Built-in FFT routines enable the user to transform the OPD distribution to give the Point Spread Function (far field intensity distribution), Modulation Transfer Function (MTF) and Strehl Ratio

 The MTF, calculated in the object plane of an imaging system, expresses the attenuation of spatial modulations in an image as a function of spatial frequency up to the limiting cut-off due to diffraction.

 MTF is a widely used tool in the design and measurement of optical imaging systems. By comparing, for example, the frequency response in the horizontal and vertical directions, the effects of astigmatism on the imaging properties of the system can be determined.

The PSF, calculated in the focal plane of an imaging system is useful in determining the effective spot size created by the imaging system..

The Strehl Ratio gives a measure of the peak intensity in the focal plane compared with the diffraction limited case.