| 摘要 |
PURPOSE:To improve the quality of a recorded image and to prevent an erroneous retrieval by detecting dust stuck on an information recording medium such as a microfilm, etc., with the signal of a mark detector and removing it. CONSTITUTION:The mark detecting signal of the mark detector 17 is inverted through a digital filter 20 and transmitted to an AND circuit 22. By ANDing between the mark detecting signal and the signal of the mark detecting signal through a delay circuit 21, dust signals are extracted. Then, the number of pulses of the dust signals having a certain length of a film is counted in a counter 25. When the counted value becomes a specified value or more a warning signal is displayed on a warning display part 27 by a CPU 26 and also a cleaning member made of rabbit fur, etc., is actuated so as to remove the dust on the film. Thus, the quality of the recorded image can be improved and the erroneous retrieval can be prevented.
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