Influence of wave aberrations on MTF measurements modelled by the pupil function

When light passes through a system of optical components, each of them will cause a certain phase transformation depending on its form and refractive index. The point spread function (PSF) of an optical system may be modelled as the Fraunhofer diffraction pattern of its complex pupil function, which, including all multiplicative phase transformations acquired while passing the system, finally emerges from the exit pupil. For a diffraction limited system, the wavefront at the exit pupil is assumed to be illuminated by a perfectly spherical wave. In the presence of aberrations, these are modelled as additional wavefront form errors in the complex pupil function. In this contribution a numerical model based on Huygens-Fresnel principle and the complex pupil function is employed to demonstrate the influence of different wavefront errors modelled by Zernike polynomials on the PSF and its associated MTF. The results will be employed in the estimation of the measurement uncertainty in the multi camera MTF measurement setup at PTB [1]. [1] Schake M., Schulz M., "Identification of aliasing effects in measurements of unknown MTFs," Proc. SPIE 11899 0H, (2021).