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A model-based edge detection is always required when quantitatively evaluating the bidirectional measurements of micro- and nanostructures in optical microscopy. For example, the accurate determination of the width of a structure requires the knowledge of the location of the real physical edges in the measured profile. The interpretation of the measured edge profile cannot be performed intuitively due to distortion which is caused by diffraction and refraction. We advise a model-based edge detection algorithm which is based on rigorous simulations of the microscope’s imaging. The intensity level which corresponds to the position of the real physical edge is called the threshold and it is determined in the simulations. For these optical simulations we employ the JCMsuite, which is a software application of the finite-element-method (FEM). Since numerical and semi-analytical methods for the calculation of electromagnetics in optical systems rely to some degree on approximations, their results may vary even when the input parameters are identical. We apply a test suite of input parameters for the purpose of comparing numerical simulation tools regarding the resulting thresholds for measurements on line-shaped nanostructures in a periodic grating. The test suite maintains the illumination and imaging parameters of a transmitted light UV-microscope while the object parameters of a binary line grating are varied. There are 25 grating configurations with different line-to-space ratios, where the line width ranges from the resolution limit up to almost 10 µm. The illumination pupil is discretized in a cartesian grid with 113 grid points in total. We introduce different pupil samplings, after calculating the threshold values of the original test suite. We obtain a high agreement of the thresholds results and the related linewidth values when comparing with already performed results of two additional rigorous applications. Furthermore, we showcase the threshold variation for different samplings of the illumination pupil.
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