calculation. Care should be taking when making comparisons between positive and negative n value.