PROBLEM TO BE SOLVED: To enhance retrieving accuracy by making a microfilm on which a mark for alignment is imprinted pass a frame detection part, detecting film density at a specified position in a film width direction, and detecting and correcting the relative positional deviation in the film width direction between the frame detection part and the film. ;SOLUTION: The microfilm for alignment on which the mark for alignment is imprinted is made to pass the frame detection part 98, and the film density is detected by optical fibers 104 and 106 at the specified positions in the film width direction. By using the obtained detected result, the relative positional deviation in the film width direction between the film for alignment and the frame detection part 98 is detected and corrected. Namely, the output level of a photosensor 108 at the time of making the film for alignment travel is inputted in a positional deviation detection part 300. The detection part 300 detects the relative positional deviation between the frame detection part 98 and the film for alignment by using output from the photosensor 108 corresponding to the film for alignment to be used.;COPYRIGHT: (C)1999,JPO
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