Scan

A scan is the operation of reading a QR code with a camera or an area imager and restoring the stored data. Everything in using QR codes begins with a scan. When you point a smartphone camera at a QR code, an image-processing algorithm detects the finder patterns (the squares in three corners), identifies the code area, and decodes the module pattern. This series of processes is normally completed within 0.1 seconds.

There are four factors that determine the scan success rate. First, contrast. Black modules on a white background are the easiest to read, and a colored QR code fails to scan when its contrast ratio drops. Second, distance. An appropriate scanning distance is 3-10 times the length of one side of the QR code. Third, the quiet zone. Without a margin of at least 4 modules around the QR code, the boundary between the background and the code cannot be recognized. Fourth, print quality. Ink bleeding, folds in the paper, and reflections on glossy surfaces all reduce scanning accuracy.

In business use, there are situations where scanning happens several hundred times or more a day (logistics warehouses, event admission control, and so on), and the time per scan is directly linked to operational efficiency. In such situations, a dedicated barcode reader can scan faster and more stably than a smartphone. Dedicated readers are equipped with an area imager that captures the whole surface at once, and they are designed to be less affected by lighting conditions.