How much do you know about barcode scanners?

Tue Jun 14 15:06:46 CST 2022

Barcode scanner
Barcode scanner, also known as barcode reader, barcode scanner, barcode scanner, barcode scanner, and barcode reader. It is a reading device used to read the information contained in the bar code. It uses optical principles to decode the content of the bar code and transmit it to a computer or other device through a data line or wirelessly. It is widely used in supermarkets, logistics express, libraries, etc. to scan barcodes of commodities and documents.

Four laser technologies
Ordinary barcode readers usually use the following four technologies: light pen, CCD, laser, image-based red light.

working principle
The light pen is the first hand-held touch bar code reader to appear, and it is also the most economical bar code reader.
When using, the operator needs to touch the light pen to the bar code surface, and a small light spot is emitted through the lens of the light pen. When the light spot is swiped across the bar code from left to right, the light is reflected in the "empty" part. "The light will be absorbed, so a changing voltage is generated inside the light pen. This voltage is amplified and reshaped for decoding.
AdvantageReading in contact with the barcode can clarify which one is the barcode to be read; the length of the barcode to be read can be unlimited; the cost is lower compared with other readers; there are no moving parts inside, and it is firm; small in size and light in weight. Disadvantages: The use of light pens is subject to various restrictions. For example, it is not suitable for reading bar codes in some situations; in addition, the light pen can only play its role when reading bar codes with a specified density and good print quality on a relatively flat surface; and Operators need to go through certain training before it can be used. For example, reading speed, reading angle, and improper use of pressure will affect its reading performance; finally, because it must be contacted for reading, when the barcode is damaged due to improper storage, or there is a When the protective film is layered, the light pen cannot be used; the first reading success rate of the light pen is low and the bit error rate is high.

Reader principle
CCD is an electronic coupling device (Chargcoupledevice), which is more suitable for close-range and contact reading. Its price is not as expensive as a laser reader, and there are no moving parts inside.
The CCD reader uses one or more LEDs, the light emitted can cover the entire bar code, the image of the bar code is transmitted to a row of lights, sampled by each individual photodiode, and the adjacent detection result is "black" or " "White" distinguishes each bar or space to determine the character of the bar code. In other words, the CCD reader does not read each "bar" or "empty" carefully, but the entire part of the bar code and converts it into an electrical signal that can be decoded. .
Advantages: Compared with other readers, CCD readers are cheaper, but they also have a wide range of barcode reading density and are easy to use. It is lighter than a laser reader, and unlike a light pen, it can only be read by contact.

Disadvantages: The limitation of the CCD reader lies in its reading depth of field and reading width. It is difficult to read barcodes printed on curved surfaces (such as beverage cans); in some occasions that require long-distance reading, such as warehouses, it is also difficult to read. Not very suitable; CCD has poor drop-resistance performance, so the failure rate is high; when the bar code to be read is relatively wide, CCD is not a good choice, and the bar code with long information or low density can easily exceed the scan The reading range of the head makes the bar code unreadable; and in some bar code readers that use multiple LEDs, any LED failure will cause it to be unreadable; most CCD readers have a low first reading success rate and a high error rate .

Principle of Laser Gun
The laser scanner is relatively expensive among various scanners, but it can provide the highest functional indicators, so it is widely used in various industries.
The basic working principle of the laser scanner is: a handheld laser scanner emits a beam of light through a laser diode, which is irradiated on a rotating prism or a mirror that swings back and forth. The reflected light passes through the reading window and illuminates the bar code surface. After the reflection of the bars or spaces, it returns to the reader, which is collected and focused by a mirror, and converted into an electrical signal by a photoelectric converter. The signal will be decoded by the decoding software on the scanner or terminal.
There are two types of laser scanners: handheld and fixed: the handheld laser gun is convenient and simple to connect and flexible in use. The fixed laser scanner is suitable for reading the largest and smaller barcodes, effectively freeing both hands to work.
Advantages: Laser scanners can be used for non-contact scanning very well. Under normal circumstances, laser readers are the only choice when the reading distance exceeds 30cm; laser reading barcodes have a wide range of density and can read irregular barcode surfaces or transparent Reading over glass or transparent adhesive paper, because it is non-contact reading, it will not damage the barcode label; because of the more advanced reading and decoding system, the first reading recognition success rate is high, the recognition speed is faster than the light pen and CCD, and the printing quality Bad or fuzzy bar code recognition effect is good; the bit error rate is extremely low (only about one in three million); the laser reader has good shock and drop resistance, such as: SymbolLS4000 series scanner, which can be 1.5 meters on cement floor Drop resistant.
Disadvantages: The only disadvantage of the laser scanner is its relatively high price, but if calculated from the sum of the purchase cost and the use cost, it is not much different from the CCD reader.

Image type red light
The image type red light bar code reader is a bar code reader that can replace the laser gun. Its scanning depth of field reaches 30cm, and with its scanning speed of up to 300 times/sec, it has excellent code reading performance. The unique image-based design of the image-based red light bar code reader has good decoding capabilities, and barcodes that cannot be read by ordinary scanners can be easily read. Through the intelligent interface, the keyboard, RS232 serial port, USB and other interfaces can be converted only by replacing the cable. At the same time, it can also be directly connected to a laptop computer. For special devices such as handheld computers, some models can be directly powered by the built-in battery, which solves the inadequate power supply capacity of the handheld computer. It can also be set up and software upgraded through software. Its rich data editing functions enable the image-based red light scanner to fully cooperate with the user's existing software. The price of image-type red light scanners is also reasonable, so it is widely used.