Focal field simulations. Focal field calculations were applied to investigate the effects of primary classical aberrations on the PSFs created by different binary PMs upon focusing the corresponding circularly polarized pupil function with a high NA objective. Thus, phase modulation experiments could be verified under strictly controlled conditions regarding misalignment and aberration. To account for significant contributions of polarization effects when focusing with a high NA objective lens, the vectorial diffraction theory of Richards and Wolf 26,27 was applied, to compute focal fields and intensity distributions. 2D-Fast Fourier Transform (FFT) operations allow for efficient computation of vectorial Debye integrals for arbitrary polarization states of the pupil function 14,28 and were used in the implementation of Boruah and Neil 14 . Comparison of simulation results with experimental **data** confirmed the correctness of our implementation.