M. Kowalczyk et al., PHASE PUPIL FILTERS FOR IMPROVEMENT OF THE AXIAL RESOLUTION IN CONFOCAL SCANNING MICROSCOPY, Optica Applicata, 28(2), 1998, pp. 127-137
Two phase pupil filters whose axial impulse response is asymmetric wit
h respect to the focal point ale proposed. It is shown that when eithe
r of the filters is placed both in the illuminating and collecting par
t of the system the impulse respon se becomes symmetric and the axial
resolution increases The filters are designed on the basis of the Four
ier-transform properties of the Hermitian functions. They consist of a
small number of zones (less than or equal to 3) whose amplitude trans
mittance is constant and its module is equal to unity. The width of al
l zones is adequately chosen. Several quantitative characteristics of
the proposed filters which evidence the improvement of the axial resol
ution are presented.