Diffraction Enclosed Energy out of focus

Question

Dear Zemax Team,can Diffraction Enclosed Energy be used on any surface in the optical system, or only on the image plane or in a focus plane?I use Diffraction Enclosed Energy on IMA (focussed Airy pattern) and on a plane a few millimeters before IMA (here some other distribution). From geometric considerations, the spot size should be in IMA about 8um and about 150um in the other plane. This is also confirmed by Geometric Encircled Energy. However, Diffraction Enclosed Energy plots the same results for both planes (8um spot size).Maybe you can give me a hint on this?Many thanksMarkus

Jeff.Wilde · Accepted Answer

Take a look at the help documentation for Diffraction Encircled Energy, in particular, the section on evaluation at surfaces other than the image surface:

The diffraction encircled energy is not computed directly on the user-selected surface, but rather on the paraxial focal plane for this surface. In other words, the ray bundle passing through the user-selected surface is allowed to come to its best paraxial focus (which will be a virtual focus if the ray bundle is diverging). Then the diffraction encircled energy computation is carried out in that focal plane. However, for the geometric encircled energy, the analysis is performed directly on the user-selected surface.

Note that you can always just defocus your image plane and see the impact using Diffraction Encircled Energy. However, once you change the surface setting to anything other than the image plane, OpticStudio will automatically apply the paraxial refocus (for PSF, MTF and Diffraction Encircled Energy analyses).

Markus · Answer

Jeff, many thanks, this was very helpful!Markus

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