Video moire reduction
US6239772A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 17, 1998 |
| Grant date | May 29, 2001 |
| Priority date | — |
| Expiry date | Feb 17, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N3/233
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A display monitor operating under the raster scanning system repeats the line scanning of an electron beam by moving the resulting scanning lines in a direction substantially perpendicular to the line direction. In a cathode ray tube (CRT), the dot pitch of the fluorescent material on the display screen (DS) of the cathode ray tube (CRT) that can emit a fluorescence is determined by the aperture pitch of the shadow mask. Thus, in case of displaying a video pattern (f1h) in which consecutive pixels in a line repeat in an ON and OFF sequence an interference with the aperture pitch of the shadow mask may occur, thereby causing a moire. The moire phenomenon is reduced with a notch filter (NF) which has a passband for baseband video frequencies (f1h) and which has a notch in the amplitude characteristic at a spatial frequency a) at or near to a spatial frequency of dots (fdh or fhh) on the display screen (DS), or b) at or near to a predetermined spatial higher harmonic (f2h, f4h) of the baseband video (f1h) which is near to said spatial frequency of the dots (fdh or fhh).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.