| 摘要 |
PURPOSE:To stop accurately a film at a specific projection position by measuring the size of a blip mark in the forward direction and inverting it, and stopping the inverted run of the film at a quantity equivalent to half the mark size. CONSTITUTION:The coincidence circuit 12 of an inversion control means 7 compares the counted value of a mark counter 10 with the frame number of a retrieval page storage circuit 11, and outputs an inversion command signal to the motor control circuit 13 of a mark size measuring means 19 when the counted value coincides with the frame number and the overall length of the blip mark is detected. Further, a run direction deciding circuit 14 decides on the film run direction on the basis of pulses A and B obtained from pulse encoders and sends the result to the means 19. The means 19 samples forward pulses corresponding to the width of a mark detection signal as mark size by an AND gate 20 for mark size measurement, and a 1/2 frequency divider 22 divides the frequency of the pulses and inputs the resulting pulses to an up/down counter 25 through an AND gate 24. Then the inverted run is stopped once the inverted run of the film through the means 7 at a quantity equivalent to a half the mark size. |
