Bar code scanning grab is a kind of commodity bar code scanning, and then transmission, statistics of a convenient office tool. Understand from the bar code scanning gun type: scanning gun and many other types, common in the following categories:

Hand-held scanning gun

The hand-held scanning gun is a product formed by the technology introduced in 1987. Its appearance is very similar to the bar code scanning gun used by supermarket cashiers in their hands. The vast majority of holding scanning guns adopt CIS technology, with an optical resolution of 200dpi, and have black and white, grayscale and color types, of which the color type is generally 18-bit color. There are also individual high-end products using CCD as a photosensitive device, can achieve a bit of true color, scanning effect is better.

small drum type scanning gun

This is an intermediate product of hand-held scanning gun and flat-type scanning gun (new products have emerged in recent years because it is called notebook scanning gun because of its built-in power supply and small size). The vast majority of this product adopts CIS technology, with an optical resolution of 300dpi, and there are two kinds of color and gray scale. The color model is generally 24-bit color. There are also a few small drum type scanning gun using CCD technology, the scanning effect is obviously better than CIS technology products, but due to structural limitations, the volume is generally significantly larger than CIS technology products. The design of the small roller type is to fix the lens of the scanning gun, and the moving object to be scanned is scanned through the lens. When operating like a printer, the object to be scanned must pass through the machine and then be sent out. Therefore, the scanned object cannot be too thick. The biggest advantage of this scanning gun is that it is small in size, but due to various limitations in use, for example, it can only scan thin paper, and the range cannot exceed the size of the scanning gun.

Platform type scanning gun

Also known as flat-panel scanning gun, desktop scanning gun, currently on the market most of the scanning gun belongs to flat-panel scanning gun, is now the mainstream. The optical resolution of this type of scanning gun is between 300dpi and 8000dpi, the number of color bits ranges from 24 to 48, and the scanning width is generally A4 or A3. The advantage of the flat plate is that, like using a copier, as long as the upper cover of the scanning gun is opened, books, newspapers, magazines and photo negatives can be put up for scanning, which is quite convenient, and the scanning effect is the best of all common types of scanning guns. Other large-format scanning guns for large-format scanning, pen-type scanning guns, bar code scanning guns, negative scanning guns (note that the effect is much better than flat-panel scanning guns and transparent scanning, and the price is certainly expensive), physical scanning guns (not flat-panel scanning guns with physical scanning capability, somewhat similar to digital cameras), and many other roller scanning guns mainly used in the field of industrial printing and typesetting.

Scanning gun interface:

There are three types of common interfaces for scanning guns:

(1)SCSI (Small Computer Standard Interface): The maximum number of connected devices for this interface is 8, and the maximum transmission speed is usually 40 M/S, which is faster and generally connects high-speed devices. The installation of SCSI equipment is more complex, in the PC machine to add SCSI card, easy to produce hardware conflict, but 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, there is no limit to the number of connections (as long as you have enough ports), and the installation and use of the device is easy. The disadvantage is that it is slower than SCSI. This interface because of the installation and use of simple and convenient and in the low-end performance requirements are not high occasions to replace the SCSI interface.

(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 scanning gun speed may be extended to 480 M/s. With hot plug function, plug and play. The scanning gun of this interface is gradually popularized with the establishment and promotion of USB standard under the push of Intel.

Scanning gun internal structure and working principle:

Common flat scanning gun is generally composed of light source, optical lens, scanning module, analog-digital conversion circuit and plastic shell. It uses photoelectric elements to convert the detected optical signals into electrical signals, and then converts the electrical signals into digital signals through analog-to-digital converters and transmits them to the computer for processing. When scanning an image, the light source shines on the image and the reflected light passes through the lens to converge on the scanning module, which converts the light signal into an analog digital signal (I. e., voltage, which is related to the intensity of the received light), while indicating the degree of darkness of that image number. At this time, the analog-digital conversion circuit converts the analog voltage into a digital signal and transmits it to the computer. The color is quantized by 8, 10, and 12 bits of the RGB three colors, and the signal is processed into an image output of the above-mentioned 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 in the distinguishable range for us, the scanning gun with a higher number of bits The effect is that the color is smooth and can see more details of the picture.

Resolution of the scanning gun:

The resolution of the scanning gun is determined from three aspects: the optical part, the hardware part and the software part. That is, the resolution of the scanner is equal to the resolution of its optical components plus the resolution of its own processing and analysis through hardware and software.

Optical resolution is the actual number of light points that can be captured by the optical components of the scanning gun per square inch area. It refers to the physical resolution of the scanning gun CCD (or other photoelectric devices) and the real resolution of the scanning gun. Its value is the value obtained by dividing the pixel point that can be captured by the photoelectric element by the maximum scanning size of the scanning gun. Such as the resolution of 1200DPI scanning gun, often its optical part of the resolution of only 400~600DPI. The resolution of the expanded part is generated by a combination of hardware and software, a process that is generated by analyzing the image by a computer and mathematically filling the blank (a process also called interpolation processing).

Optical scanning and output are one-to-one. What is scanned is what is output. After computer hardware and software processing, the output image will become more realistic, the resolution will be higher. At present, most of the scanning guns sold on the market have the function of expanding the software and hardware of the resolution. Some scanning gun advertisements write 9600 × 9600DPI, which is only the maximum resolution obtained by software interpolation, not the real optical resolution of the scanning gun. Therefore, for the scanning gun, its resolution has optical resolution (or optical resolution) and maximum resolution. Of course, what we care about is optical resolution. This is hard work.

We say that the resolution of a scanning gun is as high as 4800DPI (this 4800DPI is the sum of optical resolution and software difference processing), which means that when an image is input with a scanning gun, 4800 × 4800 pixels can be collected on a scanning width of 1 square inch (Pixel). For a 1-inch square scanning area, the image size generated after scanning with a resolution of 4800DPI is 4800 Pixel× 4800Pixel. 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 larger the interpolation component.

scanning gun of photoelectric devices:

At present, there are four main types of photosensitive devices used in scanning guns on the market: photomultiplier tubes, silicon oxide isolated CCD, semiconductor isolated CCD, and contact photosensitive devices (CIS or LIDE).

The mainstream is two kinds of CCD, the principle is simply: in a piece of silicon single crystal on the set of thousands to tens of thousands of phototransistors, these phototransistors are divided into three columns, respectively, with red, green and blue color filter cover, in order to achieve color scanning. Compared with the two kinds of CCD, silicon oxide isolation CCD is better than semiconductor isolation CCD, and friends who are familiar with physics naturally know the reason. Simply put, the leakage phenomenon between semiconductor CCD triodes will affect the scanning accuracy. Isolation with silicon oxide will greatly reduce the leakage phenomenon (this is an insulator). Of course, it is better to add temperature control, because both semiconductors and conductors are generally temperature sensitive, and the conductivity of temperature rise will generally increase (the cost will increase a lot, the price will be much higher, not to mention that everyone knows what will happen). At present, most of the mainstream market is used for semiconductor isolation CCD, and the silicon oxide isolation CCD is relatively small, obviously because of the high cost. If you want to understand the effect of a scanning gun, it is very important to understand what quality photoelectric components the scanning gun uses. Ha ha, even if it is the same semiconductor isolation quality, there are differences.

contact photosensitive device

The photosensitive material it uses is generally cadmium sulfide that we use to make photosensitive resistors, and the production cost should be much lower than CCD (CIS scanning guns with the same precision on the market are always much cheaper than CCD scanning guns for this reason). The scanning distance is short, the scanning definition is low and sometimes even the nominal value is not reached, and the temperature change is easy to affect the scanning accuracy. These are the fatal problems of this scanning gun. Friends who are familiar with physics should know that the leakage phenomenon between resistances of cadmium sulfide is larger than that of semiconductor separation, which also reduces the accuracy.

photomultiplier tube

The photosensitive material is mainly an oxide of metal cesium. His scanning accuracy, even the degree of temperature and noise are the best, but the price is also the most expensive. The average user like me is just dreaming. The price is too high. We will skip its specific technical characteristics here.

The photoelectric device of a scanning gun is an important factor to determine its performance, and other components such as control circuits and software are also important. It may be difficult to access this information directly. We often can only understand the limited content, we in judging the performance of a scanning gun in the end how, only by the actual operation and evaluation software and other methods to understand.