The rapid development of computer technology has gradually digitized our lives, and barcode scanners have gradually entered our lives and integrated into our work. It has become an important medium for us to connect more closely with digital information. Before choosing to use a barcode scanner, let’s get to know the barcode scanner first. As a high-tech product closely integrated with optics, machinery, electronics, software applications and other technologies, barcode scanners are the third generation of major computer input devices after keyboards and mice. Since the birth of scanning guns in the 1980s, they have developed rapidly and been widely used. From the most direct pictures, photos, films to various drawings, graphics and manuscript materials, they can be input into the computer with scanning guns, and then these images can be scanned. The processing, management, use, storage or output of information.
Barcode scanner interface
The commonly used interface types of scanners generally include SCSI, EPP, and USB:
(1) SCSI (Small Computer Standard Interface): The maximum number of devices connected to this interface is 8, and the maximum transmission speed is usually 40M/S, which is relatively fast and generally connects high-speed devices. The installation of SCSI devices is more complicated, and an additional SCSI card is usually added to the PC, which is prone to hardware conflicts, but the functions are powerful.
(2) EPP (Enhanced Parallel Interface): An enhanced bidirectional parallel transmission interface with a maximum transmission speed of 1.5Mbps. The advantage is that there is no need to use other cards in the PC, the number of connections is unlimited (as long as you have enough ports), and the installation and use of the device are easy. The disadvantage is that it is slower than SCSI. This interface is easy to install and use, and replaces the SCSI interface in low-end and low-end occasions that do not require high performance.
(3) USB (Universal Serial Bus Interface): Up to 127 peripherals can be connected. The current USB1.1 standard has a maximum transmission speed of 12Mbps, and there is an auxiliary channel for low-speed data transmission. In the future, if there is a USB2.0 standard scanner, the speed may be extended to 480M/s. With hot-swappable function, plug and play. Scanners with this interface have gradually become popular with the establishment and promotion of the USB standard pushed by Intel.
The internal structure and working principle of the barcode scanner
A common flat-panel scanner is generally composed of a light source, an optical lens, a scanning module, an analog-to-digital conversion circuit and a plastic casing. It uses photoelectric elements to convert the detected optical signal into an electrical signal, and then converts the electrical signal into a digital signal through an analog-to-digital converter and transmits it to a computer for processing. When scanning an image, the light source shines on the image, and the reflected light passes through the lens and converges on the scanning module. The scanning module converts the light signal into an analog digital signal, and at the same time indicates the grayness of that image. At this time, the analog-to-digital conversion circuit converts the analog voltage into a digital signal and sends it to the computer. The color is quantized with 8, 10, and 12 bits of RGB three colors, and the signal is processed into the image output of the above-mentioned bits. If there is a higher number of quantization bits, it means that the image can have richer levels and depths, but the color range has exceeded the recognition ability of the human eye, so within the recognizable range, for us, a higher-bit scanner The scanned effect is that the color connection is smooth, and more picture details can be seen.
The resolution of the scanner
The resolution of the barcode scanner should be determined from three aspects: the optical part, the hardware part and the software part. That is to say, the resolution of the barcode scanner is equal to the resolution of its optical components plus the resolution obtained by its own processing and analysis through hardware and software.
Optical resolution is the actual number of light points that the optical components of the scanner can capture per square inch. It refers to the physical resolution of the CCD (or other optoelectronic devices) of the scanner, and it is also the real resolution of the scanner. The value is the value obtained by dividing the pixel points that the photoelectric element can capture by the horizontal maximum scannable size of the scanner. For example, for a scanner with a resolution of 1200DPI, the resolution of its optical part usually only accounts for 400-600DPI. The resolution of the expanded part is jointly generated by hardware and software. This process is generated by analyzing the image through the computer and mathematically filling the blank part (this process is also called interpolation processing).
Optical scanning and output are one-to-one, what is scanned is what is output. After being processed by computer software and hardware, the output image will become more realistic and the resolution will be higher. Most of the scanner guns currently on the market have software and hardware expansion functions for resolution. Some scanner advertisements say 9600×9600DPI, which is only the maximum resolution obtained through software interpolation, not the real optical resolution of the scanner. So for barcode scanner, the resolution has optical resolution (or optical resolution) and maximum resolution. Of course, what we care about is optical resolution, which is hard work.
We say that the resolution of a certain scanner is as high as 4800DPI (this 4800DPI is the sum of optical resolution and software difference processing), which means that when the image is input by the scanner, it can capture 4800× 4800 pixels (Pixel). For a scanning area of 1 inch square, the size of the image generated after scanning with a resolution of 4800DPI is 4800Pixel×4800Pixel. When scanning an image, the higher the scanning resolution is set, the finer the effect of the generated image, the larger the generated image file, but the more interpolation components.
Optoelectronic devices for barcode scanner
At present, there are four main types of photosensitive devices used in scanners on the market: photomultiplier tubes, silicon oxide isolated CCDs, semiconductor isolated CCDs, and contact photosensitive devices (ie, CIS or LIDE).
The mainstream is two kinds of CCD. The principle is simply: thousands to tens of thousands of phototransistors are integrated on a silicon single crystal. Scan in color. Comparing the two CCDs, the silicon oxide isolation CCD is better than the semiconductor isolation CCD. Friends who are familiar with physics will naturally know the reason. To put it simply, the leakage between the semiconductor CCD triodes will affect the scanning accuracy. Isolation with insulating silicon oxide will greatly reduce the leakage. Of course, it is best to add temperature control, because both semiconductors and conductors are generally sensitive to temperature. Sensitive, the conductivity will generally increase when the temperature rises. Most of the current mainstream markets are for semiconductor isolation CCDs, and there are relatively few silicon oxide isolation CCDs, obviously because of the higher cost. If you want to understand the effect of a scanner, it is very important to know what quality photoelectric components are used in the scanner, even if the same semiconductor isolation quality is different.
Contact photosensitive device, the photosensitive material it uses is generally cadmium sulfide that we use to make photoresistors, and the production cost should be much lower than that of CCD. The scanning distance is short, the scanning resolution is low or even sometimes cannot reach the nominal value, and the temperature change is easy to affect the scanning accuracy. These are the fatal problems of this kind of scanner.
Photomultiplier tube, the photosensitive material is mainly the oxide of metal cesium. Its scanning accuracy, even the degree of influence by temperature and noise are the best, but the price is also the most expensive. Considering the production cost and the possibility of customers choosing to use it, we will eventually abandon it.
The optoelectronic device of a scanning gun is an important factor in determining its performance, and others such as control circuits and software are also very important. But we often only understand a very limited part of it. So when we want to judge the performance of a scanning gun, we can only rely on actual operation and evaluation software for further understanding.