When we choose and buy scanner, often can see such phenomenon, a lot of technical parameters, such as scan format, optical resolution, color number of the same scanner, the price difference is very big, some even dozens of times. So, what is the difference between a home scanner and a professional scanner?
What is the difference between domestic scanner and professional scanner: lamp tube
Professional scanner, before scanning will automatically detect the light intensity emitted by the lamp tube, especially when the scanner just started, because the lamp tube did not enter a stable state, the scanner has a certain preheating time, only when the light intensity is enough to reach the standard, the light source detection sensor in the machine will issue through the command. And then the scanner can be the best working state for scanning. Ordinary home, office scanner basically without self-inspection procedures, some scanner lamp tube light even naked eye can not feel dazzling, such light intensity is not enough to show the original manuscript in the dark detail.
What distinguishes a home scanner from a professional scanner: a mirror
Mirrors, they play a crucial role in the scanner. We know that when light hits a surface, there will be a diffuse reflection, because it is impossible to create an absolute plane, so when light hits the mirror, more or less there will be some loss, the higher the flatness of the mirror, the less light will be lost. Professional scanners, in order to minimize this interference, do special black jet treatment before and after the lens, and even use the same paint as the material in the camera darkroom. In fact, in recent years, the technology has been applied to ordinary home and commercial scanners.
What distinguishes home scanners from professional scanners: lenses
Perfect image quality depends to a large extent on good lenses, which must solve a series of problems related to light control: image quality, the area covered, consistency over a wide range of shooting distances, large aperture, etc. Glass used in manufacturing lenses must have good physical properties, from the perspective of lens manufacturing technology, in order to improve the transmittance of light, the use of coating technology, and the test lens coating technology is good or bad, you can use the method of direct vision, the weaker the better lens reflection. At the same time, in order to improve the imaging effect of the lens, aspheric lens technology and low dispersion technology have been adopted, and the current lens, it is necessary to use multiple combinations, such as the lens of MicrotekScanMaker6400, which consists of 4-5 lenses, and the aspheric lens.
What are the differences between domestic and professional scanners: CCD
CCD is the core component of the scanner, CCD is called photoelectric coupling device, it can output different strong and weak current according to the intensity of the light, complete the photoelectric conversion process. The scanner is generally linear CCD, linear CCD line is generally composed of 3000 to 10000 optical detection points, a total of R, G, B three lines. The more optical detection points in a certain unit of length, the higher the optical resolution of the scanner, many professional scanners have used 8000 professional CCD. Compared with the CCD of ordinary scanner, the CCD of professional scanner mostly USES the silicon dioxide material with high insulation, thus ensuring the consistency of signal transmission. Due to the limitation of cost, the p-n junction CCD with general insulation is generally used in the ordinary scanner. When the CCD is used for photoelectric conversion, the error of output data is relatively large. It can be said that the price of CCD has a direct impact on the price of the scanner, at present, professional CCD worldwide only one manufacturer kodak production, and in recent years the production of ordinary CCD manufacturers are very many, which is also the current common household, commercial scanner market prices fall again and again important reasons.
In addition, the size of professional CCDS is larger, which can further improve the consistency and sensitivity of each photosensitive point, as well as the SNR of color. The so-called signal-to-noise ratio is simply the percentage of useful and useless signals. In the process of converting light intensity signal to analog electrical signal, CCD has been relatively mature for the conversion of 8bit and 10bit, but in the conversion of 12bit and 16bit, it is required that the CCD must have a signal to noise ratio (S/N) above 12bit and 16bit. A 48bit scanner requires a CCD with a signal-to-noise ratio of more than 16 bits, which is currently very expensive. In addition, the signal-to-noise ratio will decrease with the increase of temperature, with an average decrease of one bit for each l0℃ increase in temperature. Some professional scanners, such as MICROTEK's CCD, have special thermostatic systems to ensure that the temperature at which the CCD operates is constant.
What distinguishes a home scanner from a professional scanner: cables
The signal from the CCD needs to be transmitted to the A/D converter on the main board of the scanner via the cable connecting the CCD to the main board of the scanner for digital-to-analog conversion. Because the signal that CCD sends out is the signal that imitate, be subject to outside interference easily, high-grade scanner is in the design already considered this fully, the shield layer that cable outer wrap has wire to make, the degree that will signal suffers interference is reduced to the minimum. During the scan, we can see through the glass the flat cables inside the scanner. The cables for domestic and commercial scanners are exposed without shielding.
That is the home scanner and professional scanner difference what all the content, these parameters if only literally, it seems to be much higher than professional scanner, but in fact, there is an essential difference between them and professional scanner technical indicators.