## 3 Results
### Analyzing the Grating Quality in a Radiography Setup  
We tested the developed two-dimensional grating structures using a radiographic setup at the TopoTomo beamline of the Karlsruhe synchrotron radiation facility (Karlsruhe, Germany). The measurements were performed at the energy of 8.5 keV utilizing an optical system to introduce 9\(\times\) effective magnification. The detector was a Neo sCMOS camera (Andor Technology Ltd., Belfast, UK) with an effective pixel size of 0.72 \(\upmu\)m and the field of view of 2560 \(\times\) 2140 pixels. The grating was placed 8 cm from the detector. The tested gratings were gold square pillars of 15 \(\upmu\)m height with 10 \(\upmu\)m, 25 \(\upmu\)m, and 50 \(\upmu\)m periods in both the vertical and horizontal directions, manufactured on the same 200-\(\upmu\)m-thick silicon substrate with an oxidized titanium layer. The average WFM introduced by the gratings according to the Equation (1) was 0.88. To test the robustness of the analysis algorithm we chose the gratings with several technologically-driven defects to impose challenges to the data interpretation. Our intention was to explore possibilities of decoupling the influence of typical fabrication issues using the data obtained from the projection image. The specimen has several defects in the photoresist pattern due to local adhesion issues, which were eliminated for other specimens by careful cleaning. As a consequence, the final pattern suffered from the overplating of gold on top of the photoresist layer, as shown in Figure 5a, diffraction-induced shape distortion, as represented in Figure 5b, and the impurity of the inter-structure areas and particle formation during electroplating, which can be seen in Figure 5c. Radiographic images were obtained with only the gratings in the beam path. The fragments of the images are shown in Figure 6c. Flat-field images without the gratings were obtained to correct the resulting image considering the beam shape and estimated detector noise. The exposure time for all acquired images was the same. As one can see in Figure 6a, there is a strong deviation of the background from the mean value and moreover, it has a highly inhomogeneous distribution over the whole detector area. The detector signal (recorded intensity) was composed of two Gaussians as shown in Figure 6b, which means that the illuminated detector area has two main intensity values (around  
Figure 5: SEM images of the gratings chosen to test the robustness of the characterization algorithm by radiographic projection analysis: (**a**) the illustration of the gold overplating (grating before photoresist stripping); (**b**) illustration of pattern impurity and shape distortion caused by diffraction limit; and (**c**) large particle formation during electroplating. 7500 a.u. and 8500 a.u.). The mean value for the whole distribution was around 8400 a.u. Such an effect could be either due to a non-uniform beam or detector response. Considering the inhomogeneity of the background, special attention was paid to the normalization of the data. For each grating projection, the respective flat-field image was subtracted from the data and further correction by the absorption of the substrate was applied. Relative absorption signal histograms (i.e., the number of counts associated with a certain absorption level) were plotted by applying 3 \(\times\) 3 median filters for pixel-noise removal to qualitatively characterize the intensity modulation introduced by the gratings. As one can see in Figure 6c, the intensity distribution peaks for gratings of periods 50 \(\upmu\)m and 25 \(\upmu\)m are clearly separated. However, there is still a splitting of the absorption signal peak around 400 a.u. for the 25 \(\upmu\)m period grating and around 430 a.u. for 50 \(\upmu\)m period grating. For the 10 \(\upmu\)m period, there was no clear separation of peaks observed, but, rather, an overlapping of at least three Gaussians centered at 0 a.u., 110 a.u., and 250 a.u.