With the improvement of the user level, it is no longer satisfied with simple computer host equipment, and the demand for various computer peripherals is increasing, including printers, scanners, stylus pens, etc. Among them, as a product with a certain technical content, the scanner is constantly developing in the market, and the technology is constantly improving.
What is the use of the scanner in daily study and work? Let me ask a simple question: Now that the media is rich and colorful, we often see good-looking posters, posters, and graphic materials. They are very good and I want to collect them. But first, what if they are borrowed? "Black" off? NO! If you are not a gentleman, then use a scanner to scan and save it in your computer, you can use it anytime, and it will not fade! There is a document that needs to be stored in the computer, but a comrade ca n’t type or is too slow, why? Scanner + Scanning Recognition (OCR) software, easy to get! When someone else "chicken pecks rice" can be fine COFFEE. Seeing a landscape photo is so beautiful! ! ! If you want to use it as a desktop background, simply use a scanner to get it, you can enjoy it every day.
In short, the scanner can enter printed, written, photo, and other media information into the computer, and then can be processed as desired by the software to suit different applications. From a technical point of view, the scanner is one of the devices that convert traditional analog images into digital images. It converts the analog optical signal of the original manuscript into a set of pixel information, and finally stores it in a digital file in a digital way to realize the digitization of the image.
1. Classification of scanners
(1) According to the interface mode.
At present, the common interface methods of the scanner (that is, the connection between the scanner and the computer) are SCSI, EPP, and USB:
1. SCSI interface. A scanner with a SCSI interface requires a SCSI card to connect the scanner to a computer (the required SCSI card is generally included in the scanner). Most early scanners were SCSI interfaces. The advantage is that the transmission speed is fast and the scanning quality is high; the disadvantage is that a SCSI card needs to be installed in the chassis, an ISA or PCI slot is required, and the corresponding interruption. The installation is relatively complicated and may conflict with other accessories.
2. EPP interface. It is the printing port (parallel port) that we often say. Compared with the SCSI scanner, the speed is slower and the scanning quality is slightly worse, but the installation is convenient and the compatibility is good. Most scanners that use the EPP interface have two interfaces on the rear, one connected to the computer and the other connected to the other parallel port equipment. (Usually a printer).
3. USB interface. It is the latest form of interface. Generally, ATX motherboards have their own USB interface. Older AT motherboards generally do not (some newer AT motherboards have USB ports, but you need to buy a separate cable). The advantage is that the speed is faster than EPP, and it can be plugged and plugged with power, plug and play, and the newer USB scanner can be powered directly from the USB port without the need for additional power. The disadvantage is that the old model can't be used, and the selling price is a little more expensive than EPP.
As can be seen from the above three points, industry and professional users or users with strict requirements on the effect can try to use SCSI and USB scanners, and general office use can choose EPP.
(2) According to the working principle.
From ancient times to the present day, there are handheld, flatbed, film-specific, roller and CIS scanners.
1. Handheld. It is hardly seen now. It was only used for a long time because it was cheap. The optical resolution is generally between 100 DPI and 600 DPI, mostly black and white.
2. Flat type. Also known as CCD scanner, it mainly scans reflection drafts. The optical resolution is 300DPI-2400DPI, and the number of color bits has reached 48 bits.
3. Film scanner. It is mainly used to scan slides, photographic negatives, CT films and professional films, with high precision and strong sense of layering, and the accompanying software is more professional.
4. Drum type. The scanner uses a point light source to sample one pixel at a time, and uses RGB color separation technology. The advantages are of course obvious. The real professional grade and the price are also professional grade.
5. CIS scanner. It is a new type of scanner that came out after 98 years. CIS means "contact image sensor". It does not require an optical imaging system. It has a simple structure, low cost, light weight and practicality. The effect is worse than CCD.
Of course, there are now CCD scanners with TMA (transparent scanner), which can scan film.
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Second, the technical indicators of the scanner
When we touch the scanner, we will see a variety of technical indicators. Below is a brief introduction to common indicators.
1. Scanning accuracy. The resolution we often say is an important parameter to measure the level of a scanner. It reflects the fineness that the scanner can achieve when scanning. The scanning accuracy is usually expressed in DPI (resolution), which is similar to the technical specifications of inkjet printers. The larger the DPI value, the finer the image scanned by the scanner. Scanning resolution is divided into optical resolution (true resolution) and interpolation resolution (maximum resolution). The former is in the form of hardware and the latter is in the form of software.
2. The number of colors. The number of color bits indicates the scanner's ability to recognize colors and the range of colors that can be described. It determines the true degree of color reproduction. The larger the number of color bits, the better and more realistic the scanning effect, and the distortion during the scanning process. Less.
3. Gray level. The gray-scale level of the scanner reflects the ability to provide a range of levels from dark to light when scanning, specifically the ability of the scanner to smoothly transition from pure black to pure white. The larger the number of gray levels, the richer the scan results and the better the results.
4. Scanning format. Refers to the range that the scanner can scan, that is, the size of the paper, generally A4, A4 +, A3, etc.
5. Compatibility. Almost all scanners are available for PCs, and many SCSI and USB scanners are marked as compatible with MAC (Apple).
6. System environment. Drivers are required for the scanner to work, under which systems these drivers can be used, such as WIN98, WIN2000, WINNT, etc. In addition, some SCSI and USB scanners also have FOR MAC (Apple) OS drivers.
7. Optional accessories. Usually refers to the paper feeder (ADF) and the trans-scan adapter (TMA). Not all scanners support additional accessories. As mentioned earlier, some scanners include TMA.
Third, the scanning software
1. Image category. Scanned objects are used for image processing, such as PHOTOSHOP, My Form, My Scanner, and the image program that comes with WINDOWS.
2. OCR category. Scanned objects are used for word processing, and image files are converted into text files, such as Tsinghua Unisplendour OCR, Shangshu OCR, Mentian OCR, Wentong OCR, etc., and TEXTBRIDGE for English recognition.
3. Vectorization software. For professional scanning paper, generally need to cooperate with engineering scanners (A0 or ultra-A0 large format). Almost all scanners are not provided, they need to be purchased separately. The common ones are Tsinghua Unisplendour.
Fourth, the scanning principle
The scanners currently on the market use two completely different manufacturing principles. One is CCD technology, which uses a lens to image the photosensitive element; the other is CIS contact scanning. CIS technology was mainly used in the manufacture of fax machines in the past. Its image will be recorded directly through the CID sensor after being scanned by the LED tube, without the use of lens refraction, so the whole body can be made very thin. It is more suitable for scanning documents or general plane graphics, but not for scanning three-dimensional objects or transmissive manuscripts (Note: transmissive manuscripts are manuscripts through which light can pass, such as negatives, slides, etc.)
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