| 摘要 |
Moire interference detection apparatus (100;110) for a raster-scanned cathode ray tube display comprises a band-pass filter (360;750) for generating an output signal (395;790) in response to a signal indicative of the pixel frequency of a displayed image in a direction of raster scan falling within the pass band of the filter. Control means (350;270) varies the centre frequency of the pass band of the filter in dependence on an active video period of the image in said direction of raster scan, the spacing of adjacent phosphor elements of the cathode ray display tube (210) of the display in said direction of raster scan, and the scan size in said direction of raster scan. <IMAGE> |
