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An Overview of Directed Beam Graphics Display Hardware

IP.com Disclosure Number: IPCOM000131260D
Original Publication Date: 1978-Nov-01
Included in the Prior Art Database: 2005-Nov-10
Document File: 10 page(s) / 37K

Publishing Venue

Software Patent Institute

Related People

Anthony P. Lucido: AUTHOR [+3]

Abstract

Directed beam CRT display devices have been available for some time now -- long enough that we can discuss some organizations for practical graphics systems derived from the basic directed beam display design. Currently available interactive computer graphics displays can be placed into three classes. They consist of those employing a direct view storage tube, a directed beam- oriented cathode ray tube, or a raster scan-oriented cathode ray tube. Each class of display has a wide range of applications. This article, of course, deals with the second class -- it will cover the general background and characteristics of this group of displays, including both point plotting and vector drawing directed beam displays. Direct view storage tube devices are discussed in the article by Preiss in this issue.'

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

This record contains textual material that is copyright ©; 1978 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Contact the IEEE Computer Society http://www.computer.org/ (714-821-8380) for copies of the complete work that was the source of this textual material and for all use beyond that as a record from the SPI Database.

An Overview of Directed Beam Graphics Display Hardware

Anthony P. Lucido

Texas A&M University

Directed beam CRT display devices have been available for some time now -- long enough that we can discuss some organizations for practical graphics systems derived from the basic directed beam display design.

Currently available interactive computer graphics displays can be placed into three classes. They consist of those employing a direct view storage tube, a directed beam- oriented cathode ray tube, or a raster scan-oriented cathode ray tube.

Each class of display has a wide range of applications. This article, of course, deals with the second class -- it will cover the general background and characteristics of this group of displays, including both point plotting and vector drawing directed beam displays. Direct view storage tube devices are discussed in the article by Preiss in this issue.'

The directed beam class of displays has changed greatly from the days when oscilloscopes were used as point plotting displays to show the ongoing conditions of laboratory experiments. The display screen has become larger, the display itself more complex, and vectors (lines) may be drawn upon command, rather than by having the user calculate the set of points needed to display a vector connecting two endpoints.

Also provided today are facilities to transform data before it is displayed, hardware to generate curves in addition to straight lines, and a computing facility local to the display to manage its requirements and provide image refreshing.

Cathode ray tube structure

A cathode ray tubed is designed to produce, accelerate, and focus a stream of electrons, deflect the beam as required, and provide a target toward which the beam is directed. A general layout is shown in Figure 1 (see also Figures 2 and 3).

The CRT consists of seven general structures. The heater, with an applied voltage, heats the cathode and causes a "cloud" of electrons to be emitted. The

control grid determines the number of electrons allowed to escape. Since the control grid is at a negative voltage, it will repel many of the electrons. The applied voltage on the grid controls the brightness of the displayed image. The accelerating plates raise the velocity of the electrons to a sufficient value to cause a visible spot on the phosphor coating when it is bombarded by the electron stream. The focusing structures create a fine beam from the incoming stream of electrons. The displayed spot may be controlled so that it ranges from a very fuzzy, broad one, to a...