Title: Multiple beam CRT for generating a multiple raster display

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Abstract: A low bandwidth high brightness display system that utilizes a multiple beam cathode ray tube to write multiple rasters by concurrently scanning a plurality of lines with a selected number of beams. Each of the rasters covers a different portion of the screen so that the vertical deflection of the beam is reduced for each beam by a factor related to the number of beams. The system reduces the maximum data rate in writing speed relative to conventional arrangements with a resultant bandwidth reduction proportional to the number of beams. The concept is applicable to television viewing screens and field sequential color television to produce simultaneously a high resolution, high brightness and high quality display. FIELD OF THE INVENTION This invention generally relates to display systems and particularly to a high bandwidth television display system that operates with individual channels having a relatively small information bandwidth and with a high brightness by utilizing a multi-beam cathode ray tube to form a plurality of adjacent rasters in a first dimension that concurrently define the total display. DESCRIPTION OF THE PRIOR ART Television type displays have been unable to develop a high resolution, high brightness and high quality display by using conventional scanning methods of either a single beam or even by using a multi-beam cathode ray tube. Multi-beam cathode ray tubes (CRT) are well known in the art and have been used for the generation of both color and black and white television displays. Examples of such multi-beam television displays may be found in the following U.S. Pat. Nos. 3,448,316; 3,596,126; 3,546,516; and 3,594,600, all assigned to a common assignee. For example, in 3,448,316 a lens system is used for eliminating optical errors such as spherical aberration and/or coma from the television display. The optical correction is accomplished by the use of a plurality of electron beams which are made to converge substantially at the optical center of a lens-like electrostatic focusing means which is common to all of the beams and focuses beams on to an electron receiving screen. This particular device generates a color diaplay of the sequential color dot type. Another example of display systems utilizing a multi-beam cathode ray tube may be found in Serial Number 327,896, now U.S. Pat. No. 3,821,796, "Improved Television Display System" which is assigned to the same assignee as this present application. That application discloses a multi-beam cathode ray tube used in conjunction with a field sequential color television system to produce a color display. The electron beams are in line and create a raster by sweeping the plurality of beams across the face of the display in a paintbrush-like fashion. The plurality of electron beams is then used to sweep another series of lines immediately below the previous trace. A transparent rotating color wheel, having the three primary colors -- red, green, and blue, is disposed in front of the display for creating the sense of color in the viewer's eye. The problem with most multi-beam cathode ray tubes is that they must generally be long in length from the viewing screen to the electron gun. The greater length for multi-beam cathode ray tubes is necessitated by the fact that the individual beams must be focused in close proximity to each other and the cathodes must be separated from each other because of the space that each individual cathode requires. Another drawback of most multi-beam CRTs is that generally a high bandwidth is required along with a high deflection rate in the Y-axis. If brightness is to be maintained at a high level a high bandwidth generally results in a poor resolution since brightness is dependent upon a high current beam and higher current results in beam spreading, therefore low resolution. A high current beam further requires higher power, more complex circuitry at greater cost and also reduced reliability. SUMMARY OF THE INVENTION Accordingly, it is the object of the present invention to provide a high resolution, high brightness and high quality raster display. It is another object of the present invention to provide a raster display utilizing a plurality of electron beams having a low bandwidth. It is another object of the present invention to provide a raster display by a cathode ray tube being shorter in length than heretofore possible. It is yet another object of the present invention to provide a multi-beam CRT with a small beam deflection in the Y dimension. It is still another object of the present invention to provide a plurality of electron beams for simultaneously generating a plurality of rasters on a display. In accordance with the foregoing objects a raster display generation system utilizing a multiple beam CRT includes a display surface, a source for generating a plurality of electron beams and control means. A first electron beam traces a first raster encompassing a first vertical position in a first dimension on the display screen. A second electron beam traces a second raster immediately adjacent to the first raster in a first dimension. A third electron beam traces a third raster immediately adjacent to the second raster in the same dimension. A fourth electron beam traces a fourth raster immediately adjacent to the third raster. The plurality of rasters is created simultaneously by the plurality of electron beams. An individual line of a raster is generated by moving a beam across the face of the screen; the beam is then deflected downward in a second dimension to trace the next line in that raster. Each beam is controled to define an individual raster and the plurality of rasters are generated at the same time, on a line by line basis, by the individual beams.


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