十万个为什么·科学启蒙30篇（4）

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为什么二维码能容错一部分污损

QR codes use Reed–Solomon error correction, which adds extra data to reconstruct missing parts.
They divide information into modules and encode redundancy so damaged sections can be guessed accurately.
Four levels of error correction exist: L (7%), M (15%), Q (25%), and H (30%)—higher levels mean more resilience.
A scuffed corner or coffee stain may remove up to 30% of modules without breaking the code’s readability.
Scanners detect alignment patterns and timing grids first, then decode the message using mathematical recovery rules.
This built-in redundancy lets QR codes work even when printed on curved or worn surfaces like packaging or posters.
Unlike barcodes, which store data linearly, QR codes hold information in two dimensions—making them far more robust.
Designers choose error level based on expected use: high-risk environments need H-level protection.