Light pen

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File:HypertextEditingSystemConsoleBrownUniv1969.jpg
Photo of the Hypertext Editing System (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 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

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References

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External links

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  1. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Slashphone_2006
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Everett_1980
  3. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Roch_1996
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Carlson_2009
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named CDE_2009
  6. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Kosmic_2023
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Elliott_2020_MDA
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Elliott_2012_HGCPlus
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Elliott_2012_InColor
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Amiga
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named MSX_2019
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Sanyo
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Norton_1983


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