You must have come across a barcode scanner in a retail store or a library that you visited. This story includes information regarding its working and its types.
A barcode scanner is a device that reads the barcode and converts it into numbers and letters. It is connected to a computer, that stores the numbers and letters that are decoded, using a cable via the serial port or the keyboard wedge. A decoder circuitry is present that is used to decode the image with the help of a sensor.
A barcode is a set of vertical lines and spaces, differentiated based on their width and space. It includes a start bit, stop bit, and sometimes checksum bit that checks code accuracy.
A barcode scanner consists of a laser source and a photo sensor. It decodes the code into electrical signals, and passes them on to the computer. The computer must have a software installed in it, which helps to convert the electrical signals to numbers and letters.
Types
Pen-type
The pen-type scanners are pen-shaped and have a light source and a photo diode at the tip. The light falls on the barcode and the photo diode converts the reflected light of varying intensity in a waveform. This waveform is fed to the computer via the cable.
The software converts the waveform to related data. The pen-type readers are available in different resolutions, so as to read codes of different shapes and sizes. It is less expensive and is easy to maintain.
Laser
The laser scanner has working similar to that of a pen-type scanner, but its components are different. These use laser beams as a source of light, and reciprocating mirror or rotating prism, for detecting the reflected light.
The frequency of a light source used in both is the same and the light detecting devices, like the photo diode and prisms, are also tuned to the same frequency.
CCD
CCD stands for charge-coupled device. It consists of an array of tiny sensors placed at the tip. The tiny sensors generate a voltage waveform and they are sequentially collected and given to the computer for conversion.
The basic difference between the pen-type and laser scanners is that, the pen-type measures the reflected light of a specific frequency, whereas the laser type measures the emitted ambient light from the barcode.
Camera-Based
Advanced digital image processing techniques are used for decoding the barcode. It contains a small digital camera, that directly captures the image of the code.
Portable data terminals are also available. These contain a Liquid Crystal Display (LCD). This portable terminal is in the shape of the palm and has an integrated scanner and a computing unit inside it.
Some factors that must be considered while buying a barcode scanner are as follows:
Environmental conditions (harsh or mild)
Need of a real-time system
Distance between the scanner and the barcode
Requirement of hands-free or hand-held scanning
Need of continuous or periodic scanning
They are widely used in many stores, industries and libraries for access control and automatic identification purposes.