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bar code scanner - technical definition
A device specialized for reading bar codes and converting them into either the ASCII or EBCDIC digital character code. Pen scanners, also known as wand scanners, were the first type of bar code scanner developed in the 1970s. In order to be read, the tip of the pen must physically touch the bar code. Later, laser scanners allowed the bar code to be read at a slight distance from the head of the device, enabling supermarkets to read round cans and flexible packages more easily. The most common of that type today is the visible laser diode (VLD) scanner, which emits as many as 50 laser beams simultaneously to capture the image at any angle. See bar code and point of sale.
Laser Diode Mechanism
A laser diode (1) emits a beam (red) onto a combination of rotating (2) and fixed mirrors (3) that shine multiple beams onto the bar code (4). Although as many as 50 beams may hit the package at different angles, only one is shown in this illustration. The reflected light (yellow) is captured by the collector (5) and aimed at a sensor (6).
The Reflection
The black bars absorb light, while the white bars reflect it. Photo diodes turn the reflected light into an electrical signal, which is converted into digital pulses.
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