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Fig. 5. Image stacks simulated for conventional( a, b), interference( offset-reduced)( c, d) and confocal( e, f) microscopy assuming either 260 nm( a, c, e) or 300 nm( b, d, f) period length of the grating. TM polarized light with k = 505 nm is used. The microcylinder extends from x = �2.5 lm tox = 2.5 lm. The areas of interest for interference and confocal microscopy are marked in green.
leads to significant changes in the intensity distributions and the phase behavior for all three setups considered.
The analysis goes one step further by taking a closer look at confocal imaging in direct comparison with the measurement results shown in Section 4. Thus, assuming a sinusoidal structure( silicon, peak-to-peak amplitude 50 nm, K 1 = 260 nm and K 2 = 300 nm) and TM-polarized light( k = 505 nm), rigorous simulations are performed based on the model presented in Section 3 with and without microcylinder support. Near the resolution limit, the influence of the sample on phase / contrast of the simulated image stack is marginal. In order to obtain a meaningful evaluation of the results, two simulations are therefore carried out for each case, one of them with a phase shift of 180 ° of the sinusoidal structure as described in [ 17 ]. The difference between the results I( x, z) andI inv( x, z) is calculated, resulting in DI( x, z). Figure 6 shows the resulting intensity distributions.
Taking the difference DI( x, z) into account, the results can be interpreted as follows: if the information is still present in the contrast, some periodicity is visible in DI( x, z) and thus, the theoretical resolution capability can be obtained. If this is taken into account, it can be seen that the structure with 260 nm period length cannot be resolved by the confocal system without the microcylinder( Fig. 6b), but can be resolved with microcylinder-assistance( Fig. 6d). In contrast, for K 2 = 300 nm residues indicating a resolved structure can be observed in both cases( Figs. 6f and 6h).
The assumptions about the sinusoidal structure visible in the contrast, especially in the simulations with microcylinder support, are confirmed by the reconstructed