How the Barcode Scanner works?

Basically, Barcode scanner consist of a light source, a photo-diode and a simple decoder to decode the waveform generated by photo-diode which will be described later in this post.

Currently, there are four different types of Barcode scanner available in the market. They are Pen Type Readers, Laser Scanners, CCD readers, and camera-based readers.

Pen Type Reader

Pen Type Readers

Pen Type Readers mainly consist of a photo diode and a light source which are placed next to each other in the tip of a pin. To read a barcode, generally you drag the tip of the pen from left to right in a steady even motion. The photo diode measures the intensity of light reflected back from a light source and thus generates a waveform that measures the widths of the bar and spaces in the barcode. Dark bars 

Laser Scanner

in the barcode absorbs light while white space reflect the light back to a photo diode forming the voltage waveform.

Laser Scanners

Laser scanners work in the same way as the Pen type readers works. The only difference between them is Laser scanners use laser beam as the light source and a rotating prism to scan the laser beam back and forth across a barcode.

In both pen type readers and laser scanners, the light emitted by the readers is tuned to a specific frequency and the photo diode is thus designed to catch only this specific frequency light.

DataMan 500 Camera Based Readers

CCD Readers

CCD(Charge Couple Device) readers contains hundreds of tiny light sensors which are lined up in the head of the reader. Each sensor can be treated as single photo diode which measures the intensity of the light immediately in front of it. Each individual light sensor is extremely small. Because of hundreds of tiny light sensors lined up in a row, voltage waveform is generated by measuring the voltage across each tiny sensors in the row. Difference between CCD readers and above ones is that CCD reader catches the ambient light from the barcode while pen type and laser scanners catches only the specific frequency light from the barcode.

Camera Based Readers

The Camera Based Readers consist of a camera which captures the barcode image. The reader then uses the digital processing techniques to decode the captured barcode image. Camera Based Readers uses the same technology as CCD readers use. The only difference between Camera Based Readers and Charge Couple Device(CCD) readers is that instead of using single row sensors, Camera Based Readers has a video camera which uses hundred of rows of sensors which are arranged in two-dimension so that it can generate the whole image at a time.