Wikipedia

Light pen

This article is about the computer input device. For the pen-sized flashlight, seepenlight.

Alight penis acomputerinput devicein the form of a light-sensitive wand used in conjunction with a computer'scathode-ray tube(CRT) display.

Photo of theHypertext Editing System(HES) console in use atBrown 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'sIBM 360mainframe.

It allows the user to point to displayed objects or draw on the screen in a similar way to atouchscreenbut with greater positional accuracy. A light pen can work with any CRT-based display, but its ability to be used withLCDswas unclear (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan[1]).

A light pen detects changes in brightness of nearby screen pixels when scanned bycathode-ray tubeelectron 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

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The first light pen, at this time still called "light gun", was created around 1951–1955 as part of theWhirlwind Iproject atMIT,where it was used to select discrete symbols on the screen,[2][3][4][5]and later at theSAGEproject, where it was used for tactical real-time-control of a radar-networked airspace.[3]

One of the first more widely deployed uses was in the Situation Display consoles of theAN/FSQ-7for military airspace surveillance. This is not very surprising, given its relationship with the Whirlwind projects. SeeSemi-Automatic Ground Environmentfor more details.

During the 1960s, light pens were common on graphics terminals such as theIBM 2250and were also available for theIBM 3270text-only terminal.

The first nonlinear editor, theCMX 600was 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 theFairlight CMIand personal computers such as theBBC MicroandHolborn 9100.IBM PC-compatibleMDA(only early versions),[6]CGA,[6]HGC[7](includingHGC+[8]andInColor[9]) and someEGAgraphics cards also featured a connector compatible with a light pen, as did early Tandy 1000 computers,[notes 1]theThomson MO5computer family, theAmiga,[10]Atari 8-bit,Commodore 8-bit,someMSXcomputers[11]andAmstrad PCWhome computers. For the MSX computers,Sanyoproduced a light pen interface cartridge.[12]

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]Light pen was also perceived as working well only on displays with low persistence, which tend toflicker.[13]

See also

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Notes

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  1. ^For example, the Tandy 1000 SX has aDE-9light 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.

References

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  1. ^"Slashphone Article".2006-04-20. Archived fromthe originalon 2008-11-20.Retrieved2008-11-12.
  2. ^Everett, Robert Rivers[in German](1980). "Whirlwind". InMetropolis, Nicholas Constantine;et al. (eds.).A History of Computing in the Twentieth Century.p. 375.
  3. ^abRoch, Axel[at Wikidata]."2. Lightpen and Joystick".Fire-Control and Human-Computer Interaction: Towards a History of the Computer Mouse (1940–1965)(PDF).Mindell, David.Massachusetts Institute of Technology,Program in Science, Technology, and Society. pp. 2–3 [2].Archived(PDF)from the original on 2021-06-28.Retrieved2021-08-24.(1+10 pages) (NB. This is based on an earlier German article published in 1996 inLab. Jahrbuch 1995/1996 für Künste und Apparate(350 pages) byKunsthochschule für Medien Kölnmit demVerein der Freunde der Kunsthochschule für Medien Köln;Verlag der Buchhandlung Walther König[de]in Cologne, Germany.ISBN3-88375-245-2.)
  4. ^"A Critical History of Computer Graphics and Animation".Archived fromthe originalon 2009-05-05.Retrieved2009-05-04.
  5. ^"The Computer Desktop Encyclopedia (entry for Light Pen)".Retrieved2009-05-04.
  6. ^abKosmic, Raymond "Ray", ed. (2023) [2013]."IBM 5150 - Early Versions: Early Cards - Monochrome Display and Printer Adapter (MDA)".minuszerodegrees.net.Archivedfrom the original on 2023-12-04.Retrieved2023-12-04.
  7. ^Elliott, John C. (2020-06-08)."Monochrome Display Adapter: Notes".Seasip.info.Archivedfrom the original on 2023-09-20.Retrieved2016-11-23.
  8. ^Elliott, John C. (2012-08-09)."Hercules Graphics Card Plus: Notes".Seasip.info.Archivedfrom the original on 2016-11-23.Retrieved2016-11-23.
  9. ^Elliott, John C. (2012-08-05)."Hercules InColor Card: Notes".Seasip.info.Archivedfrom the original on 2016-11-23.Retrieved2016-11-23.
  10. ^"2. Amiga joystick extensions".The Linux Kernel documentation.Archivedfrom the original on 2022-12-12.Retrieved2022-12-12.
  11. ^"MSX Wiki (entry for Light Pen)".Retrieved2019-05-16.
  12. ^"Sanyo - MLP-01 | Generation MSX".
  13. ^Norton, Peter(1983). "8. Video Access, part 1: Characters". In Culverwell, David T. (ed.).Inside the IBM PC: access to advanced features and programming.Bowie, Maryland, USA: Brady. p. 164.ISBN0-89303556-4.The light pen isn't one of the more popular options for the IBM/PC. […] The light pen is in a kind of a bind — it can only be used with a display which has a very low persistance. […] But that kind of display screen tends to flicker to the eye. So a good display for the eye can't use a light pen, and a light pen display is harder on the eye. […]
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