Generalized Fresnel lenses with curved entrance diopters are investigated with the aim of checking which curvature produces the best correction from off-axis aberrations. The beam propagation method (BPM) is used to assess the performance of a waveguide Fresnel lens with given parameters (f number=4.6, delta n=0.0822 at lambda =830 nm): it is shown that the lenses having circular or parabolic front diopters (which almost coincide in the paraxial approximation) are corrected from third-order aberrations over a field of view of several degrees. The effect of chromatic aberration is also evaluated.