I’ve been performing some tests on a series of f=25mm Petzval objectives using a double-pass interferometer and taking the Zernike data I get from that and putting it in Zemax. I’m hoping to get an MTF to compare to the theoretical MTF from the surface data of the system used to design it. This requires me to use afocal mode to get my measurements. The Interferometer has a focal length of 1066.8 mm and a wavelength of 632.8 nm. In this, I model the Petzval system as a single mirror and put the Zernike data in that. The issue is that since I use afocal mode for my analysis, the MTF is in cy/mr but I’m not sure how to convert this to cy/mm to compare to the theoretical data, or cy/mr from the surface diagram. Thank you for your help.
 

Surface data and FFT MTF from interferometer

FFT MTF from theoretical surface data in cy/mm

FFT MTF from theoretical surface data in cy/mr