
Much to our good fortune, the OTF is the Fourier transform of the point
spread function (psf ), which is discussed in Chapter 2. Thus having either of
these functions makes available the other, and either one is sufficient to specify
the resolution of the system or of one of its components. Here we are making the
assumption that the imaging components under consideration can be modeled
as shift-invariant linear systems [1, 2].
While the OTF and, equivalently, the psf are complete specifications of the
system’s imaging capability, they are curves, and it is often desirable to have
a single number as a specification of resolution. Several of these are