| 摘要 |
PURPOSE:To avoid the deterioration of the vertical image resolution and to eliminate the flicker on a character screen, by giving a substantial H/2 delay to the scanning line in an odd field compared with a scanning line in an even field. CONSTITUTION:A video signal S given from the preceding stage is applied to a contact (a) of a switch circuit 3, a character decoder 4 and a synchronous separating circuit 5. The signal S is sampled when the character signal is received at the circuit 4, and a character signal SA is applied to a contact (b) of the circuit 3. The signal S or SA given from the circuit 3 is switched through a switch circuit 8 of a double scanning frequency converting circuit 7, and the output is applied alternately to a 1H memories 10 and 11. At the same time, the signal read in a double speed as high as the writing out of a switch circuit 9 plus the signal delayed by H/2 through an H/2 memory 12 are applied to the contacts (a) and (b) of the circuit 13. Then the circuit 13 is switched by a signal ID given from a control circuit 6 based on the horizontal and vertical synchronous signals HD and VD to discriminate an odd or even scanning field. Then the signals corresponding to each field are applied to a CRT14. |
