Light pen

	Email		Print
	Bookmark		Link

Light pen

A light pen is a computer

Computer

A computer is a machine that manipulates Data according to a list of Code .The first devices that resemble modern computers date to the mid-20th century , although the computer concept and various machines similar to computers existed earlier....
input device

Input device

An input device is any peripheral used to provide data and control signals to an information processing system . Input and output devices make up the hardware interface between a computer as a or 6DOF controller....
in the form of a light-sensitive wand used in conjunction with a computer's CRT

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen....
TV set or monitor

Computer display

A visual display unit, often called simply a monitor or display, is a piece of electrical equipment which displays images generated from the video output of devices such as computers, without producing a permanent record....
. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy.

Discussion

Ask a question about 'Light pen'

Start a new discussion about 'Light pen'

Answer questions from other users

Full Discussion Forum

Encyclopedia

Hypertexteditingsystemconsolebrownuniv1969

A light pen is a computer

Computer

Input device

Cathode ray tube

Computer display

Liquid crystal display

A liquid crystal display is an Electro-optic modulator shaped into a thin, flat panel made up of any number of color or monochrome pixels filled with liquid crystals and arrayed in front of a Light#Light sources or reflector....
screens (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan), projectors and other display devices.

A light pen is fairly simple to implement. The light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun

Electron gun

An electron gun is an electrical component that produces an electron beam that has a precise kinetic energy and is most often used in televisions and Computer display which use cathode ray tube technology, as well as in other instruments, such as electron microscopes and particle accelerators....
refreshes that spot. By noting exactly where the scanning has reached at that moment, the X,Y position of the pen can be resolved. This is usually achieved by the light pen causing an interrupt

Interrupt

In computing, an interrupt is an asynchronous communication signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
, at which point the scan position can be read from a special register, or computed from a counter or timer. The pen position is updated on every refresh of the screen.

The light pen became moderately popular during the early 1980s. It was notable for its use in the Fairlight CMI

Fairlight CMI

The Fairlight CMI was the first polyphonic digital Sampler synthesizer. It was designed in 1979 by the founders of Fairlight, Peter Vogel and Kim Ryrie, and based on a dual microprocessor computer designed by Tony Furse in Sydney, Australia....
, and the BBC Micro

BBC Micro

The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation....
. Even some consumer products were given light pens, in particular Thomson's TO7 and TO7/70 computers. Because the user was required to hold his or her arm in front of the screen for long periods of time, the light pen fell out of use as a general purpose input device.

The first light pen was used around 1957 on the Lincoln TX-0

TX-0

The TX-0, for Transistorized Experimental computer zero but affectionately referred to as tixo , was an early fully transistorized computer and contained a then-huge 64kilo of 18-bit words of core memory....
computer at the MIT Lincoln Laboratory

Lincoln Laboratory

MIT Lincoln Laboratory, also known as Lincoln Lab, is a federally funded research and development center managed by the Massachusetts Institute of Technology and primarily funded by the United States Department of Defense....
, and is mentioned as the "Lincoln Wand" in the first RFC

RFC

RFC, a three-letter initialism, may refer to:...
, RFC 1.

Since the current version of the game show

Game show

A game show is a type of television program in which members of the public or celebrity, sometimes as part of a team, play a game which involves answering questions or solving problems for money and/or prizes....
Jeopardy!
Jeopardy!

Jeopardy! is a game show featuring trivia in topics such as history, literature, pop culture and science. The show has a decades-long Jeopardy! broadcast history in the United States since its creation by Merv Griffin in the early 1960s....
began in 1984, contestants have used a light pen to write down their wagers and responses for the Final Jeopardy! round.

Since light pens operate by detecting light emitted by the screen phosphors, some nonzero intensity level must be present at the coordinate position to be selected.

Light pen

See also