Pupil aberrations do not directly impact image quality, although in some circumstances they may lead to localized shadowing within an image.  In your case, the optical system is very close to being diffraction limited, so the image quality should be quite good for spatial frequencies below the incoherent imaging cutoff frequency. 

However, if the field height of the object is set too small, then the object will contain high spatial frequencies above cutoff and the image will look blurred (when the Aberrations setting for Image Simulation is set to “Diffraction”).  A similar thing can happen for the “Geometric” aberration setting if the image pixel size is on the order of the transverse ray aberration (even if the ray aberration is very small, within the Airy disk, but still finite).  Here’s an example using two paraxial lenses with a little bit of defocus added:

The object space is set to be telecentric, which means the entrance pupil is at infinity.  However, I’ve set the stop surface to be at the second lens, which is not in the back focal plane of the first lens, so the image of this stop surface as viewed from object space is *not* at infinity.  As a result there is pupil aberration.  I also added a small amount of defocus to create a finite amount of ray aberration.

Here is the Image Simulation with a small field height:

Significant image blur arises.  If the “Telecentric Object Space” setting is turned off, the pupil aberration vanishes, but the image results remain the same.

However, if the object field height is increased by 10X, the image looks much better because the image pixel size is now large compared to the ray aberration:

So, my suggestion is to check your Image Simulation settings, in particular the Field Height value. 

Hope this helps..

Regards,

Jeff

Thanks , Jeff and Mark.