One thing slipped my mind:  In the example file I should have checked Telecentric Object Space under aperture so that the emissions from the fiber are directed axially. It makes little difference in this case, but could be significant in some designs.

Thanks David!  This is really helpful.

I ran geometric image analysis and, in the defocused region, I got a spot diameter of a few millimeters.  This seems to be consistent with the spot diagrams, as rays from a point were spread out over a similar diameter (and since the object is much smaller than the defocused spot, it should approximate to a point source fairly well).

I did have a question however: I tried to do a parallel simulation using physical optics propagation with a top hat of the same width as the disk image and the results were completely different.  Instead of a spot diameter spread over a few millimeters, I got something like an Airy disc with a much smaller total diameter (~7X smaller).  Maybe there is something about one of these analysis methods that I’m missing.  Do you have some thought on the reason for the discrepancy?

Also, I noticed that if I turn telecentric object space on and then off, it doesn’t seem to revert unless I undo.  Do you know if checking that option changes some other parameter?

Thanks again!

Hi Ryan,

I don’t have any problem moving back and forth to telecentric space. In my file, I judge that by the automatic clear aperture of the paraxial lens, which switches back and forth, and also by the GIA results.

Regarding the comparison with POP, you are really simulating two different sources. In the GIA ray tracing case there is an extended source, where each point on the extended sources emits over the 0.12 NA aperture, with no phase coherence. In the POP case, the top hat beam has uniform intensity and phase over the region. Since phase is constant, the wave front is perpendicular to the axis. A ray tracing analog to that would be a source that emits a collimated beam. In that case, the beam could be focused to a point. In the POP case you get an Airy disk due to diffraction. But in the extended source case, you get an image of the extended source, with a diameter determined by the system magnification.

Best,

David