Browse Prior Art Database

Dark Screen Light Pen

IP.com Disclosure Number: IPCOM000086784D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Mantey, PE: AUTHOR [+2]

Abstract

Method and apparatus are disclosed for light-pen location and extraneous light reduction in video terminals, e.g., IBM 2250 and 3270.

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This is the abbreviated version, containing approximately 100% of the total text.

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Dark Screen Light Pen

Method and apparatus are disclosed for light-pen location and extraneous light reduction in video terminals, e.g., IBM 2250 and 3270.

One method comprises the steps of detecting the most significant digits of the cartesian coordinates of a light pen positioned upon the viewing surface of the video surface by way of interruption of an external field. The external field is formed from a flat detection field parallel to the video surface such as by a light- beam grid or a resistive-grid membrane. Reference can be made to the IBM Technical Disclosure Bulletin, Vol. 9, No. 5, October 1966, pp. 493-494, which shows a light-beam grid comprising a rectangular matrix of light beams and associated photosensitive devices overlaying a surface and the location of a probe obtained by light path interruption.

An alternate method consists of using coarse light-pen detection in which a small fraction of the total number of spots on the screen are illuminated and the larger, light-pen detect area senses one of them to give an initial coarse approximation of the pen position. The second method step includes generating a repeated raster scan line pattern in a reduced region around the coordinate point defined by the external field interruption or approximate position and obtaining the lesser significant cartesian coordinate digits upon the pen detecting a pattern in the reduced field.

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