Browse Prior Art Database

Terminal Displays Using Light Pens

IP.com Disclosure Number: IPCOM000046902D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Abrahamson, DJ: AUTHOR [+3]

Abstract

In the past, it was required that the light pen field be at least of a certain size so as to eliminate the delay problem which occurs between excitation and illumination of the phosphor. To minimize the delay time, faster responding phosphors have been used, but these are costly. The present arrangement measures the delay time which is then stored in the terminal controller so that it may be subtracted from the reported coordinates each time the light pen tip switch is pressed. This permits the light pen fields to be smaller than in the past and also reduces the requirement for faster responding phosphors. Current terminal displays having light pens compensate for phosphor delay by accepting a predetermined range of reported coordinates beyond the target character position.

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Terminal Displays Using Light Pens

In the past, it was required that the light pen field be at least of a certain size so as to eliminate the delay problem which occurs between excitation and illumination of the phosphor. To minimize the delay time, faster responding phosphors have been used, but these are costly. The present arrangement measures the delay time which is then stored in the terminal controller so that it may be subtracted from the reported coordinates each time the light pen tip switch is pressed. This permits the light pen fields to be smaller than in the past and also reduces the requirement for faster responding phosphors. Current terminal displays having light pens compensate for phosphor delay by accepting a predetermined range of reported coordinates beyond the target character position. Any reported coordinate within the predetermined range will count as a selection of the field. However, in order to avoid selection ambiguity between adjacent fields, the screen formats are restricted so that adjacent fields are not positioned within the predetermined phosphor delay range. This, of course, reduces the number of screen positions which are usable. In the present arrangement, the light pen is calibrated by positioning a target character at a predetermined location as instructed by the display terminal controller. The display terminal operator is then instructed to select the target character with the light pen instrument. The display terminal controller then calculates the pho...