How do barcode scanners work?

ByJoe Horner 2019-06-20 3731

Barcode scanning has spread all over our daily life, widely used in supermarkets, logistics couriers, libraries and other scanning goods, documents of the barcode. Today, we focus on what is bar code and how barcode scanners work.

 barcode scanners

What is a barcode

barcode is a graphical identifier that arranges multiple black bars and white space with different widths according to certain coding rules to express a set of information. The common barcode is a parallel line pattern formed by black bars (referred to as strips for short) and white bars (abbreviated to blank) with different reflectivity.

Barcode can mark many information, such as producing country, manufacturer, trade name, production date, book classification number, starting and ending place, category, date and so on. Therefore, it has been widely used in many fields, such as commodity circulation, book management, postal management, banking system and so on.

Barcode type

There are two types of barcodes, linear and 2D.

The most visually powerful UPC (Universal Product Code) is a linear barcode consisting of two parts: a barcode and a 12-bit UPC number. The first six digits of the barcode are the manufacturer's identification numbers. The next five digits represent the project number. The last number, called the check bit, enables the scanner to determine whether the barcode is scanned correctly.


Linear barcodes usually contain any type of text information. In contrast, two-dimensional barcodes are more complex and can contain more information in the code: price, quantity, URL, or image. The linear barcode scanner cannot read the 2D barcode; an image scanner is required to read the information embedded in the 2D barcode. Popular QR code is a kind of two-dimensional barcode, which can store a lot of information compared with one-dimensional barcode.

2D barcode; 

What is a barcode scanner?


Barcode scanner, also known as barcode reader, barcode scanning gun, barcode scanner, barcode scanning gun and barcode reader. It is a reading device used to read the information contained in the barcode. Using the optical principle, the content of the barcode is decoded and transmitted to the computer or other equipment by data line or wireless way.


The structure of barcode scanner is usually divided into three parts: light source, receiving device, photoelectric conversion part, decoding circuit and computer interface.

working principle:

The scanning gun is that the light emitted by the light source irradiates the barcode symbol through the optical system. The reflected light is imaged on the photoelectric converter by the optical system and interpreted by the decoder as a digital signal that can be directly accepted by the computer.

barcode scanner 

4 techniques used in barcode Scanner

Common barcode readers usually use the following four technologies: light pen, CCD, laser, image red light.

Pen-type reader 

Pen-type reader principle:

Light pen is the first kind of hand-held contact barcode reader, it is also the most economical barcode reader.

When in use, the operator needs to contact the light pen to the barcode surface, through the light pen lens to emit a very small light point, when this light point from left to right across the barcode, in the "empty" part, the light is reflected, the "bar" part, the light will be absorbed, so in the light pen interior to produce a changing voltage, this voltage by amplifying, shaping for decoding.

CCD reader principle:

CCD is an electronic coupling device (Chargcoupledevice), is more suitable for close and contact reading, its price is not as expensive as laser readers, and there are no moving parts inside.

The CCD reader uses light from one or more LED, to cover the entire barcode, the image of the barcode is transmitted to a row of light, is sampled by each individual photodiode, and each bar or space is distinguished by the adjacent detection result as "black" or "white" to determine the character of the barcode. In other words, the CCD reader does not pay attention to reading each "bar" or "empty", but the entire part of the barcode. And converted into an electrical signal that can be decoded.

Laser scanner  

Laser scanner principle:

Laser scanners are relatively expensive among all kinds of scanners, but they can provide the highest functional indicators, so they are widely used in various industries.

The basic working principle of the laser scanner is that the hand-held laser scanner emits a beam of light through a laser diode, irradiates a rotating prism or a swinging mirror, and the reflected light shines through the reading window to the barcode surface. The light returns to the reader after a strip or empty reflection, which is collected and focused by a mirror and converted into an electrical signal by a photoelectric converter. The signal will be decoded by a scanner or decoding software on the terminal.

Laser scanner is divided into two forms: hand-held laser gun is convenient and simple to connect, flexible to use. Fixed laser scanner is suitable for reading the largest, barcode smaller occasions, effectively liberate the hands to work.

Image type red light: ​ 

Image type red light principle :

The image type red light barcode reader is a barcode reader which can replace the laser gun! Its scanning depth of field is up to 30 cm, combined with its scanning speed of up to 300 times per second, so that it has excellent code reading performance. Unique image design, so that its decoding ability is very strong, the general scanner can not read the barcode, and the image red light can still be easily read. Through the intelligent interface, only need to replace the cable to realize the keyboard, RS232 serial port, USB and other interface conversion, at the same time, can also be directly connected to the notebook computer.

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