Whenever we scan a QR code (Quick Response Code) using a scanner or a smartphone, our eyes are immediately drawn to the large square boxes located in its corners. Have you ever wondered why these boxes are present in only three corners instead of all four?
What Are They Called?
In technical terms, these large square boxes are known as "Finder Patterns" (or positioning markers). Their primary job is to tell the scanner where the QR code begins and what its correct orientation is.
Key Reasons for Having Only Three Corners:
- Determining Orientation and Alignment: When you scan a QR code, you don’t always hold your phone straight. You might scan it tilted, upside down, or from an awkward angle. Because these patterns are in three corners, the scanner instantly understands which part of the code is up, down, left, or right. This asymmetrical triangular arrangement allows the scanner to read the data correctly from any angle.
- The Problem with All Four Corners (The Symmetry Problem):
If these large boxes were placed in all four corners, the QR code would become completely symmetrical. In that case, the scanner would get confused about which way is up and which way is down. Without a directional reference point, the scanner wouldn't be able to
decode the data accurately. - Perspective and Scale (Distance Detection): In geometry, three points define a plane and perspective on a 2D surface. By locating the three finder patterns, the scanner can easily calculate the distance of the QR code and the angle from which it is being viewed, correcting any distortion caused by a slanted camera angle.
Conclusion
So, the next time you scan a QR code for a payment or open a restaurant menu, you'll know that those three square boxes aren't just for decoration—they are a smart navigation map that helps scanners read the code in a fraction of a second from virtually any angle!
