One of the most important components in microscopy is the illumination and imaging numerical aperture (NA). Together with the wavelength it sets the final limits and capabilities of the microscopy system. In scatterometry and ptychography a precise knowledge of the NA is required for the reconstruction algorithm. Here the uncertainty of values supplied by the manufactures are often to large, impairing the measurement capability of the system. In this research we demonstrate a method to measure the numerical aperture with high precision and thereby improve optical microscopy measurements.

19^th IMEKO TC10 Conference "Measurement for Diagnostics, Optimisation and Control to Support Sustainability and Resilience"