ZEMAX also supports comprehensive diffraction analysis capabilities.

Select the menu option, "File > Open" from the main menu bar and open the file "Samples > Sequential > Objectives > Cooke 40 degree field.zmx". This file contains data describing a simple triplet objective.

TIP:  You can also use the "Ope" button on the button bar to open a file.

To look at the MTF for this lens, select the menu option, "Analysis > MTF > FFT MTF" from the main menu bar or select the "MTF" button on the button bar. The tangential and sagittal response for each field point will be plotted versus spatial frequency using FFT (Fast Fourier Transform) techniques. MTF calculations based on Huygen's integral calculations are also available.

To show the diffraction limited MTF for this design, click on "Settings" from the FFT MTF window menu bar, then check the box that says "Show Diffraction Limit", then click "OK". The diffraction limit will be added to the plot.