Test: Aliasing

Work in progress

This is a standalone test page for a demonstration under development. It is not yet part of a chapter.

Signals & Sampling

Aliasing: When Sensors Lie

derekmolloy.ie

1. The frozen propeller2. Samples and the Nyquist rule3. The motor that lied4. The price of seeingSandbox

The frozen propeller

Next: samples

A drone propeller spins at 5,400 rpm: 90 turns every second. Film it on a phone at 30 frames per second, and something strange happens.

Propeller speed5,370 rpm5,400 rpm5,430 rpm

What your eye seesa blur

What the camera records30 fps, frame 0

Actual speed

5,400 rpm

Turns per frame

3.000

The video shows

frozen in place

Pause

Tutor

Simulated: scripted replies driven by the live scene

Compare the two views. Your eye sees a blur. The camera sees something else entirely.