摘要
A linear denoising filter is usually of lowpass type,and the main parameter in a lowpass filter is the cutoff frequency.The lowpass filters are normally shift invariant and can be implemented as convolution in the spatial domain or as multiplication in the Fourier domain.This paper presents a linear filter that is not characterized by its cutoff frequency but is characterized by the noise model.An example of such a linear filter is presented for lowdose X-ray computed tomography(CT).
