Browse Prior Art Database

Beam-Indexed Monitor With Scanback Deflection System

IP.com Disclosure Number: IPCOM000035018D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 63K

Publishing Venue

IBM

Related People

Christopher, RJ: AUTHOR [+3]

Abstract

Disclosed is a method which combines beam-index color video display with scanback deflection in a color CRT, thereby improving the function and practicality of both techniques. In scanback deflection, the beam is used to display video in both directions, and there is no flyback. As shown in the figure, the horizontal deflection is driven by a linear amplifier. The vertical deflection is driven by a digitally controlled linear amplifier, such that it is changed in steps after each line is displayed. The video signal must be presented to the display in the proper order, which is alternately left to right and right to left, on successive lines. With current video buffers this requires additional circuitry to reverse the video order on alternate lines. Alternatively, video buffers can be built to provide this function.

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Beam-Indexed Monitor With Scanback Deflection System

Disclosed is a method which combines beam-index color video display with scanback deflection in a color CRT, thereby improving the function and practicality of both techniques. In scanback deflection, the beam is used to display video in both directions, and there is no flyback. As shown in the figure, the horizontal deflection is driven by a linear amplifier. The vertical deflection is driven by a digitally controlled linear amplifier, such that it is changed in steps after each line is displayed. The video signal must be presented to the display in the proper order, which is alternately left to right and right to left, on successive lines. With current video buffers this requires additional circuitry to reverse the video order on alternate lines. Alternatively, video buffers can be built to provide this function. Beam index uses one electron gun to display the three primary colors, sequencing through the colors for each pixel by multiplexing the drive to the electron gun. There is no shadow mask. An index stripe (not shown) is provided behind the phosphors for synchronization between the color stripes and the gun's color multiplexer. A phase-locked loop (PLL) synchronizes the deflection, via the index stripes, with the video input. The index frequency can be any rational ratio to the dot clock frequency, and, as shown in the sole figure, it is the dot clock x 3 divided by N, where N might be, for example, 5 or 7. In the preferred embodiment the video clock is constant and the deflection is servo-controlled to synchronize...