OVERVIEW OF BARCODE READERS
Barcode readers are hardware devices designed to read barcode labels and interpret the symbols in such labels. After the reading, these devices can store the information in their internal memory or send it to a centralized system server. When the barcode labels first hit the markets several decades ago, the first barcode readers also appeared and they have evolved quite much since then, although the main operating principles of the equipments are pretty much the same even today, with some minor adjustments. They generally use some sort of light source which moves across the barcodes. The devices measure the intensity of the light reflected back and transform the output into readable codes. The bars are black and white because black absorbs light and white reflects it, forming the pattern that is going to be interpreted by the barcode readers. The first models where designed to resemble a pen. Reading a barcode with such items was very difficult because of their instability. Later the same barcode readers were redesigned in order to reduce mistakes in lectures provoked by human interaction. With pen readers, the users needed to be very precise to read a barcode on the first attempt, with posterior models, the light source was attached to a fixed element and was the label the one that moved under the light. Unfortunately, this procedure limited the applications for the readers, which needed to be mobile. This is how the first laser barcode readers appeared in the market. They didn’t need to project the light source vertically over the code. It was enough for the laser beam to cover the entire surface of the barcode label to provide a very precise lecture. Mistakes were instantly reduced. Nevertheless, retail stores needed even more sophisticated methods for reading the labels. And this is how omni-directional barcode scanners appeared in the market and they are used today in the shopping centres.