What is a Barcode Scanner?
With the popularity of barcodes and QR codes, barcode scanners are increasingly used in logistics, warehousing, manufacturing, retail, and other industries. Barcode scanners are usually also called bar code scanning readers, which are devices used to read the information contained in bar codes.
The structure of a barcode scanner usually consists of the following parts: light source, receiving device, photoelectric conversion component, decoding circuit, and computer interface. The followings are the basic principles and features of barcode scanners.
Basic working principle
The light emitted by the light source irradiates the bar code symbol through the optical system, and the reflected light is imaged on the photoelectric converter through the optical system to generate an electrical signal.
The signal is amplified by the circuit to generate an analog voltage, which is proportional to the light reflected on the bar code symbol, and then filtered and shaped to form a square wave signal corresponding to the analog signal, which is interpreted by the decoder as a digital signal that the computer can directly accept.
Ordinary barcode readers usually use the following three technologies
1. Light pen
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 in use, the operator needs to touch the light pen to the surface of the bar code and emit a small light spot through the lens of the light pen. When the light spot slides across the bar code from left to right, in the "empty" part, the light is reflected the "bar" part, and the light will be absorbed, so a changing voltage is generated inside the light pen, which is amplified and shaped to be used for decoding.
(1) When reading in contact with the bar code, it can be clear which bar code is being read.
(2) The length of the reading barcode can be unlimited.
(3) Compared with other readers, the cost is lower.
(4) There are no moving parts inside, so it is relatively strong.
(5) Small size and lightweight.
2. CCD reader
CCD is a charge-coupled device, 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 neighboring detection results are "black" or "white" to distinguish each "bar" or "empty" to determine the character of the barcode.
In other words, the CCD reader does not only read each "bar" or "empty", but the entire part of the bar code and convert it into an electrical signal that can be decoded.
Compared with other readers, CCD readers are cheaper, but they also have a wide range of barcode reading densities and are easy to use. It is lighter than a laser reader, and unlike a light pen, it can only be read by contact.
3. Laser scanner
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 hand-held laser scanner emits a beam of light through a laser diode, which hits a rotating prism or a mirror that swings back and forth, and the reflected light passes through the reading window and hits the bar code surface.
The light is reflected by the "bar" or "empty" and then returns to the reader. It is collected and focused by a mirror and converted into an electrical signal by a photoelectric converter. The signal will be decoded by the scanner or the decoding software on the terminal.
The laser scanner is divided into two forms: handheld and fixed: the handheld laser gun is convenient and simple to connect and flexible to use. The fixed laser scanner is suitable for occasions with small bar codes, which can effectively free both hands to work.
(1) The laser scanner can be used for non-contact scanning very well. Normally, when the reading distance exceeds 30cm, the laser reader is the only choice.
(2) The laser reading barcode has a wide range of densities, and it can read irregular barcode surfaces or through glass or transparent adhesive paper. Because it is non-contact reading, it will not damage the barcode label.
(3) Because of the more advanced reading and decoding system, the first-reading recognition success rate is high, the recognition speed is faster than light pen and CCD, and the recognition effect of poor printing quality or fuzzy barcode is good.
(4) The bit error rate is extremely low (only about one part in three million).
(5) The laser reader has good shock and drop resistance.
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