light pen

WordReference Random House Learner's Dictionary of American English © 2025

ˈlight ˌpen, n. [countable]

1. a light-sensitive device used for pointing at characters or objects on a computer screen.

WordReference Random House Unabridged Dictionary of American English © 2025

light′ pen′, [Computers.]

1. Computing a hand-held light-sensitive device used for pointing at characters or objects on a CRT in order to make or modify drawings or to indicate functions to be performed. Also called light′ pen′cil. 

• 1955–60

Collins Concise English Dictionary © HarperCollins Publishers::

light pen noun

1. a rodlike device which, when applied to the screen of a cathode-ray tube, can detect the time of passage of the illuminated spot across that point thus enabling a computer to determine the position on the screen being pointed at
2. a penlike device, used to read bar codes, that emits light and determines the intensity of that light as reflected from a small area of an adjacent surface