Question

In a filter, all the frequencies inside a circle of radius D0 are not attenuated while all frequencies outside circle are completely attenuated. The D0 is the specified nonnegative distance from origin of the Fourier transform. Which of the following filter(s) characterizes the same?

(a) Ideal filter

(b) Butterworth filter

(c) Gaussian filter

(d) All of the mentioned

This question was addressed to me in unit test.

Question is taken from Smoothing Frequency-Domain Filters topic in section Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

Correct answer is (a) Ideal filter

For explanation I would say: In ideal filter all the frequencies inside a circle of radius D0 are not attenuated while all frequencies outside the circle are completely attenuated.