Pre-Caching hochdimensionaler Aggregate mit relationaler Technologie.

A scanning line control system shifts the timing at which a vertical synchronizing signal is generated, by h/N, to insert (N-1) scanning lines, in appearance, during one line-to-line interval for producing accurate hard copies of images displayed on a video monitor. The scanning line control system generates a signal of a frequency Nfh in synchronism with a horizontal synchronizing signal where (N-1) is the maximum number of scanning lines inserted during one line-to-line interval and fh is the frequency of the horizontal synchronizing signal. The signal of the frequency Nfh is decoded by a logic circuit in which there is preset a value corresponding to the vertical synchronizing signal as it is frequency-divided by N. The logic circuit is decoded by a train of N pulses produced by dividing the frequency Nfh synchronous with the horizontal synchronizing signal. A vertical deflection circuit is triggered by an output from the logic circuit. The vertical synchronizing signal is therefore shifted in periods of h/N with the result that a maximum of (N-1) scanning lines can be inserted, in appearance, during one line-to-line interval. A hard copy produced by photographing an image formed at a reduced line-to-line interval has a uniform contrast.