Method and apparatus for capacitively measuring variations in the nominal distance between a color selection electrode and a display window of a television display tube
US4307337A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 5, 1979 |
| Grant date | Dec 22, 1981 |
| Priority date | — |
| Expiry date | Nov 5, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J9/42
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The invention relates to a method of determining variations in the previously adjusted nominal distance between the facing surfaces of a color selection electrode and a display window of a color television display tube in places situated near the corners of the display window. In this method the capacitance variations in that distance are determined by measuring a capacitor one electrode of which is formed by the color selection electrode and the other electrode is formed by a measuring electrode surrounded by a screening electrode, the measuring electrode being 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 made negligibly small with respect to the capacitance variations due to variations in the previously adjusted nominal distance between the facing surfaces of the color selection electrode and the display window.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.