Analysis of the intensity profiles of Fig 3.

<p>Top: Points of maximum slope in the transmitted signal for light-to-shadow transitions (circle) and shadow-to-light transition (triangle) of each bar in the sample side (blue) and reference side (magenta), <i>r</i>^(<i>obs</i>), plotted against the ideally expected position of the line edges, r(exp), given the known pitch of <i>p</i>⁰ = 0.999748 mm and known line width of 0.228 mm. Due to the unknown overall radial position of the mask, the expected positions have the same arbitrary offset. Bottom: Difference between the radii of the measured transitions and the expected location of the edges of the mask. Slopes in this plot visually highlight differences in the pitch. Irrespective of the pitch, for a mask with perfect rotational alignment, the difference between measured and ideally expected edge positions would be the same for corresponding edges in the reference and sample side, i.e., equivalent blue and magenta symbols would not be offset. The observed (≈50 <i>μ</i>m) displacement between sample and reference transitions seen from the vertical shift between blue and magenta symbols in the bottom panel reveal rotational misalignment, here corresponding to 0.51°. This rotation will also change the measured pitch along the line of measurement very slightly, making it larger by <i>p</i>⁰/<i>cos</i>(<i>α</i>) − <i>p</i>⁰, which here amounts to 0.04 <i>μ</i>m. The displacement between triangles and circles reflects the difference between observed and designed linewidth, a feature not utilized in the analysis due to its susceptibility to optical misalignment and the detailed shape of the measured transitions.