First, we need to know what resolution is. All kinds of scanning guns are marked with their optical resolution and maximum resolution. The unit of resolution is dpi, which is the abbreviation of English Dot Per Inch, meaning the number of pixels per inch. After understanding the meaning of resolution, let's take a look at how important the following parameters of scanning gun are to us.
Optical resolution refers to the actual amount of information that can be collected by the optical system of the scanning gun, that is, the resolution of the photosensitive element of the scanning gun. For example, a scanner with a maximum scanning range of 2 16mm×297mm (suitable for A4 paper) can scan 8.5 inches (2 16mm), and its photosensitive original contains 5 100 cells, with an optical resolution of 5 100 dots /8.5 inches = Common optical resolutions are 300×600dpi, 600× 1200dpi, 1200×2400dpi or higher.
Color resolution is also called color depth, color mode, color level or color scale. In short, it is an index indicating the fineness of color or the gray resolution of scanning gun, and its unit is bits. The exact meaning of color bits is how many "bits" are used to represent scanned pixels. For example, 1bit can only represent black and white pixels, because the numbers in the computer use binary, and 1bit can only represent two values (2 1=2), namely 0 and 1, representing black and white respectively; Eight bits can represent 256 gray levels (2 8 = 256), representing different gray levels from black to white. 24bit can represent 167772 16 colors (2 24 =16777216). Generally, colors above 24bit are called true colors. Of course, there are also 30-bit, 36-bit and 42-bit models. Theoretically speaking, the more color digits, the more realistic the color is.
Let's talk about the relationship between resolution and file size. General scanning application software can automatically calculate the file size when you preview the manuscript, but understanding the calculation method of file size is more helpful for you to make an appropriate choice when managing scanned files and determining scan resolution. The calculation formula of black and white image file is: horizontal dimension× vertical dimension× (scan resolution) 2÷8. The calculation formula of color image file is: horizontal size× vertical size× (scan resolution) 2× color depth×1/8. For example, scanning an ordinary color photo (3.5×5 inches) with 24-bit color RGB, and the scan resolution is 300dpi, the image file length obtained is 5× 3.5× 300 2× 24×1/8 = 4.725 million bytes, that is, 4.7MB.
The last concept that needs to be elaborated is OCR. Is the abbreviation of English optical character recognition. Its function is to read the image information of characters on printed matter through optical input devices such as scanning gun, and analyze the morphological characteristics of characters by pattern recognition algorithm to distinguish different Chinese characters. Chinese OCR is generally only suitable for identifying printed Chinese characters. Using scanning gun and OCR can partly replace the function of keyboard to input Chinese characters, which is a labor-saving and fast method of text input. Common OCR are Tsinghua Wentong, Shangshu and Meng Tian. To supplement the specific application of OCR recognition of scanning gun, the representative product is Honeywell 1900, which is different from flat scanner in that it can recognize printing fonts (unfortunately, it only supports English and Arabic numerals, not Chinese), and the common printing font is OCR-A; OCR-B； OCR-C three fonts. Personally, I prefer OCR-B, which is closer to the common English printed fonts. The digital serial number on a bank check is an example in real life. The number of 1900 can be read directly by setting, and some packages in foreign logistics industry can be printed with receiving labels on the spot. Eye recognition and scanning gun recognition can use the same character string, which greatly improves the operability; Convenient and quick.