Light pen: Difference between revisions
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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. | 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 [[Liquid-crystal display|LCDs]] was unclear (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan<ref name="Slashphone_2006"/>). | 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{{Dubious|reason=This may have been historically true, but now?|date=August 2025}}. A light pen can work with any CRT-based display, but its ability to be used with [[Liquid-crystal display|LCDs]] was unclear (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan<ref name="Slashphone_2006"/>). | ||
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. | 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. | ||
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<ref name="CDE_2009">{{cite web |title=The Computer Desktop Encyclopedia (entry for Light Pen) |url=http://lookup.computerlanguage.com/host_app/search?cid=C000401&term=light%20pen |access-date=2009-05-04}}</ref> | <ref name="CDE_2009">{{cite web |title=The Computer Desktop Encyclopedia (entry for Light Pen) |url=http://lookup.computerlanguage.com/host_app/search?cid=C000401&term=light%20pen |access-date=2009-05-04}}</ref> | ||
<ref name="Everett_1980">{{cite book |chapter=Whirlwind |author-last=Everett |author-first=Robert Rivers |author-link=:de:Robert Everett (Ingenieur) |date=1980 |title=A History of Computing in the Twentieth Century |editor-last=Metropolis |editor-first=Nicholas Constantine |editor-link=Nicholas Constantine Metropolis |display-editors=etal |edition= |publisher= |isbn= |page=375}}</ref> | <ref name="Everett_1980">{{cite book |chapter=Whirlwind |author-last=Everett |author-first=Robert Rivers |author-link=:de:Robert Everett (Ingenieur) |date=1980 |title=A History of Computing in the Twentieth Century |editor-last=Metropolis |editor-first=Nicholas Constantine |editor-link=Nicholas Constantine Metropolis |display-editors=etal |edition= |publisher= |isbn= |page=375}}</ref> | ||
<ref name="Norton_1983">{{cite book |author-last=Norton |author-first=Peter |author-link=Peter Norton |editor-last1=Culverwell |editor-first1=David T. |title=Inside the IBM PC: access to advanced features and programming |date=1983 |publisher=Brady |location=Bowie, Maryland, USA |isbn=0-89303556-4 |page=164 |chapter=8. Video Access, part 1: Characters |quote=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. […]}}</ref> | <ref name="Norton_1983">{{cite book |author-last=Norton |author-first=Peter |author-link=Peter Norton |editor-last1=Culverwell |editor-first1=David T. |title=Inside the IBM PC: access to advanced features and programming |date=1983 |publisher=Brady |location=Bowie, Maryland, USA |isbn=0-89303556-4 |page=164 |chapter=8. Video Access, part 1: Characters |quote=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 {{sic|?|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. […]}}</ref> | ||
<ref name="Amiga">{{cite web |title=2. Amiga joystick extensions |url=https://www.kernel.org/doc/html/v4.19/input/devices/amijoy.html#amiga-lightpen-pinout |access-date=2022-12-12 |website=The Linux Kernel documentation |url-status=live |archive-url=https://web.archive.org/web/20221212202955/https://www.kernel.org/doc/html/v4.19/input/devices/amijoy.html#amiga-lightpen-pinout |archive-date= 2022-12-12 }}</ref> | <ref name="Amiga">{{cite web |title=2. Amiga joystick extensions |url=https://www.kernel.org/doc/html/v4.19/input/devices/amijoy.html#amiga-lightpen-pinout |access-date=2022-12-12 |website=The Linux Kernel documentation |url-status=live |archive-url=https://web.archive.org/web/20221212202955/https://www.kernel.org/doc/html/v4.19/input/devices/amijoy.html#amiga-lightpen-pinout |archive-date= 2022-12-12 }}</ref> | ||
<ref name="MSX_2019">{{cite web |access-date=2019-05-16 |title=MSX Wiki (entry for Light Pen) |url=https://www.msx.org/wiki/Light_pen}}</ref> | <ref name="MSX_2019">{{cite web |access-date=2019-05-16 |title=MSX Wiki (entry for Light Pen) |url=https://www.msx.org/wiki/Light_pen}}</ref> | ||
Latest revision as of 20:18, 13 November 2025
Template:Short description Script error: No such module "about". Template:Use dmy dates Template:Use list-defined references
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 accuracyScript error: No such module "Unsubst".. 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[1]).
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
Script error: No such module "anchor".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,[2][3][4][5] and later at the SAGE project, 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 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),[6] CGA,[6] HGC[7] (including HGC+[8] and InColor[9]) and some EGA graphics cards also featured a connector compatible with a light pen, as did early Tandy 1000 computers,[notes 1] the Thomson MO5 computer family, the Amiga,[10] Atari 8-bit, Commodore 8-bit, some MSX computers[11] and Amstrad PCW home computers. For the MSX computers, Sanyo produced 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.Script error: No such module "Unsubst". Light pen was also perceived as working well only on displays with low persistence, which tend to flicker.[13]
See also
Notes
References
External links
Template:Basic computer components Template:Pens
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