Unformatted text preview: Barrett – CS450 Winter 2011 Lecture 19 Filters 1. Low-Pass Filters • What is the simplest kind of low-pass filter? Give the weights for one. • What effect does applying two box filters in succession (i.e. cascading) have? How or why is this equivalent to a triangular filter? • Why does convolution in the space/time domain with sin(x)/x cause “ringing?” What does this tell us about using a sharp cutoff in the frequency domain? • Which smoothes a signal more? – a Gaussian filter or a Box filter o f the same dimension? Why? • Given a low-pass filter in the space/time domain, how can it be implemented in the frequency domain? 2. Band-Pass (Reject) Filters • Show how a band-pass filter could be derived from two Gaussians. • What are the trade-offs between blurring and noise in a band-pass filter? • How can a bandstop/band-reject filter be created from a bandpass filter in the space/time domain? In the frequency domain? • Why are these kind of filters sometimes called “mexican hat” filters? • How can two different gaussian functions (in the space/time or frequency domain) be used to create band these filters? • How can two different gaussian functions (in the space/time or frequency domain) be used to create band these filters?...
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- Winter '08
- High-pass filter, Band-pass filter, Low-pass filter, Band-stop filter, Median Filters