| 摘要 |
PURPOSE:To prevent the overlooking of black or white of narrow width by detecting a black or white signal by scanning one line a few times and then by deciding a picture signal in accordance with the existence of a change in signal. CONSTITUTION:During a scan on each line, gate signals G1-G4 and a read signal are supplied to change detecting circuit 20 and the read signal is sequentially supplied to circuit 20 synchronizing with a clock signal of its AND output. Circuit 20 outputs signals ''1'' and ''0'', showing the existence of a change in each scan, and a picture signal of the previous line to all-black detecting circuit 30 and logical-change circuit 40. Circuit 40, when a sampling output is unchanged, supplies the output of circuit 43 to change detecting circuit 50. When the sampling output changes, on the other hand, the output of circuit 50 is NOT-ed by inverter 41 and supplied to circuit 50 again. The signal input to circuit 50 is stored in memory 55, from which it is output via ANd circuit 53 and also input to memory 55 again, where it is stored until a read to circuit 40. |
