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Non-Linear Checker for Beam Deflection in CRTS

IP.com Disclosure Number: IPCOM000041253D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Pickover, CA: AUTHOR

Abstract

A technique is described whereby as is Moire interference pattern is produced by a cathode ray tube (CRT) electron beam so as to provide a visual indication of non-linearities. The Moire's pattern reveals minute and hidden periodicities, which provide a check of the deflection of the beam.

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Non-Linear Checker for Beam Deflection in CRTS

A technique is described whereby as is Moire interference pattern is produced by a cathode ray tube (CRT) electron beam so as to provide a visual indication of non-linearities. The Moire's pattern reveals minute and hidden periodicities, which provide a check of the deflection of the beam.

As the need for accurate alignment of beams, as used in multi-beam CRTs, increases, the need to detect non-linearities at the screen also increases. Since the yoke of the CRT is used to deflect the electron beam to different parts of the tube face when currents pass through the coils of the yoke, the operation of the yoke must be checked for proper deflection.

In order to use a Moire effect to check, for example, the horizontal deflection of the beam, parallel vertical lines are drawn with equal spacing between each line. The obtained ruling is inclined and superimposed onto the original pattern, and the resulting pattern will reveal hidden periodicities in beam deflection. For the best results, the top of the first inclined line should coincide with a line of the original (or non-inclined) pattern. In general, the higher the density of lines, the more accurate is the resulting pattern.

When implementing this approach to check the horizontal deflection in a graphics display, first vertical lines are drawn and then the same lines are drawn inclined and superimposed. Here, the result, as shown in the figure, reveals a sinusoid period...