I’m modeling microscope objectives with at NA > 0.5 and interested in knowing the PSF or alternatively how much energy is contained in the central lobe at a given beam radius. Depending on which direction rays are traced through the objective, I obtain a different amount of energy in the central lobe (either 65% or 84%), even when using the Huygens PSF and Diffraction Encircled Energy function.

For high NA (>0.5) lenses, I think much less than 84% of the energy should be in the central lobe (it doesn’t technically have a diffraction pattern unless the NA is low). How do we know whether Huygens PSF is working correctly? The results seem to depend a lot on the aperture setting, even when the rays traced in the Cross-Section look the same.