What is a bar code scanner?

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Principles of bar code reading

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  1. A bar code consists of white and black bars. Data retrieval is achieved when bar code scanners shine a light at a bar code, capture the reflected light and replace the black and white bars with binary digital signals.
  2. Reflections are strong in white areas and weak in black areas. A sensor receives reflections to obtain analog waveforms.
  3. The analog signal is converted into a digital signal via an A/D converter. (Binarization)
  4. Data retrieval is achieved when a code system is determined from the digital signal obtained. (Decoding process)
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Types of bar code scanners

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CCD method

This method uses a semiconductor device called CCD(Charge Coupled Device), which converts light signals into electric signals

The CCD method bar code scanner has a built-in light. A scanner shines this light at a bar code and its reflection is captured via CCD for reading.

A bar code is captured once, allowing fast reading. There are no movable parts and impact resistance is excellent.

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Laser method

Laser light is shone on the label surface and its reflection is captured by a sensor (laser photo detector) to read a bar code. A laser beam is reflected off a mirror and swept left and right to read a bar code.

Using laser allows reading of distant and wide bar code labels.

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Pen method

This method only has a LED light source and a sensor to capture its reflection. Since a person moves a scanner to read a bar code, practice is required for operation.

The mechanism is simple, making this method inexpensive.