First of all, we need to know what resolution is. All kinds of handheld scanners indicate their optical resolution and maximum resolution. The unit of resolution is DPI, DPI is the abbreviation of the English Dot Per Inch, which means the number of pixels per inch. After understanding the meaning of the resolution, let's see how important the parameters of the shandheld scanners to us.
Optical resolution refers to the actual amount of information that can be collected by the optical system of the handheld scanner, which means the resolution of the photosensitive element of the handheld scanner. For example, a handheld scanner with a maximum scanning range of 216mm * 297m (for A4) can scan the maximum width of 8.5 inches (216mm). It contains 5100 original photosensitive element, the optical resolution is 5100 / 8.5 Inch =600dpi. The common optical resolution is 300 x 600dpi, 600 x 1200dpi, 1200 x 2400dpi or higher.
Now Let's talk about the relationship between the resolution and the size of the file. General scanning applications can automatically calculate the size of files when you preview the original sample. But understanding the size of the file is helpful for you to make the right choice when you're managing scanning files and determining scanning resolutions. The Calculation formula of black and white image file is :horizontal dimension *vertical dimension* (scanning resolution) 2 / 8).. The calculation formula of color image file is: horizontal size * vertical size * (scanning resolution) 2 * color depth * 1/8. For example, scanning an ordinary color picture (3.5 x 5 inches) with 24 bit color RGB, scanning resolution is 300dpi, then the length of the image file is 5 x 3.5 x 3002 x 24 x 1/8=4725000Byte, that is 4.7MB.
The last concept that needs to be explained is OCR. It is the abbreviation of Optical character recognition in english. Its function is to read the text and image information on the printed matter by handheld scanner and other optical input devices, and the pattern recognition algorithm is used to analyze the morphological features of characters so as to distinguish different Chinese characters. Chinese OCR is generally only suitable for recognizing printed Chinese characters. The use of handheld scanner and OCR can partly replace the keyboard input of Chinese characters, and it is a labor-saving and fast text input method.