Hello,

I have a system with a non-circular aperture and therefore try to calculate its effective f number using the operand EFNO(effective f number). However, I get different results when using the operand EFNO, in comparison to the result given in the relative illumination analysis, despite the same setting is applied on both calculation.

(wavelength 3 is 0.555µm, and field 1 corresponds to 0 y field)

As can be seen above, one gives a value of 4.13(EFNO), while the other gives a value of 3.85. I think the latter one should be correct, but the question is why does one get different results here, do these two use different algorithms for calculation? How can I calculate this value in a Zemax macro conveniently if the result provided by EFNO is not trustworthy….

Thanks a lot in advance!