Learn in the textbookInput Devices for Capturing Text and Images
DefinitionAn image scanner (イメージスキャナー) is an input device that shines light on an original such as a sheet of paper, reads it, and brings the page into the computer as image data.
ExplanationWhat comes in is an image made of dots, so the words in it cannot be rewritten as text as they stand. OCR (optical character recognition) is what recognizes handwritten or printed letter shapes and replaces them with text in character codes. How finely the scanner reads is stated in dpi (how many dots one inch is split into), and a larger value means a finer reading.
AnalogyA photocopier prints a copy of the original on paper, while a scanner makes the same copy as an image file inside the PC. That copy is just a picture, so fixing the words in it takes a separate step of transcribing them.
Memory hookTo scan means to run your eyes over something line by line, just as a strip of light runs down the original.