light pen
{{Short description|Computer input device}}
{{About|the computer input device|the pen-sized flashlight|penlight}}
{{Use dmy dates|date=August 2021|cs1-dates=y}}
{{Use list-defined references|date=December 2023}}
File:HypertextEditingSystemConsoleBrownUniv1969.jpg (HES) console in use at Brown University, circa October 1969. The photo shows HES on an IBM 2250 Mod 4 display station, including lightpen and programmed function keyboard, channel coupled to Brown's IBM 360 mainframe.]]
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's cathode-ray tube (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. A light pen can work with any CRT-based display, but its ability to be used with LCDs was unclear (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan).
A light pen detects changes in brightness of nearby screen pixels when scanned by cathode-ray tube electron beam and communicates the timing of this event to the computer. Since a CRT scans the entire screen one pixel at a time, the computer can keep track of the expected time of scanning various locations on screen by the beam and infer the pen's position from the latest time stamps.
History
{{anchor|Lightgun}}The first light pen, at this time still called "light gun", was created around 1951–1955 as part of the Whirlwind I project at MIT, where it was used to select discrete symbols on the screen, and later at the SAGE project, where it was used for tactical real-time-control of a radar-networked airspace.
One of the first more widely deployed uses was in the Situation Display consoles of the AN/FSQ-7 for military airspace surveillance. This is not very surprising, given its relationship with the Whirlwind projects. See Semi-Automatic Ground Environment for more details.
During the 1960s, light pens were common on graphics terminals such as the IBM 2250 and were also available for the IBM 3270 text-only terminal.
The first nonlinear editor, the CMX 600 was controlled by a light pen, where operator clicked symbols superimposed on edited footage.
Light pen usage was expanded in the early 1980s to music workstations such as the Fairlight CMI and personal computers such as the BBC Micro and Holborn 9100. IBM PC-compatible MDA (only early versions), CGA, HGC (including HGC+ and InColor) and some EGA graphics cards also featured a connector compatible with a light pen, as did early Tandy 1000 computers,For example, the Tandy 1000 SX has a DE-9 light pen connector on the rear panel; on the later-introduced Tandy 1000 TX, this light pen interface has been replaced with a serial port using the same connector in the same location. the Thomson MO5 computer family, the Amiga, Atari 8-bit, Commodore 8-bit, some MSX computers and Amstrad PCW home computers. For the MSX computers, Sanyo produced a light pen interface cartridge.
Because the user was required to hold their arm in front of the screen for long periods of time (potentially causing "gorilla arm") or to use a desk that tilts the monitor, the light pen fell out of use as a general-purpose input device.{{citation needed|date=January 2012}} Light pen was also perceived as working well only on displays with low persistence, which tend to flicker.
See also
Notes
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References
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{{cite book |title=Fire-Control and Human-Computer Interaction: Towards a History of the Computer Mouse (1940–1965) |chapter=2. Lightpen and Joystick |author-first=Axel |author-last=Roch |author-link=:d:Q102435890 |others=Mindell, David |publisher=Massachusetts Institute of Technology, Program in Science, Technology, and Society |pages=2–3 [2] |url=http://moon.zkm.de/hp_new/pdf/mouse.pdf |access-date=2021-08-24 |url-status=live |archive-url=https://web.archive.org/web/20210628210444/http://moon.zkm.de/hp_new/pdf/mouse.pdf |archive-date=2021-06-28}} (1+10 pages) (NB. This is based on an earlier German article published in 1996 in Lab. Jahrbuch 1995/1996 für Künste und Apparate (350 pages) by Kunsthochschule für Medien Köln mit dem Verein der Freunde der Kunsthochschule für Medien Köln; {{ill|Buchhandlung Walther König{{!}}Verlag der Buchhandlung Walther König|de|Verlag der Buchhandlung Walther König}} in Cologne, Germany. {{ISBN|3-88375-245-2}}.)
}}
External links
{{commonscat|Light pens}}
{{Basic computer components}}
{{Pens}}
Category:Computing input devices