You can freely build on How the QR Code Works
This patent expired in 2015. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Toyota Central R&D Labs Inc
Patent granted
1998
Expired
2015
Forward citations
250
What this patent covers
The patent describes a square two-dimensional barcode containing data cells and three specific positioning symbols at its corners. These positioning symbols consist of concentric black and white squares. When a scanner draws a line through the center of any of these symbols at any angle, it always detects a specific pattern of dark and light widths in a 1:1:3:1:1 ratio. The scanner uses this unique ratio to locate the boundaries and rotational angle of the code. It then uses alternating light and dark timing cells to align its reading grid and decode the data stored in the remaining cells.
What is now free to use
All 0 claims of US 5726435 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover standard one-dimensional barcodes that only store data along a single horizontal axis.
Does not cover two-dimensional codes that use circular or hexagonal grid layouts instead of a square matrix.
Does not cover codes that rely on color variations rather than binary dark and light cells to store data.
Does not cover codes that lack the specific 1:1:3:1:1 ratio positioning symbols at three corners.
Who is building on this today
Denso Wave, the original developer and a subsidiary of Toyota, remains a key player in industrial scanning. Virtually every modern smartphone manufacturer, including Apple and Samsung, builds native QR code scanning directly into their camera software.
Products built on expired version of this technology
QR codes on restaurant tables for digital menus
Boarding passes and concert tickets scanned at gates
Mobile payment codes in apps like WeChat Pay and Venmo
Inventory tracking labels on automotive parts
How to cite this patent in your documentation
Toyota Central R&D Labs Inc. US Patent 5726435. Optically readable two-dimensional code and method and apparatus using the same. Granted 1998, expired 2015. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.