NSC and Physical Optics Propagation

  • 15 July 2020
  • 2 replies


I'm trying to simulate a system that focuses a beam with lenses after it reflects off of a DMD. I have made a rudimentary model of a DMD using NSC, but if I try to use POP I get an error message saying that the entrance pupil can't be located. I noticed that most of the posts that come up about POP show setups that are purely sequential. This might be a naive question, but is it not possible to use POP when you have non-sequential components in your system? Or is it because I have my entire system in non-sequential mode, so it doesn't take any of the lenses to be the entrance pupil?

Using the regular ray tracing method in non-sequential mode doesn't show any of the expected diffraction from the mirrors, and I don't observe a Fourier transform where I would expect.

Thanks for your help!



Best answer by Mark.Nicholson 15 July 2020, 22:04

View original

2 replies

Userlevel 7
Badge +3

Hey Katya,

If you're using hybrid mode NSC, make sure the stop is before the NSC group and use an 'object-specific' aperture definition like entrance pupil diameter or float-by-stop. You'll probably also need to use a plane phase reference and have pretty high sampling. Check out the sample file Documents\Zemax\Samples\Physical Optics\Lenslet Array.ZMX for an example of a similar system.


There's a little-known capability in Non-sequential that might do what you need better. Check out the sample file Samples\Non-sequential\Coherence Interference and Diffraction\Interference Example 4- Diffraction Limited Imaging.ZMX. Note the use of the Huygens Mode flag on detector object 6. This adds the rays landing on the detector as a coherent sum of plane waves to give the production of a full PSF rather than a geometric point image:

This may be the easier way of getting what you want. I recommend raeding the documentation on the Huygens Mode of the detector 😎

Userlevel 7
Badge +3

Quick follow up, check out for a full discussion of the POP and lenslet approach. The same thing should work for POP and DMD.