Scanner basics
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Now with the improvement of the user level, it is not satisfied with the simple computer mainframe equipment, and the demand for various computer peripherals is increasing, including printers, scanners, stylus pens, and the like. Among them, the scanner is a product with a certain technical content, the market is constantly developing, and the technology is continuously improving.
What is the use of scanners in everyday learning and work? To ask a simple question: Now the media is rich and colorful, we often see good-looking posters, posters, graphic materials, very good, want to collect, but first, if it is borrowed, what should I do? "Black" off? NO! If you are not a gentleman, then use a scanner to scan it into your computer and save it at any time. It doesn't fade! There is a document that needs to be saved to the computer, but a comrade can't type or be too slow. Why? Easy to use with Scanner + Scanning Specific Identification (OCR) software! When you are "chicken glutinous rice", you can choose COFFEE. See a photo of the scenery, so beautiful! ! ! I want to use it as a desktop background, and I can easily get it with a scanner.
In short, the scanner can input media information such as prints, written documents, photos, etc. into the computer, and then can be processed by the software to suit different applications. From a technical point of view, scanners are one of the devices that convert traditional analog images into digital images. It converts the analog light signal of the original manuscript into a set of pixel information, and finally stores it in a digital file in a digital manner to realize the digitization of the image.
First, the classification of scanners
(1) By interface method.
At present, the common interface mode of the scanner (that is, the connection between the scanner and the computer) has three types: SCSI, EPP, and USB:
1, SCSI interface. The SCSI interface scanner requires a SCSI card to connect the scanner to the computer (the required SCSI card is usually included in the scanner), and most of the earlier scanners were SCSI interfaces. The advantage is that the transmission speed is faster and the scanning quality is high; the disadvantage is that it is necessary to open a chassis to install a SCSI card, occupying an ISA or PCI slot and corresponding interruption, the installation is relatively complicated, and may conflict with other accessories.
2. EPP interface. It is the print port (parallel port) we often say. Compared with SCSI scanners, the speed is slower, the scanning quality is slightly worse, but the installation is convenient and the compatibility is good. Most of the scanners with EPP interface have two interfaces at the back, one is connected to the computer, and the other is connected to other parallel devices. (Generally a printer).
3. USB interface. It is the latest interface form. The general ATX motherboards come with a USB interface. Old-fashioned 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, it can be plugged and unplugged, plug and play, the newer USB scanner can directly take power from the USB port without additional power supply. The disadvantage is that the old model of the machine can not be used, the selling price is a little more expensive than the EPP.
As can be seen from the above three points, industry and professional users or users with strict requirements can choose SCSI and USB scanners as much as possible, and EPP can be selected for general office use.
(2) According to the working principle.
From ancient times to today, there are hand-held, flat-panel, film-specific, drum-type and CIS scanners.
1, handheld. It is almost impossible to see. It was used for a long time because it was cheap. The optical resolution is generally between 100DPI and 600DPI, mostly black and white.
2, flat type. Also known as CCD scanner, mainly sweeping the draft. The optical resolution is 300DPI-2400DPI, and the number of color bits can reach 48 bits.
3, film scanner. It is mainly used to scan slides, photographic negatives, CT films and professional films. It has high precision and strong layering, and the accompanying software is more professional.
4, drum type. The scanner samples the pixels one pixel at a time, using RGB color separation technology, the advantages are obvious, the real professional level, the price is also professional level.
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 optical imaging system. It is simple in structure, low in cost, light and practical, but it requires strict thickness and flatness of scanning. The effect is worse than the CCD.
Of course, there is now a CCD scanner with a TMA (transparator) that scans the film.
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), similar to the technical specifications of inkjet printers. The larger the DPI value, the finer the image scanned by the scanner. The scanning resolution is divided into optical resolution (real resolution) and interpolation resolution (maximum resolution). The former is in hardware form and the latter is in software form.
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 colors, the better and more realistic the scanning effect, and the distortion during scanning. The less.
3, gray level. The grayscale level of the scanner reflects the ability to provide a range of dark to light levels during scanning, specifically the ability of the scanner to smoothly transition from pure black to pure white. The larger the number of gray levels, the more abundant the level of the scan results and the better the effect.
4. Scan the format. It 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 labeled compatible with Mac (Apple).
6, the system environment. Scanner work requires drivers, which systems can be used under these systems, such as WIN98, WIN2000, WINNT, etc., and some SCSI and USB scanners and FOR
MAC (Apple) OS driver.
7, optional accessories. Usually referred to as the paper feeder (ADF) and the sweep adapter (TMA), not all scanners support additional accessories. As mentioned earlier, some scanners have included TMA.
Third, the scanning software
1, image class. Scanned objects are used for image processing, such as PHOTOSHOP, my form, scanning master, and the image program that comes with WINDOWS.
2. OCR class. Scanned objects are used for word processing, and image files are converted into text files, such as Tsinghua Unisplendour OCR, Shangshu OCR, Mengyu OCR, Wentong OCR, etc., as well as TEXTBRIDGE for English recognition.
3. Vectorization software. Professional sweeping drawings, generally need to cooperate with engineering scanners (A0 or super A0 large format) almost all scanners do not bring, you need to buy a single, the common one is Tsinghua Unisplendour.
Fourth, the principle of scanning
The scanners currently on the market use two completely different manufacturing principles. One is CCD technology, which images the lens onto the photosensitive element; the other is CIS contact scanning. CIS technology used to be mainly used in the manufacture of fax machines. Its image is recorded directly through the CID sensor after being swept by the LED tube, eliminating the need for lens refraction, so the entire body can be made very thin. It is more suitable for scanning in documents or general plan texts, and is not suitable for scanning stereoscopic articles or transmissive manuscripts (note: transmissive manuscripts are manuscripts through which light can pass, such as negatives, slides, etc.).