About Barcode Scanners

About Barcode Scanners

Barcode scanners are electronic devices that were designed for printed barcodes. Just like a flatbed scanner, a barcode scanner has a light source and a light sensor that translates optical impulses into electric ones. In most cases, barcode scanners have a decoder circuitry that analyzes the barcode’s image data provided by the sensor and sending the barcode’s content to the scanner’s output port.

As far as the scanning methods are concerned, these are differentiated by the amount of the operator manipulation necessary:

• Semi-automatic handheld readers – the operator need not swipe but must at least put the reader near the label;

• Fix-mount readers – designed for automatic reading. The reading is done laterally passing the label over the reader. For this, no operator is required, however the position of the code target must coincide with the imagining capability of the reader;

• Pen type readers – the operator swipes the pen over the code;

• Reader gates for automatic scanning – for this, the position of the code must be just under the gate for a very short time thus enabling the scanner sweep to capture the code target properly.

There are different technologies used for barcode scanners, the most important ones are:

• Pen type readers – use a light source and a photodiode that are situated next to each other in the tip of a wand or pen. In order to read a bar code, the tip of the pen moves across the bars in a steady motion. The above mentioned photodiode is designed for measuring the intensity of the light reflected back from the light source and generates a waveform which is used for measuring the widths of the bars and spaces in the bar code.

• Laser scanners – they work just like the pen type readers with a single exception: they use a laser beam as the light source and usually employ either a rotating prism or a reciprocating mirror in order to scan the laser beam back and forth across the entire bar code. Just like in pen type readers, a laser scanner uses a photodiode for measuring the intensity of the light reflected back from the bar code.

• CCD readers – use an array of hundreds of small-sized sensors that are lined up forming a row in the reader’s head. Each of the sensors can be considered to be a single photodiode that is designed for measuring the intensity of the light immediately in front of it. The main difference between a CCD reader and laser scanners or pen type readers is that the CCD reader is measuring the emitted ambient light from the bar code in comparison with the other two which are measuring the reflected light from a specific frequency originating from the scanner itself.

• Camera-based scanners – are considered the newest type of bar code readers available on the market. They use a small-sized video camera for capturing an image from a bar code.

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