(Upper left and lower left) Horizontal and vertical slices through the reconstructed focal intensity (Dataset 3). In contrast to Datasets 1 and 2 here a smaller pinhole (diameter = 1.4 µm) has been used which significantly influences the focal intensity distribution. Here the beam-defining slits S1H and S1V were set to 0.1 mm. Graphs are analogous to those of Fig. 4. (Upper right and lower right) Even though in the numerically determined focal plane a double-focus is visible, the small pinhole P2 drastically reduces the side lobes in the focal plane. After further propagation to ∼1.6 mm downstream of the reconstruction plane the wavefield becomes a single focus in the horizontal and vertical directions and adopts almost a Gaussian shape (see Fig. 7).