Barcode scanners: technology and types

In short: A barcode scanner measures which parts of a code are light and dark and translates the pattern into characters. There are laser, CCD/LED, camera (imager) and phone scanners.

In more detail: The principle: white reflects light, black absorbs it. The scanner turns the sequence of brightness values into an electrical signal, measures the widths of bars and spaces and compares them with the table of the code type. The check digit confirms the result.

In detail

• Laser scanner: a beam is steered across the code by a mirror. Good range, 1D only.
• CCD/LED: a row of light sensors, no moving parts, robust, short distance.
• Imager (camera scanner): an image is analysed. Can read 1D and 2D (QR, Data Matrix), also from a screen.
• Phone: the camera plus software (e.g. ZXing, native camera API, BarcodeDetector in the browser).
• Connection: USB as a keyboard (HID): the scanner “types” the code and presses Enter. Also Bluetooth, serial interface.
• Settings: prefix/suffix, keyboard layout, which code types are active (with programming barcodes from the manual).
• Sources of error: reflection, scratches, code too small, too little contrast, missing quiet zone.
• In the browser: camera scan via WebRTC and a decoder library, which is how the inventory tool on this site works.

See also: Barcode scanner, Barcode types at a glance