MOIRE INTERFERENCE DETECTOR AND DETECTING METHOD OF RASTER SCANNING CATHODE RAY TUBE DISPLAY

摘要

PROBLEM TO BE SOLVED: To eliminate moire fringes from a displayed image by providing a band-pass filter generating an output signal, and a control means for varying the central frequency of pass band of the filter. SOLUTION: A band-pass filter 360 generates an output signal 395 in response to a signal representative of the pixel frequency of a displayed image in the raster scanning direction within the pass band of filter. An arithmetic function block 350 varies the central frequency of pass band of the filter 360 depending on the active video period of image in the raster scanning direction, the interval in the raster scanning direction of adjacent phosphor elements in the cathode ray tube of a display, and the scanning size in the raster scanning direction. Furthermore, a threshold circuit 370 is connected with the filter 360 and generates a binary signal in response to an output signal from the filter 360. The binary signal facilitates control of moire fringes.