Unless you absolutely need to use non-sequential mode, I would recommend using sequential mode and Physical Optics Propagation (POP) for modeling a spatial filter (this is actually one of the only 3 times when you absolutely need to use POP because geometric rays cannot model this case).  You should use POP for the following 3 scenarios:

• Modeling a spatial filter where you’re trying to remove higher order Hermite-Gaussian or Laguerre Gaussian modes
• Modeling the Gibbs phenomenon of near field “ringing” at a hard aperture
• “Free space diffraction” of propagating a beam from inside the Rayleigh range to outside the Rayleigh range

POP is useful for many other systems but these 3 areas have to use POP to get accurate results.  There are 3 really good Knowledgebase Articles that discuss how to use POP:

Using Physical Optics Propagation (POP), Part 1: Inspecting the beams – Knowledgebase

Using Physical Optics Propagation (POP), Part 2: Inspecting the beam intensities – Knowledgebase

Using Physical Optics Propagation (POP), Part 3: Inspecting the beam phases – Knowledgebase

That makes sense for the analysis portion. Is there an easy way to model to conical pinhole in sequential mode? I am looking to model something like this:

My initial thought was to use a lot of apertures spaced closely together but was wondering if there is an easier solution. Thanks for your reply!