Rich life With the intervention of color printers, the families of ordinary people have become more colorful. With the rapid development of computer technology in recent years, some families have more needs
- Barcode scanner types:
There are many types of barcode scanner, the common ones are as follows:
- Handheld Barcode Scanner. The handheld barcode scanner is a product formed by the technology launched in 1987, and its appearance is very similar to the barcode scanner used by the supermarket cashier in the hand. The vast majority of handheld scanners use CIS technology, with an optical resolution of 200dpi, and are available in black and white, grayscale, and color. The color type is generally 18-bit color. There are also some high-end products that use CCD as the photosensitive device, which can achieve true color and better scanning effect.
Second, the small drum scanner. This is an intermediate product between a handheld scanner and a flatbed scanner (there have been new ones in recent years, because it has a built-in power supply and is called a notebook scanner). Most of these products use CIS technology, and the optical resolution is 300dpi, there are two kinds of color and grayscale, the color model is generally 24-bit color. There are also a few small-drum type scanner that use CCD technology, and the scanning effect is obviously better than the products of CIS technology, but due to structural limitations, the volume is generally significantly larger than the products of CIS technology. The design of the small roller type is to fix the lens of the scanning gun, and move the object to be scanned to scan through the lens. When operating, just like a printer, the object to be scanned must pass through the machine and then sent out. Therefore, the object to be scanned cannot be too large. thick. The biggest advantage of this type of scanner is that it is small in size, but due to its limitations in use, for example, it can only scan thin paper, and the range cannot exceed the size of the scanner.
Third, the Portable Desktop Barcode Scanner. Also known as flatbed scanners and desktop scanners, most of the scanners currently on the market are flatbed scanners, which are now the mainstream. The optical resolution of this type of scanning gun is between 300dpi-8000dpi, the color number is from 24 to 48, and the scanning size is generally A4 or A3. The advantage of the flatbed type is that just like using a copier, as long as the upper cover of the scanner is opened, no matter it is books, newspapers, magazines, or photo negatives, it can be placed on it for scanning, which is quite convenient, and the scanning effect is also among all common types of scanners. the best.
Others include large-format scanning guns, pen-type scanning guns, barcode scanning guns, and film scanning guns for large-format scanning (note that it is not a flat-panel scanning gun plus through-scanning, the effect is much better, and the price is of course expensive), physical scanning guns (It is not a flatbed scanner with physical scanning ability, which is somewhat similar to a digital camera), and there are many roller scanning guns mainly used in the field of industrial printing and typesetting.
- Scanner interface:
There are three common types of interfaces for scanners:
(1) SCSI (Small Computer Standard Interface): The maximum number of connected devices for this interface is 8. Usually, the maximum transmission speed is 40M/S, which is faster and generally connects to high-speed devices. The installation of SCSI equipment is more complicated, and an additional SCSI card is generally required to be added to the PC, which is prone to hardware conflicts, but has powerful functions.
(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 is easy. The downside is that it is slower than SCSI. This interface is simple and convenient to install and use, and replaces the SCSI interface in low-end and low-end applications where performance is not high.
(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 transmitting low-speed data. In the future, if there is a USB2.0 standard scanner speed, it may be extended to 480M/s. With hot plug function, plug and play. The scanner gun with this interface has gradually become popular with the establishment and promotion of the USB standard under the push of Intel.
- The internal structure and working principle of the scanner:
A common flat-panel barcode 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 illuminates the image and the reflected light passes through the lens and converges on the scanning module, and the scanning module converts the light signal into an analog digital signal (ie voltage, which is related to the intensity of the received light). related), while indicating how dark the image number is. 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 with 8, 10, and 12 bits of the RGB three colors, that is, the signal is processed into the image output of the above-mentioned number of bits. If there are higher 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 distinguishable range, for us, the higher-digit scanning gun The effect of scanning is that the color connection is smooth, and more picture details can be seen.
- Resolution of the barcode scanner:
The resolution of the 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 scanning gun 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 spots that can be captured per square inch by the optical components of the scanning gun. It refers to the physical resolution of the scanning gun CCD (or other optoelectronic devices), and is also the true resolution of the scanning gun. The value of is the value obtained by dividing the pixels that can be captured by the photoelectric element by the maximum horizontal scan size of the scanning gun. For example, a scanning gun with a resolution of 1200DPI usually only has a resolution of 400-600DPI in the optical part. The resolution of the extended part is generated by the combination of 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).
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. At present, most of the scanning guns on the market have software and hardware expansion functions for resolution. Some scanning gun advertisements say 9600×9600DPI, which is only the maximum resolution obtained by software interpolation, not the true optical resolution of the scanning gun. So for the scanning gun, its resolution has optical resolution (or optical resolution) and maximum resolution. Of course, what we care about is the optical resolution, which is the 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 with the scanning gun, on the scanning width of 1 square inch, 4800× 4800 pixels (Pixel). For a scanning area of 1 inch square, the image size generated after scanning with a resolution of 4800DPI is 4800Pixel×4800Pixel. When scanning images, the higher the scan resolution, the finer the resulting image and the larger the resulting image file, but with more interpolation components.
- The photoelectric device of the scanner:
At present, there are four main types of photosensitive devices used in scanner on the market: photomultiplier tubes, silicon oxide isolation CCDs, semiconductor isolation CCDs, and contact photosensitive devices (CIS or LIDE).
The mainstream is two kinds of CCDs. The principle is simply: thousands to tens of thousands of phototransistors are integrated on a single silicon crystal. These phototransistors are divided into three columns and covered with red, green and blue color filters, so as to achieve Color scan. Compared with 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 CCD transistors of the semiconductor will affect the scanning accuracy. The isolation of silicon oxide will greatly reduce the leakage (this is an insulator). Of course, it is best to add temperature control, because whether it is a semiconductor or a conductor is generally They are all temperature-sensitive, and the electrical conductivity will generally increase when the temperature rises (the cost will increase a lot, and the price, not to mention everyone knows what will happen). At present, most of the mainstream market is used for semiconductor isolation CCD, silicon oxide isolation CCD is relatively small, obviously because of high cost. If you want to understand the effect of a scanning gun, it is very important to know what quality of photoelectric components the scanning gun uses, huh, even if the quality of the semiconductor isolation is different.
Contact photosensitive devices, the photosensitive material used is generally cadmium sulfide, which we use to make photoresistors, and the production cost should be much lower than that of CCDs (CIS scanner with the same accuracy on the market are always much 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 easily affects the scanning accuracy. These are the fatal problems of this kind of scanning gun. Friends who are familiar with physics should know that the leakage between resistors of cadmium sulfide is larger than that of semiconductors, which also reduces the accuracy (hehe, let’s not say it, CIS seems to be very bad, the manufacturer of the barcode scanner will come and hack to death. me).
Photomultiplier tube, the photosensitive material is mainly the oxide of metal cesium. His scanning accuracy, even the degree of temperature influence and noise are the best, but the price is also the most expensive. Ordinary users like me are just dreaming, the price is too expensive, we will ignore its specific technical characteristics here.
The photoelectric device of a scanning gun is an important factor in determining its performance, and other such as control circuit and software are also very important.
