把表面讀成資料
核心畫面最直接的一支：光掃過看得見的表面，把上面印著的東西讀進電腦。
noun · B1
A machine that moves a light across a printed page or a photo and turns what it sees into a computer file, so you can save it, send it, or print it again.
掃描器
核心畫面
Picture a narrow line of light travelling steadily across something, from one edge to the other, missing nothing. It is not looking at the whole thing at once; it is going over it in strips and reading as it goes. Whatever it passes over gets turned into information a computer can hold. Every meaning of scanner is a machine doing that, and what changes between them is only what is being swept: a page, a body, a small printed code, or a long row of radio frequencies.
可以想成一道細細的光，穩穩地從一端走到另一端，把整片東西掃過去，一格都不漏。它不是一眼看完，而是一條一條讀過去。掃過…更多收起
可以想成一道細細的光，穩穩地從一端走到另一端，把整片東西掃過去，一格都不漏。它不是一眼看完，而是一條一條讀過去。掃過的東西都變成電腦能存起來的資料。scanner 的每一個意思都是在做這件事的機器；不同的只是被掃的東西是什麼——一張紙、一個身體、一個小小的條碼，或一整排無線電頻率。From the word’s history
The word is scan plus -er, the ending that names the person or thing that does something, as in print and printer. So a scanner is simply the thing that scans.
這個字是 scan 加上 -er。-er 在英文裡用來指「做這件事的人或東西」，像 print 變成 printer。所以 scanner 就是「負責掃的那一個」。這也說明為什麼從辦公室的機器到醫院的儀器，全都能共用同一個字。
Wiktionary entry for scanner, etymology supplied in packet (kaikki:3f6f69a190036ae4:384154926): From scan + -er.
Three branches
穿過去看見裡面
一樣是一格一格掃過去，只是光束不停在表面，而是穿進去，把裡面的樣子組成一張圖。
noun · B1
A machine that sends a beam through a body or a bag and builds a picture of what is inside it, so people can look without opening anything.
掃描機（醫用、安檢）
掃過一段範圍找訊號
被掃的東西從一片平面換成一條看不見的頻率帶，動作還是一樣：一格一格跑過去，找到有東西就停下來讀。
noun · C1
A radio that moves quickly through a long list of frequencies on its own and stops when it finds one that someone is using, so the listener can follow calls from services such as the fire brigade.
掃頻收音機