Computer Vision Foundations · free preview

Delta Trains and Spectrum Replication

Modeling sampling as multiplication by a delta train shows the sampled spectrum as infinitely many shifted copies of the original, and aliasing as their overlap.

1. Sampling as multiplication

Sampling as multiplication

2. A train transforms to a train

A train transforms to a train

3. The spectrum becomes its own wallpaper

The spectrum becomes its own wallpaper

4. What the model buys

What the model buys

5. Why a train becomes a train

The Fourier transform of the delta train is another delta train with spacing 2π/Ts. What is the underlying principle?

6. Aliasing as geometry

In the replicated spectrum, what precisely is aliasing, and what does reducing Ts do to it?

7. Replica spacing

Sampling uses period Ts=1/4T_s = 1/4. Write the spacing 2π/Ts2\pi/T_s of the spectral copies.

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