A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT display.
It allows the user to point to displayed objects or draw on the screen in a similar way to a touchscreen but with greater positional accuracy. It was long thought that a light pen can work with any CRT-based display, but not with LCDs (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan) and other display technologies. However, in 2011 Fairlight Instruments released its Fairlight CMI-30A, which uses a 17" LCD monitor with light pen control.
Since light pens operate by detecting light emitted by the screen phosphors, some nonzero intensity level must be present at the coordinate position to be selected, otherwise the pen won't be triggered.
Famous quotes containing the words light and/or pen:
“We not only grew up on Be-Bop; Be-Bop raised us. For my generation, Be-Bop came on like a light bulb going flash behind the eyes. For us, it was not only an intellectual movement, but a way of life. We walked, dressed, and rapped Be-Bop.”
—Ishmael Reed (b. 1938)
“As I take up my pen I feel myself so full, so equal to my subject, and see my book so clearly before me in embryo, I would almost like to try to say it all in a single word.”
—G.C. (Georg Christoph)