Hi,
There are two analysis output of one imaging design below. My question is that how can be FFT MTF values so higher during the RMS and geometric spot size radius are high.
Best answer by Mike.Jones
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RMS spot diagram and FFT MTF mismatch
Userlevel 5
+3
What is your wavelength weighting? Spot diagrams are geometric, not diffraction-based, and aren't a good measure of system performance when comparing them to diffraction-based analysis like MTF and EE. You appear to have high SA for rays near the pupul rim, and that can make spots appear much larger. Post up a ray fan plot. I'm guessing it will show relatively low ray spreading across most of the aperture, then large whiptails near the pupil rim. The ray aberrations would be larger, but there's not much energy out there. Trust diffraction MTF and EE more than spots.
Userlevel 7
+3
For an imaging system with significant aberration, you are probably better off using the Geometric MTF. It’s faster and doesn’t require excessive sampling like the FFT version.
Regards,
Jeff
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