| 摘要 |
PURPOSE:To enable sure and precise detection of a mark length by a detector wherein two sensors are provided with a spacing shorter than the minimum mark length, and detection signals obtained from the sensors during feeding of a film are counted and then processed. CONSTITUTION:Two sensors 11A and 11B are provided with a spacing shorter than the minimum mark length, and outputs SA, SB of waveform shaping circuits 12A, 12B are applied to an AND circuit 13 and an exclusive OR circuit 14. Output of the circuit 14 is applied to an AND circuit 15 together with clock pulses CP. The counted value CV of a counter 17 is divided to 1/2 by a division circuit 18, and the resultant value PB is applied to an addition circuit 19. The result of addition of the value PB and the counted value PA of a counter 16 is applied to a calculation circuit 20. The counted value PA of the counter 16 and a spacing L between the sensors 11A and 11B are also inputted to the calculation circuit 20, so that a length X of a mark 10 is determined through calculation. As a result, it becomes possible to surely determined the length X of the mark 10 with a simple circuit configuration. |
