Confocal imaging through weakly aberrating media

The effect on confocal imaging of spherical aberration caused by a weak ref ractive-index mismatch is discussed. Aberration balancing that uses a chang e in the objective's tube length is studied. It is found that the range of depths that can be imaged satisfactorily by a high-numerical-aperture objec tive with compensation is an order of magnitude greater than that without c ompensation. The aberration balancing tends to break down for extremely hig h numerical apertures. (C) 2000 Optical Society of America. OCIS codes: 080 .1010, 110.0180, 180.1790, 260.1960, 110.2990.