20 u00b0 and 70 u00b0 filtered mtfs extend only to the nyquist frequency of the 20 micron detector or 25 lp mm the best way to define what constitutes a transverse ray intercept curve which is a u201c substantially straight line u201d is to look at the mtfs over the entire useful range of the system with wavefront coding applied these curves must be very close to each other in order for the post processing to be able to move all the the mtfs to the desired performance level compare the mtfs of fig4 no wavefront coding to those of fig5 wavefront coding the fig5 mtf curves are very close together in fig6 post processing has moved the mtfs to an acceptable level more sophisticated post processing could improve the mtfs much further to nearly diffraction limited performance so long as the preprocessing curves are close enough together post processing could not accomplish this goal with the curves of fig4 because they are not at all close together 0102 fig1 also illustrates this concept the mtf curves without wavefront coding do not track each other the curves with wavefront coding are very close together thus the the curves with wavefront coding after post processing are very good finally in fig1 and 14 the mtf curves without wavefront coding are far apart but the.