The two-and three-cluster fish bone optical model with hard core correlations is derived from the corresponding resonating group model. The nuclear saturation effect is represented by three different features of inter-cluster interactions: i) by the non-local exchange potential, ii) by a reduced attraction in the region of overlapping clusters, iii)by an effective three-cluster potential. Comparability of the microscopic theory with phenomenological models is established by two off-shell transformations which orthogonalize function bases and avoid appearance of artificial three-body forces.