We all know that barcode scanning is one of the most common products, such as supermarkets, express delivery and so on. Do you know the principle behind it? Today, Xiaobian will give you a brief introduction.

The role of laser diode in bar code scanning is actually "illuminator" and "the first step of information decoding". It is responsible for emitting a very thin and bright laser beam, so that the black and white stripes of the bar code can be clearly presented in front of the receiving system. Although this light is small, it has concentrated energy, strong directivity and high brightness, which is exactly what ordinary LED lamps can't do.

In fact, the principle is quite simple. When the light emitted by the laser diode irradiates the bar code, the black bar absorbs the light and the white bar reflects the light. The optical system in the scanner will send the reflected light to the photodetector, and then through the signal processing circuit, the light intensity changes will be converted into electrical signals, which will be analyzed by the decoding chip into numbers, letters or other coded information, so that the system can identify commodity numbers or logistics information.

The divergence angle of LED is large, and the light is scattered, which looks bright but the contrast is not high; The laser diode has concentrated light, strong directivity, high brightness and strong anti-interference ability, which means that it can accurately illuminate the bar code even in a complex light environment, reducing misreading and missing reading.

Technically, the laser diode used for bar code scanning is generally in the red band, that is, between 630nm and 670nm. The red light in this band is visible to human eyes, and it has good visual recognition effect, high brightness and strong focusing.

The scanning equipment makes the laser swing rapidly from left to right through mechanical vibrating mirror or MEMS micro mirror, forming a "scanning line", which is the red line we see when scanning the code.

When you put the barcode on the red line, the sound of "drip" means that the laser has scanned the complete barcode information.

The function of laser diode is not only "lighting", but also directly determines the scanning speed and accuracy.

For example, in the high-speed logistics sorting line, almost all bar code scanning equipment uses laser, because the laser has good directivity and fast response speed, and can still maintain the recognition accuracy when the object moves rapidly.

Moreover, the laser diode has long service life, low power consumption and small size, which is also very important for equipment manufacturers, and can make the whole machine lighter, smaller and more energy-saving. Another point that is easily overlooked is that the stability and consistency of laser diode have a great influence on the code scanning effect. Some cheap scanning guns use unstable laser sources, and after a period of use, the spot diverges and the power decays, and the recognition rate will drop obviously.

But like our commonly used imported laser diodes, such as the red light series of QSI in South Korea, the light spot is uniform, the power is stable, and the service life can reach tens of thousands of hours. Such components can run stably for a long time when placed in industrial code scanning equipment.