An intuitive discussion on the ideal ramp filter in computed tomography (I)

In X-ray computed tomography (CT), the ideal ramp filter is a generalized function defined by the inverse Fourier transform. Similar to Dirac's discussion on the delta function, we present an intuitive discussion on the ideal ramp filter. With this concise discussion, one obtains a better understanding of the filter backprojection algorithm (FBP) and can easily construct new practical filters.