METHOD AND DEVICE FOR DETERMINING VARIATIONS IN THE PREVIOUSLY ADJUSTED NOMINAL DISTANCE BETWEEN THE FACING SURFACES OF A COLOUR SELECTION ELECTRODE AND A DISPLAY WINDOW NEAR THE CORNERS OF THE DISPLAY WINDOW OF A COLOUR TELEVISION DISPLAY TUBE

摘要

15.6.1979 1 PHN 9304 "Method of determining variations in the previously adjusted nominal distance between the facing surfaces of a colour selection electrode and a display window near the corners of the display window of a colour television display tube, and device for carrying out the method" The invention relates to a method of determining variations in the previously adjusted nominal distance between the facing surfaces of a colour selection electrode and a display window of a colour television display tube in places situated near the corners of the display window. In this method the capacitance is measured of a capacitor of which one electrode is formed by the colour selection electrode and the other electrode is formed by a measuring electrode surrounded by a screening electrode, which measuring electrode is provided on the outer surface of the display window. By eccentrically moving the measuring electrode in a direction towards the corner of the display window relative to the screening electrode and by a suitable choice of the outside dimensions of the screening electrode, capacitance variations as a result of glass thickness variations in the display window are negligibly small with respect to the capacitance variations as a result of variations in the previously adjusted nominal distance between the facing surfaces of the colour selection electrode and the display window.