Equipment to correct aberrations of a cathode ray beam
US4354143A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 8, 1980 |
| Grant date | Oct 12, 1982 |
| Priority date | — |
| Expiry date | Dec 8, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/28
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Aberrations of an electron beam are corrected as the beam is scanned across the screen of a cathode ray tube by deriving correction signals from stored digital values by means of the calculus of finite differences. The digital values, which are the initial differences of polynomial correction functions, are held in store 10 and summed in adder 20, the results being converted by digital-to-analog converter 50 to analog signals and supplied to the cathode ray tube. Provision is made for the reduction of error in the calculations by shifting higher order differences relative to lower order differences before addition. The circuitry may be implemented on a single chip. Preferably, the invention is applied to the correction of misconvergence in a shadow mask tube.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.