Figure 3.

Fluorescent beads with a diameter of 200 nm imaged with HELM (A) and standard fluorescence microscopy (B). (Bar = 1 μm.) The microscope system as well as the specimen preparation are identical to those described for Fig. 2. The center distance of the tightly packed beads approximates the Rayleigh limit of 240 nm. The almost invisible contrast dip between the individual beads in B is a consequence of the fact that the beads are not point sources. Furthermore, one has to take into account that, for water-immersed beads, the effective NA of the objective (nominal: 1.4) becomes smaller (28).