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A light pen is a

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

input device In computing, an input device is a piece of equipment used to provide data and control signals to an information processing system, such as a computer or information appliance. Examples of input devices include keyboards, mouse, scanners, cameras ...

in the form of a light-sensitive wand used in conjunction with a computer's

cathode-ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictur ...

(CRT) display. It allows the user to point to displayed objects or draw on the screen in a similar way to a

touchscreen A touchscreen or touch screen is the assembly of both an input ('touch panel') and output ('display') device. The touch panel is normally layered on the top of an electronic visual display of an information processing system. The display is often ...

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

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

The first light pen, at this time still called "

light gun A light gun is a pointing device for computers and a control device for arcade and video games, typically shaped to resemble a pistol. Early history The first light guns were produced in the 1930s, following the development of light-sensing ...

", was created around 1945–1955 as part of the

Whirlwind I Whirlwind I was a Cold War-era vacuum tube computer developed by the MIT Servomechanisms Laboratory for the U.S. Navy. Operational in 1951, it was among the first digital electronic computers that operated in real-time for output, and the first t ...

project at

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...

, where it was used to select discrete symbols on the screen, and later at the

SAGE Sage or SAGE may refer to: Plants * ''Salvia officinalis'', common sage, a small evergreen subshrub used as a culinary herb ** Lamiaceae, a family of flowering plants commonly known as the mint or deadnettle or sage family ** ''Salvia'', a large ...

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 The AN/FSQ-7 Combat Direction Central, referred to as the Q7 for short, was a computerized command and control system for Cold War ground-controlled interception used in the USAF Semi-Automatic Ground Environment (SAGE) air defense network. The ...

for military airspace surveillance. This is not very surprising, given its relationship with the Whirlwind projects. See

Semi-Automatic Ground Environment The Semi-Automatic Ground Environment (SAGE) was a system of mainframe computer, large computers and associated computer network, networking equipment that coordinated data from many radar sites and processed it to produce a single unified image ...

for more details. During the 1960s, light pens were common on graphics terminals such as the

IBM 2250 The IBM 2250 Graphics Display Unit was a vector graphics display system by IBM for the System/360; the Model IV attached to the IBM 1130. Overview The IBM 2250 Graphics Display Unit was announced with System/360 in 1964. A complete 2250 III sys ...

and were also available for the

IBM 3270 The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971 and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text ...

text-only terminal. Light pen usage was expanded in the early 1980s to music workstations such as the

Fairlight CMI The Fairlight CMI (short for Computer Musical Instrument) is a digital synthesizer, sampler, and digital audio workstation introduced in 1979 by Fairlight. — with links to some Fairlight history and photos It was based on a commercial lic ...

and personal computers such as the

BBC Micro The British Broadcasting Corporation Microcomputer System, or BBC Micro, is a series of microcomputers and associated peripherals designed and built by Acorn Computers in the 1980s for the BBC Computer Literacy Project. Designed with an emphas ...

IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...

compatible CGA,

HGC HGC can stand for: * Human Genetics Commission *Hercules Graphics Card * H.O.C. Gazellen-Combinatie, a Dutch field hockey club * HGC Global Communications, an internet service provider in Hong Kong * HGC (field hockey) H.O.C. Gazellen-Combinatie, ...

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 conector 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 The Thomson MO5 is a home computer introduced in France in June 1984 to compete against systems such as the ZX Spectrum and Commodore 64. It had a release price of 2390 FF. At the same time, Thomson also released the up-market Thomson TO7/70 ...

computer family, the

Amiga Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...

Atari 8-bit The Atari 8-bit family is a series of 8-bit home computers introduced by Atari, Inc. in 1979 as the Atari 400 and Atari 800. The series was successively upgraded to Atari 1200XL , Atari 600XL, Atari 800XL, Atari 65XE, Atari 130XE, Atari 800XE, ...

, Commodore 8-bit, some MSX computers and

Amstrad PCW The Amstrad PCW series is a range of personal computers produced by British company Amstrad from 1985 to 1998, and also sold under licence in Europe as the "Joyce" by the German electronics company Schneider in the early years of the series' life. ...

home computers. For the MSX computers,

Sanyo , stylized as SANYO, is a Japanese electronics company and formerly a member of the Fortune Global 500, ''Fortune'' Global 500 whose headquarters was located in Moriguchi, Osaka, Moriguchi, Osaka prefecture, Japan. Sanyo had over 230 subsidiari ...

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.

Notes

References

External links

{{Pens Computing input devices History of human–computer interaction Pointing devices

History

See also

Notes

References

External links