How to judge the good or bad of the barcode scanner?

Guide: The scanner is a high-tech product that is closely integrated with optical, mechanical, electronic, software applications and other technologies. It is the third generation of major computer input devices after keyboard and mouse. Before choosing to use the scanner, Xiaobian will take you to know the scanner.

As a high-tech product closely integrated with optical, mechanical, electronic, and software applications, the scanner is the third generation of major computer input devices after keyboard and mouse. Since the birth of the scanner in the 1980s, it has been rapidly developed and widely used. From the most direct pictures, photos, film to various drawings and documents, documents can be input into the computer with a scanner to achieve these images. Processing, management, use, storage or output of information.

First, the scanner interface

There are three types of common interfaces for scanners: (1) SCSI (small computer standard interface): The maximum number of connected devices on this interface is eight, usually the maximum transmission speed is 40M/S, the speed is fast, and the connection speed is high. device of. The installation of SCSI devices is more complicated. Generally, a SCSI card is added to the PC, which is easy to generate hardware conflicts, but it is powerful. (2) EPP (Enhanced Parallel Interface): An enhanced bidirectional parallel transmission interface with a maximum transmission speed of 1.5 Mbps. The advantage is that there is no need to use other cards in the PC, unlimited number of connections (as long as you have enough ports), the device is easy to install and use. The downside is that the speed is slower than SCSI. This interface replaces the SCSI interface in the low-end and low-end performance requirements due to its ease of installation and use. (3) USB (Universal Serial Bus Interface): Up to 127 peripherals can be connected. The current USB1.1 standard has a maximum transmission speed of 12 Mbps and has a secondary channel for transmitting low-speed data. In the future, if there is a USB 2.0 standard scanner speed may be extended to 480M / s. With hot plug function, plug and play. The scanner of this interface has become popular with the establishment and promotion of the USB standard under the push of Intel.

Second, the internal structure and working principle of the scanner

Common flatbed scanners generally consist of a light source, an optical lens, a scanning module, an analog to digital conversion circuit, and a plastic housing. It uses the photoelectric element 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 for transmission to a computer for processing. When scanning an image, the light source illuminates the image and the reflected light passes through the lens to converge onto the scanning module. The scanning module converts the optical signal into an analog digital signal (ie, the voltage, which is the intensity of the received light). Related), also pointed out the degree of darkness of that image. At this time, the analog-to-digital conversion circuit converts the analog voltage into a digital signal and transmits it to the computer. The color is quantized by the 8, 10, and 12 bits of the RGB three colors, and the signal is processed into an image output of the above number of bits. If there is a higher number of quantization bits, it means that the image can have a richer level and depth, but the color range has exceeded the recognition ability of the human eye, so for us, the higher-order scanner for the range of resolution The effect of scanning is that the color is smooth and you can see more details.

Third, the resolution of the scanner

The resolution of the scanner is determined in three ways: the optical part, the hardware part, and the software part. That is to say, the resolution of the scanner is equal to the resolution of its optical components plus its own resolution obtained by processing analysis by hardware and software. The optical resolution is the actual number of spots that the optical component of the scanner can capture in an area per square inch. It refers to the physical resolution of the scanner CCD (or other optoelectronic device) and the true resolution of the scanner. The value is the value obtained by dividing the pixel point that the photoelectric element can capture by the maximum scanable size of the scanner. For example, a scanner with a resolution of 1200 DPI often has a resolution of only 400 to 600 DPI in its optical portion. The resolution of the extended part is jointly generated by hardware and software. This process is generated by computer analysis of the image and mathematical filling of the blank part (this process is also called interpolation processing).

The optical scan and output are one-to-one, what is scanned, and what is output. After processing by computer hardware and software, the output image will become more realistic and the resolution will be higher. Most of the scanners currently on the market have software and hardware extensions for resolution. Some scanners write 9600×9600 DPI, which is only the maximum resolution obtained by software interpolation, not the true optical resolution of the scanner. So for bar code scanners, the resolution has optical resolution (or optical resolution) and maximum resolution. Of course, we are concerned with optical resolution. This is hard work.

We say that the resolution of a scanner is as high as 4800 DPI. This 4800 DPI is the sum of optical resolution and software difference processing. It refers to the image that can be collected on a 1 square inch scanning surface when the image is input by a scanner. Pixel. The 1 inch square scan area, scanned at a resolution of 4800 DPI, produces an image size of 4800 Pixel x 4800 Pixel. When scanning an image, the higher the scanning resolution is set, the finer the effect of the generated image, and the larger the generated image file, but the more the interpolation components.

Fourth, the photoelectric device of the scanner

There are currently four types of photosensitive devices used in scanning guns on the market: photomultiplier tubes, silicon oxide isolated CCDs, semiconductor isolated CCDs, and contact sensitive devices (CIS or LIDE).

The mainstream is two types of CCDs. The principle is simple: it integrates thousands to tens of thousands of phototransistors on a single silicon single crystal. These phototransistors are divided into three columns, which are respectively covered with red, green and blue color filters. Color scanning. Compared with the two CCDs, the silicon oxide isolation CCD is better than the semiconductor isolation CCD, and friends familiar with physics naturally know the reason. Simply speaking, the semiconductor CCD triode leakage phenomenon will affect the scanning accuracy. The isolation with silicon oxide will greatly reduce the leakage phenomenon. Of course, it is better to add temperature control, because semiconductors or conductors are generally temperature sensitive. The heating conductivity is generally improved. Most of the mainstream market is now used for semiconductor isolation CCDs, and silicon oxide isolation CCDs are relatively small, apparently because of the higher cost. If you want to understand the effect of a scanner, it is very important to know what quality optoelectronic components are used in the scanner, even if the quality of the semiconductor isolation is different.

Contact photographic devices, which use photographic materials are generally used to make cadmium sulfide cadmium sulfide, the production cost should be much lower than CCD, the same precision CIS scanner on the market is always cheaper than CCD scanner It is for this reason. The scanning distance is short, the scanning resolution is low, and sometimes the nominal value is not reached, and the temperature change is more likely to affect the scanning accuracy. These are the fatal problems of the scanning gun. Friends who are familiar with physics should know that the leakage between the resistance of cadmium sulfide is larger than that of the semiconductor, which also reduces the accuracy.