Raster scan image data display controller including means for reducing flickering

Claim 1

A raster scan image data display controller comprising: an image memory for storing image data items at horizontal and vertical display addresses corresponding to horizontal and vertical coordinates in an image display area, for display; read-out means for supplying the horizontal and vertical display addresses to the image memory and reading out the image data item from the image memory; display means for interlaced displaying of the read-out image data item on adjacent paired scanning lines of two types of fields which are to be formed by a raster scan, the interval between said adjacent paired scanning lines being substantially different from a predetermined distance; timing control means for synchronizing the horizontal and vertical display addresses supplied from said read-out means with the raster scan of the display means; and timing switching means for alternatively switching said adjacent paired scanning lines of said two types of fields formed by the raster scan, in association with a timing control of the horizontal and vertical display addresses by the timing control means, so as to select another adjacent paired scanning lines which are situated close to each other, said another adjacent paired scanning lines being formed by one scanning line of said adjacent paired scanning lines and one scanning line of adjacent paired scanning lines which are next to said adjacent paired scanning lines when the interval of said adjacent paired scanning lines of said display is wider than the predetermined distance.