The information content of aberrated- and non aberrated images generated by coherently- or incoherently illuminated objects

The calculation of the information content of an ideal image rests on two different mathematical approaches: The expansion of the field into either the a) coherent modes, or b) into the the sampling functions occurring at the r.h.s. of 1. The coherent mode approach leads to analytical results for a few special cases only, (rectangular- circular apertures), whereas the sampling method can be generalised in such a way that the distribution of the sampling points is known explicitly for al possible shapes of the apertures, thus obtaining optimal sampling!.