light pen
| Dictionary: light pen |
n.
A small, photosensitive device connected to a computer and moved by hand over an output display in order to manipulate information in the computer.
| Computer Desktop Encyclopedia: light pen |
A light-sensitive stylus wired to a video terminal used to draw pictures or select menu options. The user brings the pen to the desired point on screen and presses the pen button to make contact. Contrary to what it looks like, the pen does not shine light onto the screen; rather, the screen beams into the pen. Screen pixels are constantly being refreshed. When the user presses the button, the pen senses light, and the pixel being illuminated at that instant identifies the screen location.
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| Dental Dictionary: light pen |
n
A pointerlike device available with some computer terminals. A light pen selects data displayed on the screen by being pointed at any desired item.
| Wikipedia: Light pen |
This article is about the computer input device. For the pen-sized flashlight, see penlight.
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. 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. A light pen can work with any CRT-based display, but not with LCD screens (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan[1]), projectors and other display devices.
A light pen is fairly simple to implement. Just like a light gun, a light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun 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, 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, and the BBC Micro. 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 created around 1952 as part of the Whirlwind project at MIT.[2][3]
Since the current version of the game show Jeopardy! 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.
References
- ^ "Slashphone Article". 2006-04-20. http://www.slashphone.com/69/4156.html. Retrieved 2008-11-12.
- ^ "A Critical History of Computer Graphics and Animation". http://design.osu.edu/carlson/history/lesson2.html. Retrieved 2009-05-04.
- ^ "The Computer Desktop Encyclopedia (entry for Light Pen)". http://lookup.computerlanguage.com/host_app/search?cid=C000401&term=light%20pen. Retrieved 2009-05-04.
See also
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Computer Desktop Encyclopedia. THIS COPYRIGHTED DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher. © 1981-2009 Computer Language Company Inc. All rights reserved. Read more |
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| Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Light pen". Read more |
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