Barcode Scanner Composition

The system composition and structural principle of the barcode scanner are explained as follows: the main body of the scanning system is an optical structure, which should have the following two properties:
  1. It has a scanning optical path to produce a light spot, which can move linearly along a certain track under manual or automatic control and pass through the left blank area, start character, data character, terminator, and Right blank space.
  2. There is a receiving system for the reflected light of the bar code symbol, which should be able and good at receiving the diffuse reflection light reflected from the bar code symbol by the scanning light spot.The barcode scanning system can adopt different light sources, scanning forms, and optical path designs to achieve the above functions.
1) The light source of the scanner
There are many types of light sources used by barcode scanners, mainly semiconductor light sources, laser light sources, and incandescent lamps, flash lamps, and other light sources. Here we mainly introduce semiconductor light-emitting tubes and lasers.
①Semiconductor LED
  A semiconductor light-emitting tube, also known as a light-emitting diode, is actually a diode composed of a P-type semiconductor and an N-type semiconductor. Light-emitting diodes just emit light when applying forward voltage on the PN junction.
②Laser
The development of laser technology has a history of more than 30 years, and it is now widely used in various fields. There are many types of lasers. Early barcode scanners generally used helium-neon lasers as scanning light sources. In the 1980s, semiconductor lasers developed rapidly because of their low power consumption, small size, low operating voltage, high reliability, and low price. These characteristics make the original helium-neon lasers quickly replaced.
Our common semiconductor lasers are all low-power and as large as an ordinary triodes, so semiconductor lasers are also called laser diodes. Because barcode scanner generally uses laser diodes, their volume and cost are greatly reduced. In the beginning, only laser diodes that could only emit infrared lasers appeared. After the 1990s, red laser diodes appeared (now there are blue laser diodes. ), the development of laser diodes has become an important aspect of the development of barcode technology in recent years. (Source Cloud Collaborative Intelligent Manufacturing)
Compared with other light sources, the laser has unique properties:
  1. It has strong directionality.
  2. Excellent monochromaticity and coherence. No matter what kind of filtering technology is used for other light sources, the monochromatic light emitted by lasers cannot be obtained.
  3. High light intensity can be obtained. The barcode scanning system uses low-power laser diodes so that they will not cause damage to human eyes when they are shot into the human eyes for a short time, but it still has an illuminance that is difficult to achieve with other light sources.