| 摘要 |
PURPOSE:To compensate the delay characteristics of an index signal processing circuit and to obtain a picture with fidelity by varying the writing from reading in phases of a memory circuit for an index signal when projecting a color picture of an index system. CONSTITUTION:With the output of a white pulse generating circuit 408 inputting an HD and a VD signal, an index signal generation part provided at the upper part of a picture tube 401 outside of its effective scanning surface is scanned at a starting part of vertical scanning. An index signal obtained by a photoelectric converting element 402 is inputted to a memory circuit 405 and a start trigger pulse generating circuit 407, and on the basis of the 3rd rise or fall counted from the start of the rectangular wave input of the circuit 407, a trigger pulse is generated and written in the memory 405. At the starting part of the following horizontal scan, index signal generation parts provided on the left- and right-hand sides of the picture tube 401 outside of its effective scanning surface are scanned, and the signal is read out from the memory 405 on the basis of the 2nd rise of the input to the circuit 407. Thus, the delay characteristics of the beam index signal processing circuit are compensated. |
