Moiré Patterns

Aliasing you can see

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Moiré patterns are spatial aliasing: fine detail masquerading as coarse bands.
• A pattern of f cycles per pixel looks like |f − k|; only f ≤ ½ is faithful.
• Overlapping gratings make bands at the difference frequency.

Steps

1. Ghostly stripes
2. A fine grating
3. Fooling the pixels
4. Dress code
5. Resolving power
6. Two screens