Non-contact scanners can read barcodes from a distance. General purpose laser scanners can read barcodes from a distance of 4 inches to 18 inches away. High performance scanners can read barcodes from 7 inches to a distance of 20 feet. A barcode is a message that holds information. The structure of the barcode consists of the height and the width.
Information is encoded into spaces and bars of various width.
The height of the barcode does not hold any information. Using the height, however, you can enlarge a barcode for easy scanning or for better visibility. The number of characters are represented in a linear inch called the barcode density. The density depends on the symbology. For example, using Code 39, 9.4 characters can fit in one inch.