Comment on “Theoretical analysis of numerical aperture increasing lens microscopy” [J. Appl. Phys. 97, 053105 (2005)]

In a recent paper, Ippolito et al. [J. Appl. Phys. 97, 053105 (2005)] analyzed focusing at high numerical aperture into a dielectric medium. They considered three geometries, those of focusing through a level planar interface and through spherical interfaces arranged in concentric or aplanatic positions. The treatment for focusing through a planar interface is based on a different model from that presented elsewhere. It is shown that this model describes the aberration effect only approximately, in contrast to the previous, rigorous treatment.